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111.
H. R. Akçakaya L. R. Ginzburg D. Slice L. B. Slobodkin 《Bulletin of mathematical biology》1988,50(5):503-515
Traditional population models describe changes in population size as a function of changes in the resources. Such first-order
models cannot describe certain properties of population dynamics. General models with delays can account for all the observed
dynamic complexities but are judged overgeneralized. It is proposed that the simplest model of intermediate complexity that
explains such dynamic properties is a second-order model, which describes population dynamics as a function of a physiological
variable, the dynamics of which in turn depends on resources. Data on accelerated decline of populations in the absence of
food from experiments with brown and green hydra as well as literature data support the arguments. 相似文献
112.
A S Ginzburg 《Ontogenez》1989,20(1):47-57
The process of labyrinth determination has been studied in amphibians (three Urodela and seven Anura species) using homoplastic transplantation of ear ectoderm, containing labyrinth material onto the abdominal wall of embryos of the same stage of development. The stage of appearance of organ-specific properties in ear ectoderm was determined and the increase of these properties in the course of development was observed. The frequency of ear vesicles formation, the level of their differentiation and their size served as criteria. These criteria allow to align the studied species into a row, where organ-specific properties appear earlier and most completely in representatives of Ranidae family and in Bufo viridis, and weakest, in smooth newt. A comparison of properties of labyrinth material and other areas of ectoderm allowed to conclude that specific differences in determination of different ectodermal primordia are based on specific peculiarities of the whole ectoderm. The appearance of these differences can be explained by the shift in the beginning of gastrulation towards later stages of cleavage during the evolution of amphibians. 相似文献
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Methods of the Mendelian analysis of quantitative characters by pedigrees selected for proband are discussed. The method is illustrated on the example of the familial hypercholesterinemia in man. The estimations of parameters of monogenic hypothesis of inheritance, obtained by the maximum likelihood method, are considered, their adequacy discussed, and prognostic criteria of fitness of the genetic hypothesis introduced. 相似文献
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The antimicrobial spectrum of cefuroxime, an antibiotic of the cephalosporin family was studied in vitro with respect to 11 species (16 strains) of gram-positive and gram-negative bacteria and in vivo on albino mice with experimental salmonellosis or pneumococcal infections. The bacteria were either test cultures or isolates from patients. The studies showed that cefuroxime had a wide antibacterial spectrum in vitro. It inhibited the growth of Staph. aureus, Str. pneumoniae, E. coli, Salm. typhimurium, Kl. pneumoniae, Bac. subtilis and had no effect on Ps. aeruginosa, Pr. vulgaris, M. tuberculosis and M. fortuitum. Cefuroxime had also a high bacteriostatic effect with respect to the experimental pneumococcal infection and a lower bacteriostatic effect with respect to the experimental salmonellosis infection. 相似文献
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The segregation analysis is made of inheritance of the E factor of the Cattell's 16PF Questionnaire on the basis of a population sample consisting of 108 free-structured pedigrees. The possibility of major gene control of inheritance for this quantitative trait is confirmed. 相似文献