Formate increases the F0F1-ATPase activity in Escherichia coli growing on glucose under anaerobic conditions at slightly alkaline pH

Escherichia coli growing on glucose under anaerobic conditions at slightly alkaline pH carries out a mixed-acid fermentation resulting in the production of formate among the other products that can be excreted or further oxidized to H(2) and CO(2). H(2) production is largely dependent on formate dehydrogenase H and hydrogenases 3 and 4 constituting two formate hydrogen lyases, and on the F(0)F(1)-ATPase. In this study, it has been shown that formate markedly increased ATPase activity in membrane vesicles. This activity was significantly (1.8-fold) stimulated by 100mM K(+) and inhibited by N,N(')-dicyclohexylcarbodiimide and sodium azide. The increase in ATPase activity was absent in atp, trkA, and hyf but not in hyc mutants. ATPase activity was also markedly increased by formate when bacteria were fermenting glucose with external formate (30mM) in the growth medium. However this activity was not stimulated by K(+) and absent in atp and hyc but not in hyf mutants. The effects of formate on ATPase activity disappeared when cells were performing anaerobic (nitrate/nitrite) or aerobic respiration. These results suggest that the F(0)F(1)-ATPase activity is dependent on K(+) uptake TrkA system and hydrogenase 4, and on hydrogenase 3 when cells are fermenting glucose in the absence and presence of external formate, respectively.     

Centriolar SAS-5 is required for centrosome duplication in C. elegans

Centrosomes, the major microtubule-organizing centres (MTOCs) of animal cells, are comprised of a pair of centrioles surrounded by pericentriolar material (PCM). Early in the cell cycle, there is a single centrosome, which duplicates during S-phase to direct bipolar spindle assembly during mitosis. Although crucial for proper cell division, the mechanisms that govern centrosome duplication are not fully understood. Here, we identify the Caenorhabditis elegans gene sas-5 as essential for daughter-centriole formation. SAS-5 is a coiled-coil protein that localizes primarily to centrioles. Fluorescence recovery after photobleaching (FRAP) experiments with green fluorescent protein (GFP) fused to SAS-5 (GFP-SAS-5) demonstrated that the protein shuttles between centrioles and the cytoplasm throughout the cell cycle. Analysis of mutant alleles revealed that the presence of SAS-5 at centrioles is crucial for daughter-centriole formation and that ZYG-1, a kinase that is also essential for this process, controls the distribution of SAS-5 to centrioles. Furthermore, partial RNA-interference (RNAi)-mediated inactivation experiments suggest that both sas-5 and zyg-1 are dose-dependent regulators of centrosome duplication.     

Proton translocation coupled to formate oxidation in anaerobically grown fermenting Escherichia coli

Proton translocation, coupled to formate oxidation and hydrogen evolution, was studied in anaerobically grown fermenting Escherichia coli JW136 carrying hydrogenase 1 (hya) and hydrogenase 2 (hyb) double deletions. Rapid acidification of the medium by EDTA-treated anaerobic suspension of the whole cells or its alkalization by inverted membranes was observed in response to application of formate. The formate-dependent proton translocation and 2H(+)-K(+) exchange coupled to H(2) evolution were sensitive to the uncoupler, carbonylcyanide-m-chlorophenylhydrazone, and to copper ions, inhibitors of hydrogenases. No pH changes were observed in a suspension of formate-pulsed aerobically grown ("respiring") cells. The apparent H(+)/formate ratio of 1.3 was obtained in cells oxidizing formate. The 2H(+)-K(+) exchange of the ATP synthase inhibitor N,N'-dicyclohexylcarbodiimide-sensitive ion fluxes does take place in JW136 cell suspension. Hydrogen formation from formate by cell suspensions of E. coli JW136 resulted in the formation of a membrane potential (Deltapsi) across the cytoplasmic membrane of -130 mV (inside negative). This was abolished in the presence of copper ions, although they had little effect on the value of Deltapsi generated by E. coli under respiration. We conclude that the hydrogen production by hydrogenase 3 is coupled to formate-dependent proton pumping that regulates 2H(+)-K(+) exchange in fermenting bacteria.     

Plant virus RNAs. Coordinated recruitment of conserved host functions by (+) ssRNA viruses during early infection events

Positive-sense single-stranded RNA viruses have developed strategies to exploit cellular resources at the expense of host mRNAs. The genomes of these viruses display a variety of structures at their 5' and 3' ends that differentiate them from cellular mRNAs. Despite this structural diversity, viral RNAs are still circularized by juxtaposition of their 5' and 3' ends, similar to the process used by cellular mRNAs. Also reminiscent of the mechanisms used by host mRNAs, translation of viral RNAs involves the recruitment of translation initiation factors. However, the roles played by these factors likely differ from those played by cellular mRNAs. In keeping with the general parsimony typical of RNA viruses, these host factors also participate in viral RNA replication. However, the dual use of host factors requires that viral RNA template utilization be regulated to avoid conflict between replication and translation. The molecular composition of the large ribonucleoprotein complexes that form the viral RNA replication and translation machineries likely evolves over the course of infection to allow for switching template use from translation to replication.     

Accuracy of patient-reported height loss and risk factors for height loss among postmenopausal women

Background

Since loss of height may indicate vertebral fracture, the accuracy of the information on height is relevant for clinical practice. We undertook this study to compare reported and measured loss of height among post-menopausal women in a primary care setting. We also analyzed the determinants of this height loss.

Methods

In an observational study conducted between December 2007 and May 2008, we asked 1779 randomly selected general practitioners to recruit the first five female patients who were more than 60 years of age, regardless of the reason for the consultation. Using a questionnaire, physicians collected data on demographic and clinical variables, history of osteoporosis and current anti-osteoporotic treatment. We used three assessments of height: tallest height in early adulthood recalled by the patient, estimated current height reported by the patient at the visit and current measured height. We defined loss of height as the difference between the patient’s tallest recalled height and her current measured height.

Results

A total of 8610 patients were included in the analysis; the mean age was 70.9 (standard deviation [SD] 7.2) years. The mean loss of height was 4.5 cm. The mean current reported height was 2.1 (SD 2.5) cm lower than the tallest recalled height and 2.4 (SD 2.6) cm lower than the measured current height. The best predictors of a loss of height of 3 cm or more were age (odds ratio [OR] 1.09, 95% confidence interval [CI] 1.08–1.10), previous vertebral fracture (OR 1.49, 95% CI 1.16–1.91), previous nonvertebral fracture (OR 1.26, 95% CI 1.06–1.51), thoracic kyphosis (OR 2.07, 95% CI 1.69–2.55), scoliosis (OR 1.35, 95% CI 1.12–1.63), back pain (OR 1.22, 95% CI 1.07–1.39) and osteoporosis (OR 1.39, 95% CI 1.20–1.60).

Interpretation

Our study showed that the patients’ estimated current height was not correct, with a mean difference of −2.5 cm from the current measured height. The mean height loss was 4.5 cm. Previous vertebral fracture and thoracic kyphosis were strong determinants of the height loss.Loss of height is common with advancing age.^1,2 Causes include changes in curvature of the spine, narrowing of intervertebral discs and vertebral fractures. Height loss is associated with back pain and thoracic hyperkyphosis.^3,4 Two-thirds of adults have back pain at any time. Controversies exist about the need for radiographs of the spine: Does the benefit of detecting treatable disorders of the spine such as vertebral fracture outweigh the harm of unnecessary radiographs? Loss of height is usually recorded as one of the clinical signs to help identify postmenopausal women with vertebral fractures.⁵ The use of this parameter to decide whether radiography is needed depends on the threshold for height loss associated with a strong risk of vertebral fracture. The thresholds useful in clinical practice to detect prevalent vertebral fracture range from 3 cm to 6 cm,^6–9 with the risk of prevalent fracture increasing with the magnitude of the height loss. Thus, the accuracy of the information on height is relevant for clinical practice.We conducted this study to compare reported and measured loss of height in a large population of women more than 60 years old in a primary care setting and to analyze the determinants of this height loss.