scholarly journals Effects of arterial perfusion pressure on force production in working human hand muscles.

1996 ◽  
Vol 495 (3) ◽  
pp. 885-891 ◽  
Author(s):  
R Fitzpatrick ◽  
J L Taylor ◽  
D I McCloskey
Keyword(s):  
Perfusion Pressure ◽  
Force Production ◽  
Human Hand ◽  
Arterial Perfusion ◽  
Hand Muscles

Effects of muscle perfusion pressure on fatigue and systemic arterial pressure in human subjects

1999 ◽  
Vol 86 (3) ◽  
pp. 845-851 ◽  
Author(s):  
Julie R. Wright ◽  
D. I. McCloskey ◽  
Richard C. Fitzpatrick
Keyword(s):  
Blood Pressure ◽  
Perfusion Pressure ◽  
Human Subjects ◽  
Normal Subjects ◽  
Voluntary Contraction ◽  
Muscle Performance ◽  
Central Blood Pressure ◽  
Human Hand ◽  
Adductor Pollicis Muscle ◽  
Arterial Perfusion

The effects of changes in arterial perfusion across the physiological range on the fatigue of a working human hand muscle were studied in seven normal subjects. With the hand above heart level, subjects made repeated isometric contractions of the adductor pollicis muscle at 50% of maximal voluntary contraction in a 6-s on, 4-s off cycle. To assess fatigue, a maximal isometric twitch was elicited in each “off” period by electrical stimulation of the ulnar nerve. The experiment was repeated at least 2 days later with the hand at heart level. Five subjects showed faster fatigue with the arm elevated, and two subjects showed little difference in fatigue for the two conditions. Central blood pressure rose in proportion to fatigue for the subjects overall and returned quickly to its initial level afterwards. We conclude that human muscle fatigue can be increased by physiological reductions in perfusion pressure. Central blood pressure increases as the muscle fatigues, a response that may partially offset declining muscle performance.

scholarly journals Angiotensin in Blood and Lymph Following Reduction in Renal Arterial Perfusion Pressure in Dogs

1963 ◽  
Vol 13 (4) ◽  
pp. 336-345 ◽  
Author(s):  
SANDFORD L. SKINNER ◽  
JAMES W. MCCUBBIN ◽  
IRVINE H. PAGE
Keyword(s):  
Perfusion Pressure ◽  
Arterial Perfusion

scholarly journals Variable Thumb Moment Arm Modeling and Thumb-Tip Force Production of a Human-Like Robotic Hand

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Taylor D. Niehues ◽  
Ashish D. Deshpande
Keyword(s):  
Physical Simulation ◽  
Three Dimensional ◽  
Force Production ◽  
Human Hand ◽  
Robotic Hand ◽  
Motion Data ◽  
Moment Arms ◽  
Musculoskeletal Structure ◽  
Thumb Motion ◽  
Force Vectors

The anatomically correct testbed (ACT) hand mechanically simulates the musculoskeletal structure of the fingers and thumb of the human hand. In this work, we analyze the muscle moment arms (MAs) and thumb-tip force vectors in the ACT thumb in order to compare the ACT thumb's mechanical structure to the human thumb. Motion data are used to determine joint angle-dependent MA models, and thumb-tip three-dimensional (3D) force vectors are experimentally analyzed when forces are applied to individual muscles. Results are presented for both a nominal ACT thumb model designed to match human MAs and an adjusted model that more closely replicates human-like thumb-tip forces. The results confirm that the ACT thumb is capable of faithfully representing human musculoskeletal structure and muscle functionality. Using the ACT hand as a physical simulation platform allows us to gain a better understanding of the underlying biomechanical and neuromuscular properties of the human hand to ultimately inform the design and control of robotic and prosthetic hands.

Evidence that low-threshold muscle afferents evoke long-latency stretch reflexes in human hand muscles

1991 ◽  
Vol 65 (5) ◽  
pp. 1089-1097 ◽  
Author(s):  
J. Noth ◽  
M. Schwarz ◽  
K. Podoll ◽  
F. Motamedi
Keyword(s):  
Index Finger ◽  
Angular Displacement ◽  
Metacarpophalangeal Joint ◽  
Muscle Afferents ◽  
Human Hand ◽  
Hand Muscles ◽  
Long Latency ◽  
M2 Response ◽  
Spinal Afferents ◽  
Wrist Flexors

1. The aim of the present study was to identify the type of spinal afferents involved in the generation of the long-latency response in intrinsic human hand muscles. Position-controlled extensions were imposed on the index finger or on the wrist of healthy subjects who were exerting a steady voluntary flexion force at the relevant joint. Averaged surface electromyographic (EMG) responses of the first dorsal interosseus muscle (FDI) or of the wrist flexors were evaluated with respect to latency and size. 2. Small transient angular displacements of the index finger (1 degree, as measured at the metacarpophalangeal joint), which are supposed to excite primary rather than secondary afferents, evoked two clearly discernible EMG responses with mean latencies of 32.3 ms (M1 response) and 54.7 ms (M2 response), respectively. The size of the M2 response exceeded the size of the M1 response by 60%. In the wrist flexors, transient stretch (1 degree) gave rise to a large M1 response (latency 22.8 ms) and a small, inconstent M2 response. 3. Small-amplitude vibration of the index finger elicited EMG responses in the FDI that were qualitatively and quantitatively similar to those seen in response to small transient stretches of the index finger. This was also true for fast ramp-and-hold stretches (stretch velocity 400 degrees/s, amplitude 5 degrees), whereas slow ramp-and-hold stretches (125 degrees/s, 5 degrees) elicited predominantly M2 responses. 4. In the FDI, the mechanical threshold of the M1 and M2 response to the transient angular displacement was approximately 0.15 degrees, with a tendency for the M2 response to appear at a lower threshold.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Superposition of the motor commands during creation of static efforts by human hand muscles

2012 ◽  
Vol 58 (1) ◽  
pp. 43-50 ◽  
Author(s):  
IV Vereshchaka ◽  
◽  
AV. Horkovenko ◽  
Keyword(s):  
Human Hand ◽  
Hand Muscles ◽  
Motor Commands

scholarly journals Vaso-occlusion by sickle cells: evidence for selective trapping of dense red cells

Blood ◽  
1986 ◽  
Vol 68 (5) ◽  
pp. 1162-1166 ◽  
Author(s):  
DK Kaul ◽  
ME Fabry ◽  
RL Nagel
Keyword(s):  
Density Gradient ◽  
Sickle Cell ◽  
Morphological Analysis ◽  
Microvascular Obstruction ◽  
Perfusion Pressure ◽  
Peripheral Resistance ◽  
Red Cells ◽  
Arterial Perfusion ◽  
Sickle Cells ◽  
Sickle Cell Crisis

We have characterized the type of red cells from sickle cell patients that were trapped in the course of sickle-cell vaso-occlusion. In addition, the perfusion conditions (arterial perfusion pressure [Pa] and oxygen tension [PO2]) leading to experimentally induced vaso- occlusion in the artificially perfused, innervated mesocecum microvascular preparation were determined. Microvascular obstruction was induced by decrease in Pa; the lower the Pa, the greater the peripheral resistance as well as the extent of obstruction. The cells involved in the obstruction were recovered by vasodilation (secondary to denervation) and increase in Pa. Densitometric analysis of density gradient-separated infused and trapped cells was supplemented with morphological analysis to ascertain the involvement of density classes as well as morphological types seen in oxy and deoxy sickle blood. The trapping phenomenon was sensitive to PO2. Percentage of densest gradient classes, ie, fraction 3 (F3; mainly dense unsicklable SS discocytes [USDs]) and fraction 4 (F4; irreversibly sickled cells [ISCs] and the densest discocytes), showed a significant increase in trapping when perfusion was switched from oxy to deoxy perfusate. Morphological analysis revealed that unsicklable SS discocytes are more effectively trapped when deoxygenated. The deoxygenation of infused cells did not further change the percentage of ISCs trapped, suggesting that ISCs are equally capable of sequestration in the oxy and the deoxy states. The venous effluent showed a selective and significant depletion of dense cells (F4) and ISC counts at all Pa. We conclude that the progressive obstruction of the microcirculation by sickle cells involves selective sequestration of the densest classes of cells and that this mechanism might explain their partial disappearance during painful sickle cell crisis.

Use of a thermal pulse decay system to assess avian renal blood flow during reduced renal arterial perfusion pressure

1992 ◽  
Vol 262 (1) ◽  
pp. R90-R98 ◽  
Author(s):  
R. F. Wideman ◽  
R. P. Glahn ◽  
W. G. Bottje ◽  
K. R. Holmes
Keyword(s):  
Blood Flow ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Renal Blood Flow ◽  
Regional Differences ◽  
Filtration Rate ◽  
Perfusion Pressure ◽  
Portal Flow ◽  
Arterial Perfusion ◽  
Restricted Group

Using a simplified avian kidney model, renal arterial perfusion pressure (RAPP) was reduced from 120 (control) to 70 mmHg (near the glomerular filtration rate autoregulatory limit) and then to 46 mmHg (below the glomerular filtration rate autoregulatory range) in kidneys with ambient or partially restricted renal portal flow. Renal blood flow (RBF) was measured with a thermal pulse decay (TPD) system, using TPD thermistor probes inserted at three locations to evaluate regional differences in RBF. The clearance (CPAH) and extraction of p-aminohippuric acid were used to calculate renal plasma flow (RPF). CPAH, RPF, and RBF values were consistently lower for kidneys with restricted portal flow than for kidneys with ambient portal flow. Reducing RAPP to 46 mmHg did not significantly reduce CPAH, RPF, or RBF in the ambient group but did significantly reduce CPAH and RPF (regressed on RAPP) in the restricted group. RBF was not significantly affected when RAPP was reduced in the restricted group, although significant regional differences in blood flow were recorded. Renal vascular resistance decreased significantly as RAPP was reduced to 46 mmHg in the ambient group, confirming the renal autoregulatory response. In separate validation studies, significant reductions in RBF were detected by the TPD system during acute obstructions of portal and/or arterial flow. Overall, the results support previous evidence that avian RBF remains constant over a wide range of RAPPs. Observations of nonuniform intrarenal distributions of portal blood flow suggest that the portal system maintains the constancy of RBF in regions with proportionately high portal-to-arterial flow ratios.

Comparison of responses to sarafotoxins 6a and 6c in pulmonary and systemic vascular beds

1992 ◽  
Vol 262 (3) ◽  
pp. H852-H861
Author(s):  
R. K. Minkes ◽  
J. A. Bellan ◽  
T. R. Higuera ◽  
P. J. Kadowitz
Keyword(s):  
Arterial Pressure ◽  
Vascular Resistance ◽  
Perfusion Pressure ◽  
Venous Pressure ◽  
Constant Flow ◽  
Flow Conditions ◽  
Arterial Perfusion ◽  
Intravenous Injections ◽  
Autonomic Reflexes ◽  
Pressure Changes

Cardiovascular and pulmonary responses to sarafotoxin (S) 6a and S6c were investigated in the anesthetized cat. Intravenous injections of the peptides in doses of 0.1-1.0 nmol/kg caused decreases or biphasic changes in arterial pressure (AP) and increases in central venous pressure, pulmonary arterial pressure (PAP), and cardiac output (CO). Secondary decreases in CO were observed in response to higher doses, and biphasic changes in systemic (SVR) and pulmonary (PVR) vascular resistances were observed. Under constant-flow conditions, the peptides only increased pulmonary lobar arterial perfusion pressure and lobar vascular resistance. AP responses to S6a, S6c, endothelin (ET)-1, ET-2, vasoactive intestinal contractor (VIC), and Lys7-ET-1 were similar, whereas AP responses to S6b and ET-3 were similar. S6a, S6b, S6c, ET-1, ET-2, ET-3, VIC, Lys7-ET-1, and big ET-1 increased PAP. S6a and S6c increased distal aortic and superior mesenteric arterial (SMA) blood flow and caused biphasic changes at the highest doses. Under constant-flow conditions, S6a and S6c produced dose-dependent biphasic changes in hindquarters perfusion pressure. Changes in SVR and PVR in response to the peptide were not affected by hexamethonium, glyburide, or meclofenamate, indicating that responses are independent of autonomic reflexes, activation of ATP-regulated K+ channels, or release of cyclooxygenase products. In contrast, N-nitro-L-arginine methyl ester decreased hindquarters vasodilator response to S6a and S6c. The present data show that S6a and S6c produce both vasodilation and vasoconstriction in the systemic vascular bed and increase lobar vascular resistance and that hindquarters vasodilator responses are mediated, in part, by the release of endothelium-derived relaxing factor.

Impact of cervical internal carotid clamping and radial artery graft bypass on cortical arterial perfusion pressure during craniotomy

2014 ◽  
Vol 37 (3) ◽  
pp. 493-500 ◽  
Author(s):  
Ken Kazumata ◽  
Hiroyasu Kamiyama ◽  
Tatsuya Ishikawa ◽  
Toshitaka Nakamura ◽  
Shunsuke Terasaka ◽  
...  
Keyword(s):  
Radial Artery ◽  
Internal Carotid ◽  
Perfusion Pressure ◽  
Radial Artery Graft ◽  
Arterial Perfusion ◽  
Artery Graft
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