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Biomedical subjects

L Valette

Publications and source records attributed to L Valette.

At least 19 recordsLinked to original sources
PubMed1991

Dietary polyunsaturated fatty acids modulate fatty acid composition and early activation steps of concanavalin A-stimulated rat thymocytes.

The early biochemical responses to concanavalin A (Con A) of thymocytes from rats fed a saturated (coconut oil), (n-6) (sunflower oil) or (n-3) (fish oil) fatty acid-enriched diet for 3 wk were investigated. Fish oil feeding resulted in greater (n-3) polyunsaturated fatty acid level (PUFA) at the expense of (n-6) PUFA in total and individual thymocyte phospholipids. Such alterations of the fatty acid composition did not affect basal ornithine decarboxylase (ODC), cyclic nucleotide phosphodiesterase (PDE) or gamma-glutamyl transferase activities. However, the fish oil-enriched diet impaired some of the early thymocyte responses to Con A, such as the rapid induction (30 min) of soluble ODC and PDE activities. Synthesis of [3H]20:4(n-6) oxygenated metabolites was not different between the dietary groups; however, the uptake of [3H]20:4(n-6) into phospholipid classes was significantly lower in phosphatidylcholine and greater in phosphatidylethanolamine and phosphatidylinositol after fish oil feeding. Similarly, the Con A-induced remodeling of the [3H]20:4(n-6) esterification in phospholipids differed in sunflower oil- vs. fish oil-fed rats, suggesting a modulation of acyl CoA synthase and/or acyl CoA transferase activities. Thus, the modulation of Con A-induced ODC and PDE stimulation upon in vivo changes of membrane phospholipid fatty acid composition is not related to eicosanoid formation, but rather to the modification of the fatty acid acylation processes, altering phospholipid composition and signal transduction.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1990

Concanavalin A stimulates the Rolipram-sensitive isoforms of cyclic nucleotide phosphodiesterase in rat thymic lymphocytes.

Pretreatment of rat thymic lymphocytes with Concanavalin A induced a very early (30 min) and substantial increase (+90%) of the soluble cAMP phosphodiesterase activity. The crude cytosolic phosphodiesterase activity of rat thymocytes could reproducively be resolved by Mono-Q ion exchange high performance liquid chromatography into four separate phosphodiesterase peaks: a cGMP-stimulated, two cAMP-specific Rolipram-sensitive and a cGMP-inhibited cardiotrope-sensitive peaks. Concanavalin A stimulated very specifically the activity of the two predominant cAMP-specific Rolipram sensitive peaks whereas it only slightly modified the cGMP-stimulated and the cGMP-inhibited forms. The present results strongly suggest that the Rolipram-sensitive cAMP PDE activity may play a key role in the control and regulation of mitogen-induced thymocyte proliferation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1990

Early induction of ornithine decarboxylase occurs simultaneously with inositol phosphate accumulation in concanavalin A-stimulated rat thymocytes.

Stimulation of rat thymocytes with the lectin ConA produced an early peak of ornithine decarboxylase (ODC) activity within 10 min. This ODC induction appeared as early as the well-known inositol phosphate accumulation following mitogenic stimulation, and may be part of the signal transduction mechanism. The distribution of counts among the inositol phosphates was constant during the overall time of Concanavalin A (ConA) stimulation. We conclude that early induction of pre-existing ODC may be independent of protein kinase C action.

Animals↗
PubMed1978

[Determination of antigen structures of Pasteurella multocida: the preparation of vaccines].

The discovery of the role played by somatic antigens of the Pasteurella multocida A and D capsular types in the immunization of susceptible species makes it necessary to type the somatic antigens of the isolated strains prior to any action to induce active or passive immunity. Only immunoprecipitation in gel was chosen out of the various typing techniques proposed, and a correlation was established between the capsular types (according to Carter), somatic types (according to Namioka) and types determined by immunoprecipitation in gel (according to Heddleston). Parallel to this, the same technique was developed for strains of Pasteurella multocida B and E capsular types, and the immunogenicity of these capsular antigens was proven.

Agglutination Tests↗
PubMed1976

[Failure of anti-symptomatic vaccination and the methods of vaccine activity control].

Blackleg (Clostridium chauvoei) infection in Charollais cattle appears to have undergone some etiological and pathogenic changes which are reflected in the apparent failure of vaccination. Two methods have been used to determine the quality of the vaccines in order to meet the different requirements specified by pharmacopeias. The two methods differ in the vaccination schedules of the guinea pigs and the test strain used which may be either a virulent culture or a suspension of spore in calcium chloride. Both methods appear to be efficient in selecting vaccines which provide good protection. It follows, therefore, that the vaccination failures would appear to be the result of intensive selection of beef cattle with reduced immunological response. If this is the case, the remedy for these vaccination failures might lie in an adaptation of the vaccination schedule to the early developing breeds of cattle obtained by intensive selective breeding.

Animals↗
PubMed1976

[Several strains of Mycobacterium paratuberculosis: biochemical characteristics and allergic activity].

Judged from its biochemical properties and antigenic structure, Mycobacterium paratuberculosis is related to M. avium. When M. paratuberculosis was compared to B.C.G., several essential differences, were found that allowed their clear separation, within Runyon's Group III, M. paratuberculosis is differentiated by its biochemical properties as shown in the following table : (formula: see text). The allergic response of a guinea pig infected with M. paratuberculosis was stronger when an avium sensitine was used that when a bovine tuberculine was used.

Animals↗
PubMed1976

[Combined vaccines including 1 or several anti-foot-and-mouth valences].

Combined vaccines are used for many human and animal diseases. However, we have very few examples of combinations containing anti-foot-and-mouth valence which would allow easy immunization against differnet diseases without additional handling. Until now foot-and-mouth vaccination has been applied simultaneously with anti-brucellic vaccination (Baldoni, Renoux), andi-anthrax (Nobili) and vaccination against swine fever and Aujeszky's disease (Lysenko). During the last ten years we have particularly studied the association of anti-foot-and-mouth disease vaccines with anti-brucella and anti-rabies vaccines. We have shown the possiblity of combining these different antigens, either in classical aqueous vaccines in aluminum hydroxide, or in emulsified vaccines containing oily adjuvants. The anti-brucella valences may be agglutinogenic (H 38) or non-agglutinogenic (MacEwen 45/20). The combined vaccines "rabies + foot-and-mouth disease" and "brucellosis + foot-and-mouth disease" can be produced on an industrial scale. For many years millions of animals have been successfully vaccinated in France by means of a combined "rabies + foot-and-mouth disease" vaccine.

Adjuvants, Immunologic↗
PubMed1976

[Anti-foot-and-mouth vaccines combined with other bacterial or viral vaccines].

Medical and sanitary prevention of a growing number of major infectious diseases of bovines has led IFFA-Mérieux to investigate the association of vaccines and to define methods of utilization. Care has been taken to limit the number of interventions and at the same time to retain in the combined valences the efficacy they had when in a state of single constituent. The work which has been carried out for the last ten years, including the study of adjuvants as well as of incompatibility of associations, has permitted the improvement of formulas, reduced in volume (5 ml for a plurivalent dose), in aqueous excipient (aluminum hydroxide and saponin) or oily excipient (oil in water type). These formulas combine 3 foot-and-mouth disease valences with a rabies valence (fixed strain grown on cell culture) or with a brucellosis valence (strain B. abortus MacEwen 45/20 and B. melitensis H 38). The innocuity of these associations allows them to be used in sanitary compaigns; their efficacy is equal to that of monovalent vaccines. A logical vaccination calendar is proposed.

Adjuvants, Immunologic↗
PubMed1976

[Evaluation of antibrucellic vaccines in mice].

The activity of the antibrucellic vaccines was tested on mice by vaccination at varying doses. The vaccinated mice and the controls were then challenged with a fixed quantity of virulent brucella. The animals were then sacrificed, the spleens were weighed and a count was taken of the virulent brucella which they contained. These two indications, weight of the spleen and intensity of infection, allow to compare the activity of the vaccines and to have an indispensible routine test for production control.

Animals↗
PubMed1976

Freeze-drying of brucella vaccine strain B 19.

The B 19 brucellosis strain has been widely used in the production of live vaccine against Bovine Brucellosis in the field for the last 30 years. Many attempts have been made to stabilize this vaccine but it remains a problem for laboratories which prepare this vaccine. In order to improve our knowledge of the influence of residual moisture and the nature of the conditioning atomosphere, several batches of vaccine were prepared in the same freeze-drying apparatus, either with a different atmosphere, or with a different level of residual moisture. After freeze-drying, the percentage of live bacteria and the stability of the vaccine at 37 degrees and 4 degrees C were investigated. It is thus possible to determine under specific conditions the level of residual moisture which gives: a) the best stability and b) the correct percentage of live bacteria after freeze-drying. Furthermore, by using nitrogen, argon, or a vacuum in the freeze-drying procedure, it was possible to select the most favourable atmosphere for conditioning the vaccine.

Brucella Vaccine↗