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91.
92.
农田林网化地区近地面层廓线特征研究 总被引:2,自引:0,他引:2
大面积林网化地区近地面层大气的系留气球观测发现,近地面层大气的风、温、湿分为两层,即下边界层和扰动边界层,其厚度和廓线分布与理查逊数有关,在中性天气条件下均满足对数分布规律,边界层(特别是扰动边界层)内的摩擦速度U."与旷野对比点的摩擦速度U0增大1个数量级,而粗糙度Z"0增大2个数量级,甚至更大。 相似文献
93.
人红细胞NADH-细胞色素b5还原酶的分离纯化与鉴定黄长晖,朱忠勇,唐玉钗(南京军区福州总院全军医学检验中心实验科,福州350001)NADH细胞色素b5还原酶(Cytb5R,E.C.1.6.2.2.)是红细胞内催化高铁血红蛋白还原为血红蛋白的关键酶... 相似文献
94.
人血红细胞胞浆部分经(NH_4)_2SO_4沉淀,DEAE-纤维素(DE52)柱层析,磷酸纤维素柱层析(P11)得到部分纯化的PTPP,产率:5.7%,提纯1075倍。以(32) ̄P-Tyr-Poly(G_4:T)作底物,测得其表征Km约为0.5-0.8μmol/L,该酶的最适pH和最适温度分别为7.0-7.8及37-40℃。Zn ̄(2+)等二价金属离子及Na_3VO_4等酸根基团对其活性有明显的抑制作用;EDTA、甘油及DTT、巯基乙醇等则对其有强烈激活作用;而氟化物、酒石酸等对PTPP活性基本无影响。此外,某些蛋白质、氨基酸、核苷酸及抗肿瘤药物等对PTPP活性也都有不同程度的影响。特别是一些PKs及PPs在体外对PTPP活性也具有不同的作用。 相似文献
95.
通过测定红细胞胞浆及膜中的PTPP活性,发现人正常血红细胞中胞浆PTPP活性约占红细胞PTPP总活性的70-80%,膜中只有约20-30%的PTPP活性。很多因素诸如:病变、PH值、温度、离子强度、细胞贮存时间以及药物等,对PTPP在胞浆与膜中的分布有影响。可以推测:膜上的PTPP能通过某种机制解离下来,进入胞浆;相反的过程,胞浆中的PTPP也能通过某种机制与膜结合。这种偶联与去偶联的具体机制及其生理功能还有待进一步探索。 相似文献
96.
Zhuang XC Sun YZ Cui J Zhu JM Jiang C Xiang QL Li CS 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》1994,1(1):P61-P63
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. 相似文献
97.
Potassium (K+) contracture tension, measured in small bundles of rat soleus muscle fibers during maintained depolarization, increases to a peak value and then decays either to the baseline or to a pedestal level. We have tested the hypothesis that the rise and fall of tension are determined by independent activation and inactivation processes. If the “Independence” hypothesis is correct, tension during the decay of K+ contractures should equal tension predicted from the product of the activation and inactivation parameters determined from the same K+ contractures. Both the measured and predicted tensions decayed to a pedestal level that was increased in amplitude in the presence of perchlorate ions. However, the measured tensions in normal solutions and in the presence of perchlorate were three to five times smaller than the predicted tensions. This result indicates that the activation and inactivation of processes controlling the rise and decay of K+ contracture tension are not independent. 相似文献
98.
Thermodynamic, thermomechanical, and structural properties of a hydrated asymmetric phosphatidylcholine. 总被引:1,自引:1,他引:0 下载免费PDF全文
1-Behenyl-2-lauryl-sn-glycero-3-phosphocholine (22/12 PC) belongs to a unique group of phospholipids in which the molecule has one acyl chain almost twice as long as the other. The temperature-composition phase diagram for this lipid in the range of 25-65 degrees C, and 0 to 84.3% (w/w) water has been constructed by using the isoplethal method in the heating direction and x-ray diffraction for phase identification and structure characterization. At water contents between 10.3 and 34% (w/w) and at temperatures below 43 degrees C, a single mixed interdigitated lamellar gel phase (Lm beta, [symbol: see text]) of the type described by Hui et al. (1984. Biochemistry. 23:5570-5577) and McIntosh et al. (1984. Biochemistry. 23:4038-4044) was found. A second phase consisting of bulk aqueous solution coexists with the Lm beta phase at hydration levels above 34% (w/w) water in the temperature range between 25 and 43 degrees C. Above 43 degrees C, a partially interdigitated lamellar liquid crystalline (Lp alpha) phase ([symbol: see text]) is seen in the water concentration range extending from 0 to 84.3% (w/w). The pure Lp alpha phase is found below 43% (w/w) water, while coexistence of the Lp alpha phase and the bulk aqueous solution is observed above this water concentration which marks the hydration boundary. Interestingly, the latter boundary for both Lm beta and Lp alpha phases is nearly vertical in the temperature range studied. Furthermore, the lamellar chain-melting transition temperature appears to be relatively insensitive to hydration in the range 0-85% (w/w) water. We have confirmed the identify of the Lm beta phase by constructing a 5.7-A resolution electron density profile on oriented samples by the swelling method. Temperature-induced chain melting effects an increase in lipid bilayer thickness suggesting that the Lp alpha phase has chains packed in the partially as opposed to the mixed interdigitated configuration. Unlike the symmetric phosphatidylcholines a ripple (P beta') phase was not found as an intermediate between the low and high temperature lamellar phases of 22/12 PC. The specific volume of 22/12 PC is 940 (+/- 1) microliter/g and 946 (+/- 1) microliter/g in the hydrated lamellar gel state at 28 (+/- 2) and 40 (+/- 2) degrees C, respectively, from neutral buoyancy experiments. Based on measurements of the temperature dependence of the various lattice parameters of the different phases encountered in this study the corresponding lattice thermal expansion coefficients have been measured. These are discussed and their dependence on lipid hydration is reported. 相似文献
99.
复合四倍体异育银鲫个体间遗传异质性的研究 总被引:1,自引:0,他引:1
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 相似文献
100.
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 总被引:19,自引:0,他引:19
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。 相似文献