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1
Folha, Wladiney Rodrigues, Rafaela Ribeiro Souza, Genilda Canuto Amaral, Alcilane Arnaldo Silva, Jullyanna Nair Carvalho, and Márkilla Zunete Beckmann Cavalcante. "Heliconia ‘Golden Torch’ postharvest: stem ends cutting and renewing vase water benefits." Ornamental Horticulture 22, no. 2 (2016): 180. http://dx.doi.org/10.14295/oh.v22i2.908.
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The postharvest longevity is one of the main aspects that should be considered in the production of cut flowers and is a pre-requisite for product quality and marketing success. However, cut flowers are highly perishable products that need to be treated and stored to maintain its quality and value. This study aimed to assess Heliconia psittacorum ‘Golden Torch’ inflorescences postharvest longevity, submitted to periodic stem ends cutting and vase water renewal. The experimental design was a completely randomized 3x2 factorial, corresponding to the stem ends cuts (1 cm; without cutting; cutting at 24 hours; cutting at 48 hours) and water renewal (with and without renewal), with four repetitions. The assessed variables were: water uptake by flower stems (WUFS); loss of fresh stem mass (LFSM); dry matter of flower stems (DMFS) and postharvest longevity (PHL). The stem cut significantly influenced WUFS and LFSM. However, the water renewal factors affected all variables, while the interaction between factors (stem cuts x water renewal) only influenced PHL. The cuts at the stem base of Heliconia ‘Golden Torch’ procedures enable the restoration of water potential and this practice, associated with water renewal during storage allows greater tissues hydration, maintaining the postharvest quality.
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Grant, Robert. "Values, Means and Ends." Royal Institute of Philosophy Supplement 38 (March 1995): 177–88. http://dx.doi.org/10.1017/s1358246100007359.
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Morals and politics occupy themselves, if not exclusively, then at any rate centrally, with questions of value. Politicians and moralists deplore the alleged decline of values while pressing supposedly new ones upon us. The fiercest sympathies and antipathies, whether between individuals or between societies, are those which stem either from a community or from a divergence of values. ‘So natural to mankind,’ said Mill, ‘is intolerance in whatever they really care about.’
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Travis, John. "Race to Find Human Stem Cells Ends in Tie." Science News 154, no. 19 (1998): 293. http://dx.doi.org/10.2307/4010937.
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Vogel, G. "EUROPEAN UNION: E.U. Stem Cell Debate Ends in a Draw." Science 302, no. 5652 (2003): 1872a—1873. http://dx.doi.org/10.1126/science.302.5652.1872a.
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Harrington, Lea. "Does the reservoir for self-renewal stem from the ends?" Oncogene 23, no. 43 (2004): 7283–89. http://dx.doi.org/10.1038/sj.onc.1207948.
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Jambor, H., S. Mueller, S. L. Bullock, and A. Ephrussi. "A stem-loop structure directs oskar mRNA to microtubule minus ends." RNA 20, no. 4 (2014): 429–39. http://dx.doi.org/10.1261/rna.041566.113.
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Hamilton, M. G., T. T. Herskovits, and J. S. Wall. "Radial mass analysis of unstained STEM images of molluscan hemocyanins." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 3 (1990): 810–11. http://dx.doi.org/10.1017/s0424820100161618.
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The hemocyanins of molluscs are aggregates of a cylindrical decameric subparticle that assembles into di-, tri-, tetra-, penta-, and larger multi-decameric particles with masses that are multiples of the 4.4 Md decamer. Electron micrographs of these hemocyanins typically show the particles with two profiles: circular representing the cylinder viewed from the end and rectangular representing the side-view of the hollow cylinder.The model proposed by Mellema and Klug from image analysis of a didecameric hemocyanin with the two decamers facing one another with collar (closed) ends outward fits the appearance of side-views of the negatively-stained cylinders. These authors also suggested that there might be caps at the ends. In one of a series of transmission electron microscopic studies of molluscan hemocyanins, Siezen and Van Bruggen supported the Mellema-Klug model, but stated that they had never observed a cap component. With STEM we have tested the end cap hypothesis by direct mass measurements across the end-views of unstained particles.
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Włoch, Wiesław, and Beata Zagórska-Marek. "Reconstruction of storeyed cambium in the linden." Acta Societatis Botanicorum Poloniae 51, no. 2 (2014): 215–28. http://dx.doi.org/10.5586/asbp.1982.019.
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Cambium and xylem from the stem of an about 100-year-old linden (<em>Tibia cordata</em>) was examined. Intrusive growth of cells, leading to forking of cell ends and consequently to a change in the contacts of fusiform cells, occurs in the layer of initial cells. This growth gives two configurations, Z and S. Both appear along the same storey boundary, but they are spatially separated (groups of S and Z endings alternate). A unidirectional lateral shift of the growth activity of the ends was observed. In the examined linden stem a storeyed arrangement of rays was found within the stories of fusiform cells.
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Saeed, Hamid, and Mehwish Iqtedar. "Stem cell function and maintenance – ends that matter: Role of telomeres and telomerase." Journal of Biosciences 38, no. 3 (2013): 641–49. http://dx.doi.org/10.1007/s12038-013-9346-3.
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Fakruddin, Md. "Ethics in stem cell research." Bangladesh Journal of Bioethics 3, no. 1 (2012): 13–18. http://dx.doi.org/10.3329/bioethics.v3i1.10867.
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Stem cells have constituted a revolution in regenerative medicine and cancer therapies by providing the possibility of generating multiple therapeutically useful cell types that could be used for treating some of genetic and degenerative disorders. However, human embryonic stem cell research raises few ethical and political controversies because of its involvement in destruction of human embryos. The ethical issues in human embryonic stem cell research encompasses not only with question of the ethics of destroying human embryos, but also with questions about complicity of researchers in destruction of embryos, moral distinction between creating embryos for research purposes and creating them for reproductive ends and the permissibility of cloning human embryos to harvest stem cells. Bangladesh should formulate its own regulations justifying its stand regarding this matter. DOI: http://dx.doi.org/10.3329/bioethics.v3i1.10867 Bangladesh Journal of Bioethics 2012; 3(1):13-18
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Hasty, P., J. Rivera-Pérez, and A. Bradley. "The role and fate of DNA ends for homologous recombination in embryonic stem cells." Molecular and Cellular Biology 12, no. 6 (1992): 2464–74. http://dx.doi.org/10.1128/mcb.12.6.2464.
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We have analyzed the gene-targeting frequencies and recombination products generated by a series of vectors which target the hprt locus in embryonic stem cells and found the existence of alternative pathways that depend on the location of the double-strand break within the vector. A double-strand break in the targeting homology was found to increase the targeting frequency compared with a double-strand break at the edge of or outside the target homology; this finding agrees with the double-strand break repair model proposed for Saccharomyces cerevisiae. Although a double-strand break in the homology is important for efficient targeting, observations reported here suggest that the terminal ends are not always directly involved in the initial recombination event. Short terminal heterologous sequences which block the homologous ends of the vector may be incorporated into the target locus. A modification of the double-strand break repair model is described to account for this observation.
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Hasty, P., J. Rivera-Pérez, and A. Bradley. "The role and fate of DNA ends for homologous recombination in embryonic stem cells." Molecular and Cellular Biology 12, no. 6 (1992): 2464–74. http://dx.doi.org/10.1128/mcb.12.6.2464-2474.1992.
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We have analyzed the gene-targeting frequencies and recombination products generated by a series of vectors which target the hprt locus in embryonic stem cells and found the existence of alternative pathways that depend on the location of the double-strand break within the vector. A double-strand break in the targeting homology was found to increase the targeting frequency compared with a double-strand break at the edge of or outside the target homology; this finding agrees with the double-strand break repair model proposed for Saccharomyces cerevisiae. Although a double-strand break in the homology is important for efficient targeting, observations reported here suggest that the terminal ends are not always directly involved in the initial recombination event. Short terminal heterologous sequences which block the homologous ends of the vector may be incorporated into the target locus. A modification of the double-strand break repair model is described to account for this observation.
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Kalmbach, Keri, LeRoy G. Robinson, Fang Wang, Lin Liu, and David Keefe. "Telomere Length Reprogramming in Embryos and Stem Cells." BioMed Research International 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/925121.
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Telomeres protect and cap linear chromosome ends, yet these genomic buffers erode over an organism’s lifespan. Short telomeres have been associated with many age-related conditions in humans, and genetic mutations resulting in short telomeres in humans manifest as syndromes of precocious aging. In women, telomere length limits a fertilized egg’s capacity to develop into a healthy embryo. Thus, telomere length must be reset with each subsequent generation. Although telomerase is purportedly responsible for restoring telomere DNA, recent studies have elucidated the role of alternative telomeres lengthening mechanisms in the reprogramming of early embryos and stem cells, which we review here.
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Mueller, Alisa A., Tom H. Cheung, and Thomas A. Rando. "All's well that ends well: alternative polyadenylation and its implications for stem cell biology." Current Opinion in Cell Biology 25, no. 2 (2013): 222–32. http://dx.doi.org/10.1016/j.ceb.2012.12.008.
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Włoch, Wiesław, and Ewa Biczewska. "Fibrillation of events in the cambial domains of Tilia cordata Mill." Acta Societatis Botanicorum Poloniae 56, no. 1 (2014): 19–35. http://dx.doi.org/10.5586/asbp.1987.003.
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The cambium and 9 annual growths from a linden stem were studied. Some of the fusiform cell ends changed their contacts-which is shown by the comparison of the cambium layer and terminal parenchyma of the phloem. This means that these ends were active in the period the layers under comparison were formed. The active ends were found in groups numbering a few to ten-odd ends alternating with groups of inactive ends. About 70% of the ends retained their activity for only one year. In the studied areas. in a given year, one direction of migration of the active ends dominated. As a rule, this configuration changed every two years. Along with the change in the configuration of the active ends, the position of the active areas also changed in such a way that after the change of configuration, the areas previously inactive became active. No migration of activity along the borders of the storeys was observed, but only its appearance and disappearance, which was called fibrillation of activity. Fibrillation of activity becomes noticeable when there is a low intensity of events. Because the active areas at a given moment are characterized by one type of configuration of events, the whole studied surface can be seen as a single domain. Fibrillation gives the impression of frequent changes of domain type, these changes, however, are of a different nature than the movement of domain borders found in cambium characterized by a high intensity of events.
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BURKS, ROGER A. "Formation of family group names using the stem of -gaster, with special reference to names based on Miscogaster and Sphegigaster (Hymenoptera: Chalcidoidea: Pteromalidae)." Zootaxa 3389, no. 1 (2012): 61. http://dx.doi.org/10.11646/zootaxa.3389.1.7.
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Article 29.3.1 of the International Code of Zoological Nomenclature dictates that family group names are formed by deleting the case ending from the genitive singular, when the genus ends in a Latin or classical Greek word (ICZN 1999). This process determines the genitive stem of the word. Formation of a family group name based on an incorrect genitive stem is considered an incorrect original spelling, and the Code requires that it be be automatically changed to the correct stem if described before 1999 in cases where this does not create a junior homonym (Article 35.4.1).
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Hejnowicz, Z., and B. Zagórska-Marek. "Mechanism of changes in grain inclination in wood produced by storeyed cambium." Acta Societatis Botanicorum Poloniae 43, no. 3 (2015): 381–98. http://dx.doi.org/10.5586/asbp.1974.036.
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The changes in cell orientation in the cambium of <i>Entandrophragma</i> producing wood with interlocked type of grain, and in the cambium of <i>Tilia</i> in a spirally girdled stem are traced through serial tangential sections of wood. In <i>Entandrophragma</i> the changes result from the intrusive growth of a fusiform cell whih repeatedly produces a new pointed tip from one side of the existing tip which disappears. This causes a sort of creeping of cell ends of one storey past those of the adjoining storey. The oppositely directed ends of the cells belonging to one storey creep in opposite directions so that the position of the cell centres remains constant and only the angle between the cells and the stem axis changes. The stratification of short rays in <i>Entandrophragma</i> represents an adaptation to the changes in celi orientation involved in the formation of interlocked grain. The mechanism of changes in grain inclination in <i>Tilia</i> is intermediate between that based on the creeping of cell ends and that based on pseudotransverse division and intrusive elongation which is known in non-storeyed cambia.
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Raatevaara, Antti, Heikki Korpunen, Harri Mäkinen, and Jori Uusitalo. "Log end face image and stem tapering indicate maximum bow height on Norway spruce bottom logs." European Journal of Forest Research 139, no. 6 (2020): 1079–90. http://dx.doi.org/10.1007/s10342-020-01309-0.
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Abstract In cut-to-length logging, the harvester operator adjusts the bucking in accordance with visible defects on processed stems. Some of the defects, such as a sweep on the bottom of the stem, decrease the yield and quality of sawn products and are difficult for the operator to notice. Detecting the defects with improved sensors would support the operator in his qualitative decision-making and increase value recovery of logging. Predicting the maximum bow height of the bottom log in Norway spruce (Picea abies (L.) Karst.) with log end face image and stem taper was investigated with two modelling approaches. A total of 101 stems were selected from five clear-cut stands in southern Finland. The stems were crosscut and taper measured, and the butt ends of the bottom logs were photographed. The stem diameter, out-of-roundness, and pith eccentricity were measured from the images while the max. bow height was measured by a 3D log scanner at a sawmill. The bottom logs with an eccentric pith had higher max. bow height. In addition, a highly conical bottom part of the stem was more common on the bottom logs with a large max. bow height. Applying both log end face image and stem taper measurements gave the best model fit and detection accuracy (76%) for bottom logs with a large max. bow height. The results indicate that the log end face image and stem taper measurements can be utilised to aid harvester operator in deciding an optimised length for logs according to the bow height.
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Kuhn, Josef, Ulrike Tengler, and Stefan Binder. "Transcript Lifetime Is Balanced between Stabilizing Stem-Loop Structures and Degradation-Promoting Polyadenylation in Plant Mitochondria." Molecular and Cellular Biology 21, no. 3 (2001): 731–42. http://dx.doi.org/10.1128/mcb.21.3.731-742.2001.
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ABSTRACT To determine the influence of posttranscriptional modifications on 3′ end processing and RNA stability in plant mitochondria, peaatp9 and Oenothera atp1 transcripts were investigated for the presence and function of 3′ nonencoded nucleotides. A 3′ rapid amplification of cDNA ends approach initiated at oligo(dT)-adapter primers finds the expected poly(A) tails predominantly attached within the second stem or downstream of the double stem-loop structures at sites of previously mapped 3′ ends. Functional studies in a pea mitochondrial in vitro processing system reveal a rapid removal of the poly(A) tails up to termini at the stem-loop structure but little if any influence on further degradation of the RNA. In contrast 3′ poly(A) tracts at RNAs without such stem-loop structures significantly promote total degradation in vitro. To determine the in vivo identity of 3′ nonencoded nucleotides more accurately, pea atp9 transcripts were analyzed by a direct anchor primer ligation-reverse transcriptase PCR approach. This analysis identified maximally 3-nucleotide-long nonencoded extensions most frequently of adenosines combined with cytidines. Processing assays with substrates containing homopolymer stretches of different lengths showed that 10 or more adenosines accelerate RNA processivity, while 3 adenosines have no impact on RNA life span. Thus polyadenylation can generally stimulate the decay of RNAs, but processivity of degradation is almost annihilated by the stabilizing effect of the stem-loop structures. These antagonistic actions thus result in the efficient formation of 3′ processed and stable transcripts.
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Deng, C., K. R. Thomas, and M. R. Capecchi. "Location of crossovers during gene targeting with insertion and replacement vectors." Molecular and Cellular Biology 13, no. 4 (1993): 2134–40. http://dx.doi.org/10.1128/mcb.13.4.2134.
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Gene targeting was used to introduce nonselectable genetic changes into chromosomal loci in mouse embryo-derived stem cells. The nonselectable markers were linked to a selectable marker in both insertion- and replacement-type vectors, and the transfer of the two elements to the Hprt locus was assayed. When insertion vectors were used as substrates, the frequency of transfer was highly dependent upon the distance between the nonselectable marker and the double-strand break in the vector. A marker located close to the vector ends was frequently lost, suggesting that a double-strand gap repair activity is involved in vector integration. When replacement vectors were used, cotransfer of a selectable marker and a nonselectable marker 3 kb apart was over 50%, suggesting that recombination between vector and target often occurs near the ends of the vector. To illustrate the use of replacement vectors to transfer specific mutations to the genome, we describe targeting of the delta F508 mutation to the CFTR gene in mouse embryo-derived stem cells.
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Deng, C., K. R. Thomas, and M. R. Capecchi. "Location of crossovers during gene targeting with insertion and replacement vectors." Molecular and Cellular Biology 13, no. 4 (1993): 2134–40. http://dx.doi.org/10.1128/mcb.13.4.2134-2140.1993.
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Gene targeting was used to introduce nonselectable genetic changes into chromosomal loci in mouse embryo-derived stem cells. The nonselectable markers were linked to a selectable marker in both insertion- and replacement-type vectors, and the transfer of the two elements to the Hprt locus was assayed. When insertion vectors were used as substrates, the frequency of transfer was highly dependent upon the distance between the nonselectable marker and the double-strand break in the vector. A marker located close to the vector ends was frequently lost, suggesting that a double-strand gap repair activity is involved in vector integration. When replacement vectors were used, cotransfer of a selectable marker and a nonselectable marker 3 kb apart was over 50%, suggesting that recombination between vector and target often occurs near the ends of the vector. To illustrate the use of replacement vectors to transfer specific mutations to the genome, we describe targeting of the delta F508 mutation to the CFTR gene in mouse embryo-derived stem cells.
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Maples, Christopher G., and Johnny A. Waters. "Paleoautecology and systematic re-evaluation of Camptocrinus alabamensis (Mississippian: Chesterian) from northern Alabama." Journal of Paleontology 69, no. 2 (1995): 367–75. http://dx.doi.org/10.1017/s0022336000034685.
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Camptocrinus alabamensis Strimple and Moore, from the Gasperian (Mississippian: Chesterian) part of the Monteagle Limestone and overlying Bangor Limestone in northern Alabama, is the only species of Camptocrinus known to have more than 10 arms. Camptocrinus alabamensis exhibits morphological features (basals that are taller on their posterior ends than on their anterior ends, flattened primanal, shorter posteriormost secundibrachs on C ray and D ray) indicative of a tightly coiled life position, with most of the stem lying along the sediment. Unlike other coiled crinoids, Camptocrinus alabamensis had a double-folded stem and more than 10 arms, which we interpret to have been compromise solutions to the problems of protection from high current energy and predation pressure coupled with the need to lift the animal into a feeding posture. In addition, C. alabamensis is the only dichocrinid exhibiting highly modified pinnules, which may have been used as rheo/chemosensory organs. Camptocrinus alabamensis was a leeward passive suspension feeder that, in times of danger, could fold in its arms and coil tightly against the sediment.Camptocrinus alabamensis is removed from synonymy with C. cirrifer and the diagnosis of Camptocrinus is modified. Species of the genera Camptocrinus and Neocamptocrinus should be used only for specimens in which calyces are known; therefore, the plethora of stem-species erected over the years should all be assigned to stem genera unless adequate calyx descriptions are available.
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Sharma, Nidhi, Brian J. O'Donnell, and James B. Flanegan. "3′-Terminal Sequence in Poliovirus Negative-Strand Templates Is the Primary cis-Acting Element Required for VPgpUpU-Primed Positive-Strand Initiation." Journal of Virology 79, no. 6 (2005): 3565–77. http://dx.doi.org/10.1128/jvi.79.6.3565-3577.2005.
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ABSTRACT The 5′ cloverleaf in poliovirus RNA has a direct role in regulating the stability, translation, and replication of viral RNA. In this study, we investigated the role of stem a in the 5′ cloverleaf in regulating the stability and replication of poliovirus RNA in HeLa S10 translation-replication reactions. Our results showed that disrupting the duplex structure of stem a destabilized viral RNA and inhibited efficient negative-strand synthesis. Surprisingly, the duplex structure of stem a was not required for positive-strand synthesis. In contrast, altering the primary sequence at the 5′-terminal end of stem a had little or no effect on negative-strand synthesis but dramatically reduced positive-strand initiation and the formation of infectious virus. The inhibition of positive-strand synthesis observed in these reactions was most likely a consequence of nucleotide alterations in the conserved sequence at the 3′ ends of negative-strand RNA templates. Previous studies suggested that VPgpUpU synthesized on the cre(2C) hairpin was required for positive-strand synthesis. Therefore, these results are consistent with a model in which preformed VPgpUpU serves as the primer for positive-strand initiation on the 3′AAUUUUGUC5′ sequence at the 3′ ends of negative-strand templates. Our results suggest that this sequence is the primary cis-acting element that is required for efficient VPgpUpU-primed positive-strand initiation.
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Lansdorp, Peter M. "Telomeres, stem cells, and hematology." Blood 111, no. 4 (2008): 1759–66. http://dx.doi.org/10.1182/blood-2007-09-084913.
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Telomeres are highly dynamic structures that adjust the cellular response to stress and growth stimulation based on previous cell divisions. This critical function is accomplished by progressive telomere shortening and DNA damage responses activated by chromosome ends without sufficient telomere repeats. Repair of critically short telomeres by telomerase or recombination is limited in most somatic cells, and apoptosis or cellular senescence is triggered when too many uncapped telomeres accumulate. The chance of the latter increases as the average telomere length decreases. The average telomere length is set and maintained in cells of the germ line that typically express high levels of telomerase. In somatic cells, the telomere length typically declines with age, posing a barrier to tumor growth but also contributing to loss of cells with age. Loss of (stem) cells via telomere attrition provides strong selection for abnormal cells in which malignant progression is facilitated by genome instability resulting from uncapped telomeres. The critical role of telomeres in cell proliferation and aging is illustrated in patients with 50% of normal telomerase levels resulting from a mutation in one of the telomerase genes. Here, the role of telomeres and telomerase in human biology is reviewed from a personal historical perspective.
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Tyree, Melvin T. "Theory of vessel-length determination: the problem of nonrandom vessel ends." Canadian Journal of Botany 71, no. 2 (1993): 297–302. http://dx.doi.org/10.1139/b93-030.
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A theoretical analysis was undertaken to examine the accuracy of algorithms commonly used to compute vessel lengths from paint perfusion experiments. The double-difference (DD) algorithm assumes that all vessels have randomly distributed vessel ends along the axis of the paint-perfused stem and that vessels do not branch. When these conditions were met, the DD algorithm overestimated the frequency of short vessels and underestimated the frequency of long vessels. When these conditions were not met, negative numbers for frequencies were outputted by the DD algorithm. Two algorithms for correcting for negative numbers were examined, one used by Zimmermann and the other used by Ewers and Fisher. Neither algorithm produced the correct result, but the correction algorithm proposed by Ewers and Fisher produced more accurate results. Key words: vessel-length distribution.
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Bicchi, Ilaria, Francesco Morena, Chiara Argentati, et al. "Storage of Mutant Human SOD1 in Non-Neural Cells from the Type-1 Amyotrophic Lateral Sclerosis ratG93A Model Correlated with the Lysosomes’ Dysfunction." Biomedicines 9, no. 9 (2021): 1080. http://dx.doi.org/10.3390/biomedicines9091080.
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Herein, we explored the impact of the lysosome dysfunction during the progression of Amyotrophic Lateral Sclerosis type-1 (ALS1). We conducted the study in non-neural cells, primary fibroblasts (rFFFs), and bone marrow-mesenchymal stem cells (rBM-MSCs), isolated from the animal model ratG93A for ALS1 at two stages of the disease: Pre-symptomatic-stage (ALS1-PreS) and Terminal-stage (ALS1-EndS). We documented the storage of human mutant Superoxide Dismutase 1, SOD1G93A (SOD1*) in the lysosomes of ALS1-rFFFs and ALS1-rBM-MSCs and demonstrated the hallmarks of the disease in non-neural cells as in ratG93A-ALS1-tissues. We showed that the SOD1* storage is associated with the altered glycohydrolases and proteases levels in tissues and both cell types from ALS1-PreS to ALS1-EndS. Only in ALS1-rFFFs, the lysosomes lost homeostasis, enlarge drastically, and contribute to the cell metabolic damage. Contrariwise, in ALS1-rBM-MSCs, we found a negligible metabolic dysfunction, which makes these cells’ status similar to WT. We addressed this phenomenon to a safety mechanism perhaps associated with an enhanced lysosomal autophagic activity in ALS1-rBM-MSCs compared to ALS1-rFFFs, in which the lysosomal level of LC3-II/LC3I was comparable to that of WT-rFFFs. We suggested that the autophagic machinery could balance the storage of SOD1* aggregates and the lysosomal enzyme dysfunction even in ALS1-EndS-stem cells.
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Sailer, Sebastian, Giorgia Sebastiani, Vicente Andreu-Férnández, and Oscar García-Algar. "Impact of Nicotine Replacement and Electronic Nicotine Delivery Systems on Fetal Brain Development." International Journal of Environmental Research and Public Health 16, no. 24 (2019): 5113. http://dx.doi.org/10.3390/ijerph16245113.
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Maternal tobacco smoking during pregnancy remains a major public health issue. The neurotoxic properties of nicotine are associated with fetal neurodevelopmental disorders and perinatal morbimortality. Recent research has demonstrated the effects of nicotine toxicity on genetic and epigenetic alterations. Smoking cessation strategies including nicotine replacement therapy (NRT) and electronic nicotine delivery systems (ENDS) show lack of clear evidence of effectiveness and safety in pregnant women. Limited trials using randomized controls concluded that the intermittent use formulation of NRT (gum, sprays, inhaler) in pregnant women is safe because the total dose of nicotine delivered to the fetus is less than continuous-use formulations (transdermal patch). Electronic nicotine delivery systems (ENDS) were hyped as a safer alternative during pregnancy. However, refill liquids of ENDS are suspected to be cytotoxic for the fetus. Animal studies revealed the impact of ENDS on neural stem cells, showing a similar risk of pre- and postnatal neurobiological and neurobehavioral disorders to that associated with the exposure to traditional tobacco smoking during early life. There is currently no clear evidence of impact on fetal brain development, but recent research suggests that the current guidelines should be reconsidered. The safety of NRT and ENDS is increasingly being called into question. In this review, we discuss the special features (pharmacodynamics, pharmacokinetics, and metabolism) of nicotine, NRT, and ENDS during pregnancy and postnatal environmental exposure. Further, we assess their impact on pre- and postnatal neurodevelopment.
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Koike, S. T. "Occurrence of Stem Rot of Basil, Caused by Sclerotinia sclerotiorum, in Coastal California." Plant Disease 84, no. 12 (2000): 1342. http://dx.doi.org/10.1094/pdis.2000.84.12.1342b.
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In January and February 1999, extensive dieback was observed on commercial basil (Ocimum basilicum) being grown in shadecloth greenhouses in coastal California's Salinas Valley. Symptoms were associated with stems that were high in the plant canopy and had cut ends resulting from multiple harvests of the foliage. Stems had brown discoloration extending from the cut ends toward the crown of the plant. Attached petioles and leaves turned brown and wilted. Profuse white mycelia were generally present externally on symptomatic stems, and occasionally large (>5 mm long) black sclerotia were found inside affected stems. In some shade houses approximately 20 to 25% of the plants were diseased. Isolations from mycelia, sclerotia, and symptomatic stems produced colonies of Sclerotinia sclerotiorum. Inocula for pathogenicity tests were produced by growing isolates on potato-dextrose agar, removing the resulting sclerotia, air drying them for 12 h, and placing them onto sterilized sand saturated with sterile distilled water. Sand cultures were incubated at 24 to 26°C in the light. After 4 to 6 weeks, apothecia containing asci with eight uniform ascospores developed from the sclerotia. Apothecial cultures were placed at the base of potted basil plants that had been trimmed to simulate harvest and placed in a humidity chamber. After 4 weeks, stem dieback was observed on test plants and S. sclerotiorum was recovered from symptomatic tissue. This pathogenicity test was repeated and the results were similar. Though this disease has occurred in the state prior to 1999, this is the first report of S. sclerotiorum on basil in California. This disease has been reported in North America from Canada and Louisiana (2,3). In contrast with reports from Europe (1), basal infections were not observed in the California greenhouses. References: (1) A. Garibaldi et al. Plant Dis. 81:124, 1997. (2) G. E. Holcomb and M. J. Reed. Plant Dis. 78:924, 1994. (3) T. C. Paulitz. Plant Dis. 81:229, 1997.
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Mason, Douglas X., Elizabeth Goneska, and Carol W. Greider. "Stem-Loop IV of Tetrahymena Telomerase RNA Stimulates Processivity in trans." Molecular and Cellular Biology 23, no. 16 (2003): 5606–13. http://dx.doi.org/10.1128/mcb.23.16.5606-5613.2003.
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ABSTRACT Telomerase is a ribonucleoprotein enzyme responsible for the addition of telomeres onto the ends of chromosomes. Short or dysfunctional telomeres can lead to cell growth arrest, apoptosis, and genomic instability. Telomerase uses its RNA subunit to copy a short template region for telomere synthesis. To probe for regions of Tetrahymena telomerase RNA essential for function, we assayed 27 circularly permuted RNA deletions for telomerase in vitro activity and binding to the telomerase reverse transcriptase catalytic protein subunit. We found that stem-loop IV is required for wild-type telomerase activity in vitro and will stimulate processivity when added in trans.
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Lanzotti, David J., Handan Kaygun, Xiao Yang, Robert J. Duronio, and William F. Marzluff. "Developmental Control of Histone mRNA and dSLBP Synthesis during Drosophila Embryogenesis and the Role of dSLBP in Histone mRNA 3′ End Processing In Vivo." Molecular and Cellular Biology 22, no. 7 (2002): 2267–82. http://dx.doi.org/10.1128/mcb.22.7.2267-2282.2002.
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ABSTRACT In metazoans, the 3′ end of histone mRNA is not polyadenylated but instead ends with a stem-loop structure that is required for cell cycle-regulated expression. The sequence of the stem-loop in the Drosophila melanogaster histone H2b, H3, and H4 genes is identical to the consensus sequence of other metazoan histone mRNAs, but the sequence of the stem-loop in the D. melanogaster histone H2a and H1 genes is novel. dSLBP binds to these novel stem-loop sequences as well as the canonical stem-loop with similar affinity. Eggs derived from females containing a viable, hypomorphic mutation in dSLBP store greatly reduced amounts of all five histone mRNAs in the egg, indicating that dSLBP is required in the maternal germ line for production of each histone mRNA. Embryos deficient in zygotic dSLBP function accumulate poly(A)+ versions of all five histone mRNAs as a result of usage of polyadenylation signals located 3′ of the stem-loop in each histone gene. Since the 3′ ends of adjacent histone genes are close together, these polyadenylation signals may ensure the termination of transcription in order to prevent read-through into the next gene, which could possibly disrupt transcription or produce antisense histone mRNA that might trigger RNA interference. During early wild-type embryogenesis, ubiquitous zygotic histone gene transcription is activated at the end of the syncytial nuclear cycles during S phase of cycle 14, silenced during the subsequent G2 phase, and then reactivated near the end of that G2 phase in the well-described mitotic domain pattern. There is little or no dSLBP protein provided maternally in wild-type embryos, and zygotic expression of dSLBP is immediately required to process newly made histone pre-mRNA.
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Pitkänen, Matti, and Reza Rastmanesh. "DNA bioelectric field: a futuristic bioelectric marker of cancer, aging and death – A working hypothesis." Current Cancer Reports 3, no. 1 (2021): 68–79. http://dx.doi.org/10.25082/ccr.2021.01.002.
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Telomeres are associated with the ends of DNA double strands. The lengths of the telomeres are controlled by the telomerase enzyme. The shortening of the telomeres is known to relate to aging. In cancers, telomere lengths are abnormally short. Telomeres could act as buffers shielding the part of DNA coding for the proteins. For cancer cells, germ cells and stem cells the length of the telomeres is not varying. There is an analogy with microtubules, which are highly dynamical and carry a longitudinal electric field, whose strength correlates with the microtubule length. Could sticky ends generate a longitudinal field along DNA double strand with strength determined by the lengths of the sticky ends? In the standard picture the flux of the longitudinal electric field would be proportional to the difference of the negative charges associated with the sticky ends. In TGD framework, DNA strands are accompanied by the dark analog of DNA with codons realized as 3-proton units at magnetic flux tubes parallel to DNA strands and neutralizing the negative charge of ordinary DNA except at the sticky ends. This allows considering the possibility that opposite sticky ends carry opposite charges generating a longitudinal electric field along the magnetic flux tube associated with the system. DNA/Telomere bioelectric field could serve as a novel bioelectric marker to be used for prognostic and diagnostic purposes in researches of cancer, aging, surgery grafts and rejuvenation. We propsed that DNA bioelectric field can be used as a futuristic bioelectric marker of cancer, aging and death.
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Yip, W. S. Vincent, Hideki Shigematsu, David W. Taylor, and Susan J. Baserga. "Box C/D sRNA stem ends act as stabilizing anchors for box C/D di-sRNPs." Nucleic Acids Research 44, no. 18 (2016): 8976–89. http://dx.doi.org/10.1093/nar/gkw576.
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Puławska, Zofia. "Longitudinal arrangement of leaf traces and compound vascular bundles in the stem of Aristolochia clematitis L." Acta Societatis Botanicorum Poloniae 51, no. 3-4 (2014): 361–75. http://dx.doi.org/10.5586/asbp.1982.033.
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The compound vascular bundles in the <em>Aristolochia clematitis</em> stems are entirely composed of leaf traces. At the stage of protoxylem differentiation there is not one vessel in the compound vascular bundle which would belong solely to the stem. In a mature compound vascular bundle less xylem belongs to traces of higher lying leaves than to these of the lower situated ones. The lower ends of the particular traces, components of the compound vascular bundle, gradually become thinner. The traces of the upper leaves are represented in the xylem of the compound vascular bundle in the lower parts of the stem by several or even by only one metaxylem vessel. The latter constitutes a „trace" of the participation of the given leaf in the development of the compound vascular bundle. There are two categories of compound bundles in the stem. One part of these bundles does not reach to the stem apex and they develop on one side. They consist of halves (right and left) of traces of median lower leaves from one orthostichy. The others run uninterruptedly from the base to the stem tip and develop from the middle. They consist, namely, of the median traces (left or right) of lower leaves from the orthostichy and lateral leaf traces (left or right) from the second orthostichy.
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Jung, Taek Kyun, Tadasu Abumiya, Naoya Masahashi, Mok Soon Kim, and Shuji Hanada. "Fabrication of a High Performance Ti Alloy Implant for an Artificial Hip Joint." Materials Science Forum 620-622 (April 2009): 591–94. http://dx.doi.org/10.4028/www.scientific.net/msf.620-622.591.
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A new fabrication process of a stem for an artificial hip joint has been investigated to improve mechanical properties and to reduce both the fabrication cost and consumption of expensive Ti alloys by swaging and die-forging into near-net-shape at room temperature, followed by local heat treatment and precise machining. In this study metastable Ti-Nb-Sn alloys consisting of non-cytotoxic elements (biocompatible Ti alloys) were used for biomedical applications. It is found that swaging at both ends of a rod before die-forging saves material consumption by approximately 50% in comparison with turning, and enhances subsequent age-hardening. In addition the cold die-forging enables the fabrication costs to decrease. It is suggested that high strength of higher than 1100 MPa in the proximal part connected to a stem head and low Young’s modulus of less than 60 GPa in the distal part implanted in a femur can be obtained simultaneously in advanced Ti alloy stems.
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Schlaeger, Thorsten M., Hanna K. A. Mikkola, Christos Gekas, Hildur B. Helgadottir, and Stuart H. Orkin. "Tie2Cre-mediated gene ablation defines the stem-cell leukemia gene (SCL/tal1)–dependent window during hematopoietic stem-cell development." Blood 105, no. 10 (2005): 3871–74. http://dx.doi.org/10.1182/blood-2004-11-4467.
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AbstractThe stem-cell leukemia gene (SCL/tal1) is essential for the formation of all blood lineages. SCL is first expressed in mesodermal cells that give rise to embryonic blood cells, and continues to be expressed in fetal and adult hematopoietic stem cells (HSCs). However, SCL is not required for the maintenance of established long-term repopulating (LTR) HSCs in the adult. The time point at which HSC development becomes SCL independent has not been defined. Tyrosine kinase with immunoglobulin and epidermal growth factor homology domains–2 (Tie2) expression appears in hemogenic and vasculogenic sites shortly after SCL. We therefore used the Tie2Cre mouse to inactivate SCL early during embryonic and fetal hematopoiesis. Tie2Cre completely inactivated SCL in yolk sac, the aortagonad-mesonephros (AGM) region, and fetal liver hematopoietic cells and circulating blood cells. However, the fetal liver was colonized by functional LTR-HSCs. Yet SCL remained crucial for proper differentiation of both primitive and definitive red cells and megakaryocytes. These results indicate that the SCL-dependent phase of HSC development ends before Tie2Cre-mediated gene ablation becomes effective.
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Verfaillie, Catherine M., Martin F. Pera, and Peter M. Lansdorp. "Stem Cells: Hype and Reality." Hematology 2002, no. 1 (2002): 369–91. http://dx.doi.org/10.1182/asheducation-2002.1.369.
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Abstract This update discusses what is known regarding embryonic and adult tissue-derived pluripotent stem cells, including the mechanisms underlying self-renewal without senescence, differentiation in multiple cell types both in vitro and in vivo, and future potential clinical uses of such stem cells. In Section I, Dr. Lansdorp reviews the structure and function of telomerase, the enzyme that restores telomeric ends of chromosomes upon cell division, highly present in embryonic stem cells but not adult stem cells. He discusses the structure and function of telomerase and signaling pathways activated by the enzyme, with special emphasis on normal and leukemic hematopoietic stem cells. In Section II, Dr. Pera reviews the present understanding of mammalian pluripotent embryonic stem cells. He discusses the concept of pluripotentiality in its embryonic context, derivation of stem cells from embryonic or fetal tissue, the basic properties of the stem cells, and methods to produce specific types of differentiated cell from stem cells. He examines the potential applications of stem cells in research and medicine and some of the barriers that must be crossed to achieve these goals. In Section III, Dr. Verfaillie reviews the present understanding of pluripotency of adult stem cells. She discusses the concept of stem cell plasticity, a term used to describe the greater potency described by several investigators of adult tissue-derived stem cells, critically reviews the published studies demonstrating stem cell plasticity, and possible mechanisms underlying such plasticity, and examines the possible role of pluripotent adult stem cells in research and medicine.
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Gudima, Severin, Kate Dingle, Ting-Ting Wu, Gloria Moraleda, and John Taylor. "Characterization of the 5′ Ends for Polyadenylated RNAs Synthesized during the Replication of Hepatitis Delta Virus." Journal of Virology 73, no. 8 (1999): 6533–39. http://dx.doi.org/10.1128/jvi.73.8.6533-6539.1999.
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ABSTRACT The genome of hepatitis delta virus (HDV) is a 1,679-nucleotide (nt) single-stranded circular RNA that is predicted to fold into an unbranched rodlike structure. During replication, two complementary RNAs are also detected: an exact complement, referred to as the antigenome, and an 800-nt polyadenylated RNA that could act as the mRNA for the delta antigen. We used a 5′ rapid amplification of cDNA ends procedure, followed by cloning and sequencing, to determine the 5′ ends of the polyadenylated RNAs produced during HDV genome replication following initiation under different experimental conditions. The analyzed RNAs were from the liver of an infected woodchuck and from a liver cell line at 6 days after transfection with either an HDV cDNA or ribonucleoprotein (RNP) complexes assembled in vitro with HDV genomic RNA and purified recombinant small delta protein. In all three situations the 5′ ends mapped specifically to nt 1630. In relationship to what is called the top end of the unbranched rodlike structure predicted for the genomic RNA template, this site is located 10 nt from the top, and in the middle of a 3-nt external bulge. Following transfection with RNP, such specific 5′ ends could be detected as early as 24 h. We next constructed a series of mutants of this predicted bulge region and of an adjacent 6-bp stem and the top 5-nt loop. Some of these mutations decreased the ability of the genome to undergo antigenomic RNA synthesis and accumulation and/or altered the location of the detected 5′ ends. The observed end located at nt 1630, and most of the novel 5′ ends, were consistent with transcription initiation events that preferentially used a purine. The present studies do not prove that the detected 5′ ends correspond to initiation sites and do not establish the hypothesis that there is a promoter element in the vicinity, but they do show that the location of the observed 5′ ends could be controlled by nucleotide sequences at and around nt 1630.
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Abakare, Chris O. "Kantian Ethics And The Hesc Research: A Philosophical Exploration." PREDESTINASI 13, no. 2 (2021): 79. http://dx.doi.org/10.26858/predestinasi.v13i2.19534.
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The scientific reports on the successful use of Human Embryonic Stem cells to cure many sicknesses as provoked a long-standing controversy about the ethics of research involving human embryos. This controversy arises from sharply differing moral views regarding the use of embryos for research purposes. Indeed, an earnest international scholarly debate continues till today over the ethical, legal, and medical issues that arise in this arena. Immanuel Kant (1724-1804) had given a moral guideline that ethical decisions should be made by considering the nature of the act itself, not its consequences. Furthermore, Kant has warned that persons (autonomous agents) have a special moral worth or dignity, which is the basis for the respect that is owed to them. Thus, respect for persons, means never using persons merely as means to our ends, but always treating them also as ends in themselves. Some philosophers like Richard Doerflinger, Michael Novak, Gilbert Meilaender, and Robert P. George have used the Kantian formula of humanity to criticize the argument that spare IVF embryos can be used for stem cell research given their inevitable death and thus lack of properties for future life. However, the purpose of this paper is to take a critical look at the Human Embryonic Stem cells subject matter to investigate the concept of “personhood’, with the maxim of ‘never treating a person as a means’. This paper argues that if we accepts the definition of a person to possess capacities such as ‘rational’ ‘will’ and ‘self-determination’, then IVF embryos is not a person and can therefore be researched upon, used to derive human embryonic stem cells. Hence, Human Embryonic Stem cells research can be carried out within the ambiance of Kant Categorical Imperative without moral conflict.
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Johnson, Dennis A., Randall C. Rowe, and Thomas F. Cummings. "Incidence of Colletotrichum coccodes in Certified Potato Seed Tubers Planted in Washington State." Plant Disease 81, no. 10 (1997): 1199–202. http://dx.doi.org/10.1094/pdis.1997.81.10.1199.
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Incidence of Colletotrichum coccodes in lots of certified seed tubers planted in Washington state, originating from nine western and midwestern states in the United State and two provinces in Canada, ranged from 0 to 90% in 1994 and 0 to 53% in 1995. In 1994, significant interactions between state/province and cultivar, and between seed grower and cultivar, were evident. In 1995, incidence of C. coccodes in seed lots did not vary significantly among states and cultivars. C. coccodes was not isolated from nuclear seed tubers and incidence of infected tubers was higher with higher seed generations. The fungus was isolated from the tuber periderm and outer medulla tissues and isolation frequency was greater from tuber stem ends than from either bud ends or lateral sections. Significantly greater stem infections developed in plants grown from seed tubers in which C. coccodes had been detected than in plants grown from seed tubers from which C. coccodes had not been isolated. This study confirms that C. coccodes is distributed among potato-production areas within seed tubers, and that seed tuber infection increases the incidence of early-season plant infection.
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Tempest, Nicola, Alison Maclean, and Dharani Hapangama. "Endometrial Stem Cell Markers: Current Concepts and Unresolved Questions." International Journal of Molecular Sciences 19, no. 10 (2018): 3240. http://dx.doi.org/10.3390/ijms19103240.
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The human endometrium is a highly regenerative organ undergoing over 400 cycles of shedding and regeneration over a woman’s lifetime. Menstrual shedding and the subsequent repair of the functional layer of the endometrium is a process unique to humans and higher-order primates. This massive regenerative capacity is thought to have a stem cell basis, with human endometrial stromal stem cells having already been extensively studied. Studies on endometrial epithelial stem cells are sparse, and the current belief is that the endometrial epithelial stem cells reside in the terminal ends of the basalis glands at the endometrial/myometrial interface. Since almost all endometrial pathologies are thought to originate from aberrations in stem cells that regularly regenerate the functionalis layer, expansion of our current understanding of stem cells is necessary in order for curative treatment strategies to be developed. This review critically appraises the postulated markers in order to identify endometrial stem cells. It also examines the current evidence supporting the existence of epithelial stem cells in the human endometrium that are likely to be involved both in glandular regeneration and in the pathogenesis of endometrial proliferative diseases such as endometriosis and endometrial cancer.
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Saito, Yoshio, Yuta Shinohara, Subhendu Sekhar Bag, Yoshiki Takeuchi, Katsuhiko Matsumoto, and Isao Saito. "Ends free and self-quenched molecular beacon with pyrene labeled pyrrolocytidine in the middle of the stem." Tetrahedron 65, no. 4 (2009): 934–39. http://dx.doi.org/10.1016/j.tet.2008.10.093.
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Diskin, Sonia, Oleg Feygenberg, Dalia Maurer, Samir Droby, Dov Prusky, and Noam Alkan. "Microbiome Alterations Are Correlated with Occurrence of Postharvest Stem-End Rot in Mango Fruit." Phytobiomes Journal 1, no. 3 (2017): 117–27. http://dx.doi.org/10.1094/pbiomes-05-17-0022-r.
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During storage and ripening, mango fruit develop stem-end rots (SER) that reduce quality, causing significant losses of harvested fruit. The presented results indicate that pathogens, endophytically colonizing the fruit’s stem end, awaken during fruit ripening and cause SER. The main pathogens causing SER in mango grown in Israel were found to be Alternaria alternata and Lasiodiplodia theobromae. Confocal analysis of the sliced stems indicated that the pathogens endophytically colonize the phloem of the fruit’s stem end; they branch into the fruit parenchyma when the pathogen switches to its actively pathogenic stage. We show that the stem ends are also colonized by other microorganisms, including fungi, yeast, and bacteria, which do not cause any apparent symptoms and are considered as true endophytes. Stem-end microbiomes of red (resistant) compared with green (susceptible) mango stored at optimal and suboptimal temperatures were deep sequenced for fungi and bacteria using internal transcribed spacer and 16S, respectively. Our results showed that both fungal and bacterial community changes are dependent on fruit peel color, storage duration, and storage temperature. The stem-end microbiota seems to be very dynamic in terms of interactions and changes. For example, in susceptible fruits, as green mango compared with red mango and in fruit after storage compared with harvested fruit, the abundance of Alternaria (Pleosporaceae) pathogens increased. This increase in pathogenic fungi was correlated with the increased occurrence of SER. In those two scenarios, before the rot developed, the increased amount of fungi was correlated with an increased abundance of chitin-degrading Chitinophagaceae bacteria. In summary, our results show that various conditions modify the microbial community at the stem end and can reduce postharvest SER.
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Huang, Q., M. R. Jacobson, and T. Pederson. "3' processing of human pre-U2 small nuclear RNA: a base-pairing interaction between the 3' extension of the precursor and an internal region." Molecular and Cellular Biology 17, no. 12 (1997): 7178–85. http://dx.doi.org/10.1128/mcb.17.12.7178.
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The spliceosomal small nuclear RNAs U1, U2, U4, and U5 are transcribed by RNA polymerase II as precursors with extensions at their 3' ends. The 3' processing of these pre-snRNAs is not understood in detail. Two pathways of pre-U2 RNA 3' processing in vitro were revealed in the present investigation by using a series of human wild-type and mutant pre-U2 RNAs. Substrates with wild-type 3' ends were initially shortened by three or four nucleotides (which is the first step in vivo), and the correct mature 3' end was then rapidly generated. In contrast, certain mutant pre-U2 RNAs displayed an aberrant 3' processing pathway typified by the persistence of intermediates representing cleavage at each internucleoside bond in the precursor 3' extension. Comparison of the wild-type and mutant pre-U2 RNAs revealed a potential base-pairing interaction between nucleotides in the precursor 3' extension and a sequence located between the Sm domain and stem-loop III of U2 RNA. Substrate processing competition experiments using a highly purified pre-U2 RNA 3' processing activity suggested that only RNAs capable of this base-pairing interaction had high affinity for the pre-U2 RNA 3' processing enzyme. The importance of this postulated base-pairing interaction between the precursor 3' extension and the internal region between the Sm domain and stem-loop III was confirmed by the results obtained with a compensatory substitution that restores the base pairing, which displayed the normal 3' processing reaction. These results implicate a precursor-specific base-paired structure involving sequences on both sides of the mature cleavage site in the 3' processing of human U2 RNA.
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Ratajczak, Mariusz Z., and Magda Kucia. "SARS-CoV-2 infection and overactivation of Nlrp3 inflammasome as a trigger of cytokine “storm” and risk factor for damage of hematopoietic stem cells." Leukemia 34, no. 7 (2020): 1726–29. http://dx.doi.org/10.1038/s41375-020-0887-9.
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Abstract The scientific community faces an unexpected and urgent challenge related to the SARS-CoV-2 pandemic and is investigating the role of receptors involved in entry of this virus into cells as well as pathomechanisms leading to a cytokine “storm,” which in many cases ends in severe acute respiratory syndrome, fulminant myocarditis and kidney injury. An important question is if it may also damage hematopoietic stem progenitor cells?
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Chagin, Andrei S., and Phillip T. Newton. "Postnatal skeletal growth is driven by the epiphyseal stem cell niche: potential implications to pediatrics." Pediatric Research 87, no. 6 (2019): 986–90. http://dx.doi.org/10.1038/s41390-019-0722-z.
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AbstractChildren’s longitudinal growth is facilitated by the activity of the growth plates, cartilage discs located near the ends of the long-bones. In order to elongate these bones, growth plates must continuously generate chondrocytes. Two recent studies have demonstrated that there are stem cells and a stem cell niche in the growth plate, which govern the generation of chondrocytes during the postnatal growth period. The niche, which allows stem cells to renew, appears at the same time as the secondary ossification center (SOC) matures into a bone epiphysis. Thus, the mechanism of chondrocyte generation differs substantially between neonatal and postnatal age, i.e., before and after the formation of the mineralized epiphyses. Hence, at the neonatal age bone growth is based on a consumption of chondro-progenitors whereas postnatally it is based on the activity of the stem cell niche. Here we discuss potential implications of these observations in relation to longitudinal growth, including the effects of estrogens, nutrition and growth hormone.
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Sheikh, Nilofer, and Yogendra Kumar. "Foliar epidermal, stem and petiole anatomy of Meghalayan Dioscorea L. (Dioscoreaceae) and its systematic implication." Bangladesh Journal of Plant Taxonomy 24, no. 1 (2017): 53–63. http://dx.doi.org/10.3329/bjpt.v24i1.33033.
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A comparative anatomical study of eight species of Dioscorea L. from Meghalaya, North East India was carried out in order to evaluate the taxonomic significance of anatomical characters to differentiate the species. Characters were coded and analyzed by PCA and cluster analysis. The combination of selected qualitative and quantitative anatomical characters of foliar epidermis, stem and petiole were significant for identification of species. The characters that contributed most to the separation of the species were type of stomata, length of stomata, stomatal index, leaf epidermal hairs, stem epidermal hairs, layer of stem sclerenchyma, number of vascular bundle in outer ring and inner ring of stem, paired or unpaired metaxylem, presence of phloem at both ends or at one end, presence or absence of starch grain in stem, petiole epidermal hair and presence or absence starch grain and crystal in petiole. An indented dichotomous key based on anatomical characters was constructed to distinguish and identify the species.Keywords: Anatomy; Dioscorea; Cluster Analysis; Principal Component Analysis; Systematics.Bangladesh J. Plant Taxon. 24(1): 5363, 2017 (June)
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Yates, David I., Brandi L. Earp, Foster Levy, and Elaine S. Walker. "Propagation of Sciadopitys verticillata (Thunb.) Sieb. & Zucc. by Stem Cuttings and Properties of Its Latex-like Sap." HortScience 41, no. 7 (2006): 1662–66. http://dx.doi.org/10.21273/hortsci.41.7.1662.
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To improve the success of vegetative propagation of Sciadopitys verticillata, stem cuttings were subjected to three treatments designed to minimize the accumulation of a latex-like sap at the cut ends of stems. A 24-hour soak in water before a hormone dip significantly enhanced rooting success and root mass. The water soak pretreatment was more beneficial to hardwood cuttings compared with softwood cuttings. Cuttings from shade-grown source trees showed the highest rooting success, but source tree age, height, and place of origin were not important factors. The water-insoluble latex-like sap had strong antibacterial activity against 3 of 11 bacterial species tested, but activity was not related to bacterial Gram reaction or the bacterial natural environment. In contrast, pine resins and latexes from selected angiosperms showed no antibacterial activity. The antibacterial component of the Sciadopitys latex-like sap was heat stable and therefore probably not protein based.
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Lindorf, Helga. "Perforated Ray Cells in Saracha Quitensis (Solanaceae)." IAWA Journal 20, no. 1 (1999): 75–77. http://dx.doi.org/10.1163/22941932-90001550.
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This work reports perforated ray cells in the stem wood of Saracha quitensis (Solanaceae), In this species the perforated ray cells were found either isolated or together in groups of 2 to 4, localised mainly on the ends of multi seriate rays, though they may also be observed in the ray body. They are generally larger than other ray cells, with simple perforations, as in vessel elements, located in both radial and tangential walls.
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Shirobokova, N. N., and N. N. Fedina. "Some of the features of the consonant system of the Chalkan language." Languages and Folklore of Indigenous Peoples of Siberia, no. 38 (2019): 51–57. http://dx.doi.org/10.25205/2312-6337-2019-2-51-57.
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In the following article, we describe the changes that have occurred in Chalkan phonetics over the last 70 years. We compare the consonant system data collected by N. A. Baskakov to modern research data of Siberian experimental phonetics. Certain differences between the Chalkan phonetic systems and other Siberian languages are revealed. We also describe the phonetic processes that are currently taking place in the modern Chalkan language. We list the following changes in Chalkan consonantism: nasalization of labial consonants in anlaut (p- → m-), denasalization of labial consonants in inlaut (-m- → -β-), spirantization of occlusive labial phonemes in inlaut (-p- → -β-), replacement of the anlaut č- by the Altai ħ-, removal of the final fricative low-obstruent super-weak -ɣ. In Siberian Turkic languages, including the Chalkan language (as well as some Kipchak languages, including Kyrgyz, Kazakh, etc.), one may observe a process that can be characterized as a shift of phonotactic trends typical for monosyllabic roots in inter-morphemic clusters of consonants. As the model of affix annexation via connective vowels disappeared, the number of inter-morphemic consonant combinations increased, intensifying the processes of assimilation. Cases of progressive assimilation are the most common: if a stem ends with a vowel or a sonorous consonant, the first obstruent consonant of the affix is either voiced or sonorous (tүn=de ‘at night’, palъ=ɡe ‘to the child’ in Chalkan). If a stem ends with a voiceless consonant, the first consonant of the affix is also voiceless (pᴜlᴜt(t)e ‘on a cloud’, kaske ‘to a goose’ in Chalkan). The Chalkan languages possesses traits typical for Southern Siberian Turkic languages; however, it also has traits similar to those of Kipchak languages, namely the relatively high degree of preservation of voiceless intervocalic consonants in stems (whereas in inter-morphemic positions they are voiced).
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Gao, S., and L. Shain. "Effects of water stress on chestnut blight." Canadian Journal of Forest Research 25, no. 6 (1995): 1030–35. http://dx.doi.org/10.1139/x95-112.
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A range of moisture stress was induced in American chestnut (Castaneadentata (Marsh.) Borkh.) stem segments by incubating them in chambers maintained at humidities of 100%, 90%, or 70% or by soaking their unsealed lower ends in water. Stems then were inoculated with mycelial discs or conidial suspensions of a virulent strain of the chestnut blight fungus (Cryphonectriaparasitica (Murr.) Barr, Ep 155 (American Type Culture Collection No. 38755)). Bark osmotic potential and relative turgidity were monitored on these stems during the development of chestnut blight cankers. Canker expansion was greatest on the stem segments that were lowest in bark osmotic potential (−1.8 MPa) and relative turgidity (56.3%), whereas expansion was least on those stems that were highest in bark osmotic potential (−1.1 MPa) and relative turgidity (68.4%). Water stress, however, had little effect on conidial infection of wounds on stems collected during the growing season, but fewer conidial inoculations of wounds were successful on water-stressed stems collected during the dormant season. Bark osmotic potential of living trees ranged from −0.8 to −2.0 MPa in monthly samplings during the year. Mycelial growth and conidial germination of C. parasitica generally was not affected at osmotic potentials above −2.0 MPa (see companion paper). These results indicate that canker expansion, but not necessarily canker initiation, is favored by water stress and that the effects of water stress are greater on the host than on the pathogen.