Separation of monovalent and divalent ions from aqueous solution by electrodialysis and nanofiltration.

The possibilities of separating monovalent and multivalent ions by electrodialysis (ED) and nanofiltration (NF) are explored. Five synthetic single salt solutions were applied to ED and NF: NaCl, Na(2)SO(4), MgCl(2), MgSO(4) and NaNO(3). Two combinations of anionic and cationic exchange membranes were evaluated for ED (AMV/CMV Selemion membranes and ACS/CMS Tokuyama membranes), and two membranes were evaluated for NF (NTR 7450 and UTC-60). The separation was evaluated using an alternative parameter, the separation efficiency, in order to compare ED and NF. The separation efficiency ranges from 0% (no separation) to 100% (perfect separation). Both NF membranes had a good separation efficiency for the separation of monovalent and divalent anions (ca. 60%); the ED membranes performed worse. For the separation of monovalent and divalent cations, the UTC-60 membrane was the best for the considered separation because of size exclusion effects for the larger divalent ion. The ACS/CMS membranes had a similar separation efficiency (ca. 60%); the NTR 7540 membrane and AMV/CMV ED membranes showed only a small separation.

Embryo implantation during the short luteal phase of the corn mouse, Calomys musculinus, and the apparent lack of a lactational diapause in South American murid rodents.

As the corn mouse, Calomys musculinus, has a short luteal phase (2-3 days) that is not prolonged after copulation, it was hypothesized that (i) implantation would occur at the end of this phase, that is, earlier than it occurs in most murid species that have been studied, and (ii) a lactational embryonic diapause would not occur during the luteal phase. These hypotheses were tested in females that had copulated during postpartum oestrus and were either lactating or not lactating. Data were recorded from day 3 to day 5 of pregnancy (day 1 = day after coitus), at both 03:00-05:00 h and 17:00-19:00 h. Evidence of implantation in both non-lactating and lactating animals was apparent at 03:00-05:00 h on day 4 (endometrial 'blue reaction' in all cases and failure to recover free uterine embryos in some cases) and implantation swellings appeared within 24 h in both groups. In another experiment, the increase in duration of interbirth intervals in continuously mated females and their correlation with the number of suckling young were compared among C. musculinus, C. laucha, Akodon molinae (South American murid species) and Peromyscus maniculatus (a North American murid in which a lactational embryonic diapause has been shown). The results were indicative of a lactational embryonic diapause in the North American species, but not in the South American species. It was concluded that in C. musculinus (i) implantation occurs at the end of the spontaneous luteal phase, and (ii) that a lactational embryonic diapause does not occur: the absence of a lactational embryonic diapause may be common to other South American murid rodents.

Evidence that a novel type of progestational phase control occurs in the corn mouse, a South American murid rodent.

Most Muridae display a short luteal phase that becomes functional as a consequence of the prolactin release induced by the stimulation of copulation and/or lactation. The corn mouse also shows a short luteal phase, and we wanted to know whether copulation and/or lactation would release prolactin and maintain progesterone secretion in this species. Females in postpartum estrus were either allowed to copulate with an intact male or not, and either to lactate their young or not. Afterward, plasma progesterone was elevated over the baseline level only in females that had copulated and were bearing growing embryos (whether or not they were lactating), while prolactin was elevated only in lactating females. In another experiment, endometrial scratching induced decidualization both in females that had copulated with a vasectomized male and in those that had not copulated; sham operations had no effect in either case. Progesterone levels were elevated in decidualized animals as compared with their sham-operated controls. Results indicate that the initiation of the progestational phase in the corn mouse is not dependent on prolactin release. A short luteal phase during which nidation may occur has not yet been described in any other mammal.

Effect of estrogen and placental lactogen on lactogenesis in pregnant rats.

The removal of the corpora lutea or ovariectomy on Day 18 of pregnancy induced a rise in serum prolactin 24 h after surgery with a rapid decline to control values 4 h after the surge, only in the ovariectomized group. When hysterectomy was performed in addition to luteectomy or ovariectomy a similar rise in prolactin was obtained. Lactose synthetase activity in mammary tissue was significantly higher in the luteectomized and luteectohysterectomized rats when compared with ovariectomized, ovariohysterectomized rats and the sham-operated group. Estrogen treatment 12 h after ovariectomy increased serum prolactin and lactose synthetase activity to values similar to those measured in luteectomized rats, but this increase was significantly greater when compared with the ovariectomized-nontreated group. Treatment with Tamoxifen did not decrease serum prolactin in the luteectomized rats but lactose synthetase was reduced to values similar to that obtained in ovariectomized rats. Treatment with 2 bromo-alpha-ergocryptine-mesylate (CB-154) prevented the rise in serum prolactin in the ovariectomized, luteectomized and luteectohysterectomized groups, but lactose synthetase activity was lowered to control values (sham-operated rats) only in the luteectohysterectomized rats. According to these findings, rat placental lactogen in the absence of prolactin and progesterone induces lactose synthesis. Estrogen facilitates prolactin but not placental lactogen action on lactose synthetase activity.

Half-life of circulating renin under different experimental conditions.

The half-life of circulating renin was studied in normal rats and in rats with a single kidney that was ischemic. The resulting disappearance curve represented the sum of two exponentials. The average half-life of the fast component was 11.5 minutes for normal rats, 11 minutes for rats with mild renal ischemia, and 8 minutes for rats with severe renal ischemia. The mean half-life of the slow component was 67 minutes in normality, 84 minutes in mild ischemia, and 121 minutes in severe ischemia. Also, the calculated proportion of the slower component was different for each group--60.3% in normality, 68.2% in mild ischemia, and 82.2% in severe iischemia. The results suggest that more than one kind of renin may be produced and released by the kidney, and also that renal ischemia may modify the normal metabolism of renin.