Further results on the survival of a gene represented in a founder population

This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982).     

Effects of Autogamy In Paramecium Tetraurelia On Catalase Activity and On Radiosensitivity to Natural Ionizing Radiations

SYNOPSIS Catalase activity of Paramecium tetraurelia decreased during autogamy and recovered to normal 5 days later. Autogamy also caused changes in the ciliate's sensitivity to natural ionizing radiations—the decrease in cell growth rate previously described in shielded cultures did not occur when autogamous cells were used. Maximum effect of shielding was observed in 11-day-old postautogamous cells. the role of the catalase in the mechanism of natural irradiation effect is discussed.     

Gene expression changes associated with cytotoxicity identified using cDNA arrays

In order to investigate gene expression changes associated with cytotoxicity, we used cDNA arrays to monitor the expression of over 5,000 genes in response to toxic stress in the HepG2 liver cell line. Cells were treated with cytotoxic doses of acetaminophen, caffeine or thioacetamide for nine time points ranging from 1 to 24 h. Samples of mRNA from each time point were used to prepare radiolabeled cDNA, which was hybridized to nylon-membrane-based cDNA arrays. High-stringency washes were applied to reduce cross-hybridization. Analysis of spot intensities revealed that each compound led to approximately 150-250 gene expression changes that were sustained over at least three adjacent time points. The affected genes could be classified into clusters based on their temporal patterns of differential expression. A common set of 44 genes showed similar expression changes in response to all three compounds. Of these changes, 90% could be confirmed by quantitative RT-PCR analysis. The results indicate that detailed array-based time-course studies, coupled with a sensitive and highly specific confirmation assay, provide a powerful means of identifying cytotoxicity-associated gene expression changes. Electronic Publication     

Convergence to equilibrium in a genetic model with differential viability between the sexes

A single locus, diallelic selection model with female and male viability differences is studied. If the variables are ratios of allele frequencies in each sex, a 2-dimensional difference equation describes the model. Because of the strong monotonicity of the resulting map, every initial genotypic structure converges to an equilibrium structure assuming that no equilibrium has eigenvalues on the unit circle.Partially supported by funds provided by a Science and Education Grant to the USDA-Forest Service, Southeastern Forest Experiment Station, Population Genetics of Forest Trees Research Unit, Raleigh, USASupported by a grant from the Max Kade Foundation, New York, USA     

A gastric trichobezoar in a chimpanzee

A firm, mobile, oblong mass was discovered as an incidental finding in the stomach of a chimpanzee (Pan troglodytes) during routine surgery. It was removed and determined to be a trichobezoar.     

Adaptive variation of pelage color within and between species of the subterranean mole rat (Spalax ehrenbergi) in Israel

Summary Color notations of dorsal pelage were analyzed in 451 adult subterranean mole rats, comprising 19 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. In addition, the color notations of soil samples from the collection sites were measured. In an attempt to evaluate the degree of correlation between pelage color of mole rats and the local soil color, each color was compared both macro- and microgeographically. The macrogeographic comparisons were among populations of the 4 chromosomal species, and the microgeographic comparisons were among pairs of geographically neighboring subpopulations which occur under similar climatic conditions but differ in soil type and color. The results indicate that 1. no differences in pelage color notation exist between the sexes; 2. pelage of mole rats is generally characterized by an over-all grayish color, but its shades vary regionally and locally in accordance with varying soil color; 3. a positive correlation was found between pelage and local soil colors in the macrogeographic analysis and this correlation was verified in a microgeographic comparison; 4. specimens from populations of the northern chromosomal species (2n=52, 54) mainly inhabit terra rossa and basalt soils, respectively, with reddish brown tones, and they tend to have a more reddish shade, whereas animals from the central species (2n=58), which inhabits mainly dark soils including alluvial clays, terra rossa and brown rendzina and the souther species 2n=60, which occurs mainly in light soil types such as pale rendzina, sandy loams and loess, tend to have a more yellowish shade. The general appearance of specimens from 2n=58 was dark gray while that of 2n=60 specimens was light gray; 5. mole rats living in xeric environments (particularly 2n=60, but also 2n=54) are lighter than those which live in mesic environments (2n=52, 58). The results support the conclusion that pelage color of strictly subterranean mole rats is subject to selection pressures of overground predation of disharmonious types with their background soil color. The possibility that the pelage color variation and patterns also contributes to better thermoregulation while mole rats are above ground is discussed.     

Absence of subtransition in racemic dipalmitoylphosphatidylcholine vesicles

dl-Dipalmitoylphosphatidylcholine multilamellar vesicle suspensions were examined by the method of differential scanning calorimetry. A lack of the subtransition at 18°C was established. Such a subtransition is characteristic for l-dipalmitoylphosphatidylcholine suspensions. This lack is supposed to be the result of the impossibility of the racemic phospholipid mixture to form the low-temperature crystal structure L_c.     

小鼠巨核系祖细胞增殖,分化特性的研究

小鼠骨髓细胞经7d培养后进行细胞形态学观察,可见不同发育阶段的巨核细胞及不同大小的巨核细胞集落。通过计数每个集落中的细胞数,可确定相应祖细胞的有丝分裂能力。结果表明,具有不同有丝分裂能力的祖细胞的体外增殖动力学有所不同。祖细胞的数量与其有丝分裂次数呈负相关(r=-0.986)。进行0、1、2和3次有丝分裂的祖细胞的阿糖胞苷自杀率分别为48.9,58.7,48.0和41.2％;放射敏感性的D_O值(Gy)分别为1.71,1.24,1.03和0.77,D_O值的大小与有丝分裂次数呈负相关(r=-0.958)。经3Gy全身照射后CFU-Meg与CFU-GM的恢复动态过程具有不同特点。     

我国十省(市)十字花科蔬菜芜菁花叶病毒(TuMV)株系分化研究 Ⅰ.用Green氏方法划分株系

Provvidenti,R.(1980)和Green,S.K.(1985)先后用同一套鉴别寄主谱,研究了美国和我国台湾省的TuMV株系分化情况。本文用Green的方法,对由十省(市)7,982份病样中筛选出的19个TuMV主流分离物,在同一条件下进行了鉴定。结果表明,属于C_1株系的有黑_3分离物;属于C_4株系的有京_2、京_3、冀_2、宁_1(南京)、粤_1和川_1共6个分离物;属于C_5株系的有黑_1、辽_1、京_1、冀_1、沪_1、鲁_1、鲁_2共7个分离物。未检出C_2和C_3株系。黑_2、沪_2、宁_2和秦_1(陕西)共4个性状相近的分离物和冀_3分离物尚不能按Green的标准归类,暂分别定为C_(3-2)和C_6株系。此外,对Green氏方法应用于我国十字花科蔬菜TuMV株系分化研究中存在的问题作了讨论。