摘要:

AbstractMating type differentiation in Tetrahymena thermophila is known to regularly involve stable hereditary alterations at a single chromosomal locus in the somatic (macro)nucleus. This differentiation is directionally affected by the temperature at which new macronuclei develop after fertilization. We now report large and predictable effects of delayed refeeding of conjugating pairs upon mating type differentiation, particularly amongmat‐2homozygotes. The mating types whose frequency is affected the most are IV, VI, and VII, a set different from that most affected by temperature. We interpret our observations to reveal the existence of a second system which can participate in mating type differentiation, with different specificity from the system influenced by temperature under conditions of early refeeding of conjugating pairs. These observations enrich the phenomenology surrounding mating type differentiation in T thermophila and provide additional, easily controllable experimental conditions for the manipulation of mating type frequencie

ISSN:0192-253X    

DOI:10.1002/dvg.1020040302

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

年代:1983

数据来源: WILEY

摘要:

AbstractMouse trisomy 15 ⟷ 2n aggregation chimeras have been produced and analyzed at 19 days of gestation. We have found that these chimeras are viable and in most instances normal in external appearance, unlike trisomy (Ts)‐15 embryos which are severely growthretarded and die midway through gestation. Trisomic cells were found in all tissues of fetal chimeras, with proportions not significantly different from those of the controls in kidney, heart, liver, and brain, but significantly reduced in thymus and spleen. Ts‐15 cells do not, therefore, exhibit a proliferative advantage during fetal development of tissues susceptible to Ts‐15‐related lymphoid malignancies. However, the presence of Ts‐15 cells in the placenta may be associated with placental overgrowth. One fetus containing a monosomy 3 cell population was also observed, the first term fetal chimera with monosomic cells that has be

ISSN:0192-253X    

DOI:10.1002/dvg.1020040303

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

年代:1983

数据来源: WILEY

摘要:

AbstractDuring slime mold development, cells acquire the capacity to rapidly recapitulate morphogenesis in roughly a tenth the original time. When developing cells are disaggregated and refed, they completely loss this capacity in a rapid and synchronous step referred to as the “erasure event.” The erasure event sets in motion a program of dedifferentiation during which developmentally acquired functions are lost at different times. In this report, we describe the phenotype of HI4, which is a mutant partially defective in the dedifferentiation program but normal in all aspects of growth, morphogenesis, and rapid recapitulation. HI4 cells progress through the erasure event, losing in a relatively normal fashion (I) the capacity to rapidly recapitulate later stages of morphogenesis, (2) the capacity to release a cAMP signal, and (3) the capacity to respond chemotactically to a cAMP signal. However, erased HI4 cells abnormally retain the capacity to rapidly reaggregate, even though they have lost chemotactic functions. Erased HI4 cells also abnormally retain EDTA‐resistant cohesion (contact sites A) and the surface glycoprotein gp80. It appears that erased HI4 cells rapidly reaggregate owing to random collisions followed by tight cell coh

ISSN:0192-253X    

DOI:10.1002/dvg.1020040304

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

年代:1983

数据来源: WILEY

摘要:

AbstractA mutation or deficiency of the Enhancer of Polycomb(E(Pc))locus acts as a dominant enhancer of the adult mutant phenotypes of a group of similar homoeotic loci (Polycomb, Polycomblike, extra sex comb, and lethal(4)29). TheE(Pc)mutation has a recessive lethal effect, and homo‐ and hemizygotes die as late embryos or larvae which appear cuticularly normal.E(Pc)also acts as a dominant enhancer of the embryonic homoeotic syndromes associated with Polycomb. Polycomblike, and lethal(4)29 mutations: its effect on the extra sex comb syndrome has not been effectively evaluated. At least for the interaction with Polycomb mutations, evidence is presented that the Enhancer of Polycomb locus has a maternal as well as a zygotic effect, and that its effect on Polycomb expression is not at the level of transcription. We suggest that the Enhancer of Polycomb locus acts specifically to regulate the activities of this set of homoeotic loci, and thatE(Pc)recessive lethality results from noncuticular homoeotic defects which arise as a consequence of their reduced activity. In the context of this hypothesis, no present data allow us to distinguish whether Enhancer of Polycomb is a nonhomoeotic locus regulating the function(s) of Polycomb and related genes or is itself a homoeotic locu

ISSN:0192-253X    

DOI:10.1002/dvg.1020040305

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe question as to the role that genes play in determining life‐span is essentially unresolved. Although it is well documented that genotype influences longevity, this is no way demonstrates that life‐span is genetically determined. In the present study we examine five temperature‐sensitive mutations for their effect on the aging process. At the permissive temperature (22°C ), the longevity of each mutant strain is comparable to that of wild type. However, at the restrictive temperature (29°C ) the life‐span of these mutants is severely curtailed. Using behavior loss as a landmark of adult physiological age, we examined each of these strains for its pattern of behavior loss relative to longevity, and compared each to a wild‐type strain. In four of the mutations the pattern of behavior loss relative to longevity was severely altered at one or both temperatures. However, one strain,adl‐16tsldisplayed a pattern of behavior loss that was indistinguishable from wild type at both 22°C and 29°C. At 29°C not only was the longevity decreased, the pattern of behavior loss was also compressed into a shorter time period. The compression of the pattern of behavior loss was proportional to the reduction in life‐span. Thus it appears that this mutation,adl‐16tsl, may accelerate the normal aging process when placed at 29°C. The potential utility of these types of mutants for studying the aging

ISSN:0192-253X    

DOI:10.1002/dvg.1020040306

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe use of Drosophila as an organism in which to study aging has been limited by the fact that few biomarkers of aging exist in the adult. In this paper we examine behavior loss relative to longevity in wild‐type populations maintained at 22°C and 29°C to determine whether behavior loss—that is, loss of ability to perform certain innate behavioral responses within a defined test interval—can be used as biomarkers of aging. We find that under controlled conditions behavior loss can be used as a landmark of aging in populations maintained at either 22°C or 29°C. The ability to perform normal geotactic and phototactic responses is lost during the reproductive phase of the adult populations, whereas motor activity is not lost until well into the death phase. We feel that the use of behavior loss, together with other parameters of longevity in Drosophila, will allow comparisons to be made between different strains or between different environmental conditions to test their effect on aging. In the companion paper we demonstrate the use of behavior loss to identify a mutation which may accelerate the agin

ISSN:0192-253X    

DOI:10.1002/dvg.1020040307

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

年代:1983

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020040308

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

年代:1983

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020040301

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

年代:1983

数据来源: WILEY