Showing papers on "Sperm plasma membrane published in 1981"

Sperm morphogenesis in wild-type and fertilization-defective mutants of Caenorhabditis elegans.

Abstract: Taking advantage of conditions that allow spermatogenesis in vitro, the timing and sequence of morphological changes leading from the primary spermatocyte to the spermatozoon is described by light and electron microscopy. Together with previous studies, this allows a detailed description of the nuclear, cytoplasmic, and membrane changes occurring during spermatozoan morphogenesis. By comparison with wild type, abnormalities in spermatogenesis leading to aberrant infertile spermatozoa are found in six fertilization-defective (fer) mutants. In fer-1 mutant males, spermatids appear normal, but during spermiogenesis membranous organelles (MO) fail to fuse with the sperm plasma membrane and a short, though motile. pseudopod is formed. In fer-2, fer-3, and fer-4 mutants, spermatids accumulate 48-nm tubules around their nuclei where the centriole and an RNA containing perinuclear halo would normally be. In all three mutants, spermatids still activate to spermatozoa with normal fusion of their MOs, but the pseudopods formed are aberrant in most fer-2 and fer-4 spermatozoa and in some fer-3 spermatozoa. In fer-5 mutant males, spermatozoa do not form. Instead, defective spermatids with crystalline inclusions and abnormal internal laminar membranes accumulate. In fer-6 mutant males, only a few spermatozoa form and these have defective pseudopods. These spermatozoa retain their fibrous bodies, a structure which normally disassembles in the spermatid. The time of appearance of developmental abnormalities in all of these mutants correlates with the temperature-sensitive periods for development of infertility. The observation that each of these mutants has a different and discreet set of morphological defects, a structure which normally disassembles in the spermatid. The time of appearance of developmental abnormalities in all of these mutants correlates with the temperature-sensitive periods for development of infertility. The observation that each of these mutants has a different and discreet set of morphological defects, a structure which normally disassembles in the spermatid. The time of appearance of developmental abnormalities in all of these mutants correlates with the temperature-sensitive periods for development of infertility. The observation that each of these mutants has a different and discreet set of morphological defects shows that the strict sequence of morphogenetic events that occurs during wild-type spermatogenesis cannot arise because each event is dependent on previous events. Instead, spermatozoa, like bacteriophages, must be formed by multiple independent pathways of morphogenesis.

Gamete Interaction in the Sea Urchin A Model for Understanding the Molecular Details of Animal Fertilization

Abstract: Fertilization is the fusion of a sperm with an egg, resulting in the restoration of the diploid condition and the activation of the metabolically dormant egg, setting the zygote on the pathway to cleavage, organogenesis, and formation of an adult. Fertilization has been studied extensively for over 100 years because of curiosity about the mechanism that gives rise to a new generation. More recently, research on fertilization has become important because of the obvious applications to problems of fertility control. Fertilization also provides an excellent model system to study a variety of cellular phenomena. It is particularly useful as a model for studying cell adhesion and membrane fusion. Fertilization is a rare example of a natural fusion of the plasma membranes of two cells (reviewed in Epel and Vacquier 1978; others are myoblast fusion and fusion of placental trophoblast cells). In addition to the fusion of two plasma membranes, there are two exocytotic events associated with fertilization. One is the fusion of the sperm acrosome granule membrane with the overlying sperm plasma membrane; the second is the massive exocytosis of egg cortical granules seconds after sperm-egg fusion (Epel and Vacquier, 1978). Finally, fertilization is also an excellent model for the study of the biochemical activation of two cells. The sperm undergoes an activation in response to the external egg investments, involving ion fluxes, an increase in respiration, and a change in cell shape involving the polymerization of actin (Tilney et al., 1973). The egg undergoes a dramatic metabolic activation, involving a variety of physiological changes such as ion fluxes, membrane fluidity changes, a membrane depolarization, increases in nucleoside and amino acid transport, and a marked increase in macromolecular synthesis (Epel, 1978).