Discordant accelerated pulmonary maturation after adrenocorticotropic hormone-induced labor in twin sheep fetuses

To examine the role of parturition on lung maturation in sheep, we studied parameters of lung development in singleton fetuses treated with pulsatile adrenocorticotropic hormone or saline solution from day 127 or twin pregnancies in which one fetus only received pulsatile adrenocorticotropic hormone from day 127 until labor occurred. These parameters were compared with those of term fetuses (145 days). Pulsatile adrenocorticotropic hormone provoked labor in a mean (+/- SEM) of 102.6 +/- 6.6 and 181.0 +/- 18.0 hours in single and twin pregnancies, respectively. Adrenal/body weight ratios increased similarly in adrenocorticotropic hormone-treated single and twin fetuses at delivery, and basal cortisol levels were two- to threefold higher prepartum in adrenocorticotropic hormone-treated fetuses. Little change in plasma cortisol levels occurred in singletons treated with saline solution or in twins not infused with adrenocorticotropic hormone. The lung weight/body weight was not altered in any group. Lung distensibility and stability were doubled to term values in fetuses treated with pulsatile adrenocorticotropic hormone compared with controls and untreated twins. Mean lavage phosphatidylcholine levels rose from 0.07 to 0.11 mg/gm in saline solution-treated or untreated fetuses to 0.20 to 0.23 mg/gm in pulsatile adrenocorticotropic hormone-treated singletons or twins, compared with 0.63 mg/gm at term. Phosphatidylcholine production increased from 0.51 dpm/gm/hr in saline solution-treated fetuses to 0.73 and 0.89 dpm/gm/hr in the single and twin pulsatile adrenocorticotropic hormone-infused fetuses, respectively; phosphatidylcholine production was 0.62 dpm/gm/hr in the noninfused twin. Lungs of twins treated with pulsatile adrenocorticotropic hormone were morphologically more mature than those of untreated twins. We conclude that fetal endocrine responses to exogenous adrenocorticotropic hormone, rather than the stimuli associated with labor per se, are responsible for lung maturation in the fetal sheep.     

Steroid modulation of pregnenolone to progesterone conversion by human placental cells in vitro

Studies were performed to examine the production of progesterone by human placental cells in vitro. Samples of placentas from 22 women at term after spontaneous onset of labor and vaginal delivery were utilized. The tissue was dispersed into isolated cells with the use of collagenase, and suspensions of these cells were incubated with pregnenolone as substrate in the presence or absence of other compounds which may regulate progesterone production. These cell preparations produced progesterone in a dose-related fashion with exogenous pregnenolone. The conversion of pregnenolone to progesterone occurred rapidly, with most of the conversion completed during the first hour of incubation. The conversion was inhibited by dehydroepiandrosterone, estrone, androstenedione, and testosterone (p less than 0.001 in all cases). The inhibitory effect of androstenedione and testosterone was not dependent on aromatization to estrogen. Dihydrotestosterone and 5 alpha-pregnanedione resulted in a significant increase in the amount of progesterone present (p less than 0.001). In preliminary experiments, gonadotropin-releasing hormone, salbutamol, and propranolol were without significant effect in this system. We conclude that this system is a useful model for studying progesterone production by human placental tissue, and that placental progesterone production may be significantly influenced by the presence of other steroid hormones.     

Gelatin particle agglutination assay for HIV antibodies: a rapid, economical modification with increased sensitivity

Modification of a commercial gelatin particle agglutination assay for anti-HIV reduces the test time to 30 min, increases the sensitivity sevenfold without any prozoning, and maintains specificity while cutting the cost of the test by 90%. The modification involves a tenfold dilution of the gelatin particles, which are added to a dilution of test serum in a 'V' well standard microplate. After incubation, plates are centrifuged briefly and allowed to stand at an inclination of 70 degrees until positive and negative reactions are clearly distinguishable within approximately 15 min.     

Ultrastructural basis for maintenance and termination of pregnancy.

Myometrial tissues from guinea pigs, sheep, and human subjects at various stages of gestation and postpartum were quantitatively examined in the electron microscope for the presence of gap junctions between muscle cells. Gap junctions were found in tissues from guinea pigs and sheep which were being delivered or ready to be delivered and in tissues taken immediately post partum. Gap junctions were also present in 19 tissues obtained from 69 women undergoing elective or emergency cesarean section for a variety of reasons. The frequency of their occurrence varies in relation to the presence or absence of labor and other conditions. We propose that gap junctions are required for effective muscle contractions leading to termination of pregnancy in all animals, including human beings. The absence of gap junctions throughout gestation may be necessary for maintenance of pregnancy and the premature appearance of the cell contacts may lead to premature labor.