制备遗传工程小鼠的技术改进

遗传工程小鼠是当今生命科学领域集成度最高的研究体系之一。特别在“人类基因组计划和小鼠基因组计划”完成后,遗传工程小鼠在制备人类疾病模型、药物开发和评价、基因功能分析以及比较基因组学中发挥着越来越重要的作用。由此,也推动了遗传工程小鼠相关技术的快速发展。就遗传工程小鼠制备的现况、存在的问题以及新策略等相关问题进行了总结。     

体外培养骨髓巨核细胞脱氢酶活性的细胞化学观察

本文采用液体培养体系结合酶细胞化学方法,对体外培养不同发育阶段的小鼠肾髓巨核细胞乳酸脱氢酶、苹果酸脱氢酶、谷氨酸脱氢酶的活性变化进行了动态观察。在9天培养期间,巨核细胞的增殖数在5—7天达到高峰,并随时间有不同程度分化。对培养3、5、7、9天的巨核细胞进行酶细胞化学研究,结果表明,巨核细胞在发育成熟前,三种酶活性均有增高。提示巨核细胞在分化过程中,糖酵解及三羧酸循环代谢均有增强。     

Evaluation of FKBP and DHFR based destabilizing domains in Saccharomyces cerevisiae

Two orthogonal destabilizing domains have been developed based on mutants of human FKBP12 as well as bacterial DHFR and these engineered domains have been used to control protein concentration in a variety of contexts in vitro and in vivo. FKBP12 based destabilizing domains cannot be rescued in the yeast Saccharomyces cerevisiae; ecDHFR based destabilizing domains are not degraded as efficiently in S. cerevisiae as in mammalian cells or Plasmodium, but provide a starting point for the development of domains with increased signal-to-noise in S. cerevisiae.     

Population size estimation in a two-list surveillance system with a discrete covariate

Summary .   Capture–recapture methods are widely adopted to estimate sizes of populations of public health interest using information from surveillance systems. For a two-list surveillance system with a discrete covariate, a population is divided into several subpopulations. A unified framework is proposed in which the logits of presence probabilities are decomposed into case effects and list effects. The estimators for the whole population and subpopulation sizes, their adjusted versions, and asymptotic standard errors admit closed-form expressions. Asymptotic and bootstrap individual and simultaneous confidence intervals are easily constructed. Conditional likelihood ratio tests are used to select one from three possible models. Real examples are investigated.     

Estimating the species accumulation curve using mixtures

As a significant tool in ecological studies, the species accumulation curve or the collector's curve is the graph of the expected number of detected species as a function of sampling effort. The problem of estimating the species accumulation curve based on an empirical data set arising from quadrat sampling is studied in a nonparametric binomial mixture model. It will be shown that estimating the species accumulation curve not only is independent of the unknown number of species but also includes estimating the number of species as a limiting case. For the purpose of interpolation, moment-based estimators, associated with asymptotic confidence intervals, are developed from several points of view. A likelihood-based procedure is developed for the purpose of extrapolation, associated with bootstrap confidence intervals. The proposed methods are illustrated by ecological data sets.     

Transient and permanent gene transfer into the brain of the teleost fish medaka (Oryzias latipes) using human adenovirus and the Cre-loxP system

In this study, we demonstrated that human type-5 adenovirus infected the brain of the teleost fish, medaka (Oryzias latipes), in vivo. Injection of adenoviral vector into the mesencephalic ventricle of medaka larvae induced the expression of reporter genes in some parts of the telencephalon, the periventricular area of the mesencephalon and diencephalon, and the cerebellum. Additionally, the Cre-loxP system works in medaka brains using transgenic medaka carrying a vector containing DsRed2, flanked by loxP sites under control of the β-actin promoter and downstream promoterless enhanced green fluorescent protein (EGFP). We demonstrated that the presence of green fluorescence depended on injection of adenoviral vector expressing the Cre gene and confirmed that EGFP mRNA was transcribed in the virus-injected larvae.     

Generalized maximally selected statistics

SUMMARY: Maximally selected statistics for the estimation of simple cutpoint models are embedded into a generalized conceptual framework based on conditional inference procedures. This powerful framework contains most of the published procedures in this area as special cases, such as maximally selected chi(2) and rank statistics, but also allows for direct construction of new test procedures for less standard test problems. As an application, a novel maximally selected rank statistic is derived from this framework for a censored response partitioned with respect to two ordered categorical covariates and potential interactions. This new test is employed to search for a high-risk group of rectal cancer patients treated with a neo-adjuvant chemoradiotherapy. Moreover, a new efficient algorithm for the evaluation of the asymptotic distribution for a large class of maximally selected statistics is given enabling the fast evaluation of a large number of cutpoints.     

便秘相关肠道微生物研究进展

随着生活水平的提高、生活节奏的加快、年龄的增长及饮食结构的改变等,便秘的发生率与日俱增。便秘严重危害患者的身心健康,并带来诸多并发症。便秘造成肠道的微生态改变,总的来说是益生菌的种类和数目减少,而有害菌或条件治病菌却显著增加。以活的益生菌作为微生态制剂,对缓解症状、治愈便秘和恢复肠道正常菌群有十分显著的作用,其应用前景也相当广阔。本研究对便秘相关肠道微生物的研究进展进行综述。     

The relative costs and benefits of territorial defense and the two conditional male mating tactics in the Comanche Springs pupfish (Cyprinodon elegans)

We examined the aggressive costs and reproductive benefits of territorial defense and its alternatives in a population of the Comanche Springs pupfish (Cyprinodon elegans). The breeding system was characterized by three different male mating tactics: territorial defense, satellite positioning, and sneak spawning. The mating tactic adopted by males reflected the males' sizes. Territorial residents were the largest, satellites were medium-sized, and sneakers were the smallest adult males observed. Consistent with the hypothesis that primary mating tactics are relatively high-cost, high-benefit strategies, we found that territorial males engaged in a number of aggressive encounters but had higher reproductive successes than any other males. However, our observations did not support the premise that conditionally breeding males engage in relatively low-benefit, low-cost tactics. Medium satellites and small sneakers acquired fewer spawns than did territorial males, but both satellites and sneakers were involved in as much aggression as territorials. That is, the data supported the prediction that satellite or sneaker males with the inability to compete for territories would attempt to accrue some reproductive opportunities in the presence of territorial males despite the high costs of spending time on the breeding grounds. Adopting conditional tactics appeared to allow satellites and sneakers to make the best of a bad situation. During a subsequent breeding season, large males were absent from the population, and medium-sized males established territories. The aggressive behavior exhibited by medium residents was similar to the previous year, but these males did not acquire higher reproductive successes than medium satellites had. The implications of switching tactics and the influence of operational sex ratios on the costs and benefits of the male tactics are briefly addressed. Electronic Publication     

Covariate measurement error adjustment for matched case-control studies

We propose a conditional scores procedure for obtaining bias-corrected estimates of log odds ratios from matched case-control data in which one or more covariates are subject to measurement error. The approach involves conditioning on sufficient statistics for the unobservable true covariates that are treated as fixed unknown parameters. For the case of Gaussian nondifferential measurement error, we derive a set of unbiased score equations that can then be solved to estimate the log odds ratio parameters of interest. The procedure successfully removes the bias in naive estimates, and standard error estimates are obtained by resampling methods. We present an example of the procedure applied to data from a matched case-control study of prostate cancer and serum hormone levels, and we compare its performance to that of regression calibration procedures.     

Use of conditional distributions in the analysis of ion channel recordings

A method to test the Markov nature of ion channel gating is proposed. It makes use of singly and doubly conditional distributions. The application of this method to recordings from single BK channels provides evidence that at least two states of the underlying kinetic scheme are left at a constant rate. Moreover, the probabilities, when leaving a state, of reaching another given state are shown to be constant for all the states of the system. Offprint requests to: D. Petracchi     

Isolation and characterization of a temperature-sensitive conditional mutant of Escherichia coli altered for the control of phosphate-regulated proteins

We have identified a conditional mutation which confers a ple?otropic phenotype to Escherichia coli cells: no growth at temperature higher than 36 degrees C, an altered control of the synthesis of several phosphate-regulated polypeptides (including alkaline phosphatase, sn-glycerol-3-phosphate binding protein, phosphate binding protein and outer membrane porin protein PhoE) after growth at 36 degrees C and a wild-type phenotype at 30 degrees C. This mutation was located at minute 89.5 on the E. coli chromosome in a gene we have called cpr for conditional phosphate-regulated.     

New understandings on folliculogenesis/oogenesis regulation in mouse as revealed by conditional knockout

In comparison to conventional knockout technology and in vitro research methods, conditional gene knockout has remarkable advantages. In the past decade, especially during the past five years, conditional knockout approaches have been used to study the regulation of folliculogenesis, follicle growth, oocyte maturation and other major reproductive events. In this review, we summarize the recent findings about folliculogenesis/oogenesis regulation, including the functions of four signaling cascades or glycoprotein domains that have been extensively studied by conditional gene deletion. Several other still fragmented areas of related work are introduced which are awaiting clarification. We have also discussed the future potential of this technology in clarifying gene functions in reproductive biology.     

Multi-criteria clustering in genotype-environment interaction problems

Summary Significant genotype-environment interactions in an ANOVA can be found for a number of reasons: one is the differences in the among-environments variances for each genotype, another is the differences in the ordering of the environments by each genotype. Using conditional clustering, groups may be formed in which the means, variances and patterns are used simultaneously but separately to decide on group homogeneity. Contribution No. I-685 from the Engineering and Statistical Research Institute     

Small-sample confidence regions in exponential families

This article presents an algorithm for small-sample conditional confidence regions for two or more parameters for any discrete regression model in the generalized linear interactive model family. Regions are constructed by careful inversion of conditional hypothesis tests. This method presupposes the use of approximate or exact techniques for enumerating the sample space for some components of the vector of sufficient statistics conditional on other components. Such enumeration may be performed exactly or by exact or approximate Monte Carlo, including the algorithms of Kolassa and Tanner (1994, Journal of the American Statistical Association 89, 697-702; 1999, Biometrics 55, 246-251). This method also assumes that one can compute certain conditional probabilities for a fixed value of the parameter vector. Because of a property of exponential families, one can use this set of conditional probabilities to directly compute the conditional probabilities associated with any other value of the vector of the parameters of interest. This observation dramatically reduces the computational effort required to invert the hypothesis test to obtain the confidence region. To construct a region with confidence level 1 - alpha, the algorithm begins with a grid of values for the parameters of interest. For each parameter vector on the grid (corresponding to the current null hypothesis), one transforms the initial set of conditional probabilities using exponential tilting and then calculates the p value for this current null hypothesis. The confidence region is the set of parameter values for which the p value is at least alpha.     

Approximate Monte Carlo conditional inference in exponential families

This article presents an algorithm for approximate frequentist conditional inference on two or more parameters for any regression model in the Generalized Linear Model (GLIM) family. We thereby extend highly accurate inference beyond the cases of logistic regression and contingency tables implimented in commercially available software. The method makes use of the double saddlepoint approximations of Skovgaard (1987, Journal of Applied Probability 24, 875-887) and Jensen (1992, Biometrika 79, 693-703) to the conditional cumulative distribution function of a sufficient statistic given the remaining sufficient statistics. This approximation is then used in conjunction with noniterative Monte Carlo methods to generate a sample from a distribution that approximates the joint distribution of the sufficient statistics associated with the parameters of interest conditional on the observed values of the sufficient statistics associated with the nuisance parameters. This algorithm is an alternate approach to that presented by Kolassa and Tanner (1994, Journal of the American Statistical Association 89, 697-702), in which a Markov chain is generated whose equilibrium distribution under certain regularity conditions approximates the joint distribution of interest. In Kolassa and Tanner (1994), the Gibbs sampler was used in conjunction with these univariate conditional distribution function approximations. The method of this paper does not require the construction and simulation of a Markov chain, thus avoiding the need to develop regularity conditions under which the algorithm converges and the need for the data analyst to check convergence of the particular chain. Examples involving logistic and truncated Poisson regression are presented.