4个群体鲢mtDNA D-loop的PCR-RFLP分析

采用PCR技术扩增了湖北监利、江西瑞昌、湖南长沙3个长江野生群体和天津宁河1个人工繁殖群体(已繁殖6代)共158尾鲢(Hypophthalmichthys molitrix)mtDNA D-loop区段,并用14种核酸内切限制酶对扩增片段进行酶切。结果显示:所有试验鱼均扩增出约1.6 kb的DNA片段,10种限制酶有酶切位点,共检测出16种单倍型,以单倍型Ⅰ为主,在各群体中所占比例为57.5%~90.0%。鲢4个群体的单倍型多样性指数、核苷酸多样性指数为0.1885~0.6526和0.001182~0.007570。瑞昌群体与监利群体的Rogers遗传距最小,为0.1250;监利群体与宁河群体的Rogers遗传距最大,为0.2693。χ2检验结果显示4个群体间的遗传差异显著(P<0.01)。在4个群体中,宁河人工繁殖群体的单倍型多样性指数、核苷酸多样性指数均最高,并且HinfⅠ的C酶切类型为宁河群体所特有,达20.0%。     

Genetic population evaluation of two closely related flatfish species, the rare barfin flounder and spotted halibut, along the Japanese coast

ABSTRACT:   Barfin flounder and spotted halibut have been selected as target species for stock enhancement in Japan. Understanding the genetic condition of the wild stock is a principal requirement in any stock enhancement program. The genetic variability of barfin flounder and spotted halibut, and the population structure of spotted halibut were evaluated using microsatellite DNA markers (msDNA) and the control region of the mitocondrial DNA (mtDNA). Barfin flounder and spotted halibut showed high genetic variability at the msDNA level. Barfin flounder A was 16.7 and H _e was 0.860; spotted halibut A _n ranged from 7.7 to 10.2 and H _e ranged from 0.710 to 0.774. At the mtDNA level, high haplotype ( h  = 0.922) and low nucleotide (π = 0.002) diversities were observed for barfin flounder; however, low haplotype and nucleotide diversities ( h  = 0.603–0.620 and π = 0.001–0.002), and very low haplotype and nucleotide diversities ( h  = 0.193 and π = 0.0003) were observed for spotted halibut in the north and south locations, respectively. Slight genetic differentiation among spotted halibut sampling locations was observed from the msDNA. MtDNA analyses showed genetic differentiation between north and south locations, but not within them. The designation of north-specific and south-specific management units in the future stock enhancement activities of spotted halibut is recommended.     

Progression of the dose-related effects of estrogenic endocrine disruptors, an important factor in declining fertility, differs between the hypothalamo-pituitary axis and reproductive organs of male mice

For the purpose of investigation of working mechanisms in endocrine disruptors, we evaluated the dose-related effects of fetal and/or neonatal exposure to an estrogenic compound on the male reproductive organs in adult mice, particularly with respect to gene expression of steroidogenic acute regulatory protein (StAR). The pregnant ICR mice were given subcutaneous injections of 10 micro g/day/animal of diethylstilbestrol (DES) to subject the fetal mice to in utero exposure (IUE). Subsequently, the newborn male mice were subjected to neonatal exposure (NE) by treatment with vehicle or 0.1-10 micro g/day/animal of DES. Fertility rates of each group were as follows: control, 100%; IUE only, 60%; IUE+NE 0.1 micro g, 25%; IUE+NE 1 micro g, 0%; IUE+NE 10 micro g, 0%. In general histology, germ cell layers in the seminiferous tubules were thinned in the group of IUE+NE 10 micro g. Hypoplasia of the Leydig cells, in which the staining intensity of eosin was diminished, was also observed in the groups of IUE+NE 0.1-10 micro g. The androgen receptor (AR) and estrogen receptor alpha (ERalpha) immunoexpression in the Leydig cells of IUE+NE 1-10 micro g was slightly lower than that in the controls. Long-term dysfunction of the hypothalamo-pituitary-testicular axis, including sustained hypoproduction of gonadotropin and testosterone, and altered expressions of steroid hormone receptors and StAR genes were observed. The hypothalamo-pituitary control of gonadotropin secretion may be affected by the smaller doses of estrogenic agents than the reproductive organs. Furthermore, the fertility rate in the male mice exposed to this estrogenic agent was closely correlated with the testosterone levels, and even more so with the rate-limiting factor of steroidogenesis, StAR. This finding suggests that endocrine disruptors have an important pronounced effect on StAR gene expression.