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Biomedical subjects

L Robert

Publications and source records attributed to L Robert.

At least 145 records · Page 8Linked to original sources
PubMed1991

Prevention of leucocyte elastase-induced emphysema in mice by heparin fragments.

Heparin and its derivatives inhibit human leucocyte proteinases i.e. elastase and cathepsin G, but do not inhibit porcine pancreatic elastase and Pseudomonas aeruginosa elastase. In vitro experiments, reported here, also indicate that elastin, one of the physiological substrates of human leucocyte elastase (HLE), could decrease by 30-fold the inhibitory potential of an hexadecasaccharide heparin fragment (dp 16) isolated from CY 222. Nevertheless, the inhibitory capacity of the heparin fragment still remains elevated with IC50 = 2.7 x 10(-7) M and still inhibits HLE in its free and adsorbed state to elastin. These overall data prompted us to evaluate the influence of CY 222 in HLE-induced emphysema. Emphysema was induced in mice eight weeks old, following a single instillation of 200 micrograms of HLE. CY 222 treated animals received 2.5 mg.kg-1 subcutaneously once daily, 6 days per week during 4 weeks prior to HLE instillation, and for eight weeks following HLE instillation. The heparin fragment treatment of the mice halved the mortality rate observed early following HLE instillation. After 8 weeks, surviving animals were examined for lung histological and morphometrical changes: mean linear intercept (MLI) and internal alveolar area (ISA). The CY 222 heparin fragments exerted a protective effect against HLE-induced emphysema by decreasing by 70% the MLI; these heparin fragments exerted no effect on emphysema induced by pancreatic elastase in hamsters or mice. Heparin derivatives represent a new class of physiological HLE low molecular weight inhibitors capable of preventing HLE-induced emphysema.

Animals↗
PubMed1991

[Cellular and molecular mechanisms of aging: a review].

Since the beginning of this century, a large body of experimental data and observations accumulated concerning experimental and clinical gerontology. These data can be classified and analyzed according to the level of experimentation or observation as concerning aging at the molecular, cellular level or at higher levels of hierarchical organisation such as tissues, organs or the whole organism. Observations of these higher levels are mostly derived from epidemiological studies of human aging, horizontal studies or preferably vertical studies. The relative coherence of data collected at the molecular and cellular levels renders plausible a tentative of interpretation of aging phenomena at higher levels or hierarchical organisations from the tissues to the whole organism by using the data obtained at the molecular and cellular levels. The present article is a tentative for this kind or integrative interpretation of aging.

Aging↗
PubMed1991

[Study of the effect of procyanidole oligomers on cultured mesenchymatous cells. III. Size and form of cells and nuclei. Quantitative morphologic study].

The effect of procyanidole oligomers (PCOs) on the morphology of cultured human skin fibroblasts (FB) and swine aorta smooth muscle cells (SMC) was studied. Exposure to PCOs induced dose-dependent changes in the size, shape and arrangement of cultured fibroblasts. Smooth muscle cells did not exhibit similar changes. These findings demonstrate that procyanidole oligomers interact with fibroblasts membrane and cytoskeletal constituents. With smooth muscle cells the main site of action of procyanidole oligomers may be the basement membrane surrounding the cells, which is lacking in fibroblasts. Thus, in addition to their action on extracellular matrix constituents, i.e., collagen and elastin fibers, procyanidole oligomers affect structural components of cells, i.e., the cell membrane and cytoskeleton. This twofold action of procyanidole oligomers on mesenchymatous cells and their extracellular matrix may be a significant component of the pharmacologic action of procyanidole oligomers.

Adolescent↗
PubMed1990

Extracellular matrix.

A succinct overview of recent results on the biochemistry of extracellular matrix (ECM) is presented. The rapid expansion of this discipline over the best decades renders impossible to give an even approximately complete coverage of matrix biology. Some selected results concerning the four major families of macromolecules composing the ECM, that is, collagens (14 types described), elastin(s), proteoglycans and structural glycoproteins (especially fibronectin) are described. Special attention is directed to a crucial aspect of matrix biology: cell-matrix interactions. A number of cell membrane receptors were recently described mediating the two way information flow from the cells to the matrix via the 'programme' of ECM synthesis coded in the genome and unfolding during differentiation and from the ECM to the cells through the membrane receptors which contact the cytoskeleton. One of them at least, the elastin receptor was shown to be linked through a G-protein-phospholipase C-IP3 mediated relay to the regulation of intracellular calcium. Modifications of the ECM will therefore influence cell behaviour. Derangements of this informational feed back mechanisms appear to be involved in most age-related connective tissue diseases.

Animals↗
PubMed1990

Altered phosphatidylinositol breakdown after K-elastin stimulation in PMNLs of elderly.

The degradation of elastic fibres during atherosclerotic plaque formation in arterial wall is a well known process. The liberated elastin peptides such as K-elastin possess various biological activities: They are chemotactic for monocytes and fibroblasts, stimulate the oxidative burst and the intracellular free Ca2+ mobilisation through the phosphatidylinositol (PIP2) breakdown in PMNLs. It was found that the PIP2 breakdown induced by K-elastin is a pertussis toxin sensitive process in PMNLs of young subjects. In the case of the elderly, the K-elastin-induced oxidative burst, intracellular free Ca2+ elevation was less than in young, and could not be inhibited by pertussis toxin. Studying the K-elastin-induced inositol phosphate (IP) formation in PMNLs of elderly a disturbed PIP2 breakdown was found. K-elastin stimulated the IP formation at a very low level in PMNLs of elderly. This alteration of the second messenger formation (e.g. IP3 and Ca2+) after KE stimulation, might be the consequence of their originally elevated levels in resting PMNLs of elderly.

Age Factors↗
PubMed1990

Comparative study of the precipitation of low density lipoproteins by aortic proteodermatan sulphate and heparin.

The aortic proteoglycans and heparin were shown to form insoluble complexes with human low density lipoproteins (LDL). The effect of temperature, polyethylene glycol and ionic strength on the formation of complexes between porcine aortic proteodermatan sulphate (PDS) and LDL has been studied by laser nephelometry and comparisons made with heparin LDL complexes. Turbidity was a nonlinear function of the quantity of LDL precipitated by PDS. The turbidity of aggregates was constant at temperatures between 2 degrees C and 30 degrees C but increased with temperature above 30 degrees C up to 50 degrees C. The formation of insoluble complexes decreased rapidly with increasing NaCl concentration. Polyethylene glycol enhanced the turbidity at 20 degrees C but not at 37 degrees C. It also increased the resistance of complexes to dissociation by increasing ionic strength. The turbidity of heparin--LDL complexes was linearly correlated with the quantity of precipitated LDL. The heparin-LDL aggregates were less sensitive to modification of temperature and ionic strength than the PDS-LDL aggregates. These results suggest that ionic interactions are weaker in PDS-LDL complexes than in the heparin-LDL complexes. Non-coulombic interactions and/or temperature dependent conformational changes may be involved in the stabilization of supramolecular PDS-LDL aggregates. No such interactions or changes appear to be involved in complex formation between heparin and LDL.

Animals↗
PubMed1990

Susceptibility of baboon aorta elastin to proteolysis.

Elastin was purified from baboon aorta using Achromobacter collagenase and its susceptibility to proteolysis by various enzymes was studied. Human leukocyte elastase (HLE) hydrolysed baboon aortic elastin 8 times faster than human cathepsin G. Bovine chymotrypsin had virtually no activity against this substrate. The kinetic constants V and [S50] of aortic elastin hydrolysis by HLE (0.15 microM) were 0.00286 mg x ml-1 x min-1 and 0.158 mg x ml-1, respectively. One mg of this elastin could be saturated with 5.6 micrograms of HLE. As with elastins isolated from other sources, the hydrolysis of baboon aortic elastin by HLE was highly sensitive to ionic strength, and a biphasic effect was obtained with increasing NaCl concentrations. A nearly 2-fold stimulation of elastolysis was observed at a 0.15M NaCl concentration. Further increase in ionic strength led to a continuous decrease of the rate of elastolysis which paralleled the decrease of adsorption of elastase to baboon aortic elastin. Cathepsin G, but not bovine alpha-chymotrypsin, was able to stimulate the rate of hydrolysis of baboon aortic elastin by HLE. A 1.7 fold stimulation was observed for a 1:1 molar ratio of the two proteinases and rose to 2.1 for a HLE/Cat. G ratio equal to 8.

Animals↗
PubMed1990

[Sensory ataxia caused by central axonopathy].

Sensory ataxia with central axonopathy. A case of sensory ataxia of undefined origin is described and the differential diagnosis is discussed. The originality of the case lies in the fact that the nerve sensory potentials are preserved whereas the medullary and cortical somesthesic potentials no longer exist. This situates the pathological process in the central axon of the sensory ganglion, as in tabes or clioquinol poisoning.

Adult↗
PubMed1990

Determination of elastin peptides in normal and arteriosclerotic human sera by ELISA.

The degradation of elastin during various pathological processes such as emphysema or arteriosclerosis was demonstrated by several investigators. In the present work, we adapted an ELISA technique for the determination of elastin peptide (EP) levels in human sera and plasma, in healthy and arteriosclerotic subjects. This test makes use of human aorta elastin hydrolyzed by a chemical procedure (kappa-elastin) instead of EP produced by pancreatic or leukocyte elastase. Polyclonal antibodies to this antigen were obtained in rabbits. The indirect ELISA procedure is sensitive, specific and reproducible. No correlation could be demonstrated between EP level and anti-EP antibody concentration of IgG or IgM types determined in the same serum samples. These antibodies did not interfere with EP determinations. EP concentration did not change with age in control subjects. In obliterative arteriosclerosis of the legs and in type IIb hyperlipoproteinemia, EP levels showed a marked increase, while in hypertension, ischemic heart disease and diabetes mellitus, the increase was moderate. In stroke, only slight changes were observed. In type IV hyperlipoproteinemia, EP levels were lower than in controls.

Adult↗
PubMed1990

[The effect of procyanidolic oligomers on vascular permeability. A study using quantitative morphology].

In normal conditions vascular permeability is precisely regulated by mechanisms which involve among others the macromolecules of extracellular matrix of the vascular wall. Permeability for a given substance will vary according to the anatomical localisation of the vessel determining also its structure and composition. In some pathological conditions, such as inflammation or diabetes, permeability can be abnormally increased. Increased permeability can be reproduced by i.v. collagenase injection. This permeability increase can be quantified by image analysis using appropriate tracers such as FITC-dextrans or horse-radish peroxidase, on histological sections from control and collagenase treated rats, pretreated or not with procyanidolic oligomers (PCO). We studied cerebral capillaries, aorta and cardiac muscle capillaries. It could be shown that previous treatment of animals with procyanidolic oligomers prevented the permeability increase produced by collagenase injection.

Animals↗
PubMed1990

[The effect of procyanidolic oligomers on mesenchymal cells in culture. II--Attachment of elastic fibers to the cells].

Tissues are composed of cells and extracellular matrix (EM). Adhesion of cells to extracellular matrix is mediated by membrane-bound glycoproteins such as fibronectin, laminin and others. Elastonectin was shown recently to be involved in the mediation of interactions between elastic fibers and cells such as human skin fibroblasts (FB) and smooth muscle cells (SMC) from the media of the aorta. A strong interaction between fibers and cells is important for the maintenance of the quality of the vascular wall. We studied the action of procyanidolic oligomers (PCO) on the attachment of fibroblasts from human skin and smooth muscle cells from porcin aorta to elastic fibers. A dose-dependent increase of cell-fiber interaction could be demonstrated with both cell-types. Elastonectin is located on the cell membrane as well as an elastolytic serine-protease exhibiting an age- and pathology-dependent increase in activity. This will result in a degradation of elastic lamellae, the detachment of cells from elastic fibers and a weakening of the vascular wall. The activity of procyanidolic oligomers increasing the resistance of elastic fibers to degradation by elastases and enhancing the interaction between fibers and cells can be considered as favouring the maintenance of the normal functional state of the vascular wall.

Adult↗
PubMed1989

Identification and signal transduction mechanism of elastin peptide receptor in human leukocytes.

The existence of a novel receptor on human polymorphonuclear leukocytes (PMNLs) and monocytes was demonstrated, named soluble elastin peptide receptor. Soluble elastin peptides, like K-elastin, which are liberated from elastin fibres, can be found in the sera, and they possess several biological activities such as chemotaxis. Studying the effects of elastin peptides on leukocytes, it was found that: (i) the elastin peptide stimulates the oxidative burst, the intracellular free Ca2+ elevation through a specific receptor; and (ii) in the signal transduction mechanism of this elastin peptide receptor, the phosphatidylinositol breakdown is involved.

Adult↗
PubMed1989

Effect of testicular hyaluronidase on hyaluronate synthesis by human skin fibroblasts in culture.

The effect of hyaluronidase treatment on the incorporation of [3H]glucosamine into hyaluronate in human skin fibroblast cultures was investigated. Fourth passage cells in confluent cultures were treated with hyaluronidase from bovine tests, Streptomyces and leech in Dulbecco's minimum essential medium in the presence of 3% fetal calf serum. The medium was removed from the control (non-treated) and the treated cultures and the washed cell layers were incubated with [3H]glucosamine and [35S]sulfate. [3H]Hyaluronate was separated by DEAE Trisacyl chromatography and identified by specific enzymic assays. Hyaluronidase treatment induced an increase in the amount of labelled hyaluronate secreted into the medium and into the pericellular compartment. This amount reached a plateau with increasing enzyme concentration and with the time of treatment. Oligosaccharides derived from hyaluronate did not produce this effect. The maximal increase was about 3-fold, and was not inhibited by exogenous hyaluronate (25-100 micrograms/ml) or by oligosaccharides from hyaluronate. Cycloheximide (0.03 mM) inhibited hyaluronate synthesis by 18% or less in the control cells and by 50% in the hyaluronidase-pretreated fibroblasts. No significant difference was found in the hyaluronate synthase activity between control and treated cells, at 60 min following treatment, indicating the reversibility of the effect. The persistence of the stimulation required the presence of hyaluronidase. The treatment of cells with specific hyaluronidases (from Streptomyces and leech) or with testicular hyaluronidase did not modify the labelling of the sulfated glycosaminoglycans. The incorporation kinetics of the [3H]glucosamine into labeled hyaluronate and the increased amount of non-labelled hyaluronate determined by radiometric assay indicated a specific stimulation of hyaluronate synthesis in the hyaluronidase-pretreated fibroblast cultures.

Adult↗
PubMed1989

Elastase-like activity in cultured aortic endothelial cells.

Cultured porcine aortic endothelial cells were studied for cellular and secreted elastase activity. We describe an activity hydrolyzing the synthetic elastase substrate, succinyl(alanine)3 nitroanilide, but not elastin, which was shown to be membrane located and was not secreted to the culture medium. A different neutral proteinase activity degrading insoluble elastin was demonstrated in the culture medium following its fractionation by gel filtration high performance liquid chromatography (HPLC). Since no elastinolytic activity could be directly detected in the conditioned medium, it is likely that the chromatographic separation removed an endogenous inhibitor.

Animals↗
PubMed1989

Heparin fragments modulate the collagen phenotype of fibroblasts from radiation-induced subcutaneous fibrosis.

Acute local gamma irradiation of porcine skin induces, as in human skin, an extensive and mutilating sclerosis characterized by continuous expansion of the fibrosis invading the adjacent muscle and by accumulation of the macromolecular components of the extracellular matrix. Collagen synthesis, content, and types were studied in the presence of heparin fragments (100 micrograms/10(6) cells) in the culture medium, by measuring the incorporation of the radiolabeled precursor [3H]proline into confluent primary cultures of porcine fibroblasts obtained from normal and irradiated fibrotic dermis. Enhancement in collagen biosynthesis and deposition and preferential increase in collagen type III synthesis were observed in fibrotic fibroblast cultures when compared to those in normal dermis fibroblasts. The total collagen synthesis and the rate of collagen hydroxylation appear unmodified by heparin fragments both in normal and in fibrotic fibroblast cultures. But heparin fragments induce a 10- and 2-fold decrease, respectively, in collagen type III and type V syntheses by fibrosis fibroblasts. As only minor effects upon collagen type III and V are observed in cultures of normal dermis fibroblasts, these results highly suggest that heparin fragments are capable of specifically modulating the collagen phenotype of fibroblasts derived from radiation-induced dermis fibrosis and thus are able to regulate the fibrotic process.

Animals↗
PubMed1989

Interaction of platelets with endothelial cells: activation of a novel neutral protease.

The activation of a new neutral protease of MW 85,000 was demonstrated on interaction between porcine aortic endothelial cells and human and porcine platelets in culture. The activity of this enzyme, PECAP (platelet endothelial cell activated protease), was detected by electrophoresis on polyacrylamide gels impregnated with the substrate casein. Our results showed that the platelet-endothelial cell interaction did not involve induction of synthesis of de novo enzyme, but rather an activation of a latent enzyme. PECAP cleaved casein and fibrinogen, but had no activity against gelatin or elastin. It was not inhibited by inhibitors of metalloproteases (EDTA, 1.10 phenanthroline), serine proteases (phenylmethylsulfonyl fluoride, elastatinal), or cysteine proteases (iodoacetate, N-ethylmaleimide) and it seems to be unrelated to the previously known proteases of mesenchymal and hematopoietic cells.

Animals↗
PubMed1989

Biochemical characterization of elastin in neointimal hyperplasia of rabbit aorta.

Elastin synthesized in response to vascular injury was characterized in terms of its amino acid composition, the biosynthetic labeling of the desmosines and of the heat coacervable polypeptides present in the 2 M urea extract. Neointimal hyperplasia of the chronic variety was induced in rabbit aorta by superficial mechanical lesions. At 4 months following injury the reendothelialized neointimal thickening and the media were excised. Aliquot samples were incubated with [3H] lysine, extracted with 2 M urea, 0.1 M Tris, pH 7.4 and hydrolysed with collagenase. In the residue of the digests the [3H] desmosines were quantified after electrophoretic separation. Elastin was purified from the nonlabeled aliquots of the media and neointimal hyperplasia. It accounted for 60% and 25% of the dry weight of the media and the neointima respectively. Elastin isolated from the media and the neointima had essentially the same amino acid composition. The incorporation of [3H] lysine into desmosines and into coacervable polypeptides indicated that the synthesis of crosslinked elastin is still active in the hyperplasia at 4 months following injury.

Amino Acids↗