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At least 19 recordsLinked to original sources
PubMed1978

Effect of changing metabolic rate on local blood flow control in the canine hindlimb.

This study examined the effect of changing hindlimb metabolic rate on hindlimb blood flow control in anesthetized dogs. The hyperemias induced by graded levels of arterial hypoxia and the degree of steady state autoregulation evoked by changes in blood pressure were measured. Metabolic rate was increased above the resting value by direct electrical stimulation of hindlimb muscles at rates from 0.5 to 1.5 pulses/second, and in three dogs was reduced by cooling. In response to 6 minutes of arterial hypoxia, hindlimb blood flow steadily increased. At rest, and at each level of muscle stimulation, the steepness of the response increased as arterial oxygen saturation (SAO2) decreased. At all levels of SAO2, the response was steeper at increasing stimulation rates. For SAO2 greater than 50%, the relationship between the percentage increase in blood flow from control and SAO2, however, was unaffected by the degree of muscle activity, suggesting that during mild to moderate hypoxia the dynamics of the response were similar whether the muscles were at rest or exercising. The responses to severe hypoxia (SAO2 less than 50%) during stimulation were significantly enhanced compared with those at rest. Autoregulation of blood flow was measured in the steady state by comparing the relative change in blood flow from control with the relative change in blood pressure that produced it. Steady state autoregulation was weak at rest, but improved markedly with increasing muscle stimulation. Conversely, cooling the hindlimb depressed the resting steady state autoregulation. A close correlation was found between the degree of autoregulation and the hindlimb metabolic rate. The results suggest that tissue metabolic rate determines the precision of local blood flow control.

Animals↗
PubMedDate not supplied

Effects of clonidine on vascular responses in kidney and hindlimbs of cats.

1. Cardiovascular reflexes to intravenous adrenaline and histamine and to carotid occlusion were studied in the renal vasculature, and direct effects of noradrenaline and clinidoine were compared in renal and hindlimb vascular beds in anaesthetized cats. 2. Unlike its reported effects on cardiovascular reflexes in the hindlimbs, clonidine depressed all three reflexes in the kidneys. 3. Noradrenaline caused vasoconstriction when given directly into both renal and hindlimb circulartions, but clonidine produced vasoconstriction only in the hindlimb vascular bed. 4. These results suggest that alpha-adrenoceptors in the reanl vasculature may be different from those in the hindlimbs, and that the cardiovascular reflexes in these two areas are under different control.

Animals↗
PubMed1979

Effect of DOCA-NaCl hypertension on pre- and postcapillary resistance in isolated hindlimbs of dogs.

Measurements of precapillary resistance (Ra), postcapillary resistance (Ra), postcapillary resistance (Rv), capillary filtration coefficient (Kf), and mean capillary hydrostatic pressure (Pci) were made during constant-flow perfusion of isolated hindlimbs from control and deoxycorticosterone acetate (DOCA)-NaCl-treated hypertensive dogs by the isogravimetric method. Both Ra and Rv were found to be significantly increased in the hypertensive group, even after maximal vasodilatation with papaverine. The net decreases in Ra and Rv following papaverine infusion were not significantly different between control and hypertensive animals. These results suggest that the observed increases in Ra and Rv were due to structural adaptation (increased wall-to-lumen ratio). Nonpapaverinized hindlimbs from hypertensive dogs exhibited a significant 40% reduction in Kf, suggesting that capillary surface area for fluid exchange was decreased. The compliance of the hindlimb vascular bed was found to be significantly decreased in the hypertensive group. Pci of both groups of hindlimbs were not different between groups and was not affected by papaverine. This result suggests that net capillary permeability to plasma proteins in this preparation was not changed by hypertension.

Animals↗
PubMed1979

Direct measurement of arteriovenous anastomotic blood flow in the septic canine hindlimb.

Absolute blood flow through hindlimb capillaries and arteriovenous anastomoses (AVA) was determined by the radioactive microsphere technique of relative shunt measurement combined with direct (electromagnetic) measurement of femoral artery blood flow. Studies were performed before and 72 hours after infection was created in six dogs by implanting fecal-contaminated wicks in one hindlimb. Three control dogs had sterile wicks implanted. Septic dogs demonstrated decreased arterial pressure and increased core temperature with no change in mean cardiac index. Infected legs had increased total femoral blood flow, decreased peripheral resistance, decreased arteriovenous (A-V) O2 difference, but unchanged oxygen consumption, Paw temperature increased in both infected and normal contralateral limbs. Muscle blood flow (MBF) (Xe133 clearance) increased only in infected legs. A-V shunting increased five-fold and AVA flow increased seven-fold in infected hindlimbs, significantly more than that in contralateral or control limbs. Increased A-V shunting correlated highly (r=0.95) with increased total femoral blood flow in infected legs, but increased MBF was not correlated (r=0.05). Despite increased MBF, increased AVA flow occurs in septic canine hindlimbs and contributes to the low-resistance, high-flow, but unchanged oxygen consumption described in this model.

Animals↗
PubMed1978

Comparison of forelimb and hindlimb motor deficits following dorsal column section in monkeys.

Macaca speciosa monkeys were trained to acquire food reinforcement with motor responses that were defined by 4 different tasks. The effects of dorsal column lesions on the speed of these responses were compared for the forelimbs vs. the hindlimbs. Enduring impairments were not seen for any limb when the animal was required to accurately project a limb to different points in space, even with exclusion of visual guidance and with random variation of the start and stop points for each movement. Similarly, when the task required that the animals emit rapid response sequences, the forelimbs were impaired temporarily, but no long-term deficits were seen for the forelimbs or the hindlimbs. Although these impositions of spatial and temporal demands did not reveal striking disruptions of whole-limb movements, hindlimb grasp responses were shown to be impaired over long periods of postoperative testing. This corroborates previous findings for the forelimb and indicates that facility of distal extremity movement depends crucially on dorsal column-lemniscal input.

Animals↗
PubMed1977

Determinants of isogravimetric capillary pressure in the isolated dog hindlimb.

The hindlimb of the dog was rapidly isolated and carefully perfused in an attempt to prevent transcapillary fluid shifts into the interstitium which may occur during normal surgical isolation and perfusion. In the control preparation before weight was allowed to increase, isogravimetric capillary pressure (Pci) averaged 8 mmHg lower than colloid osmotic pressure of the plasma (IIp). As the weight of the leg was increased, Pci increased and IIp - Pci decreased. When weight was increased by 5.8%, IIp - Pci averaged 3 mmHg; with a 9.8% increase in weight, IIp - Pci averaged 1.3 mmHg. The calculated value of compliance of the interstitial space averaged 0.50 ml/mmHg per 100 g of tissue and increased approximately 10-fold as the weight of the leg was increased. Since IIp - Pci has always been reported to be approximately 2 mmHg when the hindleg was isolated with standard surgical techniques, these data suggest that the procedures normally used to isolate and perfuse the hindlimb caused the weight of the limb to increase by 6% or more before Pci was determined. Furthermore, it appears that most of the variation in the reported value of Pci is due to variation in the value of IIp since IIp - Pci has always been reported to be very close to 2 mmHg in the isolated hindlimb.

Animals↗
PubMed1976

Responses of cortical neurons (areas 3a and 4) to ramp stretch of hindlimb muscles in the baboon.

1. A study was made of the response of single cortical units in areas 3a and 4 to electrical stimulation of hindlimb muscle nerves and to ramp stretch of hindlimb muscles in baboons anesthetized with chloralose.2. Stimulation of hindlimb muscle nerves revealed a group I projection primarily to area 3a but with some input into adjacent area. 4. A major group II projection was found in area 4 adjacent to area 3a. A small number of area 3a neurons receive convergence from both group I and group II muscle afferents.3a. On the basis of their response pattern to ramp stretch, units were classified into one of six categories and their cytoarchitectonic location was determined. Units in area 3a had hynamic sensitivities equivalent to that of the primary spindle afferents. Although the discharge of some area 3a neurons also reflected differences in muscle length, most area 3a neurons had low position sensitivities. One unit type in area 3a did not respond to maintained muscle stretch and signaled only velocity of stretch.4. Units in area 4 had position sensitivities equivalent to that of primary and secondary spindle afferents. Although the discharge of some area 4 units reflected different velocities of muscle stretch, these units had dynamic sensitivities similar to those of secondary spindle afferents rather than those of primary afferents. One type of unit in area 4 had no dynamic component to muscle stretch and signaled only muscle length.5. The results demonstrate that there is a transfer of dynamic and position sensitivity from spindle afferents to cortical neurons. Furthermore, data processing has occurred because some units respond only to the steady-state length of muscle, while other units encode only the dynamic phase of stretch. This behavior is different from the responses to ramp stretch of either group I or group II muscle afferents in the baboon.6. The results demonstrate that single units in cerebral cortex can encode the information transmitted to the central nervous system by muscle spindle afferents. The purpose for which this information is used remains undetermined.

Action Potentials↗
PubMed1978

Cat hindlimb tactile dermatomes determined with single-unit recordings.

1. Single-unit recording from dorsal root ganglia was used to determine the dermatomes of L4-S2 segments in the cat. Dermatomes for low-threshold myelinated mechanoreceptor afferents are smaller than those reported in earlier studies of whole-root dermatomes. There are also sufficient discrepancies among earlier studies and with the present data to merit reexamination of hindlimb whole-root dermatomes. 2. Receptive-field size varies directly with distance from toes. Length/width ratio is essentially constant for different parts of the hindlimb. 3. Estimates of innervation density verify the long-standing assumption that innervation density is greater for foot and toes than for proximal hindlimb, at least for low-threshold cutaneous myelinated afferents.

Afferent Pathways↗
PubMed1979

[Central program for interaction between the hindlimbs of cats during locomotion].

Central program of interaction of hindlimbs during fictitious locomotion expressed in the time structure of motor discharges in nerves to different muscles was investigated in decerebrated and spinal immobilized cats. It was shown that in the decerebrated animals the program of interaction of hindlimbs (alternative or synphase) is determined by interaction of the flexor half-centres. The latter work either in-phase or out-of-phase. The character of activity of extensor half-centres is determined secondarily by alternating interaction of each of them with homolateral flexor half-centre. After injection of DOPA the central program of interaction of hindlimbs can be determined by synchronous work of extensor half-centres.

Animals↗
PubMed1979

Cardiovascular and respiratory chemoreflexes from the hindlimb sensory receptors evoked by intra-arterial injection of bradykinin and other chemical agents in the rabbit.

Intra-arterial injections of bradykinin into the hindlimb of the rabbit cause two types of cardiovascular reflex effects displayed in succession. The first-type effects appear early and are of inhibitory nature, being represented by systemic hypotension, contralateral hindlimb vasodilation and bradycardia; the second-type effects appear later and are excitatory in nature, consisting of hypertension, hindlimb vasoconstriction and tachycardia and occur closely associated with behavioral manifestations typical of the reaction to pain. Both the depressor and pressor effects are accompanied by hyperventilation. Analogous biphasic reflex responses may be caused by intraarterial injections of potassium ions. On the contrary, hypertonic solutions (NaCl, glucose) usually only produce second-type excitatory responses. No significant cardiocirculatory reflex effects are induced by even high doses of serotonin, nicotine, adenosine, adenosine triphosphate, adrenalin, noradrenalin, angiotensin, vasopressin and oxytocin. General anesthesia greatly inhibits the pressor reflexes and potentiates the depressor responses (to bradykinin and K ions) but does not appear to be a necessary condition for provoking depressor reflexes by chemical stimulation of somatic afferents. Both chemoreflex responses are prevented by sectioning the somatic nerves of the injected limb. Denervation of sinoaortic areas and of cardiopulmonary receptors by bilateral cervical vagotomy or complete removal of the skin from the injected limb does not prevent either type of chemoreflex response. These depressor and pressor chemoreflexes have been ascribed to activation of two functionally distinct types of sensory receptors in the skeletal muscle, differently sensitive to chemical substances and selectively concerned with different patterns of cardiocirculatory reflex response.

Animals↗
PubMed1978

Fore- and hindlimb proportions in Plio-Pleistocene hominids.

Associated fore- and hindlimb parts of five individuals are known from the hominid Plio-Pleistocene fossil collections in Africa. Four of these have been classified as Australopithecus and show definite evidence that in comparison with humans, forelimbs were relatively large and hindlimbs were relatively small. The fourth individual, placed in the genus Homo, has human proportions. These findings do not necessarily imply locomotor differences: the forelimbs may have been relatively long in Australopithecus simply because they were as yet not completely reduced from their generalized hominoid ancestral state.

Animals↗
PubMed1979

Reciprocal responses to tilt of neurones within both fore- and hindlimb regions of Deiters' nucleus.

In decerebrate cats with cerebellum intact the frequency response of 102 neurons located within the lateral vestibular nucleus (LVN) to sinusoidal stimulation of vestibular receptors was analyzed. Positional sensitive units, showing a reciprocal pattern of response to lateral tilting, characterized by an excitation during ipsilateral and a depression during contralateral tilt, were equally found in the rostroventral (forelimb) and dorsocaudal (hindlimb) divisions of the LVN. No unit was found to be excited during both ipsilateral and contralateral tilts. A comparison between these findings and those reported in cerebellectomized preparations indicates that the reciprocal pattern of response to tilt of neurons, particularly located in the hindlimb region of the LVN, depends upon the anatomical integrity of the cerebellum.

Action Potentials↗
PubMed1977

Locomotor recovery after unilateral hindlimb deafferentation in cats.

After hindlimb deafferentation, recovery of locomotor patterns may be distinguished from recovery of accurate movements. Cats were timed while crossing wide runways requiring that locomotion be present, and narrow runways which require that it also be accurate. Locomotion recovers soon after deafferentation and becomes almost normal in speed, although accuracy is still absent. This accuracy returns 10 days postoperatively. Ventral root afferents with cell bodies in dorsal root ganglia are unnecessary for recovery. Postural reflexes (and other non-topographic feedback) are used as cues for limb guidance after removal of that limb's topographic feedback. Anatomical experiments show that a thoracic root sprouts during the recovery period. This sprouting may increase the potency of postural reflexes. Although lower thoracic roots contribute to recovery, they are not essential. Ipsilateral descending system are essential, and represent the final common path for all recovery after deaffernting a hindlimb. Contralateral descending and afferent systems alone cannot mediate overground locomotion. Thus there is a difference between the systems which mediate overground locomotion and those used by animals in treadmill locomotion or with L-DOPA or clonidine or brain stem stimulation. The proposed mechanism underlying recovery of accurate locomotion is behavioral substitution which may be faciliated by collateral sprouting of relevant systems.

Animals↗
PubMed1977

The interaction between noradrenaline and 5-hydroxytryptamine in the isolated perfused rat hindlimb.

The vascular response to bolus injections of 5-hydroxytryptamine (5HT) over the range 0.01-10.0 microgram was measured in isolated perfused rat hindlimbs. The hindlimb vasculature displayed a vasoconstrictor response to 5HT, which was potentiated by the addition of 0.01 microgram/ml noradrenaline (NA) to the perfusate at all doses tested. The response to 5HT was also enhanced by the monoamine oxidase (MAO) inhibitor, tranylcypromine (0.05 mg/ml), suggesting that MAO located in the vascular wall is involved in the termination of the response to 5HT in the peripheral circulation. MAO inhibition abolishes the potentiation of 5HT by NA, indicating that this potentiation results from competition for MAO by both amines, leaving more amine intact to activate membrane receptors. Corticosterone (0.01 mg/ml), catecholamine extraneuronal uptake inhibitor, did not alter the response to 5HT, nor the increase of this response by NA, it thus appears that 5HT and NA have different membrane transport systems in the peripheral vasculature.

Animals↗
PubMed1977

Insulin-glucose dynamics during flow-through perfusion of the isolated rat hindlimb.

The dose-response relationship between glucose and insulin concentration and utilization in skeletal muscle was examined in hindlimbs of overnight fasted normal male rats. The perfusion was by flow-through technique utilizing an artificial perfusate containing beef erythrocytes. Glucose disappearance correlated significantly with insulin concentration. Insulin effect was detected within 5 minutes. When arterial glucose was 10 mM, glucose disappearance during maximal insulin stimulation was fivefold greater than glucose disappearance in the absence of insulin. A half-maximal effect occurred at an insulin concentration of 411 U per ml. Arteriovenous difference of immunoreactive insulin during a single passage thorugh the hindlimb averaged 16.7% over the range of 50 to 10,000 U per ml. In the presence or absence of insulin, glucose disappearance was positively correlated with glucose concentration up to a glucose concentration range of 30 to 45 mM. In this range and above glucose uptake averaged twelvefold above that observed for 5 mM glucose. When insulin (500 muU/ml) was added at any glucose concentration, glucose disappearance was augmented. The data thus indicate that rat skeletal muscle is a major site of insulin metabolism. In addition to the effect of insulin on glucose uptake by the muscle cell, glucose mass action appears to be quantitatively equipotent.

Animals↗
PubMedDate not supplied

Effects of histamine bolus injections and continuous infusions on the H1- and H2-receptors in the hindlimb vessels of the rabbit.

1. Hindlimb vascular resistance (HVR) was continuously measured after pharmacological block of the autonomic effectors in unanesthetized rabbits with previously implanted Doppler ultrasonic flowmeters. 2. Histamine bolus injections caused a dose-related short lived fall in HVR followed by a more sustained rise. The fall was due to H2-receptor stimulation (blocked by burimamide or metiamide) and the rise to H1-receptor stimulation (blocked by mepyramine). At the doses of histamine tested the magnitude of the H1-mediated vasoconstriction had a larger peak effect than the H2-mediated vasodilatation. 3. Histamine infusions up to 200 microgram kg-1 min-1 did not alter HVR significantly but both increases and decreases in HVR were observed after giving H2- or H1-antagonists, respectively. 4. From the double reciprocal plots of 1/peak HVR change and 1/dose of histamine the magnitude of the predicted H1- and H2-mediated peak HVR effects at large doses were the same. This suggested that the number of H1- and H2-receptors were similar in the hindlimb vascular bed, in agreement with the infusion data.

Animals↗
PubMed1978

Regeneration of symmetrical hindlimbs in larval salamanders.

The complete circle rule of the polar coordinate model of pattern regulation was tested for regenerating hindlimbs of Ambystoma larvae. The hindlimbs were made symmetrical in the circumference of either the thigh or the shank, and their ability to regenerate from both levels was observed. Thighs composed of two anterior halves failed to regenerate, whereas thighs composed of two posterior halves often regenerated distally complete, correspondingly symmetrical limbs; shanks composed of either two anterior or two posterior halves regenerated distally complete, correspondingly symmetrical limbs. These results are in contrast to what is predicted by the complete circle rule and suggest a modification of this rule.

Ambystoma↗