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The predictive capabilities of models that satisfy the Weiner bounds and Hashin-Shtrikman (HS) bounds were studied for isotropic dielectrics in a laminar heterogeneous configuration oriented perpendicular to the electric field. The dynamics were investigated isothermally using broadband dielectric relaxation spectroscopy (DRS) in the frequency range of 1 MHz to 100 mHz. The molecules chosen for study were low molecular weight glass formers, glycerol, phenyl salicylate, imidazole, and dimethyl sulfoxide, and macromolecules, polymethylhydrosiloxane, polyvinylpyrrolidone-co-vinyl acetate, poly-dl-lactic acid, and poly l-lactic acid. It was found that none of the models were able to adequately predict in entirety the resultant dynamics. Of the models studied, the most successful were the HS upper bound (HSUB), the complementary universal Weiner equation (CWE), and the Lichtenecker model for the dimensional parameter, ζ = -1/2. The least successful models were the upper Weiner bound (UWB), the Neelakantaswamy, Turkman, and Sarkar (NTS) model for ζ = 1/2, and the Lichtenecker model for ζ = 1/2.

The molecular mass of the polysaccharide hyaluronan (HA) is an important determinant of its biological activity and physicochemical properties. One method currently used for the analysis of the molecular mass distribution of an HA sample is gel electrophoresis. In the current work, an improved agarose gel electrophoresis method for analysis of high molecular mass HA is presented and validated. HA mobility in 0.5% agarose minigels was found to be linearly related to the logarithm of molecular mass in the range from approximately 200 to 6000 kDa. A sample load of 2.5 μg for polydisperse HA samples was employed. Densitometric scanning of stained gels allowed analysis of the range of molecular masses present in the sample as well as calculation of weight-average and number-average values. The method was validated for a polydisperse HA sample with a weight-average molecular mass of approximately 2000 kDa. Excellent agreement was found between the weight-average molecular mass determined by electrophoresis and that determined by rheological measurement of the solution viscosity. The revised method was then used to show that heating solutions of HA at 100°C, followed by various cooling procedures, had no effect on the HA molecular mass distribution., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Objective: We determined the relative abundance of prostaglandin endoperoxide H synthase type 1 and type 2 messenger ribonucleic acid levels in the human fetus and newborn infant., Study Design: We used ribonuclease protection assays and normalized values to messenger ribonucleic acid of cyclophilin. Tissues were obtained from all 3 trimesters and in the first 9 days of the newborn period., Results: Prostaglandin endoperoxide H synthase type 1 and type 2 messenger ribonucleic acid is present in every fetal tissue examined (lung, kidney, intestine, heart, brain, and stomach). Kidney and lung demonstrated no changes in the expression of prostaglandin endoperoxide H synthase type 1 messenger ribonucleic acid with gestational age, whereas postnatal levels in lung were one third those in the first trimester (P <.05). A large increase (5-fold to 30-fold; P <.05) occurred throughout gestation for the expression of prostaglandin endoperoxide H synthase type 2 messenger ribonucleic acid in intestine, lung, and kidney, which extended into the newborn period for lung and kidney., Conclusions: These data imply that the expression of prostaglandin endoperoxide H synthase type 2 messenger ribonucleic acid may be responsible for prostaglandin-related effects and is coordinated in several human fetal tissues in late gestation.

Objective: To determine the relationship of prostaglandin endoperoxide H synthase (PGHS) expression in the gestational tissues and fetal fibronectin in cervico-vaginal fluids before the onset of labour at term., Design: Cross-sectional, observational study., Samples: Amnion, chorion laeve and decidua were collected from 24 term pregnant women following elective caesarean section. Samples of cervico-vaginal secretions were obtained from the same women immediately before caesarean section., Methods: PGHS-1 and PGHS-2 mRNA levels in tissues were determined by specific ribonuclease protection assays. Fetal fibronectin concentrations in the cervico-vaginal fluids were measured by enzyme-linked immunosorbent assay. The abundance of PGHS mRNA was compared between groups of patients with the same mean gestational age but different cervico-vaginal fetal fibronectin levels. Linear regression analysis was used to determine the association between PGHS levels and fetal fibronectin., Results: Two groups of women were identified who had significantly different fetal fibronectin values but the same gestational ages. The group with the higher fetal fibronectin concentrations had significantly higher PGHS- 1 and PGHS-2 mRNA levels in the chorion laeve and higher PGHS-2 mRNA levels in the amnion, than the group with lower fetal fibronectin concentrations. PGHS- 1 and PGHS-2 mRNA levels in the chorion laeve and PGHS-2 mRNA in the amnion showed an overall significant association with fetal fibronectin levels., Conclusions: High concentrations of fetal fibronectin in cervico-vaginal secretions before the onset of spontaneous labour at term are associated with high levels of PGHS-2 mRNA in the chorion laeve and the amnion and of PGHS- 1 mRNA in the chorion laeve. Increased expression of PGHS in these tissues may therefore be involved in the events leading to term birth.

Human amnion cells in primary culture respond to glucocorticoids in a characteristic fashion by the increased expression of the inducible prostaglandin endoperoxide H synthase isoenzyme, PGHS-2. Since PGHS-2 induction by agonists generally involves tyrosine kinases, we examined the possibility that the glucocorticoid stimulation of PGHS-2 in the amnion cells is tyrosine kinase dependent. PGHS-2 expression was stimulated in confluent, serum-starved amnion cells with dexamethasone, and the effect of the tyrosine kinase inhibitors herbimycin A and tyrphostins AG126, AG1288, and A1 on enzyme activity induction was determined. All four inhibitors blocked the increase of PGHS activity in a concentration-dependent manner with IC50 values of 0.077 +/- 0.05, 15.38 +/- 5.14, 20.91 +/- 3.1, and 29.77 +/- 8.21 microM, respectively (mean +/- SE, n = 4). Dexamethasone increased (approximately twofold) the tyrosine phosphorylation of 120-, 110-, and 77-kDa proteins in cell extracts, and herbimycin A selectively blocked the phosphorylation of the 110-kDa phosphoprotein. The stimulation of the steady-state level of PGHS-2 mRNA by dexamethasone was also inhibited by herbimycin A. These results suggest that glucocorticoids induce PGHS-2 expression in amnion cells with the involvement of tyrosine kinase(s). The role of tyrosine kinase dependent mechanisms in the control of amnion cell responsiveness to corticosteroids remains to be established.

Prostaglandin H2 synthase (PGHS)-1 and PGHS-2 expression was examined in primary cultures of human amnion cells, an in vitro model of amnion tissue. Epidermal growth factor (EGF), the protein kinase C (PKC) activating phorbol ester TPA, and the protein phosphatase inhibitor, okadaic acid (OA), stimulated PGHS activity and the level of PGHS-2 mRNA, but did not affect the level of PGHS-1 mRNA. In situ hybridization suggested that the same population of cells responded to EGF, TPA and OA. Okadaic acid promoted PGHS activity independently of PKC. EGF stimulated the activity of extracellular signal-regulated protein kinase (Erk) and N-terminal c-Jun kinase (Jnk). OA increased Jnk activity but had no effect on Erk activity, while TPA had no influence on either Erk or Jnk activity. PD098059, a selective inhibitor of the Erk-activating kinase MEK, blocked the stimulation of PGHS expression by EGF, but did not decrease stimulation in response to OA. Herbimycin A, a tyrosine kinase inhibitor, suppressed the stimulation of PGHS activity and PGHS-2 mRNA abundance by all three stimulants, and blocked signalling via the Erk and Jnk mitogen-activated protein kinase pathways. Thus, growth factor stimulation, PKC activation and protein phosphatase inhibition induced the expression of PGHS-2 in primary amnion cells by distinct regulatory mechanisms involving tyrosine kinase(s). Tyrosine kinase inhibitors may constitute a new category of PGHS-2 inhibitors that act by blocking the expression of the enzyme., (Copyright 1998 Elsevier Science B.V.)

Objective: To determine the labor-related changes of prostaglandin endoperoxide H synthase (PGHS) activity and PGHS-1 and -2 abundance in term decidua and to assess the contribution of the PGHS isoforms to the total PGHS activity present in the tissue., Methods: Decidua was collected after elective cesarean delivery (CD) or spontaneous labor (SL) at term. Prostaglandin endoperoxide H synthase activity was determined in microsomal fractions, and PGHS-1 and -2 mRNA levels were measured by ribonuclease protection assays. Prostaglandin endoperoxide H synthase-1 and -2 mRNAs were localized in tissue sections by in situ hybridization., Results: Prostaglandin endoperoxide H synthase specific activity in decidua microsomes at CD was 111 +/- 3 pg prostaglandin-E2/minute/microgram protein (mean +/- standard error, N = 10 patients), not different from enzyme activity measured after SL (110 +/- 27 N = 10 patients, P = .97, Wilcoxon's rank sum test). Prostaglandin endoperoxide H synthase-1 mRNA abundance in CD tissues was 0.283 +/- 0.047 relative densitometric units (mean +/- standard error, n = 26 patients), which did not change with labor (SL: 0.329 +/- 0.073, n = 20 patients, P = .68). Prostaglandin endoperoxide H synthase-2 mRNA abundance was also unaffected by labor (CD: 0.933 +/- 0.255, n = 27 patients; SL: 0.714 +/- 0.179, n = 23 patients, mean +/- standard error, P = .66). Prostaglandin endoperoxide H synthase specific activity was positively and significantly (P < .05) correlated with both PGHS-1 and -2 mRNA levels. In situ hybridization showed the pervasive presence of both PGHS mRNAs in decidua cells with no detectable changes associated with labor., Conclusion: Both isoforms of PGHS are present in term decidua and contribute to enzyme activity and prostaglandin production. Mechanisms regulating decidual prostanoid biosynthesis at labor do not involve changing the levels of expression of the two PGHS isoforms.

Parturition is a process that is composed of five separate and distinct physiological components but which lead from one to the next and are, therefore, interdependent. As such, the regulation of myometrial contractility should not be examined in isolation but as part of this continuum. The initiation of labor begins with the biochemical events that result in the rupture of the fetal membranes, effacement of the cervix, and the switch from contractures to contractions. Because we have defined being in labor as the point at which contractions no longer revert to contractures, we suggest that labor is superimposed upon pregnancy in humans and nonhuman primates. There is no withdrawal or retreat from pregnancy, and no evidence exists that the concentrations or actions of progesterone diminish at term. Rather, the target tissues of labor are activated to perform their physiological functions, and these functions are initiated by stimulators. The best candidate for achieving activation is maternal estrogen, derived from fetal DHEAS, but major gaps in our knowledge of this process still exist. Prostaglandins are the most likely candidates as the stimulators of labor initiation, but close inspection of their precise roles also demands that clearer definition of their synthesis and actions be acquired. Coordination of and communication between the physiological events of labor motivates us to examine nontraditional mediators such as cytokines for their potential roles in the regulation of these events at normal term.

The activities of glucose-6-phosphatase (G6P), fructose diphosphatase, phosphoenolpyruvate carboxykinase (PEPCK), aspartate and alanine transferases were measured in liver and kidney of fetal foals between 100-318 days of gestation (term approximately 335 days) and during the immediate postnatal period (0-48 h after birth). All 5 enzymes could be detected in the fetal liver and kidney at the youngest gestational age studied. Mean fetal activities were lower than those observed in their mothers and showed no change with gestational age for the majority of enzymes studied. However, renal PEPCK and renal and hepatic G6P did increase towards term. At birth, hepatic and renal activities of these two enzymes were higher than those found in late gestation or in the adult animals. There was no apparent change in the activities of any of the other enzymes at birth. In late gestation (80-90% gestation), the activities of G6P and PEPCK in the foal were low compared to those in other species at the same stage of gestation. Similarly, the perinatal increase in enzyme activity occurred closer to term in the foal than in most other species. These observations indicate that maturation of glucogenic capacity occurs relatively late in the fetal foal and suggests that this process may be dependent on the prepartum rise in fetal cortisol as occurs in other species.