Gene conversion,unequal crossing-over and mispairing at a non-tandem duplication during meiosis of Saccharomyces cerevisiae

Summary We have developed a novel system to examine conversion, exchange and mispairing involving a nontandem duplication of the ade8 locus in yeast by monitoring the segregation of heterozygous markers between the duplicated sequence. Plasmid Yrp 17 carries the yeast selectable markers URA3 ⁺ and TRP1 ⁺. Yrpl7 derivatives with a 4 kb insert carrying ade8-18 were used to clone the mutations trpl-1 and ura3-1 by gap repair. Integrants of the resulting plasmids at the Ade8 locus were crossed to yield diploid hybrids with a non-tandem duplication of Ade8 and heterozygosity for the plasmid markers between the duplicated sequences. 1192 complete, unselected asci were analyzed and 270 exhibiting recombination of the markers contributed by the plasmid were analyzed by Southern transfers to detect changes in plasmid sequences. Twenty-seven tetrads had unequal homologous exchanges and five had unequal sister-chromatid exchanges. Seven tetrads carry an additional copy of the integrated plasmid and ten are missing one. We propose that these two classes represent conversions of the entire 11 kb plasmid, which occur after misalignment and formation of an unpaired loop. Mispairing is a frequent event, and occurs in approximately fifty percent of all meioses. The system described provides a means to determine the meiotic rules of conversion, exchange and pairing for duplicated DNA sequences.     

Illustration of the Importance of Adjustment for within- and between-Person Variability in Dietary Intake Surveys for Assessment of Population Risk of Micronutrient Deficiency/Excess Using an Example Data Set

Nutrition intervention decisions should be evidence based. Single 24-h recalls are often used for measuring dietary intake in large dietary studies. However, this method does not consider the day-to-day variation in populations’ diets. We illustrate the importance of adjustment of single 24-h recall data to remove within-person variation using the National Cancer Institute method to calculate usual intake when estimating risk of deficiency/excess. We used an example data set comprising a single 24-h recall in a total sample of 1326 1–<10-year-old children, and two additional recalls in a sub-sample of 11%, for these purposes. Results show that risk of deficiency was materially overestimated by the single unadjusted 24-h recall for vitamins B12, A, D, C and E, while risk of excess was overestimated for vitamin A and zinc, when compared to risks derived from usual intake. Food sources rich in particular micronutrients seemed to result in overestimation of deficiency risk when intra-individual variance is not removed. Our example illustrates that the application of the NCI method in dietary surveys would contribute to the formulation of more appropriate conclusions on risk of deficiency/excess in populations to advise public health nutrition initiatives when compared to those derived from a single unadjusted 24-h recall.     

困境家庭环境与儿童健康机会不平等研究 ——来自全国7省调查分析

儿童健康是健康中国建设的基础,是我国社会可持续发展的重要保障.家庭是儿童健康成长的重要环境.文章基于相互作用的家庭环境系统框架,依据2018年在我国7省份进行的"困境家庭儿童健康状况"专项调查数据,使用基于有序多分类回归的夏普里值(Shapley)分解,详细考察了家庭环境因素导致困境家庭儿童健康机会不平等及其相对贡献....     

Qualification of a microfluidics-based electrophoretic method for impurity testing of monoclonal antibodies

In this work, we present a comprehensive evaluation of the Agilent Bioanalyzer, a microfluidics-based electrophoretic device that was used for impurity testing of a monoclonal antibody (mAb). We compared the system to SDS-PAGE, both operated under non-reducing conditions and found a significant improvement of accuracy for the Bioanalyzer. In addition, the latter exhibited a larger assay range and lower limit of quantitation (LOQ) based on a predefined total error limit of ±30%. However, during method qualification applying a three-factor nested design with two operators performing duplicate measurements per day, each on 4 different days, we observed unpredictable recurring quantitative outliers using the chip-based system. In-depth analysis on multiple runs with various chip lots confirmed the above finding and indicated that most likely on-chip dye labeling and/or post-column background fluorescence elimination are not compatible with the large size of the intact antibody as similar findings were observed for myosin used as upper marker for time correction. Interestingly, after reducing the intact antibody into light and heavy chain, we resolved the outlier issue. Eventually, requalification of the micro-fabricated analytical device under reducing conditions revealed only 1 out of 32 quality control samples (QCs) exceeding the ±30% total error limits.     

De novo polyalanine expansion of <Emphasis Type="Italic">PHOX2B</Emphasis> in congenital central hypoventilation syndrome: unequal sister chromatid exchange during paternal gametogenesis

The expansion of polyalanine repeats is known to cause at least nine disorders, including congenital central hypoventilation syndrome (CCHS). Unequal crossover has been speculated as the expanding mechanism, in contrast to strand slippage in polyglutamine expansion disorders. We carried out segregation analysis of PHOX2B in 13 de novo families with CCHS and found that 6 families were informative regarding a parental origin of polyalanine expansion, with all 6 mutants being of paternal origin. Four of them were also informative regarding a chromosomal event and their mutants were derived from unequal sister chromatid exchange. It is probable that de novo expansion of polyalanine repeats in CCHS results mainly from unequal sister chromatid exchange during spermatogenesis due to the secondary DNA structure of imperfect trinucleotide repeats encoding polyalanine tracts.     

Two cases of chronic obstructive pulmonary disease with undetectable diffusing capacity for carbon monoxide

Pulmonary diffusing capacity for carbon monoxide (DL_CO) is a valuable pulmonary function test to evaluate the gas exchange capacity of the lungs. Generally, DL_CO values are significantly lower in patients with chronic obstructive pulmonary disease (COPD), particularly in those with a predominantly emphysema phenotype. However, it is extremely rare that DL_CO values cannot be obtained for reasons other than technical errors. Herein, we report two patients with COPD in whom DL_CO values were undetectable without prolonging the breath-holding time for the test. We discuss possible mechanisms for these peculiar findings.     

不同剂量布地奈德联合异丙托溴铵雾化吸入治疗慢性阻塞性肺疾病急性加重期疗效观察

目的:观察不同剂量布地奈德联合异丙托溴铵雾化吸入治疗慢性阻塞性肺疾病急性加重期(AECOPD)的疗效。方法:将本院呼吸科住院部收治87例AECOPD患者随机分成两组,布地奈德高剂量组43例和低剂量组44例,两组常规治疗,同时加用布地奈德联合异丙托溴铵雾化吸入,观察治疗后两组患者动脉血气、肺功能、疗效、住院时间及出现不良反应。结果:两组治疗7 d后比较,临床症状评分,PO2及PCO2均有明显改善,治疗前后比较,P<0.05。高剂量组疗效优于低剂量组,治疗后FEV1与FEV1/FVC明显改善,住院时间显著缩短(P<0.05)。结论:布地奈德混悬液和异丙托溴铵联合雾化吸入具有较强的快速抗炎作用和缓解急性发作的疗效,提高布地奈德的剂量在一定程度上能增加疗效,但不良反应没有随之增加。     

选用平方根代换还是对数代换?——一个实用的判别方法

对调查和实验数据进行统计学分析时,常有需要先经代换的情形,本文结合实例,介绍一种在平方根代换和对数代换之间,如何选择的判别方法。     

Isolation and characterization of rad51 orthologs from Coprinus cinereus and Lycopersicon esculentum, and phylogenetic analysis of eukaryotic recA homologs

In eubacteria, the recA gene has long been recognized as essential for homologous recombination and DNA repair. Recent work has identified recA homologs in archaebacteria and eukaryotes, thus emphasizing the universal role this gene plays in DNA metabolism. We have isolated and characterized two new recA homologs, one from the basidiomycete Coprinus cinereus and the other from the angiosperm Lycopersicon esculentum. Like the RAD51 gene of Saccharomyces cerevisiae, the Coprinus gene is highly induced by gamma irradiation and during meiosis. Phylogenetic analyses of eukarotic recA homologs reveal a gene duplication early in eukaryotic evolution which gave rise to two putatively monophyletic groups of recA-like genes. One group of 11 characterized genes, designated the rad51 group, is orthologous to the Saccharomyces RAD51 gene and also contains the Coprinus and Lycopersicon genes. The other group of seven genes, designated the dmc1 group, is orthologous to the Saccharomyces DMC1 gene. Sequence comparisons and phylogenetic analysis reveal extensive lineage- and gene-specific differences in rates of RecA protein evolution. Dmc1 consistently evolves faster than Rad51, and fungal proteins of both types, especially those of Saccharomyces, change rapidly, particularly in comparison to the slowly evolving vertebrate proteins. The Drosophila Rad51 protein has undergone remarkably rapid sequence divergence. Received: 20 July / 25 October 1996     

The analysis of neuronal discharge sequences: change-point estimation and comparison of variances

A key problem in neurophysiology is to determine whether, after presentation of a stimulus, there has been a modification in the discharge of a recorded neuron and if so, an attempt is made to estimate the latency of the response. The estimation problem can be considered as that of the estimation of a change-point in a sequence of random variables. The gamma distribution is adequate to model the distribution of intervals between action potentials for different types of neurons. Simulations show that the maximum likelihood estimator based on this model is efficient and robust. An additional problem, in the case of experiments in which a movement follows the stimulus, is to determine whether a response is related to the stimulus or to the movement. A test based on the comparison of marginal scales of a bivariate distribution is proposed. The whole procedure has been tested in simulation and with real examples.