细胞功能测定

The union between sperm and oocyte is species-specific, and the courses of events that follow are some of the most dramatic surrounding fertilization and early development. How does the highly motile, yet very small, sperm from one species recognize the immotile, very large oocyte from its own sp ...

Investigation into microtubule function in mature mammalian oocytes in relation to cryopreservation is one area of study for the present authors. An increasing number of couples are seeking the assistance of physicians for reproductive dysfunction, and cryopreservation of game ...

In pigs, as in many other species, immature oocytes liberated from ovarian follicles can resume meiosis and complete maturation in culture. Although the matured oocytes can be penetrated in vitro by spermatozoa under appropriate conditions, low rates of pronuclear formation and a high in ...

Ovulated oocytes in most mammals are arrested in metaphase II, at which point a dense array of microtubule filaments and bundles form the meiotic spindle. The spindle is vital to the alignment and separation of the chromosomes along the metaphase plate so that a proper division of the chromosome pa ...

In vitro maturation (IVM) of human oocytes is an attractive technique for reducing the costs and averting the side effects of gonadotropin stimulation for in vitro fertilization (IVF). Edwards reported that human follicle oocytes could be matured in vitro when they were isolated from foll ...

The study of the biochemical events involved in fertilization and egg activation has historically been directed toward marine invertebrate and amphibian eggs (1), although recent progress has been made in the analysis of a few enzymes that are abundant in mammalian eggs (2,3). The zebrafish ...

In vitro maturation of canine oocytes was first described in 1976 (1), but reproductive biotechnologies applied to canine species developed mostly during the last 10 yr. Few studies have been conducted on dogs because the availability of biological material (bitch ovaries in particular) ...

Fish semen cryopreservation has important applications in the following fields: (1) in aquaculture, for synchronization of artificial reproduction, for efficient utilization of semen, and for maintaining the genetic variability of broodstocks; (2) in biodiversity, for gene ba ...

The zebrafish system has many features that are ideal for the study of signal transduction enzymes involved in fertilization. However, one problem that the zebrafish egg shares with eggs of many species is that most of the signal transduction proteins are already synthesized and stored in the e ...

Prior to fertilization, spermatozoa of many animals and plants show chemotactic behavior toward eggs. Chemotactic behavior was first described in ferns (1), and their attractant was identified as the bimalate ion (2). In animals, sperm chemotaxis to the egg was first observed in the hydrozo ...

Mammalian oocytes enclosed in the ovary are arrested at the diplotene stage of the first meiotic prophase, which is also termed the germinal vesicle (GV) stage. Following proper stimulation (gonadotropin in mammals), the fully grown oocytes reinitiate meiosis. The resumption of meiotic ...

Although sperm motility has been studied for over 300 yr, sperm chemotaxis in animals has been documented and quantified only in the last 40 yr. A clear demonstration of chemotactic guidance of sperm to eggs, thereby increasing the likelihood of fertilization, was first provided in a number of inv ...

The major obstacle in standardizing techniques to evaluate stallion fertility is the huge variation in ejaculates from different stallions and even among ejaculates collected from the same stallion (1,2). Spermatozoa concentration, total volume, motility, percent live sperma ...

Substrates of small molecular size can reach the active site of immobilized enzymes without suffering significant steric hindrances generated by the support. The situation is very different when macromolecular substrates are used (Fig. 1). Some of these reactions are of great interes ...

Covalent binding of an enzyme to a support is probably the most interesting method of immobilization from an industrial point of view. In this methodology, the activated groups of the support react with some external functional groups of the protein (see Chapter 1). Generally, reaction betwe ...

Adsorption is a very economical procedure for immobilization of enzymes. The stability of the adsorbed enzyme derivative will depend on the strength of the noncovalent bonds formed between the support and the amino acid residues on the surface of the protein. Two principal types of bonds can be f ...

Coimmobilization of cells and/or enzymes is performed for three main reasons: first, to enable cells to use other, nonmetabolizable substrates than the natural ones of the corresponding strain (1,2); second, to enlarge the product spectrum by utilization of the catalytic capabilities of ...

Polyelectrolyte complexes are rapidly formed when oppositely charged polyions are mixed. There are two basic principles making use of polyelectrolyte complexes for immobilization of cells and enzymes—entrapment and microen-capsulation. Because the entrapment in polyel ...

Carbonyldiimidazole (CDI) activated supports for enzyme immobilization are commercially available. The urethane linkage that is formed when a protein is bound to these supports is about 20-fold more stable than the N-substituted isourea linkage formed during protein immobiliz ...

For many years, chemical modification of enzymes has been a key technique to elucidate the residues involved in their catalytic activity. More recently, chemical modification has also been a useful tool in applied biochemistry (e.g., enzyme stabilization by modification of key residue ...