FINE STRUCTURE OF LOACH OOCYTES DURING MATURATION IN VITRO

The morphological changes during in vitro maturation of Misgurnus anguillicaudatus oocyte are described. The process of oocyte maturation can be divided into three provisional stages based on morphological events. Fully-grown, immature oocytes are opaque yellowish-white. The morphological characteristics of their ooplasm are the existence of annulate lamellae, a mass of long mitochondria and an electron dense layer beneath the vitelline surface. Three hr after a 1 hr exposure to corticosterone, these structures disappear and the cortical ooplasm becomes semi-transparent. In this stage of the maturation process (Stage I), the germinal vesicle, without a nucleolus, moves toward the animal pole, and scattered cytoplasmic inclusions approach the vitelline surface. Six hr after exposure to the hormone (Stage II), the whole ooplasm becomes semi-transparent and large yolk platelets are seen in the animal pole region. Tubular endoplasmic reticula develop throughout the ooplasm and some cortical alveoli (CA) become aligned beneath the vitelline surface. Nine hr after exposure to the hormone (Stage III), the oocyte chorion separates from the follicle cells. Most CA align beneath the vitelline surface and cytoplasm accumulates in the cortical region of the animal hemisphere.     

Identification of genes showing differential expression profile associated with growth rate in skeletal muscle tissue of Landrace weanling pig

Suppression subtractive hybridization was used to identify genes showing differential expression profile associated with growth rate in skeletal muscle tissue of Landrace weanling pig. Two subtracted cDNA populations were generated from musculus longissimus muscle tissues of selected pigs with extreme expected breeding values at the age of 100 kg. Three upregulated genes (EEF1A2, TSG101 and TTN) and six downregulated genes (ATP5B, ATP5C1, COQ3, HADHA, MYH1 and MYH7) in pig with genetic propensity for higher growth rate were identified by sequence analysis of 12 differentially expressed clones selected by differential screening following the generation of the subtracted cDNA population. Real-time PCR analysis confirmed difference in expression profiles of the identified genes in musculus longissimus muscle tissues between the two Landrace weanling pig groups with divergent genetic propensity for growth rate. Further, differential expression of the identified genes except for the TTN was validated by Western blot analysis. Additionally, the eight genes other than the ATP5C1 co-localized with the same chromosomal positions as QTLs that have been previously identified for growth rate traits. Finally, the changes of expression predicted from gene function suggested association of upregulation of expression of the EEF1A2, TSG101 and TTN genes and downregulation of the ATP5B, ATP5C1, COQ3, HADHA, MYH1 and MYH7 gene expression with increased growth rate. The identified genes will provide an important insight in understanding of the molecular mechanism underlying growth rate in Landrace pig breed.     

Female dimorphism in Japanese diving beetle Dytiscus marginalis czerskii (Coleoptera: Dytiscidae) evidenced by mitochondrial gene sequence analysis

Three species of the Japanese diving beetle Dytiscus have been identified: D. dauricus Gebler, 1832; D. marginalis czerskii Zeitzev, 1953; and D. sharpi. At present, the latter consists of the subspecies D. sharpi sharpi Wehncke, 1875 and D. sharpi validus Régimbart, 1899 based on the comparative data of mitochondrial DNA cytochrome‐c oxidase I (COI) sequences. Many Dytiscus species have smooth and grooved elytra, which are female dimorphic traits. For many years it has been thought that Japanese D. marginalis czerskii has a single morph, that is, only grooved females, although there were some collecting reports of smooth females occurring at the foot of Mt. Chokaisan in Yamagata and Akita Prefectures. However, the population of smooth females (smooth population) has not yet been identified by DNA markers. To understand the species status of the smooth population, we sequenced 769 bp of COI of a male derived from a smooth mother insect and compared it with the sequence from a known grooved female. The sequences of 769 bp of the COI gene in the smooth population were identical to that in the grooved female, indicating that Japanese D. marginalis czerskii has female dimorphic traits.     

Identification and characterization of microsatellite markers derived from expressed sequence tags (ESTs) of radish (Raphanus satvius L.)

Radish, Raphanus satvius, is a very important commercial crop in the world, especially in East Asian countries. In this study, radish microsatellite markers have been developed for the first time from expressed sequence tags (ESTs). A total of 8 primer pairs were able to produce clear amplifications, respectively, which gave 2–5 polymorphic loci between 43 cultivars of Japanese radish. Observed and expected heterozygosity ranged from 0 to 0.4186, and from 0.1779 to 0.6205, respectively. Polymorphic information content ranged from 0.171 to 0.575. The eight simple sequence repeats were also polymorphic when tested by wild radish (Raphanus raphanistrum). Deviation from Hardy–Weinberg equilibrium was analysed in three populations, and no linkage disequilibrium was observed. It is anticipated that these newly developed microsatellite markers can advance further genomic analyses. This accomplishment may in turn accelerate and simplify radish breeding programs.     

酵母双杂交筛选锥虫早老素蛋白相互作用蛋白

目的筛选寻找锥虫早老素蛋白相互作用蛋白,以了解锥虫早老素蛋白功能。方法体外表达锥虫早老素蛋白片段,装入pGBKT7诱饵质粒,与随机肽库系统共转化酵母,筛选阳性克隆并测序,通过与基因库锥虫功能序列比较,推导可能的相互作用蛋白。结果获得108个阳性克隆,对其中50个进行了序列测定和比较,获得最有可能的4个候选基因,分别为：丝/苏氨酸性磷酸酶2b催化亚基A2;钙激活蛋白,含锚蛋白重复序列蛋白以及一个具有与APP跨膜区结合位点特征序列的功能未知蛋白。结论成功利用随机肽库酵母双杂交系统筛选锥虫早老素蛋白相互作用基因,其相互作用仍有待进一步确认。     

Cytoplasmic control of mitosis in true slime mold, Physarum polycephalum

To resolve the problem of whether mitosis is controlled by anuclear or cytoplasmic stimulus, plasmodia from various periodsof the mitotic cycle were fused with one another. Mitosis inthe fused plasmodiura occurred about midway between mitosesof the donors. Treatment with cyclohcximide during the G₂-period.delayed the next mitosis for a period equal to the time of treatment. (Received March 2, 1971; )