Fitness costs of sublethal exposure to Bacillus thuringiensis in Helicoverpa armigera: a carryover study on offspring

Bacillus thuringiensis (Bt) is an efficient entomopathogen used for pest control. While Bt pathogenesis has been thoroughly studied, less is known about the biological effects of sublethal Bt exposure. To address this knowledge gap, we document sublethal effects of Bacillus thuringiensis var. kurstaki (Btk) on the biology and development of Helicoverpa armigera (Hübner) under laboratory conditions. The results obtained revealed that duration of the different life stages in treated neonates of H. armigera was significantly affected by sublethal treatments. Furthermore, fecundity was also negatively affected in female moths developed from Btk‐treated neonates, with the rate of egg hatchability reaching zero in the LC₂₅. We also present data supporting that the effect of sublethal Btk concentrations could carry over to the next generation. Sublethal Btk concentrations reduced the net reproduction rate (R₀), and there were also significant differences among the values of this parameter at all treatments tested when compared with controls. The intrinsic and finite rates of increase (r_m and λ, respectively) were significantly lower in insects treated with sublethal Btk concentrations compared with control insects. Consequent with the reduce rate of development observed for H. armigera treated with Btk, the mean generation time (T) and doubling time (DT) were significantly higher in insects exposed to any Btk concentration tested compared with control. Our data demonstrate significant fitness costs resulting from sublethal Btk exposure in H. armigera. These observations underline the importance of considering the role of sublethal effects when attempting to evaluate the impact of Bt treatment on an insect pest population and its progeny.     

The thermodynamic basis for the use of lipophilic efficiency (LipE) in enthalpic optimizations

Approaches to improve the efficiency of molecular optimizations have received great attention and numerous efficiency metrics have been introduced to assist in this effort. Optimization of properties is equally important to optimization of potency and therefore these metrics contain potency versus property calculations. Widespread use of a metric does not guarantee its accuracy and a further understanding of which, if any, metric increases the probability of success was sought. An analysis of LE, LELP and LipE based on theoretical and experimental data was performed demonstrating that LipE most strongly correlates with compound quality as defined by enthalpy-driven binding. The basis for the prioritization of LipE over other metrics in enthalpic optimizations is described.     

Interannual variation in effective number of breeders and estimation of effective population size in long‐lived iteroparous lake sturgeon (Acipenser fulvescens)

Quantifying interannual variation in effective adult breeding number (N_b) and relationships between N_b, effective population size (N_e), adult census size (N) and population demographic characteristics are important to predict genetic changes in populations of conservation concern. Such relationships are rarely available for long‐lived iteroparous species like lake sturgeon (Acipenser fulvescens). We estimated annual N_b and generational N_e using genotypes from 12 microsatellite loci for lake sturgeon adults (n = 796) captured during ten spawning seasons and offspring (n = 3925) collected during larval dispersal in a closed population over 8 years. Inbreeding and variance N_b estimated using mean and variance in individual reproductive success derived from genetically identified parentage and using linkage disequilibrium (LD) were similar within and among years (interannual range of N_b across estimators: 41–205). Variance in reproductive success and unequal sex ratios reduced N_b relative to N on average 36.8% and 16.3%, respectively. Interannual variation in N_b/N ratios (0.27–0.86) resulted from stable N and low standardized variance in reproductive success due to high proportions of adults breeding and the species' polygamous mating system, despite a 40‐fold difference in annual larval production across years (437–16 417). Results indicated environmental conditions and features of the species' reproductive ecology interact to affect demographic parameters and N_b/N. Estimates of N_e based on three single‐sample estimators, including LD, approximate Bayesian computation and sibship assignment, were similar to annual estimates of N_b. Findings have important implications concerning applications of genetic monitoring in conservation planning for lake sturgeon and other species with similar life histories and mating systems.     

商洛低山丘陵区农林复合生态系统中大豆与丹参的光合生理特性

农林复合系统作为一种传统而又新兴的土地利用和经营方式在改善商洛生态环境、增加该区农民收入、促进其生态和经济协调发展等方面发挥着非常重要的作用.为了研究林下作物的生理生态特性,对研究区农林复合系统中不同处理大豆、丹参的光合、叶绿素荧光参数进行了系统观测.结果表明,从单作到距核桃1m处,距核桃树越近,遮光愈多.各处理大豆的光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)表现出与光合有效辐射(PAR)基本一致的日变化趋势.不同处理丹参光合速率日变化趋势各不相同,且出现“午休”现象.与单作相比,各处理大豆、丹参的光合速率、气孔导度和蒸腾速率均有不同程度的降低.随着遮荫程度的提高,大豆、丹参叶绿素含量和表观量子效率(Φ)升高,光饱和点(LSP)和光补偿点(LCP)降低.二者叶绿素荧光参数最大光能转换效率(Fv/Fm)、PSⅡ电子传递量子效率(ΦPsⅡ)以及光化学猝灭系数(qP)均有不同程度的升高,而非光化学猝灭系数(qNP)却逐渐降低.说明大豆、丹参能适应弱光环境,在较低的光照条件下正常生长.     

肝硬化患者凝血4项指标与血小板参数检测的临床价值

目的:探讨肝硬化患者的凝血功能与血小板参数联合监测的临床意义.方法:对88例肝硬化患者的凝血酶时间(PT)、活化部分凝血酶时间(APTT)、纤维蛋白(FIB)、凝血酶时间(TT)等4项凝血指标和血小板计数(PLT)、平均血小板体积(MPV)、血小板压积(PCT)、血小板分布宽度(PDW)等血小板参数进行测定,并与80例正常人进行对照.结果:与对照组相比,患者组 PT、TT、APTT 显著延长(P<0.01),差别有极显著性意义;FIB、PLT、PCT 明显下降(P<0.01),差别有极显著性意义;MPV、PD 高对照组(P<0.05),差别有显著性意义.随着肝硬化患者 Child-Pugh 评分的升高,PLT、PCT 明显下降,MPV、PDW 明显上升;Child-A、Child-B、Child-C 组间 PLT、PCT、MPV、PDW 相互比较,差异均具有显著意义(P<0.05).结论:凝血4项指标与血小板参数指标的联合监测,对临床判定肝硬化患者的肝功能损害程度和有无出血倾向有重要价值.     

Serum markers in pre-eclampsia

Preeclampsia occurs approximately in 10% of pregnancies and remains a leading cause of maternal and neonatal mortality and morbidity worldwide, particularly in developing countries. The condition is usually diagnosed in late pregnancy by the presence of hypertension with proteinuria and/ or edema. Prevention of any disease process requires knowledge of its etiology and pathogenesis, as well as the availability of methods for prediction of those at high risk for this disorder. Numerous clinical, biophysical, and biochemical tests have been proposed for prediction or early detection of preeclampsia. This review will explore the current tests available in the evaluation of hypertensive complications of pregnancy.     

Diverse role of conformational dynamics in carboxypeptidase A-driven peptide and ester hydrolyses: disclosing the "perfect induced fit" and "protein local unfolding" pathways by altering protein stability

Catalytic mechanisms of carboxypeptidase A (CPA) are well known for their diversity and the relative inaccessibility for a decisive comprehension. Recent encouraging attempts through modern computational techniques promoted new challenges for the complementary experimental endeavors. In this work, we have applied the stopped-flow technique and the method of reaction progress curve fitting to extract kinetic parameters for the CPA-catalyzed hydrolyses of smaller (typical) peptide and ester substrates, known for their strong activating/inhibiting impact, thus to which the traditional method of "initial rates" is not applicable. Our approach that innately implies the overall constancy of the affecter (substrate plus "active" product) concentration, made it possible to rigorously determine the physically meaningful "effective" values for the catalytic and Michaelis constants under diverse experimental conditions including variable temperature and urea or trimethylamine N-oxide concentrations. Analysis of the obtained results allowed for: (i) the further substantiation of diverse mechanistic patterns for archetypal specific peptide and ester substrates, (ii) testing and disclosure of intrinsic links between the stabilizing/destabilizing and activating/inhibiting effects for the important model enzyme, CPA, and (iii) tentative explanation of a distinct activating/inhibiting impact of these substrates through the strong specific interaction of their benzyl (Bz) moiety with the substrate binding S(3) subsite of CPA. We have demonstrated that stabilization of CPA either through the interaction with an extra Bz moiety (belonging to another substrate or to the product) leads to the increase of its catalytic power with respect to the specific peptide substrate and to its decrease with respect to the counterpart ester substrate. We conjecture that the catalytic mechanisms operating in these two cases include: (a) the "promoted water" mechanism for the peptide substrate that, seemingly, provides the almost "perfect induced fit" (low-barrier conformational adaptation), and (b) presumably, the "anhydride intermediate" mechanism for the ester substrate that, anyway, requires substantial conformational rearrangement (in fact, "partial or local unfolding") of the protein environment in the course of the rate-determining step.     

Nucleic-acid structural deformability deduced from anisotropic displacement parameters

The growing numbers of very well resolved nucleic-acid crystal structures with anisotropic displacement parameters provide an unprecedented opportunity to learn about the natural motions of DNA and RNA. Here we report a new Monte-Carlo approach that takes direct account of this information to extract the distortions of covalent structure, base pairing, and dinucleotide geometry intrinsic to regularly organized double-helical molecules. We present new methods to test the validity of the anisotropic parameters and examine the apparent deformability of a variety of structures, including several A, B, and Z DNA duplexes, an AB helical intermediate, an RNA, a ligand-DNA complex, and an enzyme-bound DNA. The rigid-body parameters characterizing the positions of the bases in the structures mirror the mean parameters found when atomic motion is taken into account. The base-pair fluctuations intrinsic to a single structure, however, differ from those extracted from collections of nucleic-acid structures, although selected base-pair steps undergo conformational excursions along routes suggested by the ensembles. The computations reveal surprising new molecular insights, such as the stiffening of DNA and concomitant separation of motions of contacted nucleotides on opposite strands by the binding of Escherichia coli endonuclease VIII, which suggest how the protein may direct enzymatic action.     

Effects of precipitation on photosynthesis and water potential in Andropogon gerardii and Schizachyrium scoparium in a southern mixed grass prairie

In grassland ecosystems, spatial and temporal variability in precipitation is a key driver of species distributions and population dynamics. We experimentally manipulated precipitation to understand the physiological basis for differences in responses of species to water availability in a southern mixed grass prairie. We focused on the performance of two dominant C₄ grasses, Andropogon gerardii Vitman and Schizachyrium scoparium (Michx.) Nash, in treatments that received ambient rainfall, half of ambient rainfall (“drought” treatment), or approximately double ambient rainfall (“irrigated” treatment). Water potentials of S. scoparium were lower than A. gerardii, suggesting superior ability to adjust to water deficit in S. scoparium. Additionally, drought reduced photosynthesis to a greater extent in A. gerardii compared to S. scoparium. Leaf-level photosynthesis rates were similar in ambient and irrigated treatments, but were significantly lower in the drought treatment. Although stomatal conductance was reduced by drought, this was not limiting for photosynthesis. Leaf δ¹³C values were decreased by drought, caused by an increase in C_i/C_a. Chlorophyll fluorescence measures indicated light-harvesting rates were highest in irrigated treatments, and were lower in ambient and drought treatments. Moreover, drought resulted in a greater proportion of absorbed photon energy being lost via thermal pathways. Reductions in photosynthesis came as a result of non-stomatal limitations in the C₄ cycle. Our results provide mechanistic support for the hypothesis that S. scoparium is more drought tolerant than A. gerardii.