A major question is why are there only two types of gametes (sperm- and egg cells), two types of sex steroids, (androgens and estrogens in vertebrates, and two types of ecdysteroids in insects), while the reproduction-related behaviour of the gamete producers displays a much greater ...
摘要: Rene Almeling examines the medical market for eggs and sperm in the United States - how it is organized and how it influences and is experienced by donors.关键词:eggs sperm in vitro fertilization commodification egg donor sperm donor ...
Electrofusion-mediated in vitro fertilization of maize using single sperm and egg cells was performed. Sperm cells were released from pollen grains after r... E Kranz,J Bautor,H L?Rz - 《Sexual Plant Reproduction》 被引量: 396发表: 1991年 加载更多来源...
The synthesis of the only egg-specific molecules in initially male lateral body halves means that the long-term cloning results in the total repression of genes encoding sperm-specific proteins, since genetically male determinant-bearing cells can randomly re-express the testis characteristic as ...
Electrofusion-mediated in vitro fertilization of maize using single sperm and egg cells was performed. Sperm cells were released from pollen grains after r... E Kranz,J Bautor,H L?Rz - 《Sexual Plant Reproduction》 被引量: 396发表: 1991年 Requirement of extracellular calcium ions for various...
Here we studied a population of fowl, Gallus gallus, to gain longitudinal data on a sexual ornament (the comb), quantity of gametes produced, and gamete quality (sperm velocity and egg mass) of males and females. Our results reveal pronounced differences between the sexes in age-specific ...
The sexual agglutination factor on Hansenula wingei Y-2340 type 5 cells (5-agglutinin) was purified by affinity chromatography and gel filtration after its... PH Yen,CE Ballou - 《Biochemistry》 被引量: 114发表: 1974年 Characterization of the sperm-binding protein from sea urchin egg surface ...
Research on seminal fluid proteins is providing fundamental insights into the interactive evolution of male and female reproductive strategies. Two new studies demonstrate, first, how an influential male sex peptide in Drosophila is delivered to the female bound directly onto sperm cells, and second, ...
Sexual reproduction crucially depends on the production of sperm in males and oocytes in females. Both types of gamete arise from the same precursor, the germ cells. We review the events that characterize the development of germ cells during fetal life as they commit to, and prepare for, oogen...
Discusses several scientific breakthroughs in 1999, focusing on the extraordinary potential of stem cells to heal many kinds of illness. Types of stem cell... Vogel,Gretchen - 《Science》 被引量: 104发表: 1999年 A Question of Life: The Warnock Report on Human Fertilisation and Embryology In ...