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Biomedical subjects

Y Courtois

Publications and source records attributed to Y Courtois.

At least 217 records · Page 12Linked to original sources
PubMed1981

Modulation of the shape of epithelial lens cells in vitro directed by a retinal extract factor. A model of interconversions and the role of actin filaments and fibronectin.

We have shown previously [1] that bovine epithelial lens cells can be stimulated to divide and elongate by a retinal extract (RE). In this report we show that the morphological response to the stimulatory factor is directly related to the target-cell shape, and we describe how the cell shape can be modulated into morphologically different types. If the cells are grown continuously from the explant in the presence of the RE factor, they keep a typical regular pavement-like epithelial shape (type I), even after serial passages. If the same cells are cultured in the absence of the factor, they become extremely irregular in shape and enlarge enormously (type II), and during serial passage elongate spontaneously to a fibroblast-like pattern. However, when type II cells are stimulated by RE, they elongate dramatically into type III cells as described in [1], provided they are stimulated at the optimal cell density. We show that the transformation of one type to another is directly under the control of RE, and we demonstrate that the changes in cell morphology are accompanied by alterations in cytoplasmic actin filaments. Type I cells contain few microfilaments, while type II cells display actin-tropomyosin polygonal fibre networks that reform during conversion to type III cells and then to elongated stress fibres. The change from type I to type II cells is also accompanied by massive accumulation of surface-associated fibronectin. We conclude that factors obtained directly from the eye have a direct ability to control morphology and proliferation of ocular cells like lens cells perhaps by modulation of cellular adhesiveness mediated by surface fibronectin and reorganization of cytoplasmic actin-based filaments.

Actins↗
PubMed1981

Is there a ubiquitous growth factor in the eye? Proliferation induced in different cell types by eye-derived growth factors.

In a previous work [1] we showed that a neutral extract of bovine adult retina RE can stimulate the growth and modify the morphology of bovine epithelial lens (BEL) cells in vitro. We were also able to demonstrate that the differences in cell shape are closely related to the cell growth properties induced by RE and are mediated by cytoskeletal protein organization as well as external proteins. In this study, we report the results of further investigations on this retinal extract. We show that it possesses all the characteristics of other growth factors such as promoting proliferation in low serum concentration or of enhancing the colony-forming efficiency of BEL cells considerably. By comparing the morphological response of BEL cells treated with RE with the response of other cells to other growth factors, we propose that the phenotypic modifications are cell specific, but not growth factor specific. We report also that RE has a broad spectrum of activity since it is able to stimulate cells from different origins and species (vascular and corneal endothelial cells, myoblasts, chondrocytes, neuroblastoma cells, and keratinocytes), but not all of them, since it can be toxic for fibroblasts. In this respect, it has an activity similar in many aspects to FGF and EGF, while it differs from them for some target cells. Its action has also been compared with the effects of retinoic acid derivatives and shown to be strikingly different. RE-like activity can be found in other ocular tissues from bovine and other species. The highest growth-promoting capacities were found in extracts of iris, pigmented epithelium with choroid, and vitreous body. The nature of all these extracts has not yet been determined. Since they are prepared in a similar way and since they have similar growth-promoting activity, we postulate that there is an ubiquitous growth factor in the eye called eye-derived growth factor (EDGF) which may play an important role in physiology and pathology of the eye.

Animals↗
PubMed1980

Cycloheximide effect on DNA degradation and delta-crystallin synthesis in terminally differentiating lens cells.

Low concentrations of a protein synthesis inhibitor, cycloheximide, were added throughout the process of in vitro differentiation of 11-day old embryonic chick lens cells. We found with low concentrations of cycloheximide (0.01 to 0.03 microgram/ml, 3 days of culture), that there was an almost complete delay of DNA degradation as observed on alkaline sucrose gradient. Identical concentrations and exposure time had no blocking effect on increased delta-crystallin synthesis as detected by immunoprecipitation and electrophoresis. Higher concentrations of cycloheximide (0.1 to 1 microgram/ml) showed a marked effect on DNA size and a net inhibition on delta-crystallin synthesis. Thus a selective effect of low doses of cycloheximide was observed on terminal differentiation suggesting that there was not a relationship between DNA degradation and delta-crystallin synthesis in these short term experiments. The investigations of minor proteins could be of interest as they may have a crucial role in intact nuclei cataracts.

Animals↗
PubMed1980

[Growth factors and cell cultures: a new approach for research in ophthalmology].

Tissue culture technology applied to ophtalmology has produced an extensive knowledge of ocular cell physiology. In this work, we review the various factors known to control proliferation and differentiation in lens epithelial cells and corneal endothelial cells. We discuss the role of a new ocular growth factor that we discovered in the retina and whose ubiquitous distribution suggests that it could be involved in tissue-tissue interactions.

Animals↗
PubMed1979

DNA repair in lens cells during chick embryo development.

When chick lens epithelium is cultured in vitro, differentiation into lens fiber cells is accompanied by DNA degradation. This phenomenom of terminal differentiation was studied in the epithelium from embryos at the 6th and 11th days of development. DNA size and the ability of the cells to repair DNA damage induced by X-rays were analysed in alkaline sucrose gradients. In the 6-day epithelium a rapid degradation and complete lack of DNA repair were recorded. Similar observations have been made in previous studies on the 11-day sample, but here degradation is progressive and occurs after a lag of several days. In the younger epithelium, internal irradiation by [3H]thymidine also had a drastic effect resembling that caused by X-rays. In order to assess the process of differentiation in our experimental system the synthesis of delta- and alpha-crystallins was monitored. Stage-related modifications in the rates of synthesis were recorded. The results confirm that the DNA repair system is impaired during terminal differentiation. The differences observed between the two stages may reflect either a developmental modification in DNA repair mechanisms or a change in the relative proportions of differentiating cells. An hypothesis is proposed in support of the latter case.

Age Factors↗
PubMed1979

Histones biosynthesis and turnover in epithelial lens cells cultured in vitro.

"Histone synthesis was compared in epithelial lens cells during exponential growth and in the stationary phase brought by contact inhibition. Double labelling experiments with 3H-lysine and 14C-lysine show a net turnover of histone H1 independent of DNA replication. The nucleosome core histones seem to turn over also, but much more slowly than H1".

Animals↗
PubMed1978

Spontaneous transformation of bovine lens epithelial cells: kinetic analysis and differentiation in monolayers and in nude mice.

Bovine lens epithelial cells, in vivo, are known to perform two determined functions. First, they synthesize the lens capsule and subsequently, in the germinal region, they differentiate in fiber cells with massive production of crystallin proteins, inactivation and pyknosis of the nucleus. Bovine lens epithelial cells from adult origin can be cultured but so far no massive crystallin production has been demonstrated in vitro. We have studied the growth and differentiation of these cells and shown that in long term culture they acquire spontaneously many characteristics of transformation: unlimited growth potential, abnormal karyotype, multilayering. Viral particles were scarcely detected. However, they retain their epithelioid character and the ability to synthesize lens capsule material. Kinetic characteristics of those cells have been determined. When injected into nude mice, they actively proliferate and form tumors in which synthesis of alpha-crystallin can be demonstrated. These results show that in vitro transformation of lens epithelial cells does not affect their potential for terminal differentiation.

Animals↗
PubMed1978

The repair of DNA single strand breaks in human cells with genetical disorders.

The aim of this work was to make a preliminary examination of some hereditary diseases, related to precocious aging in order to determine whether the defects involved resulted from an impairment of the DNA repair capacity. To test for an impairment in DNA single strand capacity, in cells from patients with different diseases, we have followed the rate of the DNA after X-irradiation by sedimentation on alkaline sucrose gradients. It was found that all cells observed from Lesh Nyhan, cystic fibrosis, trisomy 15 et 21, retinoblastoma, were able to repair the single strand breaks in their DNA to the same extent and at the same initial rate.

Adult↗
PubMed1977

Action of ultrasonic irradiation on the DNA of cultivated bovine epithelial lens cell.

Cultivated epithelial lens cells have been submitted to a 20 kHz continuous ultrasonic irradiation. At relativity high intensity, destruction of the cells was observed. At lower intensities, where no cell destruction appeared, the molecular weight of the single strand DNA of these cells was monitored to determine whether breakage of DNA molecules was induced by the ultrasound. No breakage of the single strand DNA was observed for intensities below 0.1 and 0.4 W cm-2 with irradiation times of less than 20 minutes and 15 seconds, respectively. These intensities and their corresponding irradiation time are higher than those used in current diagnostic practice.

Animals↗