光合率作为藻类毒理测试指标

以氧电极法的光合率作为藻类毒性测试指标。整个测试过程准确,简便,快速。能够随时测定受试毒物对藻类光合作用的效应,与常规毒性试验比较,测定时间由96h缩短到2h。灵敏度约提高了一倍,Cu~(2 )对光合作用的半数效应浓度(EC_(50))是0.105mg/L,比Cu~(2 )对藻的急性毒性试验的EC_(50)(0.204mg/L)少了一倍。     

Inhibition of lipid peroxidation by S-nitrosoglutathione and copper

The antioxidant properties of S -nitrosoglutathione, a nitric oxide-derived product were studied in different experimental systems. By using the crocin bleaching test, S -nitrosoglutathione, in the presence of copper ions, shows an antioxidant capacity about six times higher than that of Trolox c and referable to the interception of peroxyl radicals by nitric oxide. Copper alone shows a modest inhibitory action, which is about seven times lower than that of Trolox c. S -nitrosoglutathione prevents lipid peroxidation induced by the well-known Fe 2+ /ascorbate system (IC 50 =450 μM) and the inhibitory effect is strongly reinforced by the presence of copper ions (IC 50 =6.5 μM). In addition, cumene hydroperoxide-induced lipid peroxidation is markedly decreased by S -nitrosoglutathione, provided that copper ions, maintained reduced by ascorbate, are present. Decomposition of S -nitrosoglutathione through metal catalysis and/or the presence of reducing agents and the consequent release of nitric oxide are of crucial importance for eliciting the antioxidant power. In this way, copper ions and/or reducing species with low antioxidant potency are able to promote the formation of an extremely strong antioxidant species such as nitric oxide.     

Exact two-sample inference with missing data

When comparing follow-up measurements from two independent populations, missing records may arise due to censoring by events whose occurrence is associated with baseline covariates. In these situations, inferences based only on the completely followed observations may be biased if the follow-up measurements and the covariates are correlated. This article describes exact inference for a class of modified U-statistics under covariate-dependent dropouts. The method involves weighing each permutation according to the retention probabilities, and thus requires estimation of the missing data mechanism. The proposed procedure is nonparametric in that no distributional assumption is necessary for the outcome variables and the missingness patterns. Monte Carlo approximation by the Gibbs sampler is proposed, and is shown to be fast and accurate via simulation. The method is illustrated in two small data sets for which asymptotic inferential procedures may not be appropriate.     

Semiparametric regression for periodic longitudinal hormone data from multiple menstrual cycles

We consider semiparametric regression for periodic longitudinal data. Parametric fixed effects are used to model the covariate effects and a periodic nonparametric smooth function is used to model the time effect. The within-subject correlation is modeled using subject-specific random effects and a random stochastic process with a periodic variance function. We use maximum penalized likelihood to estimate the regression coefficients and the periodic nonparametric time function, whose estimator is shown to be a periodic cubic smoothing spline. We use restricted maximum likelihood to simultaneously estimate the smoothing parameter and the variance components. We show that all model parameters can be easily obtained by fitting a linear mixed model. A common problem in the analysis of longitudinal data is to compare the time profiles of two groups, e.g., between treatment and placebo. We develop a scaled chi-squared test for the equality of two nonparametric time functions. The proposed model and the test are illustrated by analyzing hormone data collected during two consecutive menstrual cycles and their performance is evaluated through simulations.     

Postmetamorphic Growth and Metabolism of Long-Spined Black Sea Urchin (Diadema antillarum) Reared in the Laboratory

Postmetamorphic growth and metabolism measurements were obtained on two cohorts of laboratory-reared Diadema antillarum. The cohorts grew linearly from less than 1 mm to over 43 mm. Daily growth averaged 0.097 and 0.11 mm d^?1, respectively, for the two cohorts, and was found to differ significantly. Urchin metabolism was examined by a series of simultaneous measurements of oxygen consumption and ammonium excretion over 16 days on starved juveniles ranging 16.5 to 18.3 mm. Metabolic activity under conditions of starvation was used as a test of the viability of urchins reared in the laboratory with cultured food resources. Catabolic activity differed from the first week of starvation compared to the second. Metabolic response included: (1) a 2.2-fold increase in oxygen consumption rate; (2) 50% decline in ammonium excretion rate; and (3) a 5.1-fold increase in oxygen to nitrogen ratio. These measurements are consistent with a shift from almost pure protein catabolism during the first seven days of starvation to a lipid : protein catabolic ratio of 1 : 1 after the first week. Growth and metabolism experiments of this type are seen as a first step towards optimizing laboratory culture techniques of this species.     

Estimating incidence of the French BSE infection using a joint analysis of both asymptomatic and clinical BSE surveillance data

Bovine Spongiform Encephalopathy (BSE) clinical surveillance data were the main source of information to perform back-calculation of BSE infection incidence. Since 2001, systematic BSE screening tests enhanced the clinical surveillance and allowed to detect some preclinical, i.e. asymptomatic, cases of BSE. We propose a method to incorporate additional information provided by screening tests. It was the first time that a back-calculation model was developed for a full BSE clinical surveillance. In the spirit, our approach resembles what it was done in the Acquired Immune Deficiency Syndrome (AIDS) epidemic to incorporate the Human Immunodeficiency Virus (HIV) diagnosis. Nevertheless, in the BSE epidemic, we had to consider different surveillance systems, their peculiarity, and the phenomenon of communicating vessels between these surveillance systems. In addition, both the preclinical sensitivity of tests and the status of BSE cases, asymptomatic or clinical, were not precisely known. We applied the model to the French BSE epidemic in order to obtain an updated estimate of the incidence of BSE infection. Our back-calculation model fitted very well the observed data of each surveillance system. We detected a lengthening of the incubation period and estimated that the number of infections was very small in the late 1990s and zero in July 2001.     

Genetic variants in selenoprotein P plasma 1 gene (SEPP1) are associated with fasting insulin and first phase insulin response in Hispanics

Context

Insulin resistance is not fully explained on a molecular level, though several genes and proteins have been tied to this defect. Knockdowns of the SEPP1 gene, which encodes the selenoprotein P (SeP) protein, have been shown to increase insulin sensitivity in mice. SeP is a liver-derived plasma protein and a major supplier of selenium, which is a proposed insulin mimetic and antidiabetic agent.

Objective

SEPP1 single nucleotide polymorphisms (SNPs) were selected for analysis with glucometabolic measures.

Participants and measures

The study included1424 Hispanics from families in the Insulin Resistance Atherosclerosis Family Study (IRASFS). Additionally, the multi-ethnic Insulin Resistance Atherosclerosis Study was used. A frequently sampled intravenous glucose tolerance test was used to obtain precise measures of acute insulin response (AIR) and the insulin sensitivity index (S_I).

Design

21 SEPP1 SNPs (tagging SNPs (n = 12) from HapMap, 4 coding variants and 6 SNPs in the promoter region) were genotyped and analyzed for association.

Results

Two highly correlated (r² = 1) SNPs showed association with AIR (rs28919926; Cys368Arg; p = 0.0028 and rs146125471; Ile293Met; p = 0.0026) while rs16872779 (intronic) was associated with fasting insulin levels (p = 0.0097). In the smaller IRAS Hispanic cohort, few of the associations seen in the IRASFS were replicated, but meta-analysis of IRASFS and all 3 IRAS cohorts (N = 2446) supported association of rs28919926 and rs146125471 with AIR (p = 0.013 and 0.0047, respectively) as well as rs7579 with S_I (p = 0.047).

Conclusions

Overall, these results in a human sample are consistent with the literature suggesting a role for SEPP1 in insulin resistance.     

Closed chain assessment of quadriceps activation using the superimposed burst technique

The superimposed burst technique is used to estimate quadriceps central activation ratio during a maximal voluntary isometric contraction, which is calculated from force data during an open-chain knee extension task. Assessing quadriceps activation in a closed-chain position would more closely simulate the action of the quadriceps during activity. Our aim was to determine the test–retest reliability of the quadriceps central activation ratio in the closed chain.MethodsTwenty-two healthy, active volunteers (13M/12F; age = 23.8 ± 3; height = 72.7 ± 14.5 cm; mass = 175.3 ± 9.6 kg) were recruited to participate. Knee extension MVIC torque and the peak torque during a superimposed electrical stimulus delivered to the quadriceps during an MVIC were measured to estimate quadriceps CAR. Interclass correlation coefficients were used to assess test–retest reliability between sessions, and Bland–Altman plots to graphically assess agreement between sessions.ResultsTest–retest reliability was fair for CAR (ICC_2,k = 0.68; P = 0.005), with a mean difference of −2.8 ± 10.3%, and limits of agreement ranging −23.1–18.1%.ConclusionsCAR calculated using the superimposed burst technique is moderately reliable in a closed-chain position using technique-based instruction. Although acceptable reliability was demonstrated, wide limits of agreement suggest high variability between sessions.     

The Contribution of Crab Burrow Excavation to Carbon Availability in Surficial Salt-marsh Sediments

Geomorphology, vegetation and tidal fluxes are usually identified as the factors introducing variation in the flushing of particulate organic matter (POM) from tidal marshes to adjacent waters. Such variables may, however, be insufficient to explain export characteristics in marshes inhabited by ecosystem engineers that can alter the quantity and quality of POM on the marsh surface that is subject to tidal flushing. In this study we evaluated the balance between transfer of buried sedimentary organic carbon (C) to the marsh surface due to crab excavation (measured from the mounds of sediment excavated from burrows) and outputs of C from the surface due to sediment deposition within crab burrows (estimated from sediment deposited within PVC burrow mimics), in a Southwestern Atlantic salt marsh supporting dense (approximately 70 ind m⁻²) populations of the crab Chasmagnathus granulatus. C excavation by crabs was much greater than deposition of C within crab burrow mimics. Per area unit estimates of the balance between these two processes indicated that crabs excavated 5.98 g m⁻² d⁻¹ and 4.80 mg m⁻² d⁻¹ of total and readily (10 d) labile C, respectively. However, sediments excavated by crabs showed a significantly lower content of both total and readily-labile C than sediment collected in burrow mimics. This indicates that ecosystem engineering by burrowing crabs causes a net decrease in the concentration of C in the superficial sediment layers and, thus, an overall decrease in the amount of C that can be washed out of the marsh by tidal action. Incorporating the in situ activities of ecosystem engineers in models of marsh export should enhance understanding of the function of marshes in estuarine ecosystems.     

Characterization of a new bacteriocin produced from a novel isolated strain of Bacillus lentus NG121

The new bacteriocin is produced from Bacillus lentus NG121 isolated from Khameera – a traditional fermented food from Himachal Pradesh, India which has been reported for the first time in the literature to produce bacteriocin and exhibited very high activity units of 20 × 10⁵ AU (Arbitrary Units)/ml. This bacteriocin was partially purified and was further characterized to assess its preservation characteristics. It showed strong antimicrobial activity against the most challenging and serious test indicators like Listeria monocytogens and Staphylococcus aureus. There was a drastic decrease up to 70% in viable cells of the indicators within the first 10 h of adding partially purified bacteriocin thus proving its bactericidal action. It could withstand the high heat of 100 °C for 10 min of heating time without losing any activity. A wide range of pH tolerance i.e. from 5.0–10.0 was expressed by this bacteriocin. It was found completely sensitive to proteolytic enzyme trypsin. The unique combination of all the above mentioned characteristics makes the bacteriocin of newly isolated Bacillus lentus NG121, a food grade bacteria, highly desirable for preservation of different food items in the food industry.