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Biomedical subjects

C Michel

Publications and source records attributed to C Michel.

At least 343 records · Page 19Linked to original sources
PubMed1981

A bacterial disease of perch (Perca fluviatilis L.) in an alpine lake: isolation and preliminary study of the causative organism.

An epizootic among perch (Perca fluviatilis L.) occurred during the summer and fall of 1979 in an alpine lake (Lake Annecy, Haute-Savoie) in France. Hemorrhagic and ulcerative clinical signs were associated with the height of the mortality. A Gram-negative, non-motile, slow-growing bacterium was isolated from skin lesions is diseased fish. Aeromonas hydrophila often was present. Since the nonmotile bacterium was suspected to be the etiological agent, its characteristics and pathogenicity were determined. The bacterium was pathogenic to perch, possibly pathogenic to rainbow trout, and non-pathogenic to carp. It could be reisolated from infected fish, but its physiologic and biochemical properties have not been assessed to determine the taxonomic position.

Aeromonas↗
PubMed1980

Cuticle and mucous glands in the oesophagus of an annelid (Nereis virens).

The oesophagus of Nereis virens is divided into anterior and posterior regions and possesses several peculiar features not previously described for cuticle or glands of Polychaetes either in body or foregut integument. The mucous cells which are permanent glands in both regions secrete a carboxylated acidic mucus and possess apical mechanisms permitting the opening and closing of the neck of the glands. The cuticle of the posterior oesophagus bears numerous striated spines and several hypotheses concerning their physiological role are discussed.

Animals↗
PubMed1980

Formation of ethylene from methionine. Reactivity of radiolytically produced oxygen radicals and effect of substrate activation.

Ethylene was determined by gas chromatography after reaction of radiolytically produced OH and O2- radicals with methionine, methionine + pyridoxal phosphate and S-adenosyl-methionine (SAM). Both oxygen radicals, alone or in combination, liberate ethylene from methionine and methionine/pyridoxal phosphate. From SAM ethylene was primarily produced by the combined attack of OH nad H2O2 or O2-.

Chromatography, Gas↗
PubMed1980

Persistence of the virulence of Aeromonas salmonicida strains kept in river sediments.

The persistence of pathogenicity in two strains of Aeromonas salmonicida maintained in river sediments was studied at different times. Cultures were kept about nine months, and the virulence was compared to its initial value exhibited by the same strain, subcultivated in rainbow trout fingerlings. Trials involved intramuscular injection of comparable doses of bacteria to batches of 30 fish held at 15 degrees C, and recording of subsequent mortalities. No difference was found during the first six months, after which a decrease of pathogenicity resulted in its disappearance before the ninth month. Progressive decrease in incubation temperatures was also exerted to simulate an artificial wintering, but did not alter the evolution of the virulence. The possible role of mud as a source of contamination for fish is discussed.

Aeromonas↗
PubMed1979

Long-term effects of negative pions in female mice exposed to whole-body irradiation.

Long-term effects, especially the incidence of tumors, of whole-body exposure of female NMRI mice with either negative pions (peak or plateau region) or X rays have been studied in comparison to controls. Animals were irradiated at the age of 10 days after birth. The mice were then regularly examined for deaths and signs of severe disease, moribund animals being killed. A detailed histopathological work-up has been performed. The data show that the survival as defined by death or the time of autopsy is significantly lower in irradiated mice in comparison to controls, that there is no difference in reduction of survival between groups treated either with X rays or pions at peak region, but that a difference can be seen when comparing X rays with pions at plateau region. The incidence of ovarian tumors at any particular age is higher in mice treated with X rays or pions than in control groups, but significantly lower in animals exposed to plateau pions than in those treated with peak pions or X rays.

Animals↗
PubMed1979

Low-dose effects of X-rays and negative pions on the pronuclear zygote stage of mouse embryos.

Mouse embryos in the pronuclear-zygote stage (day 0 of gestation) were irradiated with 13.5 rad of 140kV X-rays or negative pions. On day 13 the fetuses were examined for developmental anomalies such as intrauterine death, growth retardation and malformations. Significant decreases in the percentage of normal implantations were obtained with peak pions (high LET) and X-rays, whereas the effect of plateau pions was less obvious. Irradiation with peak pions was more effective than with X-rays by a factor of about 1.7.

Abnormalities, Radiation-Induced↗
PubMed1979

Pulse-radiolytic investigations of catechols and catecholamines. II. Reactions of Tiron with oxygen radical species.

Transient spectra and kinetic data of Tiron (1,2-dihydroxybenzene-3,5-disulphonic acid) are reported, obtained after pulse-radiolytic oxidation by hydroxyl radicals (.OH), superoxide anions (O-2) or a combination of both oxygen radicals. The rate constant with .OH radicals was determined at 1.0.10(9) M-1.s-1. Contrary to a previous report (Greenstock, C.L. and Miller, R.W. (1975) Biochim. Biophys. Acta 396, 11--16), the rate constant with O-2 of 1.0.10(7) M-1.s-1 is lower by one order of magnitude; also the semiquinone absorbs at 300 nm rather than at 400 nm. The ratio of the rate constants with .OH and O-2 of 100 again demonstrates that any oxidation reaction by the latter radical is unspecific due to the more efficient reaction of .OH radicals, leading to the same products with catechol compounds.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗
PubMed1979

On the nature of biochemically generated hydroxyl radicals. Studies using the bleaching of p-nitrosodimethylaniline as a direct assay method.

An efficient scavenger for radiolytically generated hydroxyl (OH) radicals, p-nitrosodimethylaniline, was used to try to substantiate the presence of this oxygen radical species in several biochemical systems. Most of these systems which were investigated had previously been assumed to generate OH radicals, e.g. the autoxidation of 6-hydroxydopamine, the hydroxylating system NADH/phenazine methosulfate, and the oxidation of xanthine or acetaldehyde by xanthine oxidase. We did not observe inhibition of the bleaching of p-nitrosodimethylaniline in oxygenated solutions by other scavengers of OH radicals nor, in the case of xanthine/xanthine oxidase, by catalase and superoxide dismutase. We therefore conclude that, under biochemical conditions as opposed to radiolysis or photolysis, no freely diffusable OH radicals are formed. Rather, a strongly oxidizing OH-analogous complex is considered to represent the p-nitrosodimethylaniline-detectable species formed under these conditions.

Acetaldehyde↗
PubMed1979

Furunculosis of salmonids: vaccination attempts in rainbow trout (Salmo gairdneri) by formalin-killed germs.

Two immunization trials were performed in rainbow trout, using a formalin killed Aeromonas salmonicida suspension. In the first experiment, 200 g fish were administered orally or intraperitoneally. Circulating antibodies were elicited in injected animals only, but no protection was found when they were challenged with a highly virulent strain. Rough and smooth bacteria have provided similar agglutinins titers. In the second study, fingerlings were vaccinated by injection, but experimental disease was reproduced through IP or IM inoculations. Protection was effective in the second case. In the IP injected group the mortality was the same in vaccinated fish and controls, and carriers were detected among survivors 3 months later. The surprising fact is that serum agglutinins did not always provide a protection. This last one depends on different factors such as pathogenicity of strains and route of penetration of the challenge bacteria. So, experimental challenge has to be improved.

Administration, Oral↗
PubMed1979

Rainbow trout complement fixation used for titration of antibodies against several pathogens.

Since it is impossible to fix guinea pig complement (C) with Rainbow Trout (Salmo gairdneri) antibodies, whereas it is possible with Brown Trout (Salmo trutta) antibodies, a C fixation test has been designed which uses haemolysin and C from Rainbow Trout. Immunization of trout against lysed sheep red blood cells (SRBC) elicited production of haemolytic IgM. Normal trout serum (NTS) can be used as a source of C at a dilution at which its "natural" haemolytic activity (against various homeotherms RBC) has disappeared. Heating of trout C 30 min at 37 degrees C leads to a 75% loss of its activity, and this one is completely abolished at 40 degrees C. Fixation of 3 to 4 CH50 units has been achieved in a short test (2 h at 20 degrees C) for the following antigen-antibody systems: 2 bacterial antigens (Aeromonas salmonicida and Vibrio anguillarum); 2 viruses (Infectious Pancreatic Necrosis (IPN) virus and Egtved Virus). C fixation has a sensitivity comparable with agglutination in the case of A. salmonicida. For IPN Virus, sero-neutralization is 50 times more sensitive than C fixation. In the case of Egtved virus, the difference is not so great.

Animals↗
PubMed1978

The involvement of oxygen radicals during the autoxidation of adrenalin.

1. In unbuffered alkaline solutions, autoxidizing adrenalin generates superoxide anions: both the scavenging by adrenalin itself, leading to adrenochrome, and the formation of nitrite from hydroxylamine are inhibited by superoxide dismutase. No hydroxyl radical could be detected. 2. The yield of hydrogen peroxide increases with pH in a way similar to that of adrenochrome and nitrite. The dissociated form of adrenalin (pK = 8.5) is proposed as the source of superoxide anions. 3. Superoxide dismutase delays rather than inhibits the reaction. In addition to the diminished formation of adrenochrome due to the scavenging of superoxide anions and re-reduction of the semiquinone by hydrogen peroxide, respectively, adrenochrome is further removed by hydrogen peroxide, with final products absorbing at 310 nm. 4. The diminished inhibitory effect of superoxide dismutase above pH 10 is due to superoxide-independent reactions. This effect is masked by the alkaline conversion of adrenochrome to indole compounds. 5. It is concluded that monitoring the absorption of adrenochrome in alkaline solutions does not produce reliable evidence for superoxide anions.

Adrenochrome↗