Studies on atrophic change of soleus muscle and its countermeasures in suspended rat

In the environment of microgravity, the disused atrophy of skeletal muscle, especially leg's muscle, would occur. The three purposes of this study were: 1. To observe the dynamic changes of disused atrophy of skeletal muscle under simulated weightlessness; 2. To approach the mechanism of disused atrophy of muscle; 3. To approach the countermeasures for reducing the degree of atrophy of muscle.     

Unbiased estimation of the rates of synonymous and nonsynonymous substitution

Summary The current convention in estimating the number of substitutions per synonymous site (K _S ) and per nonsynonymous site (K _A ) between two protein-coding genes is to count each twofold degenerate site as one-third synonymous and two-thirds nonsynonymous because one of the three possible changes at such a site is synonymous and the other two are nonsynonymous. This counting rule can considerably overestimate theK _S value because transitional mutations tend to occur more often than transversional mutations and because most transitional mutations at twofold degenerate sites are synonymous. A new method that gives unbiased estimates is proposed. An application of the new and the old method to 14 pairs of mouse and rat genes shows that the new method gives aK _S value very close to the number of substitutions per fourfold degenerate site whereas the old method gives a value 30% higher. Both methods give aK _A value close to the number of substitutions per nondegenerate site.     

Lymphocytes protect against and are not required for reovirus-induced myocarditis.

Many studies suggest that host lymphocytes are damaging, rather than protective, in virally induced myocarditis. We have investigated the role of lymphocyte-based immunity in murine myocarditis by using a myocarditic reovirus (reovirus serotype 3 8B), nonmyocarditic reoviruses, adoptive transfer experiments, and mice with severe combined immunodeficiency (SCID mice). Prior to infection, passive transfer of monoclonal antibodies specific for 8B capsid proteins protected neonatal mice against 8B-induced myocarditis, indicating that humoral immunity can protect against myocarditis. Some monoclonal antibodies acted by blocking viral spread to and/or replication in the heart. Passive transfer of reovirus-immune, but not naive, spleen cells prior to infection protected neonatal mice from 8B-induced myocarditis. Depletion of either CD4 or CD8 T cells resulted in increased viral titer in the heart but did not abrogate immune cell-mediated protection against myocardial injury. This shows that both CD4 and CD8 T cells can act independently to protect myocardial tissue from reovirus infection. In addition, reovirus 8B caused extensive myocarditis in SCID mice. This confirms a prior report (B. Sherry, F. J. Schoen, E. Wenske, and B. N. Fields, J. Virol. 63:4840-4849, 1989) that T cells are not required for reovirus-induced myocarditis and demonstrates for the first time that B cells are not required for reovirus-induced myocarditis. We used SCID mice and a panel of reoviruses to assess (i) the relationship between growth in the heart and myocardial damage and (ii) the possibility that nonmyocarditic reoviruses exhibit a myocarditic phenotype in the absence of functional lymphocytes. Growth in the heart was not the sole determinant of myocarditic potential in SCID mice. Although 8B induced myocarditis in SCID mice, no or minimal myocarditis was found in SCID mice infected with four reovirus strains previously shown (B. Sherry and B. N. Fields, J. Virol. 63:4850-4856, 1989) to be nonmyocarditic or poorly myocarditic in normal neonatal mice. We conclude that (i) humoral immunity and cellular immunity are protective against, and not required for, reovirus-induced myocarditis and (ii) the potential to induce cardiac damage is a property of the virus independent of lymphocyte-based immunity.     

A cellular cofactor facilitates efficient 3CD cleavage of the poliovirus P1 precursor.

The production of poliovirus capsid proteins from a capsid protein precursor (P1) is mediated by virus-encoded proteinase 3CD and involves a complicated set of proteinase-substrate interactions. In addition to substrate and enzymatic determinants required for this interaction, we describe a cellular cofactor, which facilitates 3CD recognition of the P1 precursor. Cellular cofactor activity is 3CD dependent and salt dependent. Our analysis shows that proteolytic cleavage of the P1 precursor at the VP0/VP3 cleavage site exhibits a greater dependency on the cellular cofactor than cleavage at the VP3/VP1 site. Such a greater dependency on cellular cofactor activity can be relieved (in part) by the substitution of an Ala residue for the Pro residue at the -4 position of the VP0/VP3 cleavage site. However, mutant viruses containing Pro-to-Ala substitutions at the -4 position of the VP0/VP3 site exhibit defects in viral growth.     

石炭纪一植物新属Reticalethopteris gen.nov.——对Palaeoweichselia yuani Sze的再研究

对北祁连山东段和鄂尔多斯西缘新材料的研究表明,甘肃景泰红水堡晚石炭世早期的杂羊齿属(Palaeoweichselia)与西欧的模式标本存在明显差异,遂另建-新属——Reticalethopteris gen.nov..新属与Neuralethopteris是脉延羊齿类植物中分别代表网状叶脉和羽状叶脉的一对姐妹属.     

贵州盘县新塘晚石炭世的四射珊瑚

文章通过贵州盘新塘原下二叠统下部紫松阶珊瑚化石的分析,将该地层划归上石炭统上部。描述上炭统威宁阶,过岩阶和紫松阶的四射珊瑚６属７种,其中５新种,通过对这些珊瑚的形态构造进行了剖析,略述了该地区在晚石炭世的环境特征。     

Elemental composition of secretory granules in pancreatic islets of Langerhans.

We have characterized, by electron probe microanalysis, rapidly frozen cultured rat islets at the level of individual secretory granules. Elemental analysis of thin, dried cryosections showed that beta granules could be distinguished by high Zn, Ca, and S, whereas non-beta (mainly alpha) granules contained elevated P and Mg. Although a single granule type predominated in a particular cell, some rebel granules were found in A cells that had the compositional fingerprint of B cell granules. Zn, which was found in millimolar concentrations in B cell granules, was considered a marker for the insulin storage complex. The data indicate that non-B islet cells in the adult pancreas may produce insulin-containing organelles and that, when glucagon and insulin are coexpressed, these hormones are packaged in separate granules.     

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。     

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。