Cat Hind Leg Research Articles

Combined therapy with laser puncture and wheelchair aids in cases of paralysis of the cat's hind legs

A male cat named Kucil was brought by his owner to the Cimanggu Animal Clinic with complaints that the animal was unable to stand on its hind legs. The results of the physical examination showed that the cat Kucil was unable to walk, urinate, and defaecate, and paralysed in the tail and hind legs. Radiographic examination revealed a buildup of faeces in the colon and narrowing of the lumbar intervertebral spaces 5-6 and 6-7. The Cat was diagnosed with Intervertebral Disc Disease (IVDD). Acupuncture therapy using laser puncture at points ST-36, GB-34, BL-35, BL-54, SP-10, and Hua Tuo Jia-Ji, assisted by the use of a wheelchair, is an option for treating neurological disorders in this case. Improvement in the condition resulting from the therapy occurred after the 2nd therapy. To support the use of a wheelchair applied to the cat until the 4th therapy, the cat appears to be able to move its hind legs, and after the 9th therapy the cat appears to be able to walk.

Autonomous speed adaptation by a muscle-driven hind leg robot modeled on a cat without intervention from brain

This study aims to design a nervous system model to drive the realistic muscle-driven legs for the locomotion of a quadruped robot. We evaluate our proposed nervous system model with a hind leg simulated model and robot. We apply a two-level central pattern generator for each leg, which generates locomotion rhythms and reproduces cat-like leg trajectories by driving different sets of the muscles at any timing during one cycle of moving the leg. The central pattern generator receives sensory feedback from leg loading. A cat simulated model and a robot with two hind legs, each with three joints driven by six muscle models, are controlled by our nervous system model. Even though their hind legs are forced backward at a wide range of speeds, they can adapt to the speed variation by autonomously adjusting its stride and cyclic duration without changing any parameters or receiving any descending inputs. In addition to the autonomous speed adaptation, the cat hind leg robot switched from a trot-like gait to a gallop-like gait while speeding up. These features can be observed in existing animal locomotion tests. These results demonstrate that our nervous system is useful as a valid and practical legged locomotion controller.

Autonomous gait modulation in a cat hind leg simulation model based on the spinal nervous system

Autonomous gait modulation in a cat hind leg simulation model based on the spinal nervous system

Autonomous Speed Adaptation by a Simulated Cat's Hind Legs and Evaluation of the Controller

Autonomous Speed Adaptation by a Simulated Cat's Hind Legs and Evaluation of the Controller

Leg mechanics contribute to establishing swing phase trajectories during memory-guided stepping movements in walking cats: a computational analysis.

When quadrupeds stop walking after stepping over a barrier with their forelegs, the memory of barrier height and location is retained for many minutes. This memory is subsequently used to guide hind leg movements over the barrier when walking is resumed. The upslope of the initial trajectory of hind leg paw movements is strongly dependent on the initial location of the paw relative to the barrier. In this study, we have attempted to determine whether mechanical factors contribute significantly in establishing the slope of the paw trajectories by creating a four-link biomechanical model of a cat hind leg and driving this model with a variety of joint-torque profiles, including average torques for a range of initial paw positions relative to the barrier. Torque profiles for individual steps were determined by an inverse dynamic analysis of leg movements in three normal cats. Our study demonstrates that limb mechanics can contribute to establishing the dependency of trajectory slope on the initial position of the paw relative to the barrier. However, an additional contribution of neuronal motor commands was indicated by the fact that the simulated slopes of paw trajectories were significantly less than the observed slopes. A neuronal contribution to the modification of paw trajectories was also revealed by our observations that both the magnitudes of knee flexor muscle EMG bursts and the initial knee flexion torques depended on initial paw position. Previous studies have shown that a shift in paw position prior to stepping over a barrier changes the paw trajectory to be appropriate for the new paw position. Our data indicate that both mechanical and neuronal factors contribute to this updating process, and that any shift in leg position during the delay period modifies the working memory of barrier location.

Sensory regulation of stance-to-swing transition in generation of adaptive human walking: A simulation study

In this paper, we investigated sensory mechanisms to regulate the transition from the stance to swing phases in the generation of adaptive human bipedal walking based on a neuromusculoskeletal model. We examined the contributions of the sensory information from the force-sensitive afferents in the ankle extensor muscle and from the position-sensitive afferents from the hip, inspired by a neuro-mechanical simulation for the stepping of the hind legs of cats. Our simulation results showed that the sensory signals related to the force in the ankle extensor muscle make a larger contribution than sensory signals related to the joint angle at the hip to produce robust walking against disturbances, as observed in the simulation results of cat locomotion. This suggests that such a sensorimotor mechanism is a general property and is also embedded in the neuro-control system of human bipedal walking.

System identification of muscle–joint interactions of the cat hind limb during locomotion

Neurophysiological experiments in walking cats have shown that a number of neural control mechanisms are involved in regulating the movements of the hind legs during locomotion. It is experimentally hard to isolate individual mechanisms without disrupting the natural walking pattern and we therefore introduce a different approach where we use a model to identify what control is necessary to maintain stability in the musculo-skeletal system. We developed a computer simulation model of the cat hind legs in which the movements of each leg are produced by eight limb muscles whose activations follow a centrally generated pattern with no proprioceptive feedback. All linear transfer functions, from each muscle activation to each joint angle, were identified using the response of the joint angle to an impulse in the muscle activation at 65 postures of the leg covering the entire step cycle. We analyzed the sensitivity and stability of each muscle action on the joint angles by studying the gain and pole plots of these transfer functions. We found that the actions of most of the hindlimb muscles display inherent stability during stepping, even without the involvement of any proprioceptive feedback mechanisms, and that those musculo-skeletal systems are acting in a critically damped manner, enabling them to react quickly without unnecessary oscillations. We also found that during the late swing, the activity of the posterior biceps/semitendinosus (PB/ST) muscles causes the joints to be unstable. In addition, vastus lateralis (VL), tibialis anterior (TA) and sartorius (SAT) muscle-joint systems were found to be unstable during the late stance phase, and we conclude that those muscles require neuronal feedback to maintain stable stepping, especially during late swing and late stance phases. Moreover, we could see a clear distinction in the pole distribution (along the step cycle) for the systems related to the ankle joint from that of the other two joints, hip or knee. A similar pattern, i.e., a pattern in which the poles were scattered over the s-plane with no clear clustering according to the phase of the leg position, could be seen in the systems related to soleus (SOL) and TA muscles which would indicate that these muscles depend on neural control mechanisms, which may involve supraspinal structures, over the whole step cycle.

Computer Simulation of Stepping in the Hind Legs of the Cat: An Examination of Mechanisms Regulating the Stance-to-Swing Transition

Physiological studies in walking cats have indicated that two sensory signals are involved in terminating stance in the hind legs: one related to unloading of the leg and the other to hip extension. To study the relative importance of these two signals, we developed a three-dimensional computer simulation of the cat hind legs in which the timing of the swing-to-stance transition was controlled by signals related to the force in ankle extensor muscles, the angle at the hip joint, or a combination of both. Even in the absence of direct coupling between the controllers for each leg, stable stepping was easily obtained using either a combination of ankle force and hip position signals or the ankle force signal alone. Stable walking did not occur when the hip position signal was used alone. Coupling the two controllers by mutual inhibition restored stability, but it did not restore the correct timing of stepping of the two hind legs. Small perturbations applied during the swing phase altered the movement of the contralateral leg in a manner that tended to maintain alternating stepping when the ankle force signal was included but tended to shift coordination away from alternating when the hip position signal was used alone. We conclude that coordination of stepping of the hind legs depends critically on load-sensitive signals from each leg and that mechanical linkages between the legs, mediated by these signals, play a significant role in establishing the alternating gait.

Use-dependent gain change in the reflex contribution to extensor activity in walking cats

Denervation of the synergists of the medial gastrocnemius (MG) muscle in the cat hind leg results in a progressive increase in the magnitude of burst activity in the MG muscle during walking. The increase in burst magnitude is associated with an increase in the slope of the relationship between the magnitude of individual MG bursts and the amplitude of ankle flexion during stance. This finding is consistent with the hypothesis that the increase in MG burst magnitude is due to an increase in gain of reflex pathways reinforcing the activation of MG. The increase in slope is use-dependent since it was not observed when the leg was released from a cast that immobilized the leg for 6 days.

Third-order reverse correlation analysis of muscle spindle primary afferent fiber responses to random muscle stretch.

The response of primary muscle spindle afferent fibers to muscle stretch is nonlinear. Now spindle responses (trains of action potentials) to band-limited Gaussian white noise length perturbations of the gastrocnemius muscles (input signal) are described in cats. The input noise upper cutoff frequency was clearly above the frequency range of physiological length changes in cat hindleg muscles. The input-output relation was analyzed by means of peri-spike averages (PSAs), which could be shown to correspond to the kernels of Wiener's white noise approach to systems identification. The present approach (the reverse correlation analysis) was applied up to the third order. An experiment consisted of two recordings: one (the source recording) to determine PSAs and the other (the test recording) to provide an input signal for predicting responses. The predictions of different orders were compared with the actual neuronal response (the observation) of the test recording. Four different approximation procedures were developed to adapt prediction and observation and to determine weighting factors for the predictions of different orders. The approximations also yielded the value of the power density P of the input noise signal: at a variety of stimulus parameters, P from approximations had the same magnitude as P determined directly from the input signal amplitude spectrum. The prediction of a sequence of action potentials improved the higher the order of components. 37 of 42 action potentials of a test recording (the observation) could be confidently predicted from PSAs or kernels. Compared with the size of the linear first-order prediction curve, the relative sizes of the second and third-order prediction curves were: 1.0:0.47:0.26.

Vigilance as Metaphor: The Foreign Policy of Ronald Reagan

level we are mute. This silence is particularly damaging for an assessment of the foreign policy of Ronald Reagan, as his strength is precisely at this general level; his knowledge of particulars is almost universally derided. The most serious consequence of our inability to abstract from the specific issues is our inability to predict Reagan's future actions. Mixed signals are not unusual in the conduct of American foreign policy. But lacking a metaphor, we cannot evaluate and weigh these signals in the Reagan administration. For example, let us consider U.S. foreign policy in Central America. There is an uneasiness about Reagan's next step in Nicaragua: Will he invade? If we choose to give weight to the police action in Grenada and the shrill rhetoric, we are led to believe that invasion is likely. If we emphasize the handling of the crisis in Lebanon and the electioneering speeches of the new Reagan, however, we are led to believe that invasion is unlikely. Which are indicative of Reagan's foreign policy: signs of intervention or signs of caution? Reagan and his foreign policy staff have delivered speeches explaining their actions and philosophies, but these are of limited use. Long explanations are easily misinterpreted, contradicted, forgotten. Consider long explanations of the threat of communism in Indochina. Without an image the threat would have been distant and irrelevant—a matter for experts. But remind us of the dominoes of our childhood, collapsing ever faster onto each other until all had fallen, and we could understand. In 1. Quoted in Noted with Pleasure, The New York Times Book Review, 25 November 1984, 47, from Robert Frost: Poetry and Prose ed. E. C. Lathem and L. Thompson (New York: Holt, Rinehart and Winston, 1984). VIGILANCE: THE FOREIGN POLICY OF RONALD REAGAN 135 the context of that metaphor we could begin to protest against the war: Even if we did not know where Laos or Cambodia were, we could assert loudly that we rejected the metaphor. Consider as well the image of containment, a less vivid but not obscure metaphor. It was easy for us to imagine the Soviet Union as a dehumanized enemy bent on expansion, and easier still to rally behind the forcible containment of these communists. The Cold War was also an accessible metaphor, particularly while the hot war was vividly recollected. The strength of these metaphors is not just their accessibility, but also their generality. They have described and clarified widely diverse events and strategies. When we consider the usefulness and even the comfort of these terms, it becomes all the more evident that we are now groping through four more years of foreign policy that is post-detente, post-cold war, and post-containment. It is a policy for which we have no language. But let us think of the images of Reagan's foreign policy. The image of the United States that Reagan projects is a strong, proud, rejuvenated America whose parallel with Reagan's physical person is remarkable, a parallel strengthened by his recovery from the assassination attempt. This strong nation is on guard, surrounded by hostile forces: Russians to the east and west, Cubans and Sandinistas to the south, terrorists abounding. We must be wary. Thus we talk tough to the Russians; we criticize negotiations; we reject a communist regime in Grenada. But we don't want to become overextended; we are cautious. We make threatening noises in Lebanon, but pull out before the costs are too high. We dislike the Sandinistas, but we send in the cia, not the marines. The image reminds one of a cat who is ready to pounce. The cat crouches, every muscle tense, eyes and ears alert to any disruption. Sometimes the tension mounts, and the cat's hind legs quiver (the evil empire speech); sometimes a paw whips out and catches a bug (there goes Grenada); sometimes the cat takes a slithered step forward (missiles in Europe) and sometimes a step back (withdrawal from Lebanon). The cat is sending signals: Don't touch me. I am watching your every movement, ready to fight. The cat is strong, muscular, tense. Vigilance is the metaphor that describes this image. Ronald Reagan's foreign policy is the policy of vigilance. Vigilance is an apt metaphor because it is accurate, accessible, and flexible. It extends the previous metaphors of containment and the cold war, and its definition provides a useful lens through which to analyze Reagan's foreign policy. vigilance: (1) watchfulness in respect of danger or hazard; (2) readiness or alertness, especially to respond to stimuli.

Temperature dependence of isometric contractions of cat fast and slow skeletal muscles.

The influence of temperature (range 38-20 degrees C) on the isometric contractions of flexor digitorum longus (fast-twitch) and soleus (slow-twitch) muscles of the cat hind leg was examined in situ and with supramaximal nerve stimulation. The maximum tetanic tension decreased by 5-7% on cooling from 38 to 27 degrees C and by about 17% on further cooling to 20 degrees C. The results were similar between the two muscles. The twitch tension increased by 100% in flexor digitorum longus and decreased by about 40% in soleus when the temperature was lowered from 38 to 20-24 degrees C. The results are compared with those reported for fast- and slow-twitch muscles of the rat.

Innervation patterns of cutaneous hair receptors in cat

Cat hair receptors were studied to determine whether they could be distinguished by the following receptive field characteristics: thickness of innervated guard hairs, distance between innervated follicles and receptive field size. Initially the receptors were classified as G 1, GI, G 2 or D on the basis of their velocity requirements for excitation, their degree of linear directionality, their vibrational sensitivity, and whether they were activated by movement of down hairs. It was found that the thickest guard hairs on the posterior aspect of a cat's hindleg were usually 4–5 times thicker than the thinnest guard hairs from the same area and that G 1, GI and G 2 neurons innervated the full range of guard hair thicknesses available. Although there was a tendency for thicker guard hairs to be more heavily innervated, none of the neurons studied innervated thick guard hairs exclusively. While movement of the down hair and most guard hairs within D-mechanoreceptive fields easily evoked activity, a few guard hairs were regularly found for which mechanical displacement did not elicit a discharge even though they were well within the receptive field. Receptive field sizes and nearest neighbor distances between innervated follicles were smaller for D than for G 1, GI and G 2 receptors and greater for G 1 than GI and G 2 receptors.

Histochemical evidence for sympathetic innervation of hair receptor afferents in cat skin

The goal of the present study was to demonstrate histochemically fine catecholamine-containing sympathetic nerve fibers which might be associated with hair receptor afferent fibers in cat skin. Positive results would be consistent with the hypothesis that the sympathetically mediated desensitization of hair afferents, observed in this an earlier studies, is mediated by direct neurotransmitter release onto the afferent fibers. Activity in single primary afferent fibers was recorded electrophysiologically during mechanical stimulation of hairs and electrical stimulation of the lumbar sympathetic trunk in anesthetized cats. The mechanical threshold for activation was seen to increase markedly during low-frequency sympathetic stimulation. Fresh-frozen sections of skin from cat hindleg were treated with glyoxylic acid for detection of fluorescent catecholamines. Fluorescent fibers were observed in association with hair follicles as well as with arterioles and arrector-pili muscles. Subsequent silver staining of the identical skin sections revealed that the fine catecholamine-containing fibers located near hair follicles were closely associated with hair receptor afferent fibers. The results of hair receptor sensitivity is mediated by direct neurotransmitter release onto the afferent fibers.

Phosphoenzyme decomposition in sarcoplasmic reticulum isolated from cat caudofemoralis, tibialis and soleus

Decomposition of phosphoenzyme (E ∼ P) in sarcoplasmic reticulum isolated from caudofemoralis, tibialis and soleus of cat hind leg skeletal muscles was studied under various conditions of monovalent cations. In the presence of Li +, Na + and K + chosen for E ∼ P formation and decomposition after quenching of E ∼ P with EGTA, E ∼ P in the caudofemoralis and tibialis sarcoplasmic reticulum decomposed faster than that in the soleus sarcoplasmic reticulum. Quenching the E ∼ P formation with EGTA and ADP revealed that 30–40% of the total E ∼ P formed in all types of sarcoplasmic reticulum was ‘ADP sensitive’. Decomposition of the remaining E ∼ P in caudofemoralis and tibialis sarcoplasmic reticulum was enhanced by ADP, which resulted in a multiphasic decomposition pattern. A larger portion of the remaining E ∼ P in the soleus sarcoplasmic reticulum, on the other hand, decomposed in a monophasic manner and was not significantly influenced by ADP. The data on E ∼ P decomposition clearly differentiate between the fast and slow muscle types.

Carbonic anhydrase activity of the cat hind leg.

The accessibility of tissue carbonic anhydrase to plasma was studied in five surgically isolated cat hind legs. After the leg was skinned and the paw circulation occluded with a tourniquet, it was perfused with a solution that contained neither red cells nor carbonic anhydrase. Solutions containing either H14CO3- or 14CO2 were injected with 125I-albumin, 22Na+, and 3H2O into the femoral artery and the concentrations of each were measured in the femoral venous outflow. Under control circumstances the outflow patterns of H14CO3- and 14CO2 were very similar. However, after carbonic anhydrase inhibition with 20 mg/l acetazolamide in the perfusion solution, the initial exchange of H14CO3- ("extraction") was greatly decreased, whereas the extraction of 14CO2 was slightly increased. Because there was insignificant carbonic anhydrase activity in the venous outflow, these data suggest the presence of carbonic anhydrase at a readily accessible site, possibly bound to the endothelial surface. In this location it would promote CO2 exchange and minimize disequilibrium between plasma HCO3- and CO2.

Miniature stimulator for chronic animals

A small lightweight pulse train generator is described. Train frequency and duration and pulse frequency and duration are continuously variable over a range that is suitable for many types of nerve stimulation experiments. Complete electrical specifications and schematics are shown. Also presented are the changes in contraction time of the cat hind leg muscles after 6-week chronic stimulation of the sciatic nerve. The stimulator, with batteries which are sufficient for more than six weeks operation, is small enough to be mounted on cats.

Influence of temperature on the characteristics of summation of isometric mechanical responses of mammalian skeletal muscle

Characteristics of summation of isometric mechanical responses elicited by two supramaximal nerve stimuli were examined at different temperatures (18 to 38°C) in a fast twitch (flexor digitorum longus) and a slow twitch (soleus) muscle, in situ, in the cat hind leg. At 37 to 38°C, both muscles developed a peak tension that was more than twice the twitch tension when a second stimulus was applied shortly after the first. The rate of rise of tension in such a summated response was also about, or more than, twice that of the twitch tension, and the time to peak tension was about 1.5 times the time to peak of the twitch. The peak tension in summated responses decreased with increasing the stimulus interval so that, when the interval was equal to the time to peak twitch, the tension developed was significantly less. Cooling significantly alters these characteristics in the fast twitch muscle, so that, at 20 to 22°C, the tension, the rate of rise of tension, and the time to peak tension enhancement produced by a second stimulus are markedly reduced; little or no change in the characteristics is seen with cooling of the slow twitch muscle. These results are examined in the light of some observations made on the pattern of summation in frog sartorius muscle at different temperatures (2 to 28°C). Cooling significantly increases the degree of activation occurring during the twitch in the fast twitch muscle fibers, whereas it has little or no effect on the degree of mechanical activation in the slow twitch muscle fibers. Furthermore, the results suggest that the tension, the rate of rise of tension, and, perhaps the time to peak tension of the isometric twitch in both the fast twitch and the slow twitch muscle fibers at 37 to 38°C are limited by the degree of mechanical activation and that a second stimulus applied shortly after the first can greatly overcome the effect of that limitation.

Lymphatic patterns of cats infected with Brugia malayi and streptococcus

Approximately 50% of the hind legs of cats infected with Brugia malayi and insulted with a beta haemolytic streptococcus became elephantoid in appearance after four to six weeks. This condition was found to be reversible. Collateral lymphatic vessels were seen by lymphography in most of the Brugia-streptococcus-infected legs. The popliteal draining systems in two of three cats, which harboured no worms, appeared normal by lymphography at 18 weeks.

Studies on the possible contribution of a peripheral presynaptic action of clonidine and dopamine to their vascular effects under in vivo conditions

The functional consequences of drug-induced stimulation under in vivo conditions of alpha-adrenoceptors and dopamine receptors at vascular adrenergic nerve endings (presynaptic receptors) was studied in the autoperfused hindquarters or hindlegs of cats anaesthetized with urethane. The changes in perfusion pressure in response to electrical stimulation of the lumbar sympathetic chain were taken as a measure of noradrenaline release from the vascular adrenergic nerves. Presynaptic inhibitory alpha-adrenoceptors and dopamine receptors were activated by clonidine and dopamine, respectively. According to in vitro experiments these two drugs are more potent stimulants of peripheral presynaptic than postsynaptic receptors. The lowest frequency of stimulation of the lumbar sympathetic chain which yielded a reproducible pressor response was 4 HZ for the autoperfused hindquarters and 1 HZ for the hindlegs; Clonidine was tested over a wide dose range (1-100 mug/kg i;v). A reduction of the stimulation-induced pressor response in the autoperfused hindquarters or hindlegs was observed only after the rather high dose of 100 mug/kg of clonidine. The inhibition was marked at low frequencies of stimulation (1-4 HZ) and weak or absent at high frequencies (16 and 32 HZ). The dose of clonidine (100 mug/kg) which proved to be effective at presynaptic receptors produced a transient increase in blood pressure and in perfusion pressure of the hindquarters and hindlegs and virtually abolished spontaneous sympathetic nervous activity. In spinal cats, the clonidine-induced increases in blood pressure and perfusion pressure were very pronounced and of rather long duration. Thus, under in vivo conditions clonidine showed no selectivity for presynaptic alpha-adrenoceptors in a blood-perfused vascular bed, and its presynaptic action was negligible as compared to its powerful central sympatho-inhibitory effect. Dopamine was constantly infused into the auto-perfused hindquarters or hindlegs at increasing rates until a vasoconstriction due to stimulation of vascular (postsynaptic) alpha-adrenoceptors occurred. The monoamine did not inhibit the stimulation-induced increases in perfusion pressure of the autoperfused hindquarters or hindlegs and, thus, an effect on presynaptic receptors was not found. The results underscore the importance of in vivo experiments for assessing the therapeutic significance of drug-induced stimulation of presynaptic receptors.