Method for assay of intestinal disaccharidases.

Dexamethasone caused premature delivery when infused into foetal lambs at rates of 0\m=.\06-4\m=.\0mg./24 hr. but it had no effect when administered to pregnant ewes at the rate of 4\m=.\0mg./24 hr. Infusions into the foetus of deoxycorticosterone or corticosterone were ineffective; mixtures of dexamethasone and deoxycorticosterone did not cause parturition more rapidly than dexamethasone alone. Thus, the ability of corticosteroids to cause premature parturition appears to depend on glucocorticoid rather than mineralocorticoid activity. Parturition induced by dexamethasone was not delayed by administration of 100 mg. progesterone/24 hr. to the ewe or to the foetus. This suggests either that withdrawal of inhibitory effects of progesterone on the myometrium can occur independently of the progesterone concentration in peripheral plasma, or that the mechanism of parturition provoked by corticosteroids in the foetus can override any regulatory influence of progesterone

Premature delivery of foetal lambs infused with glucocorticoids.

Development of the Human Gastrointestinal Tract: A Review

A sensitive protein-binding assay has been used to measure plasma concentrations of total corticosterone during postnatal development in the rat. These concentrations were extremely low on days 6--12, showed a significant rise by day 14, and then continued to rise until peaking on day 24. Plasma titers of corticosteroid-binding globulin rose even more dramatically from day 12 onward. Consequently, the percentage of total plasma corticosterone, which was protein-bound, showed a gradual rise from 78% on day 12 to 98% on day 24. Despite this trend, when concentrations of free corticosterone were calculated, they were found to have a developmental profile very similar to that of total corticosterone. Assay of jejunal lactase and sucrase in the same animals that were used for the corticosterone studies showed that the ontogenic rise of both total and free corticosterone preceded the developmental changes in the activities of these enzymes by approximately 2 days. The data suggest that the rise in free corticosterone that begins on day 14 acts as a cue for enzymic changes in both liver and intestine.

https://www.physiology.org/doi/pdf/10.1152/ajpendo.1978.235.5.E451

Plasma concentrations of total and free corticosterone during development in the rat.

Necrotizing enterocolitis in very low birth weight infants: Biodemographic and clinical correlates

Studies of small intestine during development. I. Distribution and activity of beta-galactosidase.

Injection of rats aged 3 to 9 days with hydrocortisone causes precocious development of invertase activity in the small intestine. The enzyme becomes fully active about 72 hours after injection of hydrocortisone. Invertase activity is also detectable when hydrocortisone is added to organ culture of intestine derived from 5-to 6-day old rats. Hydrocortisone does not appear to affect the activity of lactase, suggesting that it does not act solely by hastening the normal maturation process.

https://science.sciencemag.org/content/sci/143/3601/42.full.pdf

Intestinal Invertase: Precocious Development of Activity after Injection of Hydrocortisone

Studies were made on the induction of thymic lymphoma in C57b1 mice by urethan alone. Urethan was injected subcutaneously into mice less than 24 hr old at a dose of 1 mg/g body weight, and seven further injections at the same dose were given at weekly intervals. Tumors were found in 12 of the 13 surviving at ages between 12 and 27 weeks, and disseminstion was found in 7 of the 12. The tumors were identical histologically with those induced by irradiation. The same weekly urethan dose was injected intraperitoneally into C57b1 mice for a total of 4 treatments, beginning at 4 to 5 weeks of age; only one of 19 mice developed lymphoma at 10 months. No lymphoid tumors were found in 30 untreated mice up to 1 year old. (D.L.C.)

Ruth G. Doell

Papers

Studies of small intestine during development. I. Distribution and activity of beta-galactosidase.

Intestinal Invertase: Precocious Development of Activity after Injection of Hydrocortisone

Urethan induction of thymic lymphoma in C57bl mice.

Studies of small intestine during development. II. The intracellular location of intestinal beta-galactosidase.