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1
ANASTASI, ANGELA, CHERRYL HUNT, and HOWARD STEBBINGS. "Isolation of microtubule motors from an insect ovarian system: characterization using a novel motility substratum." Journal of Cell Science 96, no. 1 (1990): 63–69. http://dx.doi.org/10.1242/jcs.96.1.63.
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The ovaries of hemipteran insects contain massive microtubule-based translocation channels known as nutritive tubes, linking nurse cells to the developing oocytes. Translocation, which is in a retrograde direction along the nutritive tube microtubules, has previously been reactivated in vitro. Here, ATPsensitive microtubule-associated proteins (MAPs) have been isolated from the insect ovaries, and beads coated with such proteins applied to salt-treated, detergent-extracted nutritive tube microtubules microdissected from the insect ovaries. These motility substrata are composed of many thousands of parallel microtubules, all with a common known polarity, so that not only are they easily observed, but the direction of any translocation along their length can be readily interpreted. ATP extracts of insect ovarian MAPs, containing both kinesin and dynein, were seen to promote bidirectional movements of beads. Movements in the two directions differed in both rate and form. On fractionation of the ATP extract, those fractions containing kinesin brought about bead movement in an anterograde direction. Fractions containing dynein failed to promote movement of beads, and no single fraction promoted movement of beads in a retrograde direction. Kinesin, while clearly present in the insect ovary, is absent from the nutritive tube translocation channels. The nutritive tubes, however, contain a polypeptide that co-electrophoreses with insect ovarian dynein, making dynein a possible candidate for the motor that drives the retrograde translocation along nutritive tubes.
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Olsnes, Sjur, Jan Øivind Moskaug, Harald Stenmark, and Kirsten Sandvig. "Diphtheria toxin entry: protein translocation in the reverse direction." Trends in Biochemical Sciences 13, no. 9 (1988): 348–51. http://dx.doi.org/10.1016/0968-0004(88)90105-3.
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Petr, Novák, and Hůla Josef. "Translocation of the upper soil layer in multiple operations of seedbed preparation." Research in Agricultural Engineering 63, Special Issue (2017): S46—S52. http://dx.doi.org/10.17221/40/2017-rae.
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Translocation of tracers incorporated into the upper layer of topsoil was evaluated in the course of seedbed preparation for winter wheat. Aluminium cubes with the edge length of 16 mm were used as tracers that were placed into the soil before its tillage into furrows perpendicular to the direction of passes. After the passes of the OPALL-AGRI combined cultivator, the tracers were searched and marked using a metal detector. The translocation of tracers was evaluated during multiple passes on flatland and on the slope. During the seedbed preparation on the slope, downslope and upslope passes in a fall line direction were chosen. Results of the tracers movement measuring that simulate the soil particle translocation indicate a pronounced movement of the upper layer of topsoil during multiple downslope passes of the combined cultivator. A significant translocation was also observed after passes on flatland. A significantly smaller lengthwise translocation of tracers was found out at upslope passes. The type of translocation on flatland and upslope was quite similar, on the other hand, downslope movement was much larger. The upslope passes were found to have a very limited function with regard to the correction of the undesirable downslope movement of soil particles that occurs in the course of tillage.
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Fasullo, M. T., and R. W. Davis. "Direction of chromosome rearrangements in Saccharomyces cerevisiae by use of his3 recombinational substrates." Molecular and Cellular Biology 8, no. 10 (1988): 4370–80. http://dx.doi.org/10.1128/mcb.8.10.4370.
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We used the his3 recombinational substrates (his3 fragments) to direct large interchromosomal (translocations) and intrachromosomal (deletions and tandem duplications) rearrangements in the yeast Saccharomyces cerevisiae. In strains completely deleted for the wild-type HIS3 gene, his3 fragments, one containing a deletion of 5' amino acid coding sequences and the other containing a deletion of 3' amino acid coding sequences, were first placed at preselected sites by homologous recombination. His+ revertants that arose via spontaneous mitotic recombination between the two his3 fragments were selected. This strategy was used to direct rearrangements in both RAD52+ and rad52 mutant strains. Translocations occurred in the RAD52+ genetic background and were characterized by orthogonal field alternating gel electrophoresis of yeast chromosomal DNA and by standard genetic techniques. An unexpected translocation was also identified in which HIS3 sequences were amplified. Two types of tandem duplications of the GAL(7, 10, 1) locus were also directed, and one type was not observed in rad52 mutants. Recombination mechanisms are discussed to account for these differences.
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Fasullo, M. T., and R. W. Davis. "Direction of chromosome rearrangements in Saccharomyces cerevisiae by use of his3 recombinational substrates." Molecular and Cellular Biology 8, no. 10 (1988): 4370–80. http://dx.doi.org/10.1128/mcb.8.10.4370-4380.1988.
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We used the his3 recombinational substrates (his3 fragments) to direct large interchromosomal (translocations) and intrachromosomal (deletions and tandem duplications) rearrangements in the yeast Saccharomyces cerevisiae. In strains completely deleted for the wild-type HIS3 gene, his3 fragments, one containing a deletion of 5' amino acid coding sequences and the other containing a deletion of 3' amino acid coding sequences, were first placed at preselected sites by homologous recombination. His+ revertants that arose via spontaneous mitotic recombination between the two his3 fragments were selected. This strategy was used to direct rearrangements in both RAD52+ and rad52 mutant strains. Translocations occurred in the RAD52+ genetic background and were characterized by orthogonal field alternating gel electrophoresis of yeast chromosomal DNA and by standard genetic techniques. An unexpected translocation was also identified in which HIS3 sequences were amplified. Two types of tandem duplications of the GAL(7, 10, 1) locus were also directed, and one type was not observed in rad52 mutants. Recombination mechanisms are discussed to account for these differences.
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Buyukdagli, Sahin. "Facilitated polymer capture by charge inverted electroosmotic flow in voltage-driven polymer translocation." Soft Matter 14, no. 18 (2018): 3541–49. http://dx.doi.org/10.1039/c8sm00620b.
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The optimal functioning of nanopore-based sequencing tools necessitates rapid polymer capture by anionic membrane pores. This goal can be achieved by polyvalent cation addition that inverts the direction of the electroosmotic flow. The inverted flow drags the polymer in the trans direction and speeds up its capture by the nanopore.
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Elezovic, Ibrahim, Dragana Bozic, and Sava Vrbnicanin. "Absorption, translocation and metabolism of the sulfonylurea herbicides in plants." Pesticidi 18, no. 4 (2003): 205–22. http://dx.doi.org/10.2298/pif0304205e.
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Absorption, translocation and metabolism are processes affecting the efficacy of sulfonylurea herbicides. These processes contribute significantly to selectivity but are also known to effect the development of plant resistance to this group of herbicides. Sulfonylureas may be absorbed by both ground and above ground plant parts. The level of absorption depends on numerous factors such as: development stage of the plant, ambient temperature, soil humidity, fertilizers added to herbicides, application in combination with other herbicides, sufactants, plant cultivars, mode of herbicide application, various additives. Having been absorbed, the herbicide moves to the place of action whereby the direction of translocation depends on the mode of absorption. Foliary absorbed sulfonylureas are primarily basipetally translocated. Acropetal translocation is correlated to root absorption. In addition, some herbicides belonging to this group are translocated in both directions. The level and rate of translocation depend on: soil humidity, antagonistic effect of other herbicides (in case of application of herbicide combinations), additives, fertilizers etc. Sulfonylureas in plants are subjected to different metabolic changes which mostly contribute to the inactivation. These transformations are considered to be catalyzed by the cytochrom P-450 monooxigenase enzymic system. Eventually, this process is also known to be affected by numerous factors such as: temperature, soil humidity, plant cultivars, mixtures with other pesticides etc.
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Xu, H. C., L. Z. Jia, J. H. Zhang, Z. H. Zhang, and Y. H. Wei. "Combined effects of tillage direction and slope gradient on soil translocation by hoeing." CATENA 175 (April 2019): 421–29. http://dx.doi.org/10.1016/j.catena.2018.12.039.
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Olivares, Adrian O., Hema Chandra Kotamarthi, Benjamin J. Stein, Robert T. Sauer, and Tania A. Baker. "Effect of directional pulling on mechanical protein degradation by ATP-dependent proteolytic machines." Proceedings of the National Academy of Sciences 114, no. 31 (2017): E6306—E6313. http://dx.doi.org/10.1073/pnas.1707794114.
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AAA+ proteases and remodeling machines couple hydrolysis of ATP to mechanical unfolding and translocation of proteins following recognition of sequence tags called degrons. Here, we use single-molecule optical trapping to determine the mechanochemistry of two AAA+ proteases, Escherichia coli ClpXP and ClpAP, as they unfold and translocate substrates containing multiple copies of the titinI27 domain during degradation initiated from the N terminus. Previous studies characterized degradation of related substrates with C-terminal degrons. We find that ClpXP and ClpAP unfold the wild-type titinI27 domain and a destabilized variant far more rapidly when pulling from the N terminus, whereas translocation speed is reduced only modestly in the N-to-C direction. These measurements establish the role of directionality in mechanical protein degradation, show that degron placement can change whether unfolding or translocation is rate limiting, and establish that one or a few power strokes are sufficient to unfold some protein domains.
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Mazauric, Marie-Hélène, Yeonee Seol, Satoko Yoshizawa, Koen Visscher, and Dominique Fourmy. "Interaction of the HIV-1 frameshift signal with the ribosome." Nucleic Acids Research 37, no. 22 (2009): 7654–64. http://dx.doi.org/10.1093/nar/gkp779.
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Abstract Ribosomal frameshifting on viral RNAs relies on the mechanical properties of structural elements, often pseudoknots and more rarely stem-loops, that are unfolded by the ribosome during translation. In human immunodeficiency virus (HIV)-1 type B a long hairpin containing a three-nucleotide bulge is responsible for efficient frameshifting. This three-nucleotide bulge separates the hairpin in two domains: an unstable lower stem followed by a GC-rich upper stem. Toeprinting and chemical probing assays suggest that a hairpin-like structure is retained when ribosomes, initially bound at the slippery sequence, were allowed multiple EF-G catalyzed translocation cycles. However, while the upper stem remains intact the lower stem readily melts. After the first, and single step of translocation of deacylated tRNA to the 30 S P site, movement of the mRNA stem-loop in the 5′ direction is halted, which is consistent with the notion that the downstream secondary structure resists unfolding. Mechanical stretching of the hairpin using optical tweezers only allows clear identification of unfolding of the upper stem at a force of 12.8 ± 1.0 pN. This suggests that the lower stem is unstable and may indeed readily unfold in the presence of a translocating ribosome.
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Wessels, D., and D. R. Soll. "Myosin II heavy chain null mutant of Dictyostelium exhibits defective intracellular particle movement." Journal of Cell Biology 111, no. 3 (1990): 1137–48. http://dx.doi.org/10.1083/jcb.111.3.1137.
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Both cellular motility and intracellular particle movement are compared between normal Dictyostelium amebae of strain AX4 and amebae of a myosin II heavy chain null mutant, HS2215, using the computer assisted "Dynamic Morphology System." In AX4 cells rapidly translocating in buffer, cytoplasmic expansion is apical and the majority of intracellular particles move anteriorly, towards the site of expansion. When these cells are pulsed with 10(-6) M cAMP, the peak concentration of the natural cAMP wave, cells stop translocating and average particle velocity decreases threefold within 2-4 s after cAMP addition. After 8 s, there is a partial rebound both in cytoplasmic expansion and particle velocity, but in both cases, original apical polarity is lost. In HS2215 cells in buffer, both cellular translocation and average particle velocity are already at the depressed levels observed in normal cells immediately after cAMP addition, and no anterior bias is observed in either the direction of cytoplasmic expansion or the direction of particle movement. The addition of cAMP to myosin-minus cells results in no additional effect. The results demonstrate that myosin II is necessary for (a) the rapid rate of intracellular particle movement, (b) the biased anterior directionality of particle movement, and (c) the rapid inhibition of particle movement by cAMP.
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Yu, Hongjun, Tania J. Lupoli, Amanda Kovach, et al. "ATP hydrolysis-coupled peptide translocation mechanism of Mycobacterium tuberculosis ClpB." Proceedings of the National Academy of Sciences 115, no. 41 (2018): E9560—E9569. http://dx.doi.org/10.1073/pnas.1810648115.
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The protein disaggregase ClpB hexamer is conserved across evolution and has two AAA+-type nucleotide-binding domains, NBD1 and NBD2, in each protomer. In M. tuberculosis (Mtb), ClpB facilitates asymmetric distribution of protein aggregates during cell division to help the pathogen survive and persist within the host, but a mechanistic understanding has been lacking. Here we report cryo-EM structures at 3.8- to 3.9-Å resolution of Mtb ClpB bound to a model substrate, casein, in the presence of the weakly hydrolyzable ATP mimic adenosine 5′-[γ-thio]triphosphate. Mtb ClpB existed in solution in two closed-ring conformations, conformers 1 and 2. In both conformers, the 12 pore-loops on the 12 NTDs of the six protomers (P1–P6) were arranged similarly to a staircase around the bound peptide. Conformer 1 is a low-affinity state in which three of the 12 pore-loops (the protomer P1 NBD1 and NBD2 loops and the protomer P2 NBD1 loop) are not engaged with peptide. Conformer 2 is a high-affinity state because only one pore-loop (the protomer P2 NBD1 loop) is not engaged with the peptide. The resolution of the two conformations, along with their bound substrate peptides and nucleotides, enabled us to propose a nucleotide-driven peptide translocation mechanism of a bacterial ClpB that is largely consistent with several recent unfoldase structures, in particular with the eukaryotic Hsp104. However, whereas Hsp104’s two NBDs move in opposing directions during one step of peptide translocation, in Mtb ClpB the two NBDs move only in the direction of translocation.
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Ellefson, Marina L., and Francis J. McNally. "Kinesin-1 and Cytoplasmic Dynein Act Sequentially to Move the Meiotic Spindle to the Oocyte Cortex in Caenorhabditis elegans." Molecular Biology of the Cell 20, no. 11 (2009): 2722–30. http://dx.doi.org/10.1091/mbc.e08-12-1253.
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During female meiosis in animals, the meiotic spindle is attached to the egg cortex by one pole during anaphase to allow selective disposal of half the chromosomes in a polar body. In Caenorhabditis elegans, this anaphase spindle position is achieved sequentially through kinesin-1–dependent early translocation followed by anaphase-promoting complex (APC)-dependent spindle rotation. Partial depletion of cytoplasmic dynein heavy chain by RNA interference blocked spindle rotation without affecting early translocation. Dynein depletion also blocked the APC-dependent late translocation that occurs in kinesin-1–depleted embryos. Time-lapse imaging of green fluorescent protein-tagged dynein heavy chain as well as immunofluorescence with dynein-specific antibodies revealed that dynein starts to accumulate at spindle poles just before the initiation of rotation or late translocation. Accumulation of dynein at poles was kinesin-1 independent and APC dependent, just like dynein driven spindle movements. This represents a case of kinesin-1/dynein coordination in which these two motors of opposite polarity act sequentially and independently on a cargo to move it in the same direction.
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Iida, S., PH Rao, P. Nallasivam, et al. "The t(9;14)(p13;q32) chromosomal translocation associated with lymphoplasmacytoid lymphoma involves the PAX-5 gene." Blood 88, no. 11 (1996): 4110–17. http://dx.doi.org/10.1182/blood.v88.11.4110.4110.
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Abstract The t(9;14)(p13;q32) translocation is associated with approximately 50% of lymphoplasmacytoid lymphoma (LPL), a subtype of B-cell non-Hodgkin's lymphoma (NHL). We cloned the chromosomal breakpoint of der (14) from an LPL case (1052) and showed that it involved a junction between 9p13 and the switch micro region of the Ig heavy chain locus (IgH) on 14q32. Using a YAC contig spanning 1.5 megabase (Mb), we determined that the 9p13 breakpoint in one case (1052) mapped within a 270-kb restriction fragment containing two previously reported 9p breakpoints associated with a alpha-heavy chain disease case (MAL) and KI-1 positive diffuse large cell lymphoma (DLCL) cell line (KIS-1). The same fragment also contained the PAX-5 gene which encodes a B-cell specific transcription factor involved in the control of B-cell proliferation and differentiation. The breakpoints of KIS-1 and 1052 were mapped within the 5′ noncoding region of PAX-5, while the 9p13 breakpoint of MAL mapped 230 to 270 kb upstream to PAX-5. In all three cases, the translocation caused the juxtaposition of the PAX-5 gene to the IgH locus in the opposite direction of transcription. When compared with six other DLCL cell lines lacking t(9;14)(p13;q32), the KIS-1 cell line showed an 11-fold overexpression of PAX-5 mRNA and a significantly reduced expression of the p53 gene, which is normally regulated by PAX-5. Moreover, metaphase and interphase fluorescence in situ hybridization (FISH) analysis using a YAC clone spanning 1 Mb including the PAX-5 as a probe identified chromosomal translocations in 5 of 7 cases carrying 9p13 translocations. These findings suggest that the PAX- 5 gene is the target of the t(9;14) in LPL whereby its expression may be deregulated by juxtaposition to IgH regulatory elements, thus contributing to lymphomagenesis.
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Iida, S., PH Rao, P. Nallasivam, et al. "The t(9;14)(p13;q32) chromosomal translocation associated with lymphoplasmacytoid lymphoma involves the PAX-5 gene." Blood 88, no. 11 (1996): 4110–17. http://dx.doi.org/10.1182/blood.v88.11.4110.bloodjournal88114110.
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The t(9;14)(p13;q32) translocation is associated with approximately 50% of lymphoplasmacytoid lymphoma (LPL), a subtype of B-cell non-Hodgkin's lymphoma (NHL). We cloned the chromosomal breakpoint of der (14) from an LPL case (1052) and showed that it involved a junction between 9p13 and the switch micro region of the Ig heavy chain locus (IgH) on 14q32. Using a YAC contig spanning 1.5 megabase (Mb), we determined that the 9p13 breakpoint in one case (1052) mapped within a 270-kb restriction fragment containing two previously reported 9p breakpoints associated with a alpha-heavy chain disease case (MAL) and KI-1 positive diffuse large cell lymphoma (DLCL) cell line (KIS-1). The same fragment also contained the PAX-5 gene which encodes a B-cell specific transcription factor involved in the control of B-cell proliferation and differentiation. The breakpoints of KIS-1 and 1052 were mapped within the 5′ noncoding region of PAX-5, while the 9p13 breakpoint of MAL mapped 230 to 270 kb upstream to PAX-5. In all three cases, the translocation caused the juxtaposition of the PAX-5 gene to the IgH locus in the opposite direction of transcription. When compared with six other DLCL cell lines lacking t(9;14)(p13;q32), the KIS-1 cell line showed an 11-fold overexpression of PAX-5 mRNA and a significantly reduced expression of the p53 gene, which is normally regulated by PAX-5. Moreover, metaphase and interphase fluorescence in situ hybridization (FISH) analysis using a YAC clone spanning 1 Mb including the PAX-5 as a probe identified chromosomal translocations in 5 of 7 cases carrying 9p13 translocations. These findings suggest that the PAX- 5 gene is the target of the t(9;14) in LPL whereby its expression may be deregulated by juxtaposition to IgH regulatory elements, thus contributing to lymphomagenesis.
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Wessels, D., N. A. Schroeder, E. Voss, A. L. Hall, J. Condeelis, and D. R. Soll. "cAMP-mediated inhibition of intracellular particle movement and actin reorganization in Dictyostelium." Journal of Cell Biology 109, no. 6 (1989): 2841–51. http://dx.doi.org/10.1083/jcb.109.6.2841.
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Before addition of cAMP, Dictyostelum amoebae rapidly translocating in buffer are elongate, exhibit expansion zones primarily at the anterior end and filamentous actin (F-actin) localization primarily in the anterior pseudopodia. Intracellular particle movement is primarily in the anterior direction, and the average rate of particle movement is roughly five times the rate of cellular translocation. Within seconds after the addition of 10(-6)M cAMP, there is a dramatic suppression of cellular translocation, an inhibition of pseudopod formation, a freeze in cellular morphology, a dramatic depression in intracellular particle movement, loss of F-actin localization in pseudopodia concomitant with relocalization of F-actin in the general cytoplasmic cortex under the plasma membrane, and a doubling of F-actin content. After 10 s, expansion zones are again visible at the cell perimeter, but they no longer are localized in the original anterior portion of the cell. There is a slight rebound in particle movement after 10 s, but particles with persistent tracks now show no directionality towards the original anterior portion of the cell, as they did before cAMP addition. Finally, in parallel with the resumption of peripheral expansion and the small rebound in particle movement, there is a decrease in total cellular F-actin to the untreated level. The pattern of microtubule organization is unaffected by the addition of cAMP.
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Chao, Pen-Hsiu Grace, Rani Roy, Robert L. Mauck, Wendy Liu, Wilmot B. Valhmu, and Clark T. Hung. "Chondrocyte Translocation Response to Direct Current Electric Fields." Journal of Biomechanical Engineering 122, no. 3 (2000): 261–67. http://dx.doi.org/10.1115/1.429661.
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Using a custom galvanotaxis chamber and time-lapse digital video microscopy, we report the novel observation that cultured chondrocytes exhibit cathodal migration when subjected to applied direct current (DC) electric fields as low as 0.8 V/cm. The response was dose-dependent for field strengths greater than 4 V/cm. Cell migration appeared to be an active process with extension of cytoplasmic processes in the direction of movement. In some cells, field application for greater than an hour induced elongation of initially round cells accompanied by perpendicular alignment of the long axis with respect to the applied field. Antagonists of the inositol phospholipid pathway, U-73122 and neomycin, were able to inhibit cathodal migration. Cell migration toward the cathode did not require the presence of serum during field application. However, the directed velocity was nearly threefold greater in studies performed with serum. Studies performed at physiologic temperatures ∼37°C revealed a twofold enhancement in migration speed compared to similar studies at room temperature ∼25°C. Findings from the present study may help to elucidate basic mechanisms that mediate chondrocyte migration and substrate attachment. Since chondrocyte migration has been implicated in cartilage healing, the ability to direct chondrocyte movement has the potential to impact strategies for addressing cartilage healing/repair and for development of cartilage substitutes. [S0148-0731(00)00803-7]
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Schroer, T. A., S. T. Brady, and R. B. Kelly. "Fast axonal transport of foreign synaptic vesicles in squid axoplasm." Journal of Cell Biology 101, no. 2 (1985): 568–72. http://dx.doi.org/10.1083/jcb.101.2.568.
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Translocation of intracellular organelles requires interaction with the cellular cytoskeleton, but the membrane and cytoskeletal proteins involved in movement are unknown. Here we show that highly purified synaptic vesicles from electric fish added to extruded squid axoplasm can show ATP-dependent movement. The movement is indistinguishable from that of endogenous vesicles and has a slight preference for the orthograde direction. In the presence of a nonhydrolyzable ATP analog, the synaptic vesicles bind to axoplasmic fibers but do not move. Elastase treatment of vesicles inhibits both binding and movement. We conclude that a protein component on the surface of cholinergic synaptic vesicles from electric fish is conserved during evolution and so can be recognized by the organelle-translocating machinery of the squid axon, resulting in ATP-dependent movement. Synaptic vesicles apparently retain the capacity for fast axonal transport, even after they reach their intracellular destination.
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Janas, T., H. Krajiński, A. Timoszyk, and T. Janas. "Translocation of polysialic acid across model membranes: kinetic analysis and dynamic studies." Acta Biochimica Polonica 48, no. 1 (2001): 163–73. http://dx.doi.org/10.18388/abp.2001_5123.
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Transmembrane translocation of polyion homopolymers takes place in the case of polyanionic polysialic acid (polySia), polyanionic polynucleotides and polycationic polypeptides. The purpose of this work was to determine the role of membrane electrical parameters on the kinetics of polyion translocation, the influence of polysialic acid on ion adsorption on positively charged membrane surface and the dynamics of the phospholipid hydrocarbon chains and choline group by using 1H-NMR. The analysis of polyion translocation was performed by using the electrical equivalent circuit of the membrane for the initial membrane potential equal to zero. The changes in polysialic acid flux was up to 75% after 1 ms in comparison with the zero-time flux. Both a decrease of membrane conductance and an increase of polyion chain length resulted in the diminution of this effect. An increase of praseodymium ions adsorption to positively charged liposomes and an increase of the rate of segmental movement of the -CH2 and -CH3 groups, and the choline headgrup of lipid molecules, was observed in the presence of polySia. The results show that the direction of the vectorial polyion translocation depends both on the membrane electrical properties and the degree of polymerization of the polymer, and that polysialic acid can modulate the degree of ion adsorption and the dynamics of membrane lipids.
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Sherratt, David J., Lidia K. Arciszewska, Estelle Crozat, James E. Graham, and Ian Grainge. "The Escherichia coli DNA translocase FtsK." Biochemical Society Transactions 38, no. 2 (2010): 395–98. http://dx.doi.org/10.1042/bst0380395.
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Escherichia coli FtsK is a septum-located DNA translocase that co-ordinates the late stages of cytokinesis and chromosome segregation. Relatives of FtsK are present in most bacteria; in Bacillus subtilis, the FtsK orthologue, SpoIIIE, transfers the majority of a chromosome into the forespore during sporulation. DNA translocase activity is contained within a ~ 512-amino-acid C-terminal domain, which is divided into three subdomains: α, β and γ. α and β comprise the translocation motor, and γ is a regulatory domain that interacts with DNA and with the XerD recombinase. In vitro rates of translocation of ~ 5 kb·s−1 have been measured for both FtsK and SpoIIIE, whereas, in vivo, SpoIIIE has a comparable rate of translocation. Translocation by both of these proteins is not only rapid, but also directed by DNA sequence. This directionality requires interaction of the γ subdomain with specific 8 bp DNA asymmetric sequences that are oriented co-directionally with replication direction of the bacterial chromosome. The γ subdomain also interacts with the XerCD site-specific recombinase to activate chromosome unlinking by recombination at the chromosomal dif site. In the present paper, the properties in vivo and in vitro of FtsK and its relatives are discussed in relation to the biological functions of these remarkable enzymes.
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Besançon, Thierry E., Katherine M. Jennings, and Wesley J. Everman. "Absorption, Translocation, and Metabolism of Halosulfuron in Cucumber, Summer Squash, and Selected Weeds." Weed Science 65, no. 4 (2017): 461–67. http://dx.doi.org/10.1017/wsc.2017.15.
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Greenhouse studies were conducted to investigate the absorption, translocation, and metabolism of foliar-applied [14C]halosulfuron-methyl in cucumber, summer squash, pitted morningglory, and velvetleaf. Cucumber and summer squash were treated at the 4-leaf stage, whereas velvetleaf and pitted morningglory were treated at 10 cm. All plants were collected at 4, 24, 48, and 72 h after treatment (HAT) for absorption and translocation studies and an additional 96-HAT interval was included in the metabolism study. Absorption did not exceed 45% in summer squash, whereas it plateaued around 60% in velvetleaf and cucumber and reached 80% in pitted morningglory 72 HAT. None of the four species translocated more than 23% of absorbed halosulfuron out of the treated leaf. Translocation in cucumber and summer squash was predominantly basipetal, while acropetal movement prevailed in velvetleaf. No significant direction of movement was observed for pitted morningglory. Negligible translocation occurred toward the roots, regardless of plant species. Of the total amount of [14C]halosulfuron-methyl absorbed into the plants at 96 HAT, more than 80% remained in the form of the parent compound in velvetleaf, summer squash, and pitted morningglory, whereas less than 20% was detected in cucumber. Rapid and high herbicide metabolism may explain cucumber tolerance to halosulfuron-methyl, while lack of metabolism contributes to summer squash and velvetleaf susceptibility. Pitted morningglory tolerance may be due to limited translocation associated with some level of metabolism, but further research would be needed to investigate other potential causes.
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Quine, Timothy A., Les R. Basher, and Andrew P. Nicholas. "Tillage erosion intensity in the South Canterbury Downlands, New Zealand." Soil Research 41, no. 4 (2003): 789. http://dx.doi.org/10.1071/sr02063.
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Growing awareness of the pressure on land resources emphasises the need to understand the full range of processes operating in human-impacted agroecosystems. In such systems one of the greatest threats to long-term sustainability is the erosion and depauperation of soil, which, until recently, was attributed almost entirely to water erosion. This study builds on recent awareness of the significance of tillage erosion and presents the results of an experimental investigation of tillage erosion due to mouldboard ploughing. Aluminium cubes were used to trace soil translocation as a result of a single pass of the plough perpendicular to the contour in downslope and upslope directions. In common with others studies, translocation was found to be directly proportional to slope tangent for downslope tillage and unrelated to slope for upslope tillage. The influence of non-topographic variables on the relationship between translocation distance and slope was partially filtered out by using the ratio of translocation distances in the tillage direction and perpendicular to tillage. Shallow plough depths of 0.17 m produced tillage detachment of only 230 kg/m2; however, a high tillage translocation coefficient of 1.16 m/pass resulted in a soil flux coefficient of 265 kg/m.pass. The high tillage translocation coefficient is probably partly due to the loose nature of the regularly cultivated loessic soil, however, on the basis of comparison with other published studies, it is suggested that the high tillage speed of 7 km/h is the principal control on the magnitude of the coefficient. Analysis of the available data suggests that a 30% reduction in tillage erosion intensity could be obtained by reduction of the tillage speed to 4 km/h; nevertheless, more experimental work is needed to test this suggestion. On the transect studied, a pair of opposing passes of the mouldboard plough would produce erosion rates as high as 5.1 kg/m2.year (51 t/ha.year) from shoulder slope elements and as high as 1.9 kg/m2.year (19 t/ha.year) over half of the slope length. This pattern matched closely the distribution of 137Cs-derived erosion rates documented previously for a nearby field, suggesting that for this environment, as for many mechanised agricultural systems, tillage erosion is the dominant soil redistribution process and the greatest threat to long-term sustained on-site productivity. Reduction of tillage erosion should, therefore, be seen as a priority in the development of sustainable land management strategies.
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Sanguinetti-Scheck, Juan Ignacio, and Michael Brecht. "Home, head direction stability, and grid cell distortion." Journal of Neurophysiology 123, no. 4 (2020): 1392–406. http://dx.doi.org/10.1152/jn.00518.2019.
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The home is a unique location in the life of humans and animals. In rats, home presents itself as a multicompartmental space that involves integrating navigation through subspaces. Here we embedded the laboratory rat’s home cage in the arena, while recording neurons in the animal’s parasubiculum and medial entorhinal cortex, two brain areas encoding the animal’s location and head direction. We found that head direction signals were unaffected by home cage presence or translocation. Head direction cells remain globally stable and have similar properties inside and outside the embedded home. We did not observe egocentric bearing encoding of the home cage. However, grid cells were distorted in the presence of the home cage. While they did not globally remap, single firing fields were translocated toward the home. These effects appeared to be geometrical in nature rather than a home-specific distortion and were not dependent on explicit behavioral use of the home cage during a hoarding task. Our work suggests that medial entorhinal cortex and parasubiculum do not remap after embedding the home, but local changes in grid cell activity overrepresent the embedded space location and might contribute to navigation in complex environments. NEW & NOTEWORTHY Neural findings in the field of spatial navigation come mostly from an abstract approach that separates the animal from even a minimally biological context. In this article we embed the home cage of the rat in the environment to address some of the complexities of natural navigation. We find no explicit home cage representation. While both head direction cells and grid cells remain globally stable, we find that embedded spaces locally distort grid cells.
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Liu, Xiaowen, Tao Yang, Koya Suzuki, et al. "Moesin and myosin phosphatase confine neutrophil orientation in a chemotactic gradient." Journal of Experimental Medicine 212, no. 2 (2015): 267–80. http://dx.doi.org/10.1084/jem.20140508.
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Neutrophils respond to invading bacteria by adopting a polarized morphology, migrating in the correct direction, and engulfing the bacteria. How neutrophils establish and precisely orient this polarity toward pathogens remains unclear. Here we report that in resting neutrophils, the ERM (ezrin, radixin, and moesin) protein moesin in its active form (phosphorylated and membrane bound) prevented cell polarization by inhibiting the small GTPases Rac, Rho, and Cdc42. Attractant-induced activation of myosin phosphatase deactivated moesin at the prospective leading edge to break symmetry and establish polarity. Subsequent translocation of moesin to the trailing edge confined the formation of a prominent pseudopod directed toward pathogens and prevented secondary pseudopod formation in other directions. Therefore, both moesin-mediated inhibition and its localized deactivation by myosin phosphatase are essential for neutrophil polarization and effective neutrophil tracking of pathogens.
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HÖFER, T., P. K. MAINI, J. A. SHERRATT, M. A. J. CHAPLAIN, and J. D. MURRAY. "RESOLVING THE CHEMOTACTIC WAVE PARADOX: A MATHEMATICAL MODEL FOR CHEMOTAXIS OF DICTYOSTELIUM AMOEBAE." Journal of Biological Systems 03, no. 04 (1995): 967–73. http://dx.doi.org/10.1142/s0218339095000861.
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The slime mould Dictyostelium discoideum is a widely studied paradigm for biological pattern formation. To provide an explanation for the apparently paradoxical behaviour of Dictyostelium amoebae in the symmetric chemoattractant waves which govern their aggregation, we extend the standard model for chemotaxis of a cell population by explicitly considering adaptation of the chemotactic signalling pathway. In the limiting cases of very fast and very slow adaptation kinetics the model equations reduce to the standard model which predicts cell movement opposite to the observed direction. Adaptation on an intermediate timescale, however, provides cells with a "short-term memory" of experienced chemoattractant concentrations which can fully account for the experimental observation of cell translocation opposite to the direction of propagation of the chemoattractant waves.
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Anderson, K. I., Y. L. Wang, and J. V. Small. "Coordination of protrusion and translocation of the keratocyte involves rolling of the cell body." Journal of Cell Biology 134, no. 5 (1996): 1209–18. http://dx.doi.org/10.1083/jcb.134.5.1209.
Full textAbstract:
We have investigated the relationship between lamellipodium protrusion and forward translocation of the cell body in the rapidly moving keratocyte. It is first shown that the trailing, ellipsoidal cell body rotates during translocation. This was indicated by the rotation of the nucleus and the movement of cytoplasmic organelles, as well as of exogenously added beads used as markers. Activated or Con A-coated fluorescent beads that were overrun by cells were commonly endocytosed and rotated with the internal organelles. Alternatively, beads applied to the rear of the cell body via a micropipette adhered to the dorsal cell surface and also moved forward, indicating that both exterior and underlying cortical elements participated in rotation. Manipulation of keratocytes with microneedles demonstrated that pushing or restraining the cell body in the direction of locomotion, and squeezing it against the substrate, which temporarily increased the intracellular pressure, did not effect the rate of lamellipodium protrusion. Rotation and translocation of the cell body continued momentarily after arrest of lamellipodium protrusion by cytochalasin B, indicating that these processes were not directly dependent on actin polymerization. The cell body was commonly flanked by phase-dense "axles," extending from the cell body into the lamellipodium. Phalloidin staining showed these to be comprised of actin bundles that splayed forward into the flanks of the lamellipodium. Disruption of the bundles on one side of the nucleus by traumatic microinjection resulted in rapid retraction of the cell body in the opposite direction, indicating that the cell body was under lateral contractile stress. Myosin II, which colocalizes with the actin bundles, presumably provides the basis of tension generation across and traction of the cell body. We propose that the basis of coupling between lamellipodium protrusion and translocation of the cell body is a flow of actin filaments from the front, where they are nucleated and engage in protrusion, to the rear, where they collaborate with myosin in contraction. Myosin-dependent force is presumably transmitted from the ends of the cell body into the flanks of the lamellipodium via the actin bundles. This force induces the spindle-shaped cell body to roll between the axles that are created continuously from filaments supplied by the advancing lamellipodium.
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Lee, E. A., E. H. Coe, and L. L. Darrah. "Genetic variation in dosage effects in maize aneuploids." Genome 39, no. 4 (1996): 711–21. http://dx.doi.org/10.1139/g96-090.
Full textAbstract:
In maize (Zea mays L.), the consequences of aneuploidy have been well documented, however, genetic variation in the responses to aneuploidy has not been examined. Using simple B–A translocation stocks to generate a dosage series involving segments from 14 chromosome arms, we tested for the presence of genetic variation for dosage responses in maize by examining reciprocal and maternal genotype effects on the dosage responses. Reciprocal effects examined whether there were differences between two distinctly different inbred backgrounds, Mo17Ht and B73Ht, in how they responded to loss or gain of a B73Ht segment in the Mo17Ht × B73Ht (TB) F1 cross versus a Mo17Ht segment in the B73Ht × Mo17Ht (TB) F1 cross. Maternal genotype effects questioned whether different inbred backgrounds, Sc41R, T8, and either Mo17Ht or B73Ht (depending on the male), when used as females responded differently to the loss or gain of a chromosome arm segment from the same male (either B73Ht TB or Mo17Ht TB) in an F1 cross. Numerous examples of reciprocal and maternal genetic effects were identified in this study. Most of the genetic effects were due to differences in magnitude of response rather than direction; however, tassel-branch number involving the 5S chromosome segment in the B73Ht male background and the 7L chromosome segment in the Mo17Ht male background showed a trend toward the maternal genotype effects being due to differences in the direction of the response. Key words : quantitative traits, corn, B–A translocations, dosage analysis.
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Guttman, J. A., G. H. Kimel, and A. W. Vogl. "Dynein and plus-end microtubule-dependent motors are associated with specialized Sertoli cell junction plaques (ectoplasmic specializations)." Journal of Cell Science 113, no. 12 (2000): 2167–76. http://dx.doi.org/10.1242/jcs.113.12.2167.
Full textAbstract:
The mechanism responsible for spermatid translocation in the mammalian seminiferous epithelium was proposed to be the microtubule-based transport of specialized junction plaques (ectoplasmic specializations) that occur in Sertoli cell regions attached to spermatid heads. These plaques each consist of a cistern of endoplasmic reticulum, a layer of actin filaments and the adjacent plasma membrane. It is predicted that motor proteins function to move the junction plaques, and hence the attached spermatids, first towards the base and then back to the apex of the epithelium, along microtubules. If this hypothesis is true, motor proteins should be associated with the cytoplasmic face of the endoplasmic reticulum component of ectoplasmic specializations. In addition, isolated junction plaques should support microtubule movement both in the plus and minus directions to account for the bidirectional translocation of spermatids in vivo. To determine if cytoplasmic dynein is localized to the endoplasmic reticulum of the plaques, perfusion-fixed rat testes were immunologically probed, at the ultrastructural level, for the intermediate chain of cytoplasmic dynein (IC74). In addition, testicular fractions enriched for spermatid/junction complexes were incubated with and without gelsolin, centrifuged and the supernatants compared, by western blot analysis, for Glucose Regulated Protein 94 (a marker for endoplasmic reticulum) and IC74. At the ultrastructural level, the probe for IC74 clearly labelled material associated with the cytoplasmic face of the endoplasmic reticulum component of the junction plaques. In the gelsolin experiments, both probes reacted more strongly with appropriate bands from the gelsolin-treated supernatants than with corresponding bands from controls. To determine if the junction plaques support microtubule transport in both directions, polarity-labelled microtubules were bound to isolated spermatid/junction complexes and then assessed for motility in the presence of ATP and testicular cytosol (2 mg/ml). Of 25 recorded motility events, 17 were in a direction consistent with a plus-end directed motor being present, and 8 were in the minus-end direction. The results are consistent with the conclusion that the junction plaques have the potential for moving along microtubules in both the plus and minus directions and that both a kinesin-type and a dynein-type motor may be associated with the junction plaques. The data also indicate that cytoplasmic dynein is localized to the cytoplasmic face of the endoplasmic reticulum component of the plaques.
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Berezhkovskii, Alexander M., and Sergey M. Bezrukov. "Site model for channel-facilitated membrane transport: invariance of the translocation time distribution with respect to direction of passage." Journal of Physics: Condensed Matter 19, no. 6 (2007): 065148. http://dx.doi.org/10.1088/0953-8984/19/6/065148.
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Mayeux, Herman S., and Hyrum B. Johnson. "Absorption and Translocation of Picloram by Lindheimer Pricklypear (Opuntia lindheimeri)." Weed Science 37, no. 2 (1989): 161–66. http://dx.doi.org/10.1017/s0043174500071721.
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Removing the epicuticular wax from mature pads (cladophylls) of Lindheimer pricklypear increased picloram absorption by four- to sixfold in the laboratory, while the addition of surfactant had little effect on absorption. Absorption decreased with increasing pH of the picloram solution, indicating that picloram diffused through the cuticle as the undissociated molecule. Picloram entered detached pads at the areoles more readily than through the surrounding cuticle. In the glasshouse, whole plants consisting of an old, mature pad supporting a young, growing pad absorbed picloram very slowly whether picloam was applied as a spray to old or young pads or to the soil. About 90 and 80% of the applied picloram remained on the waxy surface of old and new pads, respectively, and about 2% of the applied picloram was recovered from within the epicuticular wax after 30 days. Picloram concentrations within pads treated in the glasshouse were greater when the herbicide was applied to new pads (4.6 μg/g) than old pads (1.9 μg/g) after 30 days. More picloram was translocated basipetally from treated new pads to untreated old pads than in the opposite direction, but concentrations in untreated pads were low (<1 μg/g). Little picloram was absorbed by roots, compared to pads, and little was translocated into or out of roots. These results conflict with the view that the effectiveness of picloram for pricklypear control is attributable to extensive root uptake and acropetal transport. However, observations of plants 6 months after treatment indicated that soil applications were more effective than sprays in the glasshouse.
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Taki, Tomohiko, Noriko Shibuya, Masafumi Taniwaki, et al. "ABI-1, a Human Homolog to Mouse Abl-Interactor 1, Fuses theMLL Gene in Acute Myeloid Leukemia With t(10;11)(p11.2;q23)." Blood 92, no. 4 (1998): 1125–30. http://dx.doi.org/10.1182/blood.v92.4.1125.
Full textAbstract:
Abstract Recurrent translocation t(10;11) has been reported to be associated with acute myeloid leukemia (AML). Recently, two types of chimeric transcripts, MLL-AF10 in t(10;11)(p12;q23) andCALM-AF10 in t(10;11)(p13;q14), were isolated. t(10;11) is strongly associated with complex translocations, including invins(10;11) and inv(11)t(10;11), because the direction of transcription of AF10 is telomere to centromere. We analyzed a patient of AML with t(10;11)(p11.2;q23) and identified ABI-1 on chromosome 10p11.2, a human homolog to mouse Abl-interactor 1 (Abi-1), fused with MLL. Whereas the ABI-1 gene bears no homology with the partner genes of MLL previously described, the ABI-1 protein exhibits sequence similarity to protein of homeotic genes, contains several polyproline stretches, and includes asrc homology 3 (SH3) domain at the C-terminus that is required for binding to Abl proteins in mouse Abi-1 protein. Recently, e3B1, an eps8 SH3 binding protein 1, was also isolated as a human homolog to mouse Abi-1. Three types of transcripts of ABI-1 gene were expressed in normal peripheral blood. Although e3B1 was considered to be a full-length ABI-1, the MLL-ABI-1fusion transcript in this patient was formed by an alternatively spliced ABI-1. Others have shown that mouse Abi-1 suppresses v-ABL transforming activity and that e3B1, full-length ABI-1, regulates cell growth. In-frame MLL-ABI-1 fusion transcripts combine the MLL AT-hook motifs and DNA methyltransferase homology region with the homeodomain homologous region, polyproline stretches, and SH3 domain of alternatively spliced transcript of ABI-1. Our results suggest that the ABI-1 gene plays a role in leukemogenesis by translocating to MLL. © 1998 by The American Society of Hematology.
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Taki, Tomohiko, Noriko Shibuya, Masafumi Taniwaki, et al. "ABI-1, a Human Homolog to Mouse Abl-Interactor 1, Fuses theMLL Gene in Acute Myeloid Leukemia With t(10;11)(p11.2;q23)." Blood 92, no. 4 (1998): 1125–30. http://dx.doi.org/10.1182/blood.v92.4.1125.416k40_1125_1130.
Full textAbstract:
Recurrent translocation t(10;11) has been reported to be associated with acute myeloid leukemia (AML). Recently, two types of chimeric transcripts, MLL-AF10 in t(10;11)(p12;q23) andCALM-AF10 in t(10;11)(p13;q14), were isolated. t(10;11) is strongly associated with complex translocations, including invins(10;11) and inv(11)t(10;11), because the direction of transcription of AF10 is telomere to centromere. We analyzed a patient of AML with t(10;11)(p11.2;q23) and identified ABI-1 on chromosome 10p11.2, a human homolog to mouse Abl-interactor 1 (Abi-1), fused with MLL. Whereas the ABI-1 gene bears no homology with the partner genes of MLL previously described, the ABI-1 protein exhibits sequence similarity to protein of homeotic genes, contains several polyproline stretches, and includes asrc homology 3 (SH3) domain at the C-terminus that is required for binding to Abl proteins in mouse Abi-1 protein. Recently, e3B1, an eps8 SH3 binding protein 1, was also isolated as a human homolog to mouse Abi-1. Three types of transcripts of ABI-1 gene were expressed in normal peripheral blood. Although e3B1 was considered to be a full-length ABI-1, the MLL-ABI-1fusion transcript in this patient was formed by an alternatively spliced ABI-1. Others have shown that mouse Abi-1 suppresses v-ABL transforming activity and that e3B1, full-length ABI-1, regulates cell growth. In-frame MLL-ABI-1 fusion transcripts combine the MLL AT-hook motifs and DNA methyltransferase homology region with the homeodomain homologous region, polyproline stretches, and SH3 domain of alternatively spliced transcript of ABI-1. Our results suggest that the ABI-1 gene plays a role in leukemogenesis by translocating to MLL. © 1998 by The American Society of Hematology.
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Adorante, J. S., and P. M. Cala. "Activation of electroneutral K flux in Amphiuma red blood cells by N-ethylmaleimide. Distinction between K/H exchange and KCl cotransport." Journal of General Physiology 90, no. 2 (1987): 209–27. http://dx.doi.org/10.1085/jgp.90.2.209.
Full textAbstract:
Exposure of Amphiuma red blood cells to millimolar concentrations of N-ethylmaleimide (NEM) resulted in net K loss. In order to determine whether net K loss was conductive or was by electroneutral K/H exchange or KCl cotransport, studies were performed evaluating K flux in terms of the thermodynamic forces to which K flux by the above pathways should couple. The direction and magnitude of the NEM-induced net K flux did not correspond with the direction and magnitude of the forces relevant to K conductance or electroneutral KCl cotransport. Both the magnitude and direction of the NEM-activated K flux responded to the driving force for K/H exchange. We therefore conclude that NEM-induced K loss, like that by osmotically swollen Amphiuma red blood cells, is by an electroneutral K/H exchanger. In addition to the above studies, we evaluated the kinetic behavior of the volume- and NEM-induced K/H exchange flux pathways in media where Cl was replaced by SCN, NO3, para-aminohippurate (PAH), or gluconate. The anion replacement studies did not permit a distinction between K/H exchange and KCl cotransport, since, depending upon the anion used as a Cl replacement, partial inhibition or stimulation of volume-activated K/H exchange fluxes was observed. In contrast, all anions used were stimulatory to the NEM-induced K loss. Since, on the basis of force-flow analysis, both volume-and NEM-induced K loss are K/H exchange, it was necessary to reevaluate assumptions (i.e., anions serve as substrates and therefore probe the translocation step) associated with the use of anion replacement as a means of flux route identification. When viewed together with the force-flow studies, the Cl replacement studies suggest that anion effects upon K/H exchange are indirect. The different anions appear to alter mechanisms that couple NEM exposure and cell swelling to the activation of K/H exchange, as opposed to exerting direct effects upon K and H translocation.
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Hepp, Christof, and Berenike Maier. "Kinetics of DNA uptake during transformation provide evidence for a translocation ratchet mechanism." Proceedings of the National Academy of Sciences 113, no. 44 (2016): 12467–72. http://dx.doi.org/10.1073/pnas.1608110113.
Full textAbstract:
Horizontal gene transfer can speed up adaptive evolution and support chromosomal DNA repair. A particularly widespread mechanism of gene transfer is transformation. The initial step to transformation, namely the uptake of DNA from the environment, is supported by the type IV pilus system in most species. However, the molecular mechanism of DNA uptake remains elusive. Here, we used single-molecule techniques for characterizing the force-dependent velocity of DNA uptake by Neisseria gonorrhoeae. We found that the DNA uptake velocity depends on the concentration of the periplasmic DNA-binding protein ComE, indicating that ComE is directly involved in the uptake process. The velocity–force relation of DNA uptake is in very good agreement with a translocation ratchet model where binding of chaperones in the periplasm biases DNA diffusion through a membrane pore in the direction of uptake. The model yields a speed of DNA uptake of 900 bp⋅s−1 and a reversal force of 17 pN. Moreover, by comparing the velocity–force relation of DNA uptake and type IV pilus retraction, we can exclude pilus retraction as a mechanism for DNA uptake. In conclusion, our data strongly support the model of a translocation ratchet with ComE acting as a ratcheting chaperone.
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Levy, Julien, Aravind Ravindran, Dennis Gross, Cecilia Tamborindeguy, and Elizabeth Pierson. "Translocation of ‘Candidatus Liberibacter solanacearum’, the Zebra Chip Pathogen, in Potato and Tomato." Phytopathology® 101, no. 11 (2011): 1285–91. http://dx.doi.org/10.1094/phyto-04-11-0121.
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Zebra Chip disease is a serious threat to potato production. The pathogen, the phloem-limited bacterium ‘Candidatus Liberibacter solanacearum,’ is vectored by the potato and tomato psyllid Bactericerca cockerelli to potato and tomato. Patterns of pathogen translocation through phloem in potato and tomato plants were examined to determine whether rate or direction of translocation vary by host species or potato cultivars. Two insects were given a 7-day inoculation access period on a single leaf. Weekly, leaves from upper-, middle-, and lower-tier branches were tested for the presence of ‘Ca. L. solanacearum’ by polymerase chain reaction (PCR). In tomato and potato, ‘Ca. L. solanacearum’ was detected 2 to 3 weeks after infestation, most frequently in upper- and middle-tier leaves. In potato, the pathogen was detected in leaves on a second, noninfested stem when the stems remained joined via the tuber. Although rates of pathogen movement were similar among potato cultivars, symptoms developed earlier in more susceptible cultivars. Quantitative PCR indicated that bacterial titers were frequently low in tomato and potato samples (<20 genome units per nanogram of DNA). Results establish that, for improved detection, samples should include newly developing leaves and consider that, under low insect pressure, the pathogen may be undetectable by PCR until 3 weeks after infestation.
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FOUCHER, GUY, PATRICK LORÉA, STEVEN HOVIUS, GIORGIO PIVATO, and JOSE MEDINA. "Radial Shift of the Ulnar Fingers: A New Technique for Special Cases of Longitudinal Central Deficiency." Journal of Hand Surgery 31, no. 2 (2006): 156–61. http://dx.doi.org/10.1016/j.jhsb.2005.12.003.
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Treatment of central longitudinal deficiencies is well defined, with different techniques established for the classical clefts. However, none of these techniques is easily applied to the treatment of very deep clefts accompanied by a significant divergence of the metacarpal bones. In such cases, the results of current techniques are disappointing. We propose a new technique of “Translocation in the Radial direction of the Ulnar Finger(s)” (TRUF) by intra-carpal osteotomy. The results are illustrated in three clinical cases. The TRUF operation allowed closing of the cleft, alignment of the metacarpal bones and preservation of carpometacarpal mobility. When necessary, a metacarpal synostosis may be treated at the same procedure.
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Hortsch, M., D. Avossa, and D. I. Meyer. "Characterization of secretory protein translocation: ribosome-membrane interaction in endoplasmic reticulum." Journal of Cell Biology 103, no. 1 (1986): 241–53. http://dx.doi.org/10.1083/jcb.103.1.241.
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Secretory proteins are synthesized on ribosomes bound to the membrane of the endoplasmic reticulum (ER). After the selection of polysomes synthesizing secretory proteins and their direction to the membrane of the ER via signal recognition particle (SRP) and docking protein respectively, the polysomes become bound to the ER membrane via an unknown, protein-mediated mechanism. To identify proteins involved in protein translocation, beyond the (SRP-docking protein-mediated) recognition step, controlled proteolysis was used to functionally inactivate rough microsomes that had previously been depleted of docking protein. As the membranes were treated with increasing levels of protease, they lost their ability to be functionally reconstituted with the active cytoplasmic fragment of docking protein (DPf). This functional inactivation did not correlate with a loss of either signal peptidase activity, nor with the ability of the DPf to reassociate with the membrane. It did correlate, however, with a loss of the ability of the microsomes to bind ribosomes. Ribophorins are putative ribosome-binding proteins. Immunoblots developed with monoclonal antibodies against canine ribophorins I and II demonstrated that no correlation exists between the protease-induced inability to bind ribosomes and the integrity of the ribophorins. Ribophorin I was 85% resistant and ribophorin II 100% resistant to the levels of protease needed to totally eliminate ribosome binding. Moreover, no direct association was found between ribophorins and ribosomes; upon detergent solubilization at low salt concentrations, ribophorins could be sedimented in the presence or absence of ribosomes. Finally, the alkylating agent N-ethylmaleimide was shown to be capable of inhibiting translocation (beyond the SRP-docking protein-mediated recognition step), but had no affect on the ability of ribosomes to bind to ER membranes. We conclude that potentially two additional proteinaceous components, as yet unidentified, are involved in protein translocation. One is protease sensitive and possibly involved in ribosome binding, the other is N-ethylmaleimide sensitive and of unknown function.
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Hurley, Bryan P., Cheleste M. Thorpe, and David W. K. Acheson. "Shiga Toxin Translocation across Intestinal Epithelial Cells Is Enhanced by Neutrophil Transmigration." Infection and Immunity 69, no. 10 (2001): 6148–55. http://dx.doi.org/10.1128/iai.69.10.6148-6155.2001.
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ABSTRACT Shiga toxin-producing E. coli (STEC) is a food-borne pathogen that causes serious illness, including hemolytic-uremic syndrome (HUS). STEC colonizes the lower intestine and produces Shiga toxins (Stxs). Stxs appear to translocate across intestinal epithelia and affect sensitive endothelial cell beds at various sites. We have previously shown that Stxs cross polarized intestinal epithelial cells (IECs) via a transcellular route and remain biologically active. Since acute inflammatory infiltration of the gut and fecal leukocytes is seen in many STEC-infected patients and since polymorphonuclear leukocyte (PMN) transmigration across polarized IECs diminishes the IEC barrier function in vitro, we hypothesized that PMN transmigration may enhance Stx movement across IECs. We found that basolateral-to-apical transmigration of neutrophils significantly increased the movement of Stx1 and Stx2 across polarized T84 IECs in the opposite direction. The amount of Stx crossing the T84 barrier was proportional to the degree of neutrophil transmigration, and the increase in Stx translocation appears to be due to increases in paracellular permeability caused by migrating PMNs. STEC clinical isolates applied apically induced PMN transmigration across and interleukin-8 (IL-8) secretion from T84 cells. Of the 10 STEC strains tested, three STEC strains lackingeae and espB (eae- andespB-negative STEC strains) induced significantly more neutrophil transmigration and significantly greater IL-8 secretion thaneae- and espB-positive STEC or enteropathogenic E. coli. This study suggests that STEC interaction with intestinal epithelia induces neutrophil recruitment to the intestinal lumen, resulting in neutrophil extravasation across IECs, and that during this process Stxs may pass in greater amounts into underlying tissues, thereby increasing the risk of HUS.
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Ye, Jin. "Transcription factors activated through RIP (regulated intramembrane proteolysis) and RAT (regulated alternative translocation)." Journal of Biological Chemistry 295, no. 30 (2020): 10271–80. http://dx.doi.org/10.1074/jbc.rev120.012669.
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Transmembrane proteins are membrane-anchored proteins whose topologies are important for their functions. These properties enable regulation of certain transmembrane proteins by regulated intramembrane proteolysis (RIP) and regulated alternative translocation (RAT). RIP enables a protein fragment of a transmembrane precursor to function at a new location, and RAT leads to an inverted topology of a transmembrane protein by altering the direction of its translocation across membranes during translation. RIP mediated by site-1 protease (S1P) and site-2 protease (S2P) is involved in proteolytic activation of membrane-bound transcription factors. In resting cells, these transcription factors remain in the endoplasmic reticulum (ER) as inactive transmembrane precursors. Upon stimulation by signals within the ER, they are translocated from the ER to the Golgi. There, they are cleaved first by S1P and then by S2P, liberating their N-terminal domains from membranes and enabling them to activate genes in the nucleus. This signaling pathway regulates lipid metabolism, unfolded protein responses, secretion of extracellular matrix proteins, and cell proliferation. Remarkably, ceramide-induced RIP of cAMP response element–binding protein 3–like 1 (CREB3L1) also involves RAT. In resting cells, RIP of CREB3L1 is blocked by transmembrane 4 L6 family member 20 (TM4SF20). Ceramide inverts the orientation of newly synthesized TM4SF20 in membranes through RAT, converting TM4SF20 from an inhibitor to an activator of RIP of CREB3L1. Here, I review recent insights into RIP of membrane-bound transcription factors, focusing on CREB3L1 activation through both RIP and RAT, and discuss current open questions about these two signaling pathways.
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Tlalka, Monika, Mark Fricker та Sarah Watkinson. "Imaging of Long-Distance α-Aminoisobutyric Acid Translocation Dynamics during Resource Capture by Serpula lacrymans". Applied and Environmental Microbiology 74, № 9 (2008): 2700–2708. http://dx.doi.org/10.1128/aem.02765-07.
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ABSTRACT α-Aminoisobutyric acid (AIB) is a nonmetabolized amino acid analogue of alanine, which at low (μM) concentrations acts as a tracer for amino acid movements. At high concentrations (mM), it competitively inhibits membrane transport and metabolism of protein amino acids and acts as a systemic translocated inhibitor of mycelial extension in fungi. AIB can control mycelial spread of the basidiomycete Serpula lacrymans, the cause of brown rot of wood in buildings. However, it is not known how effectively the inhibitor is distributed throughout the mycelium. Realistically heterogeneous microcosms, in which the fungus grew across nutritionally inert sand to colonize discrete wood resources, were used to investigate patterns of inhibition and translocation following local application of AIB. At a 0.1 M concentration, locally applied AIB caused immediate arrest of extension throughout the whole mycelium, maintained for a 6-week experimental period. The dynamics of translocation of subtoxic amounts of [1-14C]AIB ([14C]AIB) were mapped by photon-counting scintillation imaging in conjunction with destructive harvest to establish the velocity, direction, and rate of translocation and the extent of [14C]AIB reallocation accompanying the invasion of fresh wood. Locally applied [14C]AIB was distributed throughout complex mycelial networks within 2 h of application, becoming localized in growing margins by 12 h. Encounter with a fresh wood resource triggered a widespread response, causing withdrawal of [14C]AIB from throughout the network, accompanied by accumulation in the newly colonized wood and associated mycelium. The results are discussed in the context of nutrient dynamics in wood decomposer fungi and the mechanism of the amino acid reallocation response.
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Ross, Mary H. "Cytological studies of Blattella germanica and Blattella asahinai. I. A possible genetic basis of interspecific divergence." Genome 30, no. 5 (1988): 812–19. http://dx.doi.org/10.1139/g88-131.
Full textAbstract:
The position of the nucleolus organizing region (NOR) in Blattella asahinai differs from that in its close relative, Blattella germanica. The number and position of NORs in hybrid males from reciprocal crosses indicate that the NOR carried by the X chromosome of B. germanica corresponds to a small, paired, terminal segment on the longest chromosome (No. 12) in B. asahinai. The segment is not present in B. germanica; hybrids are heterozygous for the segment. Except for these differences and a relatively smaller size of the B. asahinai X chromosome, gross chromosome morphology is essentially identical in the two species and their hybrids. The size of the X and position of the NORs in hybrid males were as expected according to the direction of the cross. The observations are clearly indicative of a nonreciprocal translocation involving the NOR on the X chromosome of B. germanica and those on an autosome of B. asahinai. The shift involved genes fundamental to protein synthesis, i.e., rDNA (identified by association with the nucleoli). Even minor effects on these genes could bring about significant changes in an organism. It is suggested that the translocation may have been the genetic mechanism of interspecific divergence.Key words: cockroach, evolution, nucleolus, NOR chromosomes.
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Lee, Jerry S. H., Melissa I. Chang, Yiider Tseng, and Denis Wirtz. "Cdc42 Mediates Nucleus Movement and MTOC Polarization in Swiss 3T3 Fibroblasts under Mechanical Shear Stress." Molecular Biology of the Cell 16, no. 2 (2005): 871–80. http://dx.doi.org/10.1091/mbc.e03-12-0910.
Full textAbstract:
Nucleus movement is essential during nucleus positioning for tissue growth and development in eukaryotic cells. However, molecular regulators of nucleus movement in interphase fibroblasts have yet to be identified. Here, we report that nuclei of Swiss 3T3 fibroblasts undergo enhanced movement when subjected to shear flows. Such movement includes both rotation and translocation and is dependent on microtubule, not F-actin, structure. Through inactivation of Rho GTPases, well-known mediators of cytoskeleton reorganization, we demonstrate that Cdc42, not RhoA or Rac1, controls the extent of nucleus translocation, and more importantly, of nucleus rotation in the cytoplasm. In addition to generating nuclei movement, we find that shear flows also causes repositioning of the MTOC in the direction of flow. This behavior is also controlled by Cdc42 via the Par6/protein kinase Cζ pathway. These results are the first to establish Cdc42 as a molecular regulator of not only shear-induced MTOC polarization in Swiss 3T3 fibroblasts, but also of shear-induced microtubule-dependent nucleus movement. We propose that the movements of MTOC and nucleus are coupled chemically, because they are both regulated by Cdc42 and dependent on microtubule structure, and physically, possibly via Hook/SUN family homologues similar to those found in Caenorhabditis elegans.
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Alcalde, J., P. Bonay, A. Roa, S. Vilaro, and I. V. Sandoval. "Assembly and disassembly of the Golgi complex: two processes arranged in a cis-trans direction." Journal of Cell Biology 116, no. 1 (1992): 69–83. http://dx.doi.org/10.1083/jcb.116.1.69.
Full textAbstract:
We have studied the disassembly and assembly of two morphologically and functionally distinct parts of the Golgi complex, the cis/middle and trans cisterna/trans network compartments. For this purpose we have followed the redistribution of three cis/middle- (GMPc-1, GMPc-2, MG 160) and two trans- (GMPt-1 and GMPt-2) Golgi membrane proteins during and after treatment of normal rat kidney (NRK) cells with brefeldin A (BFA). BFA induced complete disassembly of the cis/middle- and trans-Golgi complex and translocation of GMPc and GMPt to the ER. Cells treated for short times (3 min) with BFA showed extensive disorganization of both cis/middle- and trans-Golgi complexes. However, complete disorganization of the trans part required much longer incubations with the drug. Upon removal of BFA the Golgi complex was reassembled by a process consisting of three steps: (a) exist of cis/middle proteins from the ER and their accumulation into vesicular structures scattered throughout the cytoplasm; (b) gradual relocation and accumulation of the trans proteins in the vesicles containing the cis/middle proteins; and (c) assembly of the cisternae, and reconstruction of the Golgi complex within an area located in the vicinity of the centrosome from which the ER was excluded. Reconstruction of the cis/middle-Golgi complex occurred under temperature conditions inhibitory of the reorganization of the trans-Golgi complex, and was dependent on microtubules. Reconstruction of the trans-Golgi complex, disrupted with nocodazole after selective fusion of the cis/middle-Golgi complex with the ER, occurred after the release of cis/middle-Golgi proteins from the ER and the assembly of the cis/middle cisternae.
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Chen, Lingfeng, Chris Janetopoulos, Yi Elaine Huang, Miho Iijima, Jane Borleis, and Peter N. Devreotes. "Two Phases of Actin Polymerization Display Different Dependencies on PI(3,4,5)P3 Accumulation and Have Unique Roles during Chemotaxis." Molecular Biology of the Cell 14, no. 12 (2003): 5028–37. http://dx.doi.org/10.1091/mbc.e03-05-0339.
Full textAbstract:
The directional movement of cells in chemoattractant gradients requires sophisticated control of the actin cytoskeleton. Uniform exposure of Dictyostelium discoideum amoebae as well as mammalian leukocytes to chemoattractant triggers two phases of actin polymerization. In the initial rapid phase, motility stops and the cell rounds up. During the second slow phase, pseudopodia are extended from local regions of the cell perimeter. These responses are highly correlated with temporal and spatial accumulations of PI(3,4,5)P3/PI(3,4)P2 reflected by the translocation of specific PH domains to the membrane. The slower phase of PI accumulation and actin polymerization is more prominent in less differentiated, unpolarized cells, is selectively increased by disruption of PTEN, and is relatively more sensitive to perturbations of PI3K. Optimal levels of the second responses allow the cell to respond rapidly to switches in gradient direction by extending lateral pseudopods. Consequently, PI3K inhibitors impair chemotaxis in wild-type cells but partially restore polarity and chemotactic response in pten- cells. Surprisingly, the fast phase of PI(3,4,5)P3 accumulation and actin polymerization, which is relatively resistant to PI3K inhibition, can support inefficient but reasonably accurate chemotaxis.
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Fleig, R., and K. Sander. "Honeybee morphogenesis: embryonic cell movements that shape the larval body." Development 103, no. 3 (1988): 525–34. http://dx.doi.org/10.1242/dev.103.3.525.
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Crucial steps in honeybee morphogenesis are characterized by the migration of free epithelial edges while well-defined epithelial cell populations expand or translocate. For each step - dorsal strip invasion, gastrulation, formation of serosa, amnion and midgut - scanning electron microscopy reveals a highly specific syndrome of cell shapes and cell movements at the advancing epithelial edge. Epithelial translocation appears to result from various combinations of ameboid movement, cell flattening, cell rearrangement (intercalation) and cell contraction along the free epithelial edge. The direction of epithelial movements could result essentially from the initial shape and orientation of the edge combined with the cells' tendency to close vacant spaces by extension and migration. These findings are discussed in relation to morphogenetic movements in other insects and to postembryonic wound healing in insects and amphibians.
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Partelová, Denisa, Klára Kuglerová, Yevheniia Konotop, et al. "Imaging of photoassimilates transport in plant tissues by positron emission tomography." Nova Biotechnologica et Chimica 16, no. 1 (2017): 32–41. http://dx.doi.org/10.1515/nbec-2017-0005.
Full textAbstract:
AbstractThe current findings show that positron emission tomography (PET), primarily developed for medical diagnostic imaging, can be applied in plant studies to analyze the transport and allocation of wide range of compounds labelled with positronemitting radioisotopes. This work is focused on PET analysis of the uptake and transport of 2-deoxy-2-fluoro[18F]-D-glucose (2-[18F]FDG), as a model of photoassimilates, in tissues of giant reed (Arundo donax L. var. versicolor) as a potential energy crop. The absorption of 2-[18F]FDG and its subsequent transport in plant tissues were evaluated in both acropetal and basipetal direction as well. Visualization and quantification of the uptake and transport of 2-[18F]FDG in plants immersed with the root system into a 2-[18F]FDG solution revealed a significant accumulation of 18F radioactivity in the roots. The transport rate in plants was increased in the order of plant exposure through: stem > mechanically damaged root system > intact root system. PET analysis in basipetal direction, when the plant was immersed into the 2-[18F]FDG solution with the cut area of the leaf of whole plant, showed minimal translocation of 2-[18F]FDG into the other plant parts. The PET results were verified by measuring the accumulated radioactivity of18F by direct gamma-spectrometry.
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Salmon, E. D., R. A. Walker, E. T. O'Brien, N. K. Pryer, W. A. Voter, and H. P. Erickson. "Visualization of the polymerization dynamics of individual 25nm-diameter microtubules in real time." Proceedings, annual meeting, Electron Microscopy Society of America 45 (August 1987): 636–37. http://dx.doi.org/10.1017/s042482010012761x.
Full textAbstract:
Microtubules (Mts) of the interphase cytoplasmic Mt complex (CMTC) and the mitotic spindle are dynamic polymers assembled from a cellular pool of tubulin by end-dependent association-dissociation reactions (1,2). Mts have an intrinsic structural polarity, which orients the direction of cell motility. Mts also play a major role in the active translocation of vesicles and chromosomes. Quantitative fluorescence microscopy studies using fluorescently labeled tubulin microinjected into living cells have shown that the great majority of Mts in the CMTC and the spindle exchange rapidly with tubulins in the cellular pool (2,3). Dynamic instability, as proposed by Mitchison and Kirschner, provides the best explanation for this rapid turnover of microtubules (1,2).Three major temporal phases of Mt polymerization and three major abrupt transitions between these phases characterize the dynamic instability behavior of pure tubulin (Fig. 1).
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Nodelman, Ilana M., Zhongtian Shen, Robert F. Levendosky, and Gregory D. Bowman. "Autoinhibitory elements of the Chd1 remodeler block initiation of twist defects by destabilizing the ATPase motor on the nucleosome." Proceedings of the National Academy of Sciences 118, no. 4 (2021): e2014498118. http://dx.doi.org/10.1073/pnas.2014498118.
Full textAbstract:
Chromatin remodelers are ATP (adenosine triphosphate)-powered motors that reposition nucleosomes throughout eukaryotic chromosomes. Remodelers possess autoinhibitory elements that control the direction of nucleosome sliding, but underlying mechanisms of inhibition have been unclear. Here, we show that autoinhibitory elements of the yeast Chd1 remodeler block nucleosome sliding by preventing initiation of twist defects. We show that two autoinhibitory elements—the chromodomains and bridge—reinforce each other to block sliding when the DNA-binding domain is not bound to entry-side DNA. Our data support a model where the chromodomains and bridge target nucleotide-free and ADP-bound states of the ATPase motor, favoring a partially disengaged state of the ATPase motor on the nucleosome. By bypassing distortions of nucleosomal DNA prior to ATP binding, we propose that autoinhibitory elements uncouple the ATP binding/hydrolysis cycle from DNA translocation around the histone core.
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Miserocchi, G., D. Venturoli, D. Negrini, M. C. Gilardi, and R. Bellina. "Intrapleural fluid movements described by a porous flow model." Journal of Applied Physiology 73, no. 6 (1992): 2511–16. http://dx.doi.org/10.1152/jappl.1992.73.6.2511.
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We injected technetium-labeled albumin (at a concentration similar to that of the pleural fluid) in the costal region of anesthetized dogs (n = 13) either breathing spontaneously or apneic. The decay rate of labeled activity at the injection site was studied with a gamma camera placed either in the anteroposterior (AP) or laterolateral (LL) projection. In breathing animals (respiratory frequency approximately 10 cycles/min), 10 min after the injection the activity decreased by approximately 50% on AP and approximately 20% on LL imaging; in apneic animals the corresponding decrease in activity was reduced to approximately 15 and approximately 3%, respectively. We considered label translocation from AP and LL imaging as a result of bulk flows of liquid along the costomediastinal and gravity-dependent direction, respectively. We related intrapleural flows to the hydraulic pressure gradients existing along these two directions and to the geometry of the pleural space. The pleural space was considered as a porous medium partially occupied by the mesh of microvilli protruding from mesothelial cells. Solution of the Kozeny-Carman equation for the observed flow velocities and pressure gradients yielded a mean hydraulic radius of the pathways followed by the liquid ranging from 2 to 4 microns. The hydraulic resistivity of the pleural space was estimated at approximately 8.5 x 10(5) dyn.s.cm-4, five orders of magnitude lower than that of interstitial tissue.
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Li, Shuang, Yihu Yang, and Weikai Li. "Human ferroportin mediates proton-coupled active transport of iron." Blood Advances 4, no. 19 (2020): 4758–68. http://dx.doi.org/10.1182/bloodadvances.2020001864.
Full textAbstract:
Abstract As the sole iron exporter in humans, ferroportin controls systemic iron homeostasis through exporting iron into the blood plasma. The molecular mechanism of how ferroportin exports iron under various physiological settings remains unclear. Here we found that purified ferroportin incorporated into liposomes preferentially transports Fe2+ and exhibits lower affinities of transporting other divalent metal ions. The iron transport by ferroportin is facilitated by downhill proton gradients at the same direction. Human ferroportin is also capable of transporting protons, and this activity is tightly coupled to the iron transport. Remarkably, ferroportin can conduct active transport uphill against the iron gradient, with favorable charge potential providing the driving force. Targeted mutagenesis suggests that the iron translocation site is located at the pore region of human ferroportin. Together, our studies enhance the mechanistic understanding by which human ferroportin transports iron and suggest that a combination of electrochemical gradients regulates iron export.