Germ Cell Development And Reproductive Aging

An exploration of germ cell development, division, disruption and death, designed for reproductive endocrinologists, microbiologists and physiologists. Topics covered include: cloning and characterization of genes expressed in germ cell lines; spermatological transplantation; and testicular ageing.

THE FASCINATION The male germ cell is the only cell of the human organism that leaves the body when it has achieved its final, highly sophisticated structure and properties. The male germ cell is designed for one purpose only: to reach the female gametes and to fertilize them. The various stages in the development of the male germ cell are characterized by proliferative phases, by the recombination of the maternal and paternal chromosomes, and by the differentiation and development of a specialized transport vehicle, the spermato zoon. Furthermore, the establishment of a special pool of stem cells, the spermatogonia, guarantees the continuity of the sperm-generation process from puberty to old age. THE FATE OF THE MALE GERM CELL The destiny of any individual germ cell is determined by a program that we know only in fragments. On the one hand every human male is able to produce many billions of germ cells in his lifetime, yet the chance of any single sperm reaching and fertilizing the female germ cell is exceedingly rare. A fertility disturbance means that somewhere during the complicated playing out of the germ cell program mistakes are made, and the program fails. It is still a fact that more than 50% of men presenting with male factor infertility have to be diagnosed as idiopathic, largely because of our lack of knowledge and conse quent lack of appropriate diagnostic tools.

The study of germ cells has undergone enormous advances in recent years and has entered into an explosive phase of new discoveries with the introd- tion of transgenic technologies and nuclear cloning. Basic knowledge and te- niques developed for lower vertebrate and invertebrate systems have facilitated the study of higher vertebrates, including humans. Many experiments that have first been performed on lower vertebrates provided the tools and strategies that could later be applied to other less readily available mammalian systems. The discovery of centrosomes in ascidians and sea urchin eggs now benefits st- ies of fertility and infertility in mammals including humans. External in vitro fertilization, now a common technique in assisted fertilization has only been possible as a result of numerous studies in lower systems in which external fertilization is natural. Egg activation, first explored in sea urchin and asc- ian eggs, now benefits cloning efficiency in farm and domestic animals. Gene manipulations and molecular methods have added to the possibilities of p- ducing live offspring with enormous biomedical, ecological, and economic implications. All sexually reproducing organisms produce primordial germ cells, a small population of cells that differentiate into gametes of either sex that carry to- potency, an ability to develop into an entire new organism. The two volumes on germ cells combine techniques in a variety of different systems and have selected those systems that have provided landmarks in advancing our kno- edge on germ cells.

All sexually reproducing organisms produce primordial germ cells, a small population of cells that differentiate into gametes of either sex and carry to- potency, an ability to develop into an entire new organism. The study of germ cells has undergone enormous advances in recent years and has entered into an explosive phase of new discoveries with the introduction of transgenic te- nologies and nuclear cloning. Basic knowledge and techniques developed for lower vertebrate and invertebrate systems have facilitated the study of higher vertebrates, including humans. Many experiments that have first been performed on lower vertebrates provided the tools and strategies that could later be applied to other less readily available mammalian systems. The discovery of centrosomes in ascidians and sea urchin eggs now benefits studies of fertility and infertility in mammals. External in vitro fertilization, now a common technique in assisted fertilization, has only been possible as a result of numerous studies in lower systems in which external fertilization is natural. Egg activation, first explored in sea urchin and ascidian eggs, now benefits techniques designed to increase cl- ing efficiency in farm and domestic animals. Gene manipulations and molecular methods have added to the possibilities of producing live offspring with en- mous biomedical, ecological, and economic implications. The two volumes on germ cells combine techniques in a variety of d- ferent systems; we have selected those systems that have provided landmarks in advancing our knowledge on germ cells.

All sexually reproducing organisms produce primordial germ cells, a small population of cells that differentiate into gametes of either sex and carry to- potency, an ability to develop into an entire new organism. The study of germ cells has undergone enormous advances in recent years and has entered into an explosive phase of new discoveries with the introduction of transgenic te- nologies and nuclear cloning. Basic knowledge and techniques developed for lower vertebrate and invertebrate systems have facilitated the study of higher vertebrates, including humans. Many experiments that have first been performed on lower vertebrates provided the tools and strategies that could later be applied to other less readily available mammalian systems. The discovery of centrosomes in ascidians and sea urchin eggs now benefits studies of fertility and infertility in mammals. External in vitro fertilization, now a common technique in assisted fertilization, has only been possible as a result of numerous studies in lower systems in which external fertilization is natural. Egg activation, first explored in sea urchin and ascidian eggs, now benefits techniques designed to increase cl- ing efficiency in farm and domestic animals. Gene manipulations and molecular methods have added to the possibilities of producing live offspring with en- mous biomedical, ecological, and economic implications. The two volumes on germ cells combine techniques in a variety of d- ferent systems; we have selected those systems that have provided landmarks in advancing our knowledge on germ cells.