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Biomedical subjects

Y Courtois

Publications and source records attributed to Y Courtois.

At least 163 records · Page 9Linked to original sources
PubMed1988

Acidic fibroblast growth factor stimulates opsin levels in retinal photoreceptor cells in vitro.

It is demonstrated that newborn rat retinal photoreceptor cells can differentiate in monolayer culture, and synthesize de novo photoreceptor-specific proteins such as opsin. When maintained in serum supplemented medium on a laminin substrate, these cells survive for up to 3 weeks. The addition of acidic fibroblast growth factor stimulates an increase in the levels of opsin of 5-10-fold control values, and prolongs cell survival by up to 6 days.

Animals↗
PubMed1988

Influence of fibroblast growth factor on phosphorylation and activity of a 34 kDa lipocortin-like protein in bovine epithelial lens cells.

We examined the effect of basic fibroblast growth factor (FGF) on phosphorylation and lipocortin-like activity of the 34 kDa protein present in the basal membrane of epithelial peripheral cells which initiate growth and differentiation in the bovine lens. We found that: (i) the 34 kDa protein possesses anti-phospholipase A2 (PLA2) activity of lipocortin; (ii) in response to FGF, the anti-PLA2 activity of this protein is enhanced whereas its phosphorylation is markedly decreased. It is suggested that the 34 kDa protein might represent an important biological activity in controlling FGF induction of growth and differentiation in the adult eye lens.

Animals↗
PubMed1988

Regulation of eye derived growth factor binding to membranes by light, ATP or GTP in photoreceptor outer segments.

Eye derived growth factor II (EDGF II), the retinal form of acidic fibroblast growth factor (aFGF) is present in rod outer segments (ROS) purified in the dark, which display higher EDGF specific activity than all other parts of the retina. EDGF binds to ROS disc membranes upon illumination. This binding is not reversible in the dark. ATP, but not GTP, readily releases EDGF from either dark-adapted or previously bleached ROS. The release of EDGF activity from ROS membranes would require a phosphorylation mechanism since AMP-PNP, an ATP analogue, is not efficient. ROS membranes compete with cellular EDGF receptors of retinal pigment epithelial cells in vitro for the binding of labelled EDGF II, suggesting that they also possess specific binding sites. These data suggest that EDGF II is involved in photoreceptor cell biology.

Adenosine Triphosphate↗
PubMed1988

Specific binding of basic fibroblast growth factor to basement membrane-like structures and to purified heparan sulfate proteoglycan of the EHS tumor.

The binding of iodinated basic fibroblast growth factor (bFGF) to low-density heparan sulfate proteoglycan purified from the Engelbreth Holm Swarm (EHS) sarcoma was investigated using different techniques. The tumor clearly contained bFGF, the level being comparable to that found in other tissues such as human or bovine brain. 125I bFGF strongly bound to the basement membrane-like matrix of EHS frozen sections as revealed by autoradiography. Iodinated bFGF bound to purified heparan sulfate proteoglycan but not to laminin or collagen type IV, three components isolated from the same tumor. In contrast, acidic fibroblast growth factor (aFGF) displayed negligible binding to heparan sulfate proteoglycan. Binding of bFGF to frozen sections and to purified proteoglycan could be strongly inhibited by heparin and was displaced by an excess of unlabeled factor and completely suppressed after heparitinase and heparinase treatments. Binding was a function of the salt concentration and was abolished at 0.6 M NaCl. Scatchard analysis indicated the affinity site had a Kd of about 30 nM, a value 10-15 higher than that recently reported by Moscatelli (J. Cell. Physiol., 131:123-130, 1987) in the case of the low-affinity binding sites present on the surface of baby hamster kidney (BHK) cells.

Animals↗
PubMed1988

Immunochemical analysis of extracellular matrix during embryonic lens development of the Cat Fraser mouse.

We have characterized the extracellular matrix present during early mouse-lens morphogenesis in Swiss and Cat Fraser mutant mice which produces a thicker capsule. In the two mouse strains, laminin was first detected when the optic vesicle and the head ectoderm are closely associated. At day 10, staining for laminin and fibronectin is especially concentrated at the border of the lens pit. At this stage, type IV collagen and proteoheparan sulphate have a similar distribution to laminin and fibronectin. In the two mouse strains, no major differences were observed in the intensity and the distribution of fluorescent basement-membrane components. This suggests that the overall increase in capsule thickness of the Cat Fraser mutant is more related to an increased cellular synthesis of capsule than to an abnormal distribution of one or more basement-membrane macromolecules.

Animals↗
PubMed1988

Variation in the relative abundance of gamma-crystallin gene transcripts during development and ageing.

The transcripts of gamma-crystallin mRNA were examined during adulthood. The mRNA transcripts were detected by Northern blot technique. Although the total RNA per lens measured remains constant during adulthood, the mRNA transcript size was observed to decline with ageing, specifically for the gamma-crystallin and not for alpha- and beta-crystallins. We could show that the relative amount of mRNA transcripts detected with the four probes decreased with ageing, with gamma 1 and gamma 2 transcripts being found at a higher level than the gamma 3 and gamma 4 transcripts.

Aging↗
PubMed1987

Characterization of acidic and basic fibroblast growth factors in brain, retina and vitreous chick embryo.

We have purified acidic and basic fibroblast growth factors (c-aFGF, c-bFGF) from 11 day-old chick embryo brain, retina and vitreous by heparin-Sepharose chromatography and reverse phase HPLC. The analysis of their biological activity as well as their molecular weight indicates that they were analogous to basic or acidic human and bovine FGF. The ratio of c-aFGF to c-bFGF activity depended of the tissue. In brain c-aFGF represented 66% of the total mitogenic activity retained on the heparin-sepharose column and c-bFGF 34% while retina contained 16% of c-aFGF and 84% of c-bFGF; vitreous 78% of c-aFGF and 22% of c-bFGF. Like human aFGF, Heparin stimulated purified c-aFGF mitogenic activity in the absence of serum but inhibited the activity of the retina acid soluble extract, in the presence of foetal calf serum (FCS). Thus, chick embryo and adult human acidic and basic FGF respectively share the same biochemical properties. Since there are no blood vessels in chick retina or vitreous, their presence in these tissues suggests that angiogenesis is not the only role of these growth factors.

Animals↗
PubMed1987

Collagen synthesis by long-lived mRNA in embryonic chicken lens.

Lens capsule collagen synthesis by epithelial and fiber cells was examined by immunoprecipitation and collagenase digestion in embryonic and posthatch chicken eye lens. Epithelial cells and lens fibers in the process of terminal differentiation produce alpha 1 and alpha 2 type IV collagen chains. At 6 days of embryonic development in addition to the alpha 1 (IV) and alpha 2 (IV) collagen chains, lens cells produce high molecular weight collagenase-sensitive proteins not immunologically related to type IV collagen. Lens capsule collagen components have been identified in central and outer fibers isolated from 18-day embryos and from 10-day posthatch chicken eyes. At these stages, fibers which have an increasing number of picnotic nuclei still show collagen synthesis due to long-lived mRNA. Analysis of collagen synthesis by lens cells incubated with actinomycin D suggests that stabilization of collagen mRNA occurs in lens fiber cells and to a lesser extent in epithelial cells as early as 6 days of embryonic development.

Age Factors↗
PubMed1987

Specific fixation of bovine brain and retinal acidic and basic fibroblast growth factors to mouse embryonic eye basement membranes.

The labeling pattern of mouse embryonic eye frozen sections incubated with radioiodinated brain acidic and basic fibroblasts growth factors (aFGF and bFGF) was investigated by autoradiography. Both growth factors bind to basement membranes in a dose-dependent way, with a higher affinity for bFGF. Similar data were obtained with eye-derived growth factors (EDGF), the retinal forms of FGF. There was a heterogeneity in the affinity of the various basement membranes toward these growth factors. The inner limiting membrane of the retina and the posterior part of the lens capsule have a higher binding capacity than the posterior part of the Bruch's membrane. The specificity of the growth factor-basement membrane interaction was demonstrated by the following experiments: (i) an excess of unlabeled growth factor displaced the labeling; (ii) unrelated proteins with different isoelectric points--gelatin, serum albumin, histones--did not modify the labeling; and (iii) iodinated EGF or PDGF did not label basement membrane. In order to get a better understanding of the nature of this binding, we performed the incubation of the frozen sections with iodinated FGFs preincubated with various compounds: (i) heparin which is known to have a strong affinity for aFGF and bFGF partially decreases the labeling, and (ii) chondroitin sulfate B and dextran sulfate at high concentrations were also partially effective. In addition, enzymatic treatment of the sections reveals that only heparitinase, not collagenase or chondroitinase ABC, completely prevents the labeling without destroying the overall structure of the basement membrane. An antibody against the proteic part of EHS mouse proteoheparan sulfate does not affect the signal. Esterification of the acidic groups cancelled the binding. These results demonstrate that FGFs bind specifically to basement membranes, probably on the polysaccharidic part of the proteoheparan sulfate, and suggest that this type of interaction may be a general feature of the mechanism of action of these growth factors.

Animals↗
PubMed1987

Effect of X-irradiation and vitamin C on DNA degradation and endogenous DNase in embryonic chick lens cells.

The lens is an organ in which epithelial cells become elongated fibers. During this process, nuclei are transformed and the DNA is degraded. In previous studies, we described an autodigestion of the chromatin in isolated fiber nuclei but not in epithelial nuclei, but the level of DNAase activity was found to be identical in both epithelial and fiber nuclei of lenses at 11 days of development. In this study, we have investigated the possibility that x-irradiation might stimulate the nuclear endogenous activity responsible for chromatin breakdown or epithelial cells to a level comparable to that observed in fiber cells. We have observed that x-irradiation does not increase the nuclear epithelial DNAase activity. Conversely, vitamin C, suspected to prevent cataract formation by protecting DNA against free radical formation, has a damaging effect on the DNA of the lens of chick embryo in vitro.

Animals↗
PubMed1986

Structure activity relationship in heparin: stimulation of non-vascular cells by a synthetic heparin pentasaccharide in cooperation with human acidic fibroblast growth factors.

Heparin enhances strongly the mitogenic properties of human acidic fibroblast growth factor (h-aFGF) on hamster fibroblast (CCL 39) or bovine lens epithelial cells (BEL). We report here that a synthetic heparin pentasaccharide with high affinity for antithrombin III has the same effect as heparin at about the same concentration. Thus a pentasaccharidic sequence may represent the shortest heparin structure which interacts with h-aFGF.

Animals↗
PubMed1986

Isolation of heparin-binding growth factors from dogfish (Mustela canis) brain and retina.

We have purified two growth factors from dogfish brain and retina by using their binding affinity for heparin-Sepharose. These growth factors were eluted at 1 and 2 M NaCl similarly to those purified from bovine brain or retina. Their mitogenic activity was assayed in vitro on the same mammalian cells: bovine lens epithelial cells or human fibroblasts. All these data seem to indicate that these growth factors belong to the families of other well defined mammalian growth factors: EDGF I, brain basic FGF, AGF II, on the one hand and EDGF II, brain acidic FGF, AGF I, ECGF, on the other. Thus, these growth factors have been widely distributed during evolution and retain at least a conservative sequence to stimulate cell proliferation, in mammalian cells.

Animals↗
PubMed1986

Effect of heparin on the stimulation of non-vascular cells by human acidic and basic FGF.

We have purified acidic and basic fibroblast growth factors from human brain (h-aFGF, h-bFGF) and studied the effect of heparin on the growth stimulation by these factors of hamster fibroblast CC139 cells and bovine epithelial lens (BEL) cells. In both the presence and the absence of foetal calf serum (FCS) heparin cooperates with h-aFGF in a dose dependent manner to stimulate both types of cells. The cooperation with h-bFGF is much less. An unpurified human brain fraction containing both factors behaves differently: in the absence of FCS, heparin enhances the activity of the crude fraction on BEL cells, while in the presence of FCS, it decreases this activity. These results indicate that heparin cooperates strongly with h-aFGF to stimulate non-vascular cell proliferation while in a partially purified extract and in the presence of serum it can induce the opposite effect.

Animals↗
PubMed1986

Evidence for FGF-like growth factor in adult bovine retina: analogies with EDGF I.

Eye Derived Growth Factor (EDGF) is the genus name for growth factor activities found in several ocular tissues. Purification from bovine retina by Cibacron blue affinity chromatography has previously given a fraction which can induce target cell proliferation at doses of 30 ng per ml of culture medium. Radioimmunoassay using a labelled synthetic decapeptide [Tyr 10]--FGF (1-10) including the 9 N terminal amino acids of brain Fibroblast Growth Factor (FGF) indicated that EDGF contained a FGF-like material. Further purification of Cibacron blue purified EDGF with heparin sepharose chromatography yielded two active fractions after elution with a sodium chloride gradient. One fraction named EDGF I eluted between 1.3 and 1.5 M NaCl and accounted for over 50% of the input biological activity and comigrated with purified FGF on SDS PAGE at a molecular weight of 16,000 d as a single band. FGF competed with EDGF I for binding to specific receptors on bovine epithelial lens cells. We conclude that retina contains a growth factor activity (EDGF I) similar if not identical to FGF.

Animals↗
PubMed1986

Nuclear endogenous Ca2+-dependent endodeoxyribonuclease in differentiating chick embryonic lens fibers.

During terminal differentiation of lens epithelial cells into fiber cells, nuclei become pycnotic and DNA degradation occurs. We investigated the putative role in this process of an endogenous DNAase. After incubation of isolated nuclei of both cell types at 37 degrees C, DNAase activity was revealed by DNA size analysis on 0.3-1% neutral and alkaline agarose, one- and two-dimensional gels. This DNAase activity is more prominent in lens fiber nuclei than in epithelial nuclei at all the embryonic stages probably because of a preexisting higher concentration of divalent cations in the former. This activity is calcium or magnesium dependent in both types of nuclei.

Animals↗
PubMed1986

Chromatin condensation and terminal differentiation process in embryonic chicken lens in vivo and in vitro.

During embryonic chick lens differentiation, the epithelial cells become transformed into elongated fibres. Concomitantly, the fibre nuclei undergo degeneration and high molecular weight (HMW) DNA breaks down due to nuclear endodeoxyribonuclease activity. An electronmicroscopic study of lens epithelial and fibre nuclei was made at different stages of chick embryonic development, both in vivo and in vitro. The in vitro conditions are conducive to the expression of endogenous endodeoxyribonuclease activity in fibres. In both conditions we observed condensation of chromatin. The organization of some nuclear material into distinct linear arrays followed by streaming of nuclear material into the cytoplasm is recorded only in vitro. Such a condition may lead to acceleration of the process of aging in lens fibres.

Animals↗
PubMed1986

Eye-derived growth factor isolated from bovine retina and used for epidermal wound healing in vivo.

Eye-derived growth factor (EDGF) has been found in several ocular tissues and shown to be able to stimulate the in vitro proliferation of cells from various tissues and organisms. It had already been shown that EDGF differs biochemically and biologically from other growth factors such as epidermal growth factor (EGF) and fibroblast growth factor in that it is the only one that can stimulate the in vitro growth of human adult keratinocytes. Moreover EDGF stimulates reepithelialization and neovascularization. In this paper we report data concerning the effect on the rate of epidermal wound healing in guinea pigs of different extracts obtained from adult bovine retina. Our results show that EDGF can significantly increase the rate of reepithelialization when epidermis is detached from dermis and removed after induction of a blister. The doses used were comparable to the ones used to obtain maximal increase of cell proliferation in vitro. However no attempt was made to further investigate the mechanism accounting for the observed wound healing. At 24 h, control wounds maintained under occlusive dressing had only about 50% of their surface covered with cells as opposed to EDGF-treated wounds which were covered up to about 80% (p = 0.05). On the other hand, EGF does not increase the rate of wound healing in this model even at 1000-fold higher doses than those used in in vitro bioassays. Although EDGF is still not purified to homogeneity and another 10- to 100-fold purification might be necessary to achieve homogeneity, our results suggest that EDGF may find therapeutic applications as a potent in vivo epidermal wound healing agent.

Animals↗