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Biomedical subjects

R Yanagimachi

Publications and source records attributed to R Yanagimachi.

At least 199 records · Page 11Linked to original sources
PubMed1976

The sperm acrosome reaction and fertilization in the guinea-pig: a study in vivo.

Female guinea-pigs were naturally or artificially inseminated before or after ovulation and the distribution of spermatozoa in the oviducts and the time of sperm penetration into the eggs were determined. When animals were inseminated before ovulation, the spermatozoa stayed in the distal half of the oviduct until about the time of ovulation. Only a very few spermatozoa were present in the proximal half of the oviduct at the time of ovulation, but these were sufficient to effect fertilization. When animals were inseminated after ovulation, the spermatozoa ascended the oviduct faster than when animals were inseminated before ovulation, and fertilization commenced in 4 hr. Regardless of the time of insemination, the spermatozoa participating in fertilization appeared to undergo the acrosome reaction after they reached the proximal part of the oviduct or when they were very near the eggs.

Acrosome↗
PubMed1975

Ultrastructural localization of lectin-binding sites on the zonae pellucidae and plasma membranes of mammalian eggs.

Receptors for Ricinus communis agglutinin I (RCAI), concanavalin A (Con A), and wheat germ agglutinin (WGA) were localized on the zonae pellucidae and plasma membranes of hamster, mouse, and rat eggs with ferritin-lectin conjugates. Intact eggs labeled with the ferritin conjugates showed dense concentrations of RCAI and WGA receptors in the outermost regions of their zonae pellucidae and sparse distributions of Con A receptors throughout the zonae. Ferritin-lectin labeling was specific, since inhibitory saccharides effectively blocked labeling. The asymmetric density of RCAI receptors across the zona was confirmed by ferritin-RCAI and fluorescein-RCAI labeling of mechanically isolated zonae pellucidae, indicating that the RCAI-binding sites are more densely distributed in the exterior zona regions. Plasma membranes of rodent eggs contained RCAI, WGA, and Con A receptors. These receptors were found to be more or less randomly distributed on surfaces of aldehyde-fixed eggs or on eggs labeled near 0 degrees C. However, eggs incubated at 25 degrees C showed aggregated WGA- and Con A-binding site distributions on their plasma membranes. This indicates that lectin-induced receptor redistribution occurs at this temperature. The possibility that plasma membrane receptor mobility is a requirement for sperm-egg fusion is discussed.

Animals↗
PubMed1975

Maturation iv vitro of ovarian oocytes of prepubertal and adult hamsters.

Oocytes of various sizes were isolated from ovaries of sexually mature and prepubertal hamsters and cultured ot determine whether all the oocytes were capable of maturing in vitro. It was found that only the oocytes that had attained maximum size (about 80 mum in the vitelline diameter) were capable of undergoing maturation in vitro. Smaller oocytes (less than 80 mum in diameter) failed either to initiate or to complete maturation. The oocytes which were capable of maturing in vitro (competent oocytes) were present in the ovaries of adult females 136 to 138 hr before ovulation. The competent oocytes first appeared in the ovaries of prepubertal females on the 23rd day after birth, about 10 days before puberty.

Age Factors↗
PubMed1975

Block of hamster fertilization by anti-ovary antibody.

Antibody produced in rabbits against hamster ovary blocked fertilization of golden hamster eggs in vitro by binding to the surface of the zona pellucida and rendering it impenetrable to spermatozoa. The antibody was also effective in blocking fertilization in vivo. An intraperitoneal injection of the antibody into females resulted in the complete inhibition of fertilization for approximately 12 days, i.e. three oestrous cycles. This temporary sterility was apparently due to the binding of the antibody to the zona pellucida of oviducal and ovarian oocytes, and dot due to a failure of sperm ascent or capacitation in the female genital tract. Neither the oestrous cycle nor ovulation was affected by the antibody injection.

Animals↗
PubMed1974

Mobility and the restriction of mobility of plasma membrane lectin-binding components.

Labeling by ferritin-conjugated agglutinins from Ricinus communis was used to demonstrate the relative mobilities of the agglutinin receptors located in specific regions on plasma membranes of rabbit spermatozoa. The relative mobility of lectin receptors was higher on postacrosomal regions of sperm than on acrosomal and tail regions. Lectin-induced clustering could not be demonstrated in the acrosomal and tail regions, an indication of the existence of localized restraints on the mobilities of lectin receptors. A system of transmembrane restraints may maintain the segregation of plasma membrane components into membrane domains on certain highly differentiated cells.

Animals↗