Lack of gonadotropic activity in the rabbit blastocyst prior to implantation

Recent reports of an LH-like hormone in the rabbit preimplantation blastocyst and of elevated serum progesterone levels in the presence of unimplanted blastocysts prompted us to characterized further the biological activity of the presumed gonadotropin. Progesterone was measured by a highly specific radioimmunoassay in sera obtained from pregnant and pseudopregnant rabbits after mating (day 0) to fertile or vasectomized males. On days 3, 4, 5, and 6, which represent the preimplantation period, mean progesterone concentrations (ng/ml +/- SE) were 4.3 +/- 0.7, 5.1 +/- 0.5, 6.8 +/- 1.1, and 9.0 +/- 1.9 in 5 pseudopregnant rabbits and 4.1 +/- 0.4, 6.7 +/- 0.6, 5.9 +/- 0.9, and 7.0 +/- 0.8 in 7 pregnant rabbits. In a separate experiment, serum progesterone concentrations in 6 pseudopregnant and 8 pregnant rabbits were 10.1 +/- 0.7 ng/ml and 13.7 +/- 1.1 (P less than 0.02), respectively on days 11-12. Thus, serum progesterone concentrations were not different in pregnant and pseudopregnant rabbits before the time of implantation (day 7), but were higher in pregnant rabbits after implantation. Blastocysts obtained on day 6 and incubated with a cell suspension of immature rat ovaries failed to stimulate the accumulation of progesterone in medium, in contrast to hCG, which was active even in the presence of blastocysts. Day-6 blastocysts also failed to stimulate the accumulation of testosterone from decapsulated rat testes and of progesterone from rabbit ovarian tissues in vitro. A gonadotropic effect of the conceptus can be observed in the rabbit within 4 to 5 days after implantation. However, we find no evidence for the existence of an LH-like hormone in the preimplantation blastocyst which stimulates the rabbit ovary to secrete progesterone.

Effect of prolactin on LH receptor in rat luteal cells

This investigation was undertaken to determine whether prolactin might act as a luteotropic hormone in the rat by increasing the receptor for LH. Immature female rats were treated with 5 SC injections of oFSH beginning at 0900 h on day 25; luteinization was induced with a single SC injection of oLH at 1500 h on day 27. In this model, LH-receptor activity, assessed by specific binding of [125I]iodohCG to ovarian membrane fractions, increased steadily (greater than 7-fold) from day 27 to day 33; specific [125I]iodoprolactin binding rose greater than 3-fold between days 27 and 31. Serum progesterone measured at 1500 h rose from greater than 10 ng/ml on day 27 to greater than 130 ng/ml on day 34. 2-Bromo-alpha-ergocryptine (CB-154, [EC]; 35 mug) given 2 X/day beginning at the time of LH injection, blocked nocturnal increases in serum prolactin measured at 0200 h on days 29, 30, and 31, and resulted in reduced binding of [125I]iodohCG on days 31 and 33; serum progesterone was similarly reduced on days 31 and 34 in EC-treated rats. Simultaneous treatment with EC and prolactin completely reversed the effects of EC with regard to both binding of [125A]iodohCG and serum progesterone. Changes in ovarian uptake of [125I]iodohCG in vivo were similar to those of the in vitro experiments described above. EC and/or prolactin treatment did not affect binding of [125I]iodoprolactin. In summary, the data indicate that LH in the absence of prolactin can induce the formation of corpora lutea which have an increased number of prolactin receptors but which have a few LH receptors and a reduced capacity to produce progesterone. If prolactin is present during the early luteinization process, corpora lutea develop an increased capacity to bind LH and to produce progesterone. It is possible that the increase in LH-receptor and progesterone production occur as independent events both mediated by the luteotropic action of prolactin. Alternatively, LH receptor might be limiting for LH stimulation of progesterone production.

The principles of hyperbaric and anoxic radiotherapy

The effectiveness of hyperbaric and anoxic radiation therapy has been analysed in relaton to local control of malignant disease. Pilot schemes have led to the adoption of two basic treatment regimes which have similar morbidity to conventional regimens, but within their limitations are shown here to greatly increase the response rate of the malignancies treated. The limitations of each method are established. It is the lack of appreciation of limitations which have prejudiced much opinion against such methods; this article attempts to put their true place in perspective.

Premature regression of corpora lutea in pseudopregnant rabbits following the removal of polydimethylsiloxane capsules containing 17 beta-estradiol

17-beta-Estradiol, which is luteotropic in rabbits, was administered during pseudopregnancy via polydimethylsiloxane (Silastic) implants to determine the effects on serum progesterone concentrations. Implants which released estradiol at a rate of approximately 2 mug/day were place beneath the skin the day after sterile mating and ovulation (day 0). Blood (3 ml) was obtained from the marginal ear vein on days 3, 6, 9, 10, 11 and 12. Serum estradiol levels, determined by radioimmunoassay, were 2- to 3-fold higher in estradiol-treated rabbits (11.7 plus or minus 1.2 pg/ml) than in untreated pseudopregnant controls (5.9 plus or minus 1.4 pg/ml). Weights of corpora lutea in treated and control rabbits were not different at the conclusion of the experiment on day 12. Serum progesterone concentrations, also determined by radioimmunoassay, were not significantly different between treated and control animals. However, when estradiol implants were removed from other rabbits on day 10, a rapid decline in serum progesterone occurred, from 14.0 plus or minus 2.4 to 2.6 plus or minus 0.8 ng/ml 24 h later. By comparison, serum progesterone concentrations in rabbits with estradiol implants left in place and in untreated rabbits on day 12 were similar (similar to 12 ng/ml). The premature decline in serum progesterone was accompanied by a decrease in the wet weight of corpora lutea. Other experiments revealed: 1) a precipitous fall in serum estradiol to basal values within 2 h after estradiol implants were removed, preceding the decline in serum progesterone by approximately 6 to 10 h; 2) reduced levels of estradiol in ovarian venous blood, but elevated levels of estradiol in peripheral arterial blood of rabbits with estradiol impants. The inability to elevated estradiol to increase serum progesterone or weights of corpora litea suggests that the luteotropic effect is maximal when estradiol is present at physiological concentrations. Following the continuous administration of estradiol, ovarian secretion of estradiol appears diminished and the corpora lutea become dependent upon the exogenous estradiol for luteotropic support. Although the ovaries continue to release measureable quantities of estradiol, this is inmeasurable quantities of estradiol, this is insufficient to prevent regression of corpora lutea when exogenous estradiol is rapidly withdrawn from the circulation.

Experimental tetracycline labeling in avian osteopetrosis

Osteopetrosis was experimentally produced and lesion development in time was studied by fluorescent illumination of tetracycline labels in the bone. Bones from birds 84, 115, 186 and 354 days of age were examined by ground section under ultraviolet light. Periosteal activity of the tibia and femur was present in normal bones at 84 days of age but had stopped at 115 days. Focal periosteal activity of osteopetrotic lesions was present at 186 days but not at 354 days of age. Slight endosteal activity of osteopetrotic bones was present at 354 days of age. Osteopetrotic bone formed at a rate of 1.26 mm. per week or 6 times faster than normal bone in some of these lesions. Tetracycline diffused throughout the 354-day-old osteopetrotic lesion but not normal compact bone indicating that the osteopetrotic bone is porous and spongy.

Surface temperatures of avian osteopetrotic bones

Body temperatures and surface temperatures of metatarsal bones were recorded in normal and osteopetrotic chickens. Osteopetrotic lesions were 6.5 F warmer than normal bones but there was no corresponding increase in body temperature at a given environmental temperature. This indicates that the temperature elevation in the osteopetrotic lesion is a local phenomenon and not a systemic response. This also supports earlier observations that osteopetrotic bones feel warmer to the touch than normal bones.