ISSN:0192-253X    

DOI:10.1002/dvg.1020010102

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

年代:1979

数据来源: WILEY

摘要:

AbstractPolypeptides solubilized from established normal and variant cell lines of Nicotiana tabacum L cv “Wisconsin 38” have been analyzed by one‐dimensional and two‐dimensional gel electrophoresis. There was little variability observed in the polypeptide profile in an established cell line; polypeptides present in different clonal lines of cells, all derived from an initial established cell culture, were very similar, if not identical. However, a large fraction of the observed polypeptides present in cytokinin‐habituated cell lines (up to 3.8% of the total polypeptides analyzed by two‐dimensional gel electrophoresis) were different from those found in the cytokinin‐requiring cells from which they were selected. The habituated nature of the selected cell lines was demonstrated to be epigenetic; tissue cultures that were reisolated from plantlets regenerated from habituated cell lines did require cytokinin. Further observations demonstrate: (1) that epigenetic events that alter a cellular phenotype change the expression of a relatively large number of polypeptides, (2) that a single epigenetic phenotype may be the result of any one of a number of possible patterns of gene expression, and (3) that epigenetic events are not

ISSN:0192-253X    

DOI:10.1002/dvg.1020010103

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

年代:1979

数据来源: WILEY

摘要:

AbstractTwo compounds, ammonia (NH3) and 3′5′ cyclic AMP (cAMP) act as specific morphogens in regulating the development of Dictyostelium discoideum [1–11]. A previous study [12]demonstrated that NH3at concentrations that affect the course of morphogenesis completely inhibits the extracellular release of cAMP by aggregation competent cells incubated in shaken suspension. The present study extends this finding in two respects:1Exposure of aggregation competent cells to NH3(supplied as ammonium carbonate) is followed within a few minutes by the complete disappearance of intracellular cAMP. Subsequent removal of NH3is followed by a rapid, complete restoration of the level. Neither the disappearance nor the reappearance is affected by the presence of cycloheximide, an inhibitor of protein synthesis.2In a mutant strain of D discoideum, greatly increased sensitivity to NH3as a regulator of morphogenesis is coupled with a correspondingly increased sensitivity to NH3as an inhibitor of cAMP accumulation.These results are consistent with a recently proposed [13, 14] model of morphogenetic regulation that is based on the supposition that NH3, by inhibiting cAMP production, restricts cAMP accumulation to specified constrained areas within the developing multicellular aggregate and thereby dictates the course of morphogenesis and cytodifferenti

ISSN:0192-253X    

DOI:10.1002/dvg.1020010104

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

年代:1979

数据来源: WILEY

摘要:

AbstractParamecium tetraurelia, stock d113, although completely homozygous, produces two kinds of genomically identical clones: N (nondischarge) clones incapable of trichocyst exocytosis (discharge) from intact cells in response to picric acid; and D (discharge) clones that do respond. These alternatives are irreversibly determined (at 27°C) during a determination sensitive period the first day after fertilization (autogamy, conjugation, or cytogamy): D parents are always determined to produce D progeny; N parents produce mostly N progeny if kept in exhausted medium, but mostly D progeny if kept in bacterized nutrient medium, throughout the sensitive period. If connecting bridges between mates persist long after the time for pair separation, the N member of N×D conjugant and cytogamous pairs produces D progeny even if exposed to exhausted medium throughout the sensitive period, thus indicating the presence in D mates of a D‐determining cytoplasmic factor, δ, which overrides effects of external conditions. N and D determinations are brought about on newly developing somatic nuclei (macronuclear anlagen). After macronuclear development has been completed, determination is irreversible in it and its descendant macronuclei. M (mixed) clones produce N, D, and partial D cells; within these clones, diverse subclones can be selected. Crosses of d113 (N)×standard wild stock 51 (D) yield no segregation in F2, indicating no genomic difference between d113 (N) and wild type (D), δ may be a genic product regulating its own production. This results in “cytoplasmic inheritance” of D vs N in crosses of D×N followed by exhausted medium during the sensitive period. As with the only other well‐analyzed comparable example, mating types, neither a genetic nor an epigenetic interpretation has yet been excluded for this system of developmental di

ISSN:0192-253X    

DOI:10.1002/dvg.1020010105

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

年代:1979

数据来源: WILEY

摘要:

AbstractIn the heterothallic myxomycete Physarum polycephalum, uninucleate amoebae normally differentiate into syncytial plasmodia following heterotypic mating. In order to study the genetic control of this developmental process, mutations affecting the amoebal‐plasmodial transition have been sought. Numerous mutants characterized by self‐fertility have been isolated. The use of alkylating mutagens increases the mutant frequency over the spontaneous level but does not alter the mutant spectrum. Three spontaneous and 14 induced mutants have been analyzed genetically. In each, the mutation appears to be linked to the mating type locus. In three randomly selected mutants, the nuclear DNA content is the same in amoebae and plasmodia, indicating that amoebal syngamy does not precede plasmodium development in these strains. These results indicate that a highly specific type of mutational event, occurring close to or within the mating type locus, can abolish the requirement for syngamy normally associated with plasmodial differentiation. These mutations help define a genomic region regulating the switch from amoebal to plasmodial gro

ISSN:0192-253X    

DOI:10.1002/dvg.1020010106

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

年代:1979

数据来源: WILEY

摘要:

AbstractAbnormal spermiogenesis in sterile pink‐eyed dilution mutants results in spermatozoa with bizarre sperm heads. The spermatozoa of normal mice bind colloidal iron hydroxide (CIH) along the length of the tail, yet the spermatozoa of pink‐eyed sterile mice show a great reduction in ability to bind CIH. This implies a loss of negative surface charges. The group(s) responsible for the charges are sensitive to methylation but resistant to neuraminidase treatment, even after deacetylation with alkaline treatment. The membrane components containing the negatively charged groups may be neuraminidase‐resistant forms of ganglio

ISSN:0192-253X    

DOI:10.1002/dvg.1020010107

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

年代:1979

数据来源: WILEY

摘要:

AbstractMouse oocytes at the dictyate and metaphase II stages as well as fertilized eggs have been studied by indirect immunofluorescence for the expression of H‐2 histocompatibility antigens on surface membranes. Serologically specific reactivity to H‐2 antibody was observed as patchy fluorescence distributed over the surface of the oocyte membrane. In contrast, one‐cell zygotes exhibited variable reactivity, and early two‐cell stages were negative. Absorption studies confirmed the serologic specificity of the reactivity on oocytes, which could be shown to be due to H‐2 antibody. The results suggest that fertilization results in altered expression of major histocompatibility complex surface antigens, and confirms earlier studies that cleavage stage mouse embryos are not reactive with H

ISSN:0192-253X    

DOI:10.1002/dvg.1020010108

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

年代:1979

数据来源: WILEY

摘要:

AbstractPupae of Drosophila melanogaster were heat‐shocked under conditions required to induce phenocopies in more than 90% of the flies that subsequently emerge. The effects of these treatments on protein synthesis in two tissues (thoracic epithelium and brain) were followed for several hours after the heat treatments. Results from pulse‐labeling and protein separations on sodium dodecylsulfate (SDS) acrylamide gels showed a virtually complete cessation of protein synthesis immediately after the shock, followed by a noncoordinate resumption of the starting pattern. Similar experiments following double heat shocks demonstrated a more rapid resumption of synthesis of heat shock proteins after two successive heat treatments than after a single

ISSN:0192-253X    

DOI:10.1002/dvg.1020010109

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

年代:1979

数据来源: WILEY

摘要:

AbstractWe studied the maternal effect for two enzymes of the pentose cycle, 6‐phosphogluconate dehydrogenase (6PGD) and glucose‐6‐phosphate dehydrogenase (G6PD), using a genetic system based on the interaction ofPgd−andZw−alleles, which inactivate 6PGD and G6PD, respectively. The presence and formation of the enzymes was investigated in those individuals that had not received the corresponding genes from the mother. We revealed maternal forms of the enzymes, detectable up to the pupal stage. The activities of “maternal” 6PGD and G6PD per individual increased 20‐fold to 30‐fold from the egg stage to the 3rd larval instar even in the absence of normalPgdandZwgenes. Immunologic studies have shown that the increase in 6PGD activity is due to an accumulation of the maternal form of the enzyme molecules. We revealed a hybrid isozyme resulting from an aggregation of the subunits of isozymes controlled by the genes of the mother and embryo itself. These results indicate that the maternal effect in the case of 6PGD is due to a long‐lived stable mRNA transmitted with the egg cytoplasm and translated during the development of Dros

ISSN:0192-253X    

DOI:10.1002/dvg.1020010110

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

年代:1979

数据来源: WILEY

摘要:

AbstractAlkaline phosphatase is one of several enzymes that accumulate in a temporally regulated sequence during the development of Dictyostelium discoideum. These enzymes can be used to monitor specific gene expression; moreover, isolation and analysis of mutations in the structural gene(s) can serve to indicate some of the essential steps in programmed synthesis and morphogenesis. A mutation (alpA) which affects the activity and substrate affinity of alkaline phosphatase was isolated in D discoideum using a procedure for screening large numbers of clones. Alkaline phosphatase activity at all stages of vegetative growth and development was altered by the mutation. Several physical properties of the enzyme from growing cells and developed cells were compared and found to be indistinguishable. It is likely that a single enzyme is responsible for the majority of alkaline phosphatase activity in growth and development. The mutation is coexpressed in diploids heterozygous foralpA and maps to linkage group III. One of the haploid segregants isolated from these diploids carries convenient markers on each of the six defined linkage groups and can be used for linkage analysis of other genetic loci.

ISSN:0192-253X    

DOI:10.1002/dvg.1020010111

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

年代:1979

数据来源: WILEY