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Biomedical subjects

I Drubaix

Publications and source records attributed to I Drubaix.

14 recordsLinked to original sources
PubMed1999

Effect of in vitro aging on the biosynthesis of glycosaminoglycans by human skin fibroblasts. Modulation by the elastin-laminin receptor.

The incorporation of a radioactive precursor 3H-glucosamine in glycoconjugates, essentially glycosaminoglycans (GAG) was evaluated in the culture medium and cell fraction of human skin fibroblasts. Using increasing passage numbers, we could estimate the effect of in vitro aging on these biosynthetic activities. The incorporation in different free (hyaluronan) and protein bound (proteoglycans) GAGs was evaluated after specific enzymatic digestion. Most newly synthesized GAGs were excreted in the extracellular medium. Incorporation of the tracer in hyaluronan, the major biosynthetic product, increased with passage number but its titratable concentration decreased with in vitro aging, suggesting a rapid post-synthetic degradation. The proportion of chondroitin sulfates 4 (A) and 6 (C) and heparan sulfate decreased and that of dermatan sulfate increased with increasing passage number. We explored the modulation of these biosynthetic activities by the elastin laminin receptor. Using agonists (elastin peptides) and an antagonist (melibiose) of the receptor, their action on GAG biosynthesis was evaluated. Both elastin peptides and melibiose increased incorporation of the tracer in GAGs, but only melibiose inhibited post-synthetic degradation of hyaluronan, therefore increasing its concentration. The effect of passage number on the receptor mediated modulations was also investigated.

Adolescent↗
PubMed1998

Quantification and localization of hyaluronan in a PTFE polymer implanted in the corneal stroma.

The amount and distribution of hyaluronan in a PTFE polymer used to support an artificial cornea implanted in the rabbit cornea were determined. The findings were used to describe the polymer-corneal stroma interface and the reason for the translucence and wettability of this originally opaque and hydrophobic biomaterial. PTFE disks (6 mm in diameter, 0.2 mm thick, 50 microns in pore size) were implanted after a free-hand intralamellar dissection. The corneas were removed 15 days, 1 month, and 3 months after implantation. The hyaluronan content of pepsin-solubilized corneal stromal extracts and its distribution (7 microns cryostat sections) were investigated using an alkaline phosphatase-linked hyaluronectin assay that specifically detects nanogram amounts of hyaluronan. A PTFE polymer implant caused large, transient increases in hyaluronan density in the implanted stroma. The presence of amphiphilic hyaluronan in the polymer 15 days post implantation probably produced translucence and wettability of this opaque, hydrophobic implant despite the absence of cells. The hyaluronan density in the PTFE polymer increased considerably during the first month and then decreased to stabilize at a moderate level by the third month. These changes in hyaluronan density parallel the invasion of the polymer by inflammatory cells during the first month and the subsequent replacement of these cells by fibroblasts. The PTFE polymer is a good interface that is compatible with the native corneal stroma, and our results indicate that hyaluronan, because of its amphiphilic character, plays a major role in the polymer wettability and translucence and in the production of typical corneal extracellular matrix within the pores of the polymer.

Alkaline Phosphatase↗
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↗
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

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

[Hyaluronic acid (hyaluronan) levels in pathological human saphenous veins. Effects of procyanidol oligomers].

We investigated the hyaluronan content in the pathologic human venous wall using an ELSA assay with hyaluronectin according to the method of Delpech et al. The mean hyaluronan content in the 74 fragments from 12 venous walls studied was 596 +/- 528 ng/mg dry weight. These 12 venous walls could be separated in 3 distinct groups according to their hyaluronan content, low (277 +/- 141 ng/mg dry weight), moderate (552 +/- 361 ng/m dry weight) or high (1299 +/- 568 ng/mg dry weight). The differences between these groups are significant (p < 0.001). The presence of a veino-lymphatic oedema was generally associated with a high hyaluronan level (in 65% of cases). The 3H-glucosamine incorporation in cultured venous wall explants showed a 35% increase (p < 0.002) in varicosis as compared with the non or less modified segments of the vein and a 29% (p < 0.001) increase in presence of a veino-lymphatic oedema. The addition of 1 mg/ml of PCO (Procyanidolic Oligomers) to the culture media induced near to 20% decrease of the 3H-glucosamine incorporation and a 34% decrease of the hyaluronan content. Our results confirm the role of local overproduction of hyaluronan in the establishment of oedema and the potential effect of PCO to counteract it.

Age Factors↗
PubMed1997

[2nd generation bio-integrated keratoprosthesis. Implantation in animals].

PURPOSE: Our goal was to evaluate a second generation biointegrable keratoprosthetic device (BioKpro II). METHODS: The device consists of a porous transparent PTFE (12 mm diameter) and a soft copolymer structure for the optical system (7 mm diameter). Intraocular pression was evaluated with a Goldmann tonometer on an artificial chamber. A lamellar dissection was carried out 3 mm radially for 360 degrees creating a pocket to accommodate the skirt. The soft optic (42.5 D; 500 microns thick) was positioned through a hole (6 mm in diameter) trephined in the central cornea. A 360 degrees peritomy was performed and conjunctiva was placed in front of the prosthesis, sutured and was opened 15 days post implantation. 14 rabbits were implanted and were allowed to heal for three months. RESULTS: We are able to measure the intraocular pressure by Goldmann tonometer on an artificial chamber. We did not observed epithelialisation on the hydrophilic optical surface (14/14). Aseptic necrosis in direct contact between cornea and the soft optical system was observed when conjunctiva was not effective (4/14). As observed with the first generation devices, conjunctiva or buccal mucosa is needed to avoid local necrosis. In other cases no adverse reactions were observed after implantation. DISCUSSION: The geometry and biomechanical properties of the BioKpro II is closed to that of the human cornea. The junction between the optical and the flange was bound by polymeric interpenetration and prosthesis dislocation was not seen under pressure over 1000 mmHg. CONCLUSION: Second generation biointegrable keratoprostheses (BioKpro II) can be implanted successfully. Further tests will determine if surface modifications designed to promote epithelial cell attachment on the optical system could prevent ulceration at the junction between the fluorocarbon and the core.

Animals↗
PubMed1996

Collagen synthesized in fluorocarbon polymer implant in the rabbit cornea.

The integration of microporous polymer into tissues is of great interest for the production of keratoprosthetic devices. Our previous studies showed functional differentiated cells and collagen synthesis in the pore of an expanded polytetrafluoroethylene implant. This study identifies and quantifies collagen types synthesized in the implant. Expanded polytetrafluoroethylene polymers were implanted in the rabbit corneas. The collagen extracted from the polymer and implanted stroma after 1, 3 and 6 months was quantified by measuring hydroxyproline. The relative proportions of collagen types were determined by densitometric analysis after SDS-PAGE. The collagen-to-protein ratio in the polymer increased from 0.22 to 0.70 between the first and third month after implantation becoming similar to control cornea. So that of the protein and collagen densities in the polymer and implanted stroma were similar to the control from the third month. The collagen synthesized in the polymer was mainly type I (87%) plus a small amount of type III (8%) 1 month after implantation. The collagen distribution from the third month after implantation was similar to that of the controls and remained constant thereafter in the polymer implant and in the implanted stroma. Immunogold labelling techniques confirmed these results. Implantation of this PTFE disc induced no obvious modification of the corneal stroma, confirming that this polymer is a good interface that is compatible with the native corneal stroma. The keratocytes in this polymer rapidly adopted a corneal phenotype, distinct from the dermal or scaring phenotype as shown by the collagen types produced in the implant.

Animals↗
PubMed1995

[Role of glycosoaminoglycans in venous disease. Mode of action of some flavonoid drugs].

Varicose vein walls differ from normal venous walls by an important loss of their collagen content and an increase of their glycosaminoglycan content, essentially of hyaluronan. The decrease in fibrous protein content can be attributed to increased proteolytic (collagenolytic) activity as well as to free radicals. Glycosaminoglycan increase reflects a disregulation of the normal program of matrix biosynthesis by the cells of varicose vein wall, essentially smooth muscle cells. Some flavonoid drugs are capable of correcting these deviations by decreasing proteolytic attack on fibrous proteins and the accumulation of proteoglycans and hyaluronan. These effects, due to interactions between flavonoid drugs and the cells and fibrous proteins of the venous wall differ according to the nature of such drugs. A hypothesis is proposed to explain these differences in the intensity of action of flavonoid drugs with apparently closely related structures, based on the conformation of these drugs and their interaction with the triple helical structure of collagen fibers as well as with the cell membranes.

Antihypertensive Agents↗
PubMed1993

Na+, K(+)-ATPase and Na+/Ca2+ exchange isoforms: physiological and physiopathological relevance.

Different isoforms of the (Na+ + K+)-ATPase are expressed in different cell types in which they contribute to specialized properties. Their biochemistry and physiology are complex. These isozymes vary in their sensitivity to cardiac glycosides and to intracellular Na+ and Ca2+ concentrations. Their functional expression at the membrane level in the different parts of kidney, heart, and brain varies with species and during ontogenesis. In rat heart, at birth and postpartum, there are quantitative and qualitative changes in the expression of the (Na+ + K+)-ATPase and Na+/Ca2+ exchange isoforms. The (Na+ + K+)-ATPase isozymes react differently to hormonal regulation and to physiopathological alterations, i.e., cardiac ischemia and cardiac hypertrophy. Considering the diversity of the (Na+ + K+)-ATPase isoforms and their numerous regulations, what could be the targets of endogenous (Na+ + K+)-ATPase inhibitors?

Animals↗
PubMed1988

Rat cardiac hypertrophy. Altered sodium-calcium exchange activity in sarcolemmal vesicles.

The sodium-calcium exchange activity has been studied in sarcolemmal vesicles isolated from rat ventricles hypertrophied by pressure overload. 4 weeks after aortic stenosis the degree of hypertrophy varied from 30 to 70%. The Na+-dependent 45Ca2+ influx and efflux were up to 50% decreased and the sensitivity to Ca2+ was 13-fold lower in vesicles from hypertrophied heart as compared to those from normal heart. However, the Na+,K+-ATPase activity, the orientation of the vesicles and the passive Ca2+ permeability were found to be similar in the two heart groups. These results indicate that the sarcolemmal Na+/Ca2+ exchange activity could be qualitatively and/or quantitatively changed in hypertrophied rat heart.

Animals↗
PubMedDate not supplied

Effect of in vitro aging on the modulation of protein and fibronectin biosynthesis by the elastin-laminin receptor in human skin fibroblasts.

The 67-kD elastin-laminin receptor (ELR) subunit which carries the recognition site for elastin peptides (EP) is a lectin. Its binding with galactosides can modulate the kinetics of its interaction with its ligand, EP. In this study the biosynthesis of proteins, collagen and fibronectin were evaluated in the presence of agonists and antagonists of the receptor on human skin fibroblasts. The biosynthesis of total proteins determined by 3H-proline incorporation and of fibronectin (by immunoprecipitation) were shown to increase with passage number. The presence of 1 microg/ml kappa-elastin (EP) in the culture medium increased both total proteins and fibronectin biosynthesis. Melibiose, an agonist of the receptor at 5 microg/ml (140 microM), decreased both proteins and fibronectin biosynthesis in the culture medium of human skin fibroblast at the 10th and 15th passage. These results show that the ELR can control the biosynthetic mechanisms of some of the macromolecular constituents of extracellular matrix such as fibronectin and moderate its age and passage-dependent upregulation.

Cells, Cultured↗