摘要:

AbstractRecombinant DNA and hybridization techniques have been used to compare the organization of mitochondrial DNA (mtDNA) from normal (N) and Texas male sterile (T) cytoplasms of maize.BamH1 restriction fragments of normal mtDNA were cloned and used in molecular hybridizations against Southern blots ofBamH1 digested N and T mtDNA. Fifteen of the 35 fragments were conserved in both N and T as indicated by hybridization to comigrating bands in their restriction patterns. Only three fragments produced autoradiographs whose differences could reasonably be attributed to single changes in the cleavage site of the enzyme while approximately half (17/35) of the clones resulted in more complicated differences between N and T. The autoradiographs produced by these 17 clones indicated multiple cleavage site changes and/or sequence rearrangements of the mtDNA. Patterns of six of these 17 clones indicated partial duplication of the sequence and two showed variation in the intensity of hybridization between N and T, which may be related to the molecular heterogeneity phenomenon found in maize mitochondrial genomes. The large proportion of changes observed between N and T mtDNA indicates that rearrangements may have played an important role in the evolution of the maize mitochondrial genome.

ISSN:0192-253X    

DOI:10.1002/dvg.1020020402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractAttachment of the cell surface to a substratum may play a critical role in initiating some cellular developmental commitments and in sustaining differentiation of cells that have already been specialized. Embryoid bodies of teratoma OTT6050 were divided, on day 10 of initial culture, into myogenic adhesive cells which were already (at day 6) characterized by endogenous prostaglandin (PG)I2formation and little‐specialized suspensive cells which formed only thromboxane (TX)B2in the same culture system. Since at day 10 both cell types reached a stationary phase in which the nature of each cell was mature enough for the analyses with mass fragmentographic technique and gas chromatography‐ mass spectrometry (GCMS), the total levels of predominant long‐chain fatty acyl CoA (acyl CoA) derivatives could be measured comparatively as methyl esters after methanolysis. It was found as a result of major differentiation that adhesive cells had a rather low ratio of arachidonyl CoA to stearyl CoA, although adhesive cells accumulated a larger total amount of acyl CoA derivatives than that accumulated in suspensive

ISSN:0192-253X    

DOI:10.1002/dvg.1020020403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractAlleles at the agouti locus determines the type of pigment produced in hair‐bulb melanocytes. In order to analyze the mechanism of agouti gene function, an attempt was made to induce the shift in melanin synthesis in vitro. Skin explants from newborn yellow mice with genotypeAy/awere cultured with the method using membrane‐filter and roller tube. Production of black pigment in the hair bulbs was observed when the explants were cultured in the presence of α‐melanocyte stimulating hormone (α‐MSH). Electron‐microscopic observation indicates that the induced black pigments are eumelanin that is normally found in hair‐bulb melanocytes of genotypically black mice. The eumelanin synthesis was also induced by cAMP, DbcAMP, or theophylline. This α‐MSH‐induced eumelanin synthesis was suppressed by actinomycin D or cycloheximide, suggesting that the α‐MSH‐induced eumelanogenesis requires de novo transcrip

ISSN:0192-253X    

DOI:10.1002/dvg.1020020404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractHybrids between species frequently arrest early in development. In the frog hybrid Rana catesbeiana female × Rana clamitans male, the embryo shows a characteristic development to an exogastrula which dies. This hybrid can be rescued by pressure suppression of the second polar body, which results in the addition of another haploid set of R catesbeiana chromosomes to the embryo. The triploid hybrid expresses genes from both species and can develop normally through metamorphosis. The results show that an R catesbeiana egg containing a full haploid set of R clamitans chromosomes is capable of development and that the usual developmental arrest caused by the R clamitans genome responds to chromosomal dosage

ISSN:0192-253X    

DOI:10.1002/dvg.1020020405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractForty aggregation‐deficient mutants of Dictyostelium discoideum were screened for changes in intracellular cAMP during the first 10 hr of starvation. The pools in 39 of the mutants remained low and relatively static during this period. However, amoebae of one mutant, strain HC151, exhibited significantly elevated levels of intracellular cAMP during vegetative growth and for several hours after starvation. A more detailed analysis of this mutant indicated that the elevated cAMP pools in these cells are a consequence of the premature appearance and partial activation of an adenylate cyclase. The mutation(s) altering adenylate cyclase regulation in this strain appears to map in linkage group IV. Complementation tests between strain HC151 and another mutant, HH201, which has recently been shown to produce an adenylate cyclase activity precociously [1], indicated that the mutations affecting adenylate cyclase activity in these strains map at different loci. Although both of these mutations behave recessively in heterozygous diploids with respect to gross development, an examination of early cAMP metabolism and terminal spore differentiation in these diploids suggest that these mutations are at least partially expressed during some stage(s) of the developmental cycl

ISSN:0192-253X    

DOI:10.1002/dvg.1020020406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThe past decade has seen an explosion of interest in mammalian embryos. Techniques of molecular and genetic analysis coupled with advances in in vitro culture and experimental manipulation of mammalian embryos have provided important insights into mechanisms of embryogenesis. Many of these recent advances have been facilitated by the use of allelic isozyme variants as autonomous cell markers or representative gene products. Investigations aimed at exploring cell lineages and cell commitment, the timing and regulation of gene expression, X chromosome inactivation, and cell interactions have depended on the availability of appropriate isozyme variants. Results from such experiments are summarized here in order to demonstrate the usefulness of this approach and to stimulate its wider application in developmental biology.

ISSN:0192-253X    

DOI:10.1002/dvg.1020020407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020020401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY