摘要:

AbstractAn electrophoretic variant of the X‐linked enzyme phosphoglycerate kinase (PGK‐1) has been used to study regulation of X chromosome expression in the diploid derivatives of the trophectoderm at 8–8.5 days post coitum in the mouse. These derivatives included the chorionic ectoderm and the polar trophoblast. The biochemical analysis suggests that only the maternally derived X chromosome (Xm) is expressed in the diploid trophectoderm derivatives. Cell selection and maternal tissue contamination were ruled out as possible causes of the observed Xmexpression. From these and other results, we conclude that all derivatives of the trophectoderm, along with the primitive endoderm, express only Xm, whereas derivatives of the primitive ectoderm show random X chromosome expre

ISSN:0192-253X    

DOI:10.1002/dvg.1020010202

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe induction of multiple flagella by a heat shock was used to examine the role of RNA and protein synthesis in the regulation of the number of flagella produced during the differentiation of the amebo‐flagellate Naegleria gruberi. Control cells differentiating at 25.0°C produce an average of 2.1 flagella per flagellate (f/F), whereas cells exposed to 38.2°C from 35 minutes until 72 minutes after initiation produce an average of approximately 5 f/F. Heat shock was found to prevent completion of the RNA synthesis essential for flagellum formation, even though both RNA and protein synthesis continued at 38.2°C. A delay of two minutes for every one minute of heat shock was seen in both the formation of flagella (T50) and the completion of essential RNA synthesis for heat shocks of one to ten minutes applied beginning 35 minutes after initiation. Times at 38.2°C of ten minutes to 45 minutes produced a delay of approximately 0.6 minutes for each minute of heat shock, whereas shocks longer than 47 minutes prevented flagellum formation. The times from completion of RNA synthesis until completion of protein synthesis or flagella formation were found to be approximately 15 minutes and approximately 32 minutes, respectively. This was true in control cells as well as in cells heat shocked for up to 45 minutes. The fact that heat shock delayed completion of RNA synthesis without affecting the time for completion of protein synthesis or flagella formation suggests that heat shock acts at some step related to the completion of transcription. Short heat shocks, 30 seconds to five minutes, were observed to prevent flagellum formation in cells that had completed RNA synthesis if additional RNA synthesis was inhibited. In contrast, short heat shocks had little effect on cells that had completed protein synthesis, even if additional protein synthesis was inhibited. Two alternative hypotheses for the mechanism of heat shock delay of transcription are discussed. One hypothesis involves a direct effect of high temperature on transcription, and the other postulates a temperature‐sensitive protein necessary for flagellum fo

ISSN:0192-253X    

DOI:10.1002/dvg.1020010203

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe relationship between heterogeneous nuclear RNA (hnRNA) and messenger RNA (mRNA) synthesis has been studied as a function of the development of the sea urchin embryo through the use of methyl incorporation. Several parameters in the metabolism of capped hnRNA and mRNA of early blastula and late gastrula stages have been investigated by measuring the kinetics of transfer of methyl groups from S‐adenosylmethionine to the 5′ cap structures in nuclear and cytoplasmic RNA:1The rate constants for the decay of hnRNA caps and the synthesis of mRNA caps are equal to within experimental error. This equality indicates a flux of precursor hnRNA caps to mRNA caps with a very high degree of conservation of the hnRNA caps. This conservation holds for each embryonic stage.2From literature data on the labeling kinetics of GTP and mRNA, we have calculated the decay constant of a putative mRNA precursor component of hnRNA. The value of this constant is very close to that for the decay constant of hnRNA caps. Hence, all hnRNA caps and some portion of their associated hnRNA sequences behave kinetically as the pre‐mRNA fraction. This kinetically ascribed pre‐mRNA comprises approximately 30% of the hnRNA mass.3The part of the hnRNA which does not serve as precursor to mRNA turns over at least twice as rapidly as the pre‐mRNA fraction.4During development from early blastula to late gastrula, the rate of hnRNA cap synthesis drops from 2 × 103molecules/min/cell to half of this value. This decline is parallel to the decline in total hnRNA synthesis and thereby confirms the constant degree of capping of hnRNA, as previously reported. We infer that the pre‐mRNA fraction of hnRNA remains nearly constant during this developm

ISSN:0192-253X    

DOI:10.1002/dvg.1020010204

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

年代:1979

数据来源: WILEY

摘要:

AbstractThis study was conducted to assess microenvironmental variability within integumental tissue of genetically identical mice with respect to a specific cellular response: cyclic synthesis of yellow and black pigment by hair bulb melanocytes. Crosses were performed within and between inbred strains of mice that were isogenic with the exception of a single gene substitution at the agouti locus. Agouti locus genes included theAvy,Aw,A,atd,at,ax,am, andaalleles. The pigment patterns of dorsal, flank, and ventral hairs of the first and third hair generations and of hairs growing in special integumentary areas such as the pinna, tail, and hind foot were studied. It was found that the amount of yellow pigment synthesized by hair bulb melanocytes within genetically identical mice is both agedependent and conditioned by the integumentary environment. Furthermore, the special integumentary regions produce hairs with a variety of pigment patterns in which the distribution and relative amounts of black and yellow pigments do not necessarily conform to dominance relationships expected among agouti locus alleles as judged by their effects on the pigmentation of the dorsal pelage. We conclude that within genetically uniform integumental tissues, microenvironmental differences occur and are reflected as alterations in the metabolic pattern of differentiated cells.

ISSN:0192-253X    

DOI:10.1002/dvg.1020010205

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

年代:1979

数据来源: WILEY

摘要:

AbstractMild heat treatments applied to whole animals or cell cultures of Drosophila prior to lethal heat shocks result in increased survival and protection against phenocopy induction. The optimal condition for the preliminary mild heat treatment is that which induces the synthesis of heat‐shock proteins but does not turn off the protein synthesis that is in progress. Recovery of protein synthesis but not RNA synthesis following a drastic heat shock is much enhanced by the pretreatments. The results suggest that the protection for survival and against phenocopy induction is due to storage of messenger RN

ISSN:0192-253X    

DOI:10.1002/dvg.1020010206

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

年代:1979

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020010207

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

年代:1979

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020010201

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

年代:1979

数据来源: WILEY