Examination of protein sequence homologies: II. SixEscherichia coli L7/L12-type ribosomal “A” protein sequnces from eukaryotes and metabacteria,contrasted with those from prokaryotes

Summary Four complete and three partial sequences ofE. coli L7/L12-type ribosomal A proteins obtained from four eukaryotes (Saccharomyces cerevisiae, Artemia salina, rat liver, and wheat germ), two metabacteria (Halobacterium cutirubrum andMethanobacterium thermoautotrophicum), and the prokaryoteEscherichia coli have been compared using a computer program that searches for homologous tertiary structures. Comparison matrices show that eukaryotic sequences sequentially match each other if deletions and/or insertions of certain residues (gaps) are assumed at specific sites corresponding to residues 36, 51, 72, and 94 ofS. cerevisiae protein YL44c. This is similar to what was previously found in prokaryotes. Metabacteria, which exhibit eukaryote-type sequences, must have separated from the eukaryotes in ancient times, because an additional deletion site is found in their sequences and their sequences have low correlation coefficients with those of all the other eukaryotes. When the eukaryote-type A proteins (110–111 residues) are compared withE. coli L7/L12 (120 residues) four groups of well-matching segments are found. It was deduced that the eukaryote-type A proteins had regenerated from the prokaryote types by a transposition and several deletions, resulting in the eukaryote-type lengths. The correspondence between the eukaryotic and prokaryotic proteins, as well as that among eukaryotic proteins themselves, is discussed in terms of protein evolution.In addition, ribosomal protein YL35 fromS. cerevisiae has been compared with RL37 from rat liver, with results indicating five well-matching parts separated by four gaps, one of which consists of 20 residues. These results contrasts with those previously reported by Lin et al. No prokaryotic counterparts to these ribosomal proteins have yet been identified.     

CD correlation of C-2′substituted monocyclic carotenoids

The scope and limitation of circular dichroism (CD) correlations of several C-2′ substituted monocyclic monochiral, homodichiral and heterodichiral carotenoids have been investigated, aiming at the assignment of absolute configuration at C-2′ by using the diester and 2′-β-d-tetraacetylglucosyl derivative of (2′R)-plectaniaxanthin and a synthetic chiral C₄₅-carotene as key references. The correlations are based on the additivity hypothesis, the conformational rule and a comparison of CD spectra, preferably conservative ones. Quantitative aspects of the conformational rule are considered. Substituent effects at C-2′ and C-1′ have been studied. Absolute configurations are suggested for (2′)-phleixanthophyll (3S,2′S)-2′-hydroxyflexixanthin, (3R,2′S)-myxoxanthophyll, (3S,2′S-4-ketomyxoxanthophyll (3R,2′S)-myxol-2′-O-methyl methylpentoside and (2R,2′S)-Cp. 473 from relevant CD correlations. The chiralities of (2′S)-4-ketophleixanthophyll and (2R,6R,2′S)-A.g. 471 are suggested from biogenetic considerations. A chemosystematic consideration of chirality and source is included.     

应用原生动物群落评价石油废水对燕山区水系的影响

北京燕山地区的水系——周口店河、东沙河、丁家洼河、西沙河、大石河中游受到石油废水和生活污水的影响。作者在5条河流同步采用载玻片法、PFu(Polyurethane Foam Unit)法和传统的浮游生物沉淀法收集原生动物群落。对群落的种类组成、多样性指数、群集过程(Seq、G、T90％)等参数进行了测定。3种方法都能监测出周口店河有严重的毒性效应,载玻片法和PFU法能监测出含石油的废水在东沙河逐渐净化的过程,PFU法能最终判断出西沙河的有机污染比丁家洼河大。因此这5条河流的污染程度是依大石河、丁家洼河、西沙河、东沙河、周口店河的次序而递增。周口店河上游站因含强酸、强碱的废水引起的毒性已迫使原生动物无法生存。由于东沙河的汇入,大石河的中游地段优势种出现以自养性向异养性转化、丰度增加、多样性指数下降的富营养化现象,对北拒马河亦有潜在的压迫。     

Reaction norms for developmental time and weight at eclosion in Drosophila mercatorum

We determined reaction norms for developmental time and weight at eclosion for 2 isozygous and 11 genetically mixed strains of Drosophila mercatorum in four culture media differing in yeast concentration. With decreasing yeast concentration, development was delayed, the weight of emerging flies decreased, and the phenotypic variance of both variables increased. Differences among stocks and significant stock × yeast interactions indicated genetic variance for both variables within environment and different phenotypic responses of stocks across environments. The phenotypic correlation between developmental time and weight was negative at low yeast concentrations and disappeared gradually with increasing yeast. The comparison of completely homozygous with genetically heterogenous stocks showed that most of the increase of variability with deteriorating environment was due to the changing expression of genetic variance. The genetic correlation between developmental time and weight turned from negative in poor to positive in rich medium, while the environmental covariance was negative in all media. Plotting the reaction norms in the developmental time-weight plane rather than separately for each trait reveals most of these results at a glance. It also suggests that much of the genetic variance might be additive, because an effect of the half-sib family structure inherent in the design is clearly visible in the plot. We interpret the pattern of changing variances and covariances, pointing out that the special growth physiology of Drosophila and the way environmental factors affect it must be taken into account. We briefly discuss the implications of changing genetic correlations among traits for the evolution of phenotypic plasticity in general.     

Avian predation upon a mixed community of common voles (Microtus arvalis) and wood mice (Apodemus sylvaticus)

Summary Pellets of diurnal avian predators (mainly kestrels and buzzards) were analysed to prove the hypothesis of selective predation for a mixed population of small rodents. It was found that voles heavily predominated as prey over mice (up to a factor of 19 during winter). Within both prey species, predation focussed on distinct parts of the populations: during winter the heaviest specimens were preferentially captured, during summer the subadults were in an exposed position. In the voles, an additional predominance of males occurred (up to a factor of 5.2 during summer). These findings verify the assumption of Errington (1956) that speciments of a low social rank are susceptible to the highest risk of predation.     

A Microcomputer Program for Evaluating Sampling Error: an Application to Stereological Methods for Electron Microscopy

In situations where there is a need to minimize sampling error or sample size, the coefficient of variation (CV) may be used to evaluate sampling error as a function of the number of observations or subjects in a sample. For example, CV is useful for estimating the minimum number of electron micrographs (N_min) required to obtain a representative field sample for stereological analysis. To facilitate the determination of N_min, we have written a program (COEFficient) for DOS microcomputers which calculates CVs. COEF assists the user in reducing error to that which solely reflects biological variability, thereby minimizing the time and cost of subsequent analyses.     

Alternative partitioning of the genotype-by-environment interaction

Summary Alternative methods for partitioning the genotype-by-environment interaction, for an arbitrary number of genotypes or environments, were examined. Partitioning of the interaction is important in order to determine the nature of the interaction. Two methods of partitioning were examined; both separated the interaction into two types: (1) due to heterogeneous variances or (2) due to imperfect correlations. Method 1 was based on heterogeneity among environments in the scaling of differences among genotypes. Method 2 was based on heterogeneity among genotypes in the scaling of differences among environments. Any remaining interaction arises from deviations from the perfect positive correlation of genotypic rankings among environments (Method 1) or of environmental rankings among genotypes (Method 2). Method 1 is more appropriate for random genotypes that are to be tested in either fixed or random environments. With Method 1, the interactions that arise mainly from heterogeneity of genotypic scaling among environments are generally unimportant. However, if environments are fixed and interactions are mainly due to imperfect correlations of rankings, specialized lines may be indicated for each environment. Method 2 is more useful in evaluating fixed genotypes for sensitivity to random environments. A partitioning of the interaction into that due to the type of interaction within each genotype was shown to be useful in that situation.Journal Paper No. 123737 of the Purdue University Agricultural Experiment Station     

Application of photon correlation spectroscopy as a technique for detecting culture contamination

The application of photon correlation spectroscopy (PCS) to detect culture contamination in chemostats was studied. It was found that the presence of a given particle size in a population of particles of a different size could be detected, but this ability was strongly dependent on particles of a different size could be detected, but this ability was strongly dependent on particle size difference and was most sensitive when contaminants are larger than the host. The inherent polydisparity of actively growing and dividing microbial cells negates any advantage in the use of multi-angle PCS to detect contaminants.     

测定叶片蒸腾系数的封闭系统

光合测定系统内附装一控制定温的定量吸湿装置,使这系统在测定叶片光合(或呼吸)过程中,湿度保持恒定,可以测得蒸腾量及蒸腾速率,从而得到蒸腾系数。文中还介绍CO_2的标定方法。