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Biomedical subjects

R J Desnick

Publications and source records attributed to R J Desnick.

At least 343 records · Page 19Linked to original sources
PubMed1976

Cardiac valvular anomalies in Fabry disease. Clinical, morphologic, and biochemical studies.

The cardiovascular abnormalities were investigated in two unrelated hemizygous males with Fabry disease who had clinical mitral insufficiency. Postmortem examination of their hearts revelaed anatomic, ultrastructural and biochemical abnormalities resulting from defective activity of the lysosomal enzyme, alpha-galactosidase A. The ultrastructural and biochemical studies demonstrated the marked accumulation of the major glycosphingolipd substrate, trihexosyl ceramide, in the lyosomes of all the cardiac tissues examined; the greatest concentrations were found in the mitral valve and elft ventricular myocardium. Intriguingly, digalactosyl ceramide, a glycosphingolipid substrate not detectable in normal lung, vessel or cardiac tissues, was found increased only in the lung and right heart tissues. Morphologic and chemical examination of cardiac and systemic vessels demonstrated accumulation of trihexosyl ceramide in lysosomes of the vascular endothelium. These studies demonstrate that the progressive accumulation of trihexosyl ceramide in the lysosomes of the cardiac structures and vascular system leads to the multiple cardiovascular manfiestation of Fabry disease.

Ceramides↗
PubMed1976

Mannosidosis: clinical, morphologic, immunologic, and biochemical studies.

The primary metabolic defect in mannosidosis is the deficiency of the acidic alpha-mannosidase A and B activites which results in the lysosomal accumulation of mannose-rich substrates. Out studies demonstrate that the enzymatic diagnosis of suspect homozygotes can be made reliably using plasma, isolated leukocytes, or cultured skin fibroblasts assayed carefully at the appropriate acidic pH. Immunologic studies of a mannosidosis homozygote revealed significant abnormalities of neutrophil function; these included a depressed chemotactic responsiveness and impaired phagocytosis of bacteria. Lymphocyte transformation studies showed a 20% of normal response to purified phytohemagglutinin and a 25% of normal response to concanavalin A. Three major components of alpha-mannosidase activity in normal human liver were resolved by ion exchange chromatography on DEAE-cellulose and electrophoresis on cellulose acetate gels. Electrophoresis of the liver extract from homozygote I with mannosidosis revealed only one band of activity which coelectrophoresed with the alpha-mannosidase C isozyme partially purified from normal liver. However, ion exchange chromatography revealed the presence of residual hepatic acidic activities; the residual A isozyme was eluted in a position corresponding to that of normal alpha-mannosidase A whereas the residual B activity was eluted at a slightly more electronegative position than that of normal B isozyme. The apparent Km values for alpha-mannosidase activity as determined from Linweaver-burk plots were 1.1 mM for normal liver and 0.9 mM for normal leukocytes. In contrast, the residual activity in these sources from homozygote 1 could not be saturated within the solubility range of the substrate; the apparent Km value was estimated at 15.4 mM in liver extracts. Zinc significantly lowered the apparent Km value of the acidic activity in normal liver (from 1.2 to 0.24 mM), whereas this metallic ion had little effect on the values for mannosidosis hepatic activity (from 15.4 to 12.3 mM). Unlike zinc, cobalt had its major effect on the acidic activity in the mannosidosis liver extract, lowering the apparent Km from 15.4 to 3.9 mM, whereas the apparent Km for the normal activity was increased from 1.2 to 1.9 mM. The residual acidic activities were markedly stimulated by zinc in both leukocytes (approximately 300%) and plasma ( approximately 400%) from the homozygotes and to a lesser extent in those sources from normal individuals. In contrast, cobalt enhanced the residual acidic activities in leukocytes (approximately 500%) and plasma (approximately 200%) from the homozygotes while inhibiting these acidic activities (78.9% and 47.7%, respectively) in normal individuals.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1975

I-cell disease (mucolipidosis II):a report on its pathology.

The single most characteristic morphological feature in I-cell disease (ICD) is the accumulation of membrane-bound vacuoles in mesenchymal cells (mainly fibroblasts). No true storage can be documented in those vacuoles. That their contents could have been dissolved during fixation or embedding remains however a possibility. Remnants consisting of a few lamellar arrays and of small amounts of fibrillo-granular material are too scarce for histochemical characterization. In hepatocytes large cells in the white pulp of the spleen and in myocardial fibers, vacuoles with fixative insoluble contents have been discovered; they are nowhere very abundant and their specificity is questionable. Because the affected fibroblastic elements represent a small fraction in any organ, most secondary biochemical abnormalities are expected to be detectable only in purely fibroblastic tissues. Our pathological study contributes to the understanding of some of the clinical features characteristic of ICD and stresses major morphological differences between ICD and the many diseases classified as mucopolysaccharidoses and mucolipidoses.

Acid Phosphatase↗
PubMed1975

Fabry disease: diagnosis by alpha-galactosidase activities in tears.

The enzymatic diagnosis of hemizygotes with Fabry disease and heterozygous carriers was accomplished by the fluorometric determination of alpha-galactosidase activities in tears. Two components of total alpha-galactosidase activity were differentiated by their relative thermostabilities and by chromatography on DEAE-cellulose. The major component, alpha-galactosidase A, was thermolabile and represented approximately 90% of total activity; the remaining activity was thermostable, eluted at a slightly higher salt concentration and was designated alpha-galactosidase B. A single, symmetric pH optimum was observed for total alpha-galactosidase activities from heterozygotes and normal individuals, whereas the total activity from hemizgotes, which was about 10% of that in normal controls, had a broad pH profile, identical to those for alpha-galactosidase B activities from all individuals studied. The apparent Km values for total activities were 3.2, 4.0, and greater than 13 mM for normal individuals, heterozygotes, and hemizygotes, respectively. In contrast, apparent Km values for alpha-galactosidase B activities were greater than 13 mM for all individuals, further suggesteng that the residual activity in hemizygotes with Fabry disease represented the alpha-galactosidase B component. of the potential inhibitors studied, alpha-D-melibiose was found to competitively inhibit total alpha-galactosidase activity (Ki approximately 10 mM). These studies demonstrate that tears provide an easily obtainable source of freshly secreted enzyme for the diagnosis of hemizygotes and heterozygotes with Fabry disease and suggest that tears may be useful for the diagnosis of other inborn errors of metabolism.

Drug Stability↗
PubMed1975

Enzyme therapy. V. In vivo fate of erythrocyte-entrapped beta-glucuronidase in beta-glucuronidase-deficient mice.

The use of erythrocyte entrapment as a strategy to deliver and protect exogenously administered enzymes for replacement therapy in selected genetic diseases has been evaluated in a mammalian model system. The uptake, tissue distribution, intracellular localization, and in vivo lifetime of erythrocyte-entrapped bovine beta-glucuronidase were determined by a selective thermal inactivation assay after intravenous administration into beta-glucuronidase-deficient mice. The exogenous activity was cleared from the circulation with a half-life of about 20 min and was no longer detectable at 2 hr. A concomitant uptake of the injected enzyme was observed in murine tissues, primarily the liver; approximately 30% of the bovine activity was recovered at 30 min and maximal hepatic uptake, 71% of dose, was detected at 2 hr. Hepatic recovery of the bovine activity was observed to decrease in a biphasic pattern to nondetectable levels by 5 days. The recovery of the entrapped activity was characterized by a latency of detection in hepatic tissue up to 13 hr postinjection. At each time point more than 80% (84-100%) of the recovered bovine activity was detected in the lysosomally enriched hepatic subcellular fraction. Maximal recoveries of 10% and 15% of administered dose were observed in splenic and renal tissues, respectively, soon after enzyme administration. In comparison to results obtained after intravenous administration of unentrapped bovine beta-glucuronidase, erythrocyte-entrapped activity was retained fourfold longer in the circulation, fivefold longer in hepatic tissue, and was more efficiently delivered to a variety of tissues.

Animals↗
PubMed1975

Characterization of Hex S, the major residual beta hexosaminidase activity in type O Gm2 gangliosidosis (Sandhoff-Jatzkewitz disease).

Hex S, the major residual beta hexosaminidase activity present in tissues, fluids, and cultured skin fibroblasts of patients with type 0 GM2 gangliosidosis, was isolated and characterized biochemically and immunologically. when appropriate tissue homogenates were tested by electrophoresis on cellulose acetate gels, hex S as well as hex C, the corresponding minor beta hexosaminidase component found in normal visceral tissues, migrated with greater anodic mobilities than hex A. However, a small but reproducible electrophoretic difference was observed between partially purified hex S and hex C components. Hex S and hex C had slightly higher apparent molecular weights than those of hex A or hex G; no major differences were found between hex S and hex A in thermostability, pH optimum, or kinetic properties. Hex S, like hex C from placenta, reacted with an antiserum directed towards the unique antigenic determinants alpha of hex A, indicating that hex S, hex C, and hex A share a common antigenic determinant. No reactivity of hex S was detected with an antiserum directed toward the common antigenic determinant beta of hex A and hex B. These results suggest that further biochemical and immunologic characterization of hex S and elucidation of its relationships with hex A, hex B, and hex C may significantly contribute to the understanding of the molecular defects in the GM2 gangliosidoses.

Brain Chemistry↗