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C Balduini

Publications and source records attributed to C Balduini.

At least 55 records · Page 3Linked to original sources
PubMed1989

The occupancy of glycoprotein IIb-IIIa complex modulates thrombin activation of human platelets.

Platelet membrane glycoprotein (GP IIb-IIIa), besides its activity as adhesive protein receptor, displays a number of properties supporting its involvement in the mechanisms of transduction of the activation signal. Recently we have observed that GP IIb-IIIa ligands, mostly fibrinogen, inhibit Ca2+ movement and cytoskeleton reorganization caused by mild platelet activation. These findings led us to investigate the effect of GP IIb-IIIa ligands on agonist-induced platelet responses, with particular attention to the two major messenger generating systems, involving the activation of phospholipase C and the inhibition of cAMP production. In this paper we demonstrate that the occupancy of the major adhesive protein receptor on the platelet surface modulates the phosphatidylinositol cycle decreasing the amount of IP3, IP2 and IP produced after mild platelet activation as well as the pattern of protein phosphorylation. The platelet cAMP content of activated platelets was also affected and kept higher when evaluated under the same experimental conditions. Our data provide evidence for a role of fibrinogen binding in regulating the degree of activation of circulating platelets.

Blood Platelets↗
PubMed1989

Keratan sulphate: a functional substitute for chondroitin sulphate in O2 deficient tissues?

Keratan sulphate and chondroitin sulphate can each fill space and exert swelling pressure in collagenous fibrillar matrices, but whereas the former is synthesised from glucose precursor without consuming NAD, the latter converts 2 mols of NAD for each uronate residue in the polymer chain. We suggest that the observed distribution of keratan sulphate and chondroitin sulphate in cartilage, cornea and intervertebral disc are determined by the ambient oxygen tension, and that keratan sulphate is preferentially synthesised in conditions of oxygen lack. The implications of this hypothesis in the physiology of contact lenses, cartilage degeneration, corneal scar repair and ageing are discussed.

Aging↗
PubMed1988

Effect of GPIIb-IIIa complex ligands on calcium ion movement and cytoskeleton organization in activated platelets.

We studied the influence of the occupancy of the fibrinogen receptor (GP IIb-IIIa complex) on two early aspects of agonist induced platelet activation: the increase of the intracellular Ca2+ concentration and the cytoskeleton reorganization. A monoclonal antibody, a peptide containing the RGD sequence and fibrinogen purified from human plasma were used as GP IIb-IIIa ligands. The obtained results demonstrated that fibrinogen receptor occupancy inhibits Ca2+ movement and cytoskeleton reorganization caused by low thrombin concentration and ADP.

Adenosine Diphosphate↗
PubMed1987

Re-evaluation of the structural integrity of red-cell glycoproteins during aging in vivo and nutrient deprivation.

Results presented in this paper show that removal of white-cell contaminations from human red blood cells by filtration through cellulose [Beutler, West & Blume (1976) J. Lab. Clin. Med. 88, 328-333] is a necessity whenever red cells are incubated at elevated temperatures or haemolysed after density separation. Omission of this precaution results in proteolysis of sialoglycoproteins in membranes from less-dense (young), but not dense (old), subpopulations. This proteolytic damage occurs during haemolysis of the cytoplasmic domain of glycophorin. A different type of proteolysis occurs if white-cell-contaminated red cells are incubated in the absence of glucose at elevated temperatures. Red cells release sialoglycopeptides. This process is stimulated by Ca2+ ions and is accompanied by the release of vesicles that differ from spectrin-free vesicles [Lutz, Liu & Palek (1977) J. Cell Biol. 73, 548-560]. This sialoglycopeptide release is dependent on white-cell contamination and is not required for the release of spectrin-free vesicles.

Cell Separation↗
PubMed1987

Severe platelet dysfunction in a patient with autoantibodies against membrane glycoproteins IIb-IIIa.

A young women affected by Hodgkin's disease developed chronic autoimmune thrombocytopenic purpura. Splenectomy induced normalization of her platelet count, but hemorrhagic symptoms did not disappear. The patient's platelets did not aggregate in response to collagen and ADP and the IgG fraction of the patient's plasma induced the same defect in normal platelets. The women's IgG recognized glycoproteins IIb and IIIa of normal platelet membranes. Prednisone therapy induced the disappearance of bleeding symptoms and the normalization of platelet aggregation.

Adult↗
PubMed1987

Organization of membrane constituents in human erythrocytes of different age.

The effect on the structural integrity of membrane glycoproteins of different methods for the isolation of human red cell subpopulations has been investigated. Moreover the extent of sialylation of membrane glycoconjugates in red cells of different age has been studied by a quantification of WGA binding sites at the single-cell level by cytofluorometric techniques, using the FITC-labeled lectin; the surface distribution of these sites has also been described by recording fluorescence intensity maps of cell surfaces.

Binding Sites↗
PubMed1986

"In vitro" fibril formation of type I collagen from different sources: biochemical and morphological aspects.

Acid soluble type I collagen was prepared from foetal and adult bovine tendon and skin and from adult bovine cornea. The degree of hydroxylysine glycosylation and the hydroxylysine di-to monoglycoside ratio as well as the "in vivo" fibril diameters, were shown to be tissue and age-dependent. Fibrils of type I collagens were reconstituted "in vitro" monitoring at 313 nm. The fibrils obtained were examined by electron microscopy. It was shown that the "in vitro" lateral growth of collagen fibrils leads to the formation of fibrils with maximum diameters which may be correlated to those of the corresponding native fibrils. Moreover it is suggested that one of the factors controlling the lateral growth of collagen may be at the level of hydroxylysine glycosylation.

Animals↗
PubMed1985

Mechanisms of thrombin-induced modifications of human platelet cytoskeleton.

Thrombin treated with phenylmethanesulphonyl fluoride, like active enzyme, promotes modifications to human platelet cytoskeleton. The removal of active thrombin by hirudin partially reverses this process. Chymotrypsin-treated platelets do not modify their cytoskeleton after thrombin stimulus, but are still able to increase their adhesiveness to collagen. It is concluded that thrombin influences the cytoskeleton and adhesion by non-enzymic mechanisms which may be mediated by different modulators.

Blood Platelets↗
PubMed1985

Thrombin increases the adhesion of washed human platelets to collagen.

Thrombin stimulates the adhesion of washed human platelets to fibrillar collagen. This phenomenon occurs also when platelets, before thrombin stimulation, are resuspended in the presence of prostaglandin E1 to minimize the release reaction. Enzymatic activity of thrombin is not necessary for the enhancement of platelet adhesiveness, since phenylmethylsulphonylfluoride inhibited thrombin is effective in this respect. Detachment of thrombin from thrombin treated platelets by the use of hirudin restores normal platelet adhesiveness to collagen.

Chromatography, Affinity↗
PubMed1985

Prognostic factors in non-Hodgkin's lymphomas.

Prognostic factors were investigated in 67 patients with non-Hodgkin's lymphomas, homogeneously staged and treated (COP or CHOP according to low or high malignant histotype). A large number of parameters were scrutinized in order to recognize those exhibiting a prognostic value regarding length of survival. All the parameters that singly appeared to influence survival were entered into a multiple regression factor analysis. The erythrocyte sedimentation rate (ESR), higher or lower than 35 mm at the 1st h, better discriminated the groups of patients surviving or not at a given time. The histologic type, according to the Kiel classification of malignancy, was the second best prognosticator when a short-term prediction was requested (survival or death after no more than 2.5 years), but showed insufficient statistical weight for predicting longer survivals (greater than 4 years). Stage seemed to be the third best prognosticator for the first years of survival, but only the second best for longer survivals. Other parameters had very low prognostic importance when compared with those above. The results were substantially confirmed by 28 other patients, taken as controls. The importance that such a simple and easy test as ESR may be adequate with regard to prognosis is emphasized.

Adult↗
PubMed1984

Modification of membrane protein organization during in vitro aging of human erythrocytes.

In in vitro aged human erythrocytes, the presence of protein clusters can be found on the membrane; these clusters are made up of peptides held together by disulfide bridges, since they can be nearly completely dissociated by dithiothreitol treatment. SDS-polyacrylamide gel electrophoresis after dithiothreitol dissociation indicates that the aggregates are made of peptide fragments with a molecular weight ranging from 20 to approximately 110 kdalton; none of these fragments correspond to an intact protein component of the membrane. Their formation results from oxidation and proteolysis of membrane, and perhaps cytoplasmic proteins.

Amino Acids↗
PubMed1984

The role of plasma fibronectin in platelet adhesion to collagen.

Human washed platelets were eluted from columns of Sepharose 4B linked to different preparations of collagen in order to evaluate cell adhesion. Collagen preparations characterized by low and high affinity toward platelets were identified. In our experiments, fibronectin purified from human plasma modified platelet adhesiveness, though not dramatically. When washed platelets, resuspended in a buffer containing fibronectin, were filtered on a low-affinity collagen-Sepharose, a significant increase in their adhesion occurred. A similar modification could be observed when platelets were allowed to adhere to the same collagen-Sepharose preconditioned with fibronectin. The effect of fibronectin was otherwise negligible when the high-affinity collagen was used for the experiments.

Chromatography, Affinity↗
PubMed1983

Membrane processes during 'in vivo' aging of human erythrocytes.

Membrane modifications occurring during in vitro and in vivo aging in human erythrocytes have been investigated. The structural damages are the consequence of proteolytic and oxidative processes and involve both glycoprotein and protein component of the membrane. The target of these processes seems to be the same during in vitro and in vivo aging.

Erythrocyte Aging↗
PubMed1982

Membrane processes in myotonic dystrophy during in vitro aging of erythrocytes.

The present communication is devoted to investigating the possibility that in myotonic dystrophy (MyD) a decreased ATP utilization by the membrane may produce modifications in glycoprotein structure and/or in the supramolecular arrangement of some membrane proteins. The study was carried out a) by determining the membrane sialic acid content and the cellular ATP concentration in 10 cases of MyD, b) by evaluating the structural modifications of membrane glycoproteins occurring during in vitro incubation, c) by testing the presence on the membrane of high molecular weight aggregates of proteins, and d) by evaluating the distribution of hydrophobic and hydrophilic domains of the membrane by using 1-anilino-8-naphthalene sulfonate (1,8 ANS) as a fluorescent probe. Our evidence suggests that the ATP concentration and membrane sialic acid content are within normal values. Only in two cases did structural modifications of membrane glycoproteins occur while the supramolecular assembly of membrane proteins could be considered normal. The fluorescent probe behaviour after in vitro aging was indicative of a decreased polarity of its environment.

Adolescent↗
PubMed1982

Anomalous erythrocytes produced by rabbits with liver damage.

Rabbit "stress macroreticulocytes" complete their membrane sialic acid content after a short "homing" in the liver. Since also normal rabbit reticulocytes are characterized by a low membrane sialic acid, the role of the liver in the maturation of these cells was investigated. For this purpose red cell modifications consequent to a severe liver steatosis, induced in rabbits by a diet lacking choline, were investigated. Animals with liver damage showed severe anemia and red cell membranes were demonstrated to have a low sialic acid content. Moreover rabbits with severe fatty liver, unlike normal animals, were not able to restore the viability of desialylated normal young erythrocytes. On the basis of these and others evidences we suggest that rabbit liver plays an important role in physiological maturation of reticulocytes.

Animals↗
PubMed1981

Ageing of rabbit red cells in vitro: membrane modifications and their possible role in red cell survival in vivo.

In vitro incubation induces, in rabbit red cell membranes, significant modifications consisting mainly in a decrease of sialic acid and galactose. In vivo the life span of incubated erythrocytes seems to be correlated to the degree of surface alterations and ATP depletion: larger surface modifications and energy charge reduction induce shorter survival time. It can therefore be postulated that incubation of red cell in vitro can cause an ageing process similar to that occurring physiologically in vivo.

Adenosine Triphosphate↗
PubMed1981

Reversible and irreversible structural modifications of erythrocyte membrane.

Membrane glycoprotein structure regulates the fate in the circulation of mammalian erythrocytes: the mechanism of this phenomenon was observed in rabbit and human red cells by in vivo and in vitro experiments. Glycoprotein remodeling can occur as a reversible desialylation process, produced by different events, or as an irreversible process consisting in a loss of sialoglycopeptides. The effect of these two phenomena on the viability of the red cell in the circulation was the subject of our investigation.

Amino Acids↗