The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Charles J. Brokaw - One of the best experts on this subject based on the ideXlab platform.
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MICROTUBULE SLIDING, BEND INITIATION, AND BEND PROPAGATION PARAMETERS OF CIONA SPERM FLAGELLA ALTERED BY VISCOUS LOAD
Cell motility and the cytoskeleton, 1996Co-Authors: Charles J. BrokawAbstract:The effect of altered viscous resistance on flagellar bending has been reexamined, utilizing ATP-reactivated sperm flagella from Ciona and newer methods that resolve metachronous and synchronous components of microtubule sliding and allow the examination of bend initiation as well as bend propagation. Large changes in Amplitude and wavelength of bend propagation occur with little change in bend initiation parameters, other than frequency, indicating that bend initiation and bend propagation are regulated by quite different mechanisms. At increased viscosity, Reduced Amplitude of propagating bends, measured as metachronous shear Amplitude, is associated with both Reduced Amplitude during bend initiation and Amplitude adjustment after bends begin to propagate. This combination of effects was seen previously when Reduced Amplitudes were induced by increased salt concentration, and it was suggested to be caused by an imbalance between active moments and viscous resistances. However, in contrast to the results at increased salt concentrations, which involved significant reduction in bend curvature and little reduction in wavelength, increased viscosity causes very little change in curvature and causes a major reduction in wavelength. This difference can be explained by a model of flagellar bending in which inner arm dyneins have primary responsibility for maintaining bend curvature and outer arm dyneins have primary responsibility for performing work against viscous resistances. Both sets of dyneins would be inhibited by increased salt concentration, but increased viscous resistance would be irrelevant to the operation of inner arm dyneins.
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microtubule sliding in Reduced Amplitude bending waves of ciona sperm flagella bending waves attenuated by lithium
Cytoskeleton, 1994Co-Authors: Charles J. BrokawAbstract:The distinct damped, or attenuated, bending pattern observed when demembranated sperm flagella of the tunicate, Ciona, are reactivated in the presence of 2 mM Li+ has been analysed in detail. In these patterns, bends are initiated at the base of the flagellum, but die out after they start to propagate along the flagellum, so that little or no bending is seen in the distal half of the flagellum. A quantitative descriptive analysis shows that the distinctive feature of this attenuation of bending wave Amplitude is an asymmetric interbend decay, or slippage, occuring, on average, only at the transitions between a reverse bend and the preceding principal bend. This attenuation is combined with a significant amount of synchronous sliding in the distal half of the flagellum and a decrease in propagation velocity of transitions between bends in the mid-region of the flagellum. Computer simulations demonstrate that the synchronous sliding in the distal half of these flagella can be an entirely passive consequence of the mechanical interaction between active sliding and bending in the basal third of the flagellum and viscous resistances to movement of the distal region of the flagellum through the fluid environment. The current computer models do not contain a mechanism for asymmetric interbend decay that can reproduce these attenuated bending patterns. © 1994 Wiley-Liss, Inc.
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Microtubule sliding in Reduced‐Amplitude bending waves of Ciona sperm flagella: Bending waves attenuated by lithium
Cell motility and the cytoskeleton, 1994Co-Authors: Charles J. BrokawAbstract:The distinct damped, or attenuated, bending pattern observed when demembranated sperm flagella of the tunicate, Ciona, are reactivated in the presence of 2 mM Li+ has been analysed in detail. In these patterns, bends are initiated at the base of the flagellum, but die out after they start to propagate along the flagellum, so that little or no bending is seen in the distal half of the flagellum. A quantitative descriptive analysis shows that the distinctive feature of this attenuation of bending wave Amplitude is an asymmetric interbend decay, or slippage, occuring, on average, only at the transitions between a reverse bend and the preceding principal bend. This attenuation is combined with a significant amount of synchronous sliding in the distal half of the flagellum and a decrease in propagation velocity of transitions between bends in the mid-region of the flagellum. Computer simulations demonstrate that the synchronous sliding in the distal half of these flagella can be an entirely passive consequence of the mechanical interaction between active sliding and bending in the basal third of the flagellum and viscous resistances to movement of the distal region of the flagellum through the fluid environment. The current computer models do not contain a mechanism for asymmetric interbend decay that can reproduce these attenuated bending patterns. © 1994 Wiley-Liss, Inc.
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Microtubule sliding in Reduced-Amplitude bending waves of Ciona sperm flagella: resolution of metachronous and synchronous sliding components of stable bending waves.
Cell motility and the cytoskeleton, 1993Co-Authors: Charles J. BrokawAbstract:Microtubule sliding associated with the bending of reactivated flagella of demembranated spermatozoa of the tunicate, Ciona, has been analyzed using a descriptive model that permits quantitation of metachronous and synchronous components of sliding. Reduced-Amplitude bending waves, obtained by addition of increased salt (K acetate), lithium, or vanadate to the reactivation solutions, have been examined. Increased K acetate can decrease bend angle by as much as 70% with little change in frequency. In all cases, a decrease in the Amplitude, or bend angle, of propagated bends is measured as a decrease in the metachronous component of sliding and is associated with a reduction in the growth of new bends after they begin to propagate during the second half-cycle of bend development. At higher K acetate concentrations, bend growth during the second half-cycle of bend development is very strongly Reduced and may even become negative. A disparity between the rates of bend growth in the first and second half-cycles of bend development corresponds to a large amount of synchronous sliding in the distal portion of the flagellum. When the synchronous sliding component is large, the sliding velocity in a propagating bend decreases to near-0 values and may even reverse its direction as the bend propagates through the mid-region of the flagellum. Since these large perturbations of sliding velocity do not interfere with regular propagation of bends with nearly constant bend angle, the bend propagation mechanism cannot operate by metachronous control of the velocity of sliding, and is unlikely to operate by local monitoring of either the amount or velocity of sliding. These observations therefore argue against models in which active sliding is regulated by shear or sliding velocity, and make curvature-controlled models relatively more attractive. In many cases, a reduction in sliding during bend initiation (the first half-cycle of development of new bends) also contributes to the decreased Amplitude of propagated bends. These changes in bend initiation are similar in both full-length flagella and in flagella shortened by breakage. The amount of sliding that occurs during bend initiation is relatively independent of the distribution of sliding between metachronous and synchronous components in the distal part of the flagellum. These observations therefore provide additional evidence that bend initiation and bend propagation are independent and separable processes. © 1993 Wiley-Liss, Inc.
P. Bouche - One of the best experts on this subject based on the ideXlab platform.
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True neurogenic thoracic outlet syndrome: Electrophysiological diagnosis in six cases
Muscle & nerve, 1998Co-Authors: N. Le Forestier, A. Moulonguet, Thierry Maisonobe, P. BoucheAbstract:We report 6 patients with true neurogenic thoracic outlet syndrome. All were female and presented unilateral severe atrophy of the thenar muscles. Pain in the affected upper limb was frequently reported, but sensory deficit was slight or absent. Reduced Amplitude of ulnar and median compound muscle action potential associated with a normal Amplitude of median sensory nerve action potential (SNAP) and a Reduced Amplitude of ulnar SNAP was indicative of a chronic axon loss in the lower trunk of the brachial plexus. The absence of the medial antebrachial cutaneous SNAP in 5 patients and a reduction in Amplitude compared to the unaffected side in the other patient indicated a C8-T1 postganglionic radicular lesion or a lower brachial plexus neuropathy. Radiography showed a rudimentary bilateral cervical rib or an elongated C7 transverse process in all cases. Surgery was performed, and in each case the lower part of the brachial plexus was found to be stretched and angulated over a fibrous band, which was removed. Pain was relieved after 1-4 weeks, but at 1 year, there was only minimal motor improvement and the electrophysiological results were unchanged.
Fu‐chan Wei - One of the best experts on this subject based on the ideXlab platform.
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Recovery of sensation and somatosensory evoked potentials following toe-to-digit transplantation in man.
Muscle & nerve, 1995Co-Authors: Nai-shin Chu, Fu‐chan WeiAbstract:Recovery of digital nerve function in 21 patients with toe-to-digit transplantation was evaluated by clinical sensory tests and somatosensory evoked potentials (SEPs) to median and digital nerve stimulation. The mean interval between injury and surgery was 7 months, and that between surgery and study was 31 months. The transplanted toes achieved a satisfactory but incomplete recovery in temperature (warm and cold), pinprick, touch, vibration, and two-point discrimination in that order. The overall sensory status of the transplanted toes appeared to be closer to normal toes than to normal fingers. In SEPs from the transplanted side, median N9, N13, and N20 components had normal latency but Reduced Amplitude, whereas digital N9 component was usually absent, but N13 and N20 components had prolonged latency and Reduced Amplitude. Transplantation performed within 1 month after injury prevented Amplitude reduction in median SEPs and latency prolongation in digital SEPs. The SEP data suggest that timing of surgery was critical in preventing retrograde effect on the median nerve, and that recovery of digital nerve function was incomplete correlating with clinical sensory findings. © 1995 John Wiley & Sons, Inc.
Daniel H. Mathalon - One of the best experts on this subject based on the ideXlab platform.
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Reduced Amplitude of low frequency brain oscillations in the psychosis risk syndrome and early illness schizophrenia
Neuropsychopharmacology, 2016Co-Authors: Susanna L. Fryer, Brian J. Roach, Katherine Wiley, Rachel L. Loewy, J.m. Ford, Daniel H. MathalonAbstract:Low-frequency oscillations (LFOs) of the blood oxygen level-dependent (BOLD) signal are gaining interest as potential biomarkers sensitive to neuropsychiatric pathology. Schizophrenia has been associated with alterations in intrinsic LFOs that covary with cognitive deficits and symptoms. However, the extent to which LFO dysfunction is present before schizophrenia illness onset remains unknown. Resting-state FMRI data were collected from clinical high-risk (CHR; n=45) youth, early illness schizophrenia (ESZ; n=74) patients, and healthy controls (HCs; n=85) aged 12-35 years. Age-adjusted voxelwise fractional Amplitude of low-frequency fluctuations (fALFF; 0.01-0.08 Hz) of the BOLD signal was compared among the three groups. Main effects of Group (p<0.005 height threshold, familywise error cluster-level corrected p<0.05) were followed up via Tukey-corrected pairwise comparisons. Significant main effects of Group (p<0.05) revealed decreased fALFF in ESZ and CHR groups relative to HCs, with values in the CHR group falling between those of ESZ and HC groups. These differences were identified primarily in posterior cortex, including temporoparietal regions, extending into occipital and cerebellar lobes. Less LFO activity was related to greater symptom severity in both CHR and ESZ groups in several of these posterior cortical regions. These data support an intermediate phenotype of Reduced posterior cortical LFO Amplitude in CHR individuals, with resting fALFF values smaller than in HCs but higher than in ESZ patients. Findings indicate that LFO magnitude alterations relate to clinical symptoms and predate psychosis onset but are more pronounced in the early stages of schizophrenia.
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Reduced Amplitude of Low-Frequency Brain Oscillations in the Psychosis Risk Syndrome and Early Illness Schizophrenia.
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 2016Co-Authors: Susanna L. Fryer, Brian J. Roach, Katherine Wiley, Rachel L. Loewy, J.m. Ford, Daniel H. MathalonAbstract:Low-frequency oscillations (LFOs) of the blood oxygen level-dependent (BOLD) signal are gaining interest as potential biomarkers sensitive to neuropsychiatric pathology. Schizophrenia has been associated with alterations in intrinsic LFOs that covary with cognitive deficits and symptoms. However, the extent to which LFO dysfunction is present before schizophrenia illness onset remains unknown. Resting-state FMRI data were collected from clinical high-risk (CHR; n=45) youth, early illness schizophrenia (ESZ; n=74) patients, and healthy controls (HCs; n=85) aged 12-35 years. Age-adjusted voxelwise fractional Amplitude of low-frequency fluctuations (fALFF; 0.01-0.08 Hz) of the BOLD signal was compared among the three groups. Main effects of Group (p
N. Le Forestier - One of the best experts on this subject based on the ideXlab platform.
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True neurogenic thoracic outlet syndrome: Electrophysiological diagnosis in six cases
Muscle & nerve, 1998Co-Authors: N. Le Forestier, A. Moulonguet, Thierry Maisonobe, P. BoucheAbstract:We report 6 patients with true neurogenic thoracic outlet syndrome. All were female and presented unilateral severe atrophy of the thenar muscles. Pain in the affected upper limb was frequently reported, but sensory deficit was slight or absent. Reduced Amplitude of ulnar and median compound muscle action potential associated with a normal Amplitude of median sensory nerve action potential (SNAP) and a Reduced Amplitude of ulnar SNAP was indicative of a chronic axon loss in the lower trunk of the brachial plexus. The absence of the medial antebrachial cutaneous SNAP in 5 patients and a reduction in Amplitude compared to the unaffected side in the other patient indicated a C8-T1 postganglionic radicular lesion or a lower brachial plexus neuropathy. Radiography showed a rudimentary bilateral cervical rib or an elongated C7 transverse process in all cases. Surgery was performed, and in each case the lower part of the brachial plexus was found to be stretched and angulated over a fibrous band, which was removed. Pain was relieved after 1-4 weeks, but at 1 year, there was only minimal motor improvement and the electrophysiological results were unchanged.
