Local stimulation of prostaglandin production by corticotropin-releasing hormone in human fetal membranes and placenta

Corticotropin-releasing hormone is produced by the human placenta and fetal membranes, but its physiological significance is not established. We examined the possibility that CRH might affect prostaglandin output by these intra-uterine tissues. Primary cultures of amnion, chorion, decidua and placenta were established from tissue obtained from women at term elective cesarean section were maintained in the presence of increasing concentrations of synthetic hCRH. PG output at 48h was measured by radioimmunoassay. hCRH stimulated PGE2 output by amnion, chorion and placenta, but not by decidual tissue. PGF2 alpha output was stimulated in amnion, decidua and placenta but not chorion, whereas output of 13, 14-dihydro-15-keto PGF2 alpha was stimulated in all four tissues. We conclude that hCRH stimulates prostaglandin output by human placenta, decidua and the fetal membranes, raising the possibility of paracrine or autocrine interactions between CRH and prostaglandins in vivo.     

Stimulation of ovine myometrial activity by 6-keto prostaglandin E1

6-keto prostaglandin E1 (6KE) is a metabolite of PGI2, which we have shown previously inhibits spontaneous myometrial activity. In the present study we examined the effects of 6KE on uterine electrical and mechanical activity in non-pregnant ovariectomized sheep. 6KE stimulated uterine activity in a dose-dependent fashion. The effect was enhanced by pre-treatment with estradiol (E2). It was not influenced by pre-treatment with meclofenamic acid and was not associated with significant changes in the concentrations of 13,14 dihydro 15-keto PGF2 alpha in vena cava plasma. After E2 treatment, 6KE had 0.2-0.3 of the stimulatory activity of PGF2 alpha. In the absence of E2, the uterine response to both 6KE and PGF2 alpha was decreased. In animals in which spontaneous myometrial activity was inhibited by PGI2, the uterus remained responsive to 6KE. We conclude that in the ovariectomized non-pregnant sheep 6KE stimulates uterine activity, and that the effect is independent of endogenous PG production.     

Activation of adrenal function in fetal sheep by the infusion of adrenocorticotropin to the fetus in utero

We determined whether ACTH1-24, infused into fetal lambs at a rate that is known to cause premature labor, elicits changes in the responsiveness of the fetal adrenal glands, and alters the pattern of corticosteroid output. Plasma cortisol (F), corticosterone (B) and progesterone (P4) were measured during 72 h of infusion of saline or ACTH (10 micrograms/h) beginning on Day 127 of pregnancy. Adrenals were then dispersed into isolated cells, and the output of F, B and P4 after exogenous ACTH determined in vitro. Plasma concentrations of F and B were higher in ACTH-treated fetuses. The increment in F (5-to 7-fold) was greater than that in B (2-fold) such that the F:B ratio in plasma of ACTH-treated fetuses on Days 2 and 3 of infusion was 2.5 times higher than in controls. After 72 h of infusion, the adrenal weights in ACTH-treated fetuses (741 +/- 38 mg, +/- SEM; n = 4) were greater than in the control animals (349 +/- 11 mg). There was a significant effect of ACTH pretreatment in vivo on F output by isolated adrenal cells in vitro. Mean increments in F output after addition of ACTH1-24 (5000 pg/ml) in vitro rose from 368 +/- 235 pg/50,000 cells in controls, to 64,639 +/- 19,875 pg/50,000 cells after ACTH in vivo. There was no significant effect of ACTH in vivo on B output in vitro; the ratio of F:B output, either in the absence or presence of ACTH in vitro, was significantly higher in cells from ACTH-pretreated fetuses. There was a significant effect of in vivo ACTH on in vitro P4 output. After ACTH treatment in vivo there was an increase in the vitro output ratio of F:P4, but no change in the output ratio of B:P4. We conclude that ACTH treatment of the fetal lamb in vivo results in activation of fetal adrenal function, increased fetal adrenal responsiveness to ACTH, and directed corticosteroid biosynthesis towards cortisol. Our results are consistent with an increase in fetal adrenal 17 alpha-hydroxylase activity after ACTH treatment.     

Stimulation of ovine myometrial activity by 6-keto prostaglandin E1

6-keto prostaglandin E₁ (6KE) is a metabolite of PGI₂, which we have shown previously inhibits spontaneous myometrial activity. In the present study we examined the effects of 6KE on uterine electrical and mechanical activity in non-pregnant ovariectomized sheep. 6KE stimulated uterine activity in a dose-dependent fashion. The effect was enhanced by pre-treatment with estradiol (E2). It was not influenced by pre-treatment with meclofenamic acid and was not associated with significant changes in the concentrations of 13,14 dihydro 15-keto PGF_2α in vena cava plasma. After E2 treatment, 6KE had 0.2–0.3 of the stimulatory activity of PGF_2α. In the absence of E2, the uterine response to both 6KE and PGF_2α was decreased. In animals in which spontaneous myometrial activity was inhibited by PGI2, the uterus remained responsive to 6KE. We conclude that in the ovariectomized non-pregnant sheep 6KE stimulates uterine activity, and that the effect is independent of endogenous PG production.     

Uterine prostaglandin concentrations following fetal death in sheep

Concentrations of prostaglandin E (PGE), PGF and 6-oxo-PGF_1α (the hydrolytic product of PGI₂) were measured by radioimmunoassay (RIA) in myometrium, endometrium, cotyledons, amnion and chorioallantois taken from different uterine areas from chronically catheterized sheep bearing fetuses which had died 12–26 h previously (n=4) or 34–72 h previously (n=4). These two groups of animals were designated fetuses dead <30 h and >30 h respectively. The time of fetal death was assessed on the basis of fetal heart rate and blood gases. At the time of the tissue collection the ewes were between 123 and 130 days after mating. For comparative purposes, tissues also were collected from four sheep bearing live chronically catheterized fetuses at 130 days of gestation.For myometrium, concentration of PGF, PGE and 6-oxo-PGF_1α were significantly higher in sheep bearing dead fetuses, compared to those bearing live fetuses. Analysis of variance also showed a significant effect of uterine area on myometrial PGE concentrations, concentrations being higher in tubal areas than elsewhere. Concentrations of PGE, PGF and 6-oxo-PGF_1α were higher in endometrium taken from uteri containing dead fetuses. In cotyledons, concentrations of PGF and 6-oxo-PGF_1α but not PGE, were significant elevated following fetal death. Concentrations of 6-oxo-PGF_1α, but not PGE or PGF, were elevated in both chorioallantois and amnion of sheep bearing dead fetuses, compared to those bearing live fetuses. In association with elevated PG concentrations, there was a progressive increase in the frequency and maximum amplitude of uterine contractions. These results show that PG concetrations are elevated following fetal death in sheep, and suggest an association between elevated PG concentrations and delivery of the dead fetus.     

A critical examination of the maximum velocity of shortening used in simulation models of human movement

The maximum velocity of shortening of a muscle is an important parameter in musculoskeletal models. The most commonly used values are derived from animal studies; however, these values are well above the values that have been reported for human muscle. The purpose of this study was to examine the sensitivity of simulations of maximum vertical jumping performance to the parameters describing the force–velocity properties of muscle. Simulations performed with parameters derived from animal studies were similar to measured jump heights from previous experimental studies. While simulations performed with parameters derived from human muscle were much lower than previously measured jump heights. If current measurements of maximum shortening velocity in human muscle are correct, a compensating error must exist. Of the possible compensating errors that could produce this discrepancy, it was concluded that reduced muscle fibre excursion is the most likely candidate.     

Carotenoids Induce Apoptosis in the T-lymphoblast Cell Line Jurkat E6.1

Epidemiologically, a high-carotenoid intake via a fruit- and vegetable-rich diet is associated with a decreased risk of various forms of cancer. The mechanisms by which carotenoids exert this protective effect are controversial. In this study, we examined the potency of a range of carotenoids commonly found in human plasma to induce apoptosis in Jurkat E6.1 malignant T-lymphoblast cells. At a concentration of 20 &#119 M, the order of potency to induce apoptosis after 24 h was: &#103 -carotene > lycopene > lutein> &#103 -cryptoxanthin=zeaxanthin. Canthaxanthin failed to induce apoptosis under these conditions. &#103 -Carotene induced apoptosis in a time- and concentration-dependent manner with a lowest effective concentration of about 3 &#119 M. Pre-conditioning of &#103 -carotene for 72 h destroyed its pro-apoptotic activity almost completely, whereas degradation for 6 h or less did not, indicating that either &#103 -carotene itself and/or an early degradation product of &#103 -carotene are the death-inducing compounds. Apoptosis induced by &#103 -carotene was characterized by chromatin condensation and nuclear fragmentation, DNA degradation, PARP cleavage and caspase-3 activation. The antioxidant BO-653 inhibited the degradation of &#103 -carotene in vitro and significantly increased its cytotoxicity, indicating that a pro-oxidant effect of &#103 -carotene is unlikely to cause its pro-apoptotic activity. The induction of apoptosis in transformed cells by carotenoids may explain their protective effect against cancer formation in humans. Possible pathways for induction of apoptosis by carotenoids are discussed.