scholarly journals Leg muscles that mediate stability: mechanics and control of two distal extensor muscles during obstacle negotiation in the guinea fowl

2011 ◽  
Vol 366 (1570) ◽  
pp. 1580-1591 ◽  
Author(s):  
Monica A. Daley ◽  
Andrew A. Biewener

Here, we used an obstacle treadmill experiment to investigate the neuromuscular control of locomotion in uneven terrain. We measured in vivo function of two distal muscles of the guinea fowl, lateral gastrocnemius (LG) and digital flexor-IV (DF), during level running, and two uneven terrains, with 5 and 7 cm obstacles. Uneven terrain required one step onto an obstacle every four to five strides. We compared both perturbed and unperturbed strides in uneven terrain to level terrain. When the bird stepped onto an obstacle, the leg became crouched, both muscles acted at longer lengths and produced greater work, and body height increased. Muscle activation increased on obstacle strides in the LG, but not the DF, suggesting a greater reflex contribution to LG. In unperturbed strides in uneven terrain, swing pre-activation of DF increased by 5 per cent compared with level terrain, suggesting feed-forward tuning of leg impedance. Across conditions, the neuromechanical factors in work output differed between the two muscles, probably due to differences in muscle–tendon architecture. LG work depended primarily on fascicle length, whereas DF work depended on both length and velocity during loading. These distal muscles appear to play a critical role in stability by rapidly sensing and responding to altered leg–ground interaction.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3567-3567
Author(s):  
Tatiana Ulyanova ◽  
Gregory V. Priestley ◽  
Yi Jiang ◽  
Stephen Padilla ◽  
Thalia Papayannopoulou

Abstract Previous experiments in vitro have emphasized the important role of a5b1 integrin/fibronectin interactions in terminal stages of erythroid differentiation (JCB1987, 105:3105), whereas in vivo experiments with genetically deficient mice (JI2000, 165:4667) and recent in vitro ones emphasized the important contribution of a4b1 integrin in the expansion of fetal erythroid progenitors (JCB2007, 177:871) or for optimal responses post stress in adult animals (MCB2003, 23:9349). However, no abnormalities in erythropoiesis were reported in a model of conditional ablation of b1 integrins post-transplantation (Blood2006, 108:1857). Therefore, it has not been clear to what extent each of the two major b1 integrins (a4b1 and a5b1) alone or in combination is critical for expansion and/or terminal erythroid differentiation of adult cells at homeostasis and/or after stress. We have made detailed and parallel observations comparing erythropoiesis in two genetic models with conditional ablation of b1 or a4 integrins at homeostasis and after phenylhydrazine (PHZ)-mediated stress. Basal erythropoiesis in b1-, a4-deficient and control mice as assessed by hematocrit levels and total nucleated erythroid cells (Ter119+) in BM and spleen was similar. Furthermore, both b1 and a4-deficient mice showed an increase in circulating progenitors (1275±230 CFC/ml PB, 2446±256 CFC/ml PB, respectively) over controls (338±113 CFC/ml PB). However, post PHZ-induced hemolytic stress there was a dramatic difference in outcomes of b1-deficient, but modest differences in a4-deficient mice compared to controls. Survival of b1-deficient mice by day 6 post PHZ was 33% compared to 100% in a4-deficient and control groups. In b1-deficient animals, no significant increase in spleen cellularity (153±26×106 and194±64×106 cells/spleen at day 0 and 6 post PHZ, respectively) was detected and the expansion of total erythroid precursors (CD71hi,Ter119+) in the spleen was minimal (from 2.08×106 to 10.8×106 cells/spleen at day 6). In contrast, in a4-deficient and control mice by the same time spleen cellularity increased respectively by 3 and 8 fold, and erythroid precursors expanded by 400 and 2,500 fold. Of interest, BM response to PHZ was not significantly different among all groups. To test whether the splenic response was cell-autonomous or environmentally controlled we compared PHZ response in wild type recipients reconstituted with b1-ablated (Cre+b1D/D) or with control (Cre-b1f/f) BM cells. Recipients of b1-ablated cells had an impaired response compared to recipients of control cells, which was somewhat intermediate to that seen in non-transplanted b1-deficient animals; by day 6 post PHZ, spleen cellularity was 300±24×106 cells/spleen and erythroid precursors expanded by 130 fold in recipients of b1-ablated BM cells compared to 859±159×106 cells/spleen and 900 fold precursor increase in control recipients. These data suggest that both erythroid and their environmental cells were responsible for the reduced survival and poor spleen response in b1-deficient mice. The target environmental cells (fibroblasts, endothelial cells, macrophages) and/or matrix involved will be the focus of future studies. It is of interest that in contrast to splenic response, the increased release of progenitors from BM seen in animals reconstituted with b1D/D cells was as high as that seen in non-transplanted b1- deficient animals and with the same qualitative characteristics, suggesting this alteration in biodistribution of progenitors is cell autonomous. Taken together, our data suggest that a combined expression of b1 integrins in erythroid and cells in their microenvironment is critical for survival and optimal splenic response to a PHZ-induced stress in adult mice; release of progenitors seen at homeostasis in both b1 and a4 models is cell autonomous with a preferential erythroid progenitor release from BM seen only in b1-deficient but not in a4-deficient mice; in contrast to results with fetal liver cells showing a critical role of a4b1 but not a5b1 integrin for proliferative expansion of erythroid cells, in adults a5b1 expression in erythroid and environmental cells in the spleen assumes a more critical role. Our data expand the current knowledge on the distinct dependency of a4b1 vs a5b1 integrins in basal vs stress erythropoiesis and bridge previously divergent information from in vitro and in vivo experiments.


2006 ◽  
Vol 101 (4) ◽  
pp. 1060-1069 ◽  
Author(s):  
C. P. McGowan ◽  
H. A. Duarte ◽  
J. B. Main ◽  
A. A. Biewener

The goal of this study was to test whether the contractile patterns of two major hindlimb extensors of guinea fowl are altered by load-carrying exercise. We hypothesized that changes in contractile pattern, specifically a decrease in muscle shortening velocity or enhanced stretch activation, would result in a reduction in locomotor energy cost relative to the load carried. We also anticipated that changes in kinematics would reflect underlying changes in muscle strain. Oxygen consumption, muscle activation intensity, and fascicle strain rate were measured over a range of speeds while animals ran unloaded vs. when they carried a trunk load equal to 22% of their body mass. Our results showed that loading produced no significant ( P > 0.05) changes in kinematic patterns at any speed. In vivo muscle contractile strain patterns in the iliotibialis lateralis pars postacetabularis and the medial head of the gastrocnemius showed a significant increase in active stretch early in stance ( P < 0.01), but muscle fascicle shortening velocity was not significantly affected by load carrying. The rate of oxygen consumption increased by 17% ( P < 0.01) during loaded conditions, equivalent to 77% of the relative increase in mass. Additionally, relative increases in EMG intensity (quantified as mean spike amplitude) indicated less than proportional recruitment, consistent with force enhancement via stretch activation, in the proximal iliotibialis lateralis pars postacetabularis; however, a greater than proportional increase in the medial gastrocnemius was observed. As a result, when averaged for the two muscles, EMG intensity increased in direct proportion to the fractional increase in load carried.


2008 ◽  
Vol 104 (2) ◽  
pp. 469-474 ◽  
Author(s):  
Christopher I. Morse ◽  
Keith Tolfrey ◽  
Jeanette M. Thom ◽  
Vasilios Vassilopoulos ◽  
Constantinos N. Maganaris ◽  
...  

The aim of this study was to assess whether the in vivo specific force and architectural characteristics of the lateral gastrocnemius (GL) muscle of early pubescent boys ( n = 11, age = 10.9 ± 0.3 yr, Tanner stage 2) differed from those of adult men ( n = 12, age = 25.3 ± 4.4 yr). Plantarflexor torque was 55% lower in the boys (77.4 ± 21.4 N·m) compared with the adults (175.6 ± 31.7 N·m, P < 0.01). Physiological cross-sectional area (PCSA), determined in vivo using ultrasonography and MRI, was 52% smaller in the boys ( P < 0.01). No difference was found in pennation angle, or in the ratio of fascicle length ( Lf) to muscle length between the boys and men. Moment arm length was 25% smaller in the boys ( P < 0.01). Antagonist coactivation, assessed using surface EMG on the dorsiflexors, was not different between the boys and men (11.8 ± 6.7% and 13.5 ± 5.8%, respectively). Surprisingly, GL force normalized to PCSA (specific force) was significantly higher (21%) in the boys than in the men (13.1 ± 2.0 vs. 15.9 ± 2.7 N/cm2, P < 0.05). This finding could not be explained by differences in moment arm length, muscle activation, or architecture, and other factors, such as tendinous characteristics and/or changes in moment arm length with contraction, may be held responsible. These observations warrant further investigation.


2014 ◽  
Vol 116 (11) ◽  
pp. 1455-1462 ◽  
Author(s):  
B. W. Hoffman ◽  
A. G. Cresswell ◽  
T. J. Carroll ◽  
G. A. Lichtwark

Extensive muscle damage can be induced in isolated muscle preparations by performing a small number of stretches during muscle activation. While typically these fiber strains are large and occur over long lengths, the extent of exercise-induced muscle damage (EIMD) observed in humans is normally less even when multiple high-force lengthening actions are performed. This apparent discrepancy may be due to differences in muscle fiber and tendon dynamics in vivo; however, muscle and tendon strains have not been quantified during muscle-damaging exercise in humans. Ultrasound and an infrared motion analysis system were used to measure medial gastrocnemius fascicle length and lower limb kinematics while humans walked backward, downhill for 1 h (inducing muscle damage), and while they walked briefly forward on the flat (inducing no damage). Supramaximal tibial nerve stimulation, ultrasound, and an isokinetic dynamometer were used to quantify the fascicle length-torque relationship pre- and 2 h postexercise. Torque decreased ∼23%, and optimal fascicle length shifted rightward ∼10%, indicating that EIMD occurred during the damage protocol even though medial gastrocnemius fascicle stretch amplitude was relatively small (∼18% of optimal fascicle length) and occurred predominantly within the ascending limb and plateau region of the length-torque curve. Furthermore, tendon contribution to overall muscle-tendon unit stretch was ∼91%. The data suggest the compliant tendon plays a role in attenuating muscle fascicle strain during backward walking in humans, thus minimizing the extent of EIMD. As such, in situ or in vitro mechanisms of muscle damage may not be applicable to EIMD of the human gastrocnemius muscle.


2020 ◽  
Author(s):  
Namita Chatterjee ◽  
Cristina Espinosa-Diez ◽  
Sudarshan Anand

AbstractDefects in stress responses are important contributors in many chronic conditions including cancer, cardiovascular disease, diabetes, and obesity-driven pathologies like non-alcoholic steatohepatitis (NASH). Specifically, endoplasmic reticulum (ER) stress is linked with these pathologies and control of ER stress can ameliorate tissue damage. MicroRNAs have a critical role in regulating diverse stress responses including ER stress. Here we show that miR-494 plays a functional role during ER stress. ER stress inducers (tunicamycin & thapsigargin) robustly increase the expression of miR-494 in vitro in an ATF6 dependent manner. Surprisingly, miR-494 pretreatment dampens the induction and magnitude of ER stress in response to tunicamycin in endothelial cells. Conversely, inhibition of miR-494 increases ER stress de novo and amplifies the effects of ER stress inducers. Using Mass Spectrometry (TMT-MS) we identified 23 proteins that are downregulated by both tunicamycin and miR-494. Among these, we found 6 transcripts which harbor a putative miR-494 binding site. We validated the anti-apoptotic gene BIRC5 (survivin) as one of the targets of miR-494 during ER stress. Finally, induction of ER stress in vivo increases miR-494 expression in the liver. Pretreatment of mice with a miR-494 plasmid via hydrodynamic injection decreased ER stress in response to tunicamycin in part by decreasing inflammatory chemokines and cytokines. In summary, our data indicates that ER stress driven miR-494 may act in a feedback inhibitory loop to dampen downstream ER stress signaling. We propose that RNA-based approaches targeting miR-494 or its targets may be attractive candidates for inhibiting ER stress dependent pathologies in human disease.


2005 ◽  
Vol 99 (2) ◽  
pp. 603-608 ◽  
Author(s):  
Masaki Ishikawa ◽  
Paavo V. Komi ◽  
Michael J. Grey ◽  
Vesa Lepola ◽  
Gert-Peter Bruggemann

The present study was designed to explore how the interaction between the fascicles and tendinous tissues is involved in storage and utilization of elastic energy during human walking. Eight male subjects walked with a natural cadence (1.4 ± 0.1 m/s) on a 10-m-long force plate system. In vivo techniques were employed to record the Achilles tendon force and to scan real-time fascicle lengths for two muscles (medial gastrocnemius and soleus). The results showed that tendinous tissues of both medial gastrocnemius and soleus muscles lengthened slowly throughout the single-stance phase and then recoiled rapidly close to the end of the ground contact. However, the fascicle length changes demonstrated different patterns and amplitudes between two muscles. The medial gastrocnemius fascicles were stretched during the early single-stance phase and then remained isometrically during the late-stance phase. In contrast, the soleus fascicles were lengthened until the end of the single-stance phase. These findings suggest that the elastic recoil takes place not as a spring-like bouncing but as a catapult action in natural human walking. The interaction between the muscle fascicles and tendinous tissues plays an important role in the process of release of elastic energy, although the leg muscles, which are commonly accepted as synergists, do not have similar mechanical behavior of fascicles in this catapult action.


2011 ◽  
Vol 366 (1570) ◽  
pp. 1463-1465 ◽  
Author(s):  
Timothy E. Higham ◽  
Andrew A. Biewener ◽  
Scott L. Delp

Animal movement is often complex, unsteady and variable. The critical role of muscles in animal movement has captivated scientists for over 300 years. Despite this, emerging techniques and ideas are still shaping and advancing the field. For example, sonomicrometry and ultrasound techniques have enhanced our ability to quantify muscle length changes under in vivo conditions. Robotics and musculoskeletal models have benefited from improved computational tools and have enhanced our ability to understand muscle function in relation to movement by allowing one to simulate muscle–tendon dynamics under realistic conditions. The past decade, in particular, has seen a rapid advancement in technology and shifts in paradigms related to muscle function. In addition, there has been an increased focus on muscle function in relation to the complex locomotor behaviours, rather than relatively simple (and steady) behaviours. Thus, this Theme Issue will explore integrative aspects of muscle function in relation to diverse locomotor behaviours such as swimming, jumping, hopping, running, flying, moving over obstacles and transitioning between environments. Studies of walking and running have particular relevance to clinical aspects of human movement and sport. This Theme Issue includes contributions from scientists working on diverse taxa, ranging from humans to insects. In addition to contributions addressing locomotion in various taxa, several manuscripts will focus on recent advances in neuromuscular control and modulation during complex behaviours. Finally, some of the contributions address recent advances in biomechanical modelling and powered prostheses. We hope that our comprehensive and integrative Theme Issue will form the foundation for future work in the fields of neuromuscular mechanics and locomotion.


2019 ◽  
Author(s):  
JC Gordon ◽  
NC Holt ◽  
AA Biewener ◽  
MA Daley

AbstractAnimals must integrate feedforward, feedback and intrinsic mechanical control mechanisms to maintain stable locomotion. Recent studies of guinea fowl (Numida meleagris) revealed that the distal leg muscles rapidly modulate force and work output to minimize perturbations in uneven terrain. Here we probe the role of reflexes in the rapid perturbation response of muscle by studying the effects of proprioceptive loss. We induced bilateral loss of autogenic proprioception in the lateral gastrocnemius muscle (LG) using self-reinnervation. We compared ankle kinematics and in vivo muscle dynamics in birds with reinnervated LG and intact LG. Reinnervated and intact muscles exhibit similar force-length dynamics, with rapid changes in work to stabilize running obstacle terrain. Reinnervated LG exhibits 23ms earlier steady-state activation, consistent with feedforward tuning of activation phase to compensate for lost proprioception. Modulation of force duration is impaired in rLG, confirming the role of reflex feedback in regulating force duration in intact muscle.


2015 ◽  
Vol 2 (2) ◽  
pp. 26-31 ◽  
Author(s):  
A. Paliy ◽  
A. Zavgorodniy ◽  
B. Stegniy ◽  
A. Gerilovych

Due to the absence of elaborated effi cient means for specifi c prevention of bovine tuberculosis, it is ex- tremely important to detect and eliminate the source of infection and to take veterinary and sanitary preven- tive measures. Here the critical role is attributed to disinfection, which breaks the epizootic chain due to the elimination of pathogenic microorganisms in the environment and involves the application of disinfectants of different chemical groups. Aim. To study the tuberculocidal properties of new disinfectants DZPT-2 and FAG against atypical mycobacteria Mycobacterium fortitum and a TB agent Mycobacterium bovis. Methods. The bacteriological and molecular-genetic methods were used. Results. It was determined that DZPT-2 prepara- tion has bactericidal effect on M. fortuitum when used in the concentration of 2.0 % of the active ingredient (AI) when exposed for 5–24 h, while disinfectant FAG has a bactericidal effect in the concentration of 2.0 % when exposed for 24 h. Disinfectant DZPT-2 in the concentration of 2.0 % of the AI, when exposed for 5–24 h, and FAG preparation in the concentration of 2.0 %, when exposed for 24 h, and with the norm of consump- tion rate of 1 cubic decimeter per 1 square meter disinfect the test-objects (batiste, wood, glazed tile, metal, glass), contaminated with the TB agent M. bovis. Conclusions. Disinfecting preparations of DZPT-2 in the concentration of 2.0 % of AI when exposed for 5 h and FAG in the concentration of 2.0 % when exposed for 24 h may be used in the complex of veterinary and sanitary measures to prevent and control TB of farm ani- mals. The possibility of using the polymerase chain reaction as an additional method of estimating tuberculo- cide activity of disinfectants was proven.


2014 ◽  
Vol 1 (3) ◽  
pp. 3-7
Author(s):  
O. Zhukorskyy ◽  
O. Hulay

Aim. To estimate the impact of in vivo secretions of water plantain (Alisma plantago-aquatica) on the popula- tions of pathogenic bacteria Erysipelothrix rhusiopathiae. Methods. The plants were isolated from their natural conditions, the roots were washed from the substrate residues and cultivated in laboratory conditions for 10 days to heal the damage. Then the water was changed; seven days later the selected samples were sterilized using fi lters with 0.2 μm pore diameter. The dilution of water plantain root diffusates in the experimental samples was 1:10–1:10,000. The initial density of E. rhusiopathiae bacteria populations was the same for both experimental and control samples. The estimation of the results was conducted 48 hours later. Results. When the dilution of root diffusates was 1:10, the density of erysipelothrixes in the experimental samples was 11.26 times higher than that of the control, on average, the dilution of 1:100 − 6.16 times higher, 1:1000 – 3.22 times higher, 1:10,000 – 1.81 times higher, respectively. Conclusions. The plants of A. plantago-aquatica species are capable of affecting the populations of E. rhusiopathiae pathogenic bacteria via the secretion of biologically active substances into the environment. The consequences of this interaction are positive for the abovementioned bacteria, which is demon- strated by the increase in the density of their populations in the experiment compared to the control. The intensity of the stimulating effect on the populations of E. rhusiopathiae in the root diffusates of A. plantago-aquatica is re- ciprocally dependent on the degree of their dilution. The investigated impact of water plantain on erysipelothrixes should be related to the topical type of biocenotic connections, the formation of which between the test species in the ecosystems might promote maintaining the potential of natural focus of rabies. Keywords: Alisma plantago-aquatica, in vivo secretions, Erysipelothrix rhusiopathiae, population density, topical type of connections.


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