Release of PGF(2alpha) during parturition and the postpartum period in the ewe

Peripheral plasma levels of 15-keto-13, 14-dihydro-PGF(2alpha) were determined from one week before parturition until five weeks postpartum in six ewes. Starting at approximately 1 nmol/l one week before parturition, the prostaglandin metabolite levels rose successively during the week preceding parturition and peaked at 70 to 125 nmol/l during parturition. During the first three days postpartum the concentrations of the 15-keto-13, 14-dihydro-PGF(2alpha) decreased to 0.5 to 1 nmol/l. These levels were maintained for three weeks and low levels of 50 to 100 pmol/l were reached around four weeks postpartum. The ewe, as well as other ruminants, has a sustained release of elevated concentrations of PGF(2alpha) postpartum. It seems likely that PGF(2alpha) plays a role in uterine involution.     

板栗枝插生根试验

促使枝插生根是板栗营养繁殖最有希望的方法之一,因其方法简便,同时又解决了由于板栗嫁接时常遇到的砧穗不亲和的问题。 试材为‘AU—Cropper’、‘AU—Homestead’和‘AU—Leader’三个板栗品种。插条采自植株成熟部位经修剪诱发的健壮副梢上抽生的春梢,剪取其顶部和基部枝条,长15—20厘米;此外,从植株未修剪的成熟部位,剪取当年生春梢(带有2—3厘米长的去年生枝)。插条上的叶片,仅留顶部2—3片,余者剪除,然后在近轴末端的     

New hybrids with d genome wheat relatives

The cytology of nine new D genome hybrids involving Triticum syriacum, Triticum ventricosum, Triticum cyclindricum, Triticum juvenale, Triticum crassum, Triticum tauschii and Triticum aestivum is described. The calculation of numerical values of the relative affinity and the patterns of chromosome pairing indicate that the D genome in T. syriacum and T. juvenale may have been substantially modified and that of T. crassum somewhat modified from that of the diploid progenitor, T. tauschii.     

Preparation and characterization of a soluble dextran alpha(1) proteinase inhibitor complex

Purified human alpha(1) proteinase inhibitor, a plasma glycoprotein with a molecular weight of 5.3 x 10(4) daltons and a major serine protease inhibitor has been covalently coupled to dextrans with molecular weights of 1.77 x 10(4) and 1.03 x 10(4) daltons. The coupled conjugates were soluble in aqueous medium and stable up to 6 months at +5 degrees C. Increased moles of dextran/mole protein ratio during coupling resulted in progressive decreases of inhibitory capacity, immunogenicity, and the association constant (k(assoc)) between the enzyme and the inhibitor. Compared to the native protein, the soluble conjugates showed improved stability at pH 3.0 and heat stability at 60 degrees C. At 60 degrees C, no loss of inhibitory capacity has been seen up to 60 min for the conjugates during which time the native protein lost greater than 90% of its inhibitory capacity. The presence of antioxidant catalase was needed to prevent oxidative degradation by hydrogen peroxide.     

Ease of removal of barnacles from various polymeric materials

The forces required to remove living, fully attached barnacles from the surface of a number of polymeric solids were measured. The forces were related to the surface energy components of the materials. The results indicate a positive correlation between polymer surface energy and force required for barnacle removal. The nonpolar component of the surface energy was more closely related to the removal force than the polar component, although the polar component is significant. Adherence to some composite materials was greater than was consistent with the correlation for noncomposites.     

Butanediol production by Aerobacter aerogenes NRRL B199: effects of initial substrate concentration and aeration agitation

Butanediol production by Aerobacter aerogenes NRRL B199 grown on glucose requires an optimal rate of aeration for the obtention of butanediol 2, 3. In the absence of air, Aerobacter aerogenes NRRL B199 growth and production are weak. Agitation-aeration is necessary for producing the biomass, but an excess of oxygen proves to be toxic with regard to metabolite production. Oxygen is a limiting substrate with regard to growth and an inhibitor with regard to the specific metabolite productivity. This observation is discussed from a kinetic stand point and in relation to the search for the optimum oxygen transfer coefficient (K(L)a), which is found to be in the range of 50-100h(-1). It has also been observed that K(L)a increases during the fermentation cycle. The initial substrate concentration effects the yield production of biomass and butanediol production. Low yields of butanediol are obtained at low initial sugar concentrations, but good yields of butanediol are obtained (0.45 g/g) at high concentrations of glucose (195 g/L). Carbon substrates and butanediol are inhibitors of cell growth while butanediol is not quite an inhibitor of the specific rate of butanediol production for the range of butanediol of 0-100 g/L.     

Kinetic properties of Na(+) -H(+) antiport in Escherichia coli membrane vesicles: Effects of imposed electrical potential, proton gradient, and internal pH

Modifications of the kinetic properties of the Escherichia coli (RA11) Na(+) - H(+) antiport system by imposed pH gradients (deltapH, interior alkaline) and membrane potential(delta(psi), interior negative) were studied by looking at the accelerating effects of deltapH and delta on downhill Na(+) efflux from membrane vesicles incubated at different external pHs. First,variations of the Na(+) efflux rate ( VNa) as a function of imposed delta pH appear to be strongly dependent on the external pH value.The individual VN, vs. deltapH relationships observed between pH 5.5 and pH 6.6 are all nonlinear and indicate the existence of a threshold deltapH above which V(Na) increases steeply as the deltapH magnitude increases; threshold deltapH values progressively decrease as the pH is raised from 5.5 to 6.6. In contrast, at or above neutrality, V(Na) acceleration is linearly related to deltapH amplitude. Strikingly, it is shown that the deltapH-dependent variations in the Na(+) efflux rate measured in vesicles incubated at different external pHs can be accounted for by variations of internal pH; the observed relationship suggests that a high internal H(+) concentration inhibits the Na(+) -H(+) antiport activity.This inhibition results from a drastic increase in the apparent K(m), of the Na(+) efflux reaction as the internal H(+) concentration increases. On the other hand, imposed Δ increases the Na(+) efflux rate linearly by a selective modification of the V(max) value of the Na(+) efflux. Together, these data indicate that the internal H(+) concentration controls the Na(+)-H(+) antiport activity and that the chemical and electrical proton gradients affect two different kinetic steps of the Na(+)-H(+) exchange reaction.     

甲型肝炎病毒对理化因子的稳定性

用放射免疫成斑法研究了甲型肝炎病毒FM-175株的理化稳定性和灭活条件,证明甲型肝炎病毒理化稳定性与其它肠道病毒相似,具有广范围的pH(2～10)稳定性;Mg~(++)和Ca可增强其热稳定性,不能抵抗冷冻干燥,但对热的抵抗力明显高于普通肠道病毒,可被紫外线迅速杀灭,也可被多种消毒剂如3～8％的甲醛液,50～90％的乙醇,2％的石炭酸及400ppm的有效氯等杀灭,但可抵抗0.1％甲醛液,2～5％的来苏儿及200ppm的有效氯1小时以上,本研究工作为甲型肝炎病毒的理化性状、保存及消毒条件等提供了实验数据。     

用于DNA或RNA去盐、去蛋白及浓缩的一种方便的新方法

一种新型方便的层析柱,NENSORB~(TM)20核酸纯化柱,已被发展起来,用于从DNA和RNA中除去蛋白、盐、非掺入的放射性核苷酸以及其它低分子量物质。NENSORB20柱的使用免去了酚/氯仿抽提及乙醇沉淀这样一些典型的低得率步骤,也可用于浓缩稀释的核酸溶液。NENSORB20柱已被用来(1)从缺口转译反应混合液中纯化标记的DNA;(2)从SP6RNA聚合酶反应液中纯化标记的RNA探针;(3)纯化有末端~(35)S或~(32)P标记的DNA或RNA;(4)纯化通过M13模板上的引物延伸反应制备出的单链DNA探针;及(5)从限制性酶消化液中纯化DNA片段。 与传统的阴离子交换方法不同,这里洗脱核酸的溶液不需含有盐。DNA和RNA收集在酒精/水溶液中;彻底干燥后,核酸可直接用于进一步的生化反应。在缺口转译、末端标记、克隆、杂交、SP6聚合酶反应、蛋白质反应以及其后的实验中,经NENSORB20柱纯化的DNA或RNA样品都显示出极好的生物学活性。从含有lng到20μg核酸和蛋白的体外反应液中可得到优质、量可重复的收集物(通常60～90％)。     

Mutants of Pachysolen tannophilus with Improved Production of Ethanol from d-Xylose

The conversion of d-xylose to ethanol by the yeast Pachysolen tannophilus is relatively inefficient in batch culture. The inefficiency has been attributed in part to concurrent utilization of ethanol in the presence of appreciable concentrations of d-xylose and to the formation of xylitol and other by-products. To increase the concentration of ethanol accumulated in batch cultures, UV-induced mutants of P. tannophilus were selected on the basis of diminished growth on ethanol. Eleven independent mutant loci that conferred the ethanol-defective phenotype were identified. Three led to a greater yield and volumetric rate of production of ethanol than the wild type. One also produced less xylitol and was characterized by a deficiency in activity for malate dehydrogenase.