Neurobiology最新文献

A cell suspension was prepared by sieving mouse brain cortices in an isotonic solution of purified polyvinylpyrrolidone. A large increase on the O2-uptake by the suspension could be obtained with the preparation procedure described. The respiratory rate of suspension, incubated in saline medium, containing 6.2 mM K+, 10 mM pyruvate, 5 mM fumarate and 0.9 mM 5'-AMP, was equal to 68% of the respiratory rate of slices. High K+ concentration (65 mM) stimulated O2-consumption of suspension by 64% (73% in slices).

The "chloride space" in brain tissue of 15- and 19-day-old chick embryos was studied during the 3 h following intracerebral administration of 3.4-10(-4) M ouabain. Total tissue water, dry substance, plasma and liquor and tissue chloride concentrations were determined. The chloride space in brain tissue was calculated on the basis of the brain-cerebrospinal fluid ratio and the brain-plasma ratio. The chloride concentration in blood plasma was generally unchanged after ouabain treatment. The chloride concentration in cerebrospinal fluid was lower in younger embryos during the whole 3-h period, whereas in 19-day-old embryos only during the 1st h. Tissue chloride concentration was generally elevated, but to a greater extent in younger embryos. Total brain tissue water increased for 3 h after ouabain treatment in 15-day-old embryos and for the first 2 h in 19-day-old embryos. The expansion of chloride space reached a new steady state during the 1st h after ouabain treatment and amounted to 12-15% of control values in 15-day-old embryos. The increase of chloride space in older embryos reached its maximum (14.8% of control values) within the 1st h and gradually decreased thereafter. The age-dependent changes of chloride compartmentation in embryonic brain tissue are discussed in relation to the previously investigated spongy state of the brain tissue in chick embryo.

Following 30-min intermittent post-tetanic potentiation of monosynaptic reflexes in the ventral horn of the spinal cord of 10 cats, the amino acid composition was analyzed after reacting with 14C-dansylchloride and by two-dimensional chromatography. The amino acids in comparable segments of the spinal cord from eight animals after ether anesthesia and from five animals who were operated on but not stimulated were also analyzed. In the latter the operation itself influenced the amino acid composition as compared to those animals who were anesthetized. Comparison between the different control groups showed that the operated animals can be used as a control for calculation of the changes caused by potentiation. The amino acids glycine, glutamic acid and aspartic acid, which act as either inhibitory or excitatory neurotransmitters, increased significantly after potentiation, as did the amino acids lysine, histidine, leucine, isoleucine, and proline.

The brain specific S100 protein has been demonstrated by immunofluorescence microscopy on neuronal cell membranes during postnatal development of rat, rabbit and guinea pig. S100 has been found in glial cell aggregates of rats 4-5 days old, of rabbits 2-3 days old, and of newborn guinea pig. The neuronal plasma membrane-bound portion of the protein appears later during development. In rats 10 to 12 days of age S100 could be found on one part of the cell membrane of Deiters' neurons and of Purkinje cells. In rats 12 to 15 days old cells from the cerebral cortex contained a heterogeneously distributed cell membrane-bound portion of S100. The protein on neuronal cell membranes could be seen somewhat earlier in rabbits as compared to rats. Newborn guinea pigs showed a heterogeneous distribution of the protein similar to that seen in adult animals. In rat and rabbit adults distribution and amounts of S100 were reached at days 25-30 and at days 20-24, respectively. The results obtained here are in agreement with biochemical results. Our findings suggest that the membrane-bound part of the S100 protein with its heterogeneous and polar distribution on the nerve cell plasma membranes (demonstratable in parallel with physical and behavioral maturation of the animals) is a sign of a protein differentiation of the neuron.

The sites of synthesis of the low molecular weight beta-trace protein, present in a seven times higher concentration in normal human CSF than in normal human serum, have been studied by means of a radioactive immunoprecipitation method. Adult squirrel monkey tissues were cultured in Eagle's minimum essential medium in the presence of 14C-labelled valine, threonine and leucine for 24 hours. Synthesis could be demonstrated in cultures of white CNS matter, whereas cultures of grey CNS matter, peripheral nerve, skeletal muscle, kidney and ovary did not show any signs of synthesis. Some cultures of spinal cord, basal ganglia, genital organs except ovary, and liver showed a probable synthesis of beta-trace protein. By means of autoradiography, the synthesis of beta-trace protein in white CNS matter could be confirmed.

Pyridoxine deficiency produced in rats during the period of development of the central nervous system resulted in a decreased incorporation of (1-14C) acetate into total lipid extracts of brain. It also resulted in a uniform decrease in the incorporation of the labeled precursor into the cholesterol, glycolipid and phospholipid fractions of brain. The specific radioactivity of purified cerebrosides and sulfatides was decreased by 78% in pyridoxine-deficient rats with respect to controls. The decreased incorporation of labeled precursor in the deficient rats was not due to the labeled precursor, since the specific radioactivity of brain acetate and the brain concentrations of acetyl coenzyme A and acetate were similar in both deficient and control rats. The results indicate that in pyridoxine deficiency established in the young rat there is an impaired formation of myelin.

Astrocytes and neuronal and oligodendroglial perikarya isolated by the method of Norton and Poduslo (1970) were examined by transmission and scanning electron microscopy and inverted phase contrast microscopy. The viability of the cells, as determined by the eosin exclusion method, was also determined. The three cell fractions showed only slight cross-contamination, but the astrocyte fraction contained significant amount of small debris. The ultrastructural appearance of the cells indicated that much of the in situ properties were retained, with bundles of fibrils preserved in astrocytes with well-defined plasma membranes. Oligodendroglial perikarya were found to be the best preserved of the cell types. The viability studies indicated that about 90% of the cells excluded eosin. Scanning electron microscopy revealed the neuronal cell surface to be rough and studded with knob-like bodies. Oligodendrocytes tended to aggregate and demonstrated a much smoother surface than the neurons.

The activity and distribution of the enzyme acetylcholinesterase in the cerebellum of adult lurcher (Lc) mutant mice and of their normal littermates was investigated using biochemical assay and light microscopic histochemistry. The biochemical assay demonstrated an approximate two-fold increase of enzyme activity in the lurcher cerebellum compared to the values obtained for the normal controls. Acetylcholinesterase activity in the cerebellum of the normal adult mouse was predominantly evident in the granular layer, corresponding to the location of the glomeruli. In contrast, the lurcher cerebellum exhibited enzyme activity in both molecular and granular layers. In the molecular layer the staining appeared to be associated with ectopic granule cells. In both normal and lurcher mice, the Golgi cells, subcortical white matter and deep nuclei also showed varying degrees of staining for acetylcholinesterase.

The nuclear size and density of oligodendrocytes in corpus callosum were investigated in rats with CCl4-induced hepatic encephalopathy. An increase in density (15 per cent) of oligodendroglial nuclei was found after 8 weeks of CCl4-administration. Measurements using an electronic image analysing system demonstrated a simultaneous decrease (13 per cent) in the nuclear size. It was concluded that these changes were due to an increase in the number of oligodendrocytes with small, dark nuclei. The corpus callosum did not show significant signs of axonal or myelin degeneration. In the cortical and subcortical grey matter degenerated neurones were observed; the oligodendroglial proliferation could, possibly, be a reaction to neuronal degeneration.

Dissociated cells from 7-day-old chick embryo cerebral hemispheres were cultivated on collagen in Falcon Petri dishes in the presence of various concentrations of fetal calf serum and of a chemically synthesized tripeptide Gly-His-Lys. Four different culture conditions were employed in the composition of the nutrient medium in which the cells were cultivated: a low serum concentration of 1, 2 or 5% (group A), a low serum concentration with 200 ng/ml tripeptide (group B), a serum concentration of 10 to 20% (group C) and a serum concentration of 10 or 20% with 200 ng/ml tripeptide (group D). Within the first 24 h of cultivation the cells settled on the collagen substrate and outgrowth of neuronal processes started in all four culture conditions. After 48 h in culture, differences between the groups became evident. In group A most isolated nerve cells had disappeared and glial cells proliferated from the remaining clumps. In group B the neurons had differentiated in absence of glial cells, the proliferation of which was greatly suppressed. In group C and D a differentiation of neurons occurred in a similar way to group B, but in addition the glial cells had proliferated. After 7-8 days in culture the cells in group A and B suddenly degenerated. In group C and D the nerve cells maintained for up to 3 weeks. The optimum concentrations of tripeptide in which the neuroblasts grew fibers and maintained in culture during 7-8 days were in the range of 100-400 ng/ml. The role of the tripeptide in the differentiation and maintenance of nerve cells is discussed.