The two-sample problem with induced dependent censorship

Induced dependent censorship is a general phenomenon in health service evaluation studies in which a measure such as quality-adjusted survival time or lifetime medical cost is of interest. We investigate the two-sample problem and propose two classes of nonparametric tests. Based on consistent estimation of the survival function for each sample, the two classes of test statistics examine the cumulative weighted difference in hazard functions and in survival functions. We derive a unified asymptotic null distribution theory and inference procedure. The tests are applied to trial V of the International Breast Cancer Study Group and show that long duration chemotherapy significantly improves time without symptoms of disease and toxicity of treatment as compared with the short duration treatment. Simulation studies demonstrate that the proposed tests, with a wide range of weight choices, perform well under moderate sample sizes.     

BcMF9, a novel polygalacturonase gene, is required for both Brassica campestris intine and exine formation

Background and Aims

The polygalacturonase (PG) gene family has been found to be enriched in pollen of several species; however, little is currently known about the function of the PG gene in pollen development. To investigate the exact role that the PG gene has played in pollen development and about this family in general, one putative PG gene, Brassica campestris Male Fertility 9 (BcMF9), was isolated from Chinese cabbage (Brassica campestris ssp. chinensis, syn. B. rapa ssp. chinensis) and characterized.

Methods

RT-PCR, northern blotting and in situ hybridization were used to analyse the expression pattern of BcMF9, and antisense RNA technology was applied to study the function of this gene.

Key Results

BcMF9 is expressed in particular in the tapetum and microspore during the late stages of pollen development. Antisense RNA transgenic plants that displayed decreased expression of BcMF9 showed pollen morphological defects that resulted in reduced pollen germination efficiency. Transmission electron microscopy revealed that the homogeneous pectic exintine layer of pollen facing the exterior was over-developed and predominantly occupied the intine, reversing the normal proportional distribution of the internal endintine layer and the external exintine in transgenic pollen. Inhibition of BcMF9 also resulted in break-up of the previously formed tectum and baculae from the beginning of the binucleate stage, as a result of premature degradation of tapetum.

Conclusions

Several lines of evidence, including patterns of BcMF9 expression and phenotypic defects, suggest a sporophytic role in exine patterning, and a gametophytic mode of action of BcMF9 in intine formation. BcMF9 might act as a co-ordinator in the late stages of tapetum degeneration, and subsequently in the regulation of wall material secretion and, in turn, exine formation. BcMF9 might also play a role in intine formation, possibly via regulation of the dynamic metabolism of pectin.Key words: Brassica campestris, Chinese cabbage, exine, intine, PG, pollen wall, polygalacturonase, BcMF9     

Phytoplankton biomass and production in northern South China Sea during summer: Influenced by Pearl River discharge and coastal upwelling

Chlorophyll a and primary production were studied in northern South China Sea during summer from 2007 to 2008. Microplankton dominated total phytoplankton biomass in the coast, while picoplankton dominated in the offshore. Algae bloom caused by Thalassionema nitzschioides was found at the subsurface of upwelling regions (D2, C2) in 2008, and maximum of phytoplankton abundance reached 1.58 × 10⁶ ind L^?1. Integrated primary production ranged from 189.3 to 976.2 mg m^?2 d^?1 in 2007, and ranged from 652.1 to 6601 mg m^?2 d^?1 in 2008. PP showed positive relationship with IPP (p < 0.01) and negative relationship with SST (p < 0.05). Coastal upwelling and Pearl River discharge sustained high PP, and played important role in regulating the phytoplankton biomass and production.     

A Meta-Analysis of Parental Smoking and the Risk of Childhood Brain Tumors

Objective

Previous studies regarding the association between parental smoking and the risk of childhood brain tumors (CBT) have reported inconsistent results. We performed a meta-analysis to summarize evidence on this association and to quantify the potential dose-response relationship.

Methods

A systematic literature search was conducted in the Medline and Embase databases. The summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated. Dose–response meta-analysis was also performed for studies that reported categorical risk estimates for a series of smoking exposure levels.

Results

A total of 17 studies fulfilled the inclusion criteria. In the meta-analyses, the summary RRs (95% CIs) of CBT for maternal smoking during pregnancy, paternal smoking during pregnancy, maternal smoking before pregnancy, and paternal smoking before pregnancy were 0.96 (0.86–1.07), 1.09 (0.97–1.22), 0.93 (0.85–1.00), and 1.09 (1.00–1.20), respectively. Dose-response meta-analysis also showed no significant association between parental smoking and the risk of CBT.

Conclusions

Findings from our meta-analysis indicate that parental smoking may not be associated with a risk of CBT.     

Design and construction of a preparative-scale dynamic field gradient focusing apparatus

A linear model is used to show that dynamic field gradient focusing (DFGF) can be scaled to preparative capacity, approximately O (10 mgs). This paper explains how the preparative-scale DFGF apparatus was designed and fabricated. Scaled-down experiments and mathematical modeling guided material selection and design changes during construction to increase the probability that the prototype preparative-scale DFGF apparatus would perform as intended. The finished prototype successfully focused bovine hemoglobin from an initial concentration of 6.82 to 15 mg/mL and allowed for 86% recovery of injected protein.     

Comparison of Beta-value and M-value methods for quantifying methylation levels by microarray analysis

Background  

High-throughput profiling of DNA methylation status of CpG islands is crucial to understand the epigenetic regulation of genes. The microarray-based Infinium methylation assay by Illumina is one platform for low-cost high-throughput methylation profiling. Both Beta-value and M-value statistics have been used as metrics to measure methylation levels. However, there are no detailed studies of their relations and their strengths and limitations.     

链霉菌Z94-2碱性脂肪酶产生条件及酶学性质

在１５２ 株脂肪酶产生菌中,链霉菌Ｚ９４２ 产脂肪酶活力为５９６ｕ／ ｍＬ,其最适培养基（ｇ／Ｌ） 为：糊精１０ 、黄豆饼粉３０ 、尿素１０ 、Ｋ２ＨＰＯ４ ０－５ 、ＭｇＳＯ４ ０－５ 、ＮａＣｌ １ 和ＡＥＯ９ ０ ．５ ,产酶的最适条件为：初始ｐＨ９ ．５ ～１０－０ ,在２６ ℃培养４８ｈ 。用ＰＶＡ 橄榄油乳化系统测定该酶的最适ｐＨ９ ．８ ,最适温度３７ ℃,在ｐＨ８－６ ～１０－２ 于５ ℃存放２４ ｈ ,酶活力不变。０－１４ｍｏｌ／Ｌ 的氯化钙有较大的激活作用。     

Parasite reliance on its host gut microbiota for nutrition and survival

Studying the microbial symbionts of eukaryotic hosts has revealed a range of interactions that benefit host biology. Most eukaryotes are also infected by parasites that adversely affect host biology for their own benefit. However, it is largely unclear whether the ability of parasites to develop in hosts also depends on host-associated symbionts, e.g., the gut microbiota. Here, we studied the parasitic wasp Leptopilina boulardi (Lb) and its host Drosophila melanogaster. Results showed that Lb successfully develops in conventional hosts (CN) with a gut microbiota but fails to develop in axenic hosts (AX) without a gut microbiota. We determined that developing Lb larvae consume fat body cells that store lipids. We also determined that much larger amounts of lipid accumulate in fat body cells of parasitized CN hosts than parasitized AX hosts. CN hosts parasitized by Lb exhibited large increases in the abundance of the bacterium Acetobacter pomorum in the gut, but did not affect the abundance of Lactobacillus fructivorans which is another common member of the host gut microbiota. However, AX hosts inoculated with A. pomorum and/or L. fructivorans did not rescue development of Lb. In contrast, AX larvae inoculated with A. pomorum plus other identified gut community members including a Bacillus sp. substantially rescued Lb development. Rescue was further associated with increased lipid accumulation in host fat body cells. Insulin-like peptides increased in brain neurosecretory cells of parasitized CN larvae. Lipid accumulation in the fat body of CN hosts was further associated with reduced Bmm lipase activity mediated by insulin/insulin-like growth factor signaling (IIS). Altogether, our results identify a previously unknown role for the gut microbiota in defining host permissiveness for a parasite. Our findings also identify a new paradigm for parasite manipulation of host metabolism that depends on insulin signaling and the gut microbiota.Subject terms: Animal physiology, Microbial ecology