Developmental changes in polypeptide composition of, and precursor incorporation into, cellular and subcellular fractions of rat cerebral cortex

Developmental differentiation of MAP2 expression in the central versus the peripheral and efferent projections of the inner ear

The goal of this study was to extend our knowledge of MAP2 localization in the peripheral nervous system of mammals, since most results on MAP2 distribution are obtained in the central nervous system (CNS). This study shows the presence of microtubule-associated protein 2b (MAP2b) and MAP2c in the inner ear and describes the immunocytochemical distribution of MAP in adult and developing spiral ganglion of the rat by using a well-characterized antibody for MAP2a and MAP2b. (This antibody does not recognize the immature MAP2c). MAP2 labeling is already present in spiral ganglion neurons at 16 days of gestation. From this stage and up to the first postnatal week, MAP2 labeling was strong in all spiral ganglion neurons and their central processes. Double immunostaining at the 16-day stage with anti-MAP2 and anti-neurofilament (NF) antibodies mainly showed NF labeling in central branches that corresponded to anatomically and functionally described axons of spiral neurons. The peripheral branches lacked MAP2 labeling. In neonatal and postnatal stages, MAP2 reactivity was located in spiral ganglion perikarya and their neurites. The intensity of adult labeling was, however, lower than in younger animals. The antibody used in this study did not label axons originating in the CNS as seen by a negative response in efferent fibers from the intraganglionic spiral bundle of the cochlea. Our results suggest that during ontogenesis, MAP2 is highly expressed in the central projection of spiral ganglion neurons, and then is reduced to lower quantities in the central branch after the first postnatal week and persists into adulthood.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain protein changes during development and sexual differentiation in the rat

Subcellular fractions were prepared from the hypothalamus-preoptic area and the 'remainder of the brain' of intact male and female rats at 0, 8, 25 and 72 days of age. Proteins associated with each fraction were subjected to SDS-PAGE chromatography and stained with Coomassie Brilliant Blue. Developmental changes were found to occur in proteins associated with the soluble (14,600, 15,000, 29,900, 38,900 and 49,000 mol. wt), nuclear (40,000-50,000 and 13,800-16,000 mol. wt.), mitochondrial-lysosomal (49,000-52,000 mol. wt.) and microsomal (14,400, 20,000, 50,100, 56,900 and 130,000 mol. wt.) fractions. In addition, soluble proteins were greater in males than in females at days 0 (53,000-56,000 mol. wt.; probably tubulin) and 25 (14,600 and 15,000 mol. wt.). These changes in brain proteins probably reflect important structural and functional changes that occur during maturation and sexual differentiation of the brain.

Glycoprotein composition and turnover in subcellular fractions from the cerebral cortex of normal and reeler mutant mice

Twenty-day-old reeler and normal mice were either injected intraventricularly with radiolabelled fucose before subcellular fractionation of the cerebral cortex followed by SDS-PAGE, or gels of such fractions were overlaid with [125I]concanavalin A (ConA). While there were no differences in polypeptide profiles of normal and reeler subcellular fractions there were marked differences in the abundance of particular ConA-binding glycoproteins and in fucose incorporation into particular glycoproteins, especially in the synaptic plasma membrane (SPM) and 100,000 g soluble fractions. In addition there was a significantly lower binding (greater than 50%) of quinuclidinyl benzilate to reeler microsomal and SPM fractions as compared with normal. The differences in glycoprotein expression may be pertinent to anatomical observations of abnormal interactions between neurons and glial fibres during development of the reeler cerebrum.

Concanavalin A binding glycoproteins in subcellular fractions from the developing rat cerebral cortex

Synaptic plasma membrane (SPM) and mitochondrial fractions were prepared from 3-50-day rat cerebral cortex and their purity assessed. The fractions were subjected to electrophoresis on slab gels, stained for protein, and overlaid with 125I-concanavalin A (ConA). ConA binding glycoproteins (CABGs) were revealed by autoradiography. In the SPM fraction CABGs of MW 25,000, 63,000, 80,000, 115,000, 174,000, and 239,000 increased while those of MW 47,000, 75,000, and 190,000 decreased developmentally. In the mitochondrial fraction, CABGs of MW 25,000, 44,000, 115,000 and 174,000 increased while those of 34,000, 43,000, 47,000, 51,000, 80,000, 107,000, and 195,000 decreased developmentally. CABGs of MW 32,000, 63,000, 88,000, 153,000, 190,000, and 239,000 appear to be unique to the SPM fraction and those of MW 34,000, 107,000, and 195,000 are unique to the mitochondrial fraction.

Developmental changes in the composition of, and precursor incorporation into, polypeptides of rat brain slices

Developmental changes in both polypeptide composition and incorporation of L-[3,4(n)-3H]valine into rat brain slice polypeptides have been monitored by SDS polyacrylamide gel electrophoresis coupled with fluorography. Six polypeptide bands (mol. wt 280, 210, 117, 66, 55 and 53 k) showed developmental decreases in relative amount whilst eleven others (mol. wt 230, 156, 95, 77, 68, 62, 48, 38, 34, 28 and 18 k) showed developmental increases. The majority of these changes were accompanied by corresponding, but not parallel changes in precursor incorporation. At least one polypeptide, mol. wt 44 k, showed a developmental decrease in precursor incorporation, but little change in relative amount. Localisation of these polypeptides in SPM, myelin and mitochondrial enriched fractions has been studied.

Polypeptide antigens of the synaptic plasma membranes of the rat brain

Antisera to two groups of polypeptides isolated from central nervous system synaptic plasma membranes of mature rats, were used to study antigenic polypeptides of new born and adult rats. Immunoprecipitation and acrylamide gel electrophoretic analysis demonstrated greater amounts of antigenic polypeptides in adult rats. These antigenic polypeptides may be involved in synaptogenesis.

Muscarinic acetylcholine receptors regulation and protein phosphorylation in primary cultures of rat cerebellum

Exposure of primary cell cultures of rat cerebellum to the muscarinic agonist carbachol led to a 50% loss in apparent muscarinic receptor number detectable in a ligand binding assay using [3H]quinuclidinyl benzilate ([3H]QNB). The loss in [3H]QNB binding was time-dependent with a half-life of 2.9 h. Examination of membrane protein phosphorylation indicated that exposure to carabachol resulted in an increase in the level of phosphorylation of 6 polypeptides. The increased phosphorylation of 3 of these polypeptides, of molecular weights, 75,000, 67,000 and 62,000, followed a similar time-course to that of carbachol-induced loss of receptor binding. These results are consistent with the idea that the muscarinic receptor regulation involves a protein phosphorylation mechanism.

Influence of prenatal hypoxia on brain development: effects on body weight, brain weight, DNA, protein, acetylcholinesterase, 3-quinuclidinyl benzilate binding, and in vivo incorporation of [14C]lysine into subcellular fractions

The influence of prenatal hypoxia on subsequent brain development in the young rat was investigated by examining body and brain weight, cerebral cortex wet weight, protein and DNA concentrations, acetylcholinesterase (AChE) activity, 3-quinuclidinyl benzilate (QNB)-binding levels, the relative amounts of protein in various subcellular fractions, and the in vivo incorporation of [14C]lysine into the protein of homogenate and subcellular fractions. Exposure of pregnant females to a mild hypoxia (9.1% O2, 10 h per day for the 9--11 days preceding birth) resulted in a reduced body weight in the pups and days 1 and 5 after birth; total cortical DNA was reduced but brain weight and protein content were unaffected, leading to a higher protein/DNA ratio in prenatally hypoxic pups. By 10 days of age these differences between prenatally hypoxic and control animals were no longer apparent. There were no differences between prenatally hypoxic and control animals in AChE and QNB binding per milligram cortex protein. The relative amount of synaptic membrane protein from the cerebral cortex was reduced at day 1 in prenatally hypoxic animals and the synaptic membrane fraction showed a higher level of incorporation of [14C]lysine on days 1, 5, and 10. The developmental profile of [14C]lysine incorporation showed a peak on day 10 which was higher in prenatally hypoxic rats. By 46 days after birth little difference could be found between prenatally hypoxic and control animals.

Increased incorporation of [3H]lysine into synaptic membranes of the visual cortex following first exposure of dark-reared rats to light is confined to particular polypeptides

The incorporation of [3H]lysine into separated polypeptides of synaptic-membrane fractions prepared from the visual cortices of dark-reared rats and littermates exposed to light for 1 h was examined. Increased incorporation of [3H]lysine was found in synaptic membranes from light-exposed compared to dark-reared rats in polypeptides of four molecular weights: 100,000, 71,000, 44,000, and 38,000. The 44,000-molecular-weight peak has been suggested to be actin on the basis of its comigration with pure brain actin. These results indicate that increased incorporation of [3H]lysine into synaptic membranes of the visual cortex, following first exposure of dark-reared rats to light, is confined to particular polypeptides.