Genomic diversity among Vibrio cholerae O139 strains isolated in Bangladesh and India between 1992 and 1998

In order to assess the extent of genomic diversity among Vibrio cholerae O139 strains, restriction fragment length polymorphisms in two genetic loci, rrn and ctx, were studied. Analysis of 144 strains isolated from different regions of Bangladesh and India between 1992 and 1998 revealed the presence of at least six distinct ribotypes (B-I through B-VI) of which three were new ribotypes, and one of these was represented by a nontoxigenic O139 strain. Strains of ribotypes B-I through B-V shared 11 different CTX genotypes (A through K). Antimicrobial resistance patterns of the strains varied independently of their ribotypes and CTX genotypes. Results of this study suggest that V. cholerae O139 is undergoing rapid genetic changes leading to the origination of new variants, and temporal changes in antimicrobial resistance patterns may be contributing to the selection of different variants.     

Effects of pH and corn steep liquor variability on mannitol production by Lactobacillus intermedius NRRL B-3693

Lactobacillus intermedius NRRL B-3693 produced mannitol, lactic acid, and acetic acid when grown on fructose at 37°C. The optimal pH for mannitol production from fructose by the heterofermentative lactic acid bacterium (LAB) in pH-controlled fermentation was at pH 5.0. It produced 160.7 ± 1.1 g mannitol in 40 h with a volumetric productivity of 4.0 g l⁻¹ h⁻¹ in a simplified medium containing 250 g fructose, 50 g corn steep liquor (CSL), and 33 mg MnSO₄ per liter. However, the mannitol production by the LAB was severely affected by the variability of CSL. The supplementation of CSL with soy peptone (5 g/l), tryptophan (50 mg/l), tryptophan (50 mg/l) plus tyrosine (50 mg/l), or commercial protease preparation (2 ml/100 g of CSL) enhanced the performance of the inferior CSL and thus helped to overcome the nutrient limitations.     

The correlation of meteorological parameters with grasshopper populations in Darjeeling

Population dynamics of five different species of grasshopper were analyzed for the first time in Darjeeling (Lebong and Happy Valley) of the eastern Himalayan region of India. The study is based on the relationship between monthly samples collected using sweep nets for three years (March, 2005 to February, 2008) in relation to meteorological parameters (monthly average rainfall, monthly mean maximum and minimum temperatures). The population for each of the five species of grasshopper is plotted against the Aridity Ratio (A.R.). For all species, the population increases at lower A.R. values and then decreases exponentially at higher A.R. values. The exponentially decreasing part of the population is modeled using a simple formula. The monthly population of A. crenulata nymphs and adults in Lebong has also been modeled by iterative equations using A.R. and results compared satisfactorily with the sample data. These works show the possibility of forecasting grasshopper populations using a simple model and thereby easing the regulation process.     

Comparative analysis of some biochemical responses of three indica rice varieties during polyethylene glycol-mediated water stress exhibits distinct varietal differences

Extensive investigation into plant response and adaptation to diverse osmotic stresses like high salt/dehydration/low temperature, involving a broad spectrum of cellular physiological and biochemical changes, is essential to unravel intrinsic mechanism to mitigate against such stresses. In our previous communications, we conducted biochemical analyses of indica rice varieties, subjected to exogenous salt/abscisic acid-mediated oxidative stress. The aim of this study was to compare differential biochemical responses of the salt-sensitive (IR-29), salt-tolerant (Pokkali) and aromatic (Pusa Basmati or PB) rice varieties during polyethylene glycol (PEG)-induced dehydration stress. The greater susceptibility of IR-29 and PB, to water scarcity, was reflected by the higher toxic Na⁺ and putrescine accumulation, considerable decrease in (reduced/oxidized) glutathione, maximal increment in protease activity and greater downregulation of nitrate reductase activity. On the other hand, Pokkali appeared to suffer lesser damages as evidenced from much lower endogenous Na⁺ but higher K⁺, Ca²⁺ and Mg²⁺ accumulation, registering the highest levels of osmolytes like glycinebetaine and higher polyamines (spermidine and spermine) accounting to improved relative water content, higher (reduced/oxidized) glutathione, maximal induction of the enzyme phenylalanine ammonia-lyase and practically unhindered nitrate reductase activity, following PEG treatment. The highest induction of sugars and proline in IR-29 and PB probably played the osmoprotective/antioxidative functions, enabling to a certain extent to heighten their lipoxygenase inhibition or H₂O₂ scavenging potential, more than Pokkali, to ward off oxidative damages and sustain survival under critical dehydrated situations. Thus, the salt-tolerant Pokkali also showed prominent dehydration-tolerance properties, whereas the aromatic rice PB, almost identical in their biochemical responses to IR-29, showed greater sensitivity to PEG-mediated water deficit.     

Time‐Dependent Predictive Accuracy in the Presence of Competing Risks

Summary Competing risks arise naturally in time‐to‐event studies. In this article, we propose time‐dependent accuracy measures for a marker when we have censored survival times and competing risks. Time‐dependent versions of sensitivity or true positive (TP) fraction naturally correspond to consideration of either cumulative (or prevalent) cases that accrue over a fixed time period, or alternatively to incident cases that are observed among event‐free subjects at any select time. Time‐dependent (dynamic) specificity (1–false positive (FP)) can be based on the marker distribution among event‐free subjects. We extend these definitions to incorporate cause of failure for competing risks outcomes. The proposed estimation for cause‐specific cumulative TP/dynamic FP is based on the nearest neighbor estimation of bivariate distribution function of the marker and the event time. On the other hand, incident TP/dynamic FP can be estimated using a possibly nonproportional hazards Cox model for the cause‐specific hazards and riskset reweighting of the marker distribution. The proposed methods extend the time‐dependent predictive accuracy measures of Heagerty, Lumley, and Pepe (2000, Biometrics 56, 337–344) and Heagerty and Zheng (2005, Biometrics 61, 92–105).     

Changing forest water yields in response to climate warming: results from long‐term experimental watershed sites across North America

Climate warming is projected to affect forest water yields but the effects are expected to vary. We investigated how forest type and age affect water yield resilience to climate warming. To answer this question, we examined the variability in historical water yields at long‐term experimental catchments across Canada and the United States over 5‐year cool and warm periods. Using the theoretical framework of the Budyko curve, we calculated the effects of climate warming on the annual partitioning of precipitation (P) into evapotranspiration (ET) and water yield. Deviation (d) was defined as a catchment's change in actual ET divided by P [AET/P; evaporative index (EI)] coincident with a shift from a cool to a warm period – a positive d indicates an upward shift in EI and smaller than expected water yields, and a negative d indicates a downward shift in EI and larger than expected water yields. Elasticity was defined as the ratio of interannual variation in potential ET divided by P (PET/P; dryness index) to interannual variation in the EI – high elasticity indicates low d despite large range in drying index (i.e., resilient water yields), low elasticity indicates high d despite small range in drying index (i.e., nonresilient water yields). Although the data needed to fully evaluate ecosystems based on these metrics are limited, we were able to identify some characteristics of response among forest types. Alpine sites showed the greatest sensitivity to climate warming with any warming leading to increased water yields. Conifer forests included catchments with lowest elasticity and stable to larger water yields. Deciduous forests included catchments with intermediate elasticity and stable to smaller water yields. Mixed coniferous/deciduous forests included catchments with highest elasticity and stable water yields. Forest type appeared to influence the resilience of catchment water yields to climate warming, with conifer and deciduous catchments more susceptible to climate warming than the more diverse mixed forest catchments.     

Use of periodic abstinence in Bangladesh: do they really understand?

Data from a nationally representative study in Bangladesh (BDHS 1996-97) were analysed to identify significant predictors of use of periodic abstinence, in comparison with other modern contraceptive methods. The study found that women in Bangladesh mostly use modern methods during their peak reproductive years, after which some of them switch to periodic abstinence. These women tend to be more from educated and from higher socioeconomic backgrounds and with at least one living son. Another set of data from the Matlab DSS was analysed and the results were in the same direction. Focus group discussions found that women were using the periodic abstinence method incorrectly, abstaining for more days than is necessary. For Bangladeshi contraceptive users to reach a higher degree of use-effectiveness for period abstinence, more IEC materials need to be developed.     

RSK phosphorylates SOS1 creating 14-3-3-docking sites and negatively regulating MAPK activation

The extent and duration of MAPK (mitogen-activated protein kinase) signalling govern a diversity of normal and aberrant cellular outcomes. Genetic and pharmacological disruption of the MAPK-activated kinase RSK (ribosomal S6 kinase) leads to elevated MAPK activity indicative of a RSK-dependent negative feedback loop. Using biochemical, pharmacological and quantitative MS approaches we show that RSK phosphorylates the Ras activator SOS1 (Son of Sevenless homologue 1) in cultured cells on two C-terminal residues, Ser1134 and Ser1161. Furthermore, we find that RSK-dependent SOS1 phosphorylation creates 14-3-3-binding sites. We show that mutating Ser1134 and Ser1161 disrupts 14-3-3 binding and modestly increases and extends MAPK activation. Together these data suggest that one mechanism whereby RSK negatively regulates MAPK activation is via site-specific SOS1 phosphorylation.