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T Kemper

Publications and source records attributed to T Kemper.

35 records · Page 2Linked to original sources
PubMed1990

Effects of protein deprivation on pyramidal cells of the visual cortex in rats of three age groups.

The effect of protein deprivation on rapid Golgi impregnated pyramidal neurons in layers II/III and V of the rat visual cortex was studied at 30, 90, and 220 days of age using morphometric methods. In order to mimic human under-nutrition female rats were adapted to either an 8% or control 25% casein diet 5 weeks prior to conception and maintained on these diets during gestation and lactation. The pups were then weaned and maintained on their respective diets. The undernourished rats showed a significant decrease in brain weight only at 90 days, indicating that the protein deprivation had a mild effect on brain development. Correspondingly, the number of significant histological differences between the two diet groups were least at 30 and 220 days of age. The effect of the diet was greater on layer V than on layer II/III pyramids. At 30 days of age the effect of the diet was different on the pyramids of these two cell layers, at 90 days there was a mixture of similar and dissimilar effects, and at 220 days the pyramids of these two cell layers showed only minor differences between the two diet groups. Analysis of age-related changes indicated that the effect of the diet was different on layer II/III pyramids compared to layer V pyramidal cells. These different effects apparently accounted for the progression from a dissimilar effect of the diet at 30 days on the pyramids of the two cell layers to only minor differences between them at 220 days. Further analysis of these age-related changes shows that two prominent effects of protein deprivation are for age-related changes to occur in undernourished rats but not in controls and for age-related changes to be out-of-phase with each other in the two diet groups. From these findings, and a review of similar studies in the literature, we propose that these mechanisms are a prominent effect of undernutrition in the post-weaning period and help account for the unexpected increases in morphometric measurements noted in undernourished rats in this and other studies.

Aging↗
PubMed1988

Occurrence of stroke in a nonhuman primate model of cerebrovascular disease.

A relation between hypertension, atherosclerosis, and stroke is well documented in humans. We report a similar relation in two hypertensive cynomolgus monkeys with severe cerebral atherosclerosis. In our primate model hypertension is induced by surgical coarctation of the aorta. These monkeys, when fed an atherogenic diet, develop severe cerebrovascular atherosclerosis. In this setting two monkeys developed spontaneous cerebral hemispheric strokes that occurred during treatment of hypertension. Since the strokes were topographically related to severe atherosclerotic narrowing of cerebral arteries and occurred without evidence of either thrombosis or embolization, they are presumed to be related to disturbances of blood flow. In both humans and animals cerebral perfusion is autoregulated to a constant flow over a wide range of mean arterial blood pressures. In hypertension both the upper and lower limits of autoregulation are increased. With treatment of hypertension readaptation to more normal levels is reported to be inconsistent and slow to develop. It is therefore postulated that the strokes in these two monkeys were due to hypoperfusion as a result of the combination of pharmacologic reduction in blood pressure and severe occlusive atherosclerosis.

Animals↗
PubMed1984

The effects of protein deprivation on the nucleus locus coeruleus: a morphometric Golgi study in rats of three age groups.

In a previous morphometric Golgi study of the nucleus locus coeruleus we identified in rats fed a 25% casein diet 3 cell types, fusiform, multipolar and ovoid, and compared their age-related changes from 30 to 90 days and 90 to 220 days. In the present study we investigated the effects of an 8% casein diet, initiated prenatally and continued postnatally in the pups, using the same morphometric parameters at the same 3 ages. In these rats the majority of significant age-related changes were in primary and secondary dendritic spine density. On all 3 cell types between 30 and 90 days there was a decreased spine density followed by an increase between 90 and 220 days. These age-related changes closely followed those in controls and, as a result, when the two diet groups were compared at each age they showed only 4 significant differences out of 18 comparisons. In control rats these age-related changes in dendritic spine density in the nucleus locus coeruleus were diametrically out-of-phase with those found in the nucleus raphe dorsalis in a previous study. This is consistent with the postulated mutual inhibitory relationship between the nucleus locus coeruleus and nucleus raphe dorsalis. Comparison of these same events in the nucleus locus coeruleus and nucleus raphe dorsalis in the 8% casein diet rats show no evidence of an out-of-phase relationship. Thus, the relationship between these two closely related nuclei appears to be fundamentally altered by the 8% casein diet. In these comparisons of dendrite spine density and other parameters the 8% casein diet rats have shown in both the nucleus locus coeruleus and nucleus raphe dorsalis deficits and increases as compared to controls. In contrast, in morphometric Golgi studies of pyramidal and Purkinje cells undernutrition generally results in deficits or little change in the various parameters. This suggests that the adaptation of the non-pyramidal neurons in the present study is different from that shown by pyramidal and Purkinje cells.

Age Factors↗
PubMed1984

Nucleus raphe dorsalis in dementia of the Alzheimer type: neurofibrillary changes and neuronal packing density.

Within the reticulate core of the brain the nucleus raphe dorsalis (NRD) is a major site of predilection for the neurofibrillary tangle (NFT) in dementia of the Alzheimer type (DAT) and, according to some studies, its primary brain stem site. In a quantitative study we have shown in six aged control brains an average of 5.2 NFT per histological section or 25.8 per mm3 and in seven age-matched brains with DAT a highly significant six-fold increase, respectively 35.3 NFT per histological section or 188.5 per mm3. There was no significant difference between the two groups in overall neuronal cell packing density. There was, however, a significant decrease in a subpopulation of neurons in DAT, a large polygonal neuron. Despite the prominence of the NRD as a target for NFT, the actual proportion of affected NRD cells was small, 0.35% in controls and 2.25% in DAT.

Aged↗
PubMed1982

Nucleus locus coeruleus: a morphometric Golgi study in rats of three age groups.

Using Rapid Golgi and Nissl techniques, 3 major cell types: fusiform, multipolar and ovoid shaped cells were identified in the nucleus locus coeruleus of male rats. Each cell type was described and quantitated as to age-related changes between 30 and 90 and between 90 and 220 days of age. The orientation and dendritic architecture of each type of cell in the locus coeruleus and relationship of these cells to blood vessels in the locus coeruleus and to surrounding structures is also described. One hundred neurons per age group were measured as to their maximal linear extent and the number of spines on the somal surfaces were counted. Dendritic number, linear extent, diameter and number of spines along a 50 microns segment near the mid-point of dendritic extensions in an equal number of primary and secondary dendrites were quantified for each age group and comparisons of these parameters between each cell group were made. Axons of each cell type were defined as to their origin and general orientation and trajectory. Axon collaterals of multipolar cells were shown to be recurrent in type projecting back onto the dendrites and soma of multipolar cells. One of the most striking findings was that between 30 and 90 days there were significant decreases in spine density on both primary and secondary dendrites in all three cell types in the locus coeruleus. This was followed by significant increases in spine density on both primary and secondary dendrites between 90 and 220 days in each of the 3 cell types. It is of interest that these age-related cell changes in spine density in the nucleus locus coeruleus are exactly out-of-phase with those of the nucleus raphe dorsalis.

Age Factors↗
PubMed1981

The effects of protein deprivation on the nucleus raphe dorsalis: a morphometric Golgi study in rats of three age groups.

In a previous study we identified 3 cell types in the nucleus raphe dorsalis (NRD): fusiform, multipolar and ovoid. In the present study, we have investigated the effect of an 8% casein diet on these 3 cell types using quantitative techniques on rapid Golgi-impregnated neurons from rats of 3 different ages: 30, 90 and 220 days. Major and minor axes of the cell body and dendritic diameter were unaffected and primary dendritic linear extent was only slightly affected by the diet. All 3 cell types in control rats showed an increase in synaptic spines on both primary and secondary dendrites between 30 and 90 days followed by a decrease for all 3 of the cell types at 220 days. Protein-deprived rats failed to show these age-related changes. Other parameters of comparison showed clear differences between the 3 cell types. These differences could be readily seen when total synaptic spine input to the primary and secondary dendrites was calculated from the data on dendritic number, linear extent and spine density. When viewed in this way the fusiform and ovoid cells show either little change or a decreased synaptic input at all ages, while the presumed serotonergic multipolar cells showed an increase. This is in agreement with neurochemical studies in these rats showing increased levels of this biogenic amine in protein malnourished rats.

Aging↗
PubMed1981

Nucleus raphe dorsalis: a morphometric Golgi study in rats of three age groups.

Using Rapid Golgi and Nissl techniques, three major cell types: fusiform, multipolar and ovoid-shaped were identified in the nucleus raphe dorsalis of male rats at 30, 90, and 220 days of age. We have described the orientation and dendritic architecture of raphe cells as to type and the relationships of these cells to blood vessels and surrounding structures. For each cell type, the origin of the axon is characteristic. One hundred neurons per age group were measured at their maximal linear extent and the number of spines on the somal surface was counted. Dendritic number, linear extent, diameter and the number of spines along a 50 micron segment near the mid-point of dendritic length in an equal number of primary and secondary dendrites were quantified in each age group. The most striking age-related changes in the multipolar and ovoid-shaped cells were dendritic number, diameter and spine number as well as the number of perisomatic spines. The fusiform cells showed the least age-related changes. In general, the nucleus raphe dorsalis is organized as a reticular nucleus with neurons having few, straight and poorly ramified dendrites.

Aging↗
PubMed1979

Developmental protein malnutrition: influences on the central nervous system of the rat.

Our group has been carrying out interdisciplinary studies on the effects of prenatal and postnatal protein malnutrition on the developing rat brain. Anatomical, physiological, biochemical and behavioral approaches using the same animal model have revealed that protein malnutrition affects the brain at various levels, i.e., (1) anatomical, as revealed by Golgi findings of deranged dendritic trees on analysis of cortical and subcortical areas; (2) physiological, as revealed by delayed sleep pattern maturation, disturbances in seizure thresholds, slowing of sensory cortico-cortical and thalamocortical evoked potentials, and changed power in hippocampal theta activity; (3) biochemical, as revealed by marked increases in biogenic amines dating from birth, as well as modifications in tryptophan metabolism; and (4) behavioral, as revealed by various changes in responses to different kinds of aversive stimulation. Reversal studies have revealed that many changes are permanent and not amenable to nutritional rehabilitation even at birth, which is before the brain growth spurt in the rat. Our paradigm closely mimicks the human condition of low level, chronic protein undernutrition and thus reveals the underlying disturbances due to malnutrition. The dietary reversal studies are attempts at pin-pointing critical brain growth periods, beyond which recovery of functions is not possible.

Animals↗
PubMedDate not supplied

Symmetrical and asymmetrical changes in brain tissue with age as measured on CT scans.

Age-related changes in mean CT attenuation values of brain tissue were analyzed by an objective, automated technique. Study participants included 64 healthy men ranging in age from 31 to 87 years. Five CT slices from each individual were evaluated: the last ventricular slice and the next four supraventricular slices. Regression analyses indicated that specific regions in the brain change with age. A schematic reconstruction of these regions suggests that several brain regions are selectively altered with age. On the medial aspect of the cerebral hemisphere there was bilaterally symmetrical atrophy of the cingulate gyrus and sulcus, the adjacent interhemispheric frontal gyri, the parietooccipital sulcus, and the marginal branch of the cingulate sulcus. On the convexity of the cerebral hemispheres there was asymmetrical widening of the central and postcentral sulcus on the left, and the intraparietal sulcus on the right.

Adult↗
PubMedDate not supplied

Mossy fibers of the hippocampal formation in prenatal malnourished rats.

Timm's impregnated mossy fiber plexus, in five coronal levels throughout the hippocampal complex, of normal and prenatally protein deprived rats at 15, 30, 90 and 220 days of age were analyzed. Morphometric computer assisted image analysis, showed significant decrease in total extent of the mossy fibers area in the prenatally malnourished rats on postnatal day 15 at levels 2, 3, and 4; on day 90 at level 1, and on day 220 at all five levels. This pattern of diet effect is similar to that noted at the same ages in the prior studies of the granule cell dendrites (Brain, Res., 1990; 532:271-277, J. Comp. Neurol, 1991; 310:356-364). This similarity of effects at these loci suggests that the diet effects on the hippocampal trisynaptic circuit are closely linked to each other. In all loci the effect of the diet was most marked on P220, indicating the late appearance of dietary deprivation effects in the hippocampal formation.

Animals↗