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C U Smith

Publications and source records attributed to C U Smith.

34 records · Page 2Linked to original sources
PubMed1993

Comparative efficiency of volume and synaptic transmission in the coerulean system: relevance to neurologic rehabilitation.

Over the past few years evidence has accumulated which confirms earlier beliefs that punctate synaptic transmission (wiring transmission) is not the only means by which "informational substances" affect cerebral neurons. This paper considers the relative efficiency of "volume" and "wiring" transmission in controlling large populations of neurons taking as a specific example the mammalian coerulean system. Making reasonable quantitative assumptions it is shown that volume transmission is a more efficient means of controlling "mass" functions than a wiring mode. Implications for the reorganisation of function following brain damage are noted.

Animals↗
PubMed1991

Alzheimer's disease: size class frequency distribution of senile plaques: do they indicate when a brain tissue was affected?

The size class frequency distribution of a sample of senile plaques (SP) was determined in a total of 20 brain regions from 5 elderly cases of Alzheimer's disease (AD). The purpose of the study was to determine whether a comparison of the frequency distributions could be used to determine the chronology of SP development in the AD brain. SP from 10 microns to a maximum diameter of 160 microns were present in the tissue and the size class frequency distributions were positively skewed. The frequency distributions varied between brain regions in: (1) the size class containing the mode, (2) the degree of positive skew, and (3) the ratio of large to small SP. In most patients the ratio of large to small SP was higher in the hippocampus or adjacent gyrus compared with temporal, parietal and frontal neocortex. If the diameter of a SP reflects its age in the tissue than the data suggest that SP formed earlier either in the hippocampus or adjacent gyrus compared with the other neocortical tissues. However, this conclusion rests on a number of assumptions including: (1) that SP diameter is directly related to age, (2) that SP development occurs at similar rates in different brain regions and (3) that, once formed, SP are not removed from the tissue by astrocytes.

Alzheimer Disease↗
PubMed1991

Alzheimer's disease: the relationship between the density of senile plaques, neurofibrillary tangles and A4 protein in human patients.

The numerical density of senile plaques (SP) and neurofibrillary tangles (NFT) as revealed by the Glees silver method was compared with SP and NFT revealed by the Gallyas method and with amyloid (A4) deposits in immunostained sections in 6 elderly cases of Alzheimer's disease. The density of NFT was generally greater and A4 lower in tissue from hippocampus compared with the neocortex suggesting that A4 deposition was less important than the degree of paired helical filament (PHF) related damage in the hippocampus. The density of Glees SP was positively correlated Gallyas SP weakly correlated with A4 deposit number. A stepwise multiple regression analysis which included A4 deposit and Gallyas SP density and accounted for 54% of the variation in Glees SP density. Hence, different populations of SP were revealed by the different staining methods. The results suggested that the Glees method may stain a population of SP in a region of cortex where both amyloid deposition and neurofibrillary changes have occurred.

Alzheimer Disease↗
PubMed1987

David Hartley's Newtonian neuropsychology.

David Hartley's association psychology has been immensely influential. His vibrationist neurophysiology has, in contrast, been largely overlooked and forgotten. Hartley's vibration theory is examined. On the one hand it is shown how closely it is related to Sir Isaac Newton's mathematical physics and on the other how well it complements the association theory. The vibration theory, indeed, strongly influenced Hartley's associationist psychology and hence is of more than merely antiquarian interest. Although Hartley's understanding of the central nervous system has long been superseded, his general ideas prefigure some aspects of contemporary neurophysiology and philosophy of mind and thus provide a further reason for rescuing his vibrationism from oblivion.

England↗
PubMed1981

Don Juan and the vision of Vision.

Castaneda's well-known sequence of Don Juan books is used as a paradigmatic example of the relativist position. Central to Don Juan's teaching is the problem of perception: the main task, he constantly reiterates, is simply to 'see', to recognise that the commonsense world we customarily perceive is nothing more than a cultural construct. To combat this thoroughgoing relativism a case study is taken from the early history of visual science. In classical antiquity several fundamentally different 'views' (to use Don Juan's term) of how we see contended for approval. It was only at the beginning of the seventeenth century that the 'modern' interpretation was selected. This interpretation was selected, ultimately, because it 'worked'. Reference is made to both Wittgenstein and Marx to support this appeal to praxis. It is argued that through an intricate, complex, and ill-understood process of popularisation our self-image is ultimately grounded in the theories of natural science; and these, in turn, are ultimately grounded in our action in the world of things.

Greece↗
PubMed1976

Morphologic and biochemical changes in autolysing dog heart muscle.

The progressive changes in pH, lactate content, and light and electron microscopic appearances were studied in dog myocardium undergoing a 6-hour period of autolysis in vitro at 37 degrees C. and at room temperature. At 37 degrees C. there was a rapid cumulative fall in pH during the 1st hour after excision of the heart and a corresponding increase in lactate content, but little additional change in either subsequently. The nature and sequence of the morphologic alterations at this temperature were generally similar to those which occur in ischemic myocardium in vivo. At room temperature, a much slower cumulative decrease in pH and increase in lactate content took place throughout the whole period of investigation and was paralleled by a slower rate of development of morphologic change.

Animals↗
PubMedDate not supplied

The use of multivariate methods in the identification of subtypes of Alzheimer's disease: a comparison of principal components and cluster analysis.

Two contrasting multivariate statistical methods, viz., principal components analysis (PCA) and cluster analysis were applied to the study of neuropathological variations between cases of Alzheimer's disease (AD). To compare the two methods, 78 cases of AD were analyzed, each characterised by measurements of 47 neuropathological variables. Both methods of analysis revealed significant variations between AD cases. These variations were related primarily to differences in the distribution and abundance of senile plaques (SP) and neurofibrillary tangles (NFT) in the brain. Cluster analysis classified the majority of AD cases into five groups which could represent subtypes of AD. However, PCA suggested that variation between cases was more continuous with no distinct subtypes. Hence, PCA may be a more appropriate method than cluster analysis in the study of neuropathological variations between AD cases.

Aged↗
PubMedDate not supplied

The spatial patterns of plaques and tangles in Alzheimer's disease do not support the 'cascade hypothesis'.

In Alzheimer's disease (AD), the 'Cascade hypothesis' proposes that the formation of paired helical filaments (PHF) may be casually linked to the deposition of beta/A4 protein. Hence, there should be a close spatial relationship between senile plaques and cellular neurofibrillary tangles in a local region of the brain. In tissue from 6 AD patients, plaques and tangles occurred in clusters and individual clusters were often regularly spaced along the cortical strip. However, the clusters of plaques and tangles were in phase in only 4/32 cortical tissues examined. Hence, the data were not consistent with the 'Cascade hypothesis' that beta/A4 and PHF are directly linked in AD.

Aged↗
PubMedDate not supplied

The ratio of diffuse to mature beta/A4 deposits in Alzheimer's disease varies in cases with and without pronounced congophilic angiopathy.

The density of diffuse, primitive, classic and compact beta/A4 deposits was estimated in the cortex and hippocampus in Alzheimer's disease (AD) cases with and without pronounced congophilic angiopathy (CA). The total density of beta/A4 deposits in a given brain region was similar in cases with and without CA. Significantly fewer diffuse deposits and more primitive/classic deposits were found in the cases with CA. The densities of the primitive, classic and compact deposits were positively correlated in the cases without CA. However, no correlations were observed between the density of the mature subtypes and the diffuse deposits in these cases. In the cases with CA, the density of the primitive deposits was positively correlated with the diffuse but not with the classic deposits. The data suggest that the mature beta/A4 deposits are derived from the diffuse deposits and that the presence of pronounced CA enhances their formation.

Aged↗