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S Hamon

Publications and source records attributed to S Hamon.

28 records · Page 2Linked to original sources
PubMed1996

Reliable flow cytometric estimation of nuclear DNA content in coffee trees.

Flow cytometry gave high resolution of genome size in two coffee taxa (Coffea liberica dewevrei and C. pseudozanguebariae). Propidium iodide (PI) and Petunia hybrida were used as dye and internal standard, respectively. Proportionally between the DNA content and the digitized fluorescence signal was checked. Five main results were evident. First, optimal experimental conditions were established for peak location estimation (mean or mode), staining time (at least 2 minutes), high voltage (557 V) for the photomultiplier tube (PMT), and PI concentration (333 micrograms/ml). Second, a parameterization of the effects of high voltage and PI concentration were deduced from curve fitting. Third, two biases in DNA content estimation were recorded for high voltage and PI concentration, and were minimized. Fourth, the genome sizes of C. liberica dewevrei and C. pseudozanguebariae were estimated with accuracy 2C = 1.421 +/- 0.005 pg and 2C = 1.129 +/- 0.005 pg, respectively. Fifth, between-genotype variance was emphasized within each taxon.

Cell Nucleus↗
PubMed1993

Inclusion bodies and crystals of Bacillus sphaericus mosquitocidal proteins expressed in various bacterial hosts.

Mosquitocidal proteins of 42 and 51 kDa from Bacillus sphaericus were produced in acrystallogenic B. sphaericus and B. subtilis strains. In both species, transformants containing each protein expressed individually were non-toxic for mosquito larvae and produced small inclusions which did not have a crystalline ultrastructure. When both components of the binary toxin were expressed together, toxicity was restored: oval and round amorphous inclusions were produced in B. subtilis, and typical native-type crystals were synthesized in B. sphaericus. In B. subtilis, native-type crystals were produced only when the two components of the binary toxin were synthesized as a 93-kDa fusion protein.

Bacillus↗
PubMed1992

Characterization and toxicity to mosquito larvae of four Bacillus sphaericus strains isolated from Brazilian soils.

Four Bacillus sphaericus strains, S1, S2, S5, and L2, isolated from Brazilian soils, were found to be toxic to larvae of the mosquitoes Culex pipiens and Anopheles stephensi at a level similar to that of strain 2362 which is now used operationally. Like strain 2362, the four strains belonged to the serotype H5 and produced major proteins of apparent molecular weights of 125, 110, 56, and 43 kDa. These latter two proteins were immunologically related to toxins of the same molecular weight as B. sphaericus 2362. Although the four Brazilian strains were very similar to strain 2362, gas chromatography analysis of the fatty acids revealed that these strains were different from strain 2362 and from each other, except for a possible similarity between strains S1 and S5.

Animals↗
PubMed1992

Vertebrate safety of Clostridium bifermentans serovar malaysia, a new larvicidal agent for vector control.

The safety of bacterial cells of Clostridium bifermentans serovar malaysia, which is highly toxic to mosquito larvae, was tested on mice, guinea pigs, rabbits, and goldfish. Inoculations of at least 1 x 10(8) cells per animal by routes recommended by World Health Organization (subcutaneous, percutaneous, inhalation, force-feeding, intraperitoneal, intravenous) and tests of subacute toxicity, anaphylactic shock, persistence in heart blood, and virulence by successive passages, were performed on mice, guinea pigs, or both. Growth was monitored for 1 mo before necropsy. Ocular irritation and skin scarification were tested with rabbits. C. bifermentans serovar malaysia did not induce any mortality or abnormal reactions in mammals at a dose 1,000 times higher than the level established by W.H.O. for the demonstration of safety. Bacterial cells are not toxic to goldfish at a dose 1,000 times higher than the LD50 for the target-mosquito larvae. We conclude that C. bifermentans serovar malaysia bacterial cells are safe for laboratory mammals and goldfish.

Animals↗
PubMed1992

Host range of Clostridium bifermentans serovar. malaysia, a mosquitocidal anaerobic bacterium.

Clostridium bifermentans serovar. malaysia (C.b.m.) is toxic to mosquito larvae. In this study, we quantified its toxicity to the mosquitoes, Aedes aegypti, Ae. albopictus, Ae. caspius, Ae. detritus, Anopheles stephensi, An. gambiae, Culex pipiens and Cx. quinquefasciatus. Anopheles larvae are the most susceptible, followed by Ae. detritus and Ae. caspius, then Culex and other Aedes larvae. According to mosquito species, the LC50 varies from 7 x 10(3) to 1.3 x 10(6) cells/ml. Three concentrations (10(7), 10(6) and 10(5) cells/ml) of C.b.m., Bacillus thuringiensis var. israelensis (B.t.i.) and Bacillus sphaericus were tested on Ae. aegypti, An. stephensi and Cx. pipiens larvae in order to determine the time necessary for each concentration to kill 50 and 90% of the population. Ninety percent of the 3 mosquito populations are killed within 4-15 h by the C.b.m. concentrations. Whatever the concentrations, C.b.m. kills at least 10 times less rapidly than B.t.i. but always quicker than B. sphaericus. Bioassays of C.b.m. bacterial cells or final whole culture were not toxic to Musca domestica and Drosophila melanogaster (Diptera) as well as to Phaedon cochleariae (Coleoptera) and Spodoptera littoralis (Lepidoptera).

Animals↗
PubMed1990

Serum lipid abnormalities in heart transplant recipients: predominance of HDL2-like particles in the HDL pattern.

Accelerated coronary atherosclerosis is a major risk limiting long-term survival after heart transplantation and is commonly associated with dyslipoproteinemia even in subjects who were not dyslipoproteinemic before intervention. The purpose of this study was to analyse the abnormalities in the lipid profiles of 2 different groups of heart-transplanted males: 18 subjects with underlying ischemic heart disease (IHD) and 19 subjects with non-obstructive cardiomyopathy of unknown aetiology (CM). Both groups were compared to 33 healthy males. All patients were under immunosuppressive therapy including prednisone, cyclosporin A and azathioprine. A moderate hyperlipidemia was found in all transplant recipients, associated with high HDL-cholesterol concentrations in the CM group (1.80 +/- 0.37 vs. 1.29 +/- 0.23 mmol/l) and normal HDL-cholesterol levels in the IHD group (1.40 +/- 0.23 mmol/l). HDL subfractionation showed a marked increase in HDL2-cholesterol (CM: 1.12 +/- 0.32; IHD: 0.69 +/- 0.28; control: 0.40 +/- 0.17 mmol/l) while HDL3-cholesterol was significantly lower than in the control group. Analysis of HDL particle sizes showed in all transplant subjects an increase of an intermediate size particle HDL2a (diameter 9.0 +/- 0.10 nm) which is a minor form in control subjects. In the CM group, both the common HDL2b (10.2 +/- 0.13 nm) and HDL2a were abundant in 13 of 17 patients. The pattern was more heterogeneous in the IHD group but witnessed to a high frequency of HDL2a particles either alone (5/14) or associated with larger HDL2b (4/14) or with small HDL3 (4/14).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathies↗
PubMedDate not supplied

Another Bacillus sphaericus serotype harbouring strains very toxic to mosquito larvae: serotype H6.

Ten isolates of Bacillus sphaericus from Ghana, very toxic to mosquito larvae, have been identified as belonging to serotype H6. These isolates can be represented by the head-group strain IAB59. They form crystals at the sporulation stage. Their larvicidal effect on Culex pipiens and Anopheles stephensi larvae is as high as that of the most toxic strains already known, e.g. 1593 and 2362 (serotype H5a,5b) and 2297 (serotype H25). Spore-crystal extracts of all these strains contain a 43-Kd polypeptide immunologically related to the 43-Kd polypeptide from strain 2362 described by other authors.

Animals↗
PubMedDate not supplied

Beneficial effect of post -thawing osmoconditioning on the recovery of cryopreserved coffee (Coffea arabica L.) seeds.

Osmoconditioning-controlled rehydration of seeds in a solution with low osmotic potential -has been shown to reinvigorate aged seeds. The present work aimed at investigating the effect of osmoconditioning on the germination of cryopreserved seeds of Coffea arabica, whose viability and vigour are drastically affected by cryopreservation. For cryopreservation, seeds were desiccated to 0.21 g H2O/g dw, cooled at 1 degree C/min to -50 degree C, then immersed rapidly in liquid nitrogen. After rapid rewarming, seeds were osmoconditioned for 1 to 6 weeks using solutions with osmotic potentials between -1 and -4 MPa. The time to produce half of the final percentage of normal seedlings, T50, was about three fold lower with osmoconditioned seeds than with non-osmoconditioned seeds (12-14 d vs 36 d). Moreover, after a 6-week osmoconditioning treatment with solutions with osmotic potential of -1 and -1.25 MPa, the percentage of seedlings recovered from cryopreserved seeds was 64-74%, against 13-16% only for cryopreserved seeds which were not osmoconditioned.

Journal Article↗