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1
Arkin, H., M. M. Chen e K. R. Holmes. "Adaptive Thermal Modeling: A Concept for Measurement of Local Blood Perfusion in Heated Tissues". Journal of Biomechanical Engineering 108, n. 4 (1 novembre 1986): 306–11. http://dx.doi.org/10.1115/1.3138619.
Testo completoAbstract (sommario):
A new Adaptive Thermal Modeling (ATM) method for the measurement of local tissue blood perfusion rate is introduced. The method is based on a two-phase numerical technique. The first phase includes a fast, finite difference scheme for solution of the transient temperature field. The second phase involves iterative corrections of the perfusion until the modeled temperatures coincide with those measured by the temperature sensors. The results obtained from computer generated “data”, as well as from laboratory experiments demonstrate the potential capability of the ATM method to continuously measure local perfusion rates in heated tissues. Rigorous analysis of the technique is planned for the near future so that it can be applied to in vivo measurements of local tissue blood perfusions.
2
ZHANG, ZE-WEI, HUI WANG e QING-HUA QIN. "METHOD OF FUNDAMENTAL SOLUTIONS FOR NONLINEAR SKIN BIOHEAT MODEL". Journal of Mechanics in Medicine and Biology 14, n. 04 (3 luglio 2014): 1450060. http://dx.doi.org/10.1142/s0219519414500602.
Testo completoAbstract (sommario):
In this paper, the method of fundamental solution (MFS) coupling with the dual reciprocity method (DRM) is developed to solve nonlinear steady state bioheat transfer problems. A two-dimensional nonlinear skin model with temperature-dependent blood perfusion rate is studied. Firstly, the original bioheat transfer governing equation with nonlinear term induced by temperature-dependent blood perfusion rate is linearized with the Taylor's expansion technique. Then, the linearized governing equation with specified boundary conditions is solved using a meshless approach, in which the DRM and the MFS are employed to obtain particular and homogeneous solutions, respectively. Several numerical examples involving linear, quadratic and exponential relations between temperature and blood perfusion rate are tested to verify the efficiency and accuracy of the proposed meshless model in solving nonlinear steady state bioheat transfer problems, and also the sensitivity of coefficients in the expression of temperature-dependent blood perfusion rate is analyzed for investigating the influence of blood perfusion rate to temperature distribution in skin tissues.
3
Usui, A., T. Hotta, M. Hiroura, M. Murase, M. Maeda, T. Koyama, M. Tanaka, E. Takeuchi e T. Abe. "Cerebral Metabolism and Function during Normothermic Retrograde Cerebral Perfusion". Cardiovascular Surgery 1, n. 2 (aprile 1993): 107–12. http://dx.doi.org/10.1177/096721099300100204.
Testo completoAbstract (sommario):
Retrograde cerebral perfusion through a superior vena cava (SVC) cannula is a new technique used to protect the brain during circulatory arrest. Cerebral blood flow, oxygen consumption, blood sugar consumption and auditory brain stem responses were measured at various rates (100, 200 and 300 ml min−1) of retrograde cerebral perfusion in normothermic mongrel dogs ( n = 12, body-weight 13–15 kg). During perfusion about 20% of the perfusate from the SVC was returned via the aorta, while the rest drained into the inferior vena cava. External jugular venous pressure increased as the perfusion rate increased (mean(s.d.) 26.0(6.4) mmHg at a rate of perfusion of 300 ml min−1). Oxygen and blood sugar consumption also increased as the rate of perfusion increased. Retrograde cerebral perfusion at 300 ml min−1 provided half of the cerebral blood flow (mean(s.d.) 14.7(6.4) versus 34.3(7.8)ml min−1) of antegrade cardiopulmonary bypass (CPB). Analysis of the blood returned through the aorta during perfusion at a rate of 300 ml min−1 showed that mean(s.d.) oxygen consumption was about one-third (4.4(2.1) versus 12.3(7.1) ml min−1) and blood sugar consumption about 15% (17(22) versus 114(54) mg min−1) of that seen in blood returned through the SVC during CPB. Auditory brain stem responses disappeared immediately when perfusion was started but recovered completely as soon as CPB was resumed. Although the oxygen provided by perfusion was not sufficient to maintain cerebral function, it should help protect the brain during circulatory arrest.
4
Lama Moktan, Sushila, e Manan Karki. "Comparison of non-invasive haemodynamic monitors of stress response to endo-tracheal intubation with perfusion index in patients undergoing elective surgery". Journal of Society of Surgeons of Nepal 23, n. 2 (31 dicembre 2020): 9–13. http://dx.doi.org/10.3126/jssn.v23i2.35797.
Testo completoAbstract (sommario):
Introduction: Laryngoscopy and intubation is always associated with a short term reflex sympathetic pressor response. The perfusion index is an indirect, non-invasive, and continuous measure of peripheral perfusion by pulse oximeter which can detect the stress response to intubation similar to heart rate, systolic blood pressure and diastolic blood pressure.
Methods: This prospective observational study enrolled sixty-five normotensive patients of American society of anesthesiologists physical status grade I and II scheduled for elective surgery under general anaesthesia. Tracheal intubation was performed after induction with intravenous fentanyl, propofol and vecuronium. Heart rate, Systolic and Diastolic Blood Pressure and Perfusion Index were measured before induction of anesthesia, before intubation and one minute, three minutes, five minutes after the insertion of the endotracheal tube. Increase in heart rate by ?10 beats per minute, systolic and diastolic blood pressure by ?15 millimeters of mercury and decrease in Perfusion index ?10% after endotracheal intubation as compared to preintubationvalue were considered positive haemodynamic changes.
Results: Endotracheal intubation produced a significant increase in heart rate and blood pressure whereas perfusion index decreased significantly. Our study showed that perfusion index response criterion achieved 97.7% (Confidence interval 97.58-97.86) sensitivity in detecting the stress response to insertion of endotracheal tube whereas systolic and diastolic blood pressure achieved sensitivity of 90% and 92% respectively.
Conclusion: Perfusion Index is easier, reliable and non-invasive alternative to conventional haemodynamic criteria for detection of stress response to endotracheal intubation.
5
pennati, giancarlo, francesco migliavacca, francesca gervaso e gabriele dubini. "assessment by computational and in vitro studies of the blood flow rate through modified blalock-taussig shunts". Cardiology in the Young 14, S3 (ottobre 2004): 24–29. http://dx.doi.org/10.1017/s1047951104006511.
Testo completoAbstract (sommario):
surgical repairs of many severe congenital cardiac malformations, such as the procedures used to redirect the flow of blood in the setting of absent or suboptimal perfusions, are performed either using direct vascular anastomosis, or by the insertion of interpositioned prosthetic shunts. examples of these applications can be found when considering those cardiac malformations characterized by the common physiological feature of having a single pumping ventricle, usually due to the incomplete and rudimentary form of the complementary ventricle. in this situation, since the circulation depends on the functionally single ventricle, pulmonary perfusion can be derived from the systemic circulation through a synthetic tube (gore-tex®, falstaff, az, usa), usually connected between the brachiocephalic or subclavian arteries and the right or left pulmonary arteries. this arrangement is called the modified blalock-taussig shunt (fig. 1, left). the effect is to produce parallel circulations (fig. 1, right). survival at this stage is closely dependent on the balance between systemic and pulmonary flows, and thus on the fluid-dynamics through the interposition shunt, which is often the sole source of pulmonary perfusion.
6
MacLean, David A., Lisa M. Vickery e Lawrence I. Sinoway. "Elevated interstitial adenosine concentrations do not activate the muscle reflex". American Journal of Physiology-Heart and Circulatory Physiology 280, n. 2 (1 febbraio 2001): H546—H553. http://dx.doi.org/10.1152/ajpheart.2001.280.2.h546.
Testo completoAbstract (sommario):
The purpose of the present study was to examine the effects of adenosine perfusion of the isolated triceps surae muscle group in the decerebrate cat on interstitial adenosine concentrations as well as heart rate and blood pressure responses. In six male cats (6.0 ± 0.21 kg), the triceps surae muscle group of both legs was perfused with an artificial blood solution containing no additives (control) and then with blood containing 20 mM or 100 μM adenosine for 10 min. An intact muscle reflex was confirmed by bolus injections of 50 mM phosphate and/or saturated KCl administered into the triceps surae muscle via the cannulated popliteal artery before and after adenosine blood perfusion. Microdialysis of the triceps surae muscle group during muscle perfusion revealed that interstitial adenosine was elevated ( P < 0.05) from 0.9 ± 0.3 μM during control blood perfusion to 2,421 ± 547 μM during 20 mM adenosine perfusion. In addition, interstitial adenosine levels were increased ( P < 0.05) from 1.1 ± 0.3 μM during control blood perfusion to 4.1 ± 1.2 μM during perfusion with 100 μM adenosine. Despite the large increases in interstitial adenosine levels, perfusion of the triceps surae muscle group with the two blood adenosine solutions resulted in no significant increases in heart rate or blood pressure. These data strongly suggest that elevated interstitial adenosine concentrations do not play a role in activating the muscle reflex and confirm our previous in vivo human findings ( J Appl Physiol 83: 1045–1053, 1997).
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Murakami, Hideyasu, Hitomi Takanaga, Hirotami Matsuo, Hisakazu Ohtani e Yasufumi Sawada. "Comparison of blood-brain barrier permeability in mice and rats using in situ brain perfusion technique". American Journal of Physiology-Heart and Circulatory Physiology 279, n. 3 (1 settembre 2000): H1022—H1028. http://dx.doi.org/10.1152/ajpheart.2000.279.3.h1022.
Testo completoAbstract (sommario):
Here we present a method for measuring the permeability coefficient-surface area product ( PS) values at the blood-brain barrier in mice, using the in situ brain perfusion technique originally developed for rats by Takasato et al. ( Am J Physiol Heart Circ Physiol 247: H484–H493, 1984). Retrograde infusion into the right external carotid artery increased the carotid perfusion pressure in proportion to the perfusion rate. Intravascular volume and cerebral perfusion fluid flow at a perfusion rate of 1.0 ml/min in mice were similar to those in rats. In addition, the contribution of systemic blood to total flow in the hemisphere was small (only 3.2%). These findings indicated that this perfusion rate is suitable for mice. The PS values of more than 20 different compounds were determined in mice by using the in situ brain perfusion technique, and comparisons were made with data from rats. There was a close relationship (1:1) between the PS values in mice and rats, indicating that brain capillary permeabilities are similar in mice and rats.
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Ajcharanukul, O., E. Chunhacheevachaloke, P. Vorachart e W. Chidchuangchai. "The Postural Autonomic Regulation of Pulpal Blood Flow". Journal of Dental Research 92, n. 2 (19 novembre 2012): 156–60. http://dx.doi.org/10.1177/0022034512469025.
Testo completoAbstract (sommario):
Evidence suggests that postural changes in systemic blood pressure may significantly affect blood flow in the dental pulp. This in vivo study examined the responses of pulpal perfusion, systemic blood pressure, and heart rate to postural changes in humans. The experiments were done on 21 premolars in 16 participants aged 20-31 yrs. Pulpal blood flow recordings were measured by means of a laser Doppler Flowmeter. A blood pressure monitor was used to record blood pressure and heart rate. All measurements were simultaneously recorded for 1 min, 5 min after participants made postural changes. Changing from supine to standing caused a significant reduction in pulpal perfusion, while heart rate and diastolic blood pressure increased significantly. A significant non-linear relationship was found between percentage changes in pulpal perfusion and heart rate resulting from standing up. We speculate that when patients arise from the supine position, the shift in venous blood to the legs transiently (2-10 sec) lowers venous return and cardiac output, causing less inhibition of the vasomotor center, which, in turn, results in increased heart rate and blood pressure, but a decrease in pulpal blood flow. These results suggest that pulpal blood flow is affected by postural change, presumably via the autonomic nervous system.
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Ohlsson, J., M. Middaugh e M. P. Hlastala. "Reduction of lung perfusion increases VA/Q heterogeneity". Journal of Applied Physiology 66, n. 5 (1 maggio 1989): 2423–30. http://dx.doi.org/10.1152/jappl.1989.66.5.2423.
Testo completoAbstract (sommario):
This study addresses the hypothesis that decreases in lung perfusion rate independently worsen gas exchange efficiency in an isolated left lower lobe in zone 2 conditions. In seven anesthetized dogs, the left lower lobe was isolated, leaving the bronchus and bronchial vasculature intact. Blood was taken from the femoral arteries and reinfused at a controlled rate into the pulmonary artery of the left lower lobe. The flow rate was varied between 100 and 400 ml/min. The multiple inert gas elimination technique was used to quantitate the matching of ventilation to perfusion. Reduction in lobe blood flow resulted in a significant increase in perfusion-related indexes of alveolar ventilation-perfusion heterogeneity, such as the log standard deviation of the perfusion distribution, the retention component of the arterial-alveolar difference area, and the retention dispersion index. The increased heterogeneity suggests a worsening of the intraregional matching between the ventilation and the perfusion when perfusion is less than normal.
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Badimon, L., JJ Badimon, VT Turitto e V. Fuster. "Role of von Willebrand factor in mediating platelet-vessel wall interaction at low shear rate; the importance of perfusion conditions". Blood 73, n. 4 (1 marzo 1989): 961–67. http://dx.doi.org/10.1182/blood.v73.4.961.961.
Testo completoAbstract (sommario):
Abstract We have previously observed that von Willebrand factor (vWF) plays an important role in platelet deposition on subendothelium at low values of wall shear rate (200 to 400 seconds-1). In the present study, we have investigated the mechanism responsible for such a defect in platelet deposition at low shear rates in the absence of vWF. Blood from both normal and von Willebrand's disease (vWD) animals was exposed to de-endothelialized aorta from normal pigs for a range of shear rates (200 to 3,000 seconds-1) and exposure times (three to 30 minutes) in a tubular perfusion chamber. Variations in the method of inhibiting coagulation (none, heparin, citrate, hirudin, and EDTA) and of perfusing blood (in vitro v ex vivo) were compared by determining the influence of wall shear rate and vWF on the deposition of 111In-labeled platelets on subendothelium. Whereas platelet deposition was reduced in the absence of vWF for all experimental variations at high shear rates (greater than 850 seconds-1), a defect was observed at low shear rates only when heparinized blood was exposed by means of an ex vivo perfusion system. Maximum sensitivity of the measurement occurs under ex vivo perfusion conditions due to the reduced ability of platelets to deposit in normal blood when recirculated in vitro. Our results indicate that vWF mediates platelet-vessel wall interaction even at low shear rates and that such effect can only be observed in systems where platelet function is minimally affected by the experimental conditions.
11
Badimon, L., JJ Badimon, VT Turitto e V. Fuster. "Role of von Willebrand factor in mediating platelet-vessel wall interaction at low shear rate; the importance of perfusion conditions". Blood 73, n. 4 (1 marzo 1989): 961–67. http://dx.doi.org/10.1182/blood.v73.4.961.bloodjournal734961.
Testo completoAbstract (sommario):
We have previously observed that von Willebrand factor (vWF) plays an important role in platelet deposition on subendothelium at low values of wall shear rate (200 to 400 seconds-1). In the present study, we have investigated the mechanism responsible for such a defect in platelet deposition at low shear rates in the absence of vWF. Blood from both normal and von Willebrand's disease (vWD) animals was exposed to de-endothelialized aorta from normal pigs for a range of shear rates (200 to 3,000 seconds-1) and exposure times (three to 30 minutes) in a tubular perfusion chamber. Variations in the method of inhibiting coagulation (none, heparin, citrate, hirudin, and EDTA) and of perfusing blood (in vitro v ex vivo) were compared by determining the influence of wall shear rate and vWF on the deposition of 111In-labeled platelets on subendothelium. Whereas platelet deposition was reduced in the absence of vWF for all experimental variations at high shear rates (greater than 850 seconds-1), a defect was observed at low shear rates only when heparinized blood was exposed by means of an ex vivo perfusion system. Maximum sensitivity of the measurement occurs under ex vivo perfusion conditions due to the reduced ability of platelets to deposit in normal blood when recirculated in vitro. Our results indicate that vWF mediates platelet-vessel wall interaction even at low shear rates and that such effect can only be observed in systems where platelet function is minimally affected by the experimental conditions.
12
Woods, L. L., H. L. Mizelle e J. E. Hall. "Autoregulation of renal blood flow and glomerular filtration rate in the pregnant rabbit". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 252, n. 1 (1 gennaio 1987): R69—R72. http://dx.doi.org/10.1152/ajpregu.1987.252.1.r69.
Testo completoAbstract (sommario):
Our purpose was to determine whether renal autoregulatory capability is retained in pregnancy despite the marked renal vasodilation that occurs at this time. Renal blood flow and glomerular filtration rate (GFR) were measured in anesthetized pregnant (22–27 days gestation) and nonpregnant rabbits during step reductions in renal perfusion pressure from control (100 +/- 3 mmHg) to 50 mmHg. Control renal blood flow and GFR were significantly higher in pregnant animals, averaging 65 +/- 5 and 13.1 +/- 1.1 ml/min, respectively, compared with 50 +/- 5 and 9.4 +/- 1.2 ml/min in nonpregnant rabbits. Filtration fraction was also significantly elevated in pregnant animals (0.33 +/- 0.02 vs. 0.27 +/- 0.01 in nonpregnant rabbits). During step reductions in renal perfusion pressure, renal blood flow was well autoregulated down to approximately 70 mmHg in both nonpregnant and pregnant animals, falling by only 9 +/- 4 and 12 +/- 5%, respectively. Likewise, GFR was also well autoregulated, falling by 10 +/- 2 and 8 +/- 3% in nonpregnant and pregnant animals, respectively, when perfusion pressure was reduced from 90 to 70 mmHg. These results suggest that renal autoregulation is preserved in pregnancy despite the fact that the renal circulation is already markedly vasodilated.
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Jin, Qing-Hua, Yuto Ueda, Yuta Ishizuka, Takato Kunitake e Hiroshi Kannan. "Cardiovascular changes induced by central hypertonic saline are accompanied by glutamate release in awake rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 281, n. 4 (1 ottobre 2001): R1224—R1231. http://dx.doi.org/10.1152/ajpregu.2001.281.4.r1224.
Testo completoAbstract (sommario):
To elucidate neurochemical mechanisms responsible for cardiovascular responses induced by central salt loading, we directly perfused the paraventricular nucleus (PVN) of the hypothalamus region with hypertonic saline (0.3 or 0.45 M) by using an in vivo brain microdialysis technique. We then measured the extracellular concentrations of glutamate in the PVN region in conscious rats along with the blood pressure and heart rate. Blood pressure, heart rate, and glutamate levels were increased by perfusion of 0.45 M saline; however, they did not change by perfusion of 0.3 M saline. Next, we examined the possible involvement of glutamate in the cardiovascular responses induced by hypertonic saline. Dizocilpine, a noncompetitive antagonist of the N-methyl-d-aspartate (NMDA) receptor, attenuated the increases of blood pressure and heart rate, although 6-cyano-7-nitroquinoxaline-2,3-dione, an antagonist of the non-NMDA receptor, did not affect the blood pressure and heart rate. Our results show that local perfusion of the hypothalamic PVN region with hypertonic saline elicits a local release of glutamate, which may act via NMDA-type glutamate receptors to produce cardiovascular responses.
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Johns, Edward J. "Role of the Renal Nerves in Modulating Renin Release During Pressure Reduction at the Feline Kidney". Clinical Science 69, n. 2 (1 agosto 1985): 185–95. http://dx.doi.org/10.1042/cs0690185.
Testo completoAbstract (sommario):
1. Experiments were undertaken in pentobarbitone-anaesthetized cats to determine how reflex activation of the renal nerves altered the responsiveness of the kidney to release renin during reductions in renal perfusion pressure. Reflex activation of the renal nerves was achieved by reducing carotid sinus perfusion pressure by 30 mmHg, which increased systemic blood pressure. During this period renal perfusion pressure was regulated at control levels and neither renal blood flow nor glomerular filtration rate changed, but there was a significant decrease in sodium excretion and increase in renin secretion. Renal denervation abolished both these latter responses. 2. Renal perfusion pressure reduction, by 25-30 mmHg, had no effect on renal blood flow or glomerular filtration rate but significantly decreased sodium excretion and increased renin secretion. Simultaneous reduction of carotid sinus and renal perfusion pressures had no effect on renal blood flow or glomerular filtration rate, decreased sodium excretion, and the magnitude of the increase in renin secretion was significantly greater than that obtained with reduction in renal perfusion pressure alone. Renal denervation abolished the increase in renin secretion during these manoeuvres. 3. During atenolol administration, renal haemodynamics and sodium excretion responses to renal pressure reduction were similar to those obtained in the absence of the drug. Renin secretion was increased, but significantly less than in the absence of atenolol. Simultaneous carotid sinus and renal pressure reductions during atenolol administration had no effect on renal haemodynamics, reduced sodium excretion and increased renin secretion, the magnitude of which was significantly greater than that recorded with only renal pressure reduction in the presence of atenolol. 4. Direct electrical stimulation of the renal nerves, at frequencies which caused a 5-10% reduction in renal blood flow, did not change glomerular filtration rate, decreased sodium excretion by 30% and increased the rate of renin secretion twofold. In the presence of atenolol, such renal nerve stimulation reduced renal blood flow to the same degree, did not change filtration rate, decreased sodium excretion by 37% but did not change renin secretion. 5. These results show that the magnitude of the release of renin in response to renal pressure reduction is dependent on activity within the renal nerves, being blunted after denervation, and enhanced during reflex activation of the renal nerves.
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Fu, Chun, Xiaoyan Feng, Dujun Bian, Wanping Du, Xiangquan Wang e Yan Zhao. "Basic T1 Perfusion Magnetic Resonance Imaging Evaluation of the Therapeutic Effect of Neoadjuvant Chemotherapy in Locally Advanced Cervical Cancer". International Journal of Gynecologic Cancer 23, n. 7 (settembre 2013): 1270–78. http://dx.doi.org/10.1097/igc.0b013e31829db950.
Testo completoAbstract (sommario):
ObjectiveThe objective of this study was to evaluate the dynamic changes of blood perfusion coinciding with tumor regression after neoadjuvant chemotherapy (NACT) in locally advanced cervical cancer (LACC).MethodsThirty patients with LACC received conventional 3.0-T magnetic resonance imaging and perfusion-weighted imaging scans at 3 different times (before NACT, 2 weeks after the first NACT, and 2 weeks after the second NACT). Characteristics of time-intensity diagrams and patterns of blood perfusion maps according to the parameter of area under the curve (AUC) were observed. Eight perfusion parameters were compared among 3 time points at 2 different chemotherapy-sensitive groups by the software of Basic T1 Perfusion.ResultsThe effective chemotherapy rate was 73.3% (22/30). The characteristic of time-intensity diagrams in cervical cancer was a rapid onset with plateau. There were 3 patterns of AUC perfusion maps. The common perfusion map was rich blood supply type in the effective chemotherapy group and peripheral blood supply type in the ineffective chemotherapy group. Four parameter values (relative enhancement, maximum enhancement, wash-in rate, and AUC) were significantly reduced 2 weeks after the second NACT than those before the therapy (P = 0.000; P = 0.009; P = 0.011; and P = 0.000) in the effective chemotherapy group, especially the value of relative enhancement 2 weeks after the first NACT, was obviously decreased compared to that before the therapy (P = 0.042). The value of time to peak 2 weeks after the second NACT was significantly longer than that before the therapy in the effective chemotherapy group (P = 0.001). There were no obvious changes of blood perfusion parameters among the 3 different times in the ineffective chemotherapy group.ConclusionsTumor blood perfusion has obviously decreased after effective NACT in the treatment of LACC.
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Seymour, Roger S., Vanya Bosiocic e Edward P. Snelling. "Fossil skulls reveal that blood flow rate to the brain increased faster than brain volume during human evolution". Royal Society Open Science 3, n. 8 (agosto 2016): 160305. http://dx.doi.org/10.1098/rsos.160305.
Testo completoAbstract (sommario):
The evolution of human cognition has been inferred from anthropological discoveries and estimates of brain size from fossil skulls. A more direct measure of cognition would be cerebral metabolic rate, which is proportional to cerebral blood flow rate (perfusion). The hominin cerebrum is supplied almost exclusively by the internal carotid arteries. The sizes of the foramina that transmitted these vessels in life can be measured in hominin fossil skulls and used to calculate cerebral perfusion rate. Perfusion in 11 species of hominin ancestors, from Australopithecus to archaic Homo sapiens , increases disproportionately when scaled against brain volume (the allometric exponent is 1.41). The high exponent indicates an increase in the metabolic intensity of cerebral tissue in later Homo species, rather than remaining constant (1.0) as expected by a linear increase in neuron number, or decreasing according to Kleiber's Law (0.75). During 3 Myr of hominin evolution, cerebral tissue perfusion increased 1.7-fold, which, when multiplied by a 3.5-fold increase in brain size, indicates a 6.0-fold increase in total cerebral blood flow rate. This is probably associated with increased interneuron connectivity, synaptic activity and cognitive function, which all ultimately depend on cerebral metabolic rate.
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DeCampos, K. N., S. H. Keshavjee, L. Tremblay, T. Yamashiro e A. S. Slutsky. "Use of a hypoxic lung as a deoxygenator to provide extended assessment of pulmonary function in rats". Journal of Applied Physiology 80, n. 5 (1 maggio 1996): 1835–40. http://dx.doi.org/10.1152/jappl.1996.80.5.1835.
Testo completoAbstract (sommario):
Isolated perfused lung systems are commonly used to assess lung function in experimental studies. Assessment of hemodynamics and gas-exchange function in these systems is limited by the availability of venous blood. This study describes and validates a rat lung perfusion circuit in which a double-lung block ventilated with a hypoxic gas mixture [inspired O2 fraction (FIO2) 0.04; inspired CO2 fraction 0.08; deoxygenator (Deoxy) block] is used to provide blood with blood gases that are similar to mixed venous values to perfuse a study lung (FIO2 0.21; left lung only). This allows extended assessment of hemodynamics and gas exchange. Fifty adult male Wistar rats (300-400 g) were used as double-lung donors. Twenty-five perfusions (of both Deoxy and study lungs) were performed in four protocols (groups 1-5; n = 5). In protocol 1 (group 1), we tested whether exposure to room air affects the gas composition of the blood in the system. We found that the gas composition of the venous reservoir blood was identical to that of the blood entering the study block. In protocol 2, the effect of perfusion time and perfusion flow rate on the stability of the system was assessed. Lungs were perfused at 4 and 12 ml/min (groups 2 and 3, respectively), and the procedure was discontinued if edema or a marked decline in hemodynamics or gas-exchange function was observed. Pulmonary function was excellent and remained stable for 3 (at 12 ml/min) and 5 h (at 4 ml/min). In protocol 3, we examined whether hypoxic ventilation in the Deoxy lungs affects the stability of the system. Despite the low FIO2 used in the Deoxy lungs, the mean pulmonary arterial pressure-to-blood flow relationships in the study and Deoxy lungs were similar. Finally, in protocol 4, perfusion of a damaged study lung did not impair the function of the system. We conclude that this model permits reliable assessment of pulmonary function in rats under controlled ventilation and perfusion conditions. The use of a Deoxy double-lung block simplifies the perfusion apparatus and eliminates the main cause of instability of other systems that use an anesthetized host animal to provide venous blood.
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Fujita, S., M. Tamazawa e K. Kuroda. "Effects of blood perfusion rate on the optimization of RF-capacitive hyperthermia". IEEE Transactions on Biomedical Engineering 45, n. 9 (1998): 1182–86. http://dx.doi.org/10.1109/10.709562.
Testo completo
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Marn, Jure, Mo Chung e Jurij Iljaž. "Relationship between metabolic rate and blood perfusion under Fanger thermal comfort conditions". Journal of Thermal Biology 80 (febbraio 2019): 94–105. http://dx.doi.org/10.1016/j.jtherbio.2019.01.002.
Testo completo
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Peng, Jianshu, e Yongquan Tian. "A surface heat disturbance method for measuring local tissue blood perfusion rate". Journal of Thermal Science 5, n. 1 (gennaio 1996): 28–33. http://dx.doi.org/10.1007/bf02663729.
Testo completo
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Peng, Jian-Shu, Ya-Qin Xia, Tao Gao, Xun-Lan Lei e Shu-Ying Zhao. "A surface heat disturbance method for measuring local tissue blood perfusion rate". Heat Transfer?Asian Research 29, n. 1 (gennaio 2000): 34–44. http://dx.doi.org/10.1002/(sici)1523-1496(200001)29:1<34::aid-htj4>3.0.co;2-l.
Testo completo
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Mazur, H., V. Merlavsky, B. O. Manko e V. V. Manko. "Dependence of the adaptive capacity of liver mitochondria on preparation method". Visnyk of Lviv University. Biological series, n. 82 (3 novembre 2020): 177–85. http://dx.doi.org/10.30970/vlubs.2020.82.16.
Testo completoAbstract (sommario):
When conducting studies on isolated hepatocytes, it is important to obtain cells that retain the functional properties that are characteristic of the whole organ. Increased blood viscosity during liver perfusion, decreased perfusion pressure in blood vessels, and hence hypoxia, are among the factors that may affect the functional state of isolated hepatocytes. The functional state of cells can be estimated by the adaptive capacity of mitochondria, by inducing maximal respiration rate by uncoupling respiration and oxidative phosphorylation due to the addition of FCCP. The research aimed to investigate the adaptive capacity of mitochondria of isolated hepatocytes using in situ and in vitro liver perfusion. Hepatocytes were isolated by the two-staged Seglen method by in situ and in vitro liver perfusion. Isolated hepatocytes, after 15-minute incubation in the medium without addition or with respective oxidative substrate – glutamine, pyruvate, succinate, monomethyl succinate, α-ketoglutarate, dimethyl-α-ketoglutarate (at a concentration of 2 mM) or glucose (10 mM) – were added into the respiratory chamber and FCCP was added in increasing concentrations. It was established that at in situ liver perfusion maximal rate of uncoupled respiration and the optimal concentration of FCCP was higher than at in vitro liver perfusion. Addition of exogenous substrates to a medium increased the respiration rate of hepatocytes. Upon in situ liver perfusion maximal uncoupled respiration rate increased at all causes except glucose, and at in vitro liver perfusion – only when dimethyl-α-ketoglutarate, succinate and monomethyl succinate were used. The optimal concentration of FCCP at in vitro liver perfusion increased due to the addition of glutamine, pyruvate and monomethyl succinate to the medium, and at in situ liver perfusion – only upon glucose oxidation. In both perfusion methods, the highest maximal rate of uncoupled respiration is with the use of monomethyl succinate and the optimal FCCP concentration – upon pyruvate oxidation. Therefore, in situ liver perfusion is better method to obtain stable and metabolically active hepatocytes in support respiratory processes at a high level then in vitro perfusion.
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Foltan, Maik, Alois Philipp, Laszlo Göbölös, Andreas Holzamer, Roland Schneckenpointner, Karla Lehle, Igor Kornilov, Christof Schmid e Dirk Lunz. "Quantitative assessment of peripheral limb perfusion using a modified distal arterial cannula in venoarterial ECMO settings". Perfusion 34, n. 6 (13 marzo 2019): 503–7. http://dx.doi.org/10.1177/0267659118816934.
Testo completoAbstract (sommario):
In cases of severe cardiopulmonary deterioration, quick establishment of venoarterial extracorporeal membrane oxygenation (ECMO) represents a support modality. After successful arterial peripheral cannulation, a certain grade of peripheral limb malperfusion is a fairly common phenomenon. Detection of peripheral malperfusion is vital, since it can result in compartment syndrome or even loss of the affected limb. To prevent or resolve emerging lower limb ischaemia, a newly designed perfusion catheter is placed into the superficial femoral artery, distal to the arterial cannula via ECMO. The aim of our study was to evaluate flow and haemodynamic characteristics of this novel distal limb perfusion cannula for ECMO therapy and present these important findings for the first time. The distal perfusion cannula blood flow increases in linear correlation with ECMO blood flow The variability of distal perfusion cannula blood flow with a 15 Fr cannula ranges between 160 ± 0.40 mL min−1 at 1.5 L min−1 ECMO flow rate and 480 ± 80 mL min−1 at 5.0 L min−1 ECMO blood flow, respectively. Comparatively, the 17-Fr-sized cannula performs on a scale of 140 ± 20 to 390 ± 60 mL distal perfusion cannula blood flow at 1.5-5.0 L min−1 ECMO blood flow, respectively. The quantitative assessment of the distal perfusion cannula blood flow has revealed that distal perfusion cannula blood flow can measure up to 10% of the ECMO blood flow. Furthermore, it has been also well demonstrated that the novel distal perfusion cannula is sufficient to compensate peripheral limb ischaemia.
24
Slamet Wahyudi, Nanda Raihan Vardiansyah e Putu Hadi Setyorini. "Effect of Blood Perfusion on Temperature Distribution in the Multilayer of the Human Body with Interstitial Hyperthermia Treatment for Tumour Therapy". CFD Letters 14, n. 6 (26 giugno 2022): 102–14. http://dx.doi.org/10.37934/cfdl.14.6.102114.
Testo completoAbstract (sommario):
Blood perfusion is defined as the volume of blood flowing through units of tissue volume per second. In thermoregulation, blood perfusion is a factor that affects heat transfer in the body, the greater the rate of blood perfusion will complicate the distribution of temperature throughout the body. In the study of bioheat transfer, heat transfer in the human body can be used as a therapy. At therapeutic temperatures (above 40°C), cells will die and stop their growth or commonly called hyperthermia therapy. It can allow thermonecrosis in body tissues and can be useful for tumour tissue. Of the various types of hyperthermia therapy, interstitial hyperthermia therapy is considered more effective because heat is directly delivered to tumour tissue to minimize other tissues exposed to therapeutic temperatures. Currently, there are no studies that study the effect of blood perfusion on the treatment of interstitial hyperthermia, even though blood perfusion greatly affects the temperature distribution in the human body/ In this study, heat transfer analysis will be performed on five layers of the human body, namely the epidermis, dermis, fat, muscle, and bones with interstitial application of hyperthermia therapy and affected by blood perfusion with a value of (8x10-4; 4x10-4; 2x10-4; 1x10-3; and 2x10-3)/s completed using finite element method with unsteady conditions in two axial dimensions. The part of the tumour studied is a tumour in the arm (forearm) in the span of 600s. This study shows that blood perfusion affects the value of temperature distribution in five layers of the body in unsteady conditions. The greater the value of blood perfusion flowing in the body, the more difficult the temperature will be to transmit because the blood distributes heat throughout the body faster, the difference between blood perfusion values is quite significant.
25
Kurashina, Toshiaki, Kent A. Kirchner, Joey P. Granger e Ami R. Patel. "Chronic Sodium-Potassium-ATPase Inhibition with Ouabain Impairs Renal Haemodynamics and Pressure Natriuresis in the Rat". Clinical Science 91, n. 4 (1 ottobre 1996): 497–502. http://dx.doi.org/10.1042/cs0910497.
Testo completoAbstract (sommario):
1. Chronic Na+,K+-ATPase inhibition with ouabain induces hypertension in the rat. To examine the role of the kidney in this process, the effect of changes in renal perfusion pressure on glomerular filtration rate, renal blood flow and urinary sodium excretion were determined in rats treated intraperitoneally with ouabain (27.8 μg day−1 kg−1 body weight) or vehicle for 6 weeks. 2. After ouabain administration, baseline mean arterial pressure was significantly higher (P < 0.05) in ouabain-treated rats (151 ± 2 mmHg; n = 9) than in control rats (116 ± 4 mmHg; n = 8). 3. At equivalent renal perfusion pressures, glomerular filtration rate was significantly lower (P < 0.05) in ouabain-treated rats compared with control rats. Glomerular filtration rate was 721 ± 73μl/min at 150 mmHg, and fell significantly to 322 ± 64 μl/min at 100 mmHg. In the control group, glomerular filtration rate was well autoregulated. The glomerular filtration rate autoregulatory index was calculated to determine the ability to maintain glomerular filtration rate during changes in renal perfusion pressure (0 reflects perfect autoregulation; >1 reflects the absence of autoregulation). This index was greater in the ouabain group than in the control group (1.54 ± 0.2 compared with 0.29 ± 0.2; P < 0.05). Renal blood flow showed a similar pattern. 4. Absolute urinary sodium excretion rate was less in ouabain-treated rats than in control rats at equivalent renal perfusion pressures. The slope of the relationship between absolute urinary sodium excretion rate and renal perfusion pressure was greater (P < 0.05) in the control group than in the ouabain group (309.1 ± 57.1 compared with 82.1 ± 14.8 μmol min−1 mmHg−1). 5. Thus, chronic inhibition of Na+,K+-ATPase induces less efficient autoregulation of glomerular filtration rate and renal blood flow as well as a rightward shift in the pressure natriuresis relationship, such that a 25–30 mmHg higher renal perfusion pressure is necessary to excrete any given sodium load. These abnormalities may contribute to the development and maintenance of hypertension in this model.
26
Topping, D. L., G. B. Storer e R. P. Trimble. "Effects of flow rate and insulin on triacylglycerol secretion by perfused rat liver". American Journal of Physiology-Endocrinology and Metabolism 255, n. 3 (1 settembre 1988): E306—E313. http://dx.doi.org/10.1152/ajpendo.1988.255.3.e306.
Testo completoAbstract (sommario):
In rat livers perfused with undiluted rat blood at perfusion rates of 6, 12, or 18 ml/min, hepatic O2 consumption rose with blood flow. Lipogenesis was unaffected by blood flow in control livers and was enhanced by insulin at 12 and 18 ml/min. Very-low-density lipoprotein triacylglycerol secretion also rose with increased flow and was stimulated by insulin at both 6 and 12 ml/min. When glucose was added to livers perfused at 12 or 18 ml/min, uptake was independent of perfusion rate and was slightly stimulated by insulin. Total lipogenesis and the secretion of newly synthesized fatty acids in very-low-density lipoprotein triacylglycerols were unaffected by insulin at either flow rate. The hormone stimulated triacylglycerol secretion at 18 ml/min but inhibited it at 12 ml/min. It seems that in perfused liver, effects of insulin on lipogenesis and very-low-density lipoprotein secretion may be modified not only by changes in O2 consumption (in this case through alterations in blood flow) but also by the choice of substrate.
27
Funk, Wolfgang, e Verena Baldinger. "Microcirculatory Perfusion during Volume Therapy". Anesthesiology 82, n. 4 (1 aprile 1995): 975–82. http://dx.doi.org/10.1097/00000542-199504000-00022.
Testo completoAbstract (sommario):
Background Because of the passage of water and salt molecules into the interstitial space, volume replacement with crystalloid solutions requires an amount at least four times that of lost blood. The resulting tissue edema may interfere with nutritive capillary perfusion and oxygen delivery. To prove this hypothesis, the effects of isovolemic hemodilution (hematocrit 30%) with Ringer's lactate solution or dextran 60 on tissue perfusion and oxygenation were investigated in awake Syrian golden hamsters. Methods Experiments were performed by using a chronic dorsal skinfold window giving access to skeletal muscle tissue (musculus cutaneus) with in vivo microscopy, quantitative video image analysis, and surface oxygen partial pressure electrodes. Central venous and arterial pressures were measured by means of chronically implanted jugular venous and carotid catheters. Results Isovolemic exchange of blood with dextran caused no significant changes in arterial or central venous pressure, heart rate, capillary flow velocity, functional capillary density, or surface oxygen partial pressure during the 1-h observation period. A volume of Ringer's solution equal to four times of the amount of blood lost maintained arterial pressure and heart rate when central venous pressure was kept at predilution control values. However, tissue perfusion determined by counting perfused capillaries per terminal arteriole was reduced by 62%, and mean tissue oxygen partial pressure decreased from 19 to 8 mmHg. Conclusions In this model, volume replacement with artificial colloids yielded hemodynamic stability and adequate tissue oxygen supply, whereas administration of crystalloids alone jeopardized tissue perfusion and oxygenation.
28
Hložková, Jana, Peter Scheer, Ivana Uhríková, Pavel Suchý, Tomáš Parák e Ota Hlinomaz. "Comparison of various methods of ischaemic cardioprotection on vitality of rat heart grafts". Acta Veterinaria Brno 86, n. 2 (2017): 199–206. http://dx.doi.org/10.2754/avb201786020199.
Testo completoAbstract (sommario):
The aim of the study was to compare 4 modes of ischaemic cardioprotection using continuous prograde autologous blood perfusion of the coronary artery in two hypothermic modes (group A, B) or conventional protection by cooled Hartmann solution (group C) or cooled saline (group D) without perfusion of the graft. Male Wistar rats (n = 24) were divided into four groups (A–D). In groups A (22–25 °C) and B (4–8 °C), blood perfusion rate was 10 ml/h and the graft was placed in a water bath. Groups C, D were initially rinsed with cold (4–8 °C) Hartmann solution (C) and cold saline solution (D), next the graft was placed in a water bath of cold (4–8 °C) Hartmann solution (C) or saline solution (D). The observed time was 30 min after the implemented perfusion (A, B) or initial rinsing (C, D). At 30 min, hearts of all the groups were perfused for 10 min with prograde-autologous arterialized blood at room temperature. At perfusion minute 10, blood was collected for biochemical analysis (sample 1). Sample 2 involved blood from a portable syringe infusion pumps (in parallel with sample 1). Pairwise test differences between samples 1 and 2 were significant in all the groups as regards creatine kinase and lactate dehydrogenase values, sampling 1 values being always higher, while cardiac troponin I concentrations were non-significant in the same comparison. The heart rate during the final perfusion was identical in all the groups. Our study has demonstrated that all observed cardioprotection modes are useful for experimental heart grafting.
29
Fedorovich, Andrey A., Yulia I. Loktionova, Elena V. Zharkikh, Maria A. Mikhailova, Julia A. Popova, Alexander V. Suvorov e Evgeny A. Zherebtsov. "Body Position Affects Capillary Blood Flow Regulation Measured with Wearable Blood Flow Sensors". Diagnostics 11, n. 3 (4 marzo 2021): 436. http://dx.doi.org/10.3390/diagnostics11030436.
Testo completoAbstract (sommario):
In this study we demonstrate what kind of relative alterations can be expected in average perfusion and blood flow oscillations during postural changes being measured in the skin of limbs and on the brow of the forehead by wearable laser Doppler flowmetry (LDF) sensors. The aims of the study were to evaluate the dynamics of cutaneous blood perfusion and the regulatory mechanisms of blood microcirculation in the areas of interest, and evaluate the possible significance of those effects for the diagnostics based on blood perfusion monitoring. The study involved 10 conditionally healthy volunteers (44 ± 12 years). Wearable laser Doppler flowmetry monitors were fixed at six points on the body: two devices were fixed on the forehead, on the brow; two were on the distal thirds of the right and left forearms; and two were on the distal thirds of the right and left lower legs. The protocol was used to record three body positions on the tilt table for orthostatic test for each volunteer in the following sequence: (a) supine body position; (b) upright body position (+75°); (c) tilted with the feet elevated above the head and the inclination of body axis of 15° (−15°, Trendelenburg position). Skin blood perfusion was recorded for 10 min in each body position, followed by the amplitude–frequency analysis of the registered signals using wavelet decomposition. The measurements were supplemented with the blood pressure and heart rate for every body position analysed. The results identified a statistically significant transformation in microcirculation parameters of the average level of skin blood perfusion and oscillations of amplitudes of neurogenic, myogenic and cardiac sensors caused by the postural changes. In paper, we present the analysis of microcirculation in the skin of the forehead, which for the first time was carried out in various positions of the body. The area is supplied by the internal carotid artery system and can be of particular interest for evaluation of the sufficiency of blood supply for the brain.
30
Onizuka, M., T. Tanita e N. C. Staub. "Erythrocytes reduce liquid filtration in injured dog lungs". American Journal of Physiology-Heart and Circulatory Physiology 256, n. 2 (1 febbraio 1989): H515—H519. http://dx.doi.org/10.1152/ajpheart.1989.256.2.h515.
Testo completoAbstract (sommario):
In isolated, dog lung lobes with pulmonary vessels filled with different liquids, we measured the rate of weight gain for 5 or 10 min at constant alveolar and vascular pressures under zone 1 conditions (alveolar pressure greater than vascular pressure). We used six different liquids: syngeneic plasma, whole blood (hematocrit = 38 +/- 4%), 4% albumin in Krebs-Ringer solution, washed red blood cells in Krebs-Ringer solution (hematocrit = 37 +/- 6%), and platelet-rich or platelet-poor plasma. We studied the lobes under three conditions: immediate perfusion after removal (less than 30 min), delayed perfusion (2 h or more), or immediate perfusion after removal from air-embolized animals. In lobes that showed low-filtration rate using plasma [less than 0.5 g/(min x 100 g)] substitution of whole blood had no effect on the filtration rate. In lobes that showed high-filtration rates using plasma (delayed perfusion or deliberately injured using air emboli) substitution of whole blood caused a dramatic decrease in the filtration rate, restoring it to the level obtained in uninjured lobes. Platelets had no effect. Thus the red cells specifically reduced abnormally high filtration but did not affect normal filtration. There appear to be three possible mechanisms: 1) red cells physically blocking large leaks; 2) red cells settling on the filtration surface area (osmotic-barrier effect); 3) red cells acting as reducing agents against active oxygen metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)
31
Kelly, L. J., W. Mitzner, E. W. Spannhake, B. Bromberger-Barnea e H. A. Menkes. "Pulmonary blood flow affects recovery from constriction in dog lung periphery". Journal of Applied Physiology 60, n. 5 (1 maggio 1986): 1554–60. http://dx.doi.org/10.1152/jappl.1986.60.5.1554.
Testo completoAbstract (sommario):
The influence of blood flow through the pulmonary circulation on the time course of recovery of the lung periphery from challenge with three bronchoconstrictive agents was studied in dogs. The rate of perfusion of the left lower lobe was varied between 0 and 300 ml/min. A fiber-optic bronchoscope (OD = 5.5 mm) was wedged in a small airway in the same lobe, and resistance to airflow through the collateral system was continuously monitored. The lung was challenged with histamine aerosol for 1 min, or with intravenous boluses of histamine, acetylcholine, or methacholine. The time constant (tau) of recovery from each of the challenges was measured under the various pulmonary blood flow conditions. The mean tau of the recoveries from histamine was inversely related to the rate of blood flow. However, pulmonary blood flow had no effect on recovery from challenge with acetylcholine or methacholine, two agents metabolized by cholinesterase in lung tissue. From this study we conclude that recovery of the lung periphery from histamine is perfusion dependent, whereas recovery from acetylcholine or methacholine is perfusion independent. This suggests that the rate of blood flow through the pulmonary circulation could play an important role in recovery of the peripheral airways from certain mediators of bronchoconstriction.
32
Stanley, W. C., J. L. Hall, C. K. Stone e T. A. Hacker. "Acute myocardial ischemia causes a transmural gradient in glucose extraction but not glucose uptake". American Journal of Physiology-Heart and Circulatory Physiology 262, n. 1 (1 gennaio 1992): H91—H96. http://dx.doi.org/10.1152/ajpheart.1992.262.1.h91.
Testo completoAbstract (sommario):
We assessed the relationship between myocardial glucose metabolism and blood flow during ischemia in eight open-chest swine. Coronary flow was controlled by an extracorporeal perfusion circuit. Left anterior descending coronary arterial (LAD) flow was reduced by 60%, while left circumflex flow was normally perfused. The rate of glucose uptake (Rg) was measured with a coronary infusion of 2-deoxy-D-[14C]glucose and myocardial blood flow with radiolabeled microspheres. Myocardial biopsies were taken after 50 min of ischemia. Regional arterial-venous glucose difference was calculated as Rg per myocardial blood flow. Subendocardial blood flow decreased from 1.27 +/- 0.19 to 0.25 +/- 0.11 ml.g-1.min-1 (P less than 0.0001). The subendocardial arterial-venous glucose difference was greater in the LAD bed (1.38 +/- 0.35 mumol/ml) than the left circumflex coronary arterial perfusion bed (0.10 +/- 03; P less than 0.01); however, there was no statistically significant difference in the rate of glucose uptake between the two beds. Subendocardial glycogen concentration in the LAD perfusion bed was reduced to 26% of circumflex bed values. In conclusion, acute ischemia stimulated a dramatic increase in glucose extraction; however, this did not compensate for the decrease in blood flow, and thus the rate of glucose uptake did not increase significantly. The high rate of glycolysis is primarily supported by accelerated net glycogen breakdown rather than increased glucose uptake.
33
Allsop, TF. "Transfer of Magnesium across the Perfused Choroid Plexus of Sheep". Australian Journal of Biological Sciences 39, n. 2 (1986): 161. http://dx.doi.org/10.1071/bi9860161.
Testo completoAbstract (sommario):
Isolated perfused choroid plexus preparations from sheep were used to study the effects of low concentrations of magnesium in the perfusion fluid on the transfer of magnesium into choroid plexus fluid (CPF). A perfusion fluid of similar electrolyte composition to sheep blood resulted in CPF similar to ventricular cerebrospinal fluid at a rate of 2�2 III min - 1 mg -I dry choroidal tissue. Decreasing the concentration of magnesium in the perfusion fluid caused a fall in the concentration of magnesium in the CPF, although it remained higher than in the perfusion fluid. The rate of transfer of magnesium from the perfusion fluid to the CPF decreased in the presence of high levels of potassium in the perfusion fluid. But decreasing the concentration of calcium in the perfusion fluid had no effect on magnesium transfer rates.
34
Fokin, V. F., N. V. Ponomareva, M. V. Krotenkova, R. N. Konovalov, M. M. Tanashyan e O. V. Lagoda. "TWO PATTERNS ОF CT-BRAIN PERFUSION AND DC-POTENTIALS ОF THE BRAIN EVOKED COGNITIVE TASK IN DISCIRCULATORY ENCEPHALOPATHY PATIENTS". Annals of the Russian academy of medical sciences 67, n. 10 (10 ottobre 2012): 38–43. http://dx.doi.org/10.15690/vramn.v67i10.414.
Testo completoAbstract (sommario):
In patients with discirculatory encephalopathy the influence of verbal fluency test on the characteristics of cerebral perfusion, DC-potentials of the brain, as well as on blood pressure and heart rate was investigated. Two patterns of responses to the verbal fluency test were observed. The first one is the process of generalized activation, manifested by the reduction of the TTP (time to peak) parameters of brain perfusion, the rise of the DC-potentials in all areas of brain and the modulation of blood pressure and heart rate. The second process, directly connected with cognitive processing, was manifested by the shifts of local characteristics of brain perfusion and DC-potentials in the frontal, temporal and central cortex, especially in the left hemisphere. Correlations were found between the characteristics of cerebral perfusion and DC-potentials on the one hand and the number of words during the verbal fluency test performance on the other hand.
35
Akgören, N., e M. Lauritzen. "Stimulus rate-dependence of cerebellar blood flow demonstrated by laser-Doppler perfusion imager". NeuroImage 7, n. 4 (maggio 1998): S274. http://dx.doi.org/10.1016/s1053-8119(18)31107-8.
Testo completo
36
Mathie, RT, JB Desai e KM Taylor. "The effect of normothermic cardiopulmonary bypass on hepatic blood flow in the dog". Perfusion 1, n. 4 (ottobre 1986): 245–53. http://dx.doi.org/10.1177/026765918600100403.
Testo completoAbstract (sommario):
Hepatic blood flow was investigated in two groups of eight anaesthetized dogs during and after one hour of either pulsatile or non-pulsatile cardiopulmonary bypass (CPB). Mean perfusion pressure was maintained at 60 mmHg. Hepatic arterial (HA) and portal venous (PV) blood flows were measured using electromagnetic flow probes, and hepatic O 2 consumption determined. The results demonstrate that: (a) pulsatile CPB reduces peripheral vascular resistance during and after perfusion, and more effectively preserves pump flow rate and cardiac output than non-pulsatile CPB; (b) total liver blood flow is sustained more effectively by pulsatile CPB than by non-pulsatile CPB due to relative preservation of both HA and PV flows; (c) hepatic O2 consumption is only marginally better preserved during and after pulsatile CPB than with non-pulsatile perfusion. We conclude that: (a) pulsatile CPB tends to maintain hepatic blood flow through a relative reduction in HA vascular resistance and an improvement in PV flow produced passively by a greater pump flow rate; (b) pulsatile CPB less effectively benefits hepatic O2 consumption because of poor O2 uptake from the hepatic PV blood supply.
37
Rowan, Simon C., Keith D. Rochfort, Lucie Piouceau, Philip M. Cummins, Malachy O’Rourke e Paul McLoughlin. "Pulmonary endothelial permeability and tissue fluid balance depend on the viscosity of the perfusion solution". American Journal of Physiology-Lung Cellular and Molecular Physiology 315, n. 4 (1 ottobre 2018): L476—L484. http://dx.doi.org/10.1152/ajplung.00437.2017.
Testo completoAbstract (sommario):
Fluid filtration in the pulmonary microcirculation depends on the hydrostatic and oncotic pressure gradients across the endothelium and the selective permeability of the endothelial barrier. Maintaining normal fluid balance depends both on specific properties of the endothelium and of the perfusing blood. Although some of the essential properties of blood needed to prevent excessive fluid leak have been identified and characterized, our understanding of these remains incomplete. The role of perfusate viscosity in maintaining normal fluid exchange has not previously been examined. We prepared a high-viscosity perfusion solution (HVS) with a relative viscosity of 2.5, i.e., within the range displayed by blood flowing in vessels of different diameters in vivo (1.5–4.0). Perfusion of isolated murine lungs with HVS significantly reduced the rate of edema formation compared with perfusion with a standard solution (SS), which had a lower viscosity similar to plasma (relative viscosity 1.5). HVS did not alter capillary filtration pressure. Increased endothelial shear stress produced by increasing flow rates of SS, to mimic the increased shear stress produced by HVS, did not reduce edema formation. HVS significantly reduced extravasation of Evans blue-labeled albumin compared with SS, indicating that it attenuated endothelial leak. These findings demonstrate for the first time that the viscosity of the solution perfusing the pulmonary microcirculation is an important physiological property contributing to the maintenance of normal fluid exchange. This has significant implications for our understanding of fluid homeostasis in the healthy lung, edema formation in disease, and reconditioning of donor organs for transplantation.
38
Arkin, H., K. R. Holmes, M. M. Chen e W. G. Bottje. "Thermal Pulse Decay Method for Simultaneous Measurement of Local Thermal Conductivity and Blood Perfusion: A Theoretical Analysis". Journal of Biomechanical Engineering 108, n. 3 (1 agosto 1986): 208–14. http://dx.doi.org/10.1115/1.3138604.
Testo completoAbstract (sommario):
Presented here is a theoretical analysis of the recently developed thermal pulse decay (TPD) method for a simultaneous measurement of local tissue conductivity and blood perfusion rate. The paper describes the theoretical model upon which the TPD method is based and details its capabilities and limitations. The theoretical aspects that affected the development of the measurement protocol are also discussed. The performance of the method is demonstrated with an experimental example which compares the measurements of local kidney blood perfusion rates made using the TPD method with the total renal blood flow obtained coincidentally using a blood flowmeter, in an anesthetized dog.
39
Barstad, RM, H. Stormorken, L. Orning, RW Stephens, LB Petersen, P. Kierulf e KS Sakariassen. "Reduced thrombus formation in native blood of homozygous factor VII- deficient patients at high arterial wall shear rate". Blood 84, n. 10 (15 novembre 1994): 3371–77. http://dx.doi.org/10.1182/blood.v84.10.3371.3371.
Testo completoAbstract (sommario):
Abstract Inhibition of thrombin formation in flowing native blood reduces thrombus formation on subendothelium, dacron, or collagen fibrils at arterial wall shear rates of 450 to 650 s-1. In the present study, we have investigated the role of low levels of factor VII (FVII) in thrombus formation on collagen fibrils at arterial wall shear rates of 650 s-1 (coronary arteries), 2,600 s-1 (mildly stenosed arteries), and 10,510 s-1 (severely stenosed arteries) in parallel-plate perfusion chambers. In the perfusion chamber with the highest wall shear rate, thrombus formation took place at the apex of an eccentric stenosis, which reduced the cross-sectional area of the blood flow channel by 80%, thus simulating thrombus formation at an atherosclerotic plaque rupture. Native blood from 21 healthy volunteers and 12 homozygous FVII- deficient patients was drawn by a pump directly from an antecubital vein over a surface of fibrillar collagen positioned in the respective perfusion chambers. The patients had FVII coagulant activities ranging from 1.3% to 4.5% and FVII antigen levels of 16% to 23% of normal. Immunoaffinity purification of the patients' FVII followed by electrophoresis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]) and immunoblotting showed a protein with similar molecular mass as normal FVII. In the perfusion studies, a reduction in thrombus volume of 54% of normal (P < .007) at 10,510 s-1 was observed. The deposition of fibrin on the thrombogenic surface and the plasma level of fibrinopeptide A (FPA) in blood samples collected distal to the perfusion chamber were concomitantly reduced (P < .002 and P < .04, respectively). The plasma FPA level was also reduced at 2,600 s-1 (P < .04), but not at 650 s-1. However, at the lower shear conditions, the thrombus volume and the fibrin deposition were within the ranges observed in normal blood. The platelet-collagen adhesion was not affected at any of the three shear conditions. Thus, low plasma levels of FVII result in significantly less formation of thrombin and fibrin in and around growing platelet masses at high shear condition. This may weaken the thrombus stability and reduce platelet recruitment, thereby lowering thrombus volume. In support of this theory, one patient with afibrinogenemia had an 83% reduction in thrombus volume at this high shear condition.
40
Barstad, RM, H. Stormorken, L. Orning, RW Stephens, LB Petersen, P. Kierulf e KS Sakariassen. "Reduced thrombus formation in native blood of homozygous factor VII- deficient patients at high arterial wall shear rate". Blood 84, n. 10 (15 novembre 1994): 3371–77. http://dx.doi.org/10.1182/blood.v84.10.3371.bloodjournal84103371.
Testo completoAbstract (sommario):
Inhibition of thrombin formation in flowing native blood reduces thrombus formation on subendothelium, dacron, or collagen fibrils at arterial wall shear rates of 450 to 650 s-1. In the present study, we have investigated the role of low levels of factor VII (FVII) in thrombus formation on collagen fibrils at arterial wall shear rates of 650 s-1 (coronary arteries), 2,600 s-1 (mildly stenosed arteries), and 10,510 s-1 (severely stenosed arteries) in parallel-plate perfusion chambers. In the perfusion chamber with the highest wall shear rate, thrombus formation took place at the apex of an eccentric stenosis, which reduced the cross-sectional area of the blood flow channel by 80%, thus simulating thrombus formation at an atherosclerotic plaque rupture. Native blood from 21 healthy volunteers and 12 homozygous FVII- deficient patients was drawn by a pump directly from an antecubital vein over a surface of fibrillar collagen positioned in the respective perfusion chambers. The patients had FVII coagulant activities ranging from 1.3% to 4.5% and FVII antigen levels of 16% to 23% of normal. Immunoaffinity purification of the patients' FVII followed by electrophoresis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]) and immunoblotting showed a protein with similar molecular mass as normal FVII. In the perfusion studies, a reduction in thrombus volume of 54% of normal (P < .007) at 10,510 s-1 was observed. The deposition of fibrin on the thrombogenic surface and the plasma level of fibrinopeptide A (FPA) in blood samples collected distal to the perfusion chamber were concomitantly reduced (P < .002 and P < .04, respectively). The plasma FPA level was also reduced at 2,600 s-1 (P < .04), but not at 650 s-1. However, at the lower shear conditions, the thrombus volume and the fibrin deposition were within the ranges observed in normal blood. The platelet-collagen adhesion was not affected at any of the three shear conditions. Thus, low plasma levels of FVII result in significantly less formation of thrombin and fibrin in and around growing platelet masses at high shear condition. This may weaken the thrombus stability and reduce platelet recruitment, thereby lowering thrombus volume. In support of this theory, one patient with afibrinogenemia had an 83% reduction in thrombus volume at this high shear condition.
41
Manohar, M. "Tracheobronchial perfusion during exercise in ponies". Journal of Applied Physiology 68, n. 5 (1 maggio 1990): 2182–85. http://dx.doi.org/10.1152/jappl.1990.68.5.2182.
Testo completoAbstract (sommario):
Tracheobronchial circulation during exercise has previously not been examined. Therefore blood flow to the trachea and bronchi (up to 7th generation of branching) was studied in seven healthy adult ponies at rest and during the 3rd and 10th min of exercise performed at a treadmill speed setting of 25 km/h. The ambient air temperature varied from 19 to 20 degrees C and humidity from 35 to 45%. To determine blood flow radionuclide-labeled 15-microns-diameter microspheres were injected into the left ventricle via a catheter advanced from the left carotid artery (exposed using local anesthesia), and a reference sample was obtained from the aorta. Adequate mixing of microspheres with blood was demonstrated by similar perfusion values for left and right kidneys. Exercise increased heart rate (194 +/- 9 and 200 +/- 7 beats/min) and mean aortic pressure (169 +/- 8 and 156 +/- 4 mmHg) of ponies at 3rd and 10th min. Tracheal blood flow (6.7 +/- 0.5 ml.min-1 x 100 g-1) of resting ponies was only one-third of the bronchial blood flow (21.6 +/- 4.9 ml.min-1 x 100 g-1) Significant changes in tracheal perfusion did not occur at 3rd or 10th min of exercise. Although bronchial perfusion also did not change at the 3rd min of exercise, it rose dramatically to 202.8 +/- 30.3 ml.min-1 x 100 g-1 during the 10th min. Concomitantly, renal blood flow decreased at 10th min of exertion. The large increase in bronchial blood flow at 10th min of exertion may have been necessitated by the need to help dissipate body heat.
42
Huang, Tao, Weibo Zhang, Shuyong Jia, Yuying Tian, Guangjun Wang, Lijian Yang, Ingrid Gaischek, Lu Wang e Gerhard Litscher. "A Transcontinental Pilot Study for Acupuncture Lifting-Thrusting and Twisting-Rotating Manipulations". Evidence-Based Complementary and Alternative Medicine 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/157989.
Testo completoAbstract (sommario):
The goal of this study was to observe possible changes of the skin microvascular perfusion on the acupoints and related areas and to quantify influences of acupuncture stimulation on the volunteers' blood pressure, heart rate, and heart rate variability (HRV). During the measurement, the needling sensations of volunteers were enquired and recorded. Ten healthy volunteers with a mean age ± SD of 25.4 ± 2.6 years were enrolled, and acupuncture stimulation was performed on ST36 (Zusanli, right side), in pure lifting-thrusting or twisting-rotating manipulation. During needling, we observed the changing of microvascular perfusion on ST36, 37, 38, and a control point using MOOR speckle laser blood flow scanning. Electrocardiogram and blood pressure were registered before, during, and after needling. Both lifting-thrusting and twisting-rotating needle manipulations could decrease blood pressure and heart rate while improving HRV significantly. There were significant differences in microvascular perfusion on acupoints ST36, 37, 38, and the control point following these two kinds of needle manipulation. The needling sensation caused by lifting-thrusting is stronger than that of twisting-rotating manipulation. Significant differences between lifting-thrusting and twisting-rotating acupuncture stimulation methods show that the mechanisms may be different and need to be researched thoroughly in the future.
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Newman, John M. B., Carla A. Di Maria, Stephen Rattigan e Michael G. Clark. "Nutritive blood flow affects microdialysis O/I ratio for [14C]ethanol and3H2O in perfused rat hindlimb". American Journal of Physiology-Heart and Circulatory Physiology 281, n. 6 (1 dicembre 2001): H2731—H2737. http://dx.doi.org/10.1152/ajpheart.2001.281.6.h2731.
Testo completoAbstract (sommario):
Changes in the microdialysis outflow-to-inflow (O/I) ratio for [14C]ethanol and3H2O were determined in the perfused rat hindlimb after increases and decreases in nutritive flow mediated by the vasoconstrictors norepinephrine (NE) and serotonin (5-HT), respectively. Microdialysis probes (containing 10 mM [14C]ethanol and 3H2O pumped at 1 or 2 μl/min) were inserted through the calf of the rat. Hindlimb perfusion flow rate was varied from 6 to 56 ml · min−1 · 100 g−1 in the presence of NE, 5-HT, or saline vehicle. The O/I ratios for both tracers were determined at each perfusion flow rate, as was perfusion pressure, oxygen uptake (a surrogate indicator of nutritive flow), and lactate release. Both tracers showed a decreased O/I ratio as hindlimb perfusion flow was increased, with [14C]ethanol being higher than 3H2O. NE decreased the O/I ratio compared with vehicle, and 5-HT increased it for both tracers and both microdialysis flow rates. We conclude that the microdialysis O/I ratio, while able to detect changes in total flow, is also sensitive to changes in nutritive and nonnutritive flow, where the latter still extracts tracer, but less than the former.
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Min, Ji Young, Hyun Jae Chang, Su Jung Chu e Mee Young Chung. "The Perfusion Index of the Ear as a Predictor of Hypotension following the Induction of Anesthesia in Patients with Hypertension: A Prospective Observational Study". Journal of Clinical Medicine 11, n. 21 (27 ottobre 2022): 6342. http://dx.doi.org/10.3390/jcm11216342.
Testo completoAbstract (sommario):
Patients with hypertension develop hemodynamic instability more frequently during anesthesia—particularly post-induction. Therefore, different monitoring methods may be required in patients with hypertension. Perfusion index—the ratio of the pulsatile blood flow to the non-pulsatile static blood flow in a patient’s peripheral tissues, such as the fingers or ears—can show the hemodynamic status of the patient in a non-invasive way. Among the sites used for measuring the perfusion index, it is assumed that the ear is more reliable than the finger for hemodynamic monitoring, because proximity to the brain ensures appropriate perfusion. We hypothesized that the low value of preoperative ear PI could be a predictor of post-induction hypotension in patients with hypertension. Thirty patients with hypertension were enrolled. The perfusion index and pleth variability index were measured using the ear, finger, and blood pressure, and heart rate was recorded to monitor hypotension. After insertion of the supraglottic airway, 20 patients developed post-induction hypotension. Those who developed hypotension showed a significantly lower preoperative perfusion index of the ear. The preoperative perfusion index of the ear could predict post-induction hypotension in patients with hypertension.
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Pearse, D. B., R. G. Brower, N. F. Adkinson e J. T. Sylvester. "Spontaneous injury in isolated sheep lungs: role of perfusate leukocytes and platelets". Journal of Applied Physiology 66, n. 3 (1 marzo 1989): 1287–96. http://dx.doi.org/10.1152/jappl.1989.66.3.1287.
Testo completoAbstract (sommario):
Perfusion of isolated sheep lungs with blood causes spontaneous edema and hypertension preceded by decreases in perfusate concentrations of leukocytes (WBC) and platelets (PLT). To determine whether these decreases were caused by pulmonary sequestration, we continuously measured blood flow and collected pulmonary arterial and left atrial blood for cell concentration measurements in six lungs early in perfusion. Significant sequestration occurred in the lung, but not in the extracorporeal circuit. To determine the contribution of these cells to spontaneous injury in this model, lungs perfused in situ with a constant flow (100 ml.kg-1.min-1) of homologous leukopenic (WBC = 540 mm-3, n = 8) or thrombocytopenic blood (PLT = 10,000 mm-3, n = 6) were compared with control lungs perfused with untreated homologous blood (WBC = 5,320, PLT = 422,000, n = 8). Perfusion of control lungs caused a rapid fall in WBC and PLT followed by transient increases in pulmonary arterial pressure, lung lymph flow, and perfusate concentrations of 6-ketoprostaglandin F1 alpha and thromboxane B2. The negative value of reservoir weight (delta W) was measured as an index of fluid entry into the lung extravascular space during perfusion. delta W increased rapidly for 60 min and then more gradually to 242 g at 180 min. This was accompanied by a rise in the lymph-to-plasma oncotic pressure ratio (pi L/pi P). Relative to control, leukopenic perfusion decreased the ratio of wet weight to dry weight, the intra- plus extravascular blood weight, and the incidence of bloody lymph. Thrombocytopenic perfusion increased lung lymph flow and the rate of delta W, decreased pi L/pi P and perfusate thromboxane B2, and delayed the peak pulmonary arterial pressure. These results suggest that perfusate leukocytes sequestered in the lung and contributed to hemorrhage but were not necessary for hypertension and edema. Platelets were an important source of thromboxane but protected against edema by an unknown mechanism.
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Gladden, L. B., R. E. Crawford e M. J. Webster. "Effect of blood flow on net lactate uptake during steady-level contractions in canine skeletal muscle". Journal of Applied Physiology 72, n. 5 (1 maggio 1992): 1826–30. http://dx.doi.org/10.1152/jappl.1992.72.5.1826.
Testo completoAbstract (sommario):
The purpose of this study was to determine the effect of blood flow on net lactate uptake (L) at constant elevated blood lactate concentration and metabolic rate in the in situ dog gastrocnemius-plantaris (GP) muscle. In all experiments, an infusion of lactate/lactic acid at a pH of 3.8 established a blood lactate concentration of 10–13 mM while maintaining normal blood gas/pH status as the GP was stimulated to contract with twitches at 1 Hz. In series 1 (n = 14), blood flow (ml.kg-1.min-1) was controlled by a pump at either 1) the spontaneous level for 1-Hz contractions (control flow = 332 +/- 23) or 2) a level estimated to be approximately 65% greater (high flow = 543 +/- 42). In series 2 (n = 7), perfusion pressure was varied during 1-Hz contractions. Four different perfusion pressures (80, 120, 155, and 180 Torr) were presented to each GP preparation, resulting in mean flow rates of 308 +/- 34, 419 +/- 30, 492 +/- 37, and 646 +/- 30 ml.kg-1.min-1. Increasing blood flow had no significant effect on net L in series 1. Similarly, there was no significant change in net L across the first three perfusion pressures/flow rates in series 2. However, net L (mmol.kg-1.min-1) was significantly increased in the highest perfusion pressure/flow rate period (from 0.335 +/- 0.029 at 80 Torr to 0.431 +/- 0.034 at 180 Torr). This study suggests that blood flow may have an independent effect on net L at the upper extreme of the normal blood flow range during contractions but very little effect over a fairly wide low-to-middle range of flow rates.
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Donadelli, Roberta, Jennifer N. Orje, Miriam Galbusera, Giuseppe Remuzzi e Zaverio M. Ruggeri. "Regulation of High Shear Rate Induced von Willebrand Factor Mediated Platelet Thrombi by ADAMTS-13 ." Blood 104, n. 11 (16 novembre 2004): 516. http://dx.doi.org/10.1182/blood.v104.11.516.516.
Testo completoAbstract (sommario):
Abstract ADAMTS-13 is a metalloproteinase that cleaves von Willebrand factor (VWF) at the peptide bond Tyr842-Met843 within the A2 domain of the mature subunit, thus contributing to the regulation of multimers size in the circulation. Cleavage is effective on newly released VWF bound to the surface of endothelial cells, but the extent to which the protease acts on circulating VWF or limits the adhesive properties of multimers during thrombus formation remains unclear. To begin to address these questions, we have established a real-time videomicroscopy technique to visualize the formation of platelet aggregates mediated by the binding of VWF A1 domain to the platelet membrane glycoprotein (GP) Ibα. In this process, single platelets first adhere to surface-immobilized VWF, and then bind soluble VWF from plasma and aggregate through a mechanism dependent on shear rate above a critical threshold. Platelet aggregates formed promptly when whole human blood containing the thrombin inhibitor D-phenyl alanyl-L-prolyl-L-arginine chloromethyl ketone dihydrochloride as an anticoagulant (80 μM) was perfused over immobilized VWF at wall shear rates above 10,000 s−1. The size of aggregates increased during the first 5 min of perfusion, then started to decrease and was less than 30% of maximum after 10 min of perfusion. When the metal ion chelator, EDTA (5mM), was added to the blood before perfusion, the size of aggregates was larger than in control blood and showed no decrease over a 10 min period. A similar result was obtained when plasma was removed and washed blood cells were suspended in a buffer containing 20 μg/ml purified VWF multimers, suggesting that a metal ion dependent plasma protease was responsible for the time-dependent reduction of platelet aggregate size. To evaluate this hypothesis, recombinant human ADAMTS-13 purified from the culture medium of stably transfected D. melanogaster cells was added to washed blood cells resuspended in buffer/VWF, and the suspension was perfused over immobilized VWF at shear rates above 10,000 s−1. In this case, VWF-mediated thrombi started to form but began to dissipate within 3 min. After 6 min, the size of thrombi was 30% or less of that seen in the absence of ADAMTS-13. When the latter was added to washed blood cells resuspended in buffer/VWF after 5 min of perfusion, when platelet aggregates had reached their maximum dimensions, a reduction in size to 30% or less of maximum occurred within 5 min. Pre-incubation of ADAMTS-13 with the blood cell/VWF suspension before perfusion did not accelerate or enhance the reduction of platelet aggregate size, indicating that the enzyme likely acts only under flow conditions and/or after VWF multimers are bound to platelet GP Ibα and exposed to shear stress. ADAMTS-13 also had no significant effect on the size of platelet thrombi formed onto collagen type I fibrils at shear rates as high as 6,000 s−1. These findings suggest that ADAMTS-13 provides a selective mechanism to regulate the size of platelet thrombi, but the effect may be limited to conditions under which the cohesion between platelets depends mainly on VWF binding induced by pathologically elevated shear stress.
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Ueno, Katsuhito, Shinichi Takamoto, Takeshi Miyairi, Tetsuro Morota, Ko Shibata, Arata Murakami e Yutaka Kotsuka. "Cerebral Metabolism of Nitric Oxide during Retrograde Cerebral Perfusion". Asian Cardiovascular and Thoracic Annals 10, n. 3 (settembre 2002): 223–27. http://dx.doi.org/10.1177/021849230201000307.
Testo completoAbstract (sommario):
The aim of this study was to determine whether alpha- or pH-stat protects the brain during deep hypothermic retrograde cerebral perfusion. Fifteen anesthetized dogs on cardiopulmonary bypass were cooled to 18°C under alpha-stat and underwent retrograde cerebral perfusion for 90 minutes under alpha-stat or pH-stat, or underwent antegrade cardiopulmonary bypass under alpha-stat as the control. Cerebral blood flow of the cortex was monitored and serial analyses of blood gases and total nitric oxide oxidation products made. Cerebral blood flow and cerebral metabolic rate for oxygen were significantly higher and plasma levels of nitric oxide oxidation products in the outflow from the brain were significantly lower in retrograde cerebral perfusion under pH-stat than under alpha-stat. This study shows that reduced levels of nitric oxide oxidation products may protect against neuronal damage induced by nitric oxide and that increased cerebral blood flow under pH-stat may lead to a reduction of nitric oxide oxidation products. Under retrograde cerebral perfusion, pH-stat is thus better than alpha-stat for protecting the brain.
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Zhu, Liang, Lisa X. Xu, Qinghong He e Sheldon Weinbaum. "A New Fundamental Bioheat Equation for Muscle Tissue—Part II: Temperature of SAV Vessels". Journal of Biomechanical Engineering 124, n. 1 (16 agosto 2001): 121–32. http://dx.doi.org/10.1115/1.1431263.
Testo completoAbstract (sommario):
In this study, a new theoretical framework was developed to investigate temperature variations along countercurrent SAV blood vessels from 300 to 1000 μm diameter in skeletal muscle. Vessels of this size lie outside the range of validity of the Weinbaum-Jiji bioheat equation and, heretofore, have been treated using discrete numerical methods. A new tissue cylinder surrounding these vessel pairs is defined based on vascular anatomy, Murray’s law, and the assumption of uniform perfusion. The thermal interaction between the blood vessel pair and surrounding tissue is investigated for two vascular branching patterns, pure branching and pure perfusion. It is shown that temperature variations along these large vessel pairs strongly depend on the branching pattern and the local blood perfusion rate. The arterial supply temperature in different vessel generations was evaluated to estimate the arterial inlet temperature in the modified perfusion source term for the s vessels in Part I of this study. In addition, results from the current research enable one to explore the relative contribution of the SAV vessels and the s vessels to the overall thermal equilibration between blood and tissue.
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Matsubara, Shunji, Junta Moroi, Akifumi Suzuki, Masahiro Sasaki, Ken Nagata, Iwao Kanno e Shuichi Miura. "Analysis of cerebral perfusion and metabolism assessed with positron emission tomography before and after carotid artery stenting". Journal of Neurosurgery 111, n. 1 (luglio 2009): 28–36. http://dx.doi.org/10.3171/2008.09.17663.
Testo completoAbstract (sommario):
Object The authors analyzed cerebral perfusion and metabolism in patients with internal carotid artery stenosis before and after carotid artery stenting (CAS). Methods Sixteen patients with internal carotid artery stenosis (> 70%) underwent PET scanning before CAS, 1–7 days after CAS, and 3–4 months after CAS to assess a variety of parameters related to cerebral perfusion and metabolism. Results Cerebral blood flow at rest (CBFrest) significantly increased in the immediate postoperative stage before returning to normal levels over the long term; this trend was also recognized on the contralateral side. In contrast, there was gradual improvement in the rate of CBF variation on acetazolamide administration (% CBFaz). Cerebral perfusion pressure (CBF/cerebral blood volume) increased rapidly during the acute stage and decreased in the long term, and the oxygen extraction fraction decreased slightly during the acute stage before normalizing over the long term. The cerebral metabolic rate of oxygen (CMRO2) increased slightly after stenting over both the short and long term. The ratios of ipsilateral to contralateral values (asymmetry index) for CBFrest, % CBFaz, cerebral blood volume, oxygen extraction fraction, and CMRO2 tended to approach 1.0 over time. Conclusions Repeated PET scanning revealed improvements in CBF, perfusion pressure, and oxygen metabolism after CAS. In particular, the vascular reserve tended to improve gradually, while CBF, cerebral perfusion pressure, and CMRO2 increased rapidly and peaked soon after CAS. These results suggest that a large discrepancy between rapidly increased CBF, perfusion pressure, and a small increase in vascular reserve in the acute stage after CAS could cause hyperperfusion syndrome.