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Biomedical subjects

G Lemaire

Publications and source records attributed to G Lemaire.

At least 19 recordsLinked to original sources
PubMed1992

Low response of BALB/c macrophages to priming and activating signals.

Trehalose dimycolate (TDM), a mycobacterial glycolipid, is a powerful macrophage-priming agent. However, its efficiency seems limited in the case of BALB/c mice. Peritoneal macrophages harvested from TDM-treated BALB/c mice did not control BCG growth in vitro as efficiently as similar macrophages from two other mouse strains, (B6 x D2)F1 and C57BL/6, which are respectively Bcgr and Bcgs. BALB/c macrophages elicited by TDM also exhibited a low capacity to produce hydrogen peroxide and, after activation by lipopolysaccharide (LPS), weak cytostatic activity against P815 mastocytoma cells. Finally, alkaline phosphodiesterase, a marker of resident and inflammatory macrophages, was still expressed at a high level in macrophages of BALB/c mice treated with TDM. Low responsiveness of BALB/c macrophages to stimuli was not observed with TDM only; activation for tumor cytotoxicity of thioglycolate-elicited macrophages from BALB/c mice required also higher doses of interferon-gamma, and LPS. L-Arginine-dependent production of nitric oxide was inducible in macrophages from BALB/c mice, but the conditions required for its induction were more stringent. Thus, the reduced antiproliferative effects of BALB/c macrophages may be due to uncomplete induction of NO synthase after suboptimal stimulation.

Amino Acid Oxidoreductases↗
PubMed1991

Stimulation of antimycobacterial activity in mouse peritoneal macrophages by priming with trehalose dimycolate (TDM).

We examined the potential of two bacterial immunomodulators, trehalose dimycolate (TDM) and lipopolysaccharide (LPS), to stimulate the capacity of mouse peritoneal macrophages to control the growth of the intracellular bacterium, Mycobacterium tuberculosis BCG. Macrophages were obtained from mice innately susceptible (Bcgs) or resistant (Bcgr) to BCG infection. In all mouse strains tested (Bcgr and Bcgs), with the exception of BALB/c (Bcgs), TDM was sufficient to elicit macrophages with strong antimycobacterial activity in vitro. In BALB/c mice, the induction of anti-BCG activity required two signals, TDM and LPS, given in sequence. Our data suggest that additional gene(s), besides the Bcg locus, control macrophage resistance to BCG.

Animals↗
PubMed1990

Alterations of ribonucleotide reductase activity following induction of the nitrite-generating pathway in adenocarcinoma cells.

The murine adenocarcinoma cell line TA 3 synthesized nitrite from L-arginine upon stimulation with gamma-interferon (IFN-gamma) associated with tumor necrosis factor (TNF), and/or bacterial lipopolysaccharide (LPS), but not with IFN-gamma, TNF, or LPS added separately. Induction of the NO2(-)-generating activity caused an inhibition of DNA synthesis in TA 3 cells. This inhibition was prevented by the L-arginine analog N omega-nitro-L-arginine, which inhibited under the same conditions nitrite production by TA 3 cells. The TA 3 M2 subclone, selected for enhanced ribonucleotide reductase activity, was found to be less sensitive than the wild phenotype TA 3 WT to the cytostatic activity mediated by the NO2(-)-generating system. Cytosolic preparations from TA 3 M2 cells treated for 24 or 48 h with IFN-gamma, TNF, and LPS exhibited a reduced ribonucleotide reductase activity, compared to untreated control cells. No reduction in ribonucleotide reductase activity was observed when N omega-nitro-L-arginine was added to treated cells. Addition of L-arginine, NADPH, and tetrahydrobiopterin into cytosolic extracts from 24-h treated TA 3 M2 cells triggered the synthesis of metabolic products from the NO2(-)-generating pathway. This resulted in a dramatic inhibition of the residual ribonucleotide reductase activity present in the extracts. The inhibition was reversed by NG-monomethyl-L-arginine, another specific inhibitor of the NO2(-)-generating activity. No L-arginine-dependent inhibition of ribonucleotide reductase activity was observed using extracts from untreated cells that did not express NO2(-)-generating activity. These results demonstrate that, in an acellular preparation, molecules derived from the NO2(-)-generating pathway exert an inhibitory effect on the ribonucleotide reductase enzyme. This negative action might explain the inhibition of DNA synthesis induced in adenocarcinoma cells by the NO2(-)-generating pathway.

Adenocarcinoma↗
PubMed1979

Regulation of plasminogen activator secretion in mouse peritoneal macrophages. I. - Role of serum studied by a new spectrophotometric assay for plasminogen activators.

A chromogenic tripeptide - H-D-Val-Leu-Lys-p-nitroanilide-substrate of plasmin, can be used to follow plasminogen activation by an activator such as urokinase or the activator secreted by mouse peritoneal macrophages (thioglycolate-elicited). The acceleration of p-nitroaniline production is proportional to the initial rate of plasmin formation from plasminogen. Thus, at a given plasminogen concentration, this acceleration is proportional to the activator concentration. The acceleration can be evaluated from the spectrophotometer trace recording at 405 nm the appearance of p-nitroaniline, either by means of a computer program or by a plot of delta A405 vs.t2. The sensitivity of this assay allows detection of 0.003 CTA units of urokinase. Thioglycollate-elicited mouse peritoneal macrophages secrete plasminogen activator into the extracellular medium during in vitro cultivation only after a contact with serum.

Animals↗
PubMed1976

Limited proteolysis of tryptophanyl-tRNA synthetase from beef pancreas.

Treatment of purified tryptophanyl-tRNA synthetase with either chymotrypsin, papain, subtilisin or elastase converts all the enzyme into a high-molecular-weight intermediate. This protease-resistant core molecule has the same dimeric structure as the native protein and possesses the ability to bind substrates (tryptophan, ATP and tRNATrp) but is catalytically inactive. The monomer molecular weight of the protease-treated enzyme is 39000 compared to 54000 for the intact molecule. Chemical studies indicate that proteases excise the amino-terminal part of the polypeptide chain. It has been demonstrated previously that removal of a 13000-dalton fragment from the amino-terminal region of the tryptophanyl-tRNA synthetase converts the native enzyme to another active form. Cleavage of 20 additional amino acids produces the inactive protease-resistant core.

Amino Acids↗
PubMed1975

Multiple forms of tryptophanyl-tRNA synthetase from beef pancreas.

Three different forms of tryptophanyl-tRNA synthetase can be isolated from pancreatic extracts. Structural, immunological and catalytic properties of these various forms have been compared. The native enzyme is a dimeric molecule of molecular weight 108000. Two other forms, of molecular weight 85000 and 82000, are composed of two polypeptide chains identical with the carboxyl terminal region of the native subunits. These molecules are supposed to derive from the original protein by removal, from the amino-terminal part of each subunit, of a fragment of 11000 to 13000 molecular weight. Such removal modifies the shape and the stability of the molecule and decreases its specific acitvity. The origin of the derived forms is attributed to proteolysis. In fact, limited proteolysis of purified tryptophanyl-tRNA synthetase, in its native form, by elastase, results in the formation of an active compound, similar to one of the tryptophanyl-tRNA synthetase derived forms. Furthermore, incubation with "elastolytic fractions" prepared from pancreatic extracts presenting a particularly high level of proteolytic activity produces the same cleavage in tryptophanyl-tRNA synthetase polypeptide chain.

Amino Acids↗