Association of XRCC1 Arg399Gln polymorphism with bladder cancer susceptibility: A meta-analysis

Genetic variations in DNA repair genes are thought to modify DNA repair capacity and may to be related to cancer susceptibility. However, epidemiological study results have been inconsistent. In this meta-analysis, we assessed 24 case–control studies of association between the X-ray repair cross complementing group 1 (XRCC1) Arg399Gln polymorphism and bladder cancer susceptibility in the general population and in Asian and non-Asian subgroups. A moderately significant association with bladder cancer risk was found for AG vs GG (OR = 1.110, 95% CI = 1.018–1.210). No significant associations with bladder cancer risk were found for AA vs GG (OR = 0.942, 95% CI = 0.823–1.077), the dominant model AA/AG vs GG (OR = 1.075, 95% CI = 0.990–1.167) and the recessive model AA vs AG/GG(OR = 0.890, 95% CI = 0.788–1.005). In subgroup analysis, a moderately significant association was also found for AG vs GG (OR = 1.091, 95% CI = 1.008–1.180) in non-Asian subgroup. The analysis suggests that the XRCC1 Arg399Gln polymorphism might be a moderate risk factor for bladder cancer, especially in non-Asian population.     

Association of genetic polymorphisms in ADH and ALDH2 with risk of coronary artery disease and myocardial infarction: A meta-analysis

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are the major enzymes responsible for alcohol metabolism in humans. Emerging evidences have shown that functional polymorphisms in ADH and ALDH genes might play a critical role in increasing coronary artery disease (CAD) and myocardial infarction (MI) risks; however, individually published studies showed inconclusive results. The aim of this meta-analysis is to evaluate the associations between the genetic polymorphisms of ADH and ALDH genes with susceptibility to CAD and MI. A literature search was conducted on PubMed, Embase, Web of Science and Chinese BioMedical databases from inception through December 1st, 2012. Crude relative risks (RRs) with 95% confidence intervals (CIs) were calculated. Twelve case–control studies were included with a total of 9616 subjects, including 2053 CAD patients, 1436 MI patients, and 6127 healthy controls. Meta-analysis showed that mutant genotypes (GA + AA) of the rs671 polymorphism in the ALDH2 gene were associated with increased risk of both CAD and MI (CAD: RR = 1.20, 95%CI: 1.03–1.40, P = 0.021; MI: RR = 1.32, 95%CI: 1.11–1.57, P = 0.002). However, there were no significant associations of ADH genetic polymorphisms to CAD and MI risks (CAD: RR = 0.92, 95%CI: 0.73–1.15, P = 0.445; MI: RR = 0.93, 95%CI: 0.84–1.03, P = 0.148). In conclusion, this meta-analysis provides strong evidence that ALDH2 rs671 polymorphism may be associated with increased risks of CAD and MI. However, further studies are still needed to accurately determine whether ADH genetic polymorphisms are associated with susceptibility to CAD and MI.     

Warming chambers stimulate early season growth of an arctic sedge: results of a minirhizotron field study

We examined the effects of passive open-top warming chambers on Eriophorum vaginatum production near Toolik Lake, Alaska, USA. During the 2002 growing season, chamber warming was consistent with the magnitude and seasonality observed in recent decades throughout northwestern North America. Leaf-growth rates were higher in late May and early June; maximum growth rates in each leaf cohort occurred earlier and peak biomass was observed 20 days earlier within the chambers. Consequently, plants within the chambers maintained more live leaf biomass during the period of highest photosynthetically active radiation. Annual leaf production within the chambers (21±2 mg tiller) was not significantly different than under ambient conditions (17±2 mg tiller) (P=0.2256) despite higher early-season growth rates. Root growth began earlier; growth rates were higher in late May and early June, and maximum growth rates occurred earlier within the chambers. Therefore, plants within the chambers maintained greater root biomass during what earlier studies have identified as a period of relatively high nutrient availability. Annual root production within the chambers (191±42 g m^–2) was not significantly different than under ambient conditions (119±48 g m^–2) (P=0.1979), although there was a trend toward higher production within the chambers. The tendency toward higher root production within the chambers is consistent with previous laboratory experiments and with the predictions of biomass allocation theory.     

Relations between biochemical thermodynamics and biochemical kinetics

The parameters in steady-state or rapid-equilibrium rate equations for enzyme-catalyzed reactions depend on the temperature, pH, and ionic strength, and may depend on the concentrations of specific species in the buffer. When the complete rate equation (i.e. the equation with parameters for the reverse reaction as well as the forward reaction) is determined, there are one or more Haldane relations between some of the kinetic parameters and the apparent equilibrium constant for the reaction that is catalyzed. When the apparent equilibrium constant can be calculated from the kinetic parameters, the equilibrium composition can be calculated. This is remarkable because the kinetic parameters all depend on the properties of the enzymatic site, but the apparent equilibrium constant and the equilibrium composition do not. The effects of ionic strength and pH on the unoccupied enzymatic site and the occupied enzymatic site have to cancel in the Haldane relation or in the calculation of the apparent equilibrium constant using the rate constants for the steps in the mechanism. Several simple enzymatic mechanisms and their complete rate equations are discussed.     

Leveraging plant hydraulics to yield predictive and dynamic plant leaf allocation in vegetation models with climate change

Plant functional traits provide a link in process‐based vegetation models between plant‐level physiology and ecosystem‐level responses. Recent advances in physiological understanding and computational efficiency have allowed for the incorporation of plant hydraulic processes in large‐scale vegetation models. However, a more mechanistic representation of water limitation that determines ecosystem responses to plant water stress necessitates a re‐evaluation of trait‐based constraints for plant carbon allocation, particularly allocation to leaf area. In this review, we examine model representations of plant allocation to leaves, which is often empirically set by plant functional type‐specific allometric relationships. We analyze the evolution of the representation of leaf allocation in models of different scales and complexities. We show the impacts of leaf allocation strategy on plant carbon uptake in the context of recent advancements in modeling hydraulic processes. Finally, we posit that deriving allometry from first principles using mechanistic hydraulic processes is possible and should become standard practice, rather than using prescribed allometries. The representation of allocation as an emergent property of scarce resource constraints is likely to be critical to representing how global change processes impact future ecosystem dynamics and carbon fluxes and may reduce the number of poorly constrained parameters in vegetation models.     

Synthesis and characterization of carboxymethyl-polyaminate chitosan and its adsorption behavior toward a reactive dye

Carboxymethyl-polyaminate chitosan (DETA-CMCHS), a novel kind of amphoteric chitosan derivative, was prepared and characterized by elemental analysis, and by IR and ¹H NMR spectroscopy. The adsorption behavior of Reactive Blue (RB2) on DETA-CMCHS was also studied. Results showed that the maximum value of adsorption capacity was 1185.71 mg/g at pH 3. The adsorption kinetic behavior was fitted with a second-order reaction rate equation. The adsorption was an exothermic, irreversible and entropy-reduced process according to thermodynamic parameters, such as standard Gibbs free-energy change, enthalpy change, and entropy change, all of which were calculated from adsorption equilibrium data.     

Development of a boron buffered solution culture system for controlled studies of plant boron nutrition

Chelated-buffered nutrient solutions are used for studies on micronutrient metals but so far no equivalent system exists for boron nutrition studies: the present investigation was initiated with that intention. From a literature review, it was noted that a range of substances form chelates with boron including polyhydric alcohols, sugars and phenolic compounds. However, none apart from hydrofluoric acid formed chelates with formation constants comparable to those of micronutrient metal chelates like diethylenetriaminepentaacetic acid (DTPA). Moreover, most chelating substances had deleterious side effects which reduced their possible use in water culture: many of the compounds are substrates for bacterial growth, some are harmful to handle, and others are toxic to plants or humans. Borosilicate glass; was tested in a laboratory experiment but found to release boron too slowly into solution to maintain constant boron concentration in solution even when very finely ground. Current investigations centre around the use of a boron-specific resin, which strongly complexes H₃BO₃ on its N-methyl glucamine functional groups. The boron sorption capacity of the resin varied from 2.2 to 5.0 mg B g^-1 resin. Boron saturated resin maintained an equilibrium solution boron concentration of 46 t M when added at the rate of 2 g of resin to 1 L of boron free triple deionised water. Plants grown in complete nutrient solution with boron saturated resin added at 1 g per litre of nutrient solution grew as well as plants grown in conventional nutrient solution containing 9.2 t M boron and their shoots contained adequate boron concentrations for growth. There was no evidence that the resin had effects on plant growth other than in releasing and equilibrating boron concentration in the nutrient solution.