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Biomedical subjects

N G Beratis

Publications and source records attributed to N G Beratis.

At least 73 records · Page 4Linked to original sources
PubMed1979

Cystathionase deficiency: the effect of cofactor on the stability of normal and abnormal enzyme from lymphoid cell lines.

Heating at 70 degrees C with and without added pyridoxal phosphate (PLP) had strikingly different effects on cystathionase protein from normal long-term lymphoid cell lines and on the enzymes from cells derived from patients with vitamin-B6-responsive cystathioninuria. PLP added to extracts of normal cells afforded complete protection against heat inactivation, whereas inactivation of the cystathionase protein in extracts obtained from two cystathioninuric lines was greater in the presence of PLP than in its absence.

Cells, Cultured↗
PubMed1978

Alpha-L-fucosidase in cultured bone marrow fibroblasts from fucosidosis patients.

Bone marrow fibroblasts were cultured from two patients with fucosidosis type 2, six control subjects, and three patients with other lysosomal disorders. Optimal conditions for measuring alpha-L-fucosidase activity in lysates of these cells with the fluorogenic substrate 4-methylumbelliferyl-alpha-L-fucoside were established. The pH profile of normal bone marrow fibroblasts showed three peaks and a shoulder of enzymatic activity, with maximum activity at pH 4.75. In cells derived from fucosidosis patients two peaks of apparent alpha-L-fucosidase activity were obtained; the pH optimum was 4.5. alpha-L-Fucosidase activity (mean +/- SD) in the fucosidosis and control bone marrow fibroblasts was 2.5 and 312.4 +/- 10.9 nmoles 4-methylumbelliferone per milligram protein per hour, respectively. A reduction in the apparent specific enzymatic activity in the fucosidosis cells was observed by using increasing concentrations of cellular protein in the assay system. Mixing experiments between normal and fucosidosis cells gave the expected activities. These findings indicate that cultured bone marrow fibroblasts can be used for the diagnosis and study of fucosidosis.

Bone Marrow↗
PubMed1978

Characterization of the molecular defect in infantile and adult acid alpha-glucosidase deficiency fibroblasts.

Different clinical expressions of acid alpha-glucosidase deficiency have been described. The present study was undertaken to investigate the basic metabolic defect in the infantile and adult forms of the disease. Acid alpha-glucosidase (EC 3.2.1.20) was purified from normal and from adult acid alpha-glucosidase deficiency fibroblasts. The pH optimum; Michaelis constant; electrophoretic mobility in starch; thermal denaturation at pH 4.0 and 7.0; and inhibition by turanose, alpha-methylglucoside and trehalose were the same in purified enzyme from normal and mutant cells. Placental acid alpha-glucosidase was purified to, or near, homogeneity. Monospecific antibodies raised against the enzyme in each of three enzyme peaks obtained from the last purification step were found to cross-react with the enzyme of all three peaks, and with purified, normal fibroblast enzyme. Cross-reacting material (CRM) also was identified in fibroblast lysates from normal subjects and from both forms of acid alpha-glucosidase deficiency. The amount of CRM in the adult form appeared to be significantly less than in normal cells or cells from the infantile form. Enzyme activity was demonstrated in the immune complexes of the normal and adult acid alpha-glucosidase deficiency fibroblasts, but not of the infantile form. Competition for antibody binding sites was observed between normal and both types of mutant enzymes. The findings indicate that this case of infantile acid alpha-glucosidase deficiency is the result of a structural gene mutation which causes the synthesis of a catalytically inactive (CRM-positive) enzyme protein. It appears that in the adult form, the mutation causes a reduction in the amount of the enzyme protein present in the cells.

Adult↗
PubMed1977

Cell-specific differences in membrane beta-glucosidase from normal and Gaucher cells.

Two isozymes of membrane-bound beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) with activity towards 4-methylumbelliferyl-beta-D-glucopyranoside have been identified in human cells. One of these isozymes was found to have a pH optimum of 5.0, a Km of 0.4 mM and to be rapidly inactivated at pH 4.0 ("acid-labile"). The second isozyme had a pH optimum of 4.5, a Km of 0.8 mM and was stable at pH 4.0 ("acid-stable"). Cultured long-term lymphoid lines and peripheral blood leukocytes contained both isozymes while cultured skin fibroblasts contained only the "acid-stable" form in detectable amounts. The specific activity of the "acid-stable" isozyme was severely reduced in cultured skin fibroblasts, cultured long-term lines and peripheral leukocytes from patients with Gaucher's disease. The specific activity of the "acid-labile" enzyme in the latter two cell types was apparently unaffected. The beta-glucosidase activity in all three cell types examined was predominantly particulate but the enzyme could be solubilized with low concentrations of Triton X-100. The solubilized enzyme required sodium taurocholate (0.2%) for maximum activity. Solubilized beta-glucosidase did not exhibit the cell-specific differences in pH optimum and Km shown by the membrane-bound enzyme.

Cell Membrane↗
PubMed1977

alpha-L-fucosidase in cultured skin fibroblasts from normal subjects and fucosidosis patients.

alpha-L-Fucosidase (EC 3.2.1.51) activity was studied in cultured skin fibroblasts obtained from 23 members of a family in which two cases of fucosidosis type 2 had occurred and in the fibroblasts of a patient with fucosidosis type 1. Both the 4-methylumbelliferyl glycoside and the p-nitrophenyl derivative were used as substrates. pH activity profiles showed two major peaks of activity. With the fluorogenic substrate pH optimum was at 4.5, whereas with the colorigenic substrate maximum activity was at pH 5.7. No activity was found in the fibroblasts of the three patients with the colorimetric assay. With the fluorometric assay the mean activity in the two patients with fucosidosis type 2 was 4.1 and 2.8 (range 1.3-9.9); activity in the patient with fucosidosis type 1 was 4.6 nmol 4-methylumbelliferone/mg protein/hr (range 1.0-8.6). The specific activity in the lysates of the patients' fibroblasts decreased as the amount of cellular protein used per assay increased. Fucosidosis fibroblasts cultured for 3 and 5 days in medium without fetal calf serum showed almost the same levels of apparent residual activity as fibroblasts cultured in medium containing fetal calf serum. Maximum activity in the deficient fibroblasts was at pH 4.5-4.75. Mixing experiments between lysates of both of fucosidosis and a normal fibroblast strain showed the expected enzymatic activities. The mean alpha-fucosidase activity in four heterozygotes for fucosidosis was 37.6 (range 24.1-48.7) and 30.3 (range 19.0-44.1) nmol final product split/mg protein/hr with the fluorogenic and the colorigenic substrate, respectively. In 12 normal fibroblast strains the mean activity +/- SD was 85.3 +/- 24.4 (range 50.8-129.3) and 67.6 +/- 21.1 (range 31.1-118.3). However, in four family members in which the alpha-L-fucosidase phenotype (by isoelectric focusing) was type 2-1, and who should therefore be carrying two normal alleles, the activity was within the heterozygote range. This indicates that occasional overlap between normal subjects and carriers may be present in cultured skin fibroblasts. Increased specific activity of alpha-L-fucosidase at pH 3.2-4.0 was observed after incubation of cell lysates with neuraminidase. The alpha-L-fucosidase activity did not show any increase after fusion between fucosidosis fibroblasts type 1 and 2.

Biopsy↗
PubMed1976

Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and the esterification of cholesterol in human long term lymphoid cell lines.

The regulation of the rate-controlling enzyme in cholesterol biosynthesis and of the incorporation of [14C]oleate into cholesterol esters were studied in established lymphoid cell lines from normal subjects and compared with that of eight patients with genetic abnormalities of lipid metabolism. The activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-controlling enzyme in cholesterol biosynthesis, increases in lymphoid cell lines derived from normal subjects after the culture medium is changed to a lipid deficient medium and reaches peak activity after 48 hr. The addition of whole serum and of low density lipoproteins to cell lines derived from normal subjects suppressed 3-hydroxy-3-methylglutaryl coenzyme A reductase activity by 50%, but failed (almost completely) to suppress the activity in the lymphoid cell lines derived from two patients with homozygous familial hypercholesterolemia. When 7-ketocholesterol was added, the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase was markedly suppressed in both normal and abnormal lymphoid cell lines. Lymphoid cell lines derived from patients presumably heterozygous for familial hypercholesterolemia were difficult to distinguish from normal cells in these studies. The incorporation of [14C]oleate into the fatty acid fraction of cholesteryl esters was stimulated by the addition of the low density lipoproteins to the culture media of the lymphoid cell lines derived from the normal human subjects. The lymphoid cell lines derived from the patients with homozygous familial hypercholesterolemia showed no increase in [14C]oleate incorporation into cholesteryl esters even when a fourfold amount of low density lipoprotein was added to the media; a modest increase in [14C]oleate incorporation was observed in lymphoid cell lines from patients with heterozygous familial hypercholesterolemia. The results of these studies in lymphocyte cell lines are compared with the findings in cultured human fibroblasts obtained from normal subjects and from patients with homozygous familial hypercholesterolemia. Studies of the regulation of cholesterol biosynthesis in the apparently permanent lymphoid cell line maintained in suspension culture offer certain advantages over cultured skin fibroblasts, and, in addition, provide a second tissue for the study of genetic abnormalities from the same patient.

Abetalipoproteinemia↗
PubMed1976

alpha-L-Fucosidase in normal and deficient individuals.

Deficiency of the enzyme alpha-L-fucosidase has been demonstrated in peripheral leukocytes, cultured skin fibroblasts and long-term lymphoid lines from two sibs with fucosidosis 2. Reliable identification of heterozygotes for this disease was accomplished by enzyme assay of mononuclear cells isolated from peripheral blood. Isoelectric focusing of alpha-L-fucosidase isozymes in leukocyte extracts from normal individuals revealed a common polymorphism which was shown to result from two autosomal alleles at a single, autosomal locus. Evidence was obtained for a third, "silent" allele segregating in the family of the two affected children. It is probable that the disease fucosidosis type 2 results from homozygosity for this "silent" allele. Preliminary experiments have shown that cultured skin fibroblasts from deficient individuals can incorporate and retain purified alpha-L-fucosidase added to the culture medium.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1976

Alkaline phosphatase activity in cultured skin fibroblasts from fibrodysplasia ossificans progressiva.

Alkaline phosphatase activity in four strains of cultured skin fibroblasts obtained from a patient with fibrodysplasia ossificans progressiva was at the low normal range. The enzyme activity in normal fibroblasts significantly increased at late confluency. It appears that the high levels of alkaline phosphatase activity reported in biopsies of lesions are not genetically determined but are secondary events of local tissue reaction.

Adolescent↗
PubMed1976

Fucosidosis type 2.

Two siblings, 9 and 4 1/2 years old, had alpha-L-fucosidase deficiency, angiokeratoma, progressive psychomotor retardation, neurologic signs, coarse facila features, and dysostosis multiplex. It appears that genetic heterogeneity is present in fucosidosis; there are at least two types. In type 1, patients have no vascular lesions, but have rapid psychomotor regression, severe and rapidly progressing neurologic signs, elevated sodium and chloride excretion in the sweat, and fatal outcome before the sixth year. In type 2, patients have angiokeratoma, milder psychomotor retardation and neurologic signs, longer survival, and normal salinity in the sweat. Quantitative studies on erythrocytes and in saliva disclosed severely increased expressions of Lea and Leb. Biopsies of skin and gingiva showed alterations as seen in angiokeratoma. There was also evidence of lysosomal storage in vascular endothelium, eccrine sweat gland epithelium, and fibroblasts of the skin.

Adult↗
PubMed1975

Vitamin B6-responsive and -unresponsive cystathioninuria: two variant molecular forms.

Cystathionase activity in a lymphoid cell line extracts from a vitamin B6-responsive patient with cystathioninuria was increased strikingly by pyridoxal phosphate. Immunodiffusion with antiserum to human hepatic cystathionase showed identity between this cystathionase protein and cystathionase from an extract of normal lymphoid cells. Neither an increase in cystathionase activity nor immunochemical identity was found using extract of cells from a B6-unresponsive patient.

Amino Acid Metabolism, Inborn Errors↗
PubMed1975

Fucosidosis: detection of the carrier state in peripheral blood leukocytes.

We have utilized the fluorogenic substrate 4-methylumbelliferyl-alpha-L-fucoside to measure the activity of alpha-L-fucosidase in white blood cells and serum. We have compared the findings with those using the P-nitrophenyl derivative. pH activity curves showed two major peaks of activity in leukocyte lysates, with different specificities to these substrates. alpha-L-Fucosidase activity was determined in peripheral leukocytes. Isolated mononuclear cells (mainly lymphocytes), and granulocytes in 21 members of a family in which fucosidosis had occurred and in normal control subjects. The activity in the leukocytes, lymphocytes, and granulocytes of the normal subjects was 300.7 +/- 79.8, 190.1 +/- 43.9, and 281.9 +/- 73.1 nmoles 4-methylumbelliferone/mg protein/hour with the fluorogenic substrate, and 150.0 +/- 31.8, 154.8 +/- 21.0, and 148.3 +/- 48.3 nmoles p-nitrophenol/mg protein/hour with the colorigenic substrate, respectively. No activity was detected in the patients' cells with the colorigenic substrate, whereas with the fluorogenic substrate the apparent activity varied from 0.5 to 1.1. In the lymphocytes of both of the patients' parents, two grandparents, and six other potential carriers, the activity fell between the normal and patients' values. Great variation in alpha-L-fucosidase activity, with broad overlap between normal subjects and heterozygotes, was observed in serum and plasma. Our findings indicate that detection of carriers for fucosidosis is possible by direct fucosidase determinations in isolated mononuclear cells.

Carbohydrate Metabolism, Inborn Errors↗