Use of hormonal contraceptives and occurrence of pregnancy-related pelvic pain: a prospective cohort study in Norway

BACKGROUND: Pregnancy-related pelvic pain is a common condition, and use of hormonal contraceptives before pregnancy has been proposed as a risk factor. We used data from a sub-sample of women participating in the "Norwegian Women and Cancer study" (NOWAC) to assess the association between hormonal contraceptive use and pelvic pain in pregnancy. METHODS: From a sub-group of 2078 parous women participating in the NOWAC study, information was collected from a self-instructive four-page questionnaire containing questions about lifestyle and medical conditions. We calculated odds ratios (OR) and 95% confidence intervals (CI), using unconditional logistic regression. RESULTS: In this study, the prevalence of pelvic pain in women was 26.5% during the first pregnancy and increased with parity. Use of hormonal contraceptives before a woman's first pregnancy was associated with an increased risk of pelvic pain in her first pregnancy (OR = 1.6; 95% confidence interval 1.2–2.2). There was no association between use of hormonal contraceptives and pelvic pain in the second or third pregnancy. Occurrence of pelvic pain in a previous pregnancy was the only factor associated with pelvic pain in subsequent pregnancies (OR = 51.1; 95% CI 32.9–79.5 in the second pregnancy and OR = 28.3; 95% CI 15.4–53.1 in the third pregnancy). CONCLUSION: Use of hormonal contraceptives was associated with an increased risk of pelvic pain in a woman's first pregnancy. The most important determinant of pelvic pain in the second or third pregnancy was the history of pelvic pain in the preceding pregnancy

Potassium Starvation in Yeast: Mechanisms of Homeostasis Revealed by Mathematical Modeling

The intrinsic ability of cells to adapt to a wide range of environmental conditions is a fundamental process required for survival. Potassium is the most abundant cation in living cells and is required for essential cellular processes, including the regulation of cell volume, pH and protein synthesis. Yeast cells can grow from low micromolar to molar potassium concentrations and utilize sophisticated control mechanisms to keep the internal potassium concentration in a viable range. We developed a mathematical model for Saccharomyces cerevisiae to explore the complex interplay between biophysical forces and molecular regulation facilitating potassium homeostasis. By using a novel inference method (“the reverse tracking algorithm”) we predicted and then verified experimentally that the main regulators under conditions of potassium starvation are proton fluxes responding to changes of potassium concentrations. In contrast to the prevailing view, we show that regulation of the main potassium transport systems (Trk1,2 and Nha1) in the plasma membrane is not sufficient to achieve homeostasis

Membranes with the Same Ion Channel Populations but Different Excitabilities

Electrical signaling allows communication within and between different tissues and is necessary for the survival of multicellular organisms. The ionic transport that underlies transmembrane currents in cells is mediated by transporters and channels. Fast ionic transport through channels is typically modeled with a conductance-based formulation that describes current in terms of electrical drift without diffusion. In contrast, currents written in terms of drift and diffusion are not as widely used in the literature in spite of being more realistic and capable of displaying experimentally observable phenomena that conductance-based models cannot reproduce (e.g. rectification). The two formulations are mathematically related: conductance-based currents are linear approximations of drift-diffusion currents. However, conductance-based models of membrane potential are not first-order approximations of drift-diffusion models. Bifurcation analysis and numerical simulations show that the two approaches predict qualitatively and quantitatively different behaviors in the dynamics of membrane potential. For instance, two neuronal membrane models with identical populations of ion channels, one written with conductance-based currents, the other with drift-diffusion currents, undergo transitions into and out of repetitive oscillations through different mechanisms and for different levels of stimulation. These differences in excitability are observed in response to excitatory synaptic input, and across different levels of ion channel expression. In general, the electrophysiological profiles of membranes modeled with drift-diffusion and conductance-based models having identical ion channel populations are different, potentially causing the input-output and computational properties of networks constructed with these models to be different as well. The drift-diffusion formulation is thus proposed as a theoretical improvement over conductance-based models that may lead to more accurate predictions and interpretations of experimental data at the single cell and network levels

Governing shipping externalities : Baltic ports in the process of SOx emission reduction

This paper analyses the debate which has unfolded in the Baltic Sea Region regarding the reduction of sulphur content in vessel fuels, in order to illustrate how tightening environmental regulation challenges traditional forms of maritime governance. Using an interactive governance approach, this study reconstructs the process of sulphur emission reduction as a complex multi-stakeholder interaction in multiple contexts. The empirical investigation has drawn on documentary material from around the Baltic region, including Russia, and has applied the method of qualitative content analysis. The empirical study focuses on two interlinked questions: (1) How sulphur emission reduction policies are being anticipated by maritime industry, in particular by Baltic ports and (2) How port adaptation strategies are tied into Baltic local and energy contexts. Addressing these questions highlights the role of polycentricity in shipping governance and explains how the same universal international regulations can produce varying patterns of governance. The paper concludes that policy-making shall take an account of the fact that the globalized shipping industry is nevertheless locally and sectorally embedded.Peer reviewe