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H Witas

Publications and source records attributed to H Witas.

At least 19 recordsLinked to original sources
PubMed1996

The effects of in vivo and in vitro non-enzymatic glycosylation and glycoxidation on physico-chemical properties of haemoglobin in control and diabetic patients.

The erythrocyte deformability, which is related to erythrocyte internal viscosity, was suggested to depend upon the physico-chemical properties of haemoglobin. In the present study we employed ESR spectroscopy on order to explore further the extent to which the in vivo or in vitro glycation and/or glycoxidation might affect haemoglobin structure on conformation. We revealed that under both in vivo and in vitro conditions the attachment of glucose induced a mobilization of thiol groups in the selected domains of haemoglobin molecules ( the increased h+1/h0 parameter of maleimide spin label, MSL; 0.277 +/- 0.021 in diabetics vs 0.338 +/- 0.017 in controls, n = 12, P < 0.0001). The relative rotational correlation time (tau c) of two spin labels, TEMPONE and TEMPAMINE, respectively, in erythrocyte insides (5.22 +/- 0.42 in diabetics, n = 21 vs 4.79 +/- 0.38, n = 16 in controls, P < 0.005) and in the solutions of in vitro glycated haemoglobin, were increased. Neither oxidation nor crosslinking of thiol groups was evidenced in glycated and/or oxidized haemoglobin. In addition, erythrocyte deformability was found to be reduced in type 2 diabetic patients (6.71 +/- 1.08, n = 28 vs 7.31 +/- 0.96, n = 21, P < 0.015). In conclusion, these observations suggest that: the attachment of glucose to haemoglobin might have decreased the mobility of the Lys-adjacent Cys residues, thus leading to the increased h+1/h0 parameter of MSL. Such structural changes in haemoglobin owing to non-enzymatic glycosylation may contribute to the increased viscosity of haemoglobin solutions (r = 0.497, P < 0.0035) and the enhanced internal viscosity of diabetic erythrocytes (r = 0.503, P < 0.003). We argue that such changes in haemoglobin, and consequently in red blood cells, might contribute to the handicapped oxygen release under tissue hypoxia in the diabetic state.

Adult↗
PubMed1993

Cystic fibrosis--V. Does cystic fibrosis alter the values of dynamic parameters of erythrocyte membrane ghosts?

1. The dynamic properties of erythrocyte membranes in CF children have been investigated by means of fluorescence and ESR techniques. 2. It has been revealed that the apparent distance separating the membrane protein tryptophan and bound 1-anilino-8-naphthalenesulphonate (ANS) molecules is decreased in CF children which results in a significant increase of the maximum energy transfer efficiency. 3. The slight increase in the ratio hw/hs of maleimide bound to membrane protein-SH groups of erythrocytes in cystic fibrosis may ensue the lowered membrane protein immobilization in the plane of lipid bilayer, especially at the intrinsic, more slowly reacting thiol groups.

Anilino Naphthalenesulfonates↗
PubMed1992

The association between erythrocyte internal viscosity, protein non-enzymatic glycosylation and erythrocyte membrane dynamic properties in juvenile diabetes mellitus.

The association of intracellular viscosity of red blood cells and the dynamic properties of erythrocyte membranes in children suffering from diabetes has been investigated by means of ESR spectroscopy. It has been revealed that the slight decrease in the ratio hw/hs of maleimide bound to membrane protein-SH groups of erythrocytes in diabetes may ensue from the enhanced membrane protein immobilization in the plane of lipid bilayer. These alterations were accompanied by a corresponding increase in the relative rotational correlation time (tau c) of iodoacetamide spin label, thus suggesting that the conformational changes in membrane proteins may occur at both the intrinsic and more exposed thiol groups. The membranes of diabetic red blood cells were more glycosylated than those of relevant controls, and the extent of glycosylation was found to correlate significantly with h + 1/h0 and tau c (r = -0.652, P < 0.01 and r = 0.609, P < 0.01). Further, the conformational alterations in erythrocyte membranes from diabetic subjects were accompanied by a significant increase in the mobility parameter (h + 1/h0) of haemoglobin molecules in diabetic erythrocytes. The latter changes correlated well with the enhanced intracellular viscosity of diabetic red blood cells and the level of glycosylated haemoglobin. We conclude that the alterations in membrane lipid-protein interactions together with the increased glycosylation-derived internal viscosity may consequently imply altered viscoelastic properties of erythrocyte membranes and, underlying the impaired deformability of red blood cells in the diabetic state, contribute to the development of late diabetic sequelae.

Adolescent↗
PubMed1990

Cystic fibrosis. IV. Structural analysis of a chloroform soluble compound isolated from gastric juice.

Cystic fibrosis (CF) is the most common autosomal disorder yet its cause is unknown. During an investigation of chloroform soluble fraction compounds of samples of gastric secretions from children with CF, a new substance was isolated. The new compound is concerned in alteration of membrane phospholipid composition, and changes in the activity of the enzyme transferring long-chain acyl moieties. Its structure is investigated, evaluated and discussed in relation to CF.

Alkalies↗
PubMed1989

Palmitylation of the glycoprotein IIb-IIIa complex in human blood platelets.

The presence of covalently bound palmitic acid in fibrinogen receptors, glycoproteins (GP) IIb and IIIa, has been explored in human blood platelets. Membrane fractions were isolated from fresh blood platelets labeled with [9,10-3H]palmitic acid and then analyzed for radioactive proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Protein bands were visualized by staining with Coomassie Brilliant Blue, excised, and counted in a liquid scintillation counter. The results indicate that membrane proteins with electrophoretic mobility corresponding to glycoproteins IIb and IIIa incorporate [9,10-3H]palmitic acid. The palmitylated glycoproteins IIb and IIIa were immunoprecipitated by specific anti-GP IIb and GP IIIa antisera. It is interesting to note that the palmitylation of these glycoproteins occurred rapidly in platelets activated with 0.5 unit of thrombin or 30 microM ADP. At the concentration used (100 micrograms/ml), cycloheximide did not inhibit incorporation of [3H]palmitate into the glycoproteins showing that this process is not dependent upon protein synthesis. The acyl moiety was resistant to denaturating detergents, delipidation with organic solvents, and hydrolyzable with hydroxylamine. In the case of membrane protein with the electrophoretic mobility of GP IIb, the radioactive label was significantly decreased after reduction with 2-mercaptoethanol. Final identification of GP IIIa as an acylated product in human platelets incubated with [9,10-3H]palmitic acid was provided by two-dimensional polyacrylamide gel electrophoresis. In contrast to GP IIb alpha, GP IIIa isolated by this method showed the presence of attached radioactive palmitic acid residues. Analysis by high performance liquid chromatography after methanolysis of the [3H]palmitate-labeled glycoproteins confirmed the fatty acid nature of the label. Palmitylation is a newly identified post-translational modification of the fibrinogen receptor which may play an important role in its interaction with the membrane and/or its biological function.

Adult↗
PubMed1989

Cystic fibrosis: II. Altered microviscosity of erythrocyte membrane.

Erythrocyte membrane fluidity alterations in cystic fibrosis are described. The relative flexibility of the membrane was studied using lipid spin label, i.e. methyl-5-doxylpalmitate (M5DP), and pyrene as a fluorescence probe. It was found that there was a decrease of membrane fluidity in the hydrophobic midzone of the membrane, probed by pyrene, as well as at the hydrophilic surface region, probed by M5DP.

Child↗
PubMed1987

Paraquat as an agent affecting antioxidant enzymes of common carp erythrocytes.

The effects of paraquat on the superoxide dismutase, catalase, glutathionine peroxidase activities and lipid peroxidation at different times of paraquat exposure of Cyprinus carpio morph L. erythrocytes were studied. Typical characteristics were observed in the changes of the enzyme activities of the erythrocytes after exposure to paraquat. The haemoglobin concentration of common carp haemolysates was decreased by exposure to paraquat.

Animals↗
PubMed1984

Comparative studies on superoxide dismutase and catalase activities in livers of fish and other Antarctic vertebrates.

The activities of superoxide dismutase and catalase in livers of fish and other Antarctic vertebrates were examined. Significant differences between superoxide dismutase activities in livers of white-blooded and red-blooded fish species were observed. Superoxide dismutase seems to be involved more than catalase in protection processes against cell damage caused by oxygen free radicals.

Animals↗
PubMed1983

Lipids associated with rat small-intestinal mucus glycoprotein.

The lipid content and composition of rat small-intestinal mucus, and the purified mucus glycoprotein before and after Pronase digestion were investigated. The mucus, obtained by the instillation of intestine with 2M NaCl, was fractionated on Bio-Gel A-50 in the presence of 6M urea and the mucus glycoprotein free of noncovalently bound protein was isolated. A portion of the purified glycoprotein was subjected to Pronase digestion to yield glycopeptides. The native mucus, and the purified glycoprotein and glycopeptides were extracted with chloroform-methanol, and the lipids contained in the extracts were analyzed. The lipids accounted for 17.6 of the dry weight of mucus, 26.4 of the mucus glycoprotein, and 25.3% of the glycopeptides. In comparison to mucus, the lipids associated with mucus glycoprotein contained 1.9 times more phospholipids and 2.1 times more glycolipids, showed a 26% increase in neutral lipids, and were virtually free of glycosphingolipids. Treatment of the purified glycoprotein with Pronase led to a moderate (22.3%) loss in neutral lipids, 4.3-fold decrease in phospholipids, and 52.3% increase in glyceroglucolipids. The results indicate that while the interaction of mucus glycoprotein with phospholipids involves its Pronase-susceptible region, the interaction with glyceroglucolipids occurs in the glycosylated region of the glycoprotein that is resistant to proteolysis.

Animals↗
PubMed1983

Covalently linked fatty acids in gastric mucus glycoprotein of cystic fibrosis patients.

Undegraded mucus glycoprotein has been isolated in highly purified form from gastric secretion of cystic fibrosis patients. The purification procedure involved gel filtrations on Bio-Gel P-100 and Bio-Gel A-50 and lipid extractions with five mixtures of the organic solvents. The final preparation represented pure glycoprotein as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, cesium chloride density gradient centrifugation, and lipid analysis. Treatment of the pure and delipidated glycoprotein with methanolic KOH or hydroxylamine resulted in liberation of ester-bound fatty acids. Of the total released fatty acids, 95% were represented by hexadecanoate (36.5%), octadecanoate (48.7%), and octadecenoate (8.6%). The quantitative analysis established that, on the average, 12.2 nmol of fatty acids/mg of glycoprotein were released. The studies on cystic fibrotic glycoprotein susceptibility to proteolytic digestion indicated that fraction of glycoprotein which was resistant to pronase digestion contained on the average 33.1 nmol of fatty acids/mg of glycoprotein. After removal of the fatty acid residues from pronase-resistant glycoprotein, by treatment with hydroxylamine, the glycoprotein became susceptible to proteolytic digestion. Thus, in cystic fibrosis, the covalently bound fatty acids interfere with proteolytic degradation of mucus glycoprotein. Perhaps this is the major defect of cystic fibrosis glycoproteins and the cause of the obstruction of secretory glands and the accumulation of poorly soluble secretions.

Adolescent↗
PubMed1983

Isolation of fatty acids covalently bound to the gastric mucus glycoprotein of normal and cystic fibrosis patients.

Covalently bound fatty acids were found in strictly purified and delipidated gastric mucus glycoprotein of normal and cystic fibrosis individuals. The susceptibility of this linkage to methanolic KOH and hydroxylamine treatment indicated the ester bond between fatty acids and glycoprotein. On the average, 2.9 nmol fatty acid/mg glycoprotein were found in normal samples, and 12.2 nmol/mg glycoprotein in samples derived from cystic fibrosis. In normal gastric mucus glycoprotein the covalently linked fatty acids consisted of hexadecanoate (47.0%), octadecanoate (22.0%), tetracosanoate (5.9%), octadecenoate (14.5%) and tetracosenoate (6.0%). In cystic fibrosis mucus glycoprotein the covalently bound fatty acids were comprised mainly of hexadecanoate (36.5%), octadecanoate (48.7%) and octadecenoate (8.6%). These data indicate that cystic fibrosis gastric mucus glycoprotein is highly acylated and perhaps this is the major defect of glycoproteins in this disease.

Centrifugation, Density Gradient↗
PubMed1983

Lipids of gastric secretion in patients with cystic fibrosis.

Lipids were investigated in gastric secretions of patients with cystic fibrosis and of normal individuals. Organic extracts from dialyzed and lyophilized samples were fractionated on silicic acid columns into neutral lipids, glycolipids and phospholipids. The lipids contained in each fraction were separated into individual components by thin-layer chromatography and quantitated. The gastric secretions of patients with cystic fibrosis contained 80-140% more lipids than those of normal individuals, exhibited an elevated level of neutral lipids and contained alkylglycerols and alkylacylglycerols. The level of glycolipids was higher in normal gastric secretions. The phospholipids of cystic fibrosis secretions exhibited about 50% lower content of lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylserine. The glycosphingolipids of both types of samples contained mono-, di- and trihexosylceramides. The major glyceroglucolipid of normal gastric secretions was tetraglucosyl glyceroglucolipid, whereas hexa- and octaglucosyl glyceroglucolipids were predominant in cystic fibrosis samples. The sulfated glyceroglucolipids in cystic fibrosis samples were lower than those of normal secretions and represented only 4-37% of total glyceroglucolipid, whereas in normal secretion sulfated glyceroglucolipids averaged 50-62%.

Cholesterol↗
PubMed1983

Association of lipids with proteins and glycoproteins in human saliva.

The distribution of lipids in the fractions of parotid and submandibular saliva following Bio-Gel A-50 column chromatography was measured. Over 50% of the total lipids of submandibular saliva was found in the fraction which contained mainly the high-molecular-weight glycoprotein. This fraction also contained most of the glycolipids, free fatty acids, phospholipids, and cholesterol. In the parotid saliva, the fraction containing the basic glycoprotein (the major glycoprotein fraction of parotid saliva) contained 35% of the total saliva lipids and was enriched in phospholipids ana cholesterol esters.

Adult↗
PubMed1982

The effect of diabetes on the activities of the peroxide metabolism enzymes.

The lipid peroxidation and (of the peroxide metabolism enzymes) the catalase, superoxide dismutase and glutathione peroxidase activities were determined in red blood cell haemolysates from 20-35-year-old human diabetics of both sexes. The results were compared with the values for normal controls from the same age group. The diabetic haemolysates displayed significantly higher glutathione peroxidase and significantly lower superoxide dismutase activities. The lipid peroxidation too was significantly higher in the diabetic haemolysates. Diabetes was induced with alloxan or streptozotocin in rats, and the enzyme activities of the blood and organ homogenates were similarly compared; in these cases the total peroxidase activity. In experimental diabetes the previously-observed phenomenon of oxidative stress was confirmed; this may serve as a logical explanation for the occurrence of the later diabetic damage.

Adult↗
PubMed1978

Down syndrome - transferrin parallels plasma iron changes.

The transferrin level was studied in patients with simple trisomy 21 and with Robertsonian unbalanced translocations 21/22 and 21/14. In all these groups of patients, known to have significantly lowered plasma iron levels, the transferrin levels were found to be decreased with respect to the control group.

Adolescent↗