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Biomedical subjects

S S Raghavan

Publications and source records attributed to S S Raghavan.

At least 37 records · Page 2Linked to original sources
PubMed1986

Two abnormalities of hexosaminidase A in clinically normal individuals.

Two abnormalities of beta-hexosaminidase A (HEX A) activity are described. One, found in two unrelated Jewish children, was characterized by the complete absence of HEX A activity in serum, but low levels of activity in leukocytes and fibroblasts using artificial substrate. The other, found in a non-Jewish man, was characterized by uniformly low levels of HEX A activity in leukocytes, fibroblasts, and serum against artificial substrate. In all cases, the pH optimum of HEX A was normal, there was no increased lability at 37 degrees C, and no inhibitor was detected to account for the deficiency of activity. Cultured fibroblasts of these individuals were capable of synthesizing and processing alpha- and beta-subunits of HEX A and capable of cleaving GM2 ganglioside. The patients, ranging in age from 6 to 30 years, are clinically normal. They are probably genetic compounds carrying the classical Tay-Sachs gene and a differently mutated allele that imparts the anomalous phenotypic features observed.

Adult↗
PubMed1985

Neurovisceral and skeletal GM1-gangliosidosis in dogs with beta-galactosidase deficiency.

Beta-galactosidase-deficient siblings in two litters of English springer spaniel puppies showed a progressive neurological impairment, dwarfism, orbital hypertelorism, and dysostosis multiplex. An excess of GM1-ganglioside was found in the brain. Three abnormal oligosaccharides were present in samples of urine, brain, liver, and cartilage. Light microscopy of selected tissue specimens revealed cytoplasmic vacuoles in neurons, circulating blood cells, macrophages, and chondrocytes. Ultrastructural studies demonstrated that these membrane-bound vacuoles were of two types--one containing lamellated membranes and the other, finely granular material. These clinical and pathological findings are similar to those observed in human patients affected by the infantile form of GM1-gangliosidosis.

Animals↗
PubMed1985

GM2-ganglioside metabolism in hexosaminidase A deficiency states: determination in situ using labeled GM2 added to fibroblast cultures.

To clarify the relationship between hexosaminidase A (HEX A) activity and GM2-ganglioside hydrolysis in atypical clinical situations of HEX A deficiency, we have developed a simple method to assess GM2-ganglioside metabolism in cultured fibroblasts utilizing GM2 labeled with tritium in the sphingosine portion of the molecule. The radioactive lipid is added to the media of cultured skin fibroblasts, and after 10 days the cells are thoroughly washed, then harvested, and their lipid composition analyzed by HPLC. The degree of hydrolysis of the ingested GM2 is determined by comparing the amount of radioactive counts recovered in undegraded substrate with total cellular radioactivity. A deficiency in GM2-ganglioside hydrolysis was demonstrated in seven HEX A-deficient adults with neurological signs and in two healthy-appearing adolescents with older affected siblings. In each case, an analysis of endogenous monosialoganglioside composition revealed an increase in GM2-ganglioside, confirming the presence of a block in the metabolism of GM2. No defect in GM2-catabolism was found in four other healthy individuals with HEX A deficiency. This method of assay is especially helpful in the evaluation of atypical cases of HEX A deficiency for the definitive diagnosis of GM2-gangliosidosis.

Adult↗
PubMed1981

Leukocyte sulfatidase for the reliable diagnosis of metachromatic leukodystrophy.

A simple assay technique for the determination of sulfatidase activity in leukocytes has been developed for the reliable diagnosis of metachromatic leukodystrophy (MLD). Sulfatide is tritiated in sphingosine and fatty acid by reduction with [3H]sodium borohydride in alkali in the presence of palladium chloride. This labeled natural substrate for aryl sulfatase A (AsA) is hydrolyzed by normal human leukocytes in 25 mM-acetate buffer, pH 5.0, in the presence of 0.3% sodium taurodeoxycholate. The enzyme activity is greatly improved after dialysis, exhibiting better linearity with protein concentration. It is stimulated maximally by 5 mM-MnCl2 with an apparent Km of 0.17 mM for the substrate. Patients with MLD exhibited virtually no detectable sulfatidase activity although they had residual AsA activity that was measured with the synthetic substrate, p-nitrocatechol sulfate (NCS). Potential heterozygotes could be identified by the sulfatidase assay in instances where the NCS assay for AsA was inconclusive. Several individuals with levels of AsA activity characteristic of MLD, including a few healthy carriers and certain patients with unknown neurological diseases, were shown not to have MLD by the presence of measurable levels of sulfatidase in their leukocytes.

Arylsulfatases↗
PubMed1980

Leukocyte beta-glucosidase in homozygotes and heterozygotes for Gaucher disease.

Human leukocytes contain at least two isozymes of 4-methylumbelliferyl-beta-glucosidase acting optimally at pH 4.0 and 4.8; in Gaucher disease, only the former is deficient. Brief exposure of the leukocyte homogenate to pH 4.0 at room temperature results in irreversible inactivation of the pH 4.8 activity, while the activity at pH 4.0 remains unaffected. The more acidic isozyme is stimulated four- to fivefold by 0.2% sodium taurodeoxycholate (TDC) with a shift in the pH optimum to 5.0. The less acidic isozyme is completely suppressed in the presence of this detergent. Both leukocyte isozymes appear to be membrane-bound since gel filtration of Sephadex G-200 produces only one peak of activity located at the void volume, unlike in liver and kidney where a second peak also can be demonstrated. Heat inactivation analysis indicated that in controls, assayed in the absence of detergent, pH 4.0 activity is more thermostable than pH 4.8 activity. However, in Gaucher disease, the residual beta-glucosidase at pH 4.0 is just as thermolabile as the unaffected pH 4.8 activity. Heat inactivation of the enzyme in the presence of TDC resulted in rapid loss of activity, suggesting a direct effect of the bile salt on the configuration of the enzyme decreasing its thermal stability. In the absence of detergent, acid beta-glucosidase shows two K(m)'s, one at 3.2 mM and another at 0.9 mM. In the presence of detergent, only the higher K(m) at 3.3 mM is obtained. In patients with Gaucher disease and in obligate carriers, the K(m) remains essentially unaffected while the V(max) shows the expected deficiency.A reliable and reproducible selective assay technique has been developed for the diagnosis of Gaucher disease homozygotes and obligate heterozygotes and for the carrier screening of individuals at risk for this inherited disorder. The efficacy of this technique has been demonstrated by studying the activity in 42 controls, 26 patients, 32 obligate heterozygotes, and 23 healthy relatives of patients with Gaucher disease.

Adult↗
PubMed1979

Abnormal copper metabolism in Menke's steely-hair syndrome.

Copper (Cu) metabolism was selectively studied in seven infants with Menke's steely-hair syndrome (SHS). A daily oral regimen of CuSO4 (584 microgram Cu/kg) and L-histidine (100 mg/kg) in three infants produced an increase in serum Cu concentrations ranging from 33-95% of normal, but without the formation of ceruloplasmin. Cohn serum protein fractionation after oral Cu/L-histidine loading showed a disproportionate accumulation of Cu in the albumin fraction (V). The electron spin resonance spectrum of fraction V showed a heightened signal for the SHS patients, suggesting that an increased concentration of a radical Cu species is present after oral loading. The Sephadex G-150 chromatographic profile of serum fraction V in SHS did not differ significantly from controls. These results suggest that, in SHS, Cu absorbed in the presence of L-histidine is in an abnormal complex involving albumin, which does not allow for holoceruloplasmin biosynthesis. Cu and ceruloplasmin concentrations in the cord blood specimen of an infant who went on to develop SHS were normal, a finding which may account for the transient period of seemingly normal development after birth in SHS patients. An almost 6-fold difference in mean Cu concentration was observed in SHS fibroblasts compared to controls. Fibroblast Cu concentration was elevated in one to two possible maternal heterozygotes, a finding which may permit diagnosis of the carrier state for some SHS heterozygotes.

Blood Proteins↗
PubMed1977

The beta-glucosidases of porcine kidney.

Some of the properties of a partially purified particle bound and soluble beta-glucosidase (EC 3.2.1.21) from pig kidney were compared. The soluble beta-glucosidase (1) hydrolyzed 4-methylumbelliferyl-beta-D-glucoside (4-MU-beta-D-glucoside) 17 alpha-estradiol 3beta-glucoside. 17 alpha-estradiol 17beta-glucoside, and salicin, but not glucosylceramide, (2) possessed a broad pH optimum (5.5-7.0), (3) had an isoelectric point of 4.9, and (4) was inhibited by Triton X-100. Several compounds were found to be competitive inhibitors of its hydrolytic activity, gluconolactam and estrone beta-glucoside being the most effective. In contrast, a particulate beta-glucodidase purified from the same tissue (1) had an acidic pH optimum (5.0), (2) was stimulated by sodium taurocholate and 'Gaucher's factor' for the hydrolysis of both 4-MU-beta-glucosidase and glucosylceramide, and (3) was capable of catalyzing a transglucosylation reaction employing 4-MU-beta-D-glucoside or glucosylceramide as the glucosyl donor, and [14C]ceramide as acceptor.

Animals↗
PubMed1975

Hydrolytic and transglucosylation activities of a purified calf spleen beta-glucosidase.

Certain properties of the transglucosylitic activity and the hydrolytic activity of a purified calf spleen beta-glucosidase (beta-D-glucoside glucohydrolase EC 3.2.1.21) were investigated. There was a stimulation of both activities by sodium taurocholate and "Gaucher's factor". The K-m values for 4-methylumbelliferyl-beta-D-glucoside and glucosylceramide as donors in the transglucosylation reaction were 2 mM and 0.075 mM, respectively. The K-m for ceramide as acceptor was 0.149 mM with both of these compounds. The ability of several glucoside to act as donors was examined. The capacity to catalyze this "transglucosylation" reaction is greatly diminished in spleen tissue samples from Gaucher's patients. The enzyme possesses the capacity to hyrolyze 4-methylumbellifery-beta-D-glucoside, p-nitrophenyl-beta-D-glucoside, glucosylsphingosine, glucosylceramide and deoxycorticosterol-beta-D-glucoside. It is postulated that a single enzyme protein may be responsible for both the hydrolytic and the transglucosylitic activities.

Animals↗
PubMed1974

Isolation and characterization of glucosylsphingosine from Gaucher's spleen.

Glucosylsphingosine has been isolated for the first time as a natural constituent from Gaucher's spleen. On thin-layer chromatography, it migrates with authentic glucosylsphingosine, yielding a positive color reaction with ninhydrin for the amino group and with alpha-naphthol-sulfuric acid for the carbohydrate residue. N-Acylation with palmitic acid gave rise to glucosylceramide, which was cleaved by purified glucosylceramide: beta-glucosidase to ceramide. Gas-liquid chromatography of the trimethylsilyl derivative showed a retention time similar to authentic glucosylsphingosine. Gas-liquid chromatographic analysis of the trimethylsilyl derivatives after methanolysis revealed the presence of only glucose and C(18)-sphingosine. Mass spectral data further supported the structural identity with glucosylsphingosine.

Acylation↗