Do tocolytic agents stop preterm labor? A critical and comprehensive review of efficacy and safety.

OBJECTIVE: Our aim was to determine the efficacy and safety of tocolytic agents currently used to treat premature labor. STUDY DESIGN: We carried out a comprehensive review of tocolytic agents in the treatment of premature labor. Three hundred twenty-eight studies published between 1933 and 1992 were analyzed. RESULTS: An analysis of randomized, placebo-controlled, clinical trials showed that magnesium sulfate is not better than placebo in the treatment of premature labor. beta-Adrenergic receptor agonists effectively stop premature labor for only 24 to 48 hours. Calcium channel blockers and oxytocin antagonists inhibit uterine contractions, but their role in stopping labor is undefined. Prostaglandin inhibitors appear to be effective in treating premature labor and have few adverse side effects. CONCLUSIONS: The only tocolytic drugs that might be effective are the prostaglandin inhibitors. Tocolytic agents should be used only between 24 and 32 completed weeks of gestation. Magnesium sulfate should not be used to treat premature labor. Oxytocin antagonists should be used only in experimental clinical trials. Calcium channel blockers and beta-adrenergic receptor agonists inhibit uterine contractions but do not prolong gestation for longer than 48 hours.

Rabbit endosalpinx inhibits implantation in vitro.

OBJECTIVE: To evaluate the ability of rabbit endometrial or endosalpingeal cells to support implantation in vitro and to assess the effects of endosalpinx and endometrium-conditioned media (CM) on blastocyst-endometrial cell interaction. DESIGN: In one experiment, rabbit blastocysts were co-cultured in vitro with endometrial or endosalpingeal cells growing on Matrigel-coated plastic culture plates or Millicell-HA inserts. In a second experiment, rabbit blastocysts were co-cultured with endometrial cells in the presence of fresh medium or of endosalpinx- or endometrial-CM. After 48 or 72 hours attachment to the cell monolayer was evaluated. RESULTS: Blastocysts in co-culture attached to endometrial but not to endosalpingeal monolayers. The addition of CM from cultured endosalpinx significantly decreased embryo attachment to endometrial cells in culture. CONCLUSIONS: These findings in vitro agree with the observation that rabbit endosalpinx in vivo does not support embryo implantation and support the hypothesis that rabbit endosalpinx secretes a factor that prevent tubal implantation.

Rabbit endosalpinx suppresses ectopic implantation.

This study was undertaken to elucidate the mechanism underlying the absence of oviductal ectopic pregnancies in infraprimates. Endosalpingeal circumferential grafts were substituted for endometrium in a group of rabbits. The endosalpingeal grafts interfered with implantation as evidenced by four observations: (1) The nidation indices were lowered, (2) no implantations occurred on the grafted endosalpinx, (3) unattached blastocysts were found in animals grafted with endosalpinx, and (4) the implantation sites were significantly smaller in uterine horns containing endosalpingeal grafts. These findings suggest the presence of a factor in rabbit endosalpinx that actively suppresses ectopic implantation in the oviduct.

Human transferrin. Expression and iron modulation of chimeric genes in transgenic mice.

Transferrin (TF) is a plasma protein that transports and is regulated by iron. The aim of this study was to characterize human TF gene sequences that respond in vivo to cellular signals affecting expression in various tissues and to iron administration. Chimeric genes were constructed containing 152, 622, and 1152 base pairs (bp) of the human TF5'-flanking region with the coding region of a reporter gene, CAT (chloramphenicol acetyltransferase), and introduced into the germ line of mice. Transgenes containing TF 5'-flanking sequences to -152 bp were expressed poorly in all tissues examined. In contrast, transgenes containing TF sequences to -622 or -1152 bp were expressed at high levels in brain and liver, greater than or equal to 1000-fold higher than tissues such as heart and testes. Liver and brain are major sites of endogenous TF mRNA synthesis, but liver mRNA levels are 10-fold higher than brain. A significant diminution of CAT enzymatic activity in liver accompanied iron administration in both TF(0.67) and TF(1.2)CAT transgenic mice, mimicking the decrease of transferrin in humans following iron overload. Levels of endogenous plasma transferrin also decreased in iron-treated transgenic mice. Transgenic mouse lines carrying human TF chimeric genes will be useful models for analyzing the regulation of human transferrin by iron and for determining the molecular basis of transferrin regulation throughout mammalian development into the aging process.

Antibodies to Chlamydia trachomatis and risk for tubal pregnancy.

We performed a case-control study of the effect of exposure to Chlamydia trachomatis on the risk for tubal pregnancy. Sixty women with tubal pregnancies and 60 matched control women with normal second-trimester intrauterine pregnancies were studied. Cases were more likely than controls to have detectable antichlamydial IgG antibodies (82% versus 58%, p less than 0.01) and their mean titers were higher. The prevalence of IgM antibody seropositivity was not different between cases and controls (20% versus 12%, not significant). Compared with women with IgG antibody titers of less than or equal to 1:8 the relative risk for tubal pregnancy for women with titers greater than or equal to 1:128 was 6.6 (95% confidence interval, 2.0 to 21.6). Among women with tubal pregnancies, antichlamydial antibody titers of greater than or equal to 1:128 were significantly associated with pelvic adhesions and inflammatory tubal mucosal damage. Only 17.6% of women with detectable antichlamydial antibody or inflammatory tubal damage reported a history of pelvic inflammatory disease or gonorrhea.

The contralateral corpus luteum and tubal pregnancy.

One hundred fourteen cases of tubal pregnancy were examined for evidence of active or chronic salpingitis, other anatomic and functional etiologies, and the side of the corpus luteum relative to the pregnancy. A corpus luteum was found ipsilateral to the tubal pregnancy in 80 cases (70%) and contralateral in 18 (16%). In 16 cases (14%), the position of the corpus luteum could not be identified by inspection. No differences were noted among the groups in days from last normal menstrual period or the incidence of irregular bleeding. Of the 98 cases in which a corpus luteum was identified, 53 women (54%) had at least one condition that could be considered etiologic for tubal pregnancy, including 38 (39%) who had microscopic evidence of chronic salpingitis. No association was found between the laterality of the corpus luteum and the presence of risk factors, including mechanical factors. Possible explanations for absent corpora lutea in association with tubal pregnancies are discussed.

Pregnancy rate in timed-mated, spontaneously cyclic rhesus monkeys, Macaca mulatta.

After detection of the preovulatory oestradiol-17 beta peak in blood, females were placed with a male and left undisturbed during mating (N = 28, 94 cycles) or were exposed to serial diagnostic laparoscopy (1-4 occasions) to monitor ovulation (N = 87, 224 cycles). A total of 86 pregnancies resulted from timed mating in the 318 menstrual cycles (27% rate). When periovulatory laparoscopy was performed, the pregnancy rate was 22.3%. In the absence of laparoscopy the pregnancy rate was 38.3% (P less than 0.003). These pregnancy rates are similar to those of women and show an adverse effect of laparoscopy on pregnancy rate.

Embryo cryopreservation in cynomolgus monkeys.

An improved knowledge of cryopreservation of primate embryos will have important research and clinical application. Fifty-six 4- to 8-cell in vitro fertilized embryos were frozen in HEPES-buffered Tyrode's solution containing 1.5 M dimethylsulfoxide (DMSO) and cooled at the rate of 0.3 degrees C/minute to -39 degrees C before being transferred into liquid nitrogen. Embryos were rapidly thawed at room temperature for 2 minutes. DMSO was diluted with medium in three steps at 5-minute intervals. Of the 56 embryos, 39 (70%) were classified as viable on the basis of surviving the freezing process with greater than 50% of their blastomeres intact. Twelve of the 39 embryos were cultured overnight, and 11 cleaved at least once. Twenty-five embryos were transferred to nine synchronized, unstimulated recipient monkeys 24 to 48 hours after ovulation. Three pregnancies (33.3%) resulted from the nine transfers.

Anatomy and pathology of tubal pregnancy.

The prevalence of tubal pregnancy has increased markedly during the past decade. The reasons for this are obscure. A systematic gross and histopathologic study of 25 consecutive ectopic pregnancies has been performed using a clearing method not used previously for this purpose. In addition, the presence of the corpus luteum and its location in reference to the tubal pregnancy are documented. Results indicate that trophoblastic spread was predominantly intraluminal in 67% of cases. Intratubal hemorrhage, generally in parallel to trophoblastic spread, often led to marked tubal destruction. Histologic evidence of salpingitis was noted in only seven of 24 specimens (29%). The corpus luteum was contralateral to the ectopic pregnancy in five of 21 cases (23.8%). Clinical correlates and areas of future research are discussed. Results indicate that segmental resection of the tubal pregnancy is appropriate in selected cases.

Peptide and steroid hormone concentrations in human seminal plasma.

Concentrations of peptide (alpha fraction of human chorionic gonadotropin [alpha-hCG], beta fraction of human chorionic gonadotropin [beta-hCG], luteinizing hormone [LH], follicle-stimulating hormone [FSH], and prolactin [PRL] ) and steroid hormones (testosterone [T], dihydrotestosterone [DHT], estrone [E1], estradiol [E2] and delta 4-androstenedione [A] ) were measured in the seminal plasma of 193 men. They were divided into three groups: group 1--patients attending an infertility clinic; group 2--normal volunteers of proven fertility; and group 3--men vasectomized at least 1 year prior to the study. Correlations among concentrations of hormones in seminal plasma and characteristics of the spermogram were studied. Seminal concentrations of alpha-hCG, beta-hCG, LH, T, and DHT were significantly higher in subjects with sperm in their ejaculate than in vasectomized men. No differences were observed among the groups in seminal concentrations of FSH, PRL, A, E1, and E2. Concentrations of beta-hCG and LH were highly correlated with the numbers and motility of sperm in the ejaculates. Testosterone concentrations were significantly correlated with motility of sperm.

The effects of chronic administration of LH-RH agonists and antagonists on the menstrual cycle and endometrium of the rhesus monkey.

Regularly cycling rhesus monkeys (Macaca mulatta) were used to study the effects of prolonged administration of LH-RH analogs on the menstrual cycle and the endometrium. According to the treatment, animals were divided into: Group 1, vehicle; Group 2, LH-RH agonist (D-Trp6 LH-RH, 20 micrograms/day); and Group 3, LH-RH antagonist [( N-Ac-D-Trp1,3, D-p-Cl-Phe2,D-Arg6,D- Ala10 ]-LH-RH,200 micrograms/day) for 90 days. Follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and progesterone (P) were measured every second day until thirty days past the discontinuation of drug administration. Endometrial biopsies were obtained on days 10, 40, 90 and 120 and processed for histologic exam and determination of estrogen (E) and progesterone receptors. Animals of Group 1 presented regular cycles, while those in Groups 2 and 3 remained anovulatory throughout the treatment. Animals of Group 2 presented different degrees of endometrial hyperplasia during treatment and animals of Group 3 showed either resting or atrophic endometrium. Administration of LH-RH agonist produced a marked increase in E and P endometrial receptors and the antagonist produced a decrease in P receptors. In both instances, reversal of the effects on the menstrual cycle and in the endometrium was observed 30 days after discontinuation of drug administration.

Prevention of the postcoital luteinizing hormone surge by ultrashortloop feedback control.

Studies were designed to determine whether the ultrashortloop feedback (USLF) system could prevent the gonadotropin-releasing hormone (GnRH) stimulation and postcoital rise of luteinizing hormone (LH). Unanesthetized castrated female rabbits bearing chronically-implanted venous catheters were subjected to the following: (1) GnRH stimulation. Ten animals received intravenous (IV) bolus injections of 30 microgram GnRH. Two hours prior to GnRH, animals received either 2000 IU human chorionic gonadotropin (hCG) or saline. A second group of ten animals received 20 microgram GnRH. One hour prior to GnRH, an infusion of human luteinizing hormone (hLH) at 2.75 IU/min or of saline was started and continued over 4 hours. (2) Coital stimulation. Ten rabbits were studied with the use of natural coital stimulus. They received either 2000 IU hCG 2 hours before mating or saline as a control group. Both hLH infusion and hCG injection inhibited GnRH stimulation of LH secretion but did not modify the follicle-stimulating hormone (FSH) response. hCG inhibited the coitus-induced LH surge and did not modify coitus-induced FSH secretion. These studies demonstrate that USLF control of LH can modulate LH secretion under both pharmacologic and physiologic conditions.

Luteal function in hypophysectomized rhesus monkeys.

Experiments were designed to study the maintenance of corpus luteum function in the rhesus monkey. The experiments used a transfrontal microsurgical approach for total hypophysectomy. This proved to be a reliable and safe procedure for the complete removal of the pituitary gland. Luteal function was not affected by either complete hypophysectomy or sham surgery performed 1 day after ovulation. The concentrations of PRL in serum became undetectable during the luteal phase in hypophysectomized animals. Serum LH levels in the first postoperative cycle were detectable, but were just above the lower limits of sensitivity of the bioassay. Ovulation was induced with human menopausal gonadotropin and hCG or human menopausal gonadotropin and human LH at least 6 months after hypophysectomy, at which time endogenous LH was undetectable. These animals displayed normal luteal function, for approximately 10 days suggesting that the corpus luteum, once formed, can function independently of circulating LH and in the absence of the pituitary gland.

Effects of porcine follicular fluid on gonadotropin concentrations in rhesus monkeys.

The administration of steroid-free charcoal-treated porcine follicular fluid to long term castrated female rhesus monkeys lowered basal serum concentrations of FSH and had almost no effect on serum LH. Treatment with porcine follicular fluid before the administration of exogenous LRH inhibited the release of FSH, but also affected the release of LH. This inhibition was especially striking on the suppression of the peak of release of both FSH or LH at 20 min. These findings suggest that an inhibin-like material present in follicular fluid could play an important role in the secretion of FSH and LH in rhesus monkeys.

Effects of delta 9-tetrahydrocannabinol during the follicular phase of the rhesus monkey (Macaca mulatta).

It is well documented in the literature that delta 9-tetrahydrocannabinol (THC) decreases serum concentrations of pituitary gonadotropins in several species. To study its effects in the menstrual cycle of regularly cycling rhesus monkeys, 2.5 mg/kg THC were administered to five animals from days 1-18 of the cycle [ovulation day in our colony, 15 +/- 1 day (mean +/- SD)]. Controls received vehicle (Tween 80 and saline) in an identical protocol. Animals were bled daily or every other day, and serum total estrogens, LH, PRL, and progesterone were determined by RIA. Serial laparoscopies were performed to visualize ovulation. Whereas animals treated with vehicle presented normal cycle lengths (26, 26, 29, 30, and 34 days), those treated with THC presented abnormal lengths (145, 76, 22, 94, and 59 days). All vehicle-treated cycles were ovulatory, while four of five THC cycles were anovulatory (P < 0.02). Five THC-treated animals were anovulatory in the posttreatment cycle. To determine the site of action of THC-induced anovulation, five animals received THC, human menopausal gonadotropin, and hCG simultaneously. All ovulated normally, as determined by laparoscopic visualization of stigma. Normal luteal phases were evidenced by normal luteal phase lengths and serum progesterone concentrations. These findings are of clinical relevance, since they were achieved with doses of THC that produce blood concentrations similar to those found in heavy marijuana users.