The Experts below are selected from a list of 9006 Experts worldwide ranked by ideXlab platform
Timothy I Musch - One of the best experts on this subject based on the ideXlab platform.
-
effect of chronic heart failure in older rats on respiratory Muscle and Hindlimb blood flow during submaximal exercise
Respiratory Physiology & Neurobiology, 2017Co-Authors: Joshua R Smith, David C Poole, Sue K Hageman, Craig A Harms, Timothy I MuschAbstract:Submaximal exercise diaphragm blood flow (BF) is elevated in young chronic heart failure (CHF) rats, while it is unknown if this occurs in older animals. Respiratory and Hindlimb Muscle BFs (radiolabeled microspheres) were measured at rest and during submaximal exercise (20m/min, 5% grade) in older healthy (n=7) and CHF (n=6) Fischer 344X Brown Norway rats (27-29 mo old). Older CHF, compared to healthy, rats had greater (p<0.01) left ventricular end-diastolic pressure and right ventricle and lung weight (normalized to body weight). During submaximal exercise, respiratory and Hindlimb Muscle BFs increased (p<0.02) in both groups, while diaphragm BF was higher (CHF: 257±32; healthy: 121±9mL/min/100g, p<0.01) and Hindlimb BF lower (CHF: 111±10; healthy: 133±12mL/min/100g, p=0.04) in older CHF compared to healthy rats. Submaximal exercise Hindlimb BF was negatively related (r=-0.93; p=0.03) to diaphragm BF in older CHF rats. During submaximal exercise, diaphragm BF is elevated in older CHF compared to healthy rats in proportion to the compromised Hindlimb BF.
-
critical speed in the rat implications for Hindlimb Muscle blood flow distribution and fibre recruitment
The Journal of Physiology, 2010Co-Authors: Steven W Copp, Daniel M Hirai, Timothy I Musch, David C PooleAbstract:Critical speed (CS) constitutes an important metabolic and performance demarcator. However, active skeletal Muscle blood flow distribution specifically surrounding CS remains unknown. We tested the hypotheses that CS could be accurately determined in the running rat and that measurement of Hindlimb inter- and intramuscular blood flow below and above CS would support that the greatest Muscle fibre recruitment above, relative to below, CS occurs in the predominantly glycolytic Muscles. Seven male Sprague–Dawley rats performed five constant-speed tests to exhaustion at speeds between 95 and 115% of the speed that elicited to determine CS. Subsequent constant-speed tests were performed at speeds incrementally surrounding CS to determine time to exhaustion, , and Hindlimb Muscle blood flow distribution. Speed and time to exhaustion conformed to a hyperbolic relationship (r2= 0.92 ± 0.03) which corresponded to a linear 1/time function (r2= 0.93 ± 0.02) with a CS of 48.6 ± 1.0 m min−1. Time to exhaustion below CS was ∼5× greater (P 0.05 vs. above CS). The 11 individual Muscles or Muscle parts that evidenced the greatest blood flow increases above, relative to below, CS were composed of ≥69% Type IIb/d/x Muscle fibres. Moreover, there was a significant correlation (P < 0.05, r= 0.42) between the increased blood flow above expressed relative to below CS and the percentage Type IIb/d/x fibres found in the individual Muscles or Muscle parts. These data validate the powerful CS construct in the rat and identify that running above CS, relative to below CS, incurs disproportionate blood flow increases (indicative of recruitment) in predominantly highly glycolytic Muscle fibres.
-
effects of neuronal nitric oxide synthase inhibition on resting and exercising Hindlimb Muscle blood flow in the rat
The Journal of Physiology, 2010Co-Authors: Steven W Copp, Daniel M Hirai, Timothy I Musch, Peter J Schwagerl, David C PooleAbstract:Nitric oxide (NO) derived from endothelial NO synthase (eNOS) is an integral mediator of vascular control during Muscle contractions. However, it is not known whether neuronal NOS (nNOS)-derived NO regulates tissue hyperaemia in healthy subjects, particularly during exercise. We tested the hypothesis that selective nNOS inhibition would reduce blood flow and vascular conductance (VC) in rat Hindlimb locomotor Muscle(s), kidneys and splanchnic organs at rest and during dynamic treadmill exercise (20 m min−1, 10% grade). Nineteen male Sprague–Dawley rats (555 ± 23 g) were assigned to either rest (n= 9) or exercise (n= 10) groups. Blood flow and VC were determined via radiolabelled microspheres before and after the intra-arterial administration of the selective nNOS inhibitor S-methyl-l-thiocitrulline (SMTC, 2.1 ± 0.1 μmol kg−1). Total Hindlimb Muscle blood flow (control: 20 ± 2 ml min−1 100g−1, SMTC: 12 ± 2 ml min−1 100g−1, P 0.05) between control and SMTC conditions. SMTC reduced (P < 0.05) blood flow and VC at rest and during exercise in the kidneys, adrenals and liver. These results enhance our understanding of the role of NO-mediated circulatory control by demonstrating that nNOS does not appear to subserve an obligatory role in the exercising Muscle hyperaemic response in the rat.
-
Respiratory Muscle blood flows during physiological and chemical hyperpnea in the rat
Journal of Applied Physiology, 2000Co-Authors: David C Poole, William L. Sexton, Bradley J. Behnke, Christine S. Ferguson, K. Sue Hageman, Timothy I MuschAbstract:Whether the diaphragm retains a vasodilator reserve at maximal exercise is controversial. To address this issue, we measured respiratory and Hindlimb Muscle blood flows and vascular conductances us...
Ann K. Goodchild - One of the best experts on this subject based on the ideXlab platform.
-
On the presence and functional significance of sympathetic premotor neurons with collateralized spinal axons in the rat
The Journal of Physiology, 2019Co-Authors: David G. S. Farmer, Natasha Pracejus, Bowen Dempsey, Anita Turner, Phillip Bokiniec, Julian F. R. Paton, Anthony E. Pickering, Jasmine Burguet, Philippe Andrey, Ann K. GoodchildAbstract:Key points Spinally-projecting neurons of the rostral ventrolateral medulla (RVLM) determine sympathetic outflow to different territories of the body. Previous studies suggest the existence of RVLM neurons with distinct functional classes, such as neurons that target sympathetic nerves bound for functionally-similar tissue types (e.g. Muscle vasculature). The existence of RVLM neurons with more general actions had not been critically tested. Using viral tracing, we show that a significant minority of RVLM neurons send axon collaterals to disparate spinal segments (T-2 and T-10). Furthermore, optogenetic activation of sympathetic premotor neurons projecting to lumbar spinal segments also produced activation of sympathetic nerves from rostral spinal segments that innervate functionally diverse tissues (heart and forelimb Muscle). These findings suggest the existence of individual RVLM neurons for which the axons branch to drive sympathetic preganglionic neurons of more than one functional class and may be able to produce global changes in sympathetic activity. We investigate the extent of spinal axon collateralization of rat rostral ventrolateral medulla (RVLM) sympathetic premotor neurons and its functional consequences. In anatomical tracing experiments, two recombinant herpes viral vectors with retrograde tropism and expressing different fluorophores were injected into the intermediolateral column at upper thoracic and lower thoracic levels. Histological analysis revealed that similar to 21% of RVLM bulbospinal neurons were retrogradely labelled by both vectors, indicating substantial axonal collateralization to disparate spinal segments. In functional experiments, another virus with retrograde tropism, a canine adenovirus expressing Cre recombinase, was injected into the left intermediolateral horn around the thoracolumbar junction, whereas a Cre-dependent viral vector encoding Channelrhodopsin2 under LoxP control was injected into the ipsilateral RVLM. In subsequent terminal experiments, blue laser light (473 nm x 20 ms pulses at 10 mW) was used to activate RVLM neurons that had been transduced by both vectors. Stimulus-locked activation, at appropriate latencies, was recorded in the following pairs of sympathetic nerves: forelimb and Hindlimb Muscle sympathetic fibres, as well as cardiac and either Hindlimb Muscle or lumbar sympathetic nerves. The latter result demonstrates that axon collaterals of lumbar-projecting RVLM neurons project to, and excite, both functionally similar (forelimb and Hindlimb Muscle) and functionally dissimilar (lumbar and cardiac) preganglionic neurons. Taken together, these findings show that the axons of a significant proportion of RVLM neurons collateralise widely within the spinal cord, and that they may excite preganglionic neurons of more than one functional class.
David C Poole - One of the best experts on this subject based on the ideXlab platform.
-
effect of chronic heart failure in older rats on respiratory Muscle and Hindlimb blood flow during submaximal exercise
Respiratory Physiology & Neurobiology, 2017Co-Authors: Joshua R Smith, David C Poole, Sue K Hageman, Craig A Harms, Timothy I MuschAbstract:Submaximal exercise diaphragm blood flow (BF) is elevated in young chronic heart failure (CHF) rats, while it is unknown if this occurs in older animals. Respiratory and Hindlimb Muscle BFs (radiolabeled microspheres) were measured at rest and during submaximal exercise (20m/min, 5% grade) in older healthy (n=7) and CHF (n=6) Fischer 344X Brown Norway rats (27-29 mo old). Older CHF, compared to healthy, rats had greater (p<0.01) left ventricular end-diastolic pressure and right ventricle and lung weight (normalized to body weight). During submaximal exercise, respiratory and Hindlimb Muscle BFs increased (p<0.02) in both groups, while diaphragm BF was higher (CHF: 257±32; healthy: 121±9mL/min/100g, p<0.01) and Hindlimb BF lower (CHF: 111±10; healthy: 133±12mL/min/100g, p=0.04) in older CHF compared to healthy rats. Submaximal exercise Hindlimb BF was negatively related (r=-0.93; p=0.03) to diaphragm BF in older CHF rats. During submaximal exercise, diaphragm BF is elevated in older CHF compared to healthy rats in proportion to the compromised Hindlimb BF.
-
critical speed in the rat implications for Hindlimb Muscle blood flow distribution and fibre recruitment
The Journal of Physiology, 2010Co-Authors: Steven W Copp, Daniel M Hirai, Timothy I Musch, David C PooleAbstract:Critical speed (CS) constitutes an important metabolic and performance demarcator. However, active skeletal Muscle blood flow distribution specifically surrounding CS remains unknown. We tested the hypotheses that CS could be accurately determined in the running rat and that measurement of Hindlimb inter- and intramuscular blood flow below and above CS would support that the greatest Muscle fibre recruitment above, relative to below, CS occurs in the predominantly glycolytic Muscles. Seven male Sprague–Dawley rats performed five constant-speed tests to exhaustion at speeds between 95 and 115% of the speed that elicited to determine CS. Subsequent constant-speed tests were performed at speeds incrementally surrounding CS to determine time to exhaustion, , and Hindlimb Muscle blood flow distribution. Speed and time to exhaustion conformed to a hyperbolic relationship (r2= 0.92 ± 0.03) which corresponded to a linear 1/time function (r2= 0.93 ± 0.02) with a CS of 48.6 ± 1.0 m min−1. Time to exhaustion below CS was ∼5× greater (P 0.05 vs. above CS). The 11 individual Muscles or Muscle parts that evidenced the greatest blood flow increases above, relative to below, CS were composed of ≥69% Type IIb/d/x Muscle fibres. Moreover, there was a significant correlation (P < 0.05, r= 0.42) between the increased blood flow above expressed relative to below CS and the percentage Type IIb/d/x fibres found in the individual Muscles or Muscle parts. These data validate the powerful CS construct in the rat and identify that running above CS, relative to below CS, incurs disproportionate blood flow increases (indicative of recruitment) in predominantly highly glycolytic Muscle fibres.
-
effects of neuronal nitric oxide synthase inhibition on resting and exercising Hindlimb Muscle blood flow in the rat
The Journal of Physiology, 2010Co-Authors: Steven W Copp, Daniel M Hirai, Timothy I Musch, Peter J Schwagerl, David C PooleAbstract:Nitric oxide (NO) derived from endothelial NO synthase (eNOS) is an integral mediator of vascular control during Muscle contractions. However, it is not known whether neuronal NOS (nNOS)-derived NO regulates tissue hyperaemia in healthy subjects, particularly during exercise. We tested the hypothesis that selective nNOS inhibition would reduce blood flow and vascular conductance (VC) in rat Hindlimb locomotor Muscle(s), kidneys and splanchnic organs at rest and during dynamic treadmill exercise (20 m min−1, 10% grade). Nineteen male Sprague–Dawley rats (555 ± 23 g) were assigned to either rest (n= 9) or exercise (n= 10) groups. Blood flow and VC were determined via radiolabelled microspheres before and after the intra-arterial administration of the selective nNOS inhibitor S-methyl-l-thiocitrulline (SMTC, 2.1 ± 0.1 μmol kg−1). Total Hindlimb Muscle blood flow (control: 20 ± 2 ml min−1 100g−1, SMTC: 12 ± 2 ml min−1 100g−1, P 0.05) between control and SMTC conditions. SMTC reduced (P < 0.05) blood flow and VC at rest and during exercise in the kidneys, adrenals and liver. These results enhance our understanding of the role of NO-mediated circulatory control by demonstrating that nNOS does not appear to subserve an obligatory role in the exercising Muscle hyperaemic response in the rat.
-
Respiratory Muscle blood flows during physiological and chemical hyperpnea in the rat
Journal of Applied Physiology, 2000Co-Authors: David C Poole, William L. Sexton, Bradley J. Behnke, Christine S. Ferguson, K. Sue Hageman, Timothy I MuschAbstract:Whether the diaphragm retains a vasodilator reserve at maximal exercise is controversial. To address this issue, we measured respiratory and Hindlimb Muscle blood flows and vascular conductances us...
John R Hutchinson - One of the best experts on this subject based on the ideXlab platform.
-
evolution of Hindlimb Muscle anatomy across the tetrapod water to land transition including comparisons with forelimb anatomy
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2020Co-Authors: Julia Molnar, John R Hutchinson, Rui Diogo, Stephanie E PierceAbstract:: Tetrapod limbs are a key innovation implicated in the evolutionary success of the clade. Although musculoskeletal evolution of the pectoral appendage across the fins-to-limbs transition is fairly well documented, that of the pelvic appendage is much less so. The skeletal elements of the pelvic appendage in some tetrapodomorph fish and the earliest tetrapods are relatively smaller and/or qualitatively less similar to those of crown tetrapods than those of the pectoral appendage. However, comparative and developmental works have suggested that the musculature of the tetrapod forelimb and Hindlimb was initially very similar, constituting a "similarity bottleneck" at the fins-to-limbs transition. Here, we used extant phylogenetic bracketing and phylogenetic character optimization to reconstruct pelvic appendicular Muscle anatomy in several key taxa spanning the fins-to-limbs and water-to-land transitions. Our results support the hypothesis that transformation of the pelvic appendages from fin-like to limb-like lagged behind that of the pectoral appendages. Compared to similar reconstructions of the pectoral appendages, the pelvic appendages of the earliest tetrapods had fewer Muscles, particularly in the distal limb (shank). In addition, our results suggest that the first tetrapods had a greater number of Muscle-Muscle topological correspondences between the pectoral and pelvic appendages than tetrapodomorph fish had. However, ancestral crown-group tetrapods appear to have had an even greater number of similar Muscles (both in terms of number and as a percentage of the total number of Muscles), indicating that the main topological similarity bottleneck between the paired appendages may have occurred at the origin of the tetrapod crown group. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.
-
evolution of Hindlimb Muscle anatomy across the tetrapod water to land transition including comparisons with forelimb anatomy
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2020Co-Authors: Julia Molnar, John R Hutchinson, Rui Diogo, Stephanie E PierceAbstract:Tetrapod limbs are a key innovation implicated in the evolutionary success of the clade. Although musculoskeletal evolution of the pectoral appendage across the fins-to-limbs transition is fairly well documented, that of the pelvic appendage is much less so. The skeletal elements of the pelvic appendage in some tetrapodomorph fish and the earliest tetrapods are relatively smaller and/or qualitatively less similar to those of crown tetrapods than those of the pectoral appendage. However, comparative and developmental works have suggested that the musculature of the tetrapod forelimb and Hindlimb was initially very similar, constituting a "similarity bottleneck" at the fins-to-limbs transition. Here, we used extant phylogenetic bracketing and phylogenetic character optimization to reconstruct pelvic appendicular Muscle anatomy in several key taxa spanning the fins-to-limbs and water-to-land transitions. Our results support the hypothesis that transformation of the pelvic appendages from fin-like to limb-like lagged behind that of the pectoral appendages. Compared to similar reconstructions of the pectoral appendages, the pelvic appendages of the earliest tetrapods had fewer Muscles, particularly in the distal limb (shank). In addition, our results suggest that the first tetrapods had a greater number of Muscle-Muscle topological correspondences between the pectoral and pelvic appendages than tetrapodomorph fish had. However, ancestral crown-group tetrapods appear to have had an even greater number of similar Muscles (both in terms of number and as a percentage of the total number of Muscles), indicating that the main topological similarity bottleneck between the paired appendages may have occurred at the origin of the tetrapod crown group. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 303:218-234, 2020. © 2018 American Association for Anatomy.
-
Analysis of Hindlimb Muscle moment arms in Tyrannosaurus rex using a three-dimensional musculoskeletal computer model: implications for stance, gait, and speed
Paleobiology, 2005Co-Authors: John R Hutchinson, Frank C. Anderson, Silvia S. Blemker, Scott L. DelpAbstract:Abstract Muscle moment arms are important determinants of Muscle function; however, it is challenging to determine moment arms by inspecting bone specimens alone, as Muscles have curvilinear paths that change as joints rotate. The goals of this study were to (1) develop a three-dimensional graphics-based model of the musculoskeletal system of the Cretaceous theropod dinosaur Tyrannosaurus rex that predicts Muscle-tendon unit paths, lengths, and moment arms for a range of limb positions; (2) use the model to determine how the T. rex Hindlimb Muscle moment arms varied between crouched and upright poses; (3) compare the predicted moment arms with previous assessments of Muscle function in dinosaurs; (4) evaluate how the magnitudes of these moment arms compare with those in other animals; and (5) integrate these findings with previous biomechanical studies to produce a revised appraisal of stance, gait, and speed in T. rex. The musculoskeletal model includes ten degrees of joint freedom (flexion/extension, ab...
David G. Reid - One of the best experts on this subject based on the ideXlab platform.
-
MRI detects early Hindlimb Muscle atrophy in Gly93Ala superoxide dismutase-1 (G93A SOD1) transgenic mice, an animal model of familial amyotrophic lateral sclerosis
NMR in biomedicine, 2004Co-Authors: Keith J. Brooks, Mark D. Hill, Paul D. Hockings, David G. ReidAbstract:MRI has been used to measure Hindlimb Muscle volume in female and male transgenic mice overexpressing the Gly93Ala (G93A) mutant human superoxide dismutase 1 (SOD1), a widely used model of familial amyotrophic lateral sclerosis (FALS), over the first 4 months of life. Significant decreases in the Hindlimb Muscle volume of the female G93A SOD1 mice were evident from 11 weeks of age, before other overt pathology appeared. By 15 weeks volume had decreased by 37% compared with 7 weeks, from 0.84+/-0.04 cm(3) (mean+/-standard deviation, n = 6) to 0.54+/-0.07 cm(3), (p 0.05). Wild-type male Muscle volume did not change significantly over this period, with an increase in body weight of 20%. Longitudinal MRI Hindlimb Muscle volume measurements may provide a straightforward, rapid, non-invasive and sensitive, way of monitoring outcome of experimental ALS treatments.