Metaplastic charges due to vitamin A-deficiency and overstimulation with estrogen were studied in the uterus of the rat. The investigation was concerned with the following problems: (1) the role of the ovaries in producing uterine metaplasia in vitamin A-deficient rats; (2) whether uterine metaplasia which is induced by estrogen is a gradual process or a rapid one, which takes place a short time after the beginning of treatment; (3) whether the age of the animal at the start of estrogen treatment has any effect on the production of metaplasia; and (4) a cytologic comparison of the metaplastic processes resulting from vitamin A-deficiency with those resulting from overstimulation with estrogen.
"Depolarization-dependent calcium influx is biphasic in synaptosomes (Nachshen and Blaustein, 1980, 1982). The fast and slow components of 45 Ca++ influx are proposed to occur through separate calcium channels. In this report the fast and slow components of depolarization-dependent 45Ca++ influx are resolved. The fast component is inactivated by predepolarization, inhibited by low concentrations of lanthanum and closely correlates with the rapid release of 3H-norepinephrine from synaptosomes. The properties of the fast component of influx suggest that it is mediated by calcium channels which inactivate during the first second of depolarization. The slow component is not sensitive of predepolarization and is partially dependent on the internal Na+ content of the synaptosomes. It is proposed that during depolarization a portion of the slow component of Ca++ influx in synaptosomes is mediated by a Na i/Cao exchange mechanism."