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Biomedical subjects

C Balduini

Publications and source records attributed to C Balduini.

At least 73 records · Page 4Linked to original sources
PubMed1980

Interactions between bovine cornea proteoglycans and collagen.

Two types of proteoglycan subunits were obtained from bovine cornea, the first mainly composed of proteochondroitin sulphate and the second of proteokeratan sulphate. These two fractions can be obtained from the tissue as an aggregate, and are able to recombine each other after separation, to re-form the original structure. In order to investigate collagen-proteoglycan interactions, type-I collagen was isolated from bovine cornea by pepsin digestion followed by 3.5% (w/v) NaCl precipitation, and was then linked to CNBr-activated Sepharose 4B. Two identical columns were prepared, the first filled with collagen coupled to Sepharose 4B, the second with free Sepharose 4B. The two proteoglycan subunits and the aggregate were chromatographed on the two gels under the same conditions; the elution profiles showed that both the aggregate and the proteochondroitin sulphate subunit are retarded by the collagen coupled to Sepharose. No interaction, however, occurred when proteokeratan sulphate subunit was run through the columns. Chondroitinase digestion of the proteoglycan samples confirmed that chondroitin sulphate chains are mainly responsible for the interaction with collagen; their removal, in fact, completely abolishes any differences between the chromatographic behaviour on the collagen-Sepharose and the control columns.

Animals↗
PubMed1979

Membrane abnormalities of pyruvate kinase deficient red cells.

Two experimental systems have been applied to the study of PK-deficient red cells in an attempt to reveal possible membrane abnormalities of these erythrocytes: (1) the glycoprotein self-digestion of intact erythrocytes during in vitro incubation at 37 degrees C; (2) the red cell sensitivity to the lytic action of mouse macrophages. PK-deficient erythrocytes display a more precocious than normal membrane glycoprotein self-digestion and are much more susceptible than normal to the cytotoxic activity of mouse macrophages. This latter effect is more pronounced in young than in old PK-deficient red cells. These observations indicate the existence of membrane abnormality in PK-deficient red cells other than those so far suspected.

Adenosine Triphosphate↗
PubMed1978

Interactions between different corneal proteoglycans.

Proteoglycans were extracted from bovine cornea with 4M-guanidinium chloride and purified by CsCl-density-gradient centrifugation. Under associative conditions two fractions were found: one capable of forming assemblies of high molecular weight and another lacking this property. The heavier fraction (density 1.59 g/ml) was eluted as a single retarded peak from Sepharose 2B, but on DEAE-Sephadex chromatography, gave two peaks: the first (eluted with 0.75 M-NaCl) contained mainly proteochondroitin sulphate and the second (eluted with 1.25 M-NaCl) mainly proteokeratan sulphate. Each of these proteoglycans was more retarded on Sepharose 2B than was the original sample from density-gradient centrifugation. Re-aggregation was obtained by recombination of the two fractions. The lighter fraction (density 1.44 g/ml), containing predominantly keratan sulphate chains, was eluted from DEAE-Sephadex as a single peak with 1.25 M-NaCl and was retarded on Sepharose 2B: this fraction was not able to form aggregates with proteochondroitin sulphate. Chemical analyses of the carbohydrate and protein moieties of the proteoglycans from DEAE-Sephadex confirmed that, in the cornea, different subunits are present with characteristic aggregation properties and hydrodynamic volumes.

Animals↗
PubMed1978

Behaviour of young and old desialylated rabbit erythrocytes in vivo.

Young and old rabbit erythrocytes, separated by density gradient centrifugation, were desialylated by neuraminidase treatment and reinjected into the animal after 51Cr labelling. Both red cell populations are quickly removed from the circulation and trapped by the liver; then a large percentage of the young cells reappear in the peripheral blood and behaves like untreated erythrocytes; old cells, on the contrary, do not return to the blood stream and are probably lysed in the liver. These results suggest that a sialic acid repair can occur on the membrane of young erythrocytes and confirm that the loss of this molecule is not by itself sufficient to determine the death of the cell.

Animals↗
PubMed1977

Self-digestion of human erythrocyte membranes. Role of adenosine triphosphate and glutathione.

Intact human erythrocytes incubated at 37 degrees C, pH7.4, release a sialoglycopeptide similar in its chemical composition, immunological and aggregation properties to the glycopeptide released by isolated 'ghost' membranes. The presence of ATP or reduced glutathione at physiological concentrations in the incubation medium of 'ghost' membranes inhibits this self-digestion process.

Adenosine Triphosphate↗
PubMed1977

In vivo behaviour of neuraminidase-treated rabbit erythrocytes and reticulocytes.

51Cr rabbit erythrocytes were treated with different amount of neuraminidase and reinjected into the animal. The survival curves after the removal of more than 50% membrane sialic acid show a characteristic behaviour: after a rapid decrease, blood radioactivity increases again reaching a maximum level 50-80 h after reinjection, then tends to decrease with a slope similar to that of control curves. Liver radioactivity determined before the rise of blood radioactivity is evidently higher than the value determined after radioactivity elevation. Similar results were obtained with phenylhydrazine-induced young erythrocytes.

Animals↗
PubMed1977

Membrane sialic acid and behaviour in vivo of rabbit "stress" macroreticulocytes.

Membranes of rabbit reticulocytes obtained by phenylhydrazine stimulation have a chemical composition different from that of normal erythrocytes; sialic acid/protein and cholesterol/protein ratios are in fact lower than normal. In vivo study of 51Cr-labelled reticulocytes show that these cells are quickly removed from blood and, after a short "homing" in liver, return to peripheral blood. During "homing" in the liver, the sialic acid/protein ratio seems to increase.

Animals↗
PubMed1977

Experimental arthrosis from intra-articular vitamin A injection in the rabbit. Morphological and biochemical study: considerations on the pathogenesis of human arthrosis in relation to the experimental model.

The key to the pathogenesis of arthrosis lies in the mechanism responsible for the initial lesions. In this experimental work the possibility of producing arthrosic changes is demonstrated by activating lysosomal chondrocytic enzymes by the intra-articular injection of Vitamin A in rabbits. On the basis of the experimental results the authors discuss the possible role that activation of the lysosomal hydrolytic enzymes might play in producing primary and secondary arthrosis in humans. They advance the hypothesis that this mechanism may be the common final step in the degradation of the articular cartilage, whatever the aetiological factor.

Acid Phosphatase↗
PubMed1976

Identification of a sialoglycopeptide released by self-digestion from human erythrocyte membranes.

Membranes from human O Rhesus-positive erythrocyte 'ghosts' were tested in vitro for their ability to digest their own glycoproteins. 'Ghost' membranes incubated in Tris/HCl buffer, pH 7.4, release a sialoglycopeptide, which contains glucosamine, galactosamine, galactose and mainly polar amino acids. Chemical composition, molecular size and aggregation properties suggest that this glycopeptide may be a fragment of glycophorin.

Chromatography, Gel↗
PubMed1976

Glycopeptides of erythrocyte membranes in some hematological disorders.

Red cell membrane glycopeptides of subjects suffering from different hematological disorders (PNH, hemolytic anemias, dyserythropoietic anemias and polycythemia vera) have been characterized. In most cases, except in polycythemia vera, a decrease of sialic acid and galactosamine was detected. The role of these alterations is discussed with regard to the decrease of membrane glycopeptides during physiological aging of the red cell.

Adult↗
PubMed1976

Effect of some nucleotides on the regulation of glycosaminoglycan biosynthesis.

The effect of some nucleotides on UDP-glucose dehydrogenase (EC. 1.1.1.22) and UDP-glucose 4'-epimerase (EC 5.1.3.2) extracted from epiphysial-plate cartilage of newborn pigs was investigated. UDP-xylose acts as a co-operative allosteric inhibitor of UDP-glucose dehydrogenase, whereas it does not inhibit UDP-glucose 4'-epimerase activity: the inhibition of UDP-glucose dehydrogenase results in an increase of UDP-galactose synthesis, in agreement with the equilibrium constant of UDP-glucose 4'-epimerase reaction. Because of the presence of UDP-glucose 4'-epimerase activity in the enzyme extract, the addition of UDP-galactose induces an increase in reaction rate of UDP-glucose dehydrogenase. NADH inhibits both UDP-glucose dehydrogenase and UDP-glucose 4'-epimerase activities: in the presence of non-saturating NAD concentrations, NADH acts as a co-operative allosteric inhibitor of both enzymes. The inhibitory effect of NADH seems to be strikingly correlated with the value of NAD/NADH ratio and pH. In any case, the percentage inhibition of UDP-glucose 4'-epimerase, under the same experimental conditions, is always higher than that of UDP-glucose dehydrogenase.

Animals↗
PubMed1975

Biosynthesis of glycosaminoglycans: uridine diphosphate glucose 4'-epimerase from cornea and epiphysial-plate cartilage.

UDP-glucose 4'-epimerase (EC 5.1.3.2.) was extracted from newborn-pig epiphysial-plate cartilage and whole bovine cornea. The formation of radioactive UDP-galactose from UDP[U-14C]glucose was demonstrated by radioautography after separation of the sugar nucleotides by paper chromatography or t.l.c. The pH optimum and the Km values for UDP-glucose, UDP-galactose and NAD+ were determined in both tissues. UDP-galactose and UDP-glucuronic acid formation after incubation with different UDP-glucose concentrations was followed; the same experiment was carried out using different UDP-galactose concentrations and following the formation of UDP-glucose and UDP-glucuronic acid. At equilibrium, the ratio UDP-glucose/UDP-galactose reaches a value of about 3.5. The results obtained seem to indicate that UDP-glucose 4'-epimerase activity is strongly dependent on that of UDP-glucose dehydrogenase. The physiological meaning of UDP-glucose 4'-epimerase in glycosaminoglycan biosynthesis in the two tissues under study is discussed on the basis of the Km values of UDP-glucose 4'-epimerase and UDP-glucose dehydrogenase and on the basis of the rate of UDP-glucose and UDP-galactose utilization.

Animals↗
PubMed1974

Membrane glycopeptides from old and young human erythrocytes.

Glycopeptides were extracted by papain digestion from old and young human erythrocyte membranes and fractionated on DEAE-Sephadex A-25. Chemical characterization of the unfractionated samples and of the main peak eluted from the column indicates that glycoproteins of the erythrocyte membrane undergo significant decreases in sialic acid and galactosamine content with aging.

Cell Membrane↗
PubMed1973

Uridine diphosphate glucose dehydrogenase from cornea and epiphysial-plate cartilage.

1. UDP-glucose dehydrogenase (EC 1.1.1.22) was extracted from epiphysial-plate cartilage of newborn pigs and from whole bovine corneas. 2. Formation of UDP-glucuronic acid was demonstrated by radioautography after separation of the sugar nucleotides by paper chromatography or t.l.c.: in these conditions a radioactive glucuronic acid spot also appears. 3. UDP-xylose prevented the formation in the incubation mixture of both UDP-glucuronic acid and free glucuronic acid. 4. In both tissues the dependence of the enzyme activity on pH and the K(m) values for UDP-glucose and NAD(+) were determined. 5. Inhibition by UDP-xylose with respect to UDP-glucose was investigated. The plots of 1/v versus 1/[UDP-glucose], and of percentage inhibition versus UDP-xylose concentration and the Hill coefficient showed that a co-operative effect existed between UDP-xylose-binding sites. 6. The physiological meaning of the different affinities of cartilage and cornea enzymes for UDP-xylose is discussed and related to the different glycosaminoglycan contents of the two connective tissues studied.

Alcohol Oxidoreductases↗