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Biomedical subjects

H C Agrawal

Publications and source records attributed to H C Agrawal.

At least 55 records · Page 3Linked to original sources
PubMed1981

Demonstration of five major glycoproteins in myelin and myelin subfractions.

Myelin was found to contain five major glycoproteins with molecular weights of 120000, 95000, 88000, 43000 and 38000. Light myelin contained only 5-7% of the amount of these glycoproteins in whole myelin, whereas heavy myelin and the membrane fraction contained amounts nearly identical with whole myelin. Since all the major and minor glycoproteins, with the exception of 120000-mol-wt. glycoprotein, were detected only after treating the myelin membrane with neuraminidase, N-acetylneuraminic acid is a terminal sugar residue in these glycoproteins.

Animals↗
PubMed1981

Radioimmunoassay for central nervous system myelin-specific proteolipid protein.

A double-antibody radioimmunoassay (RIA) has been developed with antisera to purified rat brain myelin proteolipid protein (PLP). The addition of Triton X-100 allowed antibody-antigen interaction and immune precipitation in the presence of sodium dodecyl sulfate (SDS). The RIA will accurately measure 8-80 ng of PLP in buffer or human serum. The RIA is highly specific for myelin PLP and does not cross-react with material in tissues (heart, kidney, muscle, testicle, and intestine) other than the central nervous system. The antibodies to rat myelin PLP cross-react with PLP from bovine brain homogenate or myelin. Myelin PLP was found to account for 55 and 52% of total myelin protein from bovine and rat brain, respectively. Furthermore, there is a higher concentration of PLP in white than in gray matter corresponding to the degree of myelination. Unlike myelin basic protein, myelin PLP was undetectable in both bovine and rat peripheral nervous system.

Animals↗
PubMed1979

A comparative study of the immunohistochemical localization of basic protein to myelin and oligodendrocytes in rat and chicken brain.

Antisera to highly purified basic protein (BP) from rat and chicken brain were prepared and their purity and specificity demonstrated by double immunodiffusion and cross-immunoadsorption. These antisera were used for immunohistochemical localization of BP in the brains of adult and developing rat and chick. Myelin basic protein was exclusively localized to myelin or the myelin forming elements of the CNS. It was present in high concentrations in white matter and absent in areas free of myelin. Neuronal parikarya and dendrites were negative as were axons cut in cross section and at Nodes of Ranvier. The latter was best observed in cross sections of human spinal cord demonstrating also the immunoreactivity of the antibodies with human BP. The internodal distance in a fine (1.5 micrometer) rat cortical fiber was determined to be approximately 45 micrometers. Myelin basic protein was shown to extend into cranial roots, in contrast to myelin proteolipid protein which abruptly lose fluorescence as the nerves emerged from the brain. During development, BP was first observed on the fourteenth day of incubation in chick and at birth in the rat. The protein appeared in oligodendrocytes and in association with fibers near these cells. Fluorescent processes were frequently observed connecting the oligodendrocytes with the fibers. As myelination progressed, the intensity of the immunohistochemical reaction decreased in the oligodendrocytes while the brightness in fibers increase. Eventually, the oligodendrocytes became undetectable. Fibers with immature myelin exhibited a beaded or varicosed appearance with the highest concentration of immunofluorescence in the outer portion of the varicosities. The varicosities were postulated to represent dilations in the newly forming sheath between intervals of compaction along the axon undergoin myelination. These dilations might represent areas of increased cytoplasmic volume which could serve as channels for transport and/or storage sites for myelin proteins prior to incorporation into the membrane. The varicosities became less prominent with the thickening of the myelin sheath and mature myelinated fibers became smooth. The process of synthesis of BP, transport of the protein to the varicosed fibers, and maturation of the myelin sheath was seen to progress in a more or less caudal to rostral direction as myelination of the CNS takes place. In the rat, this was accomplished over approximately a 30-day period starting near the time of birth. In the chick, most of the myelination was accomplished in the three or four days immediately before hatching. At this time, innumerable oligodendrocytes were observed producing BP simultaneously in the major white fiber tracts. It is postulated that in chick some degree of oligodendrocytic cell death occurs normally during myelination.

Animals↗
PubMed1977

Turnover of myelin proteins in mouse brain in vivo.

The incorporation of tyrosine into proteins was measured after the subcutaneous implantation of a pellet of [14C]tyrosine in mice. This method keeps the specific radioactivity of free tyrosine fairly constant and makes it possible to follow incorporation up to a 10-day period. At the end of 10 days most of the protein-bound tyrosine was replaced (i.e. most protein turned over) in lung, liver, heart, kidney and spleen; about half was replaced in brain, one-quarter in muscle. The rate of protein turnover in myelin was approx. 40% of that of whole brain proteins; at 10 days one-fifth of the myelin proteins were replaced. All protein components of myelin measured were in a dynamic state; incorporation decreased in the following order, Wolfgram greater than DM-20 greater than basic greater than proteolipid proteins. The incorporation of tyrosine into each protein fraction was greater in the 0-5-day than in the 5-10-day period, indicating heterogeneity of metabolic rates. The results show that after myelination at least a portion of each protein component of myelin is undergoing significant metabolic turnover. In the adult, myelin components are not stable, but turnover is heterogeneous, and each protein may be compartmentalized. Turnover can be influenced by a variety of factors.

Animals↗
PubMed1976

Morphological and biochemical characterization of light and heavy myelin isolated from developing rat brain.

Myelin from developing rat brains was separated on a discontinuous sucrose gradient into subfractions of two different densities, i.e. light and heavy myelin. Electron photomicrographs showed that heavy myelin consisted primarily of large compacted multilamellar structures with a distinct intraperiod line characteristic of myelin in situ. Light myelin, on the other hand, was composed of small vesicles having a unilamellar structure. Similar to whole myelin, both membrane subfractions were highly enriched in 2',3'-cyclic nucleotide-3'-phosphohydrolase. The specific activity of the enzyme, however, showed no developmental trend. Both subfractions contained all the four major proteins characteristic of the whole myelin membrane. There were, however, quantitative differences in the relative distribution of these proteins between light and heavy myelin. Basic protein accounted for 55% and proteolipid protein for 46% of the total myelin proteins of light and heavy myelin, respectively. DM-20 (Agrawal, H.C., Burton, R. M., Fishman, M.A., Mitchell, R.F. and Prensky, A.L. (1972) J. Neurochem. 19, 2083-2089) exhibited a developmental "switch" between light and heavy myelin. Light myelin appeared to contain more DM-20 in 15- to 20-day-old rat brain, whereas the concentration of this protein was higher in heavy myelin at subsequent ages studied.

Aging↗
PubMed1976

Accumulation and turnover of the classical Folch-Lees proteolipid proteins in developing and adult rat brain.

The turnover of classical Folch-Lees proteolipid proteins was studied after administration of [2,3-3H]tryptophan to both developing and adult rat brain. The animals were killed from 2h to 250 days after subcutaneous injections of [3H]tryptophan. The measured specific radioactivity in developing brain attained maximum value 24h after the administration of label, whereas the total radioactivity per brain reached a maximum 21 days after injection. The half-life of proteolipid protein from the measured specific radioactivity was 7-20 days, depending on the time-points used for the calculation, whereas calculation from total radioactivity between 28-77 and 91-257 days gave half-lives of 35-40 and 188 days respectively. In contrast, in animals injected at 40 days of age, the half-life from the whole-brain-radioactivity data was 188 days. The problem of the recycling of radioactivity for the synthesis of myelin proteins from either a general or a discrete amino acid pool is discussed.

Age Factors↗
PubMed1975

Relation of C-6 glial cells in culture to myelin.

C-6 glial cells were shown to contain enriched in their plasma membranes an enzyme, 2':3'-cyclic nucleotide 3'-phosphohydrolase, characteristic of myelin, and, in addition, proteolipid protein and two basic proteins that are identical in their electrophoretic mobilities with the respective proteins found in myelin. The data indicate that C-6 cells exhibit features of myelin-producing glia as well as astrocytes.

Acetylcholinesterase↗
PubMed1974

Metabolic studies on myelin. Evidence for a precursor role of a myelin subfraction.

Myelin prepared from brain tissue of the developing rat (15 days post partum) can be separated into several subfractions. These are (1) ;myelin-like' and ;purified myelin', by the technique of Davison and co-workers (Agrawal et al., 1970b) and (2) ;membrane fraction,' ;light myelin' and ;heavy myelin' by the discontinuous-sucrose-gradient procedure described in the present paper. ;Myelin-like' and ;membrane-fraction' subfractions appear to be similar in chemical properties, but different in detailed morphology by electron microscopy. Both fractions are related to myelin, on the basis of demonstrable myelin basic protein by polyacrylamide-gel electrophoresis in sodium dodecyl sulphate and the presence of a myelin-marker enzyme, 2':3'-cyclic nucleotide 3'-phosphohydrolase. These two fractions have a low lipid content (17% for ;myelin-like' and 40% for ;membrane-fraction' subfractions) compared with myelin (67-72%). No cerebroside was detected in these two fractions, whereas cerebrosides are a major component of myelin itself. The administration of [2,3-(3)H]tryptophan to young rats results in more rapid incorporation into proteins of the ;myelin-like' and ;membrane-fraction' subfractions when compared with incorporation into myelin. Data are presented which are consistent with a precursor-product relationship for conversion of ;myelin-like' and ;membrane-fraction' subfractions into myelin.

Animals↗