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PubMed1977

A comparison of visual pathways in Boston and Midwestern Siamese cats.

A genetic mutation in Siamese cats causes retinogeniculate fibers representing roughly the first 20 degrees of ipsilateral visual field in each eye to cross aberrantly in the optic chiasm and terminate in the wrong lateral geniculate nucleus (LGN). Previous investigations have shown that in the visual cortex this extra representation of ipsilateral visual field can be organized into one pattern in Boston Siamese cats, another in Midwestern. This finding was confirmed here. The possibility that the organization of the LGN might account for these two patterns was studied using combined anatomical and physiological methods. On the basis of microelectrode recordings from the visual cortex, 11 out of the 12 Siamese cats included here were Boston cats; one was Midwestern. The distribution of retinogeniculate terminals was examined in each cat using autoradiographic techniques following an eye-injection of 3H-proline. Overall, the LGN organization in Boston cats was similar to that of Midwestern: both lateral and medial normal segments of lamina A1 (mnA1) were present. In Boston cats, however, the mnA1 was remarkably small and shifted ventromedially in the nucleus to allow for the fusion between the medial borders of lamina A and the abnormal segment of A1. In the Midwestern cat this fusion was not apparent and the medial normal segment of A1 was significantly larger. These differences in organization of the LGN are consistent with those seen at the level of the visual cortex in Midwestern and Boston Siamese cats. It was not possible, however, to relate them clearly to the characteristic strabismus of these animals.

Animals↗
PubMed1977

Anatomy of interhemispheric connections in the visual system of Boston Siamese and ordinary cats.

In Siamese cats, previous studies have shown that a genetic mutation causes retinogeniculate fibers in each eye which arise from the temporal retina representing the 20 degrees of ipsilateral visual field adjacent to the vertical meridian to cross aberrantly in the optic chiasm, thereby terminating in the wrong lateral geniculate nucleus. The abnormality is expressed subsequently at the level of the visual cortex. This paper presents anatomical evidence that the pattern of commissural visual connections in the "Boston" variety of Siamese cat also is highly abnormal in comparison to that of ordinary cats. The topographical distribution of neurons supplying visual fibers to the splenium of the corpus callosum was studied in Boston Siamese and ordinary cats using the method of retrograde transport of horseradish peroxidase (HRP) following localized cortical injections made through a recording micropipette. In ordinary cats, after an HRP injection at the border between cortical areas 17 and 18, which represents the vertical meridian of the visual field, HRP-labeled cells in areas 17 and 18 of the opposite hemisphere were found only immediately adjacent to the 17-18 border, thus confirming the results of previous investigations. In Boston Siamese cats, the border represents a region in the ipsilateral visual field roughly 20 degrees away from the vertical meridian, and the vertical meridian representation is displaced to sites within areas 17 and 18 proper. When HRP was injected at the 17-18 border, labeled cells in the opposite hemisphere were located well within area 17 near the suprasplenial sulcus, and also well within area 18; few labeled cells were found at the 17-18 border. When an HRP injection was placed at the vertical meridian representation, again few HRP-labeled cells were found at the opposite 17-18 border, but instead most were found in area 17 slightly medial to the border, and in area 18 slightly lateral to it. Thee findings were complemented in an autoradiographic study in which orthograde transport of tritiated proline after a localized cortical injection was used to demonstrate the distribution of callosal terminals. Thus the pattern of callosal connections revealed in Boston Siamese cats, although anatomically different from that of ordinary cats, was nevertheless consistent with the proposal that cortical sites representing similar visual field coordinates in each hemisphere are appropriately interconnected via the corpus callosum. The laminar distribution of callosal connections was examined briefly. Layer III pyramidal cells of areas 17 and 18 supplied the majority of terminals to the opposite 17-18 border. Pyramidal cells of Layers II and VI, and Layer IVa in area 18, made a smaller contribution. In areas 17 and 18, the same cortical layers (II, III, and VI; and IVa in 18) were again the major sites of callosal termination. A clear projection to the base of layer I was also noted. The laminar distribution of callosal connections in ordinary and Boston Siamese cats were not substantially different.

Agenesis of Corpus Callosum↗
PubMed1978

The nasotemporal division of retina in the Siamese cat.

By sectioning one optic tract in Siamese kittens and allowing sufficient time for the affected ganglion cells to degenerate and disappear, we have obtained maps of the distribution of ipsi- and contralaterally projecting ganglion cells in the retina of the Siamese cat. As previous work predicted, many ganglion cells in the Siamese cat retina project contralaterally which, in the normally pigmented cat, would project ipsilaterally. The transition from the pattern of projection typical of nasal retina (all contralateral) to that typical of temporal retina (most ipsilateral) is much more gradual in the Siamese cat than in the normally pigmented cat, and is centred 1.7-3 mm temporal to the area centralis, instead of at the area centralis. In the Siamese cat only a few ganglion cells at the area centralis project ipsilaterally, as against nearly 50% in the normally pigmented cat. The proportion of ipsi-projecting cells reaches the 50% level 1.7-3.0 mm into temporal retina, and overall the zone of transition may be several millimetres wide, as against about 0.2-0.5 mm in in the normall pigmented cat. Evidence is presented that the degree of the abnormality of nasotemporal division varies between individual Siamese cats and that the abnormality is more severe among large or "giant" cells than among the population as a whole.

Animals↗
PubMed1991

The cells of origin of the spinohypothalamic tract in cats.

Various cutaneous and visceral stimuli alter the discharge rates of neurons in the hypothalamus. Changes in the activity of hypothalamic neurons are thought to play important roles in eliciting neuroendocrine, autonomic, and affective responses to somatosensory and visceral stimuli. Information from peripheral structures has been considered generally to reach the hypothalamus via multisynaptic ascending pathways. Recently, a direct projection from the spinal cord to the hypothalamus was demonstrated in rats. The goal of this study was to determine whether a similar projection exists in cats. Either wheat germ agglutinin conjugated to horseradish peroxidase, a mixture of this tracer and the B subunit of cholera toxin conjugated to horseradish peroxidase, or fast blue was injected into the hypothalamus of cats. Injections were centered in the hypothalamus in seven cats and did not spread to the thalamus, zona incerta or midbrain. After these injections, retrogradely labeled neurons were observed bilaterally in each of the 17 spinal segments that were examined. A total of approximately 400-500 labeled neurons was observed in alternate sections through these segments in the most effective cases. Roughly 70% of the labeled neurons were located contralaterally. Labeled neurons were found predominantly in the deep dorsal horn, the intermediate zone/ventral horn and in the area surrounding the central canal. A few were also noted in the superficial dorsal horn. The first and second sacral segments contained the largest numbers of retrogradely labeled neurons in the spinal cord. The number of spinohypothalamic tract neurons observed in this study in cats was roughly an order of magnitude smaller than that previously reported for rats. This finding suggested either that the spinohypothalamic tract is relatively small in cats or that our tracing techniques did not label many spinohypothalamic tract neurons in cats. To test the sensitivity of one of our tracing techniques, control injections of wheat germ agglutinin conjugated to horseradish peroxidase that filled the ventrobasal thalamus were made in two cats. In both cases, thousands of spinal cord neurons were labeled. In summary, our results indicate that a spinohypothalamic tract exists in cats. However, our findings also suggest that the total number of spinohypothalamic tract neurons in cats may be an order of magnitude smaller than it is in rats.

Animals↗
PubMed1979

Enhancement of feline leukemia virus-induced leukemogenesis in cats exposed to methylnitrosourea.

The effect of methylnitrosourea (MNU), a potent resorptive carcinogen, was evaluated for its influence on the susceptibility of adult cats to infection and induction of oncornavirus disease by feline leukemia virus (FeLV). Young adult cats at an age previously demonstrated to be highly resistant to FeLV, were injected intravenously with moderately toxic doses (15-20 mg/kg) of MNU alone or with infections FeLV (Rickard strain). Following exposure to virus and chemical, cats were monitored for antibody to the feline oncornavirus-associated cell membrane antigen (FOCMA), viremia by direct infectivity and the presence of gsa in peripheral blood leukocytes, and for toxic effects of MNU by hemogram analyses on peripheral blood. Of 8 cats injected with MNU + FeLV, 6 developed persistent viremia, 5 of which became debilitated from thymic lymphoma. Only 1 of 6 non-MNU-treated and infected cats of the same age became transiently viremic. FOCMA antibody development was markedly depressed in MNU + FeLV inoculated cats compared with cats inoculated with FeLV alone. Results show that MNU was apparently responsible for the obliteration of age-related susceptibility in cats to FeLV infection and induction of FeLV-related disease, and suggest that in nature exposure to toxic chemical carcinogens may act as factors which determine susceptibility to feline oncornaviruses in the cat.

Age Factors↗
PubMed1997

Persistence and evolution of feline coronavirus in a closed cat-breeding colony.

Feline coronavirus (FCoV) persistence and evolution were studied in a closed cat-breeding facility with an endemic serotype I FCoV infection. Viral RNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in the feces and/or plasma of 36 of 42 cats (86%) tested. Of 5 cats, identified as FCoV shedders during the initial survey, 4 had detectable viral RNA in the feces when tested 111 days later. To determine whether this was due to continuous reinfection or to viral persistence, 2 cats were placed in strict isolation and virus shedding in the feces was monitored every 2-4 days. In 1 of the cats, virus shedding continued for up to 7 months. The other animal was sacrificed after 124 days of continuous virus shedding in order to identify the sites of viral replication. Viral mRNA was detected only in the ileum, colon, and rectum. Also in these tissues, FCoV-infected cells were identified by immunohistochemistry. These findings provide the first formal evidence that FCoV causes chronic enteric infections. To assess FCoV heterogeneity in the breeding facility and to study viral evolution during chronic infection, FCoV quasispecies sampled from individual cats were characterized by RT-PCR amplification of selected regions of the viral genome followed by sequence analysis. Phylogenetic comparison of nucleotides 7-146 of ORF7b to corresponding sequences obtained for independent European and American isolates indicated that the viruses in the breeding facility form a clade and are likely to have originated from a single founder infection. Comparative consensus sequence analysis of the more variable region formed by residues 79-478 of the S gene revealed that each cat harbored a distinct FCoV quasispecies. Moreover, FCoV appeared to be subject to immune selection during chronic infection. The combined data support a model in which the endemic infection is maintained by chronically infected carriers. Virtually every cat born to the breeding facility becomes infected, indicating that FCoV is spread very efficiently. FCoV-infected cats, however, appear to resist superinfection by closely related FCoVs.

Amino Acid Sequence↗
PubMed1992

The effect of dietary supplementation with cysteic acid on the plasma taurine concentration of cats maintained on a taurine-restricted diet.

The biochemical impairment in the taurine anabolic pathway of the cat has not yet been fully elucidated; however, a number of key enzymes are known to have reduced activity in the cat compared to the rat. There are a series of possible routes resulting in the formation of taurine, one of which is the decarboxylation of cysteic acid. The aim of this study was to investigate the effect of cysteic acid, as a precursor, on the circulating concentration of taurine. A group of twelve adult cats was fed a basal, canned diet containing 0.22 g taurine/kg fresh weight for a period of eighty-four days. The diet was supplemented with 2.0 g/kg fresh weight L-cysteic acid on day fifteen through fifty six and plasma taurine concentration was measured every two weeks throughout the study. The results showed that when the dietary intake of taurine was inadequate to maintain the plasma concentration above 40 mumol/L, the addition of L-cysteic acid to the diet gave rise to an increase in plasma taurine concentration in some cats. Eight of the twelve cats showed a significant rise in plasma taurine after dietary supplementation for six weeks (52.0 +/- 22.3 vs 212.4 +/- 97.9 mumol/L, p less than 0.01) and a subsequent decrease in plasma levels when the cysteic acid was withdrawn (65.6 +/- 37.1 mumol/L). The other four cats showed no significant rise in plasma taurine after six weeks supplementation (13.5 +/- 4.2 vs 35.5 +/- 19.4 mumol/L, ns). However, withdrawal of the cysteic acid resulted in a subsequent decrease in circulating levels of taurine (11.8 +/- 1.5 mumol/L, ns). These data indicate that the addition of cysteic acid to a taurine-restricted, canned diet will, in some cats, result in the biosynthesis of taurine. The plasma taurine concentration of the remaining cats, although not apparently increasing significantly, was maintained at a slightly higher constant level until the cysteic acid was withdrawn. These results suggest that cats are able to synthesise taurine via an alternative pathway utilising L-cysteic acid as a precursor, although the efficiency of this process differs considerably among individual animals.

Animal Nutritional Physiological Phenomena↗
PubMed1993

The role of the lateral suprasylvian visual cortex of the cat in object-background interactions: permanent deficits following lesions.

The contribution of the lateral suprasylvian cortex to pattern recognition was studied by behavioural detection experiments in combination with bilateral lesions of different parts of the lateral suprasylvian areas (LSA) and area 7 in seven cats. In a two-alternatives forced choice task the cats had to discriminate simple outline patterns which were additively superimposed on a structured visual background made up of broadband Gaussian noise. For various stimulus conditions (moving or stationary patterns and/or background) the detection probability (PD) of the cats was measured as a function of the signal-to-noise ratio (S/N). Each cat was tested before and after the lesion. Four different types of lesion could be distinguished depending on their extent: (1) lesion of parts of the (LSA); (2) lesion of parts of the LSA with undercutting of areas 17, 18 and 19; (3) lesion of area 7; (4) lesion of area 7 and parts of the LSA. 1. We found that a large bilateral lesion of the LSA led to significant deficits in all test situations which were dependent on the existence of relative velocity of moving patterns against a structured background. The ability of the cats to discriminate simple outline patterns which were kept stationary was not reduced. On the contrary, when they were tested with stationary and moving patterns on unfocused (empty) backgrounds, we found, to our great surprise, that the performance of the lesioned cats was significantly improved compared with intact animals. As these lesioned cats had no deficits with moving patterns on a uniformly grey background, we conclude that the deficits with the moving patterns must have been caused by interactions between patterns and background, and not by movement of a pattern per se. 2. As soon as the lesion of the LSA was extended by a bilateral undercutting of areas 17, 18 and 19 we found very severe deficits in all test situations, regardless of whether the patterns were moving or kept stationary, or whether they were superimposed on a background or not. The most substantial deficits occurred when the patterns were moving on a stationary background. In these situations the cats were no longer able to reach the 84% correct criterion. Again, the cats were able to reach criterion with moving patterns on a uniformly grey background indicating that this deficit is probably caused by the interaction of patterns and background and not by motion of the patterns per se.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1982

Formation of functional synapses in the adult cat red nucleus from the cerebrum following cross-innervation of forelimb flexor and extensor nerves. II. Analysis of newly appeared synaptic potentials.

The effects of cross-innervation of peripheral flexor and extensor nerves on the time course and properties of red nucleus (RN) neurons were studied in adult cats. The time course of corticorubral unitary EPSPs was examined. In operated cats, RN neurons innervating upper spinal segments (C-cells) manifested corticorubral unitary EPSPs with shorter time-to-peak and larger amplitude than in normal cats. The mean amplitude of these EPSPs was 0.41 +/- 0.11 mV; the mean time-to-peak was 1.14 +/- 0.51 ms (n = 18). These values differ from normal cats (0.33 +/- 0.09 mV, and 2.68 +/- 0.61 ms, n = 22). RN neuron membrane properties were examined in cross-innervated cats. The main time constant was 5.2 +/- 0.7 ms (n = 10), the shorter equalizing time constant, 0.69 +/- 0.19 ms (n = 10), the input resistance, 2.5 +/- 0.8 M omega. These values were not significantly different from those of normal cats. The electrotonic length was 1.2 (n = 10), somewhat larger than in normal cats. The number of converging interpositorubral synapses, estimated in eight cells from cross-innervated cats, ranged from 37 to 57. This was not significantly different from normal cats, and indicated that there is no large-scale degeneration of interpositorubral synapses after cross-innervation. These results suggest that sprouting and formation of functional synapses occur after cross-innervation of peripheral flexor and extensor nerves.

Animals↗
PubMed1987

The morphology of retinogeniculate X- and Y-cell axonal arbors in dark-reared cats.

The cat's retinogeniculate pathway, immature at birth, develops physiologically and anatomically over the first three postnatal months. Visual deprivation from birth interferes with this maturation. Thus, monocular eye lid suture from birth leads to pronounced abnormalities in the morphology of retinogeniculate terminations and geniculate neurons, and to a reduction in the proportions of Y-cells recorded physiologically in the lateral geniculate nucleus (e.g. see Sherman and Spear 1982). This "loss" of geniculate Y-cells could possibly be due to reduced retinogeniculate Y-cell terminations and expanded X-cell terminations in the A-laminae (Sur et al. 1982), so that many geniculate cells that normally receive retinal Y-cell input accept and retain retinal X-cell input (Friedlander et al. 1982). Dark-rearing from birth also leads to a reduction in the proportions of Y-cells recorded in the lateral geniculate nucleus (Kratz et al. 1979). Such a loss might also be due to abnormalities in retinogeniculate X- and Y-cell terminations. To test this possibility, we injected horseradish peroxidase into physiologically identified retinogeniculate axons of dark-reared cats. Surprisingly, we found that our sample of retinogeniculate X- and Y-cell axons in dark-reared cats had normal morphology. If our sample is representative of the entire population of retinogeniculate X- and Y-cell axons, retinogeniculate axon morphology in dark-reared cats differs from that in monocularly sutured cats. Yet, using extracellular recording, we replicated the observation that physiologically identified geniculate Y-cells are encountered less often in dark-reared cats than in normal cats. Given the apparent normality of the retinogeniculate axons in these cats, the "loss" of geniculate Y-cells in dark-reared cats could then conceivably be due to conduction block in retinogeniculate afferents, tonic inhibition on Y-cells, or deficits in non-retinal influences that may importantly affect Y-cell development.

Animals↗
PubMed1982

Thiamine deficiency in the cat leads to severe learning deficits and to widespread neuroanatomical damage.

Behavioral and neuroanatomical consequences of a thiamine-deficient diet, combined with the application of a thiamine-antagonist (pyrithiamine) were investigated in the cat. Eight cats (the experimental group) were subjected to a vitamin-B1-poor diet until they developed neurological symptoms (epileptic attacks, ataxia, gait disturbances), while 24 cats were fed normally and served as control group. Immediately following the appearance of neurological signs, a high dose of thiamine was given to the cats of the experimental group; they were then allowed to recover for ten days. Thereafter the performance in learning an alternation task in a T-maze was tested and compared with that of the control group. Behaviorally, the cats of the experimental group manifested drastically retarded acquisition rates in the learning task compared to the cats of the control group. Neuroanatomically, damage was found in the brains of each of the cats in the experimental group; this damage consisted mainly of enlarged ventricles, hemorrhages, neuronal loss and gliosis. Those regions most consistently affected were the periaqueductal gray, the inferior colliculi and the mamillary nuclei. The thalamic mediodorsal nucleus was affected to a minor degree in three cats only. Four cats manifested damage in the hippocampal formation. No damage was found in the cerebellum. Most of the damaged neuroanatomical loci resemble those found in patients with a Wernicke-Korsakoff syndrome.

Animals↗
PubMed1981

Critical flicker fusion in Siamese cats.

Critical flicker fusion was determined over a wide luminance range for six Siamese and four normal cats. The Siamese cats had the lowest CFF at all luminance levels when compared to normal and binocularly deprived (BD) cats. The Siamese cat's inferior temporal resolution is most likely due to their profound y-cell loss because (1) CFF is proportional to y-cell population across normal, BD, and Siamese cats; and (2) unlike BD cats, the visual cortex of Siamese cats is comparatively normal. The implication of this finding for the CFF of dark-reared cats and normal cats viewing a stimulus which does not stimulate y-cell is discussed.

Animals↗
PubMed2000

Pathological and experimentally induced blindness induces auditory activity in the cat primary visual cortex.

Early blindness in humans and experimental visual deprivation in animal models are known to induce compensatory somatosensory and/or auditory activation of the visual cortex. An abnormal hydrocephalic cat with extreme malformation of the visual system, born in our breeding colony, rendered a good model system for investigating possible cross-modal compensation in such a pathological case. For comparison, we used normal and neonatally enucleated cats. When introduced to a novel environment, the abnormal cat behaved as if it was completely blind, yet it responded normally to auditory stimuli. As anticipated, single cells in the visual cortex of normal cats responded to visual, but not to auditory stimuli. In the visual cortex of enucleated cats, flashes of light did not elicit field-evoked potentials or single-unit responses. However, several cells did respond to various auditory stimuli. In the remnant visual cortex of the abnormal cat, auditory stimuli evoked field potentials and single-cell responses. Unexpectedly, however, unlike the enucleated cats, in the abnormal cat, flashes of light also elicited field-evoked potentials. Judging by its behavior, it is very likely that this deformed cat had completely lost its ability to perceive images, but had probably retained some sensitivity to light.

Abnormalities, Multiple↗
PubMed2000

Genomic homology of the domestic ferret with cats and humans.

We used chromosome paints from both the domestic cat and humans to directly establish chromosomal homology between the genome of these species and the domestic ferret. The chromosome painting data indicate that the ferret has a highly conserved karyotype closer to the ancestral carnivore karyotype than that of the cat. The cat chromosome paints revealed 22 homologous autosomal regions in the ferret genome: 16 ferret chromosomes were hybridized by a single cat paint, while 3 ferret chromosomes were hybridized by two cat paints. In situ hybridization combined with banding showed that ferret Chromosome (Chr) 1 = cat A2p/C2, Chr 2 = F2/C1q, and Chr 3 = A2q/D2. Five ferret chromosomes are homologous to single arms of cat chromosomes: ferret 4 = A1q, 5 = B1q, 6 = C1p, 10 = A1p, and 12 = B1p. The human chromosome paints revealed 32 + XY homologous regions in the ferret genome: 9 ferret chromosomes were each hybridized by a single human paint, 7 by two paints, 3 by three paints. The 10 ferret chromosomes hybridized by multiple human paints produced the following associations: ferret 1 = human 19/3/21, 2 = 8q/2q, 3 = 10/7, 5 = 8/4, 8 = 15/14, 9 = 10/12/22, 11 = 20/2, 12 = 8/4, 14 = 12/22/18, 18 = 19/16. We present an index of genomic diversity, Z, based on the relative number of conserved whole chromosome and chromosome segments as a preliminary statistic for rapid comparison between species. The index of diversity between human-ferret (Z = 0. 812) is slightly less than human-cat (Z = 0.843). The homology data presented here allow us to transfer gene mapping data from both cats and humans to the ferret.

Animals↗
PubMed1986

Vasoactive intestinal polypeptide (VIP) and cerebrospinal fluid (CSF) of sleep-deprived cats restores REM sleep in insomniac recipients.

In the past few years a steadily increasing number of substances have been suggested to qualify as sleep-inducing factors. Most 'sleep factors' appear to exert their effects on slow-wave sleep. Recently, however, it has been shown that the cerebrospinal fluid (CSF) of sleep-deprived cats may contain a rapid eye movement (REM) sleep factor, and that vasoactive intestinal peptide (VIP) may be a specific REM sleep inducer. The purpose of this study is to determine whether the CSF of sleep-deprived cats and VIP can reverse insomnia produced by parachlorophenylalanine (PCPA). Donor cats were sleep-deprived for 24 h and their CSF extracted. Some donor cats were additionally pre-treated with chloramphenicol, and some extracted CSF was heated. Recipient cats were injected with 400 mg/kg i.p. of PCPA on two consecutive days. Twenty-four h after the second injection, the recipient cats were intraventricularly injected with a 100-microliters of the various CSF types or 200 ng of VIP. The results showed that only CSF from sleep-deprived cats and VIP were capable of restoring REM sleep in the otherwise PCPA insomniac cats. Since the return of REM sleep was through an increase in its frequency, it is suggested that the CSF of sleep-deprived cats contains a VIP-like sleep factor possibly involved in triggering REM sleep.

Animals↗
PubMed1991

Coordination of motor pools controlling the ankle musculature in adult spinal cats during treadmill walking.

The coordination of the motor pools of two ankle plantar-flexor, i.e. the soleus (Sol) and medial gastrocnemius (MG), and an ankle dorsiflexor, i.e. the tibialis anterior (TA) was quantified by comparing the EMG amplitude relationships in muscle pairs in normal and trained adult spinalized cats during treadmill walking across a range of relatively slow speeds (0.1 to 1.0 m/s). The effects of increased tactile stimulation or loading on locomotor performance were also studied in the spinal cats. Joint probability density distributions in the spinalized cats showed a low level of MG activation relative to Sol which did not change as speed increased. In general, the coordination between Sol and MG was similar in normal and spinal cats. However, towards the final phase of the extensor burst, the MG EMG amplitude decayed prematurely in spinal cats, particularly at higher speeds. Preferential elevation of MG relative to Sol activity was seen as a result of tactile stimulation. An elevated load resulted in a higher level of MG activation relative to Sol, prolonged MG activity at the end of the extensor burst, and the reduction in the clonic pattern of EMG typical of spinal cats. Spinalized cats showed an increased incidence of Sol-TA coactivation, especially at the higher speeds, due in part to the tonic activity in the TA. However, the overall reciprocal relationship between these antagonists was maintained. This reciprocity was preserved, but the high level of coactivation was unaffected by tactile stimulation. An elevated load, however, resulted in less Sol-TA coactivation. These results suggest that the coordination between synergists (Sol-MG) and between antagonists (Sol-TA and MG-TA), as well as the level of activation are modulated in the adult spinal cat similar to that observed in the normal cat. Further, there are specific types of proprioceptive-cutaneous information that can affect selected phases of the step cycle such that full weight-supporting stepping is significantly improved.

Animals↗
PubMed1987

High dorsal column cordotomy plus subdiaphragmatic vagotomy prevents acute ionizing radiation sickness in cats.

Our purpose was to determine the effects on acute radiation sickness of interrupting afferent neural pathways that converge upon the medullary vomiting center but which bypass the emetic chemoreceptor trigger zone in the area postrema. A comparison was made of the vomiting response and other signs of sickness in three groups of chronic cats surgically prepared as follows: high spinal cord section of the dorsal columns, subdiaphragmatic vagotomy, and the combination of procedures. Every cat was exposed over the whole body to 45 Gy 60Co gamma-radiation which was effective in evoking emesis in 11 of 12 normal cats. Neither cordotomy alone (8 cats) nor vagotomy alone (2 cats) reliably blocked the vomiting response but they separately delayed its onset. On the other hand, the cordotomy prevented the loss of appetite and behavioral malaise that was invariably caused by the irradiation in normal cats. Finally, the combination of cordotomy and vagotomy protected all of 3 cats against the entire radiation syndrome. These cats then vomited appropriately in response to the injection of deslanoside which induces emesis through an action on the area postrema. Histological examination of the lower medulla revealed no damage of the area postrema resulting from the cordotomies. We conclude that acute radiation sickness in the cat is signaled through afferent neural pathways originating in the abdomen and that the area postrema does not participate in the causation of this syndrome.

Animals↗
PubMed1988

Unilateral interruption of geniculate and callosal inputs to the visual cortex of cats: ocular dominance and responsiveness of cells in the deafferented and in the intact hemispheres.

In order to study the ocular dominance and responsiveness of cells in the deafferented visual cortex, the geniculate and the callosal inputs were interrupted in adult cats by either simultaneous (OTCCX) or separate surgical transection of the optic tract (OTX) and the posterior corpus callosum (CCX). Unit recording was chronically carried out mainly in the boundary of areas 17-18, the callosal projection zone. A small proportion of visually responsive cells was encountered in the deafferented hemisphere of the OTCCX (8.3%) and the OTX (6.3%) cats. In the intact hemisphere, 59.7% of the cells were visually responsive in the OTCCX cats and 57.0% in the OTX cats; they were 61.6% of the cells in the CCX cats and 85.6% in the normal controls (both hemispheres). The majority of the cells in the deafferented hemisphere of the OTCCX (88.9%) and the OTX (82.4%) cats were binocularly driven. In the intact hemisphere of the OTCCX cats, 85.1% of the cells were binocularly driven, in comparison to 77.6% in the OTX cats, 48.8% in the CCX cats, and 81.5% in the normal controls. We therefore concluded that following unilateral elimination of the geniculate input as well as the callosal transection, binocularity in the intact hemisphere was preserved despite the remarkable diminution in the responsiveness level there. Furthermore, the supply of visual input to the deafferented hemisphere was not affected after callosotomy, suggesting an alternative transfer, albeit minor, via an anterior callosal or another commissural pathway.

Afferent Pathways↗