Cl- Fluxes and Cl- Content of Dunaliella acidophila--An Alga with a Positive Membrane Potential

The Cl^– fluxes across the plasma membrane and the Cl^–content of the acid–resistant alga Dunaliella acidophila(optimal growthat pH 1.0, positive membrane potential) werestudied in the presence of 0.01–300 mM Cl^–. Up to40 mM Cl^– in the medium, theinternal Cl^– concentrationis higher than that predicted by the electrochemical equilibrium,whereas at higher external Cl^– concentrations internalCl^– levels are lower than expected for the electrochemicalequilibrium. Growth in the absence of Cl^– is significantlylower than in the standard growth medium (2.2 mM Cl^–)and this reduction cannot be overcome by the addition ofothermonovalent anions such as Br^– or NO^–₃ The latterimplies a specific Cl^– requirement in addition to therole of Cl^– as apermeant anion during ion translocations.Growth and photosynthesis tolerate an excess of Cl^– upto 300 mM (without stepwiseadaptation to increasing salinity).The uptake of Cl^– (measured by tracer techniques) exhibitsMichaelis–Menten kinetics (K_M = 0.75 mM Cl^–) andis stimulated by light and high H⁺ concentrations. Internalacidification by acetic acid causes an inhibition of Cl^–uptake. The uptake of Cl^– is inhibited by the monovalentanions Br^–, I^–, and NO^–₃ with K¹, values notvery much different from the K_M. value for Cl^–. The aniontransport inhibitors SITS and DIDS do not affect photosynthesis,but strongly suppressthe uptake of Cl^–. The Cl^–channel blockers A–9–C and NPPB cause inhibitionsof Cl^– uptake as well as of photosynthesis andthe ATPpool. FCCP strongly depresses the internal ATP–pool withouta marked effect on Cl^– uptake. Cl^– efflux was inhibitedbyDIDS and SITS, but stimulated or inhibited by FCCP, dependingon the external Cl^– concentration. Results are in agreementwiththe hypothesis that Cl^– uptake into D. acidophila is dueto catalysed diffusion and is primarily independent of the hydrolysisofATP. Cl^– efflux is assumed to be coupled to an activepump. Data suggest tight co–operativity between the systemsresponsiblefor Cl^– uptake and Cl^– efflux, with thecytoplasmic pH and the membrane potential being important mediators. Key words: Acid resistance, chloride carrier, chloride channels, Dunaliella acidophila, membrane potential, plasma membrane     

An assessment of the breeding range,colony sizes and population of the Westland petrel (Procellaria westlandica)

Abstract

The Westland petrel (Procellaria westlandica) is an endemic New Zealand species and one of the very few burrowing seabird species still breeding on mainland New Zealand. It nests only on a series of coastal ridgelines near to Punakaiki on the West Coast of the South Island. Between 2002 and 2005, surveys were undertaken at 28 of the 29 known colonies. The area occupied by the colonies was 73 ha; most colonies had fewer than 50 burrows, but six colonies had 201–500 burrows and four colonies had more than 1000 burrows. We find that the current breeding range of Westland petrel and the location of individual colonies are similar to those reported in both the 1950s and 1970s. Based on total burrow counts at 28 colonies and burrow occupancy rates determined by annual monitoring, the annual breeding population is estimated to be between 2954 and 5137 breeding pairs.     

Predictors of mortality of patients with acute respiratory failure secondary to chronic obstructive pulmonary disease admitted to an intensive care unit: A one year study

Background

Patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) commonly require hospitalization and admission to intensive care unit (ICU). It is useful to identify patients at the time of admission who are likely to have poor outcome. This study was carried out to define the predictors of mortality in patients with acute exacerbation of COPD and to device a scoring system using the baseline physiological variables for prognosticating these patients.

Methods

Eighty-two patients with acute respiratory failure secondary to COPD admitted to medical ICU over a one-year period were included. Clinical and demographic profile at the time of admission to ICU including APACHE II score and Glasgow coma scale were recorded at the time of admission to ICU. In addition, acid base disorders, renal functions, liver functions and serum albumin, were recorded at the time of presentation. Primary outcome measure was hospital mortality.

Results

Invasive ventilation was required in 69 patients (84.1%). Fifty-two patients survived to hospital discharge (63.4%). APACHE II score at the time of admission to ICU {odds ratio (95 % CI): 1.32 (1.138–1.532); p < 0.001} and serum albumin (done within 24 hours of admission) {odds ratio (95 % CI): 0.114 (0.03-0.432); p = 0.001}. An equation, constructed using the adjusted odds ratio for the two parameters, had an area under the ROC curve of 91.3%. For the choice of cut-off, sensitivity, specificity, positive and negative predictive value for predicting outcome was 90%, 86.5%, 79.4% and 93.7%.

Conclusion

APACHE II score at admission and SA levels with in 24 hrs after admission are independent predictors of mortality for patients with COPD admitted to ICU. The equation derived from these two parameters is useful for predicting outcome of these patients.     

The contribution of genetic variation and infection to the pathogenesis of ANCA-associated systemic vasculitis

The aetiology of anti-neutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis has not been well defined. Here we review two factors which may play a role in the pathogenesis of the disease: genetics and infection. In particular, we discuss the role of autoantibodies to LAMP-2, which may arise following infection with Gram-negative bacteria, and may contribute to the development of ANCA-associated systemic vasculitis in genetically susceptible individuals.