Monitoring Cl- movement in single cells exposed to hypotonic solution

Self-referencing ion--selective electrodes (ISEs), made with Chloride Ionophore I-Cocktail A (Fluka), were positioned 1-3 microm from human embryonic kidney cells (tsA201a) and used to record chloride flux during a sustained hyposmotic challenge. The ISE response was close to Nernstian when comparing potentials (VN) measured in 100 and 10 mM NaCl (deltaVN = 57 +/- 2 mV), but was slightly greater than ideal when comparing 1 and 10 mM NaCl (deltaVN = 70 +/- 3 mV). The response was also linear in the presence of 1 mM glutamate, gluconate, or acetate, 10 microM tamoxifen, or 0.1, 1, or 10 mM HEPES at pH 7.0. The ISE was approximately 3 orders of magnitude more selective for Cl- over glutamate or gluconate but less than 2 orders of magnitude move selective for Clover bicarbonate, acetate, citrate or thiosulfate. As a result this ISE is best described as an anion sensor. The ISE was 'poisoned' by 50 microM 5-nitro-2-(3phenylpropyl-amino)-benzoic acid (NPPB), but not by tamoxifen. An outward anion efflux was recorded from cells challenged with hypotonic (250 +/- 5 mOsm) solution. The increase in efflux peaked 7-8 min before decreasing, consistent with regulatory volume decreases observed in separate experiments using a similar osmotic protocol. This anion efflux was blocked by 10 microM tamoxifen. These results establish the feasibility of using the modulation of electrochemical, anion-selective, electrodes to monitor anions and, in this case, chloride movement during volume regulatory events. The approach provides a real-time measure of anion movement during regulated volume decrease at the single-cell leve

Evolutionary ecology during the rise of dioxygen in the Earth's atmosphere

Pre-photosynthetic niches were meagre with a productivity of much less than 10−4 of modern photosynthesis. Serpentinization, arc volcanism and ridge-axis volcanism reliably provided H2. Methanogens and acetogens reacted CO2 with H2 to obtain energy and make organic matter. These skills pre-adapted a bacterium for anoxygenic photosynthesis, probably starting with H2 in lieu of an oxygen ‘acceptor’. Use of ferrous iron and sulphide followed as abundant oxygen acceptors, allowing productivity to approach modern levels. The ‘photobacterium’ proliferated rooting much of the bacterial tree. Land photosynthetic microbes faced a dearth of oxygen acceptors and nutrients. A consortium of photosynthetic and soil bacteria aided weathering and access to ferrous iron. Biologically enhanced weathering led to the formation of shales and, ultimately, to granitic rocks. Already oxidized iron-poor sedimentary rocks and low-iron granites provided scant oxygen acceptors, as did freshwater in their drainages. Cyanobacteria evolved dioxygen production that relieved them of these vicissitudes. They did not immediately dominate the planet. Eventually, anoxygenic and oxygenic photosynthesis oxidized much of the Earth's crust and supplied sulphate to the ocean. Anoxygenic photosynthesis remained important until there was enough O2 in downwelling seawater to quantitatively oxidize massive sulphides at mid-ocean ridge axes

Importance of hand germ contamination in health-care workers as possible carriers of nosocomial infections Importância da contaminação das mãos por germes, em trabalhadores da saúde, como possíveis transmissores de infecções hospitalares

The importance of hands in the transmission of nosocomial infection has been world wide admitted. However, it is difficult to induce this behavior in health-care workers. The aim of the present work was to point out the importance of hand bacteria colonization, the influence of hand washing and of patient physical examination. One hundred health-care workers were randomly divided in two groups: Group A without hand washing previous to patient physical examination or handling (PPE); group B with hand washing previous to PPE. Direct fingerprint samples in Columbia agar before and after PPE were obtained. The colonies were counted and identified by conventional techniques, and antibiograms according to NCCLS were performed. Before PPE group A participants showed a high number of bacteria regarding group B participants (73.9 Vs 20.7; p < 0.001); 44 out of 50 participants were carriers of potentially pathogen bacteria. No group B participants were carriers of potential pathogen bacteria before PPE. The latter group showed an increase in number of bacteria after PPE (20.7 CFU (before) Vs 115.9 CFU (after); p < 0.001). Sixteen group B participants were contaminated after PPE with potential pathogens such as S. aureus (50% of them meticillin resistant); Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis, half of them multiresistant. We can conclude on the importance of these results to implement educational programs and to provide the health-care workers with the proper commodities to fulfill this practice.<br>A importância das mãos na transmissão de infecções hospitalares é aceita mundialmente. Todavia, é difícil introduzir este procedimento entre os trabalhadores da saúde. Este trabalho pretendeu evidenciar a colonização das mãos por bactérias e a influência da lavagem de mãos e o exame físico dos pacientes. 100 profisionais de saúde foram divididos, ao acaso em dois grupos: A - sem lavagem de mãos antes do exame físico ou manejo dos pacientes (PPE); B - com lavagem prévia das mãos antes do PPE. Foram obtidas amostras de impressões digitais em agar Columbia antes e depois do PPE. As colônias foram contadas e identificadas por técnicas convencionais e antibiogramas de acordo com NCCLS. Antes do PPE os participantes do grupo A apresentaram elevado número de bactérias em relação ao grupo B (73.9 vs. 20.7; p < 0.001); 44 dos 50 participantes eram portadores potenciais de bactérias patogênicas. Nenhum participante do grupo B era portador de bactéria potencialmente patogênica antes do PPE. Este grupo mostrou um aumento no número de bactérias depois do PPE (20.7 UFC antes vs. 115.9 UFC depois; p < 0.001). 16 participantes do grupo B foram contaminados, depois do PPE, com patógenos potenciais tais como S. aureus (50% dos quais eram resistentes à meticilina), Escherichia coli, Pseudomonas aeruginosa e Enterococcus faecalis, metade dos quais, multiresistentes. Podemos concluir sobre a importância destes resultados para implementar programas educacionais e para prover os trabalhadores da saúde com facilidades para o adequado cumprimento desta prática