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Biomedical subjects

M Leconte

Publications and source records attributed to M Leconte.

15 recordsLinked to original sources
PubMed2005

Genetic evidence of local adaptation of wheat yellow rust (Puccinia striiformis f. sp. tritici) within France.

Puccinia striiformis f. sp. tritici (PST), a clonal basidiomycete causing yellow rust disease on wheat, has a long record of 'overcoming' cultivar resistance introduced by breeders. Despite the long dispersal capacity of its spores, the French population of PST presents a strong geographical structure, with the presence of a specific pathotype (array of avirulence genes) at high frequencies in the south of France. The genetic diversity underlying this differentiation was analysed by microsatellite and AFLP markers. A total of 213 French isolates belonging to 10 pathotypes collected over a 15-year period were investigated. For each of the 12 microsatellites used, polymorphism resulted from a unique allelic variant associated to the south-specific pathotype. This pathotype was characterized by 40 specific markers over the total of 63 polymorphins detected using 15 AFLP primer combinations. Phylogeographical analysis indicated a strictly clonal structure of the population, and a strong genomic divergence between the northern population and a south-specific clone. Both virulence and molecular data show that the northern French population belongs to the northwestern European population, whereas the southern clone is most likely related to a Mediterranean population, the two subpopulations resulting from the ancient divergence of two clonal lineages. While the virulence complexity in the northern population may be explained by the successive introduction of corresponding resistance genes in cultivars, the maintenance of a simple virulence type in southern France, despite gene flow between the two populations, may be explained in terms of host cultivars repartition and local adaptation to specific host or climatic conditions.

Adaptation, Physiological↗
PubMed2004

Mixing and reaction fronts in laminar flows.

Autocatalytic reaction fronts between unreacted and reacted mixtures in the absence of fluid flow propagate as solitary waves. In the presence of imposed flow, the interplay between diffusion and advection enhances the mixing, leading to Taylor hydrodynamic dispersion. We present asymptotic theories in the two limits of small and large Thiele modulus (slow and fast reaction kinetics, respectively) that incorporate flow, diffusion, and reaction. For the first case, we show that the problem can be handled to leading order by the introduction of the Taylor dispersion replacing the molecular diffusion coefficient by its Taylor counterpart. In the second case, the leading-order behavior satisfies the eikonal equation. Numerical simulations using a lattice gas model show good agreement with the theory. The Taylor model is relevant to microfluidics applications, whereas the eikonal model applies at larger length scales.

Journal Article↗
PubMed2003

Pattern of reaction diffusion fronts in laminar flows.

Autocatalytic reaction between reacted and unreacted species may propagate as solitary waves, namely, at a constant front velocity and with a stationary concentration profile, resulting from a balance between molecular diffusion and chemical reaction. The effect of advective flow on the autocatalytic reaction between iodate and arsenous acid in cylindrical tubes and Hele-Shaw cells is analyzed experimentally and numerically using lattice Bhatnagar-Gross-Krook simulations. We do observe the existence of solitary waves with concentration profiles exhibiting a cusp and we delineate the eikonal and mixing regimes recently predicted.

Animals↗
PubMed2003

Differences in the digestive tract characteristics of broiler chickens fed on complete pelleted diet or on whole wheat added to pelleted protein concentrate.

1. The effects of whole grains of wheat on the digestive tract of broiler chickens was studied. A complete pelleted feed was compared with free choice feeding of whole wheat and a pelleted protein concentrate, given from 7 to 29 d of age. 2. Pepsin activity in proventriculus tissue was lower in whole wheat-fed birds than in complete diet-fed birds. The weight (g/kg body weight) of the gizzard was higher in whole wheat-fed birds and its contents had a lower pH. 3. In the intestine, there were no differences in deoxyribonucleic acid (DNA) concentration, protein/DNA, ribonucleic acid (RNA)/DNA, RNA/protein ratios or alkaline phosphatase activity expressed per tissue weight. The weight (g/kg body weight) of the duodenum was lower in whole wheat-fed birds and its contents had a higher pH. Also the activities of alkaline phosphatase and leucine aminopeptidase in the duodenum, and maltase in the ileum, expressed per unit of bird weight, were lower in whole wheat-fed birds. 4. These results suggest that whole grain feeding increases the chemical (pepsin in proventriculus) and physical (gizzard muscle) functionality of the upper part of the digestive tract but decreases the digestive capacity of the intestine. Higher gizzard functionality may play a positive role in the control of bacterial populations. The lower digestive enzyme activities in the intestine may be detrimental in situations of mucosal deterioration caused by intestinal disease.

Animal Feed↗
PubMed2003

Effects of whole wheat feeding on the development of coccidial infection in broiler chickens.

A complete ground and pelleted feed was compared to free choice feeding of whole wheat and a pelleted protein concentrate during three experimental infections with coccidia in broiler chickens. At 22 d of age birds were inoculated with different doses of sporulated oocysts of a cecal species (Eimeria tenella) in experiment 1 or intestinal species E. maxima or E. acervulina in experiments 2 and 3, respectively. The effects of diets were assessed on weight gain, hematocrit (during cecal coccidiosis), serum coloration (during intestinal coccidiosis), oocyst excretion, and lesion score until 7 d post-inoculation. In experiment 1 before inoculation, the birds fed whole grain had more beneficial microflora with lower counts of coliform bacteria. As shown by oocyst output and lesion score, whole wheat feeding increased parasite development during infection with the cecal parasite E. tenella. This led to significantly lower weight gain with whole wheat than with ground wheat from 5 to 6 d post-inoculation and to lower hematocrit at the highest infective dose. Parasite development in experiments 2 and 3 was similar among diets, during intestinal infection with E. maxima and E. acervulina, respectively, with no significant differences in lesion score. During the acute phase (4 to 7 and 3 to 5 d post-inoculation), when a difference appeared between diets, whole wheat fed-birds were always more affected than ground diet-fed birds in terms of serum coloration and weight gain. These results might be explained by modifications of digestive physiology and intestinal microflora by whole wheat.

Animal Feed↗
PubMed2001

Posture-related distribution of hyperbaric bupivacaine in cerebro-spinal fluid is influenced by spinal needle characteristics.

BACKGROUND: No studies have evaluated the relationship between duration of time sitting and spinal needle type on the maximal spread of local anaesthetics. The few trials available have studied the influence of time spent sitting on the spread of anaesthesia without standardising spinal needle types, and have not found any effect. METHODS: In this randomised, blinded study, 60 patients scheduled for elective orthopaedic surgery of the lower limbs were divided into 4 groups. With the patient sitting erect, 15 mg hyperbaric bupivacaine were injected in a standard manner through a 24G Sprotte or a 27G Whitacre needle and patients were placed supine after 1 min (24G/1 group and 27G/1 group) or 4 min (24G/4 group and 27G/4 group). RESULTS: Time to achieve maximum block height after injection was similar in all groups. Block height levels were significantly lower at all time points for the 24G/4 group. Maximum block heights were Th4 in the 24G/1, 27G/1 and 27G/4 groups, and Th6 in the 24G/4 group (P<0.0001). CONCLUSION: In a standard spinal anaesthesia procedure, when different lengths of time spent sitting are compared, spinal needle characteristics influence the maximum spread of hyperbaric bupivacaine. However, within the limits of our study, a two-segment difference in block height is too small to consider using spinal needles as valuable tools to control block height during spinal anaesthesia in our daily practice.

Adult↗
PubMed1996

Ability of different flavonoids to inhibit the procoagulant activity of adherent human monocytes.

Sixty-five natural flavonoids of various chemical classes were screened for their ability to inhibit the procoagulant activity of adherent human monocytes stimulated by endotoxin and interleukin-1 beta in vitro. Eighteen of these compounds inhibited the interleukin-1 beta-induced expression of tissue factor on human monocytes, but the most active compound was a biflavonoid: hinokiflavone.

Amino Acid Sequence↗
PubMed1981

[Immunity in tetanus].

Among twenty six patients who have got tetanus the movement of the IgG, IgA, IgM, the serum complement, the number of B end T lymphocytes do not change in a significant way during the illness. There is no abnormally that could be considered as a consequence or a favorable factor of tetanus. In a group of patients being vaccinated against tetanus it has been given evidence that the specific antibodies develop much later than in a group of non vaccinated blood givers. Such an abnormal response can be found also in a third group of individuals without tetanus but whose ages in the average are comparable to these of the patients (69 years old). Thus, it seems not to be connected with tetanus itself but with the old ages of the patients.

Aged↗
PubMed1975

[Parenteral use of a solution-emulsion following digestive surgery].

A post-operative use of the calorico-nitrogenous mixture: Trivé 1000 was carried out in 25 patients after digestive surgery. The prescribed dose of this lipidic emulsion was 1,36 1 for an average period of four days. A study of the results led to establish the following facts:--a 55 p. cent increase in the nitrogen retention in comparison with a control series of ten patients and from (J o) the day of the intervention to (J F) the day when the treatment was stopped. Besides, the duration of the treatment did not seem to modify this balance, at least within the limits of the period of use. On the other hand, the quantity of EB 51 was a determining factor since 2000 ml were necessary to obtain a positive nitrogen balance (+ 0.96 g).--a very small rise in the amino-acid serous rate. It appeared in 14 patients and, supplied by EB 51, 3 other amino-acids increased their proportion spontaneously (Asp.--Gluc.--Tau.).--a reduction of the rate of 5 amino-acids, one of which, however, (Arginine) was being supplied by the drip. The variations were never statistically significant but for the Phenylalanine rate increase.--a non-systematic variation in the blood proteids that decreased as far as total proteids and albumin were concerned and that increased as far as globulins alpha1 and alpha2 were concerned.--Finally, no variations in the serous graphic record of lipid levels were noted, neither in the average of figures, nor in the analyses carried out after each bottle. Besides, it must be added that the tolerance of the product was excellent both on a general level (very few cases of intolerance: 4) and on the level of the plasma turbidimetry which did not reveal and chylomicrons except in one case. Therefore Trivé 1000 proved to be an interesting nutrient combinatin quite suited to a parenteral feeding because of its high caloric power. The necessity of a calories/g/nitrogen ratio from 100 to 200 corresponding to 2000 ml of EB 51 was once more evidenced. Therefore such a dose (for lack of a protein assimilation) allows for a nitrogen retention important enough to prevent an excessive consumption of the body proteinic reserves. Such doses are perfectly tolerated both on the general and metabolic levels (mainly on the lipometabolic one).

Adult↗