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Biomedical subjects

G Lorans

Publications and source records attributed to G Lorans.

16 recordsLinked to original sources
PubMed1993

[Fibrocyte reaction to interleukin 1 stimulation in keratoconus. Original title: Fibrocyte response to interleukin 1 stimulation in keratoconus].

BACKGROUND: The reduced mechanical strength of the tissues around a keratoconus and the ultrastructural disorganization of its matrix components are caused by proteolytic breakdown and incomplete repair. In most biochemical studies on this subject, reduced collagen content and increased collagenase and gelatinase activity have been reported. METHODS: Since interleukin-1 (IL-1) promotes secretion of prostaglandin E-2 (PG-E2 and collagenase, we were interested in the number of membrane receptors for these cytokines on keratoconus fibroblasts and determined the corresponding dissociation constant (kD). We also studied the kinetics of cyclo-oxygenase and the synthesis of PG-E2, IL-1 and collagen. We compared the data with data from normal human corneas. RESULTS: 1) There was a significant difference (P < 0.05) between the specific binding of [125I]-IL-1 in keratoconic and normal corneal cells. In keratoconus, the number of receptors was four times higher (7000 +/- 100 binding sites per cell) than in normal corneas (1540 +/- 100 binding sites per cell). However, there was little difference between the dissociation constants for keratoconic ([6.21 +/- 0.5] x 10(-11) and normal ([6.27 +/- 0.5] x 10(-11) corneal cells. 2) Under the study conditions, interleukin-1 was found neither in normal nor in keratoconic cornea. 3) Synthesis of PG-E2 without stimulation of cells by IL-1, which was observed in 8 corneas with and 8 without keratoconus, showed that keratoconus cells secrete ten times more PG-E2 than normal corneals cells. If IL-1 is added to the incubation medium, which contains [3H]-labeled arachidonic acid, PG-E2 synthesis increases more than in normal corneal cells. 4) After adding IL-1, the collagen concentration in keratoconus cells in culture was more pronounced than in normal corneal cells. CONCLUSIONS: It is still not known why the anomalies discussed above occur in keratoconus. The increase in IL-1 receptor expression and the high level of cyclooxygenase activity are very probably due to genetic causes, because they are observed even after 40 generations of cell cultures.

Cells, Cultured↗
PubMed1993

Modification of prostaglandin E2 and collagen synthesis in keratoconus fibroblasts, associated with an increase of interleukin 1 alpha receptor number.

Keratoconus, a bilateral corneal disease, is characterized by modifications in corneal shape and thinning of the stroma. It affects young people. From a biochemical point of view, a decrease in collagen content, probably due to the high collagenase activity, has been reported. In these experiments, we have studied the membrane receptors for interleukin 1 alpha, and the corresponding dissociation constant (KD). We also investigated synthesis of prostaglandin E2 (PGE2) and collagen, as well as kinetics of cyclooxygenase. Data from normal human corneas and from keratoconus were compared. Fibroblasts from keratoconus proved to bear four fold more IL1 binding sites than those from normal cornea, with similar KD. Both types of cells synthesize prostaglandin E2, even if IL1 is not added to the medium, but the keratoconus cells produce ten times more than the normal cornea cells. When the cells are stimulated with IL1, synthesis of PGE2 strongly increases and the amounts produced by keratoconus cells are always higher than those of the normal cornea cells. Kinetics of the cyclooxygenase show that Vmax. is 10 times higher in keratoconus than in normal cornea cells; Km's are the same. The amounts of collagen synthesized by keratoconus cells are slightly lower than those of normal cornea cells. Addition of IL1 to the cultures enhances synthesis of collagenase by the cells and decreases collagen found in the culture media. The drop of collagen is more important in keratoconus than in normal cornea cell cultures.

Cells, Cultured↗
PubMed1991

Binding sites for human interleukin 1 alpha, gamma interferon and tumor necrosis factor on cultured fibroblasts of normal cornea and keratoconus.

Keratoconus, a bilateral corneal disease, is characterized by modifications in corneal shape and thinning of the stroma. From a biochemical point of view, a decrease in collagen content, probably due to the high collagenase activity, has been reported. Gamma Interferon (gamma-IFN), Tumor Necrosis Factor (TNF), and Interleukin 1 (IL1) are peptide regulatory factors involved in immunological responses, but they also play a role in the synthesis of collagen and prostaglandin E2 by fibroblasts. In these experiments, we have determined the number of membrane binding sites for gamma-IFN, TNF, and IL1, and the dissociation constant (Kd) for each radiolabelled ligand. All experiments were carried out on cultured corneal stromal cells. Data from normal human corneas and from keratoconus were compared. No differences were found concerning gamma-IFN and TNF binding sites between normal corneas and keratoconus, while fibroblasts from keratoconus proved to bear four fold more IL1 binding sites than normal fibroblasts, with similar Kd.

Adolescent↗
PubMed1990

Effects of acidic and basic fibroblast growth factors on the proliferation of rabbit corneal cells.

Effects of acidic and basic forms of Fibroblast Growth Factor (aFGF, bFGF) on cell proliferation and DNA synthesis were studied in stromal fibroblasts and epithelial cells of rabbit cornea. Both aFGF and bFGF enhance proliferation of sparse cells and trigger DNA synthesis in confluent cultures. Stromal fibroblasts are more sensitive to aFGF than to bFGF in DNA synthesis. No significant difference was seen in the proliferation. Epithelial cells maintained in medium allowing survival are equally sensitive to aFGF and bFGF regardless of the assay used.

Animals↗
PubMed1990

[Secretion of plasminogen activators and their inhibitors in corneal fibroblasts. Modification of this secretion in Schnyder's lens corneal dystrophy].

In this study, we have shown that the secretion of plasminogen activators (PA) by corneal fibroblasts from Schnyder dystrophy is much lower than that secreted by normal corneal fibroblasts. This defective secretion of PA was noted both in the supernatant of cell culture and on the cell surface. This anomaly is found in cultured fibroblasts and therefore is not related to environment modification. Since PA was implicated in remodeling of extracellular matrix, we hypothesized that this anomaly should be responsible for the corneal dystrophy.

Cells, Cultured↗
PubMed1978

Metabolism of proline in a human leukemic lymphoblastoid cell line.

Amino acid analysis of the culture medium was carried out in a human leukemic lymphoblastoid cell line (REH) established from the lymphoblasts of a patient with acute lymphoid leukemia. The results are compared with those of a reference cell line (LHN13) established from normal human lymphocytes. The most striking difference between these two cell lines concerns proline. In LHN13 the concentration of this amino acid in the culture medium increases by 40 microgram/ml/10(6) cells during a 72-hr incubation. In REH there is a decrease under the same culture conditions. In both cell lines proline is derived from glutamic acid and from arginine, as found with the use of 14C-labeled precursors. Synthesis of proline in the REH line represents approximately 26% of the value measured in LHN13 when the precursor is glutamic acid and 15% when the precursor is arginine. The radioisotopic assay for delta1-pyrroline-5-carboxylate reductase showed that there is a deficiency of this enzyme in the REH cells. The defect in proline synthesis of REH was found at the establishment of this line and constitutes a metabolic marker that has persisted for more than 2 years.

Amino Acids↗
PubMed1977

Further purification and chemical characterization of the lymphocyte-inhibiting-factor extracted from thymus (LIFT).

A thymic extract which was previously demonstrated to contain a lymphocyte-inhibiting-factor (LIFT) based on its immunosuppressive activity in vivo and its antiproliferative properties on lymphocytes in vitro, has been purified using ultrafiltration procedures. Most of the activity measured by the ability to inhibit DNA synthesis in short term cultures of mouse thymocytes, was recovered in the 10,000-50,000 m. wt fraction (I fraction). In contrast, similar extracts from non-lymphoid organs were always ineffective in decreasing DNA synthesis in thymocytes. The I fraction was also inhibitory of DNA synthesis in mouse spleen cells stimulated by PHA whatever the time at which the fraction was added after the mitogen stimulation. This fraction, as well as the crude thymic extract, was ineffective in decreasing DNA synthesis in non-lymphoid target cells. The I fraction was further purified by Sephadex G50 filtration and DEAE Sephadex chromatography. The active molecule seemed to be a heat resistant basic peptide probably bound to a ribonucleotide moiety.

Animals↗
PubMed1975

Effect of trimethylcolchicinic acid on the synthesis and excretion of proteoglycans in tissue culture.

The action of trimethylcolchicinic acid on the synthesis and excretion of proteoglycans has been studied on the L cell strain. The incorporation of precursors has been measured, and proteoglycans produced in the culture medium have been extracted and their concentration determined. The mucopolysaccharide components have been studied by electrophoresis. Control cultures produce hyaluronic acid, dermatan sulfate and very low concentrations of chondroitin 4-sulphate or 6-sulphate. Cultures treated with trimethycolchicinic acid (4 mu g/ml) produce hyaluronic acid, very high concentrations of chondroitin 4-sulphate or 6-sulphate and only traces of dermatan sulphate. So, trimethylcolchicinic acid does not modify the synthesis of hyaluronic acid: it considerably increases the production of chondroitin 4-sulphate or 6-sulphate and inhibits the production of dermatan sulphate. Protein fraction of the proteoglycans is proportionally increased in treated cultures, but there is no marked difference between amino acid concentrations of proteoglycans extracted from control and treated cultures. A slight fall in the cystine concentrations was the only change in the amino acid content of proteoglycans extracted from treated cultures. A hypothesis to explain these results is discussed.

Amino Acids↗