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Biomedical subjects

R C Pearson

Publications and source records attributed to R C Pearson.

At least 109 records · Page 6Linked to original sources
PubMed1985

Hypertrophy of cholinergic neurones of the rat basal nucleus following section of the corpus callosum.

The effect of division of the corpus callosum on immunohistochemically identified cholinergic neurones of the basal nucleus has been examined in rats. Following callosal section the cholinergic cell bodies on both sides are significantly larger (25%) than those in normal animals. This hypertrophy persists for at least 62 days after operation, the longest survival time examined. It is greatest when the animal is operated on in infancy, but it occurs at all ages examined. The enlargement is similar to that seen in the cells of the same nucleus on one side following contralateral cortical damage.

Animals↗
PubMed1985

The callosal connexions of the primary somatic sensory cortex in the monkey.

The callosal connexions of the primary somatic sensory cortex, SI, of the monkey have been studied with axonal degeneration methods after the placement of lesions of varying size in the cortex of one hemisphere and after section of the corpus callosum. For the correlation of the distribution of the degeneration with the cytoarchitectonic subdivisions of SI and with their boundaries, planar reconstructions of the extents of the subdivisions and of area 5 were made. The extent of area 5 is surprisingly large, being about the same as SI, and area 3a can be recognized as a distinct subdivision along the entire medio-lateral extent of SI. The callosal fibres end in narrow, irregular bands aligned in the medio-lateral dimension and there are accentuations at the boundaries of the cytoarchitectural subdivisions. In the representations of the trunk and face, the bands of degeneration are present across the entire antero-posterior extent of SI and with increases at the boundaries, while in the limb regions the degeneration becomes restricted to the boundaries. It is suggested that the callosal connexions of the somatic sensory cortex, like those in the visual and auditory areas, are connecting those parts of the cortex in the two hemispheres that are concurrently activated by a peripheral stimulus. The parts of SI that are devoid of callosal connexions are related to the distal limbs. The callosal connexions are homo- and heterotopical; an architectonic subdivision within the callosally connected regions projects to the same and other architectonic subdivisions at the same medio-lateral level in the opposite hemisphere; the cortex containing the representation of the caudal trunk near the post-central dimple is connected with the same region in the other hemisphere and with that of the separate representation of the caudal trunk in the posterior part of the cingulate sulcus, while the representation of the occipital region at the post-central dimple is connected both with the homotopical site in the other hemisphere and with the other representation of this part of the periphery at the level of the lower end of the intraparietal sulcus.

Animals↗
PubMed1985

The ipsilateral cortico-cortical connexions between the cytoarchitectonic subdivisions of the primary somatic sensory cortex in the monkey.

The ipsilateral cortico-cortical connexions passing between the architectonic subdivisions of the primary somatic sensory cortex, S1, of the monkey have been studied with axonal degeneration methods after the placement of small lesions. All architectonic subdivisions except area 3a, and all the topographic representations, have been involved by the lesions. The degeneration of local intracortical fibres has the same features that have been described in other cortical areas: dense terminal degeneration for about 200 micron immediately around the lesion and moderate degeneration extending for a few millimetres with that in layers I, IV and the deep part of V being the most marked and reaching furthest; the degeneration extends further in the antero-posterior than in the medio-lateral dimension, and further posteriorly than anteriorly. The arrangement of the intercortical fibre connexions varies with the architectonic subdivision and with the topographic representation, and as in other sensory areas these fibres may be considered as either feed-forward or feed-back. The feed-forward projections are heavy, terminate in all layers of the cortex but mainly in layer IV and the deep part of layer III, whereas the feed-back connexions are lighter and end in layers I, II, the superficial part of layer III and in layers V and VI. In the antero-posterior dimension, feed-forward fibres from area 3b go to areas 3a, 1 and 2; area 1 sends feed-forward connexions to areas 3a and 2 and feed-back to area 3b; area 2 sends a feed-forward projection to area 3a and feed-back to areas 3b and 1; all areas also send fibres to area 5. A lesion in one of the architectonic subdivisions in the trunk and face representations results in degeneration throughout the antero-posterior extent of S1, but after damage within an architectonic area in the distal limb regions, there are foci of degeneration in the middle of the antero-posterior extents of the other areas but with little or none at the boundaries. The cortico-cortical fibres also extend medially or laterally for a few millimetres, in bands a few hundred micron wide. After damage of the trunk, occiput or proximal limb representations, the degenerating fibres pass predominantly along the boundaries; the separate representations of the caudal trunk, at the postcentral dimple and cingulate sulcus, are connected by continuous bands along the boundaries of area 3a and at the 2/5 boundary, and those of the occiput region at the levels of the postcentral dimple and lower end of the intraparietal sulcus are similarly linked.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

The projection of the primary somatic sensory cortex upon area 5 in the monkey.

The projection of the cortex of the primary somatic sensory area (S1) upon area 5 in the rhesus monkey has been studied with axonal degeneration methods. There is little or no overlap between the major topographic representations in area 5 but there is both convergence and divergence within a representation; the degeneration after a small lesion in a representation in SI virtually fills the representation in area 5 and there is extensive overlap of the degeneration after two lesions in widely separated parts of the representation in S1. The representation of the arm in area 5 is surprisingly large, that of the face is relatively smaller than in S1 and the trunk and leg are about the same as in S1. Lesions in the trunk and face representations result in terminal degeneration throughout the antero-posterior extent of area 5, but after damage of the limb representations the degeneration in area 5 is concentrated into 3 medio-laterally disposed bands. Of the cytoarchitectonic subdivisions of S1, area 2 projects most heavily upon area 5 and area 3b the least, and there is a reversal in the antero-posterior dimension with more posterior parts of S1 projecting to more anterior parts of area 5. The corticocortical fibres from S1 end in layers III and IV of area 5, and while the degeneration in layer IV is continuous it is in distinct 'prongs' in layer III.

Animals↗
PubMed1985

Anatomical correlates of the distribution of the pathological changes in the neocortex in Alzheimer disease.

The numbers and distribution of the neurofibrillary tangles and neuritic plaques have been determined in several areas of the neocortex in brains affected by various degrees of severity of Alzheimer disease. The homotypical cortex of the "association" areas of the temporal, parietal, and frontal lobes are severely involved, whereas the motor, somatic sensory, and primary visual areas are virtually unaffected. The neurofibrillary tangles are mainly in the supra- and infragranular layers, particularly in layers III and V. In all areas except area 18 in the occipital lobe, there are approximately twice as many tangles in layer V as in layer III. The tangles are arranged in definite clusters, and those in the supra- and infragranular layers are in register. The neuritic plaques occur in all layers but predominantly affect layers II and III and do not show clustering. These data on the severity of the pathological involvement in different areas of the neocortex and the laminar distribution and the clustering of the tangles support the suggestion that the pathological changes in Alzheimer disease affect regions that are interconnected by well-defined groups of connections and that the disease process may extend along the connecting fibers. The invariable and severe involvement of the olfactory areas of the brain in this disease is in striking contrast to the minimal changes in the somatic sensory and primary visual areas and raises the possibility that the olfactory pathway may be initially involved.

Aged↗
PubMed1985

Effect of unilateral decortication on choline acetyltransferase activity in the nucleus basalis and other areas of the rat brain.

Acetyl-coenzyme A: choline O-acetyltransferase (EC 2.3.1.6) (ChAT) enzyme activity was measured in the nucleus basalis and other microscopically identified brain areas at various times after unilateral cortical lesions were made in the rat. Initially, a significant decrease in ChAT activity was detected in the nucleus basalis ipsilateral to the lesion. However, after 120 days ChAT activity had apparently recovered, as levels of the enzyme at that time were not significantly different from control values. No changes in ChAT activity could be detected in any of the other brain areas similarly studied. The significance of these findings and their relationship to the morphological changes seen in neurones of the nucleus basalis after cortical lesions are discussed.

Animals↗
PubMed1984

Hypertrophy of immunohistochemically identified cholinergic neurons of the basal nucleus of Meynert following ablation of the contralateral cortex in the rat.

The effects of unilateral damage of the cortex on cholinergic neurons identified by immunohistochemical demonstration of choline acetyltransferase, were examined in the basal nucleus of the rat. Those cells contralateral to the lesion showed significant hypertrophy as compared with cells in the same nucleus in age- and sex-matched control animals. This enlargement was present by 7 days and persisted after 300 days postoperatively, the longest survival time examined. The age of the animal at operation and the extent of the damage may influence the magnitude of the enlargement. Similar changes were seen in the cholinergic cells of the medial septal nucleus after removal of the contralateral hippocampus.

Acetylcholine↗
PubMed1984

Voice changes following cricothyroidotomy.

Twenty-four patients underwent cricothyroidotomy at Guy's Hospital between 1977 and 1981. Of these, 13 died during admission or shortly after discharge as a result of their primary disease and three were unsuitable for further examination. The eight remaining patients were examined to assess the effect of cricothyroidotomy on the laryngeal function of voice production. Assessment was made both subjectively and objectively by laryngography. Objective findings were correlated with structural changes seen by indirect laryngoscopy. Six of the eight patients examined had both subjective and objective disturbance of voice production. We report our experience with the surgical procedure of cricothyroidotomy which, in addition to a high incidence of vocal disturbance, includes one case of subglottic stenosis secondary to granulation tissue.

Adolescent↗
PubMed1984

Times of appearance and disappearance of colostral IgG in the mare.

Pre- and postpartum colostral samples collected from 14 Arabian and 22 Thoroughbred mares were examined for color, consistency, and immunoglobulin (Ig)G concentration. Initial samples, obtained 3 to 28 days before mares had foaled, contained greater than 1,000 mg of IgG/dl. Mean concentration of IgG in colostrum of the Arabian mares at the time of parturition (T0) was 9,691 mg/dl and was significantly (P less than 0.05) higher than the average, 4,608 mg/dl, for the Thoroughbreds. Average times lapsed from T0 until the colostral IgG decreased to 1,000 mg/dl (T1,000) was 19.1 hours for the Arabian mares and 8.9 hours for the Thoroughbred mares--the former being significantly (P less than 0.01) longer. Induction of parturition by injection of oxytocin had no significant effect either upon the colostral IgG concentration at T0 or upon the T1,000.

Animals↗
PubMed1983

Retrograde changes in cholinergic neurons in the basal forebrain of the rat following cortical damage.

The effects of unilateral cortical damage on immunohistochemically identified cholinergic neurons of the basal nucleus have been examined in the rat. In the first 2 weeks after operation, the cells were swollen and their nuclei became eccentric, these changes being closely similar to those seen in the cholinergic oculomotor nuclei of the same animals following removal of the extraocular muscles. During the third week these acute changes were replaced by shrinkage of the cholinergic cell bodies and their dendrites. At longer survival times the appearance of the neurons did not alter, and all the cholinergic cells persisted in their shrunken form after 120 days, the longest survival time examined.

Acetylcholine↗
PubMed1983

Persistence of cholinergic neurons in the basal nucleus in a brain with senile dementia of the Alzheimer's type demonstrated by immunohistochemical staining for choline acetyltransferase.

Immunohistochemically identified cholinergic neurons in the basal nucleus of Meynert in a brain with SDAT have been compared with those in two age- and sex-matched normal brains. The numbers of such cells at carefully matched levels are not significantly lower, but the cells in SDAT are substantially smaller than in the normal basal nucleus. The persistence of shrunken cholinergic neurons in the basal nucleus in the diseased brain is similar to that seen in an experimental study of retrograde cellular degeneration in the nucleus following damage of the cortex.

Acetylcholinesterase↗
PubMed1983

Retrograde cell degeneration in the basal nucleus in monkey and man.

Retrograde cellular degeneration has been found in the basal nucleus of Meynert in macaque monkeys after large lesions of the neocortex, and in the human brain after either hemidecortication or leucotomy. These observations may be relevant to the interpretation of the cellular degeneration in the basal nucleus in Alzheimer's disease.

Animals↗
PubMed1983

The cortical relationships of certain basal ganglia and the cholinergic basal forebrain nuclei.

Three groups of subcortical nuclei are related to the entire cerebral cortex, to the allocortex of the hippocampus and olfactory areas as well as the neocortex. The medial septal nucleus, the nucleus of the diagonal band and the basal nucleus send cholinergic fibers to the cortex: the striatum, neo- and ventral, receives fibers from the cortex and the claustrum has reciprocal cortical connections. In their neocortical relationships there are marked similarities between these groups.

Acetylcholine↗
PubMed1983

The projection of the basal nucleus of Meynert upon the neocortex in the monkey.

After injections of horseradish peroxidase into several areas of the neocortex in the macaque monkey longitudinal bands of labeled cells in the basal nucleus of Meynert related to areas of cortex in the frontal lobe have been found to overlap along their long axes with the bands related to widely separated but interconnected areas of the parieto-temporal cortex. The frontal and parietal lobes are related to the anterior and posterior halves respectively of the nucleus, the temporal cortex to the postero-lateral margin of the nucleus and the occipital lobe to its upturned posterior extension.

Animals↗
PubMed1982

The organization of the connections between the cortex and the claustrum in the monkey.

The distribution of labelled cells and of extracellular granules in the claustrum has been studied after injections of horseradish peroxidase in several areas of the neocortex. The frontal and parietal lobes are related to the anterior and posterior halves respectively of the claustrum, and the occipital and temporal cortex to the posterior and inferior margins. Parts of the claustrum related to areas of the cortex in the frontal lobe overlap considerably in the antero-posterior dimension with parts related to widely separated but interconnected areas of the parieto-temporal cortex. Areas of cortex within one lobe which are interconnected are related to parts of the claustrum which overlap in the dorsoventral dimension.

Animals↗