Search PubMed⌕ Search

Biomedical subjects

P V Donnelly

Publications and source records attributed to P V Donnelly.

At least 19 recordsLinked to original sources
PubMed1995

Insulin resistance is mediated by a proteolytic fragment of the insulin receptor.

Insulin resistance is a common clinical feature of obesity and non-insulin-dependent diabetes mellitus, and is characterized by elevated serum levels of glucose, insulin, and lipids. The mechanism by which insulin resistance is acquired is unknown. We have previously demonstrated that upon chronic treatment of fibroblasts with insulin, conditions that mimic the hyperinsulinemia associated with insulin resistance, the membrane-associated insulin receptor beta subunit is proteolytically cleaved, resulting in the generation of a cytosolic fragment of the beta subunit, beta', and that the generation of beta' is inhibited by the thiol protease inhibitor E64 (Knutson, V. P. (1991) J. Biol. Chem. 266, 15656-15662). In this report, we demonstrate that in 3T3-L1 adipocytes: 1) cytosolic beta' is generated by chronic insulin administration to the cells, and that E64 inhibits the production of beta'; 2) chronic administration of insulin to the adipocytes leads to an insulin-resistant state, as measured by lipogenesis and glycogen synthesis, and E64 totally prevents the generation of this insulin-induced cellular insulin resistance; 3) E64 has no effect on the insulin-induced down-regulation of insulin receptor substrate-1, and therefore insulin resistance is not mediated by the down-regulation of insulin receptor substrate-1; 4) under in vitro conditions, partially purified beta' stoichiometrically inhibits the insulin-induced autophosphorylation of the insulin receptor beta subunit; and 5) administration of E64 to obese Zucker fatty rats improves the insulin resistance of the rats compared to saline-treated animals. These data indicate that beta' is a mediator of insulin resistance, and the mechanism of action of beta' is the inhibition of the insulin-induced autophosphorylation of the beta subunit of the insulin receptor.

3T3 Cells↗
PubMed1984

The urinary excretion of heparan sulfate by juvenile- and adult-onset diabetic patients.

The daily urinary excretions of total polymeric glycosaminoglycans and of polymeric heparan sulfate have been measured in the urine of juvenile-onset and adult-onset diabetics of both sexes and in those of normal controls. The results indicate that diabetic patients excrete more polymeric heparan sulfate than their controls, either in an absolute amount or as a percentage of the total glycosaminoglycans excreted. These results suggest that in the course of diabetes there is an increased degradation of heparan sulfate to large oligosaccharide fragments. These are excreted before being completely degraded to monosaccharides and inorganic sulfate.

Adolescent↗
PubMed1984

Synthesis and sulfation of glycosaminoglycans in fibroblasts from a patient with Lowe's syndrome.

Glycosaminoglycans of cultured normal skin fibroblasts and fibroblasts of a patient with Lowe's syndrome were labelled for 72 h with either [14C]-glucosamine or with 35SO4. For each culture, the incorporation was measured in total glycosaminoglycans per culture and in the glycosaminoglycans isolated from the intracellular, pericellular and extracellular pools. The synthesis of the sulfated glycosaminoglycans in the three pools and the total 35SO4 incorporation in the glycosaminoglycans of the two types of cultures were strictly comparable. However, Lowe's intracellular glycosaminoglycans were less sulfated than the corresponding normal ones. Undersulfated glycosaminoglycans were present in the pericellular pool of Lowe's cells, while hypersulfated ones were present in their extracellular pool. Degradation of the different pools with chondroitinases indicated that hyposulfated chondroitin 4- and 6-sulfates are present on the cell surface of Lowe's cells, where an increased amount of normally sulfated heparan sulfate may be demonstrated. This abnormal distribution of pericellular glycosaminoglycans in Lowe's cells has been described already. However, the demonstration that the total incorporation of 35SO4 is normal in Lowe's cells does not support the possibility that this abnormal distribution is the consequence of excessive hydrolysis of the phosphosulfate bond of adenosine 3'-phosphate 5'-phosphosulfate.

Carbon Radioisotopes↗
PubMed1983

Sulfated glycosaminoglycans synthesized by fibroblast, smooth muscle and endothelium-like cells grown in culture.

Monolayer cultures of fibroblast, smooth muscle and endothelium-like cells incorporated 35SO2-(4) into glycosaminoglycans of the extracellular, pericellular and intracellular compartments. These glycosaminoglycans have been identified on the basis of electrophoretic mobility, enzymatic degradation with specific mucopolysaccharidases and by the type of degradation products formed. The sulfated glycosaminoglycans from the extracellular pool of the three cell types show a similar composition, while the intracellular and pericellular pools of the three cells have a different glycosaminoglycans composition. They differ in the relative proportion of heparitin sulfate and chondroitin sulfate and in the structure of isomeric chondroitin sulfate.

Animals↗
PubMed1981

Cleavage of the (1 goes to 3)-2-acetamido-2-deoxy-beta-D-glucopyranosyl linkage present in keratan sulfate. The A and B isoenzymes of human liver hexosaminidase (EC 3.2.1.30).

The disaccharide 2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 goes to 3)-D-[1-3H]-galactitol, prepared from keratan sulfate, was rapidly hydrolyzed by the A and B isoenzymes of normal human liver hexosaminidase (EC 3.2.1.30), and by the B isoenzyme prepared from the liver of a patient who had died of Tay-Sachs disease. The disaccharide substrate was also hydrolyzed by extracts of normal, cultured-skin fibroblasts, and fibroblasts of patients with Tay-Sachs disease, whereas it was not hydrolyzed by fibroblast extracts of patients with Sandhoff disease. Thus, effective degradation of keratan sulfate, secondary to a defect of the beta subunits present in the A and B isoenzymes of hexosaminidase, may contribute to the appearance of skeletal lesions in patients affected by Sandhoff disease.

Acetylglucosaminidase↗
PubMed1981

Collagen treated with (+)-catechin becomes resistant to the action of mammalian collagenase.

Treatment of radioactively labeled guinea-pig skin soluble collagen or calf skin collagen with the flavonoid (+)-catechin makes the collagen resistant to the action of mammalian collagenase but not to the action of bacterial collagenase. Complete resistance to the action of the mammalian enzyme may be achieved by incubating 0.6 mg of collagen (dry weight) with 0.1 mM (+)-catechin, followed by dialysis to remove the unbound flavonoid. Since incubation of the mammalian enzyme with (+)-catechin does not inhibit its activity, it is postulated that (+)-catechin binds tightly to collagen and modifies its structure sufficiently to make it resistant to enzyme degradation.

Animals↗
PubMed1978

The interaction of human plasma glycosaminoglycans with plasma lipoproteins. II. Hemagglutination studies.

Formalinized, tannic acid-treated sheep erythrocytes coated with low density lipoproteins (LSL) or apoprotein B (apo-B) are are agglutinated by anti-apo-B immunserum. Those coated with high density lipoproteins (HDL) or apoprotein A-I(apo-A-I) are agglutinated by anti-apo-A-I immunserum. These coated formocells have been used to study the interactions of lipoproteins and apoproteins with plasma glycosaminoglycans (GAG). The sulfate-rich species of plasma GAG agglutinates cells coated with LDL, HDL, apo-B, and apo-A-I at ionic concentrations above 0.15 M. The less-sulfated species of plasma GAG does not agglutinate the coated cells but inhibits the agglutination caused by the sulfate-rich species. Treatment of the sulfate-rich GAG with papain causes a reduction in molecular weight by one-half and also causes a loss of its agglutinating activity. These results suggest that the sulfate-rich plasma GAG, consisting of two glycan chains linked to a peptide backbone, cause agglutination by binding to two or more formocells. In contrast, the less-sulfated plasma GAG, consisting of single, short glycan chains, are incapable of causing agglutination but may prevent it by covering specific binding sites present on the coated cells.

Apoproteins↗
PubMed1976

Abnormally soluble collagen produced in fibroblasts cultures.

Abnormally soluble collagen is synthesized in vitro not only by skin fibroblasts of Marfan patients but also by those of patients with Ehlers-Danlos type V and cutis laxa. The excessive solubility of collagen is corrected by the addition to the culture medium of a synthetic flavonoid, (+)- catechin.

Benzopyrans↗
PubMed1976

The effect of (+) --cyanidanol on lysosomal enzymes of I-cell fibroblasts.

(+)--Cyanidanol, a water-soluble flavonoid, when added to cultured skin fibroblasts of a patient with I-cell disease raised the intracellular concentration of beta-galactosidase but did not affect the distribution of arylsulfatase. A, alpha-mannosidase or beta-glucuronidase. The elevated accumulation of 35SO4 by I-cell, Hunter and Maroteaux-Lamy fibroblasts was decreased by the addition of (+)--cyanidanol to the culture medium, but the degradation of previously labeled, intracellular glycosaminoglycans was not. It is concluded that (+)--cyanidanol does not produce a biochemical correction of the enzymic abnormalities existing in I-cell fibroblasts.

Benzopyrans↗
PubMed1975

Lysyl oxidase deficiency in Ehlers-Danlos syndrome type V.

Two maternal cousins affected by the X-linked form of Ehlers-Danlos syndrome have been observed. Both had congenital heart disease, "floppy valve syndrome", hernias, short stature, stretchable skin and moderate joint hypermobility. Both excreted normal amounts of urinary glycosaminoglycans, almost entirely represented by dermatan sulfate, whose degradation appeared to be inadequate. They also excreted large amounts of hydroxylysine glycosides and L-valyl-proline, considered to be products of degradation of collagen and elastin, respectively. Cultured skin fibroblasts of the propositus synthesized excessively soluble collagen and had a low lysyl oxidase activity. These findings suggest that the increased degradation of structural proteins may be secondary to the defective cross-linking processes caused by the enzymic defect. Addition of (+) catechin, a flavonoid, to the propositus's cultured fibroblasts decreased the abnormal solubility of their collagen.

Amino Acid Oxidoreductases↗
PubMed1975

Reliability of the Booth-Nadler technique for the detection of Hunter heterozygotes.

Skin fibroblasts from three obligated and one potential heterozygotes for the Hunter gene displayed abnormal metabolism of glycosaminoglycans four to six weeks after rapid freezing in liquid nitrogen. The technique seems to be useful for the identification of Hunter carriers, especially when the degradation of 35SO4-labeled, intracellular glycosaminoglycans, rather than the uptake of 35SO4, is measured.

Adult↗