Biomedical subjects

O Koul

Publications and source records attributed to O Koul.

11 recordsLinked to original sources

PubMed1991

Developmental expression of HNK-1-reactive antigens in rat cerebral cortex and molecular heterogeneity of sulfoglucuronylneolactotetraosylceramide in CNS versus PNS.

Monoclonal antibody HNK-1 reacts with a carbohydrate epitope present in proteins, proteoglycans, and sulfoglucuronylglycolipids (SGGLs). On high-performance TLC plates, SGGLs of the CNS from several species migrated consistently slower than those from the PNS, a result indicating possible differences in the structures. The structural characteristics of the major SGGL, sulfoglucuronylneolactotetraosylceramide (SGGL-1), from CNS was compared with those of SGGL-1 from PNS. Although the composition, sequence, and linkages of the carbohydrate moiety of the SGGL-1 species were identical, SGGL-1 from CNS contained mainly short-chain fatty acids, 16:0, 18:0, and 18:1, amounting to 85% of the total fatty acids, whereas SGGL-1 from PNS contained large proportions (59%) of long-chain fatty acids (greater than 18:0). These differences in the fatty acid composition accounted for the different migration pattern observed. The developmental expression of SGGLs and HNK-1-reactive proteins was studied in rat cerebral cortex between embryonic day (ED) 15 to adulthood. SGGLs in the rat cortex were maximally expressed around ED 19 and almost completely disappeared by postnatal day (PD) 20. This expression was contrary to their increasing expression in the cerebellum and sciatic nerve with postnatal development. Six to eight protein bands with a molecular mass of greater than 160 kDa were HNK-1 reactive in the rat cerebral cortex at different ages. The major HNK-1 reactivity to the 160-kDa protein band seen in ED 19 to PD 10 cortex decreased and completely disappeared from the adult cortex, whereas several other proteins remained HNK-1 reactive even in the adult. Western blot analyses of the neural cell adhesion molecules (N-CAMs) during development of the rat cortex with a polyclonal anti-N-CAM antibody showed that the major HNK-1-reactive protein bands were not N-CAMs. Between PD 1 and 10, 190-200-kDa N-CAM was the major N-CAM, and between PD 15 to adulthood, 180-kDa N-CAM was the only N-CAM present in the rat cortex.

Amino Acid Sequence↗

PubMed1991

Rapid isolation of monosialogangliosides from bovine brain gangliosides by selective-overload chromatography.

A procedure for rapid isolation of monosialogangliosides from purified bovine brain gangliosides has been developed. It utilizes the selective difference in association between monosialogangliosides and polysialogangliosides for the ion-exchange resin Q-Sepharose. When the ion-exchange column is overloaded with a bovine brain ganglioside mixture in the proper ganglioside to column bed-volume ratio, the polysialogangliosides are selectively retained by the column while the monosialogangliosides emerge with the void volume without the use of salt for elution. With the critical ganglioside to bed-volume ratio (1 g:8.32 ml), and an appropriate column bed-height to column radius ratio of 6.9, monosialogangliosides are reproducibly obtained in high purity with greater than 90% yield. The method has been used at both the analytical and preparative scale. We call this separation technique selective-overload chromatography.

Animals↗

PubMed1990

Developmental expression of HNK-1-reactive antigens in the rat cerebellum and localization of sulfoglucuronyl glycolipids in molecular layer and deep cerebellar nuclei.

Monoclonal antibody HNK-1-reactive carbohydrate epitope is expressed on proteins, proteoglycans, and sulfoglucuronyl glycolipids (SGGLs). The developmental expression of these HNK-1-reactive antigens was studied in rat cerebellum. The expression of sulfoglucuronyl lacto-N-neotetraosylceramide (SGGL-1) was biphasic with an initial maximum at postnatal day one (PD 1), followed by a second rise in the level at PD 20. The level of sulfoglucuronyl lacto-N-norhexaosyl ceramide (SGGL-2) in cerebellum was low until PD 15 and then increased to a plateau at PD 20. The levels of SGGLs increased during postnatal development of the cerebellum, contrary to their diminishing expression in the cerebral cortex. The expression of HNK-1-reactive glycoproteins decreased with development of the rat cerebellum from PD 1. Several HNK-1-reactive glycoproteins with apparent molecular masses between 150 and 325 kDa were visualized between PD 1 and PD 10. However, beyond PD 10, only two HNK-1-reactive bands at 160 and 180 kDa remained. The latter appeared to be neural cell adhesion molecule, N-CAM-180. A diffuse HNK-1-reactive band seen at the top of polyacrylamide electrophoretic gels was due mostly to proteoglycans. This band increased in its reactivity to HNK-1 between PD 15 and PD 25 and then decreased in the adult cerebellum. The lipid antigens were shown by two complementary methodologies to be localized primarily in the molecular layer and deep cerebellar nuclei as opposed to the granular layer and white matter. A fixation procedure which eliminates HNK-1-reactive epitope on glycoproteins and proteoglycans, but does not affect glycolipids, allowed selective immunoreactivity in the molecular layer and deep cerebellar nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

UDP-galactose:globoside galactosyltransferase in murine kidney.

There are increased levels of stage-specific embryonic antigens-3 and -1 (SSEA-3 and SSEA-1) globo-series glycolipids in male versus female DBA/2 and C57BL/6 kidneys, respectively. To determine what enzymatic steps may be responsible for these differences, the activity and properties of UDP-galactose:globoside galactosyltransferase were studied in male and female mouse kidney microsomes. This enzyme participates in the biosynthesis of galactosylgloboside, SSEA-3 glycolipid; the reaction product was identified by high performance thin-layer chromatography (HPTLC) immunostaining. In C57BL/6 mice, the specific activity of the enzyme, in the presence of CHAPS, was 2-fold greater in the male than that in the female. Optimum pH for the enzyme from both sexes was about 5.6, and Mn2+ was essential for maximal activity. Fifty percent of the male and female enzyme activity was lost after preincubating the microsomes for 1 min at 55 degrees C; thereafter, the enzyme from female microsomes had a slower rate of denaturation. The Km for globoside in presence of sodium cholate for both male and female was 0.035 mM, but it was approximately 2-fold greater for the female in presence of CHAPS. The enzyme in male and female microsomes was differentially activated by CHAPS and cholate. The results suggest the presence of an enzyme modulator in these membranes. In DBA/2 mice, the enzyme activity was about 2-fold greater in males than that in the female. The specific activity of the enzyme in the two strains was of a similar magnitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Regulation of cerebroside and sulfatide metabolism in glia cells.

Mouse oligodendroglioma cells, G-26 clone 20 and 24, contain galactosylceramide (cerebroside) and sulfogalactosylceramide (sulfatide) as determined by an HPLC technique. The synthesis of both these lipids was stimulated by 10(-6) M hydrocortisone (cortisol) and also by the removal of serum from the culture medium. Forty-eight hours after the addition of cortisol the incorporation of H235SO4 into sulfatide, the level of sulfatide and the specific activity of the enzyme 3'-phosphoadenosine 5'-phosphosulfate:galactosylceramide sulfotransferase in the cells increased three- to fourfold. The level of cerebroside and the specific activity of UDP-galactose:hydroxyacyl sphingosine galactosyltransferase also increased threefold in the cells on treatment with cortisol. The effect of the hormone on the synthesis of cerebroside preceded the increase in sulfatide synthesis. Experiments with cycloheximide and actinomycin D showed that the effect of the hormone on glycolipid synthesis in these cells were mediated through de novo messenger RNA and protein synthesis. Removal of serum from the culture medium resulted in an approximately twofold enhancement of H235SO4 incorporation into sulfatide within 24 h. The levels of sulfatide and cerebroside and the specific activity of the galactosyltransferase and sulfotransferase also increased significantly after serum removal. However, in contrast to the effect of the steroid, the sulfotransferase activity and the level of sulfatide increased prior to elevations in galactosyltransferase and cerebroside. The effect of serum removal was also found to be mediated by de novo RNA and protein synthesis. The effects of cortisol and serum removal on the synthesis of cerebroside and sulfatide were strictly additive.

Acetates↗

PubMed1978

Regional developmental and fractional studies on myelin and other carbonic anhydrases in rat CNS.

Myelin carbonic anhydrase (CA) was studied with respect to its development in various brain regions and light and heavy myelin (LM and HM). The data indicate that the specific activity of myelin CA has a clear neuraxial distribution, increasing rostrally. The absolute activities and relative distribution are invariant with age; this suggests the CA activity in myelin is independent of stage and degree of myelination. The studies on HM and LM illustrate that HM, like total myelin, has a constant CA activity during development. In contrast, LM although equal to HM at 14 days, progressively decays to an adult level which is one-fourth that of HM. The distribution of CA in myelin was further investigated by comparing the activity in myelin with that present in the SN4 fraction. The activity in this latter fraction, which is derived from heavy myelin, was found to be 2.2 times higher than that in the myelin fraction. Thus, in the adult there exists an almost ten-fold range of activities among the various myelin fractions, SN4 greater than HM greater than LM. This may indicate a segregation of activity towards the outer lamellae. This segregation may have physiological importance in that it is this region of the sheath which should be integrally involved in control of myelin edema. Evidence indicates that there is an interaction of chloride with the enzyme, and maybe the primary ion moved by CA in order to initiate an osmotic flux out of the sheath. The interaction of chloride with the enzyme is dependent on the CA complex with the membrane in that solubilization and partial (60-fold) purification results in a preparation which is refractory to anions.

Aging↗

PubMed1978