Occurrence and biodegradation of hydrocarbons at high salinities.

Hypersaline environments are found around the world, above and below ground, and many are exposed to hydrocarbons on a continuous or a frequent basis. Some surface hypersaline environments are exposed to hydrocarbons because they have active petroleum seeps while others are exposed because of oil exploration and production, or nearby human activities. Many oil reservoirs overlie highly saline connate water, and some national oil reserves are stored in salt caverns. Surface hypersaline ecosystems contain consortia of halophilic and halotolerant microorganisms that decompose organic compounds including hydrocarbons, and subterranean ones are likely to contain the same. However, the rates and extents of hydrocarbon biodegradation are poorly understood in such ecosystems. Here we describe hypersaline environments potentially or likely to become contaminated with hydrocarbons, including perennial and transient environments above and below ground, and discuss what is known about the microbes degrading hydrocarbons and the extent of their activities. We also discuss what limits the microbial hydrocarbon degradation in hypersaline environments and whether there are opportunities for inhibiting (oil storage) or stimulating (oil spills) such biodegradation as the situation requires.

Use of a Hepatitis C Screening Order Set to Improve Screening Rates and Measure Intervention Effectiveness.

INTRODUCTION: Hepatitis C virus (HCV) infection leads to significant morbidity and mortality. Rates of HCV infection are greatest in patients born from 1945 to 1965, so the Centers for Disease Control recommends a one-time screening in this cohort. Previous interventions utilizing the electronic medical record (EMR) capabilities at two University of Utah Family Medicine clinics have increased screening rates significantly, but further improvement is possible. METHODS: A family medicine resident-led continuous quality improvement (CQI) team used the Model for Improvement methods popularized by the Institute for Healthcare Improvement to create a team-based intervention with the goal of improving HCV screening in a family medicine faculty and resident clinic. An order set was created and a protocol developed that allowed medical assistants or clinic phlebotomists to order the appropriate HCV screening lab if this had not yet been done by the primary care provider. Data were extracted from the EMR that showed changes in total and monthly screening rates as well as the frequency of order set use. RESULTS: Monthly screening rates at the Madsen Family Medicine Clinic (Salt Lake City, UT) increased from approximately 40% to greater than 50% in the 5-month intervention period. The order set was used 19 times during this period which accounted for 18.8% of new screens. CONCLUSIONS: Creating an order set that allows medical assistants to order the HCV screening lab increased HCV screening rates in our clinic. Because order set utilization data can be extracted from the EMR, this intervention provided a process measure that can differentiate the effect of this intervention from the effects of other interventions previously undertaken in the clinic.

Chronic alcohol feeding potentiates hormone-induced calcium signalling in hepatocytes.

KEY POINTS: Chronic alcohol consumption causes a spectrum of liver diseases, but the pathogenic mechanisms driving the onset and progression of disease are not clearly defined. We show that chronic alcohol feeding sensitizes rat hepatocytes to Ca2+ -mobilizing hormones resulting in a leftward shift in the concentration-response relationship and the transition from oscillatory to more sustained and prolonged Ca2+ increases. Our data demonstrate that alcohol-dependent adaptation in the Ca2+ signalling pathway occurs at the level of hormone-induced inositol 1,4,5 trisphosphate (IP3 ) production and does not involve changes in the sensitivity of the IP3 receptor or size of internal Ca2+ stores. We suggest that prolonged and aberrant hormone-evoked Ca2+ increases may stimulate the production of mitochondrial reactive oxygen species and contribute to alcohol-induced hepatocyte injury. ABSTRACT: 'Adaptive' responses of the liver to chronic alcohol consumption may underlie the development of cell and tissue injury. Alcohol administration can perturb multiple signalling pathways including phosphoinositide-dependent cytosolic calcium ([Ca2+ ]i ) increases, which can adversely affect mitochondrial Ca2+ levels, reactive oxygen species production and energy metabolism. Our data indicate that chronic alcohol feeding induces a leftward shift in the dose-response for Ca2+ -mobilizing hormones resulting in more sustained and prolonged [Ca2+ ]i increases in both cultured hepatocytes and hepatocytes within the intact perfused liver. Ca2+ increases were initiated at lower hormone concentrations, and intercellular calcium wave propagation rates were faster in alcoholics compared to controls. Acute alcohol treatment (25 mm) completely inhibited hormone-induced calcium increases in control livers, but not after chronic alcohol-feeding, suggesting desensitization to the inhibitory actions of ethanol. Hormone-induced inositol 1,4,5 trisphosphate (IP3 ) accumulation and phospholipase C (PLC) activity were significantly potentiated in hepatocytes from alcohol-fed rats compared to controls. Removal of extracellular calcium, or chelation of intracellular calcium did not normalize the differences in hormone-stimulated PLC activity, indicating calcium-dependent PLCs are not upregulated by alcohol. We propose that the liver 'adapts' to chronic alcohol exposure by increasing hormone-dependent IP3 formation, leading to aberrant calcium increases, which may contribute to hepatocyte injury.

Reliable encoding of stimulus intensities within random sequences of intracellular Ca2+ spikes.

Ca(2+) is a ubiquitous intracellular messenger that regulates diverse cellular activities. Extracellular stimuli often evoke sequences of intracellular Ca(2+) spikes, and spike frequency may encode stimulus intensity. However, the timing of spikes within a cell is random because each interspike interval has a large stochastic component. In human embryonic kidney (HEK) 293 cells and rat primary hepatocytes, we found that the average interspike interval also varied between individual cells. To evaluate how individual cells reliably encoded stimuli when Ca(2+) spikes exhibited such unpredictability, we combined Ca(2+) imaging of single cells with mathematical analyses of the Ca(2+) spikes evoked by receptors that stimulate formation of inositol 1,4,5-trisphosphate (IP3). This analysis revealed that signal-to-noise ratios were improved by slow recovery from feedback inhibition of Ca(2+) spiking operating at the whole-cell level and that they were robust against perturbations of the signaling pathway. Despite variability in the frequency of Ca(2+) spikes between cells, steps in stimulus intensity caused the stochastic period of the interspike interval to change by the same factor in all cells. These fold changes reliably encoded changes in stimulus intensity, and they resulted in an exponential dependence of average interspike interval on stimulation strength. We conclude that Ca(2+) spikes enable reliable signaling in a cell population despite randomness and cell-to-cell variability, because global feedback reduces noise, and changes in stimulus intensity are represented by fold changes in the stochastic period of the interspike interval.