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A J Patel

Publications and source records attributed to A J Patel.

At least 91 records · Page 5Linked to original sources
PubMed1985

Observations on cell growth and regulation of glutamine synthetase by dexamethasone in primary cultures of forebrain and cerebellar astrocytes.

Cell growth, development of glutamine synthetase and its regulation by glucocorticoids, were studied in primary cultures of two types of astrocytes derived from rat brain, one from newborn forebrain and another from either newborn or 8-day-old cerebellum. Cell number per dish increased linearly following an initial decrease due to removal of non-astrocytic cells, and after the second week reached a stationary phase in both types of cultures at more or less the same time, although the cell number in cerebellar cultures was about 35% lower than in forebrain cultures of the same age. At all ages, irrespective of cell density, the cerebellar astrocytes were larger in size than the forebrain astroglial cells. The developmental curves for glutamine synthetase activity were similar in vitro and in vivo; however, the increase in enzyme activity in vitro was significantly greater than in vivo and this difference was more marked in forebrain than in cerebellar cultures. Throughout the period studied the specific activity of glutamine synthetase was significantly higher in forebrain astrocytes than in cerebellar astroglial cells. Treatment with dexamethasone caused a marked increase in the specific activity of glutamine synthetase. However, in agreement with our previous in vivo findings, the steroid induction in forebrain astrocytes was significantly less than that in cerebellar astrocytes. In culture, both types of astrocytes remain responsive to the hormone for longer than in vivo. The differences in the biochemical properties of the forebrain and cerebellar astrocytes seem to be intrinsic, and not related to the cell density or to the purity of the cultures.

Age Factors↗
PubMed1985

Concentration of free amino acids in primary cultures of neurones and astrocytes.

The cellular distribution of free amino acids was estimated in primary cultures (14 days in vitro) composed principally of cerebellar interneurones or cerebellar and forebrain astrocytes. In cultured neural cells, the overall concentration of amino acids resembled that found in brain at the corresponding age in vivo. In the two neural cell types, there were marked differences in the distribution of amino acids, in particular, those associated with the metabolic compartmentation of glutamate. In neuronal cell cultures, the concentrations of glutamate, aspartate, and gamma-aminobutyric acid were, respectively, about three, four, and seven times greater than in astrocytes. By contrast, the amount of glutamine was approximately 65% greater in astroglial cell cultures than in interneurone cultures. An unexpected finding was a very high concentration of glycine in astrocytes derived from 8-day-old cerebellum, but the concentrations of both serine and glycine were greater in nerve cell cultures than in forebrain astrocytes. The essential amino acids threonine, valine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, and arginine were all present in the growth medium, and small cellular changes in the contents of some of these amino acids may relate to differences in their influx and efflux during culturing and washing procedures. The present results, together with our previous findings, provide further support for the model assigning the "small" compartment of glutamate to glial cells and the "large" compartment to neurones, and also underline the metabolic interaction between these two cell types in the brain.

Amino Acids↗
PubMed1985

Effects of undernutrition and thyroid state on the ontogenetic changes of D1, D2, and D3 brain-specific proteins in rat cerebellum.

Disturbances in metabolic balance brought about by alterations in thyroid state and undernutrition during early life had a marked effect on the concentrations of the brain-specific proteins, D1, D2, and D3 in the developing rat cerebellum. In normal rats, the concentrations of D1 and D3 increased and that of D2 decreased during the first 3 weeks after birth. In the hyperthyroid state a small but consistent advancement was observed in the developmental curves of these proteins. The hypothyroid state caused a marked retardation in the maturational pattern of D1 and D2 but not of D3. In undernutrition, at 6 days the concentrations of D1 and D3 proteins were higher than in controls, but thereafter the developmental increase was markedly delayed for D1 only. The concentration of D2 was normal at 6 days, but after the first week a marked retardation was observed in the maturational pattern of this protein in undernourished rats. In addition, the "anodic-immature" form of D2 predominated in 6-day-old controls, but this was gradually replaced by a "cathodic-mature" form which progressively became the dominant form of D2 in 35-day-old rat cerebellum. The developmental switch in terms of the two forms was also advanced in hyperthyroidism and retarded in thyroid deficiency and undernutrition. Furthermore, daily treatment of hypothyroid rats with physiological doses of thyroxine from birth restored the concentrations of D1 and D2 to normal, but that of D3 was increased above control levels, indicating differences between the proteins in their sensitivity to mechanisms of control by thyroid hormone. Also, the overall effects of undernutrition were markedly different from those of hypothyroidism.

Age Factors↗
PubMed1984

Developmental changes in the amount of glial fibrillary acidic protein in three regions of the rat brain.

Glial fibrillary acidic (GFA) protein, extractable in 50 mM phosphate buffer, pH 8, was measured in the olfactory bulbs, forebrain and cerebellum of the rat during development using a double antibody radioimmunoassay. Each brain region showed a different pattern of development for GFA protein. At birth GFA protein per mg protein was highest in olfactory bulbs followed by forebrain and cerebellum, and these amounted to 15, 10 and 8% of the adult values, respectively. The relative increase in GFA protein was more marked during the first 2 postnatal weeks than in the following 7 weeks after birth. When values were expressed per brain region, the developmental increase in the amount of GFA protein from birth to adulthood was about 100-fold in olfactory bulbs, 85-fold in forebrain and 485-fold in cerebellum. The patterns of developmental increases in GFA protein and in glutamine synthetase activity, another protein enriched in astrocytes, were similar in the forebrain and olfactory bulbs, but differed markedly in the cerebellum. The major increase in content of the GFA protein during development was found to correspond with the maturation of astrocytes rather than with their proliferation; however, a small but significant amount of GFA protein acquired at an early age may be related to increase in astroglial cell numbers in the cerebellum.

Age Factors↗
PubMed1983

Regulation of in vivo glutamine synthetase activity by glucocorticoids in the developing rat brain.

Induction of glutamine synthetase in vivo by glucocorticoids was studied in different brain regions of the rat during development. Corticosterone treatment resulted in an age-dependent increase in glutamine synthetase activity. In 11-day-old rats, in comparison with controls, the increase was about 80% in the cerebellum, 50% in the olfactory bulbs and 20% in the forebrain. During development the effect diminished markedly and at day 20 a marked increase was detectable only in the cerebellum, suggesting that the elevation of glutamine synthetase was dependent on the maturational state of the region at the time of hormone treatment. The increase in enzyme activity was dose-dependent, and was also observed after treatment with dexamethasone but not with testosterone, estradiol or progesterone. Pre-treatment with the protein synthesis inhibitor anisomycin blocked the hormonal response. Also, immunochemical detection of glutamine synthetase in brain homogenates fractionated by SDS-polyacrylamide gel electrophoresis and transferred to diazobenzyloxymethyl paper showed that the increase in enzyme activity was due to induction of protein synthesis. This may be the first report showing a regulation by glucocorticoids of mammalian brain glutamine synthetase in vivo, and it is in good agreement with previous findings with chick retina in vivo and various avian and mammalian cells in vitro.

Age Factors↗
PubMed1983

Mitochondria in the postnatally developing rat cerebellar cortex: a morphological and biochemical study.

Ultrastructural changes during development in the proliferating cells of the external granular layer and the granule cells of the internal granular layer of the rat cerebellar cortex were examined. Changes in the number of free ribosomes, development of membrane systems, nuclear appearance and the number of cristae and matrix density of mitochondria suggested that both the round and elongated cells of the external granular layer and the granule cells of the internal granular layer were at same stage of maturation at any given age. Quantitatively, the relative volumes of cytoplasm and of mitochondria in the granule cells of internal granular layer were significantly higher than in the proliferating external granular layer cells; however, mitochondrial density and its increase during development were not significantly different in the two cell populations. The activity of the mitochondrial enzyme, succinate dehydrogenase, was also similar in ultrastructurally preserved and metabolically competent perikaryal fractions enriched in replicating external granular layer cells, granule cells and Purkinje cells. These findings emphasize the similarities between proliferating external granular layer cells and granule cells of internal granular layer. They lend support to the view that these cell types at the ages examined, represent a continuum of maturation towards full neuronal differentiation.

Animals↗
PubMed1983

Cell death in the external granular layer of normal and undernourished rats: further observations, including estimates of rate of cell loss.

Pyknotic nuclei in the external granular layer (EGL) of the rat cerebellum accounted for 0.6-0.8% of the total cell population in the first and third post-natal weeks and 1.4% at day 12. A wave of cell death induced by hydroxyurea showed an exponential decrease after 12 hr, from which a mean duration for pyknoses of about 6.5 hr was calculated. Undernutrition delayed the clearance of pyknotic nuclei following hydroxyurea, the mean duration being 24.5 hr. It is concluded that cell death does not significantly influence cell acquisition in the developing cerebellar EGL, and that the increased pyknotic index seen in the EGL of undernourished rats is a consequence of delayed clearance rather than an increase in the number of cell deaths.

Animals↗
PubMed1983

The past, present, and future of clinical specular microscopy.

Since the introduction of specular microscopy into the field of clinical ophthalmology in 1975, many technological and methodological advances have been made. These have for the most part eliminated the previously discussed objections to the use of specular microscopy as a clinical tool. With the advent of new instrumentation, a number of specular microscopes are not available. The advantages and disadvantages of these clinical specular microscopes, current clinical practice with small-field and wide-field specular microscopy, and description of problems and possible future developments of specular microscopy are discussed.

Cornea↗
PubMed1982

Effect of central nervous system acting drugs on brain cell replication in vitro.

The role in the regulation of cell replication of the neurotransmitter compounds and the drugs which affect their balance was studied in vitro, using morphologically preserved brain slices. Compounds affecting noradrenergic, dopaminergic and serotoninergic neurotransmitter systems reduced the brain cell replication, measured in terms of the rate of [3H]thymidine incorporation into DNA. The reduction was dose dependent and half-maximal effects were obtained at about 1-5 x 10(-4) M concentrations. Although agonists and antagonists both showed similar inhibitory effect, the action of agonists was reversed by the appropriate antagonists. Also, the pharmacologically active isomers were several-fold more effective than the inactive isomers in forebrain slices, although with cerebellar slices the selectivity was less marked. Cyclic nucleotides and drugs affecting cholinergic neurotransmitter systems were apparently ineffective. These results indicate that monoamines may be involved in the regulation of cell replication in the developing brain. Furthermore, as some of the CNS acting drugs tested are suspected behavioural teratogens the present results suggest that the reported behavioural abnormalities in the offspring may be related, in part, to a chronologically determined interference with the formation of certain cell types.

Animals↗
PubMed1982

The activities in different neural cell types of certain enzymes associated with the metabolic compartmentation glutamate.

The cellular distribution of certain enzymes associated with the metabolic compartmentation of glutamate was estimated in ultrastructurally preserved and metabolically competent perikarya fractions that were enriched in astrocytes, granule cells and Purkinje cells and derived from 8-day-old rat cerebellum, and in monolayer cultures (14 days in vitro) composed principally of interneurones or astrocytes. The neuronal activities of glutamine synthetase and glutamate dehydrogenase were respectively about 4- to 8-fold and 2- to 5-fold lower than in astrocytes, depending upon the class of neurone and the type of preparation used for comparison. By contrast glutaminase activity was about 3- to 12-fold higher in neuronal than in astroglial preparations. Estimations of the specific activity of succinate dehydrogenase differed less between cell types, indicating that the differences in glutamate dehydrogenase and glutaminase were not simply related to variations in the concentration of mitochondria relative to the other cellular constituents. The findings presented provide direct evidence in support of our model assigning the 'small' glutamate compartment, where most of the labelled glutamine is synthesized, to glial cells, and the 'large' compartment to neurones, and also underline the metabolic interaction between these two cell types in the brain.

Animals↗
PubMed1981

Indolic substances in plasma, cerebrospinal fluid, and frontal cortex of human subjects infused with saline or tryptophan.

Psychiatric patients undergoing the psychosurgical operation of stereotactic subcaudate tractotomy were infused intravenously with either saline or L-tryptophan (15 mg/kg/h). Plasma, lumbar cerebrospinal fluid (CSF), ventricular CSF and a specimen of frontal cortex were collected. The relationships of plasma concentrations of substances claimed to influence brain tryptophan concentration (total tryptophan, free tryptophan, large neutral amino acids) with the concentration of tryptophan in the cortex and CSF were investigated. Tryptophan infusion resulted in plasma tryptophan values comparable to those found after oral doses used in treating depression or insomnia, and about sixfold increases of tryptophan in the cerebral cortex. Increased brain 5-hydroxytryptamine synthesis was indicated by significant rises of CSF 5-hydroxyindoleacetic acid. The concentration of plasma free tryptophan was a better predictor than plasma total tryptophan of cortex tryptophan concentration. As all correlation coefficients of plasma versus brain or plasma versus ventricular CSF tryptophan concentrations were decreased when allowance was made for differences of concentration of large neutral amino acids, the results suggest that the role of these substances within their physiological range as inhibitors of tryptophan transport to the brain may previously have been overemphasised.

Cerebral Cortex↗
PubMed1981

[Joint prostheses].

Since 34 years, many improvement occurred. Joint prosthesis have to be anatomic, simple, thin and not a large foreign body. New material are warranted for their solidity. Many types are manufactured. The most used are hip prosthesis. Junction between bone and prosthesis is not solved as yet. Acrylic cement was on interface junction but in order to solve the failures, new porous or rough surface materials allowed anchorage by the bone itself. Prosthesis longevity is limited by bone prosthesis interface. Prosthesis replacement is possible and will develop.

Humans↗