两种石磺齿舌形态差异分析

显微观察了瘤背石磺(Onchidiumstruma)和石磺(O. verruculatum)齿舌的形态结构。运用差异系数法对两种石磺齿舌参数进行比较分析。利用SPSS10.0对瘤背石磺、石磺齿舌参数(齿舌长、齿舌头宽、齿舌中宽、齿舌尾宽、横列数、每排最少齿片数和每排最多齿片数)与个体参数(体长、体宽、体高、足长、足宽和体重)作回归分析。结果表明,两种石磺齿舌都很发达,外观呈长统靴状;齿片排成许多横列,每一横列均有中央齿一枚,侧齿若干无缘齿;两种石磺的齿舌头宽、齿舌中宽和齿舌尾宽差异极显著,但差异系数小于1.28,认为两种石磺的齿片形态存在明显的种间差异,但齿舌参数不适合作为石磺属贝类的分类依据;瘤背石磺的体宽和石磺的体重在评估各自齿舌生物学性状方面起到比较重要的作用。     

Heritability of and correlations among genotype-by-environment stability statistics for grain yield in bread wheat

Several genotype-by-environment stability measures are in use, but little information exists about their inheritance or genetic inter-relationships. Among those measures in common use are the linear regression coefficient (b), deviations from regression (s_b), coefficient of determination (R²), coefficient of phenotypic variation (CPV) and, more recently, interaction principal components (IPCA) of the additive-main-effect-and-multiplicative-interaction (AMMI) model. Because of the factorial structure of the data, the diallel cross is well suited to study these parameters and their relationship to quantitative traits. For this study a complete diallel cross, derived by mating eight lines from a broad based bread wheat breeding population, was grown for several growing seasons at two Ugandan locations, one of which was prone to yellow rust. Stability parameters and grain yield were measured for each cross. CPV had the highest narrow-sense heritability (h²=0.522) followed by IPCA1 of the AMMI (h²=0.461). Lowest narrow-sense heritabilities were calculated for b and R² (h²=0.150 and 0.100 respectively). There were high additive genetic correlations (r_A) between grain yield and CPV (r_A=−0.933), grain yield and IPCA1 (r_A=0.707), and grain yield and IPCA2 (r_A=0.751). The genetic association between CPV and IPCA1 was also high and negative (r_A= −0.934). These results suggest that it may be possible to select simultaneously for high and stable grain yield in this broad-based bread wheat breeding pool by selecting outyielders that exhibit a low CPV. Received: 25 July 2000 / Accepted: 7 December 2000     

Patterns of prey utilization in a web of orb-weaving spiderAraneus pinguis (Karsch)

The pattern of prey utilization of the orb-weaving spider Araneus pinguis was studies by comparing between arthropods restrained in the empty webs (spiders were removed) and those unattacked in the intact webs (spiders were not removed). The number of arthropods was larger in the empty webs than in the intact webs. In the empty webs, web area, mesh width, number of radii, and signal thread length were presumed to affect the number of arthropods left in a single web. As for the intact webs, web area, mesh width, and web-exposure time were important factors. In the empty webs, the density of arthropods decreased away from the hub. On the other hand, the density of unattacked arthropods in the intact webs was the same throughout the web. Arthropods in the empty webs were larger than those in the intact webs. The upper limit in size of unattacked arthropods increased along with the distance from the hub in the intact webs, but not in the empty webs. These results indicate increase in the minimum size of eaten arthropods increased in the former. This positive sizedistance relation may have resulted from the adaptive switching of spiders’ alternative foraging methods (i.e., the rapid attack at encounter and the later eating during web deconstruction) on the basis of the prey profitability.     

A multimeric model for murine anti-apoptotic protein Bcl-2 and structural insights for its regulation by post-translational modification.

A monomeric model for murine antiapoptotic protein Bcl-2 was constructed by comparative modeling with the software suite MPACK (EXDIS/DIAMOD/FANTOM) using human Bcl-xL as a template. The monomeric model shows that murine Bcl-2 is an all -helical protein with a central (helix 5) hydrophobic helix surrounded by amphipathic helices and an unstructured loop of 30 residues connecting helices 1 and 2. It has been previously shown that phosphorylation of Ser 70 located in this loop region regulates the anti-apoptotic activity of Bcl-2. Based on our current model, we propose that this phosphorylation may result in a conformational change that aids multimer formation. We constructed a model for the Bcl-2 homodimer based on the experimentally determined 3D structure of the Bcl-xL: Bad peptide complex. The model shows that it will require approximately a half turn in helix 2 to expose hydrophobic residues important for the formation of a multimer. Helices 5 and 6 of the monomeric subunit Bcl-2 have been proposed to form an ion-channel by associating with helices 5 and 6 of another monomeric subunit in the higher-order complex. In the multimeric model of Bcl-2, helices 5 and 6 of each subunit were placed distantly apart. From our model, we conclude that a global conformational change may be required to bring helices 5 and 6 together during ion-channel formation.Figure Hydrophobic interactions in the dimerization groove are shown. Helix 2' of monomer B interacts through residues V90, H91, L94, A97, G98, F101 and Y105 with the hydrophobic surface formed by residues in helices 3, 4, and 5 of the monomer A. Shown here is a lateral view of monomer A depicted in a surface model with hydrophobic regions in red. The backbone of the helix is shown using a neon representation in yellow and the interacting side chains are in blue.     

On the stochastic model for estimation of mutational distance between homologous proteins

Summary A set of simple equations is derived which gives the relationship between the observed amino acid differences per 100 codons and the evolutionary distance per 100 codons using Holmquist's stochastic model of molecular evolution.Contribution No. 910 from the National Institute of Genetics, Mishima, Shizuoka-ken 411 Japan.     

Restricted BLUP for Mixed Linear Models

A new estimation procedure for mixed regression models is introduced. It is a development of Henderson's best linear unbiased prediction procedure which uses the joint distribution of the observed dependent random variables and the unknown realisations of the random components of the model. It is proposed to replace the likelihood of the observations given the random components by the asymptotic likelihood of the maximum likelihood estimators and the prior distribution of the random components by a restricted prior distribution which is consistent with the usual restrictions placed on the random components when they are considered conditionally fixed.     

A method for determining overall protein fold from NMR distance restraints

Summary We describe a simple method for determining the overall fold of a polypeptide chain from NOE-derived distance restraints. The method uses a reduced representation consisting of two particles per residue, and a force field containing pseudo-bond and pseudo-angle terms, an electrostatic term, but no van der Waals or hard shell repulsive terms. The method is fast and robust, requiring relatively few distance restraints to approximate the correct fold, and the correct mirror image is readily determined. The method is easily implemented using commercially available molecular modeling software.     

Linear Predictivity: An Alternative for MANOVA and Multivariate Multiple Regression

The maximal linear predictable combination of a set of dependent variables is defined as that linear combination maximizing the multiple correlation coefficient with the predictor set. It allows the relative importance of a number of factors to be evaluated for the joint response, rather than for the response of each dependent variable in turn. The procedure is illustrated by an example. AMS subject classification: major 62J10, 62H20; minor 62H25.     

Comparison of non-linear and linear models for estimating haemoglobin adduct stability

According to the kinetic theory for the build-up and elimination of haemoglobin (Hb) adducts, unstable Hb adducts are simultaneously eliminated by zero-order Hb turnover and first-order chemical instability. Thus, the elimination of unstable Hb adducts is non-linear with respect to time. Nonetheless, many studies of Hb adduct stability have characterized the elimination of Hb adducts using linear zero-order or linear first-order models. This paper demonstrates the use of non-linear regression to estimate the first-order rate constant of Hb adduct instability (k) using data on the elimination of Hb adducts in rats dosed with benzene or ortho -toluidine. Results obtained using non-linear regression models are compared with results from the more commonly employed zero- and first-order linear models. It is shown that exposure estimates based on measured levels of unstable Hb adducts can be severely biased if zero-order turnover is assumed. Furthermore, based on published data, estimates of k are subject to estimated relative biases in the range of -4% to 96% when first-order linear models are used to characterize Hb adduct instability.     

基于k-mer组分信息的系统发生树构建方法

随着越来越多基因组的测序完成,基于全基因组的非比对的系统发生分析已成为研究热点。不同的生物物种或个体基因组之间的核酸组分不完全相同。遗传语言-DNA序列的信息很大程度上反映在其k—mer频数中。基于基因组序列k-mer频数的系统发生树则从新的角度为我们提供物种之间的亲缘关系。本文定义基于k-mer,频数的信息参数,并用它表征基因组序列,计算不同基因组之间信息参数的距离,用邻接法对84个病毒构建了系统发生树,发现构建的系统发生树很大程度上与已有的系统发生树相吻合。     

Regression equations for estimating stature from long bones of early Holocene European samples

Regression equations for estimating living stature from long bone lengths have been calibrated on a sample of European Neolithic skeletons (33 males and 27 females) by using both least-squares (model I) and major-axis (model II) regression techniques. Stature estimates of the skeletal sample have been made by means of Fully's anatomical method, a procedure based on the sum of all osseous components of height, providing the best approximations to the actual stature. The calculated equations have been tested, along with those generally used to predict stature of earlier European remains, on a small, well-preserved sample including Late Upper Paleolithic, Mesolithic, and Neolithic skeletons. The results indicate that the model II equations are particularly useful when very short or very tall individuals are involved and, at the same time, are among the best predictors of stature in less extreme conditions. © 1996 Wiley-Liss, Inc.     

The Error Rate of Tests for Regression Coincidence and Parallelism Under Unknown Multiplicative Heteroscedasticity

The usual F test of regression coincidence, which is appropriate under a homoscedastic model, is examined under a multiplicatively heteroscedastic model. The departure of the test from its nominal level is slight when the sample of explanatory variables is symmetric, but may be substantially inflated when the sample has positive skew. Conversely, the nominal level may be slightly depressed when the sample has negative skew. The size of the perturbation from the nominal level depends on the degree of heteroscedasticity, however its effect is more pronounced with positively skewed samples. Similar trends are evident for the usual F test of regression parallelism. There is no apparent pattern to the discrepancy of the level of the test with regard to the data which would permit empirical researchers to adjust their results.     

麦绿素加工专用大麦产量与气象因子的关系

以两个大麦品种为材料,在杭州条件下分7期播种,研究了麦绿素加工专用大麦产量与气象因子的关系．结果表明,第一收获期产量与播种后第1旬平均温度呈显著正相关,与第1、2旬的累积雨量显著负相关;第二收获期产量与第一次刈青后第2旬平均温度、第3旬降雨量显著正相关;三期总产量与播种后第2旬的平均温度呈极显著正相关,与第6旬平均温度呈极显著负相关．分别建立了第一收获期产量、三期总产量与生长天数、积温、降雨量及播种后第1、2、3旬平均温度的一元二次回归模型,寻优获得了在第一收获期高产基础上获较高总产量的适宜气象生态条件．     

A statistical test for differences in sexual dimorphism between populations

Many studies involve comparison of measures of sexual dimorphism between two samples. This comparison is used to test a variety of hypotheses, such as changing environmental conditions. Methods for testing the significance of the difference between two populations tend to be complex, and/or require access to complete original data. We offer a simplified approach which is based on a linear regression model using dummy variables. Our method is computationally simple and can be used with summary statistics (sample size, means, standard deviations) instead of raw data. We present three examples of the application of our method to problems in physical anthropology. We also note that our method has a broader range of applications apart from that of sexual dimorphism.     

A Classification of Trivariate Regression Models

The present study begins with a discussion of a topic frequently mentioned in the relevant literature, namely the division of multiple regression models with two predictors into five mutually excluding categories. The theoretical basis for this classification is criticized and a system of three mutually excluding categories is suggested which is free of the criticized inconsistencies.     

Model choice and influential cases for survival studies

Deletion diagnostics are developed for identifying observations that influence the estimates of regression parameters and the mixture parameter in the families of relative risk functions for failure time data. The diagnostic for the regression parameters is a generalization of Cain and Lange's (1984, Biometrics 40, 493-499) measure of individual influence. The generalizations of martingale residuals, Schoenfeld's partial residuals (1982, Biometrika 69, 239-241), and score residuals by Therneau, Grambsch, and Fleming (1990, Biometrika 77, 147-160) are also obtained. The influence of some observations on regression parameters can be drastically modified as the mixture parameter changes, even for a very small change. In addition, adding or deleting some observations might result in choosing different models. The diagnostics are applied to a family proposed by Guerrero and Johnson (1982, Biometrika 69, 309-314). One illustrative example is presented.