Morphological Appraisal of Gametogenesis. Spermatogenetic Process in Mammals with Particular Reference to Man

Abstract

Consequently, a new terminology has arisen. It is used by different authors, in different languages, so that in context it has a different and sometimes opposite meaning to the old more classical nomenclature. Even if problems still remain to be clarified before a definitive understanding of the spermatogenic process is reached, the terminology should be standardized at least for the purpose of teaching students in the medical and allied areas. At the same time this would allow incorporation of the new advances that research in this field provides.although not exhaustive, aims at: 1. surveying of current concepts 2. compiling of the more important facts and problems 3. and thus facilitating discussion among those interested in this area of research.In the classical literature, the term "spermatogenesis" designates the development of the primordial germ cells of the embryo up to the late spermatids which are released by the germinal epithelium in the adult seminiferous tubules (spermiation). The concept of the continuity of spermatogenesis and what we consider to be a useful nomenclature are presented in Fig. 1. Many of the steps are tentative because of the present lack of adequate knowledge. Thus, this schematization should be regarded as an operational proposition to stimulate further research and discussion.Today, most text-books use the word "spermatogenesis" to imply the proliferation, maturation and differentiation of the germinal cells in the adult. For the English-speaking authors, spermatogenesis is thus the sperm production after puberty, comprising spermatocytogenesis, meiosis and spermiogenesis (Bloom and Fawcett -1968). Most of the problems in terminology arise from the fact that information concerning the development of the germinal cells in the prenatal and prepuberal stages is scarce. Authors dealing with this particular field of research have advanced new terms, for example, Hilscher (1973) speaks of: 1. Pregonadic stage, up to the migration of the primordial germ cells into the gonadal anlage, 2. Prespermatogenesis up to the appearance The present review on mammalian, including human, spermatogenic processes,

Testicular x-ray irradiation in adult mice as a model to study spermatogonial proliferation

“…Before this period, the seminiferous epithelium is formed by Sertoli cells (which end their mitotic activity just before entering into sexual maturation) and type-A spermatogonia. At puberty, and due to many factors not yet fully understood, the pattern of spermatogonial renewal and proliferation, followed by spermatogenic differentiation ensues, as is characteristic of complete (adult) spermatogenesis (Bustos-Obregon et al, 1975). The effect of irradiation upon full spermatogenesis has been addressed by many authors (in the rat : Dym & Clermont, 1967;Pineau et al, 1989; in mice : Oakberg, 1956: Oakberg, , 1959Bustos-Obregon & Rodriguez, 1990).…”

Monosaccharide Transport Across Membranes of Human Spermatozoa

“…pmoles/h in 10' cells, that means in 2,6 mm3. This could correspond to an intracellular D-fructose concentration of 4,6 mM after incubation of the native semen (with D-fructose concentration of 20 mM) for 4 h at 37' C. Since on the one hand a part of D-fructose is metabolized (this would reduce the intracellular D-fructose concentration) and on the other hand a part of the intracellular space is occupied for instance by condensed nucleoproteins (Bustos -Obregon et al -1975) and is also not available for D-fructose it is not possible to calculate the true intracellular D-fructose concentration at the present time.…”

Cytokinesis in development and disease: variations on a common theme

“…If erythroblast enucleation truly uses the same physical mechanism as that in cytokinesis, the control of this mechanism must be quite different from the common pathways described above, as this process is independent of microtubules and is not coupled with chromosome segregation. In addition to erythrocyte enucleation, programmed removal of other major cellular parts also occurs in specialized developmental programs, such as the process of residual body detachment during sperm maturation, where a major portion of the cytoplasm, as opposed to the nucleus, is discarded [149] (Fig. 5).…”