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PubMedDate not supplied

Theories regarding endocrine contributions to the onset of labor.

A review of the literature on endocrine factors influencing labor is presented. Treated separately are oxytocin, the prostaglandins, the fetus, and estrogen/progesterone. Implications for nursing practice and theory are discussed where appropriate, and the reader is encouraged to think of parturition as a complex interplay of factors.

Coitus↗
PubMed2002

Identification of suppressors of cytokine signaling (SOCS) proteins in human gestational tissues: differential regulation is associated with the onset of labor.

Inflammatory cytokines secreted by the placenta and fetal membranes are believed to play an important role in the initiation of parturition. The suppressor of cytokine signaling (SOCS) proteins regulate signal transduction by several cytokines that have been reported to affect gestational tissues. The presence, distribution and roles of SOCS proteins, however, have not been described in human gestational tissues. Using reverse transcriptase (RT)-PCR and Western blot analysis we investigated the expression of SOCS1, SOCS2, and SOCS3 mRNA and protein, respectively, by human villous placenta, amnion and choriodecidua (n = 3-4). Tissues were obtained from uncomplicated pregnancies at term after either spontaneous labor and vaginal delivery or caesarean section (before labor). Messenger RNAs for SOCS1, SOCS2, and SOCS3 were expressed in all tissue types, irrespective of labor status. SOCS proteins were, however, only detectable in villous placenta and in one case in the choriodecidua. Labor was associated with abrogated expression of SOCS1 and SOCS3 proteins in villous placenta and the choriodecidua sample. Following labor the band for SOCS2 protein increased slightly in size which may indicate post-translational modification of SOCS2. Reduced expression of SOCS proteins in gestational tissues may provide a mechanism by which inflammatory cytokines enter into a positive feedback loop of inflammatory changes leading to delivery.

Blotting, Western↗
PubMed1986

[Bradykinin receptor and the mechanism of the onset of labor].

Bradykinin (BK) receptor of uterus and chorionic membrane were studied by radioreceptor assay to clarify the role of BK as theta an agent contracting uterine muscle. Basic examination revealed that incubation at 0 degrees C for 45 minutes with [3H] BK in buffer containing 5mM Mg++ was the most suitable condition for receptor-BK binding. BK receptor assay of several kinds of tissue such as pregnant rat uterus, human chorionic membrane, and placenta was done and the following results were obtained. Specific BK receptor existed in human chorionic membrane and in rat uterus. Ultracentrifugation revealed that it was on the plasma membrane (145 f mole./mg protein: The highest binding in the pellet at 10,000 g centrifugation followed by 600 g centrifugation). Association constant (Ka) and maximal binding capacity (MBC) showed the lowest level at 15 days gestation in rat uterus. These seemed to effectively maintain pregnancy by inhibiting uterine contraction. Both Ka and MBC were increased in the uterus of intrapartum rat compared with that of prepartum, but the former was about 45%, and the latter was almost the same as, that of non pregnant rat.

Animals↗
PubMed1988

[Steroids' action on dependence of outset, maintenance of gravidity and onset of labor].

Dependence of outset, maintenance of gravidity and onset of labor on different kinds of steroid hormones has long been the focus of debate with the underlying control mechanism of these hormones in question remaining left unestablished still in these days. Of author's particular concern in this paper was the two-sided aspect of steroid functions. In fact, the steroid may stimulate mother's organ, fetus and placenta to produce much amount of steroid hormone throughout gravidic interval, while at the same time it may control the two contradictory processes, namely the maintenance of gravity and onset of labor through one and the same route. With a view to solve the complexity referred to above an effort has been made through a series of experiments particularity in the term of: 1. Dependent of a system capable to simultaneously determine concentrations of a variety of steroid hormones using the high performance liquid chromatography (HPLC); 2. Profile-analysis to be made on behavior of different kinds of steroids observable over gravidic interval under a support of HPLC system; 3. Behavior of different kinds of hemogenic hormones subsequent to an active DHAS loading in both group with- and without labor pains; 4. Influence of DHAS and gestation on activity of 11 beta hydroxy steroid dehydrogenase in placenta; Some of the results brought by these experiments, which are of some value to speculate on the mechanism of labor-onset and growth of fetus, may be summarized below in line with the preceding items: 1. The measuring system incorporating HPLC made it possible to determine 8 kinds of steroid hormones under systems of C19 and C21 readily in approx. 45 min., even when pretreatment is made involved in the procedure. It was also demonstrably verified that the system shows an acceptable sensitivity combined with a higher correlation with the RIA-method. 2. Profile was successfully delineated of those steroids which would participate in controlling the labor pains inducing mechanism through a series of analytical works made on the behavior of steroid associated with the process of gravidism. With the approach of expected labor, it was seen that 5 kinds of steroid hormones comprising DHA, testosterone, pregnenolone, 20 alpha OH-progesterone, and cortisol showed a marked increase. In contrast, androstenedione and progesterone begin to fall abruptly ever since several days preceding the date of labor. 3. Gain of DHA, 17 alpha OH-progesterone, due to DHAS-loading was clearly identified in the group with onset of labor pains.(ABSTRACT TRUNCATED AT 400 WORDS)

Chromatography, High Pressure Liquid↗
PubMed1991

An enzyme (beta-D-N-acetylglucosaminidase) released from the decidua to maternal plasma prior to the onset of labor.

Changes in the activity of beta-N-acetylglucosaminidase (E.C. 3.2.1.30; NAG), a lysosomal marker enzyme, in the maternal plasma and utero-placental tissues during late pregnancy and parturition were examined in order to determine if lysosomal enzymes participate in the cervical ripening. NAG activity in the plasma gradually increased as gestation advanced, to reach a maximum 3-4 days before the spontaneous onset of labor, and remaining at this level until the second stage. The activity measured in decidua and amnion obtained from the women who had undergone routine repeat cesarean section after labor onset was lower than in those before the onset. Since the decidua was much heavier than the amnion, it was concluded that NAG was released to the maternal circulation mainly from the decidua and only partly from the amnion. Our data revealed that lysosomal enzyme release occurs prior to the onset of labor, and that NAG may play a role primarily in the ripening of the cervix rather than in the onset of labor, by hydrolysing GAGs in the uterine cervix.

Acetylglucosaminidase↗
PubMed1995

Interleukin-8 synthesis and the onset of labor.

OBJECTIVE: To examine the role of cytokines in cervical dilation. METHODS: In 55 patients undergoing cesarean delivery, we took samples from the lower uterine segment, the decidua, and the membranes. We determined the concentrations of interleukin (IL)-2, IL-8, tumor necrosis factor-alpha, matrix metalloproteinase (MMP)-8, and MMP-9 in the different tissues. RESULTS: Depending on the state of labor, we observed a significant increase (P < .001) in IL-8 concentrations in the lower uterine segment. The leukocyte enzymes MMP-8 and MMP-9 were highly significantly correlated with the IL-8 concentrations. CONCLUSION: Interleukin-8 is critically involved in the process of parturition in humans. Interleukin-8 concentrations in the myometrium, decidua, and membranes correlated strongly with the observed MMP-8 and MMP-9 concentrations.

Cervix Uteri↗
PubMed2003

Comparison of potassium currents in human decidua before and after the onset of labor.

The human decidua plays a prominent role in the signaling between maternal and fetal tissues. It also secretes a plethora of molecules that modulate uterine function. Ion-channel activity underpins many cellular functions; however, the channels in human decidua have not been characterized in any detail. We have used the whole-cell recording mode of the patch-clamp technique to carry out current-clamp and voltage-clamp recordings of membrane properties and whole-cell potassium (K+) currents of freshly isolated decidual stromal cells. Decidual tissue was obtained from women after spontaneous vaginal delivery (SVD) or elective cesarean section (CS). Cells from both groups generated action potentials, the overshoots and durations of which were dependent on extracellular calcium levels, inhibited by cobalt and enhanced by barium. Potassium current (IK) density was higher in the CS than in the SVD group. Outwardly directed currents were heterogeneous with respect to their activation/inactivation profiles and exhibited outward rectification. The main difference between the SVD and CS group was the presence of a sustained current component in CS cells that is tetraethylammonium chloride-resistant and appears to be unaffected by E-4031. No evidence for the activation of any calcium-activated K+ currents was obtained. We propose that human parturition is associated with subtle changes in K+ channel remodeling, reflecting the transition from uterine quiescence to activation and stimulation. An understanding of the signal transduction events underlying these process may eventually lead to novel approaches to prevent preterm labor via decidual rather than myometrial intervention.

4-Aminopyridine↗