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Biomedical subjects

G Lemaire

Publications and source records attributed to G Lemaire.

At least 55 records · Page 3Linked to original sources
PubMed1982

Regulation of plasminogen activator secretion in mouse peritoneal macrophages. II. Inhibition by immunomodulators of bacterial origin.

Two classes of immunomodulators of bacterial origin, peptidoglycan derivatives and lipopolysaccharides, are able to block in vitro the production of plasminogen activator by elicited macrophages: the release of the enzyme into the medium is inhibited and the intracellular activity reduced. In the case of peptidoglycan derivatives, high molecular weight compounds like WSA (water-soluble adjuvant) are stronger inhibitors than small molecules like MPP (muramyl pentapeptide). MDP (muramyl dipeptide) gives partial inhibition only. WSA (at 100 micrograms/ml) completely inhibits plasminogen activator production; the inhibition is reversible and specific. LPS is active at low concentrations (25-100 ng/ml). At concentrations higher than 50-100 ng/ml the action of LPS becomes irreversible and less specific. Peptidoglycan-derived immunomodulators can inhibit plasminogen activator production in the presence of polymixin B or in the case of macrophages obtained from C3H/HeJ mice; LPS is inactive under such conditions.

Adjuvants, Immunologic↗
PubMed1982

Stimulation of several functional properties of macrophages after injection of a suspension of killed Streptococci.

Mouse peritoneal macrophages elicited by injecting i.p. killed group C Streptococci were shown to exhibit several characteristics commonly found in inflammatory macrophages: they secreted high levels of plasminogen activator but had to be stimulated in vitro by LPS to elaborate significant amounts of lymphocyte activating factor (LAF); they contained increased acid hydrolase activities as compared to resident macrophages whereas ecto 5'-nucleotidase was diminished; and they released less arachidonic acid oxygenation products than resident macrophages. However, they also expressed biochemical and functional properties attributed to classically activated macrophages, harvested from immune animals: they displayed reduced levels of alkaline phosphodiesterase; when suitably triggered, they released large quantities of H2O2; and they were strongly cytostatic to syngeneic tumor cells.

Animals↗
PubMed1982

Antitumor activity and hydrogen peroxide release by macrophages elicited by trehalose diesters.

Trehalose diesters (natural 6,6'-trehalose dimycolate from Mycobacterium tuberculosis or synthetic (a 76 carbon atom analogue)), when suspended in water, give stable and well-defined emulsions. These emulsions, injected i.p. in mice significantly limit the growth of P815 syngeneic mastocytoma cells. They elicit macrophages with a cytostatic activity against P815 cells in vitro, strong enough to be expressed at low effector to target ratios (E/T = 1.4) or after a short coincubation period (2 hr). The antitumor potential of these macrophages seems to coincide with their ability to release H2O2 upon pharmacologic triggering. Depressed levels of alkaline phosphodiesterase and beta-galactosidase are proposed as other biochemical markers of cytostatic macrophages.

Animals↗
PubMed1980

[Carcinoma affecting a single kidney. Conservative surgery. One case (author's transl)].

On the basis of a case of partial nephrectomy of a single functioning kidney performed with immediate success in a 77-year-old woman, the author reviews the main data from the literature concerning this particular treatment of carcinoma of the kidney. In the great majority of cases the carcinoma required partial nephrectomy only because the affected kidney was single. Operative mortality was low : 2.6 %. Three year survival is 61 % of cases and it is important to note that terminal renal failure and recurrences in the remaining portion of the kidney are rare. Metastases represent the chief cause of death. Survivals ranging from 6 to 14 years have been reported. When the fact that the kidney is single is not because of nephrectomy for a carcinoma, the prognosis after partial nephrectomy is the same as that after wide excision for carcinoma (in patients with both kidneys). When the opposite kidney had been the site of a carcinoma and even more so in the presence of metastases, the prognosis becomes far less good. With a single kidney, the development of a carcinoma does not necessarily imply the need for total excision of the kidney followed by intermittent haemodialysis. A partial nephrectomy is worth the attempt when it appears to be reasonable. A number of particular technical features are emphasised : - the need for prior arteriography which defines the respective topography of the tumour and the renal vessels, - the safety of temporary clamping of the renal artery when the kidney is made hypothermic by cooling using ice piled up in contact with the kidney, - the possibility of performing such an excision in situ via an appropriate surgical approach.

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↗