MALE HYBRID STERILITY IN DROSOPHILA: INTERACTIONS BETWEEN AUTOSOMES AND SEX CHROMOSOMES IN CROSSES OF D. MOJAVENSIS AND D. ARIZONENSIS

By backcrossing hybrids from the cross Drosophila mojavensis female × Drosophila arizonensis male to both parental species we show that several interspecific combinations of autosomes with one or the other sex chromosome (X or Y) result in sperm abnormalities. Two of these incompatibilities will cause the same type of nonreciprocal F₁ male sterility that is observed in this pair of species, but the possibility of an additional incompatibility that would have the same result, e.g., an incompatibility between the mojavensis Y and the arizonensis X chromosomes, cannot be excluded. The incompatibility between the arizonensis Y chromosome and the mojavensis fourth chromosome found to occur for all tested populations of mojavensis race B (Vigneault and Zouros, 1986) is shown also to occur for race A of this species. We further show that a dominance relationship exists between heterospecific homologous autosomes in their interactions with the sex chromosomes and that the direction of the dominance depends on whether the sex chromosome is the X or the Y. The present role of these incompatibilities in preventing gene flow between the two species may be minor, but their genetic basis and mode of action may provide useful insights about the genetic events that have played a significant role in earlier stages of speciation.     

CYTOGEOGRAPHIC STUDIES IN DICENTRA. I. DICENTRA FORMOSA AND D. NEVADENSIS

Dicentra formosa (Haw.) Walp. is morphologically the most variable of the nine North American species in the genus. It constitutes a complex of rhizomatous perennials distributed throughout mountainous regions of the Pacific States. Dicentra nevadensis Eastw. is confined to high elevations in Tulare County, California. Two chromosomal races of Dicentra formosa exist. A tetraploid race, with n = 16, appears to be confined to coastal mountains and valleys, while a diploid race, with n = 8, is distributed along inland mountain ranges, except in Josephine County, Oregon, where the two races could be sympatric. Morphological associations with ploidy level occur, but they appear to be inconstant.     

CRITERIA OF FEMALE MATE CHOICE IN DROSOPHILA LITTORALIS,D. MONTANA,AND D. EZOANA

We examined sexual selection by Drosophila littoralis, D. montana, and D. ezoana females on male courtship sounds to determine whether the females use absolute or relative criteria when choosing their mates. Behavior of the females was observed, when they were courted by a single male producing normal sounds, or by a single wing-manipulated male producing abnormal sounds; and when they were courted by one or both of these males in a choice situation. The females usually accepted short-winged (but not wingless) males producing abnormal sounds, if they had no alternatives. However, if they heard the sound produced by a normal male, they rejected the deficient male. Drosophila littoralis and D. ezoana females selected between two wing-manipulated males with different wing areas. Our results suggest that the females choose their mates on the basis of relative criteria if the signals emitted by the courting males are within the range of acceptable cues.     

POLLEN AND TAPETUM DEVELOPMENT IN DESMODIUM GLUTINOSUM AND D. ILLINOENSE (PAPILIONOIDEAE; LEGUMINOSAE)

Each of the four microsporangia has three or four wall layers, a uninucleate tapetum of various cell shapes with nuclei that remain in prophase, and 12-24 pollen mother cells (PMCs). A sterile transverse septum sometimes bisects the microsporangium. PMCs secrete callose but not uniformly, and contact among them continues through meiosis. Simultaneous cytokinesis by furrowing isolates each microspore in callose, which later disperses. The separated microspores become vacuolate, undergo mitosis to become pollen, and later become filled with food reserves. Endothecial wall thickening and tapetal dissolution occur after pollen engorgement. Calcium oxalate crystals form in tapetal cells during the sporogenous stage, reach maximum size during early meiosis, and remain prominent until tapetal dissolution.     

FURTHER STUDIES IN THE GENUS DRYOPTERIS: THE ORIGIN OF D. CLINTONIANA,D. CELSA AND RELATED TAXA

Walker , S. (Liverpool Univ., England.) Further studies in the genus Dryopteris: the origin of D. clintoniana, D. celsa and related taxa. Amer. Jour. Bot. 49(5): 497–503. Illus. 1962.—Cytogenetic studies of 5 Dryopteris species, from North America, together with wild and synthesized hybrids between some of them, show that D. clintoniana and D. celsa are allohexaploid and allotetraploid respectively. Cytological and morphological evidence points to D. cristata and D. goldiana being parental to D. clintoniana, whilst D. goldiana and D. ludoviciana are parental to D. celsa. The taxon D. X australis is triploid and has been synthesized; it is the backcross between D. celsa and D. ludoviciana.     

THE STRUCTURE AND DISTRIBUTION OF PERIPHERAL CILIATED RECEPTORS IN THE BIVALVE MOLLUSCS DONAX SERRA AND D. SORDIDUS

The siphons and mantle edge of Donax serra and D. sordidus possesstwo types of ciliated sensory receptor. Type 1 has > 7 ciliawith an exposed length of 0.7–2.4 µm. Type II hasfewer cilia (2–5) which are 2–6 µm long. Athird type (Type III) described from the tips of the tentaclesof the siphon and mantle edge of D. sordidus, possesses twotufts of cilia which are 12 µm long. All three receptortypes appear to be primary receptors. Estimates of abundanceshow that receptors are most numerous on the tips of the siphontentacles (9.75 x 10³. mm^–2), and it is suggested thatthese receptors function as chemoreceptors. (Received 11 May 1983;     

THE DISTRIBUTION OF GROUP D STREPTOCOCCI IN CATTLE AND SHEEP

Numbers and types of Lancefield group D streptococci have been determined in samples from the colons of 17 cattle and 9 sheep. Mean total streptococcal counts of 8 × 10⁴/g in cattle and 2 × 10⁶/g in sheep were obtained. Streptococcus bovis was found in every sample and was the predominant species in 15 of the cattle and 6 of the sheep. Other group D streptococci ( Strep. faecalis, Strep. faecium and Strep. durans ) were rare in cattle, but in sheep they formed a significant proportion of the population. Of 60 Strep. faecium, Strep. durans and related strains, 51 fermented raffinose. Many of the strains of Strep. faecium were also atypical in that they fermented sorbitol and appreciably reduced tetrazolium in broth at pH 6.0.
Strep. bovis remained the predominant streptococcus in faeces samples from 4 dairy cows when they were tested again after an interval of 17 and 18 months.     

天然常绿阔叶异龄幼林胸径的Weibull分布及动态预测

 常绿阔叶林是我国亚热带东部地区的地带性自然植被。本次在浙江西北部研究的44块常绿阔叶林样地的主要树种是青冈(Cyclobalanopsis glauca)、石栎(Lithocarpus glaber)、甜槠(Castanopsis eyrei)、木荷(Schima superba)和苦槠(Castanopsis sclerophylla)等。Weibull函数能够较灵活地用来表达常绿阔叶异龄林的这种具有不同偏度和峭度变化的直径分布。随着林分平均胸径(D)的增大,常绿阔叶异龄林的胸径分布表现出由指数形转向倒J形至正态形。偏度由正偏趋于负偏．峭度逐渐变小．多数相应增大的动态分布规律。采用参数预估法研究建立了以D为自变量的天然常绿阔叶异龄林直径分布动态模型及其预测数表．可供合理经营等参考使用。     

p16和cyclinD1在乳腺导管非典型增生癌变过程中的表达

目的 探讨乳腺导管非典型增生癌变过程中p16和cyclinD1的变化及其相互关系。方法 应用免疫组织化学方法检溯p16、cyclin成在乳腺各组病变中的蛋白表达情况。结果 乳腺导管单纯性增生、非典型增生组织中p16蛋白表达率明显高于乳腺癌组织,差异有显性。cyclinD1在中,重度非典型增生组表达最为明显,且与乳腺导管单纯性增生组及轻度非典型增生组比较,差异均有显性。p16、cyclinD1蛋白在乳腺各组病变中表达呈负相关关系。结论 p16、cyclinDl在乳腺增生性病变中呈现不同程度表达,其表达强度在一定程度上与细胞的恶性倾向有关,检测其表达水平可作为乳腺导管非典型增生组织恶性转化的一个客观检测指标。其中,cyclinD1蛋白可能是乳腺癌发生过程中的早期分子事件,可作为临床早期发现乳腺癌的免疫学指标。