A Tripolar Spindle Formed at Meiosis I Assures the Retention of the Original Ploidy in the Gynogenetic Triploid Crucian Carp, Ginbuna Carassius auratus langsdorfii

A triploid crucian carp, ginbuna ( Carassius auratus langsdorfii ), reproduces by gynogenesis, in which sperm of diploid ginbuna or of other species triggers the development of the triploid eggs, but a male genome makes no contribution to the zygotic genome. Gynogenesis is maintained by two mechanisms: exclusion of male genome during fertilization and retention of somatic ploidy levels during oogenesis. We examined the mechanisms responsible for producing unreduced eggs. Microfluorometry with a DNA staining dye showed that DNA content in the ginbuna oocytes was not reduced in half during meiosis I. Cytological observations revealed that a tripolar spindle was formed at meiosis I and the first polar body was not extruded, whereas an ordinary bipolar spindle was formed and the second polar body was extruded at meiosis II. Activity of histone H1 kinase (as an indicator of maturation-promoting factor) decreased transiently between meiosis I and II, strongly suggesting a "normal" meiotic cycle progression in the ginbuna oocytes. These results have indicated that in the gynogenetic ginbuna the somatic ploidy levels are maintained by inhibiting the first polar body extrusion via the formation of the tripolar spindle at meiosis I.     

A Mutational Analysis of Killer Toxin Resistance in Saccharomyces Cerevisiae Identifies New Genes Involved in Cell Wall (1 -> 6)-β-Glucan Synthesis

Recessive mutations leading to killer resistance identify the KRE9, KRE10 and KRE11 genes. Mutations in both the KRE9 and KRE11 genes lead to reduced levels of (1 -> 6)-β-glucan in the yeast cell wall. The KRE11 gene encodes a putative 63-kD cytoplasmic protein, and disruption of the KRE11 locus leads to a 50% reduced level of cell wall (1 -> 6)-glucan. Structural analysis of the (1 -> 6)-β-glucan remaining in a kre11 mutant indicates a polymer smaller in size than wild type, but containing a similar proportion of (1 -> 6)- and (1 -> 3)-linkages. Genetic interactions among cells harboring mutations at the KRE11, KRE6 and KRE1 loci indicate lethality of kre11 kre6 double mutants and that kre11 is epistatic to kre1, with both gene products required to produce the mature glucan polymer at wild-type levels. Analysis of these KRE genes should extend knowledge of the β-glucan biosynthetic pathway, and of cell wall synthesis in yeast.     

Induction and Turnover of Nitrate Reductase in Zea mays (Influence of NO3-)

Zea mays (cv W64A x W182E) was used to investigate the induction and turnover of nitrate reductase (NR). In our system, 5 or 10 mM KNO3 gave the best growth over a 6-d growing period. With these NO3- levels, NR reached steady-state levels after 24 h. For the turnover experiments, the seedlings were transferred to a NO3--free medium after a 24-h induction. Shoot NR was less sensitive to the removal of NO3- than root NR, which declined almost as soon as NO3- was removed when the seedlings were induced with 5 or 10 mM NO3-. With 1 mM NO3-, however, removal of NO3- from medium resulted in declines in both NR activity and NO3- in shoot and root. Although there was a delay in the degradation of NR protein relative to the loss of NR activity, this protein was not reactivated when NO3- was resupplied. These results indicate that NO3- regulates NR by influencing the de novo synthesis of the NR protein and not by a reversible activation-inactivation of that protein.     

环境因子对荒漠沙蜥种群密度影响的研究

本文研究人类改造荒漠的活动,植被,潜在的可利用的食物资源,竞争种的密度,土壤理化性质等坏境因子对荒漠沙蜥种群密度的影响。结果说明：人类的活动对沙蜥种群密度没有显著影响;决定沙蜥种群密度的主导因子是潜在的可利用的食物资源,植被,土壤含水量,竞争种的密度。这些因子的任何改变都能改变沙蜥的种群密度,均具有调节种群的作用。     

复合四倍体异育银鲫个体间遗传异质性的研究

用聚丙烯酰胺梯度凝胶电泳,分析比较了４个不同的银鲫雌核发育系,红鲤和复合四倍体异育银鲫鳍的５种不同的同工酶及蛋白表型的差异,表明复合四倍体异育银鲫表型上的差异主要是来自银鲫种内的遗传差异（不同的雌核发育系）。来源于同一个银鲫雌核发育系的复合四倍体异育银鲫,个体间的ＥＳＴ同工酶出现差异,并与父体红鲤的ＥＳＴ同工酶的多态性相关,因此,复合四倍体异育银鲫个体间的异质性也包含了来自父本的遗传影响。在所检测     

中国熊猴的分类整理

本文通过查看国内收藏的标本对M.assamensis进行了分类整理,认为M.a.coolidgei的亚种地位应予恢复,滇西地区熊猴可能代表一个新类群。通过t检验,滇南和越南等地与滇西北和西藏东南部等地熊猴头骨的某些特征表现出显著或极显著差异。作为区分coolidgei与assamensis的指标:coolidgei体型较小,肩背毛较短,35—75mm,背毛环纹略显或不明显,0—2环,体色更为灰暗;assamensis体型较大,肩背毛较长,85—110mm,背毛环纹明显,3—4环。     

鱼类远缘杂交正反交杂种胚胎发育差异的细胞遗传学分析

本文报道了鲤(Cyprinus carpio)×鲢(Hypophthalmichthys molitrix)、鲫(Carassiusauratus)×鲢、白鲫(Carassius auratus cuvieri)×鲢和鲢×鲤、鲢×鲫、鲢×白鲫的正反交试验。在鲤×鲢、鲫×鲢和白鲫×鲢3个正交组中,胚胎发育基本正常,尽管孵出的鱼苗绝大多数生命力弱,但孵化率都在50％左右;而在鲢×鲤、鲢×鲫和鲢×白鲫3个反交组中,胚胎发育均为畸形,不能孵化出苗。 胚胎发育细胞遗传学分析表明,鲤×鲢、鲫×鲢和白鲫×鲢的杂种胚胎几乎都是整倍体,而鲢×鲤、鲢×鲫×鲢×白鲫的杂种胚胎基本上是非整倍体,染色体数变化较大。这些正反交杂种胚胎发育的显著差异可能与其亲本物种间的基因组大小有关。文中还分析讨论了这些正反交差异与天然多倍体物种以及胚胎发育速度的相关性,认为天然多倍体物种可能具有一些不同于普通二倍体物种协调外源基因组的能力。     

笼养间蜂猴的繁殖

1989年至今,对15只（10,5）成年间蜂猴在人工饲养条件下的繁殖进行观察,结果为：1．间蜂猴的繁殖有明显的季节性;2．发情周期为49．67d(SD=1.25),在此期间,雌性外生殖器红肿,变大;雄性阴囊胀大;3．交配以背腹相贴为主;4．怀孕期为188d;5．哺乳期为108d(SD=4.12);6．均为一胎二仔。