ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37501.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37502.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37503.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Among physiological systems, that of reproduction in females probably shows greater variation in functional activity during life than any other. In our own species, the reproductive lifespan begins at menarche and ends at menopause, a span averaging 36 years in Western countries.1Reproductive potential reaches a peak value after a short period of postpubertal maturation, but steadily declines during the fourth and fifth decades of life2,3and is lost irretrievably when ovarian cycles cease at about age 50.4The effects of maternal age on fecundity and fertility are complex and multifactorial, involving a progressive depletion of the ovarian follicular store, production of defective oocytes, and reduced competence of the organs and systems required to sustain gestation successfully. Inbred rodents have been studied extensively to assess the relative weight of these factors because they are inexpensive, have a lifespan of only 2–3.5 years, and offer opportunities to identify hierarchical responsibility in aging by heterochronic organ transplantation. In the following sections the effects of aging on three variables affecting reproduction at late ages are described. The CBA mouse has been chosen as the principal model since reproductive life in this animal is completed within a year of ag

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37504.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The early development of the mammal appears to be directed by an intrinsically programmed and autonomously regulated series of molecular and cellular changes. The notion that an autonomous program directs early mammalian development implies that the information for and orchestration of early ontogeny is contained within the oocyte and early embryo. The expression of an intrinsic program can be envisaged to function in the progressive acquisition of “developmental states of readiness.” During oogenesis these states include competence to reinitiate arrested meiosis in the fully grown oocyte and fertilizability resulting from preovulatory maturation. In the preimplantation stages, such a program would be expected first to specify cell potentials (labile developmental options such as generation of a population of inside and outside cells in space and time1) and subsequently to limit the expression of developmental options by commitment to specific and stable cell form, fate, or function. The state of readiness attained at the blastocyst stage represents the ability of the embryo to initiate implantation as a consequence of delineation of inner cell mass and trophectoderm. This paper examines the nature of an intrinsic developmental program and addresses the question of the extent to which expression is regulated at the genomic or extragenomic le

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37505.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37506.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

During the last several years, the study of the nucleolus and, more specifically, its structure has been the object of much research.1The observation of the state of the nucleolus, its composition, and its spatial organization allows us to appreciate the synthesis and metabolism of ribonucleic acids (rRNA).Vacuoles have been observed in the nucleolus in some cells, such as those of cotton fibers2the embryonic root cells of Zea Mays,3tobacco cells,4and so on. This is also the case in oocytes, for instance, inXenopus5and in the teleost fish,Xiphophorus helleri.6The rat oocytes from antral follicle often have germinal vesicles possessing spherical inclusions. With mature rats, Tsafiri and Kraicer7have noticed these formations in 91% of the nucleoli. We have also found them in nearly all oocytes from adult rats, but not in those from prepubertal untreated rats.8Bomsel‐Helmreichet al.9have published illustrations showing that these cavities can be clearly distinguished at the interior of very large nucleoli belonging to human oocytes in mature ovarian follicles.To our knowledge, the origin, development and significance of these nucleolar vesicles have not yet been established with certaint

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37507.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37508.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37509.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0077-8923    

DOI:10.1111/j.1749-6632.1985.tb37510.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY