RESUMO
We define the class of bivariate binomial distributions as Poisson distributions transformed by a binomial dilution and mixing with a gamma distribution. They are used to study the number of nematodes, considering the sex ratio, parasitizing birds.
Assuntos
Doenças das Aves/parasitologia , Modelos Biológicos , Nematoides/crescimento & desenvolvimento , Infecções por Nematoides/veterinária , Aves Canoras/parasitologia , Animais , Distribuição Binomial , Feminino , Masculino , Infecções por Nematoides/parasitologia , Distribuição de Poisson , Razão de MasculinidadeRESUMO
The antigenic mutant Shigella flexneri 3b showed selective prevalence when subcultured with the original strain 1b. Mathematical analysis of such co-cultures showed that the dynamics of bacterial growth may be described by equations of the Lotka-Volterra type. The analysis of serial cultivations suggests that parameters of the equations may be realizations of random variables characterizing strains and media. The mutant carries a prophage lethal for the original strain. Distinctive features of the growth of these strains alone and in co-culture may be successfully explained by the differences in growth parameters, without phage inference. The concurrence model connected only with the existence of the phage is not sufficient. A complete description of the dynamics of the co-culture is obtained by the connection of the assumptions of two models: strains in competition and growth of strains with phage, given the random character of the parameters.
Assuntos
Shigella flexneri/crescimento & desenvolvimento , Antígenos de Bactérias/imunologia , Bacteriófagos/fisiologia , Divisão Celular , Meios de Cultura , Lisogenia , Modelos Biológicos , Modelos Estatísticos , Mutação , Dinâmica Populacional , Shigella flexneri/genética , Shigella flexneri/imunologia , Shigella flexneri/virologiaRESUMO
Several S. flexneri 1b serotype strains of clinical isolation were compared with their 3b serotype variants isolated either as Lac+ recombinants from crosses of S. flexneri x E. coli Hfr C, or F2-resistant mutants. The studied variants 3b were deprived of type I antigen but acquired type III antigen. They appeared to be less sensitive to killing action of complement present in normal bovine serum although kinetics of killing and its effectiveness differed between the strains.
Assuntos
Variação Antigênica/fisiologia , Proteínas do Sistema Complemento/imunologia , Óperon Lac/genética , Mutação , Shigella flexneri/genética , Shigella flexneri/imunologia , Animais , Antígenos de Bactérias/imunologia , Bacteriófagos/genética , Bovinos , Complemento C3b/imunologia , Epitopos , Cinética , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Sensibilidade e EspecificidadeRESUMO
Conditions of optimizing mating efficiency in the yeast. Saccharomyces cerevisiae were tested and measured as a number of prototrophic diploids. It was found that the process of diploid formation could be controlled by suitably adjusting cell densities in liquid mating medium and alpha: a mating type cell ratio. When the first was about 5 x 10(8) per ml and the second 1:10, respectively, every alpha cell was able to find a partner of opposite mating type. Some mathematical models of the "courtship" in yeast were advanced and the conclusions are discussed in the light of recent data on mating pathway in S. cerevisiae.
