Search PubMed⌕ Search

Biomedical subjects

L Robert

Publications and source records attributed to L Robert.

At least 73 records · Page 4Linked to original sources
PubMed1998

Preliminary data on the age-dependent decrease in basic fibroblast growth factor and platelet-derived growth factor in the human vein wall and in their influence on cell proliferation.

The roles of basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) in vein disease and aging were investigated. Smooth muscle cells from human saphenous veins were cultured. The age dependence of bFGF and PDGF activation of the smooth muscle cell proliferation was determined, and the bFGF and PDGF contents in vein wall homogenates were measured by an enzyme-linked sorbent assay. There were morphological alterations in the cells with more polygonal and polynucleated cells in cultures from aged donors, similar to those observed in vitro in aged cell cultures. Some cultures did not reach confluency after the tenth passage, suggesting early decay of the cultures from diseased veins. bFGF and PDGF stimulated the proliferation of the vein smooth muscle cells, but only in cultures treated with hyaluronidase. This stimulation decreased with the age of the donor. The amount of the two growth factors in human vein walls decreased with donor age. The amount of bFGF decreased faster (slope: 3.3138 ng/mg DNA/year) than that of PDGF (slope: 1.021 ng/mg DNA/year). This results in an age-dependent change in the bFGF/PDGF ratio from 4 mol/mol at the age of 20 years to 1 mol/mol at the age of 80. These growth factors also modulate the synthesis of extracellular matrix components. The continuous change in the bFGF/PDGF ratio may alter the composition of the extracellular matrix of the vein wall during aging and thus its susceptibility to varicose disease.

Aging↗
PubMed1998

Mechanisms of aging of the extracellular matrix: role of the elastin-laminin receptor.

Aging of connective tissues is important for the understanding of aging mechanisms of tissues rich in extracellular matrix and of age-dependent diseases often affecting such tissues. Aging mechanisms of such tissues can be divided as follows: (1) age-dependent modifications of matrix biosynthesis; (2) postsynthetic modifications of extracellular matrix, and (3) modifications of cell-matrix interactions. Examples are discussed for all three aspects of tissue aging, with special emphasis on the role of epigenetic reactions. These reactions include the Maillard reaction, uncontrolled proteolytic degradation, and free radical release. Proteolytic fragments of fibronectin and of elastic fibers were shown to produce noxious effects and to be engaged in vicious circles of autoentertained and self-amplified mechanisms. We studied in particular the role of the elastin-laminin receptor in tissue aging and in atherogenesis. The presence of saturating concentrations of elastin peptides in the circulation results in a chronic overstimulation of the receptor with sustained free radical and lytic enzyme production. Other examples of age-dependent uncoupling of receptors also illustrate the importance of altered receptor function in tissue aging and related pathologies.

Aging↗
PubMed1998

Epitope specificity of monoclonal and polyclonal antibodies to human elastin.

Polyclonal (pAb) and monoclonal (mAb) anti-human aorta elastin antibodies were reacted with a series of overlapping hexapeptides along the human tropoelastin sequence covering exons 2-7 and 23-36 from the N-terminus to the C-terminus, advancing 1 amino acid residue each time. ELISA indicated reactive epitopes. mAb A2.1 recognized sequences containing Ala-Lys, mAb G8.1, A7.1 and pAb, hydrophobic sequences. None of them reacted with the hexapeptide VGVAPG, or with desmosine or isodesmosine. pAb L85 reacted with a His-containing sequence coded in exon 26A. pAb kappaE(L), kappaE(S) and L85 reacted with the Cys-containing sequence of exon 36. A synthetic 14-residue peptide containing the three proximal tyrosines coded in exon 13 did not react with any of the antisera tested. It appears therefore that the most frequently recognized epitopes are hydrophobic sequences. One polyclonal antibody detected several isoforms of tropoelastin in the medium of cultured vascular smooth muscle cells. Monoclonal and polyclonal antibodies stained elastic fibers on tissue sections, suggesting that the epitopes recognized are available on the native fibers for reaction with the antibodies.

Amino Acid Sequence↗
PubMed1998

Taenia solium: description of the intestinal implantation sites in experimental hamster infections.

Experimental infections in golden hamsters with viable Taenia solium metacestodes were used to study by light and electron microscopy the implantation site of the adult tapeworm in the intestinal wall. Implantation sites from 3-, 4-, 10-, and 40-day infections were located in the upper third of the duodenum, excised and fixed in Zenker's or Karnovsky's solution, embedded in Polybed resin, and sectioned longitudinally to observe the position of the worm on the intestinal wall. The scolex of the tapeworm was situated between host villi, with the rostellum penetrating the intestinal wall and the suckers entrapping adjacent villi. Serial sections through several whole implantation sites revealed that the worm was anchored to the host by all 4 suckers simultaneously, each of which was located at a different level and had entrapped intestinal villi in its cavity. Host tissue within the suckers was damaged, exhibiting various degrees of cell lysis and necrosis of epithelial and submucosal cells. The tegumentary surface and microtriches of the scolex were well preserved, with occasional coalescence of tegumentary microvesicles in 10- and 40-day-old infections; microtriches were in direct contact with the damaged host tissue. This study is the first morphological and ultrastructural description of the attachment of T. solium to the intestinal wall employing an experimental model, the results of which may contribute to a better understanding of the biology of human tapeworm infections.

Animals↗
PubMed1998

Aging and matrix biology.

This introduction to a theme issue of Pathologie Biologie on the extracellular matrix starts with a brief overview of the advances made over the last few years and of the increasing specialization they have resulted in. A review is then presented of cell-matrix interactions, with emphasis on those mediated by the elastin-laminin receptor during physiologic processes and during aging and age-related diseases. The activated human lymphocyte expressing the elastin-laminin receptor is used as an example. When exposed to low levels of elastin peptides (kappa-elastin, 75 kappa D, 1-10 micrograms/ml, i.e., 1.4 to 14.10(-8)M), this receptor mediates increases in cell growth and in the production of serine-elastase. Levels of about 100 micrograms/ml are associated with cell death due to necrosis and to apoptosis. This example illustrates the key role played by epigenetic phenomena in aging of cells and tissues.

Aging↗
PubMed1998

Biological effects of elastin peptides.

Atherosclerosis is clearly one of the most life-threatening diseases and a major cause of morbidity and mortality in industrialized countries. Typical arterial lesions contain both cells originating from the blood (monocytes/macrophages) and locally-recruited smooth muscle cells. The structure of the artery is profoundly disrupted. Degradation of arterial elastin fibers results in loss of elasticity, and several elastin peptides are released that can interact with various cells via an increasingly well-characterized elastin receptor. Elastin receptor-mediated reactions that are of obvious physiologic importance include vasodilating effects and induction of mesenchymal cell adhesion to elastin fibers. Other effects are potentially harmful, such as increased elastase production, free radical release, induction of LDL oxidation, and stimulation of endogenous cholesterol production. These deleterious effects become predominant during aging as a result of chronic exposure of the elastin receptor to circulating elastin peptides. This review describes the results of recent investigations into the biological effects of elastin peptides.

Animals↗
PubMed1998

Interactions of elastin fibers with fibroblasts a time-lapse cinemicrographic study.

Adhesion of cells to the extracellular matrix is mediated by structural glycoproteins such as fibronectin and laminin, and also elastonectin, whose role is to ensure binding of elastin fibers to cells. Interactions between elastin fibers and human skin fibroblasts cultured in a Rose chamber were investigated by using cinemicrography to observe elastin fiber attachment, detachment, and displacement over a five-day period. Elastin fiber displacement over the cell layer resulted in aggregation, which was measured using morphometry. The total number of isolated elastin fibers or aggregates decreased between 1 h and 8 h and remained stable thereafter. During the same time interval, significant decreases occurred in the numbers of isolated fibers and small aggregates (perimeter < 0.268 mm; surface area < 894 microns 2), whereas larger aggregates were formed. After 15 hours of interaction, none of the aggregates had a perimeter greater than 0.536 mm, consistent with an increase in aggregate compacting. These data demonstrate that elastin-cell interactions do not occur at random. These interactions may play a pivotal role in morphogenesis and in maintaining the integrity of elastic tissues such as the arterial wall, lungs, and skin.

Cells, Cultured↗
PubMed1998

Extracellular matrix and blood-brain barrier function.

The blood-brain barrier (BBB) is a functional characteristic of the cerebral microvasculature that determines which molecules can travel from the bloodstream to the brain parenchyma and vice versa. During the last few decades, we have investigated the contribution of vascular extracellular matrix (ECM) to BBB function. The present review analyzes our findings in the light of recent data on age-related brain function alterations and discusses the potential contribution of BBB function impairment to the processes that determine these alterations.

Animals↗
PubMed1997

Influence of ePTFE polymer implant permeability on the rate and density of corneal extracellular matrix synthesis.

Microporous polymers have great potential for the production of corneal keratoprosthetic devices. Keratocytes invade the pores of expanded polytetrafluoroethylene implants (ePTFE) and collagen synthesis occurs. This ePTFE becomes translucent after its implantation in the stroma of rabbit cornea. The rate and density of cell growth within this polymer depends on the implant thickness, pore size, and its placement in the cornea. We have investigated the influence of the polymer permeability on the collagen and protein contents ePTFE implants. Rabbit corneal stroma were implanted with ePTFE disks (6 mm in diameter) by intralamellar keratoplasty. The implanted polymers were removed from the stroma after 3 to 6 months. The collagen and protein contents were determined after pepsin solubilization. The collagen content of the high-permeability implant was 3.7-fold greater than that of the low-permeability implant 3 months after implantation and 2.4-fold greater after 6 months. The total protein content of the high-permeability implant was 2.5-fold greater than that of low-permeability implant at 3 months and was the same after 6 months. The collagen-to-protein ratio was 68% in the high-permeability implants, and thus similar to that of normal corneal stroma. Thus, high polymer permeability increased both the rate and density of the corneal extracellular matrix ingrowth.

Animals↗
PubMed1997

Corneal hyaluronan content during post-ablation healing: evidence for a transient depth-dependent contralateral effect.

The hyaluronan content during wound healing following excimer laser photoablation was investigated. Rabbit corneas were photoablated (Summit Omnimed, 193 nm, 5 mm diameter, 50 microns and 100 microns depth). Central optical zones of photoablated and contralateral corneas were removed 7, 30 and 90 days after surgery. Corneas from 2 untreated rabbits were used as control. Hyaluronan content was determined after pepsin-solubilization using an alkaline-phosphatase linked hyaluronectin sorbent assay. The hyaluronan content of non-photoablated contralateral corneas was significantly increased and the changes appeared depth dependent. Hyaluronan content returned to control levels by the first month at 50 microns depth and by the third month at 100 microns depth in contralateral corneas. The hyaluronan content of the photoablated corneas was not significantly different from that of the non-photoablated contralateral sample regardless of the depth of photoablation. By contrast, the hyaluronan content of the treated corneas was significantly higher than that of the controls during the first month post-surgery and returned to control values by the third month. Thus the hyaluronan contents in the photoablated and contralateral corneas after excimer laser corneal photoablation were very similar during wound healing. This study shows that excimer laser photoablation induced transient depth-dependent contralateral alterations of the hyaluronan content.

Animals↗
PubMed1997

Lymphocytes in human atherosclerotic plaque exhibit the elastin-laminin receptor: potential role in atherogenesis.

The purpose of this immuno-histochemical study was to investigate if lymphocytes, present in the human atherosclerotic plaque, exhibit the elastin-laminin receptor. We showed recently that human activated lymphocytes in vitro express this receptor. Briefly, we demonstrated by immuno-localization experiments and by flow cytometry that this receptor is available on the cell surface of human activated lymphocytes, free to react with ligands and show capping. The activation of this receptor by elastin peptides triggers several cellular reactions of biological interest as shown previously such as chemotactic movement to an elastin peptide gradient, modulation of the biosynthesis of connective tissue macromolecules, increase of protease synthesis and release of free radicals (O2-., NO.) from mononuclear and endothelial cells, modifications of ion fluxes and also increase of cell proliferation. All these processes may contribute to the development of the atherosclerotic lesion. Two of the previously demonstrated cell reactions mediated by the receptor could be demonstrated also on PHA-stimulated human lymphocytes namely stimulation of cell proliferation and increase of elastase activity. We demonstrated in the present immuno-histological study that about 50-60% of lymphocytes of the human atherosclerotic plaque obtained by endarterectomy express the 67 kDa subunit of the elastin-laminin receptor confirming that the above described phenomena could contribute to the chronicity of the lesion.

Aged↗
PubMed1997

Aging of the vascular wall: serum concentration of elastin peptides and elastase inhibitors in relation to cardiovascular risk factors. The EVA study.

The relations of biological markers of extracellular matrix (plasma elastin peptides and elastase inhibitors) to the clinical history of cardiovascular diseases and risk factors for atherosclerosis were examined in a large population study (the EVA Study) on vascular and cognitive aging performed in 1389 men and women aged 59-71 years. A moderate decrease in elastin peptides was observed in women with a self-reported history of coronary heart disease (P < 0.091) and stroke (P < 0.03) as well as with diabetes (P < 0.043). Similar but non-significant trends were found in men. Furthermore, elastin peptides were significantly and positively correlated to HDL-cholesterol and apolipoprotein A1 in both sexes. On the other hand, elastase inhibitor titers were significantly higher in women than in men. A moderate increase was also found in men (P < 0.097) and women (P < 0.068) with a history of coronary heart disease that reached significance level after pooling both sexes (P < 0.014). Furthermore, elastase inhibitor titers were significantly and positively related to fibrinogen and C reactive protein in either sex. No consistent associations were observed between both biological markers of extracellular matrix and age, blood pressure, body mass index and tobacco or alcohol consumption. These results suggest that a decrease in elastin peptides and an increase in elastase inhibitors might be associated with risk factors of atherogenesis as well as with atherosclerosis-related diseases.

Aged↗
PubMed1997

Effect of lithium on superoxide production and intracellular free calcium mobilization in elastin peptide (kappa-elastin) and FMLP stimulated human PMNS. Effect of age.

The effect of lithium pretreatment on superoxide anion production and intracellular free calcium levels was investigated in polymorphonuclear leukocytes (PMN) from middle-aged and old individuals after stimulation by elastin peptides or FMLP. K-elastin (KE) significantly stimulated the production of superoxide anion by PMNs from middle-aged subjects, while this stimulation decreased with age and was absent in PMNs of elderly arteriosclerotic patients. Li pretreatment slightly increased this stimulating effect of KE in PMNs from middle-aged subjects and elderly arteriosclerotic patients, while slightly decreased in healthy elderly subjects. Moreover, Li was able to increase superoxide anion production even in the absence of KE, but this effect decreased also in PMNs of healthy and arteriosclerotic elderly patients. FMLP significantly increased superoxide anion production in all age-groups, but this effect was further amplified by Li only in PMNs of middle-aged subjects. In aged individuals Li pretreatment slightly decreased the effect of FMLP and had no effect in arteriosclerotic patients. Ca-mobilization induced by KE was inhibited by Li pretreatement in each age group. This inhibition by Li was much weaker in FMLP-stimulated PMNs. Li pretreatment did however modify the shape of the Ca-transient curves in FMLP stimulated leukocytes suggesting a qualitative modification of ion channel regulation. No such shape change of Ca-transient curves was observed after KE stimulation of Li pretreated PMNs. It appears that the regulation of these two receptors is differently affected by Li treatment.

Adult↗
PubMed1997

Effect of age on the vasodilatory action of elastin peptides.

We have recently shown, on young adult rat aorta rings, that elastin peptides induce a dose and endothelium-dependent vasodilation mediated by the 67 kDa subunit of the high affinity elastin-laminin receptor and, at least in part, by EDRF (NO). Here we have studied the effects of elastin peptides at circulating concentrations and below, on noradrenaline-contracted rat aortic rings, as a function of age. First, we have observed that, unlike 2-month-old (2M), 4-6-month-old (4M) and 12-month-old (12M) rat aorta rings, 30-month-old (30M) rat aorta rings were unable to maintain their contraction in long lasting experiments. Secondly, elastin peptides at physiological circulating concentrations (10(-6)-10(-3) mg/ml) induce a dose-dependent vasodilation on 4M rings. By contrast, only higher elastin peptide concentrations (10(-3) mg/ml) were effective on 12M rings, whereas rings from both younger (2M) and older animals (30M) did not respond to elastin peptides. Finally, using lactose and laminin as inhibitors, we have demonstrated that elastin peptide-induced vasodilation on 4M and 12M rings is mediated by the 67 kDa subunit of the elastin-laminin receptor. These experiments suggest that the functional availability of the 67 kDa subunit of the elastin-laminin receptor changes with age. It could be hypothesized that in young animals (0-2M) the reusable shuttle role recently demonstrated for the 67 kDa receptor subunit during elastic fiber formation leads to a major decrease in its availability for signal transduction. On the contrary, in adult animals. (4-12M), when developmental elastogenesis is completed, this subunit is essential for extracellular signal transduction. Inefficiency of this receptor in old animals (30M) can be attributed to its uncoupling from its transduction pathway, as previously shown on human cells. Finally, the age-dependent variations of circulating elastin peptide concentration and elastin-laminin receptor responsiveness to elastin peptides are two independent parameters which could influence the vascular tension regulation.

Aging↗
PubMed1997

Fibronectin in bovine vitreous. An immunochemical study.

The vitreous body is a transparent gel essentially composed of hyaluronan, collagen and proteoglycans. These components are assembled in a three-dimensional structure that is maintained by self-aggregation of macromolecules and the interactions between these different macromolecules. We confirmed the presence of fibronectin in vitreous body using immunochemical methods and by indirect immunofluorescence on cryostat sections. We also determined its distribution in vitreous extracts as compared to those of collagen, proteoglycans and hyaluronan. Because of its high affinity to these macromolecules fibronectin in the vitreous appears to play an important role in strengthening and stabilizing the gel structure.

Animals↗
PubMed1997

Synthesis of glycoconjugates by human diseased veins: modulation by procyanidolic oligomers.

Venous diseases become steadily more common and severe with age, and are often accompanied by venous lymphatic oedema. We have investigated the role of glycoconjugates in this disorder and the action of procyanidols used to treat these diseases. Explants of vein wall from patients with or without venous lymphatic edema were cultured for 24 hours and the incorporation of radioactive glucosamine into total glycoconjugates and into hyaluronan was measured. The explants from patients with oedema incorporated more glucosamine than those without oedema (+42% expressed as c.p.m./mg dry weight into total glycosaminoglycans and +12% expressed as c.p.m./mg dry weight into hyaluronan). The explants from oedematous patients secreted less glycoconjugates into the culture medium than those from non-oedematous veins (-63% of total incorporated radioactivity into hyaluronan and -66% into hyaluronidase-resistant glycoconjugates). Explants placed in medium containing procyanidols (1 mg/ml, 2.8 mM) incorporated less glucosamine (-19%) and secreted more into the medium (+119%). Glycoprotein and sulphated glycosaminoglycan synthesis were mainly affected which may well explain the beneficial effect of procyanidols on vein disorders.

Adult↗
PubMed1997

Human helper and memory lymphocytes exhibit an inducible elastin-laminin receptor.

We showed recently that human activated lymphocytes express the elastin-laminin receptor. In this study, we were interested in the kinetics of the induction of this receptor on human activated lymphocytes in vitro and in the quantification of its expression on different human lymphocyte subsets. It appears that the expression of the elastin-laminin receptor is a general property of most activated human lymphocytes but strongly dependent on the lymphocyte subsets. It appeared that the helper (CD4+) and memory (CD45RO+) lymphocytes exhibited the strongest increase of elastin-laminin receptor expression when cultured for 72 h in the presence of 2 microg/ml elastin peptides (2.7x10[-8] M) as compared to control cells. Activation of this receptor by elastin peptides triggers the stimulation of biosynthesis and release of a PMN-like elastase. Activated T lymphocytes (mostly helper and memory T cells) are present from early stages of the atherosclerotic process and this release could contribute to the progression of the lesion by engaging a vicious circle with more elastin peptides released attracting more mononuclear cells and increasing their elastase production.

Antibodies, Monoclonal↗