Enhanced myogenic activation in skeletal muscle arterioles from spontaneously hypertensive rats

1993 ◽  
Vol 265 (6) ◽  
pp. H1847-H1855 ◽  
Author(s):  
J. C. Falcone ◽  
H. J. Granger ◽  
G. A. Meininger
Keyword(s):  
Venous Pressure ◽  
Muscle Length ◽  
Vascular Wall ◽  
Intraluminal Pressure ◽  
Active Tension ◽  
Hypertensive Rats ◽  
Cross Sectional ◽  
Wall Area ◽  
Myogenic Responses

The purpose of this study was to determine whether the vascular myogenic response is enhanced in hypertension. Experiments were conducted in the intact cremaster muscle microcirculation as well as in isolated arterioles of hypertensive (SHR) and normotensive (WKY) rats. Increasing venous pressure in vivo by approximately 5 mmHg had no effect on normotensive first- (1A) or third-order arteriolar (3A) diameters; in contrast, hypertensive 1A diameter decreased 4% (89 +/- 2 to 85 +/- 3 microns) with an 8% decrease in 3A (24 +/- 2 to 22 +/- 2 microns). To further examine this enhanced constriction to elevated intravascular pressure in SHR, diameter was monitored in isolated 1A during step increases and decreases in intraluminal pressure. Normotensive arterioles displayed myogenic responses between pressures of 50 and 170 cmH2O; in contrast, hypertensive arterioles demonstrated myogenic responses over an extended pressure range (50–210 cmH2O). In addition, the change in diameter for each step change in pressure was greater in the arterioles from SHR, indicating an increased myogenic responsiveness. The myogenic reactions were unaffected by alpha-receptor blockade with phentolamine (10(-6) M), indicating that adrenergic hypersensitivity was not involved in the enhanced response to stretch. Morphometric analysis of the vascular wall revealed no differences in wall thickness, cross-sectional wall area, or wall-to-lumen ratio between normotensive and hypertensive rats. The length-tension relationships for normotensive and hypertensive rats demonstrated that peak active tension occurred at nearly the same vascular smooth muscle length. In addition, SHR arterioles were capable of maintaining higher levels of active tension that WKY arterioles, indicating an altered length-tension curve in chronic arterial hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of bat wing venule contraction by transmural pressure changes

1992 ◽  
Vol 262 (3) ◽  
pp. H625-H634 ◽  
Author(s):  
M. J. Davis ◽  
X. Shi ◽  
P. J. Sikes
Keyword(s):  
Venous Pressure ◽  
Transmural Pressure ◽  
The Body ◽  
Intraluminal Pressure ◽  
Positive Pressure ◽  
Cross Sectional ◽  
Series Of Experiments ◽  
Pressure Changes ◽  
Bat Wing

We tested the hypothesis that the frequency and amplitude of spontaneous venular contractions in the bat wing could be modulated by changes in transmural pressure. In one series of experiments, venous pressure in the wing was elevated by pressurizing a box containing the body of the animal while the wing was exposed to atmospheric pressure. During this time, venular diameters were continuously recorded using intravital microscopic techniques while venular pressures were measured through servo-null micropipettes. In another series of experiments, single venular segments were dissected from the wing, cannulated, and pressurized in vitro. The results from both experimental protocols were qualitatively similar; alterations in venous pressure over a narrow range (+/- 5 cmH2O from control) produced substantial changes in contraction frequency and amplitude. The product of frequency and cross-sectional area was maximal over the venous pressure range between 10 and 15 cmH2O. Venules demonstrated a rate-sensitive component in their reaction to rapid pressure changes, because contraction bursts occurred immediately after positive pressure steps and quiescent periods often occurred after negative pressure steps. We conclude that venular vasomotion in the bat wing is modulated by intraluminal pressure and involves a bidirectional, rate-sensitive mechanism. In addition, comparisons with arteriolar vasomotion studies suggest that venules are more sensitive to luminal pressure changes than arterioles.

scholarly journals Three-dimensional geometrical changes of the human tibialis anterior muscle and its central aponeurosis measured with three-dimensional ultrasound during isometric contractions

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2260 ◽  
Author(s):  
Brent J. Raiteri ◽  
Andrew G. Cresswell ◽  
Glen A. Lichtwark
Keyword(s):  
Three Dimensional ◽  
Muscle Length ◽  
Pennation Angle ◽  
Human Muscle ◽  
Muscle Fibres ◽  
Isometric Contractions ◽  
Fascicle Length ◽  
Cross Sectional ◽  
Shape Changes

Background.Muscles not only shorten during contraction to perform mechanical work, but they also bulge radially because of the isovolumetric constraint on muscle fibres. Muscle bulging may have important implications for muscle performance, however quantifying three-dimensional (3D) muscle shape changes in human muscle is problematic because of difficulties with sustaining contractions for the duration of anin vivoscan. Although two-dimensional ultrasound imaging is useful for measuring local muscle deformations, assumptions must be made about global muscle shape changes, which could lead to errors in fully understanding the mechanical behaviour of muscle and its surrounding connective tissues, such as aponeurosis. Therefore, the aims of this investigation were (a) to determine the intra-session reliability of a novel 3D ultrasound (3DUS) imaging method for measuringin vivohuman muscle and aponeurosis deformations and (b) to examine how contraction intensity influencesin vivohuman muscle and aponeurosis strains during isometric contractions.Methods.Participants (n= 12) were seated in a reclined position with their left knee extended and ankle at 90° and performed isometric dorsiflexion contractions up to 50% of maximal voluntary contraction. 3DUS scans of the tibialis anterior (TA) muscle belly were performed during the contractions and at rest to assess muscle volume, muscle length, muscle cross-sectional area, muscle thickness and width, fascicle length and pennation angle, and central aponeurosis width and length. The 3DUS scan involved synchronous B-mode ultrasound imaging and 3D motion capture of the position and orientation of the ultrasound transducer, while successive cross-sectional slices were captured by sweeping the transducer along the muscle.Results.3DUS was shown to be highly reliable across measures of muscle volume, muscle length, fascicle length and central aponeurosis length (ICC ≥ 0.98, CV < 1%). The TA remained isovolumetric across contraction conditions and progressively shortened along its line of action as contraction intensity increased. This caused the muscle to bulge centrally, predominantly in thickness, while muscle fascicles shortened and pennation angle increased as a function of contraction intensity. This resulted in central aponeurosis strains in both the transverse and longitudinal directions increasing with contraction intensity.Discussion.3DUS is a reliable and viable method for quantifying multidirectional muscle and aponeurosis strains during isometric contractions within the same session. Contracting muscle fibres do work in directions along and orthogonal to the muscle’s line of action and central aponeurosis length and width appear to be a function of muscle fascicle shortening and transverse expansion of the muscle fibres, which is dependent on contraction intensity. How factors other than muscle force change the elastic mechanical behaviour of the aponeurosis requires further investigation.

scholarly journals Three-dimensional architecture of the whole human soleus muscle in vivo

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4610 ◽  
Author(s):  
Bart Bolsterlee ◽  
Taija Finni ◽  
Arkiev D’Souza ◽  
Junya Eguchi ◽  
Elizabeth C. Clarke ◽  
...  
Keyword(s):  
Soleus Muscle ◽  
Diffusion Tensor ◽  
Three Dimensional ◽  
Muscle Length ◽  
Fascicle Length ◽  
Cross Sectional ◽  
Quantitative Measurements ◽  
Muscle Fascicle ◽  
Total Muscle

Background Most data on the architecture of the human soleus muscle have been obtained from cadaveric dissection or two-dimensional ultrasound imaging. We present the first comprehensive, quantitative study on the three-dimensional anatomy of the human soleus muscle in vivo using diffusion tensor imaging (DTI) techniques. Methods We report three-dimensional fascicle lengths, pennation angles, fascicle curvatures, physiological cross-sectional areas and volumes in four compartments of the soleus at ankle joint angles of 69 ± 12° (plantarflexion, short muscle length; average ± SD across subjects) and 108 ± 7° (dorsiflexion, long muscle length) of six healthy young adults. Microdissection and three-dimensional digitisation on two cadaveric muscles corroborated the compartmentalised structure of the soleus, and confirmed the validity of DTI-based muscle fascicle reconstructions. Results The posterior compartments of the soleus comprised 80 ± 5% of the total muscle volume (356 ± 58 cm3). At the short muscle length, the average fascicle length, pennation angle and curvature was 37 ± 8 mm, 31 ± 3° and 17 ± 4 /m, respectively. We did not find differences in fascicle lengths between compartments. However, pennation angles were on average 12° larger (p < 0.01) in the posterior compartments than in the anterior compartments. For every centimetre that the muscle-tendon unit lengthened, fascicle lengths increased by 3.7 ± 0.8 mm, pennation angles decreased by −3.2 ± 0.9° and curvatures decreased by −2.7 ± 0.8 /m. Fascicles in the posterior compartments rotated almost twice as much as in the anterior compartments during passive lengthening. Discussion The homogeneity in fascicle lengths and inhomogeneity in pennation angles of the soleus may indicate a functionally different role for the anterior and posterior compartments. The data and techniques presented here demonstrate how DTI can be used to obtain detailed, quantitative measurements of the anatomy of complex skeletal muscles in living humans.

scholarly journals Estimation of the force–velocity properties of individual muscles from measurement of the combined plantarflexor properties

2020 ◽  
Vol 223 (18) ◽  
pp. jeb219980
Author(s):  
Mehrdad Javidi ◽  
Craig P. McGowan ◽  
David C. Lin
Keyword(s):  
Muscle Length ◽  
Muscle Architecture ◽  
Muscle Group ◽  
Cross Sectional ◽  
Fiber Properties ◽  
Group Modeling ◽  
Force Velocity ◽  
The Individual

ABSTRACTThe force–velocity (F–V) properties of isolated muscles or muscle fibers have been well studied in humans and other animals. However, determining properties of individual muscles in vivo remains a challenge because muscles usually function within a synergistic group. Modeling has been used to estimate the properties of an individual muscle from the experimental measurement of the muscle group properties. While this approach can be valuable, the models and the associated predictions are difficult to validate. In this study, we measured the in situ F–V properties of the maximally activated kangaroo rat plantarflexor group and used two different assumptions and associated models to estimate the properties of the individual plantarflexors. The first model (Mdl1) assumed that the percent contributions of individual muscles to group force and power were based upon the muscles' cross-sectional area and were constant across the different isotonic loads applied to the muscle group. The second model (Mdl2) assumed that the F–V properties of the fibers within each muscle were identical, but because of differences in muscle architecture, the muscles' contributions to the group properties changed with isotonic load. We compared the two model predictions with independent estimates of the muscles' contributions based upon sonomicrometry measurements of muscle length. We found that predictions from Mdl2 were not significantly different from sonomicrometry-based estimates while those from Mdl1 were significantly different. The results of this study show that incorporating appropriate fiber properties and muscle architecture is necessary to parse the individual muscles' contributions to the group F–V properties.

Intestinal microvascular responsiveness to norepinephrine in chronic portal hypertension

1991 ◽  
Vol 260 (4) ◽  
pp. H1135-H1143 ◽  
Author(s):  
T. Joh ◽  
D. N. Granger ◽  
J. N. Benoit
Keyword(s):  
Blood Flow ◽  
Portal Hypertension ◽  
Dose Response ◽  
Vessel Diameter ◽  
Maximal Response ◽  
Hypertensive Rats ◽  
Response Curves ◽  
Cross Sectional ◽  
On Line

Effects of chronic prehepatic portal hypertension on intestinal microvascular sensitivity to norepinephrine (NE) were studied. Normal and portal hypertensive rats were anesthetized, and the intestine was prepared for in vivo microscopic observation. The preparation was transferred to a video microscope and a first-, second-, or third-order submucosal arteriole (i.e., 1A, 2A, or 3A, respectively) selected for study. Microvascular diameter and arteriolar erythrocyte velocity were measured on-line, and arteriolar blood flow was subsequently calculated as the product of velocity and vessel cross-sectional area. Once steady-state conditions were reached, the preparation was exposed to incremental doses of NE and microvessel responses were recorded. Cumulative log dose-response curves relating the change in arteriolar blood flow and vessel diameter to NE concentration were constructed for each group of arterioles and the ED50 for maximal response obtained from each dose-response relationship. NE ED50 for 1A blood flow was significantly higher in portal hypertensive rats (2.57 +/- 0.25 microM) compared with control rats (1.48 +/- 0.19 microM). Analysis of the diameter responses of 1A, 2A, and 3A indicated that the loss of vascular NE sensitivity in chronic portal hypertension was localized to the terminal submucosal arterioles (2A and 3A). No differences in the diameter response of 1A were observed between normal and portal hypertensive rats. Separate experiments were conducted to test if glucagon, a known mediator of the hyperdynamic intestinal circulation in portal hypertension, could acutely alter NE responsiveness in normal animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastrocnemius muscle specific force in boys and men

2008 ◽  
Vol 104 (2) ◽  
pp. 469-474 ◽  
Author(s):  
Christopher I. Morse ◽  
Keith Tolfrey ◽  
Jeanette M. Thom ◽  
Vasilios Vassilopoulos ◽  
Constantinos N. Maganaris ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Muscle Length ◽  
Tanner Stage ◽  
Surface Emg ◽  
Specific Force ◽  
Moment Arm ◽  
Fascicle Length ◽  
Cross Sectional ◽  
Adult Men

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.

scholarly journals Geometric Features of the Pial Arteriolar Networks in Spontaneous Hypertensive Rats: A Crucial Aspect Underlying the Blood Flow Regulation

2021 ◽  
Vol 12 ◽  
Author(s):  
Dominga Lapi ◽  
Martina Di Maro ◽  
Nicola Serao ◽  
Martina Chiurazzi ◽  
Maurizio Varanini ◽  
...  
Keyword(s):  
Blood Flow ◽  
Peripheral Resistance ◽  
Hypertensive Rats ◽  
Cross Sectional ◽  
Spontaneously Hypertensive ◽  
Adult Age ◽  
Cranial Window ◽  
Frequency Components ◽  
Geometric Arrangements

BackgroundSeveral studies indicate that hypertension causes major changes in the structure of the vessel wall by affecting the regulation of blood supply to the tissues. Recently, it has been observed that capillary blood flow is also considerably influenced by the structural arrangement of the microvascular networks that undergo rarefaction (reduction of the perfused vessel number). Therefore, this study aimed to assess the geometric arrangements of the pial arteriolar networks and the arteriolar rhythmic diameter changes in spontaneously hypertensive rats (SHRs).MethodsFluorescence microscopy was utilized to observe in vivo the pial microcirculation through a closed cranial window. Pial arterioles were classified according to Strahler’s method. The arteriolar rhythmic diameter changes were evaluated by a generalization short-time Fourier transform.ResultYoung SHRs showed four orders of vessels while the adult ones only three orders. The diameter, length, and branching number obeyed Horton’s law; therefore, the vessels were distributed in a fractal manner. Larger arterioles showed more asymmetrical branches than did the smaller ones in young SHRs, while in adult SHRs smaller vessels presented asymmetrical branchings. In adult SHRs, there was a significant reduction in the cross-sectional area compared with the young SHRs: this implies an increase in peripheral resistance. Young and adult age-matched normotensive rats did not show significant alterations in the geometric arteriolar arrangement with advancing age, both had four orders of arteriolar vessels, and the peripheral resistance did not change significantly. Conversely, the frequency components evaluated in arteriolar rhythmic diameter changes of young and adult SHRs showed significant differences because of a reduction in the frequency components related to endothelial activity detected in adult SHRs.ConclusionIn conclusion, hypertension progressively causes changes in the microarchitecture of the arteriolar networks with a smaller number of vessels and consequent reduced conductivity, characteristic of rarefaction. This was accompanied by a reduction in the formation and release of independent and dependent – endothelial nitric oxide components regulating arterial vasomotion.

Endothelium-dependent, flow-induced dilation of isolated coronary arterioles

1990 ◽  
Vol 259 (4) ◽  
pp. H1063-H1070 ◽  
Author(s):  
L. Kuo ◽  
M. J. Davis ◽  
W. M. Chilian
Keyword(s):  
Intraluminal Pressure ◽  
Flow Mediated Dilation ◽  
Mechanical Removal ◽  
Reservoir Systems ◽  
Spontaneous Tone ◽  
The Mean ◽  
Myogenic Responses ◽  
Dependent Flow ◽  
Coronary Arterioles

Flow-mediated dilation has been documented in large conduit coronary arteries but not in coronary arterioles. The goal of this study was to determine whether this response occurs in coronary arterioles and whether it competes with myogenic constriction. Subepicardial arterioles (40-80 microns) were isolated and cannulated with two glass micropipettes connected to independent reservoir systems. During zero flow, myogenic responses were studied over the range of intraluminal pressure (IP) between 20 and 140 cmH2O. Myogenic constrictions and dilations was observed when IP was increased (greater than 60 cmH2O) and decreased (less than 60 cmH2O), respectively. Flow was initiated by simultaneously moving the reservoirs in equal and opposite directions, thus generating a pressure gradient (delta P) without changing the mean luminal pressure (range delta P = 4-60 cmH2O). Flow-induced responses were studied at low, intermediate, and high myogenic tones by setting IP at 20, 60, and 100 cmH2O, respectively. The threshold for flow-induced dilation was delta P = 4 cmH2O, and maximum dilation was observed at delta P = 20 cmH2O. Red cell velocities in isolated arterioles at delta P of 4 and 60 cmH2O were 1.2 +/- 0.2 and 15.9 +/- 1.3 mm/s, respectively, which are within the range of those reported for coronary microvessels in vivo. The magnitude of the flow-induced dilation was greatest at the intermediate tone (60 cmH2O IP) but was attenuated at lower and higher IP. After mechanical removal of the endothelium, spontaneous tone and myogenic responses were preserved, but flow-induced dilation and bradykinin-induced dilation were abolished.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals In vivo human gracilis whole muscle passive stress-sarcomere strain relationship

2021 ◽  
Author(s):  
Lomas S. Persad ◽  
Benjamin I. Binder-Markey ◽  
Alexander Y. Shin ◽  
Kenton R. Kaufman ◽  
Richard L. Lieber
Keyword(s):  
Mechanical Properties ◽  
Sarcomere Length ◽  
Mammalian Species ◽  
Muscle Length ◽  
Human Muscle ◽  
Gracilis Muscle ◽  
Rabbit Muscle ◽  
Cross Sectional ◽  
Whole Muscle

We measured the passive mechanical properties of intact, living human gracilis muscles (n=11 individuals, 1 female, age: 33±12years, mass: 89±23kg, height: 177±8cm). Measurements were performed in patients undergoing surgery for free functioning myocutaneous tissue transfer of the gracilis muscle to restore elbow flexion after brachial plexus injury. Whole muscle force of the gracilis tendon was measured in four joint configurations (JC1-JC4) with a buckle force transducer placed at the distal tendon. Sarcomere length was also measured by biopsy from the proximal gracilis muscle. After the muscle was removed a three-dimensional volumetric reconstruction of the muscle was created via photogrammetry. Muscle length from JC1 to JC4 increased by 3.3±1.0 cm, 7.7±1.2 cm, 10.5±1.3 cm and 13.4±1.2 cm respectively, corresponding to 15%, 34%, 46% and 59% muscle fiber strain respectively. Muscle volume and an average optimal fiber length of 23.1±0.7 cm yielded an average muscle physiological cross-sectional area of 6.8±0.7 cm2 which is approximately three times that measured previously from cadaveric specimens. Absolute passive tension increased from 0.90±0.21 N in JC1 to 16.50±2.64 N in JC4. As expected, sarcomere length also increased from 3.24±0.08 µm at JC1 to 3.63±0.07 µm at JC4, which are on the descending limb of the human sarcomere length-tension curve. Peak passive muscle stress was 27.8±5.5 kPa in JC4 and muscle modulus ranged from 44.8 MPa in JC1 to 125.7 MPa in JC4. Compared to other mammalian species, human muscle passive mechanical properties are more similar to rodent muscle than rabbit muscle. These data provide direct measurements of whole human muscle passive mechanical properties that can be used in modeling studies and for understanding comparative passive mechanical properties among mammalian muscles.

Relative metabolic utilization of in situ rabbit soleus muscle: thermistor-based measurements and model

2000 ◽  
Vol 203 (23) ◽  
pp. 3667-3674
Author(s):  
K.J. Gustafson ◽  
G.D. Egrie ◽  
S.H. Reichenbach
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Muscle Length ◽  
Multiple Linear Regression Model ◽  
Active Tension ◽  
Contraction Duration ◽  
Continuous Power

Electrically conditioned skeletal muscle can provide the continuous power source for cardiac assistance devices. Optimization of the available sustained power from in vivo skeletal muscle requires knowledge of its metabolic utilization and constraints. A thermistor-based technique has been developed to measure temperature changes and to provide a relative estimate for metabolic utilization of in situ rabbit soleus muscle. The relative thermistor response, active tension and muscle displacement were measured during cyclic isometric and isotonic contractions across a range of muscle tensions and contraction durations. The thermistor response demonstrated linear relationships versus both contraction duration at a fixed muscle length and active tension at a fixed contraction duration (r(2)=0.90+/−0.14 and 0.70+/−0.21, respectively; means +/− s.d.). A multiple linear regression model was developed to predict normalized thermistor response, DeltaT, across a range of conditions. Significant model variables were identified using a backward stepwise regression procedure. The relationships for the in situ muscles were qualitatively similar to those reported for mammalian in vitro muscle fiber preparations. The model had the form DeltaT=C+at(c)F+bW, where the constant C, and coefficients for the contraction duration t(c) (ms), normalized active tension F and normalized net work W were C=−1.00 (P&lt;0.001), a=5.97 (P&lt;0.001) and b=2.12 (P&lt;0.001).

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