ISSN:0022-104X    

DOI:10.1002/jez.1402280202

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

年代:1983

数据来源: WILEY

摘要:

AbstractSoon after entering the genital ridge, mouse primordial germ cells take either a male or a female pathway of development. Which direction they follow, and how successful their subsequent gametogenesis turns out to be, depends on various factors, including their own genotype and the phenotype of the gonad they inhabit. Experimental situations that have helped to throw light on this problem include XX⟷XY chimeras, XO females, and mice carrying the sex‐reversed gene (Sxr). Further information can be obtained by studying germ cells that fail to enter the genital ridge, as well as culturing isolated germ ce

ISSN:0022-104X    

DOI:10.1002/jez.1402280203

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe differentiation of germ cells in the adrenal glands of 26 male and female Swiss albino mice was studied in sequential stages of development, from day 12½ of intrauterine life to postnatal day 21; the study was performed by means of high‐resolution light microscopy and electron microscopy. In 12½‐and 13‐day‐old embryos, the ectopic cells had morphologic characteristics typical of primordial germ cells, whereas in 14‐ and 15‐day‐old fetuses they were identifiable as oogonia. In male and female fetuses from day 17 to term, all ectopic germinal elements entered meiotic prophase, reached diplotene, and differentiated into oocytes in perfect adherence to mouse ovarian timetables. In the postnatal animals, females as well as males, all oocytes progressed through the postmeiotic phase of growth just as they normally do in ovarian follicles, and, in the 2‐ and 3‐week‐old animals, they displayed features identical to those exhibited by oocytes in large antral follicles, including a zona pellucida. Germinal elements were no longer seen in the adrenals of animals older than 3 weeks. Our study shows that mammalian germ cells are capable of developing even outside the gonads, and that in ectopic sites they all differentiate as oocytes irrespective

ISSN:0022-104X    

DOI:10.1002/jez.1402280204

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

年代:1983

数据来源: WILEY

摘要:

AbstractMammalian sperm normally fertilize eggs in the ampulla of the oviduct after a long trip through the female reproductive tract. During this trip, the sperm become capacitated to fertilize but must overcome substantial barriers in the form of egg investments before reaching the plasma membrane of the egg. Once inside the egg the head of the sperm responds to cytoplasmic factors to decondense and form a pronucleus. All the problems of sperm penetration of the egg and its investments can be circumvented by injecting the sperm into the egg with a micropipette. Such injected sperm can participate normally in the subsequent events, typical of fertilized eggs, that lead to the formation of embryos. Sperm can also be injected into normally fertilized eggs to produce a third pronucleus and a triploid embryo.To avoid the mechanical problems of capturing a swimming sperm with a micropipette, the sperm suspension can be sonicated to break off the sperm tails. The resulting sperm heads can easily be injected into unfertilized eggs to induce the normal events of fertilization. With these injection procedures it is possible to test the fertilizing capacity of foreign sperm, of defective sperm, and even of “dead” sperm. We have found that the phenotype of the sperm does not reflect the genotype in terms of fertilizing ability after microinjection. Immotile and grossly defective sperm of the mouse when injected into the egg produce the same reactions that are produced by fertilization with healthy robust sperm. Thus we conclude that the complex set of interactions normally required for sperm to penetrate the egg investments and to fertilize the egg are biologically unnecessary and can be circumvented by direct injection of the sperm into the

ISSN:0022-104X    

DOI:10.1002/jez.1402280205

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

年代:1983

数据来源: WILEY

摘要:

AbstractRecently, in several centers, there have been striking in creases in the pregnancy rates from human in vitro fertilization (IVF). Some of the improvements are 1) refinement and individualization of ovulation induction with clomiphene citrate and human menopausal gonadotropin and timing of hCG administration, aided by monitoring of plasma estradiol, cervical mucus characteristics, and follicle size and number; 2) preincubation of oocytes before insemination; 3) improvements in embryo transfer procedures, including smaller diameter catheters, smaller fluid volume, and the inclusion of a high proportion of serum in the transfer medium.Although there are still unresolved problems at all stages it would be of significant assistance to the induction and culture if a noninvasive monitor of oocyte maturity and health were available. The appearance of the living oocyte under the light microscope has proved of limited diagnostic value.With this aim in mind, the microscopic appearance of cumulus cells and follicular fluid protein levels have been assessed with respect to their usefulness in indirect oocyte assessment. Follicular fluid proteins from patients who had become pregnant after the transfer of a single embryo have been separated by broad spectrum pH isoelectric focusing. The complex band profiles were quantitated by laser beam densitometry.Statistical analyses of the results, grouped according to the performance of the oocyte and resulting embryo following IVF, indicate that there are differences between the groups in which the oocytes fertilized, cleaved, and produced pregnancies and those which did not. Further studies are underway to assess the predictive value of the individual isoelectric focusing profiles. Also being investigated is their possible usefulness in monitoring ovulation induction regimens.

ISSN:0022-104X    

DOI:10.1002/jez.1402280206

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe developing use of in vitro fertilization (IVF) as a human clinical procedure has prompted the exploitation of nonhuman primates to assess the chromosomal and biochemical normality of embryos produced by IVF. Of 1995 oocytes recovered from squirrel monkeys, 628 (31.5%) matured and 339 (54.0%) fertilized. Fertility can be significantly enhanced by the addition of 1 or 10 μM dbcAMP to the culture medium. Chromosome analysis of oocytes and embryos used in these studies revealed an incidence of abnormality between 7 and 25%, comparable with that found for both in vivo and in vitro fertilized embryos from other laboratory species. There is no evidence that the IVF technique increases chromosomal abnormality. There was a decrease in protein synthesis of oocytes at maturation and during the early embryonic development stages, but an increase in the rate of RNA synthesis as development progressed. There was steroid uptake in early preimplantation embryos. The temporal relationships of early embryonic developmental events in the squirrel monkey have been determined

ISSN:0022-104X    

DOI:10.1002/jez.1402280207

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

年代:1983

数据来源: WILEY

摘要:

AbstractInterspecific hybrids and chimeras in mammals provide unique tools for investigating problems in genetics and embryology, because of the degree of disparity between the two component genotypes. We have attempted to produce hybrids and chimeras betweenMus musculus, the laboratory mouse, andMus caroli, a wild species of mouse from Southeast Asia.M. musculusandM. carolido not normally interbreed, although sterile hybrids can be produced at a low rate by artificial insemination. Extrinsic problems of genotypic incompatibility between the fetus and the maternal environment seem to be involved in poor hybrid survival, sinceM. caroliblastocysts also die when transferred to theM. musculusuterus. Death is associated with the generation of maternal T‐cells which are cytotoxic toM. carolitarget cells in vitro. It is not yet clear whether this immune response is the primary cause of death or is secondary to breakdown of some other components of the fetal‐maternal interaction. It is clear, however, that it is the trophoblast layer that mediates survival or death of the foreign embryonic cells in theM. musculusjuterus, sinceM. caroliinner cell mass cells can survive to term after injection intoM. musculusblastocysts: Viable interspecific chimeras result. Even more convincing evidence is provided by the production of viableM. carolioffspring by trophoblast vesicle reconstitution using trophoblast ofM. musculusgenotype and inner‐cell mass ofM. carolitype. Studies of properties of isolated trophoblast tissues have indicated thatM. carolitrophoblast may differ fromM. musculusin both its antigenic and immunosuppressive properties. Elucidation of trophoblast‐uterine interactions in these various interspecific pregnancies is being aided by the development of an in situ marker system, which can distinguish cells of the two species in sectioned material by in situ hybridization with aM. musculussatellite DNA probe. This same marker is also proving a very powerful tool for analyzing cell lineage development in c

ISSN:0022-104X    

DOI:10.1002/jez.1402280208

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

年代:1983

数据来源: WILEY

摘要:

AbstractNormal growth and differentiation of mammalian embryos in vitro during the preimplantation period appear to be dependent upon the availability of appropriate metabolic substrates. For preimplantation embryos, defined conditions of culture have been achieved only in a few laboratory species. There is now evidence that differentiation factors isolated from fetal calf serum and human placental cord serum may promote further development of blastocysts. Postimplantation rat and mouse embryos can be cultured during the organogenesis period with rat or human sera in roller bottles. The embryonic differentiation of the rat at this stage of development is progressively retarded in such cultures with male rat serum. The embryonic development is not improved, even in sera obtained from rats at different days of gestation (12, 15–16, and 20–21). Inability to grow placental tissues simultaneously with embryos, accumulation of unfavorable substances, and rapid depletion of nutrients contribute to the retardation of embryonic growth. To improve growth and differentiation of conceptuses, a continuous culture system with the possibility of infusion of increasing concentrations of oxygen in the roller bottle gas atmosphere has been developed. This improved method allows considerable continuous growth and differentiation from the neurula stage with development of numerous primary organs.Utilizing these in vitro culture methods during pre‐ and postimplantation periods, it is now possible to assess embryotoxic or teratogenic potential of drugs and chemical agents. The postimplantation culture procedure allows a more precise assessment of mechanisms associated with anomalous embryonic differentiation. Bioactivation of teratogens and effects of active toxic metabolites on organ primordium differentiation have been shown by combining embryo culture with a hepatic microsomal activating system. Microinjection of teratogens and cells into conceptus compartments is being used to elucidate specific anomalous differentiation proc

ISSN:0022-104X    

DOI:10.1002/jez.1402280209

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

年代:1983

数据来源: WILEY

摘要:

AbstractMany questions related to the development and the phenotypic expression of trisomy (Ts) are amenable to systematic investigation in a mouse model that allows the induction of Ts 1 to 19 by a breeding design of mice heterozygous for Robertsonian metacentric chromosomes. Some Ts do not survive the first critical phase of organogenesis on days 11 to 12 of fetal development; others as Ts 12, 14, 16, 18, and 19, have a life span until or beyond birth. Model type studies of the morphogenesis of developmental anomalies (e.g. craniocerebral, cardiovascular, or placental) are possible in Ts with a longer developmental span, and Ts 16 of the mouse is considered as a natural model of human trisomy 21. The eventual breakdown and death of the trisomic organism are inevitable. There is considerable interest to find ways for rescue and longer survival of Ts in competitive developmental systems, as e.g., in Ts ⟷ 2n blastocyst chimeras, or by isolation of trisomic cellular or tissue systems. Thus, the transfer of Ts hemopoietic stem cells of the fetal liver to irradiated adult recipients is a means of studying the functional capacities and maturation of trisomic hemopoiesis and lymphopoiesis. Both are almost completely restored by Ts 12, 14, 18, and 19 stem cell transplantation with survival periods of more than 6 months. But in other Ts, as of chromosomes 13 or 16, such capacity of reconstitution is impaired. The stepwise analysis of the effects of chromosome triplication on the cell level, in isolated functional systems and in the embryonic organism, is a promising way to understand the phenotypic expression of genome anomalies in complex developmental processe

ISSN:0022-104X    

DOI:10.1002/jez.1402280210

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe single active X principle has served for two decades as a focal point for research on the cyclic activation and inactivation of gene loci. Differences in X chromosome inactivation patterns of eutherian and marsupial mammals provide probes for investigating the mechanisms of the X inactivation process.In eutherian mammals, the X chromosome is inactivated early in meiotic prophase in males and remains inactive throughout the rest of spermatogenesis. During meiosis in females, the inactive X chromosome is activated so that both X chromosomes are active in oocytes. During the early cleavage divisions of female embryos, the paternally derived X is activated. It and the maternally derived X remain active until differentiation begins in early embryogenesis. At that time, the paternally derived X is inactivated in cells that give rise to extraembryonic membranes, whereas a random process determines which X chromosome is inactivated in cells that give rise to the embryo itself.Although less is known about developmental aspects of X inactivation in female marsupials, it is clear that the paternal X is preferentially inactive in postembryonic somatic cells. Furthermore, the paternal X is partially active at some loci in some cell types, indicating that it is not regulated as a single unit. The successful adaptation of a small (80–150 g), fecund marsupial to simple laboratory conditions now enables extensive experimentation on the large number of marsupials at various developmental stages. This capability, coupled with the application of newly developed cellular and molecular techniques to questions about X chromosome inactivation, shows great promise for advancing our understanding of the mechanisms that control the cyclic behavior of X chromosome activit

ISSN:0022-104X    

DOI:10.1002/jez.1402280211

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

年代:1983

数据来源: WILEY