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Biomedical subjects

M Paula-Barbosa

Publications and source records attributed to M Paula-Barbosa.

13 recordsLinked to original sources
PubMed1988

Granule cell loss and dendritic regrowth in the hippocampal dentate gyrus of the rat after chronic alcohol consumption.

The effects of chronic alcohol consumption (CAC) on the relative number of dentate gyrus granule cells and their dendritic trees, were studied in animals fed alcohol for 6, 12 and 18 months and in their respective controls. The granule cell density was estimated with the unbiased disector method. Following 6 months of alcohol consumption, the thickness of the dentate gyrus granular layer and the relative number of dentate granule cells were significantly decreased when compared with controls. The granule cell dendritic arborizations showed an increase of their dendritic extent in alcohol-treated rats. No significant differences were found in the density of dendritic spines between alcohol-fed and control animals. These results indicate the existence of hippocampal granule cell dendritic regrowth in alcohol-fed rats, probably occurring as a compensatory response to the granule cell deficit which follows the alcohol-induced granule cell degeneration. These degenerative and regenerative changes might have functional implications for the organization of the synaptic hippocampal circuitry after long periods of alcohol consumption.

Alcoholism↗
PubMed1988

Alzheimer's disease: coated vesicles, coated pits and the amyloid-related cell.

The amyloid-related cell (ARC) of the neuritic plaques of Alzheimer's disease revealed numerous cytoplasmic projections surrounding extracellular amyloid material. It is proposed that ARC-coated vesicles fuse with the cell membrane, forming coated pits, which may empty their secretory material into the extracellular space where polymerization of amyloid filaments could occur.

Alzheimer Disease↗
PubMed1988

Unbiased estimate of cerebellar granule cell numbers in hypothyroid and in sex-age-matched control rats.

Regardless the enormous amount of morphometric data related to the influence of thyroid hormones deficiency on the cerebellar cortex histogenesis, it remains controversial whether, in fully developed hypothyroid rats, the number of granule cells is actually altered. In order to get a quantitative unbiased view of its number at the end of the neurogenic period, we studied, using recently described stereological techniques, the granular layer of groups of 30 days old rats rendered hypothyroid from the day of birth. The results were compared with age- and sex-matched controls, as sex dimorphic differences were previously described for cerebellar granule cells. The granule cell packing density was increased independently of changes of their nuclear diameters. Its numerical density was similar in hypothyroid and controls, although a significant decrease in their total number was depicted as a consequence of the volumetric reduction of the granular layer in the hypothyroid groups. When male and female control groups were compared, the number of granule cells was found to be significantly smaller in females. This sex dimorphic difference was not detected between male and female hypothyroid groups, which suggests that, to be manifested, the presence of thyroid hormones is a necessary condition.

Animals↗
PubMed1988

Unbiased estimate of hippocampal granule cell numbers in hypothyroid and in sex-age-matched control rats.

Despite the similarities in the processes of cell acquisition between the hippocampal and cerebellar granular layers, it was suggested that changes induced by thyroid deficiency on the neurogenesis of their granule cells were region specific, leading to different end-results: a permanent decrease in the number of the dentate gyrus granule cells in hypothyroids, conversely to what occurs in the cerebellum, where their number is similar to those of controls or even increased. We decided to re-investigate this subject by applying to the hippocampal granular layer the same stereological techniques previously used for the cerebellum which allow a reliable comparative analysis. The sex of the animals was discriminated, as in rodents the hippocampal granule cells display sex dimorphic differences. No significant differences were found between the packing and numerical densities of granule cells in male and female groups of hypothyroid and control rats, as opposed to what happens to the total number of granule cells which was found to be reduced in the former groups. The number of granule cells was significantly increased in control male rats in comparison with control females. A similar sex difference was no longer observed between male and female hypothyroid animals, which suggests that the presence of sex dimorphic characteristics is related to the thyroid hormone levels. It is likely to admit that granule cell reduction might interfere with the hippocampus input and therefore contribute to underly the marked behavioral changes observed in cretinism.

Animals↗
PubMed1987

A quantitative study of frontal cortex dendritic microtubules in patients with Alzheimer's disease.

The dendritic microtubules (MT) of the frontal cortex layers II and III were studied in 9 patients with Alzheimer's disease (AD) and the results compared with 9 case controls. Dendrites with abnormally oriented MTs and others depleted of these structures were seen. A significant reduction in the number of MTs per unit area was found in AD. It is suggested that microtubular changes in AD can interfere with neuroplasmic transport and thus, be implicated with the dendritic degeneration present in this disease.

Aged↗
PubMed1979

Nuclear bodies in nerve cells of two patients with normal-pressure hydrocephalus.

Biopsy specimen fragments from two patients with normal-pressure hydrocephalus were studied using ultrastructural methods. Simple nuclear bodies were found in all layers of the cortex and white matter, whereas complex ones were only seen in the fifth and sixth layers and in the underlying white matter. There may be a relationship of these nuclear bodies, either to the neuroglial proliferation observed in both patients or to the existence of a viral infection of the CNS.

Adult↗
PubMed1977

The effects of different methods of fixation on central nervous system synaptic pinocytotic vesicles.

Synaptic pinocytotic vesicles (invaginating from the surface membrane) and coated vesicles inside rat mossy fiber endings were counted after the use of different kinds of fixatives. Significantly greater numbers of pinocytotic vesicles and coated pinocytotic vesicles per unit length of membrane were found when osmium was used as the first fixative. A high positive correlation was found between these values and the number of coated vesicles per unit area of mossy fiber ending profiles. The results emphasize the need for caution when considering the theory that in vivo synaptic vesicle recycling involves a coated vesicle invagination of the surface membrane followed by internalisation and loss of coat of the vesicle.

Animals↗
PubMed1976

Pentalaminar specialized membrane junctions - tight junctions - are described in the granular layer of the pigeon cerebellum. The presence of these axo-dendritique and dendrosomatic contacts suggest the existence of electrotonic coupling in the pigeon cerebellum.

Pentalaminar specialized membrane junctions - tight junctions - are described in the granular layer of the pigeon cerebellum. The presence of these axo-dendritique and dendrosomatic contacts suggest the existence of electrotonic coupling in the pigeon cerebellum.

Animals↗
PubMed1975

The duration of aldehyde fixation as a "flattening factor" of synaptic vesicles.

Synaptic vesicle flattening can be induced in the excitatory mossy fibre endings of the rat cerebellum by prolonged immersion in aldehyde during fixation (with or without perfusion). The flattening is found in a greater percentage of vesicles if perfusion has been omitted before the prolonged immersion. This is discussed in relation to the various other factors that are thought to cause flattening and the important problem of the classification of different types of synapse.

Aldehydes↗
PubMed1975

A Golgi and electron microscopical study of nerve cells in layer I of the cat auditory cortex.

The nerve cells of the plexiform layer of the cat auditory cortex were studied in Golgi rapid preparations, and by electron microscopy. In the Golgi material 178 cells were found. Thirty were horizontal cells (Cajal's cells) with spiny dendrites and a long axon with horizontal trajectory. Seventy-two small cells had smooth dendrites and a short axon branching profusely around the perikaryon, within the plexiform layer. Twenty-eight were slightly larger cells, morphologically similar to the small ones, but their axons and dendrites were longer, extending to layer II. Twenty-five cells had large bottle-shaped perikarya, spiny dendrites reaching layer II, and a vertically oriented axon branching in layer II, and sometimes reaching layer III. In addition, 23 small modified pyramidal cells, similar to those of layer II, were found within the boundaries of layer I. In the most superficial 50 mum of the cortex horizontal cells were found, but the other categories were very rare. The 3 categories of short axon cells were preferentially localized between 50 and 150 mum from the pial surface. By electron microscopy two classes of cells were found. The first had abundant mitochondria, well defined Nissl bodies and few axosomatic synapses. The second had few mitochondria, undefined Nissl bodies and 6-8 axosomatic synapses per profile. Desmosome-like membrane specializations were found between perikarya of the second class and pyramidal dendrites or their spines. It is suggested that the first class of cells found by electron microscopy may correspond to the horizontal cells while the second class may correspond to the 3 categories of short axon cells.

Age Factors↗
PubMedDate not supplied

Alzheimer's disease: paired helical filaments and cytomembranes.

Observations were made with the electron microscope on biopsies from the frontal cerebral cortex of four patients showing the clinical symptoms of advanced Alzheimer's disease (AD). Sections from all four biopsies showed neuronal dendrites, and to a lesser extent, perikarya, packed with paired helical filaments (PHFs) and a correlated complete loss of the normal content of microtubules. It was usually impossible to visualize the beginning and end of the PHF since it passed out of the plane of section. However, not infrequently, PHFs could be seen apparently arising at or from the surfaces of cytomembranes. Such membranes (in perikarya or dendrite) often formed irregular stacks or lamellated bodies. These membranes were invariably agranular (i.e. not studded with ribosomes) and so might be considered as pathological forms of smooth endoplasmic reticulum (SER). A correlation is established between the known biochemical nature of PHFs and their postulated membrane origin.

Alzheimer Disease↗