Chronic stimulation of uterine prostaglandin synthesis during cervical ripening before the onset of labor

Concentrations of 13, 14-dihydro-15-keto-PGF2α (PGFM) were measured in plasma of six carefully selected primigravid women with an unripe cervix at term before and at various intervals after extra-amniotic insertion of a Foley catheter with or without methylhydroxyethylcellulose (Tylose^R) gel. The procedure caused an acute elevation of PGFM levels within 5 min (P < 0.025), which was maintained for at least 6 hours in the absence of uterine activation at 179 ± 32% of the initial values (P < 0.01). Extra-amniotic administration of Tylose gel caused an increase in PGFM levels which was both higher and more prolonged ( > 12 hours) than insertion of a Foley catheter alone.The observations indicate that cervical ripening without concomitant uterine activation is associated with an increase in PGFM levels. They also demonstrate that prolonged activation of (intra)uterine prostaglandin synthesis may occur several hours before the onset of labor-like uterine activity. A chance finding further suggests that spontaneous rupture of the membranes too may be preceeded by an increase in (intra)uterine prostaglandin synthesis. In their totality these observations lend strong support to the proposition that an increase in (intra)uterine prostaglandin production is a prerequisite to rather than a consequence of the initiation of labor.     

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.     

Specific glucocorticoid binding in human uterine tissues, placenta and fetal membranes

The binding of [3H]dexamethasone to cytosol fractions of human myometrium, endometrium, decidua, chorion, amnion and placenta has been studied. All tissues examined contained high affinity, low capacity binding sites with high specificity for glucocorticoids. Maximum specific binding of [3H]dexamethasone was reached after about 10 h at 0-4 degrees C and remained stable for at least the next 12 h. Sucrose density gradient analysis showed that the binding macromolecules sedimented at 7.9 S in hypotonic solutions and at 4.35 in solutions containing 0.4 M KCl. In the presence of sodium molybdate, the sedimentation coefficients shifted both in the absence and presence of 0.4 M KCl to 8.9 and 5.7 S, respectively. The apparent equilibrium dissociation constants (Kd) of the glucocorticoid binding sites were similar in most tissues, ranging between 1 and 6 nM, with the exception of the placenta in which the binding sites showed a higher Kd (13-22 nM). In all tissues studied, the binding affinities were similar in nonpregnant and pregnant patients and in patients at different stages of pregnancy or in labor. The concentration of the binding sites in the different tissues ranged from 11 to 268 fmol/mg protein, higher concentrations being found in myometrium, placenta and amnion and lower concentrations found in endometrium, chorion and decidua. The number of binding sites was higher in the myometrium of nonpregnant than pregnant women, but was similar in the myometrium of women at term pregnancy before or during labor. In the placenta, the number of binding sites increased significantly from early pregnancy to midpregnancy, while in chorion, amnion and decidua the number of binding sites did not change during pregnancy. It is concluded that human uterine tissues, placenta and fetal membranes contain specific binding sites with properties characteristic of glucocorticoid receptors suggesting that these tissues may respond directly to glucocorticoids.     

Expression of tumor necrosis factor-alpha and vascular endothelial growth factor in different zones of fetal membranes: a possible relation to onset of labor

This study aimed to explore whether the altered expression of tumor necrosis factor-alpha (TNF-α), vascular endothelial growth factor (VEGF) and apoptotic changes in mid zone (MZ) and rupture zone (RZ) of fetal membranes (FM) are regulatory mechanisms associated with labor at term. Fifteen FM specimens were collected after vaginal deliveries and 13 specimens after elective caesarian section. Histological and immunohistochemical analysis were employed. Area percent of TNF-α and VEGF immunostaining and apoptotic index (AI) were evaluated using image analysis. The statistical data revealed significantly higher area % for TNF-α, VEGF immunoexpression and AI in labor compared to non-labor specimens (p < 0.0001). There was a significantly higher percentage of TNF-α immunoexpressed area in MZ compared with RZ in both groups (p < 0.0001). VEGF expression in RZ of both groups proved nearly double or triple the area % of expression relative to MZ with highly significant difference (p < 0.0001). quantitative analysis revealed near two fold increase in the AI in RZ (13.42 % ± 1.2 in labor; 11.20 % ± 0.96 in non-labor groups) when compared to MZ (7.20 % ± 0.6 in labor; 5.08 % ± 0.76 in non-labor groups) with highly significant zonal difference (p < 0.0001). Correlation analysis revealed significant correlation between apoptotic indices and area % of TNF-α (r = 0.575, p = 0.002 in non-labor; r = 0.652, p < 0.0001 in labor) and VEGF (r = 0.795, p < 0.0001 in non-labor; r = 0.668, p < 0.0001 in labor). In conclusion, Apoptosis may be regulated by TNF-α and VEGF expression in FM at labor. MZ is a step back from RZ and could participate actively in rupture of the FM during labor. TNF-α and VEGF increase with onset of labor and differentially expressed in the RZ and the MZ. These findings call for further study with tissue cultures or animal models.     

Cytokeratin expression in squamous metaplasia of the human uterine cervix

The expression of cytokeratin polypeptides in squamous metaplasia of the human uterine cervix was investigated by immunocytochemical labeling with polypeptide-specific antibodies against cytokeratins. Immunofluorescence microscopic examination of cervical tissues using various monoclonal antibodies indicated that squamous cervical metaplasia expresses a unique set of cytokeratin polypeptides, this being distinctively different from that expressed by all of the normal epithelial elements of the exo- and endocervix. The development of metaplastic foci was accompanied by the expression of cytokeratin polypeptide no. 13, which is commonly detected in stratified epithelia, and by a reduction in the level of polypeptide no. 18, which is typical of simple epithelia. The 40-kilodalton cytokeratin (no. 19) described by Moll et al., which is abundant in the columnar and reserve cells of the endocervix, was found throughout the metaplastic lesions. Only in 'well-differentiated' metaplasias did we detect polarity of cytokeratin expression reminiscent of the staining patterns in the exocervix. This was manifested by the exclusive labeling of the basal cell layer(s) with antibodies KB 8.37 and KM 4.62, which stain the basal cells of the exocervix. Furthermore, a comparison of cervical metaplasia with squamous areas occurring within endometrial adenocarcinomas pointed to a close similarity in the cytokeratin expression of the two. We discuss the use of cytokeratins as specific markers of squamous differentiation, the relationships between squamous metaplasia and cervical neoplasia, and the involvement of reserve cells in the metaplastic process.     

Immunolocalization of proinflammatory cytokines in myometrium, cervix, and fetal membranes during human parturition at term.

Each of the proinflammatory cytokines interleukin (IL)-1beta, IL-6, IL-8, and tumor necrosis factor (TNF) alpha has been identified in reproductive tissues during labor. The cellular origin of these cytokines is unclear. The aim of this study was to localize these proinflammatory cytokines in myometrium (upper and lower segment), cervix, and fetal membranes at term. Biopsies were taken from women undergoing cesarean section either before or after the onset of labor. Immunohistochemistry was used to localize each of the cytokines IL-1beta, IL-6, IL-8, and TNFalpha. Leukocytes were localized using an antibody to CD45. In myometrium and cervix, immunostaining for IL-1beta was predominantly in leukocytes. In fetal membranes, IL-1beta localized to leukocytes and to the stromal cells of the decidua. In myometrium, IL-6, IL-8, and TNFalpha were restricted to leukocytes, which were present in greater numbers in tissue obtained during labor. In cervix, IL-6, IL-8, and TNFalpha localized to leukocytes and glandular and surface epithelium. IL-8 also localized to cervical stromal cells. In fetal membranes, IL-6 and TNFalpha were expressed by decidual stromal cells, infiltrating leukocytes, and extravillous trophoblasts. In membranes, IL-8 localized to leukocytes in the chorion but was not detected in the amnion. In fetal membranes collected at labor, IL-8 was expressed in decidual stromal cells. Infiltrating leukocytes are a major source of cytokines in uterine tissues during labor.     

Effect of weak inorganic acids and lower carboxylic acids on the conductivity of bilayer lipid membranes

The ability of weak inorganic acids (H₂S, HCN) and lower carboxylic acids to interact with bilayer lipid membranes, change their conductivity, and act as protonophores has been investigated. The mechanism of changes in membrane conductivity was studied. Factors influencing the interaction of acids with model lipid membranes were determined. Maximum changes in conductivity were observed at pH values equal to the dissociation constants of weak acids and correlated with the octanol-water partition coefficients.     

Longitudinally and circularly measured EMG activity in the human uterine cervix during labour

The role of the smooth cervical muscle has not yet been sufficiently explored. For that reason cervical EMG was measured during induced labour of several primiparas and multiparas. Three spiral electrodes were placed on the cervix in order to measure the EMG in the longitudinal and circular direction referred to the cervical axis. A quantitative analysis of changes in the amplitude and frequency of the EMG signals was performed by means of the spectral method. It was found that the EMG measured from the two leads differed in unripe cervices in the latent phase of labour. The differences are illustrated by two cases. Some possible explanations for the different activity are discussed.     

Evolution of the elastic fiber network of the human uterine cervix before, during and after pregnancy. A quantitative evaluation by automated image analysis

To assess the evolution of the elastic fiber network of the human uterine cervix before, during and after pregnancy, biopsy samples were obtained from 49 women. The high affinity of the polyphenolic compound (+)-catechin for elastin was used to stain the elastic fibers selectively, and enabled automated image analysis. In the human uterine cervix, the elastic fiber network is made up of: (1) fibers running parallel to the basement lamina of the epithelium, and (2) thinner, perpendicular fibers. Quantification using automated image analysis shows a decline in the cervical elastin content from a prepregnancy level of 1.33 +/- 0.08 (SEM) to 0.73 +/- 0.09% (Vv) at the end of pregnancy. In parallel with a constant decline, dissociation and disorganization of the fibers become more clearly evident as pregnancy progresses. However, by 5-7 weeks postpartum the elastic fiber network appears almost completely restructured. These changes support a role of elastin in the processes of cervical maturation and reconstruction during pregnancy and after delivery.     

Cytologic and hormonal findings in a carcinoid tumor of the uterine cervix

A carcinoid tumor of the cervix in a 40-year-old woman was studied by cytology, histology, electron microscopy, immunohistochemistry and hormonal analysis. The preoperative cytologic and histologic findings strongly suggested a carcinoid tumor of the cervix. The serum serotonin level was elevated; immunohistochemical studies demonstrated the presence of serotonin in the cytoplasm of the tumor cells. Following radical hysterectomy, the concentration of serotonin was measured in the excised tumor; it was about 20 times higher than the level seen in normal cervical tissue, confirming that the tumor was a serotonin-secreting carcinoid of the uterine cervix.     

Cloning and characterization of the DNA of a new human papillomavirus from a woman with dysplasia of the uterine cervix.

A previous analysis of 121 female genital tract lesions from the United States and South America had revealed that a large number contained DNA sequences that were weakly homologous to a panel of human papillomavirus (HPV) probes. The DNA sequences of one of these viruses have been molecularly cloned and shown to be a new type of HPV which is called HPV 31. Among the cloned HPV genomes, HPV 31 is most closely related to HPV 16. Although absent from all genital condylomas studied, HPV 31 was present in approximately 20% of the mild and moderate dysplasias and in 6% of the invasive cervical cancers     

Establishment and characterization of a lymphoepithelial-like carcinoma cell line (HUUCLEC) derived from the human uterine cervix

A cell line designated HUUCLEC was established from a human uterine cervical lymphoepithelial carcinoma obtained from a 61-year-old Japanese woman. The cell line has grown slowly without interruption and serial passages were successively carried out 60 times within 3 years. The cultured cells were spindle or round in shape, showing anaplastic and pleomorphic features, a pavement cell arrangement and multilayering without contact inhibition. The population doubling time of the HUUCLEC line was 72 hours while the chromosomal number varied widely and showed aneuploidy. The modal chromosomal number was stable at the triploid range and marker chromosomes were present; the Ebstein-Barr virus was absent in the cultured cells.     

Immunohistochemistry of carbonic anhydrase in human placenta and fetal membranes

The localization of human carbonic anhydrase (CA) isoenzymes HCA I, HCA II, and rat CA II have been studied in human umbilical cord, chorion laeve including amnion and placenta from first and second trimester and also from term pregnancies. Detection techniques of immunofluorescence and immunoperoxidase were used in cryostat and paraffin sections. Both isoenzymes were found in the villous syncytiotrophoblast throughout pregnancy. HCA I staining patterns in the villous endothelium were highly variable whereas increasing immunoreactivity levels of endothelial HCA II were detected as pregnancy advances. The extravillous cytotrophoblast showed generally weaker levels of immunoreactivity. In amnionic epithelium of membranes, chorionic plate and umbilical cord, higher activities for HCA I, HCA II and rat CA II were found than in all other localizations. Our findings emphasize the importance of enzyme mediated bicarbonate/CO₂ removal from the feto-placental unit as opposed to simple bicarbonate diffusion or carrier mediated transport. As effective transfer routes should be considered not only umbilical cord — placental villi — intervillous space, but also fetal kidney — amnionic fluid — amnion — uterine vessels.