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Diploid embryos which are homozygous for the t12 mutation die at the morula stage. In the current studies, ova from heterozygous () females were fertilized in vitro with spermatozoa from males. The fertilized ova were immediately placed into media containing cytochalasin B to prevent second polar body formation, producing +/+/+, +/+/t12, +/t12/t12, and t12/t12/t12 embryos. The subsequent development of these triploid embryos was compared with that of diploid +/+, , and embryos developing from ova which were also fertilized in vitro with spermatozoa from males but which were not treated with cytochalasin B immediately following gamete coincubation. The data show that those triploid embryos which possess a wild-type allele and two mutant alleles are phenotypically wild type while those possessing three mutant alleles are not phenotypically distinguishable from their diploid () counterparts. Like embryos, t12/t12/t12 embryos die at the morula stage, prior to blastocoelic cavity formation. 相似文献
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Mutations at the bithoraxoid (bxd) and postbithorax (pbx) loci cause a transformation of posterior haltere to posterior wing. It has previously been shown that pbx and cause this transformation by affecting the maintenance (or cell heredity function) of determination so that the transformed cells are indistinguishable from normal wing cells, and have no “memory” of having been part of a haltere disk (Adler, 1978a). I report here that Tp(3) and bxd1, pbx, ew both cause the transformation of posterior haltere to posterior wing in the same way as pbx. On the other hand, bxd1, , bxd51j, , and cause this same transformation of posterior haltere to posterior wing by interfering with the expression of the determined state so that the developmental information of posterior haltere is “misread” as posterior wing. The transformed cells in these disks retain the memory of having been part of a haltere disk; that is, these posterior cells that would secrete wing cuticle during metamorphosis regenerate anterior haltere structures. Thus it appears clear that it is possible to uncouple the expression and cell heredity functions of determination in the haltere disk of Drosophila. 相似文献
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It is shown that biased answers are given by the mathematical method used by Stein and his colleagues (Hankin B. L. Hankin, W. R. Lieb, and W. D. Stein (1972)Biochim. Biophys. Acta288, 114–126) to calculate , the half-saturation concentration for the entry of glucose into erythrocytes in infinite-cis conditions. A method for calculating accurately is described and tested. The published estimates of are low; nevertheless, even when they are revised upwards, the asymmetrical carrier model of glucose transport still fails to satisfy the “rejection criteria” of Hankin et al. (1972). 相似文献
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The dual wavelength assay technique (H. R. Levy, and G. H. Daouk, 1979, J. Biol. Chem.254, 4843–4847) is used to examine the rates of the NADP- and NAD-linked reactions of Leuconostoc mesenteroides glucose 6-phosphate dehydrogenase simultaneously under various conditions. Inhibition by ATP, MgATP2?, acetyl-CoA, and palmitoyl-CoA is greatly diminished at high glucose 6-P concentration which favors the NAD-linked reaction. Increasing concentration ratios inhibit the NADP-linked, but stimulate the NAD-linked reaction. The selective effects of glucose 6-P and the concentration ratio, which cannot be detected by conventional assays, are explained in terms of the differing kinetic mechanisms for the NADP-linked and NAD-linked reactions previously described (C. Olive, M. E. Geroch, and H. R. Levy, 1971, J. Biol. Chem.246, 2047–2057). It is proposed that these effects constitute the mechanism whereby the nucleotide specificity of the amphibolic glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides is regulated. 相似文献
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Lo-Sheng Dai 《Mathematical biosciences》1982,61(2):267-277
Edelstein's model , , , , where τ ? 0 and ?∞<s<∞, m ? 2, describes the behavior of two basic chemical species during the cellular differentiation in a linear ensemble of the same cell type. We prove the existence and uniqueness of a travelling-wavefront solution. We also demonstrate one kind of stability for this solution. 相似文献
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Susan E. Lewis 《Developmental biology》1978,65(2):553-557
This report describes the phenotype of the c25H lethal homozygote. Our studies have shown that embryos homozygous for c25H fail to implant and to induce a decidual reaction. Embryos arrested at the three- to six-cell stage were considered to be c25H homozygotes because of their homogeneous stage of arrest and because they were present in the appropriate proportion in preimplantation litters from matings. Mitosis appeared to be disturbed in the arrested embryos. 相似文献
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