Inhibition of KCa2.2 and KCa2.3 channel currents by protonation of outer pore histidine residues

Ion channels are often modulated by changes in extracellular pH, with most examples resulting from shifts in the ionization state of histidine residue(s) in the channel pore. The application of acidic extracellular solution inhibited expressed K_Ca2.2 (SK2) and K_Ca2.3 (SK3) channel currents, with K_Ca2.3 (pIC₅₀ of ∼6.8) being approximately fourfold more sensitive than K_Ca2.2 (pIC₅₀ of ∼6.2). Inhibition was found to be voltage dependent, resulting from a shift in the affinity for the rectifying intracellular divalent cation(s) at the inner mouth of the selectivity filter. The inhibition by extracellular protons resulted from a reduction in the single-channel conductance, without significant changes in open-state kinetics or open probability. K_Ca2.2 and K_Ca2.3 subunits both possess a histidine residue in their outer pore region between the transmembrane S5 segment and the pore helix, with K_Ca2.3 also exhibiting an additional histidine residue between the selectivity filter and S6. Mutagenesis revealed that the outer pore histidine common to both channels was critical for inhibition. The greater sensitivity of K_Ca2.3 currents to protons arose from the additional histidine residue in the pore, which was more proximal to the conduction pathway and in the electrostatic vicinity of the ion conduction pathway. The decrease of channel conductance by extracellular protons was mimicked by mutation of the outer pore histidine in K_Ca2.2 to an asparagine residue. These data suggest that local interactions involving the outer turret histidine residues are crucial to enable high conductance openings, with protonation inhibiting current by changing pore shape.     

Consumption of pentane by hepatic microsomes and consequences on pentane measurement in exhaled gases

Pentane measurement in exhaled gases was proposed as a safe method to evaluate the importance of lipoperoxidation in vivo, in man and in animals. However we have observed that pentane, which arises from lipoperoxide decomposition, is significantly consumed by cytochrome P-450-rich liver microsomes. This pentane consumption is completely inhibited after heating the microsomes at 100 degrees C, and is considerably reduced by metyrapone, a cytochrome P-450 inhibitor. Hepatic metabolism of pentane, particularly after cytochrome P-450 induction, constitutes a risk of error, when pentane exhalation is taken as an index of lipoperoxidation in vivo.     

Cell-free synthesis of hemocyanin from the scorpion Androctonus australis. Characterization of the translation products by monospecific antisera

Translation of Androctonus australis poly(A)-RNA in vitro led to a number of polypeptides products (8-10) of 70-73 kDa analyzed by two-dimensional gel electrophoresis and identified by immunoprecipitation with an anti-(dissociated hemocyanin) antiserum. The translated hemocyanin polypeptides have the same physico-chemical characteristics as authentic hemocyanin subunits. Subunits Aa 2 and Aa 4 have been identified with monospecific antisera characterized (a) by their capability of reacting with their homologous subunit and (b) by their inability of binding to cross-reacting subunits. Each polypeptide chain is coded by a different messenger without significant post-translational events. Hemocyanin could be detected among the translation products of the poly(A)-RNA isolated from the cuticle under the carapace.     

Pattern of protein phosphorylation in intact stimulated cells: thyrotropin and dog thyroid

Two-dimensional, high-resolution electrophoretic technique of O'Farrell has been adapted to the analysis of thyroid phosphorylated proteins. Proteins were extracted from dog thyroid slices which had been incubated in the presence of [32P]phosphate with thyrotropin or with different agents which enhance the intracellular accumulation of cyclic AMP. About 350 phosphorylated polypeptides have been separated. Thyrotropin stimulates the phosphorylation of at least eight of these polypeptides. An increase in the phosphorylation of the same polypeptides was observed was observed when dog thyroid slices were incubated with dibutyryl adenosine 3':5'-monophosphate, cholera toxin or prostaglandin E1 instead of thyrotropin. Our results confirm that most of dog thyroid protein phosphorylation is independent of cyclic AMP. They offer a first link between the action of cyclic AMP on protein kinase and the physiological effects of thyrotropin. They strongly substantiate the hypothesis that most thyrotropin effects are mediated by cyclic AMP.     

Urticating hairs of "brown-tail" moth (Euproctis chrysorrhoea L.) (Lepidoptera): preliminary studies in urban and laboratory

Urticating hairs of the brown-tail moth (Euproctis chrysorrhoea L.) are detectable in the air using apparatus designed for the collection of airborne microorganisms and pollen research studies. The hairs are produced by caterpillars and are distributed by air currents or via moths. They were collected in Bordeaux. In the laboratory a nycthemeral cycle of hair emission is observed and is correlated with the biological activities of these species.     

Classification moléculaire des cancers du sein : utilité en clinique

In spite of the progress of treatments and the discovery of targeted therapies, breast cancer remains the leading cause of cancer mortality among women. It is also the first cancer to get benefits from target therapies against hormone receptors and now HER2. The anatomoclinical classification used to optimize the therapeutics is not always accurate and is a cause of overtreatments or of inappropriate treatments. Tumour cells genomic studies have shown the relationship between genomic alterations and the prognosis and the efficacy of treatments. The molecular classification which results from those studies allowed the emergence of numerous diagnostic tests. They use different technologies and different clinical approaches which should allow a better classification in order to be able to propose a personalized therapy. In this review, eight molecular tests are estimated compared to their scientific validation and to their clinical utility. Protein assays are also reviewed as uPA/PAI-1, the only prognostic marker validated with a level of evidence 1.     

Comparison of three devices for the automated detection of estrus in dairy cows

Considerable technological advances have been made in the automated detection of estrus in dairy cattle, but few studies have evaluated their relative performance on the same animals or assessed cow-related factors that affect their performance. Our objective was to assess the performance and reliability of three devices commercially available in France for cow estrus detection. The devices were a pedometer (PM; Afitag) and two activity meters (AM1; Heatime-RuminAct, and AM2; HeatPhone). Two algorithms were tested for AM2. We fitted 63 lactating Holstein cows with the three detectors from calving to 90 days after calving. The onset and pattern of cyclicity were monitored from 7 to 90 days postpartum measuring progesterone concentration in milk twice weekly. A total of 211 ovulations were identified. Cyclicity was classified as normal in 60% of cows (38/63). Calculated over the operating period of all the devices (179 periods of estrus), the sensitivities and positive predictive values were, respectively, 71% and 71% for PM, 62% and 84% for AM1, 61% and 67% for the first algorithm of AM2, and 62% and 87% for the second algorithm of AM2. Both activity meters had a lower sensitivity but a higher positive predictive value than the PM (P < 0.05). For all devices, the performance in estrus detection was much poorer at the first postpartum ovulation than at subsequent ovulations (P < 0.05). Lactation rank and milk production affected some devices (P < 0.05). These devices could be used to reinforce visual observations, especially after 50 days postpartum, the minimum recommended delay to insemination. However, their full benefit remains to be verified in different farming systems and taking into account the specific objectives of the dairy farmer.