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Biomedical subjects

D M Mann

Publications and source records attributed to D M Mann.

At least 181 records · Page 10Linked to original sources
PubMed1982

Accumulation of lipoprotein pigments in nerve cells of British and Sri Lankan nationals.

The lipofuscin and melanin contents of nerve cells were measured in 18 subjects, 9 of British Nationality, 9 of Sri Lankan, both groups being matched for age and sex. Lipofuscin content was apparently increased for age in the British group, though melanin content was unchanged. Nucleolar volume was unaltered in both groups for all cell types. It is suggested that the lipid portion of the lipofuscin granule is increased in the British cases, rather than the actual mass of pigment granules, and that this change in composition may be related to differences in diet, particularly in respect of the amount of polyunsaturated fat consumed by the two populations.

Adolescent↗
PubMed1982

The noradrenergic system in Alzheimer and multi-infarct dementias.

The number of melanin containing nerve cells of the locus coeruleus and vagus nucleus is reduced in Alzheimer's disease by 60% with decrease of 22% in the protein synthetic capability of remaining cells. These changes are matched by reductions in brain noradrenaline in eight regions, averaging 36%. In multi-infarct dementia, however, all three of these features are unchanged. These findings indicate that degeneration of central noradrenergic nerve cells is a specific aspect of the pathogenic process underlying Alzheimer's disease.

Aged↗
PubMed1981

The relationship between formation of senile plaques and neurofibrillary tangles and changes in nerve cell metabolism in Alzheimer type dementia.

Nerve cell nucleolar volume in reduced, in senile dementia of Alzheimer type, by 15 - 25% in nerve cells not containing neurofibrillary tangles and by over 35% in those which do contain such changes, in a wide variety of brain regions, when compared to similar cells from non-demented control cases, suggesting that interference with production of proteins may be an early consequence of the pathogenic process. The extent to which nucleolar volume is decreased in the non-tangle-bearing cells is related to frequencies of both neurofibrillary tangle and senile-plaque formation within that region, but the reduction in volume in the tangle-bearing cells correlated with neurofibrillary changes only. It seems, therefore, that the severity with which the dementing process affects an area of brain is initially shown by alterations in cell metabolism, which may invoke reductions in protein synthesis in non-tangle-bearing cells, and is later marked by the proportion of these affected cells which go to form neurofibrillary tangles. Changes in nerve cell function do not seem to be as well indicated by the density of senile plaques within that area.

Aged↗
PubMed1981

Alterations in protein synthetic capability of nerve cells in Alzheimer's disease.

Cytoplasmic RNA content, nuclear and nucleolar volume are all significantly reduced in nerve cells of the temporal cortex in cases of Alzheimer's disease, examined both at diagnostic craniotomy and post mortem, when compared with non=demented control cases of similar age. On average, at necropsy, all three parameters are equally reduced by about 40-50%, but in biopsy cases, nuclear volume is decreased by the greatest amount (43%), followed by nucleolar volume is decreased by the greatest amount (43%), followed by nucleolar volume (36%), and cytoplasmic RNA (26%). These findings indicate that a change in protein synthesis occurs daily in the course of Alzheimer's disease which may result from a primary alteration within the nuclear apparatus.

Adult↗
PubMed1980

The fine structure of the axonal torpedo in Purkinje cells of the human cerebellum.

Axonal torpedoes on Purkinje cells of the cerebellum have been observed at electron microscopic level in the case of a 5-year-old boy suffering from juvenile astrocytoma present in the roof of the fourth ventricle and cerebellar hemisphere. The axon torpedo is characterised by a central accumulation of disoriented neurofilaments, which displace the mitrochondria and endoplasmic reticular elements to the periphery. The mitochondria are small and densely staining with longitudinally arranged cristae and are intimately associated with the smooth endoplasmic reticulum that occurs as stacked complexes. Multivesicular and lamellar bodies, typical of degenerating axons, are not consistently seen and this indicates that axon torpedoes are more likely to represent a regenerating state within the nerve fibre than a degenerative condition.

Astrocytoma↗
PubMed1980

Changes in the monoamine containing neurones of the human CNS in senile dementia.

In thirteen cases of senile dementia of the Alzheimer type severe loss of nerve cells from the locus caeruleus was frequently seen together with reductions in nucleolar volume and cytoplasmic RNA in surviving cells, averaging 14 and 21 per cent respectively. These histological findings were matched in two cases by biochemical measurements of loss of noradrenaline from all brain regions examined, ranging from 10 per cent in temporal cortex to 53 per cent in hypothalamus. By contrast, neither nucleolar volume nor cytoplasmic RNA was altered in cells of the substantia nigra, nor was dopamine content significantly altered in most regions. In vascular dementia neither noradrenaline nor dopamine metabolism was changed except in regions of local circulatory deficiency. These findings provide evidence of a primary degeneration of the noradrenergic system in Alzheimer type dementia.

Aged↗
PubMed1979

The effects of ageing on the pigmented nerve cells of the human locus caeruleous and substantia nigra.

The nucleolar volume and melanin content of the human locus caeruleus and substantia nigra has been measured in 70 persons of age range new born to 91 years, all of whom were at death free from overt neurological illness. Both cell types show a reduction in nucleolar size with advancing age, which becomes disproportionately larger towards old age. At 90 years of age, the change in nucleolar volume in cells of the locus caeruleus amounts to about 5% whereas cells of the substantia nigra show a loss of 20%. The greater decrease in nucleolar volume in cells of the substantia nigra is attributed to the higher concentration of melanin pigment occurring in these cells at old age, rather than the absolute amount present. This marked decline in nucleolar volume in cells of substantia nigra indicates a reduced activity in the cell which, in turn, may be reflected in the difficulty in control and coordination in muscular activity commonly seen in normal elderly persons.

Adolescent↗
PubMed1978

The DNA content of Purkinje cells in mammals.

Nerve cells have generally been assumed to have a diploid DNA content, typical of non-dividing somatic cells. However several reports have suggested that certain nerve cells types, notably Purkinje cells of the cerebellum, are polyploid. Other studies have contradicted these findings, stating Purkinje cells to be diploid. In this paper we reinvestigate the DNA status of Purkinje cells, in a variety of mammalian species. Cell DNA content is measured on tissue smears by Feulgen microspectrophotometry. Results show that for all species examined by us, Purkinje cells have, without exception, a DNA content comparable to that of somatic cells. A critical appraisal of the techniques used in those studies claiming a tetraploid DNA content for Purkinje cells leads us to believe our findings to be correct.

Animals↗
PubMed1978

Granulovacuolar degeneration in pyramidal cells of the hippocampus.

We have shown that as the number of granulovacuolar bodies in affected pyramidal cells of the hippocampus increases so cytoplasmic RNA contant is reduced. Prior to its degeration, the nucleolus is increased in volume while that of the nucleus remains unchanged in size throughout. The effects of these degenerative changes are to bring about a progressive decline in the capacity for nerve cell function, leading eventually to the death of the cell.

Aged↗
PubMed1978

Post-mortem changes in human central nervous tissue and the effects on quantitation of nucleic acids and enzymes.

A study of post-mortem changes in human central nervous tissue has shown that within 100 h of death, no significant change occurs in the amount of nerve cell DNA and nucleolar RNA nor in some membrane-associated enzymes such as succinate dehydrogenase, NADH and NADPH diaphorase, and cytochrome oxidase. Low molecular weight RNA species, probably transfer and messenger RNA are quickly lost, but there is little alteration in ribosomal RNA content. Cytoplasmic enzymes show variable changes; phosphofructokinase activity is rapidly decreased; hexokinase is unaltered but lactate dehydrogenase, pyruvate kinase and glucose-6-phosphate dehydrogenase initially show increases in activity which subsequently decline. Oxygen uptake diminishes quickly. These findings indicate that mechanical alterations in cell structure, following death, render organelles physiologically ineffective long before any significant changes in certain constituent biochemicals are detected. This report emphasizes the great importance necessary in the selection of appropriately time matched post-mortem tissues if accurate comparative studies of many of the cells constituents are to be made.

Aged↗
PubMed1978

The relationship between lipofuscin pigment and ageing in the human nervous system.

The cytoplasmic RNA content, nucleolar volume and lipofuscin content of nerve cells of the inferior olivary and dentate nuclei, Purkinje cells and pyramidal cells of the hippocampus has been measured in 82 persons of age range 2--91 years, who were free from overt neurological disease at the time of death. All 4 cell types accumulate lipofuscin in a linear manner throughout life, but to markedly differing extents. Both the RNA content and nucleolar volume of dentate, olivary and hippocampal cells decrease, with advancing age, in a similar way in all of these 3 cell types, despite the widely differing extents of pigment accumulation, with losses of RNA and nucleolar volume at 90 years of age of 15 and 30% respectively. Olivary cells which contain most pigment show a different pattern of change with losses of RNA and nucleolar volume of about 60%. It seems, therefore, that, if there is a causal relationship between lipofuscin accumulation and reductions in RNA and nucleolar volume, it is rather obscure. It cannot simply be a matter of the absolute amounts of pigment present in any one cell type, but rather might be that there is a critical concentration of such material in the cytoplasm.

Adolescent↗
PubMed1977

Cytophotometric mapping of neuronal changes in senile dementia.

Results of a cytophotometric study have shown a widespread reduction in cytoplasmic RNA of nerve cells. It appears, therefore, that although certain aspects of the symptomatology of senile dementia may be accounted for by lesions in particular anatomical sites, the main part of the neurological disturbance is related to more broadly based changes in nerve cell metabolism affecting much, if not all, of the CNS.

Brain Chemistry↗