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Biomedical subjects

M Rabaud

Publications and source records attributed to M Rabaud.

At least 55 records · Page 3Linked to original sources
PubMed1987

A new reconstituted connective tissue matrix: preparation, biochemical, structural and mechanical studies.

A fibrinogen derivative generated by thrombin was reacted with elastin to yield a new addition product or adduct between the two proteins. Addition of fibronectin, and then of collagen, did not interfere with the basic elastin-fibrinogen reaction and conferred the qualities of an artificial connective tissue to the product. Biochemical, structural and biomechanical aspects of the new matrix were studied. Aprotinin, heparin, thiomersal, and thiourea did not inhibit the main reaction; indeed, some of these ingredients improved the matrix cohesion. Scanning electron microscopy showed the genesis of a true network whose meshes were more reticulated by the addition of thiourea. Biomechanical studies, i.e., strength and elasticity showed the thiourea matrix to be the strongest. These intrinsic properties suggest the product could have biological and clinical applications.

Biocompatible Materials↗
PubMed1987

Collagen studies in congenital cutis laxa.

A case of congenital cutis laxa (CCL) of unclear mode of inheritance associated with multiple pulmonary artery branch stenosis was extensively investigated to assess possible correlations between clinical, ultrastructural, and biochemical features. Light microscopy revealed that elastic fibers were absent in the papillary dermis, while hypoplastic elsewhere. Transmission electron microscopy showed a poor elastin matrix content in some elastic fibers, variable diameters of collagen fibrils, and abundant glycogen granules in most dermal cells. Measurement of collagen fibril diameters, using an image analyzer, was carried out in the patient and two age- and site-matched controls. A bimodal distribution was found in the upper reticular dermis of the patient. In vitro analysis of collagen in skin fibroblast cultures of the patient showed increased collagen synthesis with a balanced production of type I and type III procollagens. Our study confirms that CCL represents a disorder both of collagen and elastic connective tissue.

Cells, Cultured↗
PubMed1987

Adduct formation between soluble fibrin monomers and elastin.

Monomers of fibrin generated from fibrinogen by thrombin reacted with elastin to give a new addition product or adduct. The adduct formation results from a covalent bond between both proteins, formation of which is dependent on elastin, fibrinogen and Ca2+ concentrations; but, Factor XIIIa did not intervene. Addition of fibronectin, together with fibrinogen, as cold insoluble proteins from human plasma, and of soluble collagen from rat tail tendon did not inhibit the first reaction. This enabled us to elaborate a new artificial connective matrix.

Animals↗
PubMed1987

Effects of long-term treatment with D-penicillamine on antigen-induced arthritis in rabbits: studies on in vivo articular chondrocyte damage and in vitro collagen biosynthesis by cultured chondrocytes.

The effects of a long-term (120 days) treatment with D-penicillamine (DP) (50 mg/kg/day; i.v.) on antigen-induced arthritis were studied in rabbit. They were investigated by the terminal histological examination of the joints of different groups of rabbits (unimmunized treated or untreated, immunized treated or untreated) and the study of collagen and non-collagen protein biosynthesis by cultured chondrocytes obtained from articular cartilage of the same groups of animals. Treatment with D-penicillamine diminished the intensity of the erosions of cartilage and subchondral bone, the severity of the inflammatory synovitis, and the loss of chondrocyte clusters found in cartilage sections. In cultures of chondrocytes obtained from immunized treated rabbits, a partial or complete inhibition of the decreased biosynthesis of collagen and non-collagen proteins seen in culture of chondrocytes obtained from immunized untreated animals was observed. These results show that DP could be effective in preventing damage of chondrocytes and inhibition of collagen biosynthesis in them, phenomena important in cartilage destruction induced by a chronic immunological inflammation.

Animals↗
PubMed1986

Inhibition of human pancreatic elastase II activity on human aortic elastin by human alpha 2-macroglobulin.

Human alpha 2-macroglobulin-human pancreatic elastase II binding were investigated using a homologous substrate, human aortic elastin, in order to test the enzymatic activity. We demonstrated that two moles of alpha 2-M are required to inhibit one mole of HPEII when the enzyme is added to a mixture of elastin and alpha 2-M. In addition, when the elastase-alpha 2-M complex is prepared under some circumstances, it exhibits an elastinolytic activity.

Aorta↗
PubMed1986

Soluble fibrinogen derivatives generated by thrombin: affinity for elastin.

When human citrated plasma is dialysed against a phosphate buffer containing Ca++, citrate anions are removed, thrombin is generated and soluble fibrinogen derivatives (fibrin monomers and/or soluble fibrin polymers) are formed. These derivatives are able to combine with human or bovine elastin to form a very stable addition product or adduct. The formation of the adduct is dependent on time, Ca++ and thrombin concentrations.

Animals↗
PubMed1985

Human serum alpha 1-antichymotrypsin is an inhibitor of pancreatic elastases.

Incubation of human serum alpha 1-antichymotrypsin with human pancreatic elastase 2 or porcine pancreatic elastase results in the complete inhibition of each enzyme as determined by spectrophotometric assays. alpha 1-Antichymotrypsin reacts much more rapidly with the human than with the porcine enzyme. The inhibitor: enzyme molar ratio, required to obtain full inhibition of enzymatic activity, is equal to 1.25/1 when alpha 1-antichymotrypsin reacts with human pancreatic elastase 2 while it is markedly higher with porcine pancreatic elastase (5.5/1). Patterns obtained by SDS/polyacrylamide gel electrophoresis of the reaction products show the formation with both enzymes of an equimolar complex (Mr near 77 000) and the release of a fragment migrating as a peptide of Mr near 5000. Moreover a free proteolytically modified form of alpha 1-antichymotrypsin, electrophoretically identical with that obtained in the reaction with cathepsin G or bovine chymotrypsin, is produced in the reaction with each elastase but in a much greater amount when alpha 1-antichymotrypsin reacts with porcine elastase than with human elastase. As a consequence of our findings, the specificity of alpha 1-antichymotrypsin, so far limited to the inhibition of chymotrypsin-like enzymes from pancreas and leukocyte origin, has to be extended to the two pancreatic elastases investigated in this work. A contribution of alpha 1-antichymotrypsin to the regulatory balance between plasma inhibitors and human pancreatic elastase 2 in pancreatic diseases is suggested.

Animals↗
PubMed1985

Magnesium enhances human pancreatic elastase digestion of 125I-labeled elastin.

The effect of some divalent cations, especially Mg++, on elastinolysis by porcine or human pancreatic elastase has been determined using 125Iodine-labeled elastin as substrate. Elastin degradation was significantly increased in the presence of 10(-3) M Mg++. If elastin was pre-incubated with 0.5 (w/v) Triton, there was a further increase in elastinolysis to 2.6 times the original rate.

Animals↗
PubMed1984

Purification of human alpha 1 antiprotease-pancreatic elastase complex. Interaction with homologous elastin.

A human alpha 1-antiprotease (alpha 1.AP)-human pancreatic elastase ( HPE11 ) complex was isolated from plasma, or prepared from commercial alpha 1.AP. The complex was identified and isolated by affinity chromatography, using Concanavalin A or IgG anti-elastase as ligands, in association with Sephacryl gel filtration. The alpha 1.AP- HPE11 complex was shown to bind with aorta and with purified aortic elastin. In both cases, the complex exhibited elastinolytic activity.

Aorta↗
PubMed1984

A study of microvasculature in normal and inflammatory synovial membranes in the rabbit using light and electron microscopy and freeze fracture.

The Authors made a study of microvasculature in normal and inflammatory synovial membranes in the rabbit, by light and electron microscopy and with the use of freeze fracture. The synovial membrane of the knee was studied in 15 normal rabbits and in 22 rabbits in whom immunization with mycobacterium tuberculosis crude cytoplasmic water soluble extract had provoked inflammatory synovitis. A comparison between normal and inflammatory synovia by light microscopy showed, in inflammatory synovitis, a significant increase in the number of congested and obliterated microvessels (p less than 0.001) and in the number of endothelial nuclei per microvessel (p less than 0.0001). By electron microscopy no specific alteration of synovial microvessels was observed. A significant increase was found in the number of venules in inflammatory synovitis (p less than 0.01). The number of simple interendothelial tight junctions, defined by 1 or 2 interendothelial contacts, and of complex interendothelial tight junctions, defined by 3 or more interendothelial contacts, was similar in venules and in capillaries of inflammatory synovitis and of normal controls. The mean number and mean spacing of junctional strands in interendothelial tight junctions was similar in the microvessels of inflammatory synovitis and of normal controls. The Authors conclude that inflammation does not provoke specific alterations in synovial microvasculature but could induce an adaptative state resulting in increased synovial permeability.

Animals↗
PubMed1983

Phosphorolysis of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) and other 5-substituted-2'-deoxyuridines by purified human thymidine phosphorylase and intact blood platelets.

Various 5-substituted-2'-deoxyuridines (dUrd), including 5-ethyl,5-propyl-, 5-trifluoromethyl-, 5-hydroxymethyl-, 5-formyl-, 5-vinyl-, (E)-5-(2-chlorovinyl)-, (E)-5-(2-bromovinyl)-, 5-fluoro-, 5-chloro-, 5-bromo-, 5-iodo-, 5-cyano-, 5-thiocyano-, 5-nitro- and 5-amino-dUrd, were shown to be effective substrates for the thymidine (dThd) phosphorylase isolated from human blood platelets. Some of dUrd analogs, i.e. the highly potent and selective antiherpes agent (E)-5-(2-bromovinyl)-dUrd, were degraded more rapidly than the natural substrates, dUrd and dThd. All dUrd analogs were also readily catabolised by intact human blood platelets. The potent inhibitors of thymidine phosphorylase, 6-amino-thymine and 6-amino-5-bromo-uracil, strongly inhibited the phosphorolysis of (E)-5-(2-bromovinyl)-dUrd by both purified enzyme and intact platelets.

Blood Platelets↗
PubMed1983

[Fractionation of a sciatic nerve homogenate from normal, trembler and quaking mice on a continuous sucrose gradient].

Two fractions, characterized by biochemical criteria [quantity and density of particulate material, localization of myelin specific protein--Po, P1 and Pr--and of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and of 5'-nucleotidase], were isolated from sciatic nerve homogenate of normal, Trembler and quaking, young and adult Mice, on a continuous sucrose gradient. The fraction, at 0.58-0.6 M, the richest in membrane particles contains the myelin. The fraction at 0.7-0.75 M should contain the plasma membrane of the Schwann cell which synthesizes myelin.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1983

[Complexes of "pancreatic elastase-seric inhibitors" in swine: their behavior in the presence of homologous aortic elastin].

The present paper deals with the particular behavior of the complexes formed between pancreatic elastase and seric inhibitors in the Pig, when they were set in contact with homologous elastin. The previously known values of dissociation constants of alpha 1-antiprotease-elastase and alpha 2-macroglobulin-elastase complexes indicated they were very stable and almost irreversible. Nevertheless, our results suggest that, when the overall complexes between porcine pancreatic elastase and seric inhibitors were isolated in non drastic conditions, they might develop an elastolytic activity against elastin fibers. This result is important as regards atherosclerosis--in Human--where a destruction of elastin is involved at a early stage of the disease.

Animals↗
PubMed1983

[Demonstration of elastinolytic activity in blood or plasma].

The complexes between "elastases" and their seric inhibitors (a. 1. AP and a2. M) which could be formed in the blood, are exhibited in vitro: after incubation of serum or plasma with 125iodine labelled elastin at pH = 6, followed by extensive washing, pH was increased from 6 to 8.6: labelled peptides are released in supernatant.

Animals↗