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Biomedical subjects

M Veron

Publications and source records attributed to M Veron.

At least 73 records · Page 4Linked to original sources
PubMed1984

Impaired resistance to Listeria monocytogenes in mice chronically exposed to cadmium.

It is shown in this work that resistance to Listeria monocytogenes is greatly impaired in C57BL/6 mice chronically exposed to cadmium (Cd) chloride. Animals received 0.5 mg/kg Cd by an intraperitoneal route three times a week during a 4-week period and were then infected with L. monocytogenes. Susceptibility to this pathogenic bacteria was not due to a defect of the specific immune response, since mice developed normal levels of anti-Listeria T cell-mediated immunity and did not show any impairment of macrophage activation. In fact, bacterial growth in organs was rapid in Cd-exposed mice during the early phase of infection, suggesting an impairment of non-specific defence mechanisms. Experimental data indicate that the susceptibility to L. monocytogenes might be due to a defect of macrophage recruitment in sites of infection during the early phase of the host response.

Animals↗
PubMed1983

Evidence that a cAMP binding protein from Dictyostelium discoideum carries S-adenosyl-L-homocysteine hydrolase activity.

A cAMP-adenosine binding protein partially purified from exponentially growing Dictyostelium discoideum cells carries S-adenosyl-L-homocysteine (SAH) hydrolase activity. This protein is present throughout the developmental cycle and has many properties in common with a cAMP binding activity previously reported from this laboratory (Gunzburg and Véron, 1981). Direct binding measurements with radioactive ligands indicate a dissociation constant of 0.2 microM for adenosine and 9 nM for cAMP, a value in good agreement with measurements of the rate constants for cAMP binding (k+1 = 2.4 X 10(4) M-1 sec-1) and dissociation (k-1 = 1.1 X 10(-4) sec-1). The binding of cAMP is completely abolished in the presence of 1 microM adenosine; a maximum 60 per cent inhibition of adenosine binding can be achieved with cAMP concentrations as high as 0.1 microM, suggesting that at least some of the cAMP and adenosine binding sites are not identical. The protein has a sedimentation coefficient of 9.2S and a native molecular weight of 190,000, as judged by gel filtration. Labeling with the photoaffinity ligand 8-azido-[3H]-cAMP followed by SDS polyacrylamide gel electrophoresis results in a single band of 47,000 MW, suggesting that the protein may be a tetramer. The physiological importance of the protein and its association with SAH hydrolase activity is discussed in relation to a possible role in the regulation of protein and phospholipid methylation that occurs during chemotaxis.

Adenosine↗
PubMed1983

[In vitro effect of rosoxacin on hospital bacteria. Results of a multicenter study].

This work reports a multicenter study of antibacterial activity of rosoxacin, a new antibacterial agent of the quinolone group. Enterobacteriaceae are very sensitive to rosoxacin (modal MIC 0,5 micrograms/ml); resistant strains are observed in all species, but more often among Serratia and Citrobacter. Pseudomonas aeruginosa is less sensitive with a maximum number of strains between 2 and 8 micrograms/ml, so it is nearly for Acinetobacter. Haemophilus are very sensitive, having MIC of 0,03 and 0,06 micrograms/ml. The spectrum of rosoxacin includes Gram positive bacteria, since the MIC of Staphylococci are similar to Enterobacteriaceae; Enterococci are less sensitive, the major part of the strains being inhibited by 4 and 8 micrograms/ml.

4-Quinolones↗
PubMed1982

A cAMP-dependent protein kinase is present in differentiating Dictyostelium discoideum cells.

We demonstrate the occurrence of a cAMP-dependent protein kinase in Dictyostelium discoideum cells at the terminal stage of differentiation. A cAMP-binding component was purified to homogeneity by affinity chromatography. This subunit inhibits the activity of purified catalytic subunit from beef heart protein kinase; the inhibition is reversed upon addition of cAMP. The protein is highly specific for cAMP and has a dissociation constant of 4 nM. The isolated regulatory subunit is a monomer of 39 K, with a sedimentation coefficient of 3.5S and a frictional coefficient of 1.24. The differences between this regulatory subunit and regulatory subunits of protein kinases from other sources are discussed.

Journal Article↗
PubMed1982

[Activity of amoxicillin and ampicillin against infection with Salmonella typhimurium in mice ].

Experimental mouse intraperitoneal or intragastric infection due to Salmonella typhimurium C5 was treated with subcutaneous amoxicillin or ampicillin. The minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) of the two penicillins were similar. Amoxicillin was significantly more effective than ampicillin in protecting the animals from the lethal effects of the infection. The enumeration of bacteria from spleen and Peyer's patches of the small intestine showed that amoxicillin killed S. typhimurium faster than ampicillin.

Amoxicillin↗
PubMed1982

[Phenotypes and epidemiological markers of Salmonella typhimurium].

Salmonella typhimurium is the most often encountered serotype. The need for numerous epidemiological markers seems particularly obvious. The purpose of this study was to extend the biotyping patterns previously published and usually restricted to some biochemical characters. 192 strains of S. typhimurium, selected as representative of 6 continental French regions and 4 ecological sources, were studied by means of 203 tests, including the assimilation of 147 carbon substrates. An analysis of the results showed that 52 biochemical or nutritional tests could be used as markers during the survey of an epidemic. In addition, 18 of these tests permitted to delineate three polythetic phenons, in which the ecological origin of strains was statistically different. The identification of these phenotypes, before testing markers, could be a useful first step for the investigation of studied strains.

France↗
PubMed1982

[Epidemiological significance, clinico-morphological evaluation and behavior of pathogenetic factors, in asymptomatic chronic carriers of the HBsAg in the La Plata area. Study in voluntary blood donors].

Seric positivity for HBsAg (CIED) investigated on 100.000 volunteer blood donors of La Plata city was 0.239%. Humoral findings on 40 cases only revealed TGO-TGP seric levels over twice the normal in 15 and 10% respectively. On 27 biopsied patients, chronic active hepatitis in one case and chronic persistent hepatitis in another one were found. Non-specific chronic inflammatory changes were seen in 18.5%. Correlation between TGO-TGP levels and histologic damage was generally proved. HBeAg seric positivity in 3/29 cases (10.3%) was accompanied of both raised TGO-TGP levels and some kind of chronic inflammatory change. Statistic high risk was determined for both O-Rh negative blood group and HLA-Bw21 individuals. Diminished cutaneous PPD reactivity without significative alteration of linfocite population was established.

Adult↗
PubMed1981

Intracellular adenosine 3',5'-phosphate binding proteins in Dictyostelium discoideum: partial purification and characterization in aggregation competent cells.

Three adenosine 3',5'-phosphate (cAMP) binding proteins were separated and partially purified from cytoplasmic extracts of Dictyostelium discoideum cells developed to aggregation competence. Two species, A and B, representing respectively 50% and 20% of the total activity, bind cAMP with very rapid kinetics and high specificity. Species A (Kd = 7.5 nM) is a monomeric protein of 36 000 daltons with a sedimentation coefficient of 2.3 S. Species B, which binds cAMP with positive cooperativity, also displays a high affinity for the ligand (Kd = 3.2 nM). This protein is present in the extracts as an equilibrium between monomeric, dimeric, and tetrameric forms with respective sedimentation coefficients of 2.4, 4.5, and 6.5 S; binding of cAMP to the monomer induces the appearance of the multimeric forms. A third cAMP binding protein (species C, Kd - 9.5 nM) was characterized as a larger protein (Mr 190 000, sedimentation coefficient of 9.2 S) which also binds adenosine and adenosyl derivatives. Species C represents 30% of the activity in the extracts and resemble the "adenosine analogue binding proteins" described in mammalian cells. The relevance of the properties of these proteins to the developmental process of D. discoideum amoebas is discussed.

Binding, Competitive↗
PubMed1978

[Clinical, bacteriological and pharmacokinetic study of Sisomicin in the newborn infant].

A study of the efficiency and tolerance of sisomicin in 19 children with severe bacterial infections led to the following conclusions: -sisomicin was efficient, particularly in association with beta-lactamin; -the local and systemic tolerance was good. The susceptibility of various bacterial strains was studied. The half-life of sisomicin given intramuscularly was : 4,0 +/- 1,8 hours in the new-borns under 10 days and 2,0 +/- 0,3 hours in older infants, when creatininemia was below 10 mg/l. No accumulation was found. The recommended daily dose of sisomicin by intramuscular route is 3 to 6 mg/kg, i.e. 1 to 2 mg every 8 hours in infants an 1,5 to 3 mg every 12 hours in new-borns.

Bacterial Infections↗
PubMed1977

Binding of concanavalin A to the surface of sea urchin eggs and its alteration upon fertilization.

The binding of concanavalin A (Con A) to Strongylocentrotus purpuratus eggs has been investigated using 125I-concanavalin A (125I-Con A). The lectin binds specifically to the egg surface and does not produce agglutination of the eggs. High 125I-Con A concentrations are necessary to saturate all of the surface binding sites. Scatchard plots of the binding data are biphasic and may be interpreted as showing two main classes of sites. Unfertilized eggs have 4 X 10(8) high affinity sites/egg (Ka=8 X 10(-7) M) and 4.5 X 10(8) istes of lower affinity (Kb=4 X 10(-6) M). The sites may be assigned to different layers of the egg surface by studying the effects of removal of egg coats on the binding reaction. Removal of the jelly coat by washing eggs at pH 4.5 has no effect on binding. However, disruption of the vitelline layer with dithiothreitol leads to a decrease in the number of high affinity sites. After fertilization, the high affinity sites are found upon the fertilization membrane produced from the vitelline layer. Low affinity sites predominate in the plasma membrane, and are not affected by treatments which alter the vitellinelayer. The number of low affinity sites double upon fertilization, with the insertion of new membrane into the egg surface, as a result of cortical granule exocytosis. The doubling of sites is not due to hyaline material released from the cortical vesicles at fertilization, and thus these sites appear to reside upon the new membrane that is inserted from the cortical vesicles. If eggs are activated with ammonia, bypassing the cortical reaction, no change in the binding of ConA occurs. Con A inhibits fertilization at concentrations higher than 0.1 mg/ml, where less than 50% of the high affinity (viteline layer) binding sites are occupied, and there is little binding to the low affinity (plasma membrane) sites. Thus, the interaction of sperm with vitelline layer components may be an obligatory step in the fertilization process. A fraction of the 125I-Con A binding sites is cleaved from the egg surface upon fertilization or after activation by the calcium ionophore A23187. This release of Con A binding sites occurs during the limited proteolysis of surface components that accompanies the cortical reaction, and does not occur with ammonia activation of the egg, where the cortical reaction does not occur. Thus, the changes in Con A binding at fertilization are caused by the massive cortical granule exocytosis that occurs within minutes of sperm penetration, and not by activation of the egg per se.

Animals↗
PubMed1977

Sequential biochemical and morphological events during assembly of the fertilization membrane of the sea urchin.

The fertilization membrane of Strongylocentrotus purpuratus undergoes changes in morphology, solubility, and permeability during the process of hardening. As the fertilization membrane elevates from the egg surface, it retains casts of the tips of the microvillous processes of the plasma membrane. The dome-shaped microvillar casts become angular at the same time that the fertilization membrane becomes resistant to solubilization in mercaptan solutions. 2-4 min after this morphological and chemical transition, the fertilization membrane becomes impermeable to the lectin conconavalin A, as monitored by binding of 125I- or fluorescein-labeled concanavalin A. Glycine ethyl ester inhibits the changes in morphology, solubility, and permeability, whereas sodium sulfite inhibits only the permeability block and resistance to solubilization by mercaptans. Parthenogenetic activation with the divalent ionophore, A23187, elicits fertilization membrane elevation more rapidly than does activation by fertilization; however, the morphological and permeability changes characteristic of hardening proceed more slowly. Elevation and hardening of the fertilization membrane thus appear to be discrete, multiple-step assembly processes that occur in fixed sequence, with kinetics that are affected by the mechanism of cortical granule exocytosis.

Animals↗