Carbon Balance of a Mannitol Fermentation and the Biosynthetic Pathway

The carbon balance was determined for a fermentation in which mannitol is produced from glucose by an Aspergillus species. The products found were: cells (17% of carbon input), CO(2) (26%), mannitol (35%), glycerol (10%), erythritol (2.5%), glycogen (1%), and unidentified compounds (8%). Thus, 92% of the carbon input was accounted for. Cell-free enzyme studies showed that mannitol was synthesized via the reduction of fructose-6-phosphate and not by the direct reduction of fructose. If the cell yield from glucose was assumed to be 50% and the theoretical conversion efficiency from glucose to polyols was 90%, as calculated from the energy balance, then 34% of the glucose carbon was used for growth and 53% was used for polyol formation.     

脊髓灰质炎病毒中Ⅰ9株基因组克隆及其部分结构分析

以脊髓灰质炎病毒RNA为模板,反转录合成了长链ds-cDNA。将合成的脊灰病毒中I9株ds—cDNA片段重组到质粒pAT153上,获得了约占脊灰病毒中I9基因组95％以上的cDNA克隆。对克隆的中I9cDNA部分片段作了限制性内切酶图谱分析和部分核酸的序列分析,发现脊灰病毒中I9部分核酸顺序有所改变。     

三乙醇胺基强碱性聚苯乙烯树脂共价固定胰酶的研究

用多孔强碱型三乙醇胺基聚苯乙烯阴离子交换树脂做为载体,用CNBr与载体上的多羟基作用共价偶联了胰酶。红外光谱表明:其共价偶联反应机理与用CNBr活化多糖类载体并接酶的机理相类似。最适偶联条件研究表明:CNBr用量增多,酶蛋白载量增加。但比活下降。偶联pH为10时,固定化酶有适宜的载量和较高的比活。由于胰酶水解蛋白反应释放出H~+质子,这些质子在载体内积累,使微环境内H~+质子浓度增加,进而使得固定化胰酶的pH—活性曲线在pH9～11范围内未出现下降。在变温和60℃恒温下对固定化酶的热稳定性测试表明:固相酶的热稳定性比天然酶的热稳定性有所提高。     

Influence of SQ 30741 on thromboxane receptor-mediated responses in the feline pulmonary vascular bed.

The effects of SQ 30741, a thromboxane A2 (TxA2) receptor blocking agent, on responses to the TxA2 mimic, U-46619, were investigated in the pulmonary vascular bed of the intact-chest cat under constant-flow conditions. The administration of SQ 30741 in doses of 1-2 mg/kg iv markedly reduced vasoconstrictor responses to U-46619 without altering responses to prostaglandin (PG) F2 alpha or PGD2 and serotonin. SQ 30741 had no significant effect on mean vascular pressures in the cat, and the dose-response curve for U-46619 was shifted to the right in a parallel manner with a similar apparent maximal response. In addition to not altering responses to PGF2 alpha, PGD2 alpha, or serotonin, SQ 30741 (2 mg/kg iv) was without significant effect on pulmonary vasoconstrictor responses to the PGD2 metabolite 9 alpha, 11 beta-PGF2, norepinephrine, angiotensin II, BAY K 8644, endothelin 1, or endothelin 2. Although responses to vasoconstrictor agents, which act through a variety of mechanisms, were not altered, responses to the PG and TxA2 precursor, arachidonic acid, were reduced significantly. The duration of the TxA2 receptor blockade was approximately 30 and 75 min at the 1- and 2-mg/kg iv doses of the antagonist, respectively. The present data show that SQ 30741 selectively blocks TxA2 receptor-mediated responses in a competitive and reversible manner in the pulmonary vascular bed. These data suggest that responses to arachidonic acid are due in large part to the formation of TxA2 and that discrete TxA2 receptors unrelated to receptors activated by PGD2 or PGF2 alpha are most likely located in resistance vessel elements in the feline pulmonary vascular bed.     

贵州省赤水县桫椤调查初报

国家一级重点保护植物桫椤,目前世界上少数国家尚存,国内除华南、西南地区及台湾等少数省份外亦不多见。其中贵州省赤水县桫椤不仅面积广,且数量多,生长旺。据不完全统计,全县35个乡中,有20个乡有分布,面积     

高胆固醇高脂肪膳食对家兔β-VLDL组成及其与巨噬细胞相互作用的影响的初步研究

给家兔喂以1％胆固醇及10％菜油(A组)或猪油(B组)50多天后A组血胆固醇水平(824.2±265.1mg/dl)明显低于B组(1666±693.8mg/dl);A组甘油三酯水平(51.9±19.1mg/dl)亦低于B组(104±40.2mg/dl)。二组家兔的β—VLDL的脂类组成无差别,但A组β—VLDL的apoE高于B组,分别为45.2％及37.5％。高分子量apoB(apoB_h)为33.6％,低于B组β-VLDL(47.3％)。A组β-VLDL促进小鼠腹腔巨噬细胞胆固醇堆积的程度大于B组,可能与apoE含量高有关。我们认为多不饱和脂酸减轻动脉粥样硬化(As)的作用不在于改变脂蛋白构成后阻碍泡沫细胞的形成而是促进β—VLDL从体内清除。     

Molecular diversity of L-type calcium channels. Evidence for alternative splicing of the transcripts of three non-allelic genes

The diversity of L-type calcium channels was probed using the polymerase chain reaction and primers based on regions conserved in the L-type skeletal muscle (CaCh 1) and cardiac calcium channels (CaCh 2). Related sequences were amplified from human heart, hamster heart, rabbit heart, mouse ovary, mouse BC3H1 cells, and hamster insulin-secreting (HIT) cells. Sequencing of various clones revealed the presence of alternate splicing in gene products coding for CaCh 1, CaCh 2, and a related calcium channel. This related gene product, which we refer to as neuroendocrine or CaCh 3, is expressed in brain and endocrine cells. The diverse products can be explained by the use of alternate exons of equal size, which account for changes in amino acid composition, in combination with an alternate splice acceptor site or an exon skipping event, which produces channels of variable length. Four variants were defined for the gene 3 product, subtypes 3a, 3b, 3c, and 3d that differed in both the sequence of the third membrane spanning segment of the fourth repeat unit (IVS3) and in the size of the linker between this and the fourth membrane spanning segment (IVS4). Three CaCh 2 variants were cloned, subtypes 2a, 2c, and 2d, that are homologous to the a, c, and d variants of CaCh 3. For the skeletal muscle calcium channel only two variants were isolated. They are homologous to those of the a and c subtypes of CaCh 2 or 3, in that they differ only in the size of the IVS3 to IVS4 linker. These results demonstrate that calcium channel diversity is created by both the expression of distinct genes and the alternate splicing of these genes.     

Structure and assembly of turnip crinkle virus. VI. Identification of coat protein binding sites on the RNA

Structural studies of turnip crinkle virus have been extended to include the identification of high-affinity coat protein binding sites on the RNA genome. Virus was dissociated at elevated pH and ionic strength, and a ribonucleoprotein complex (rp-complex) was isolated by chromatography on Sephacryl S-200. Genomic RNA fragments in the rp-complex, resistant to RNase A and RNase T1 digestion and associated with tightly bound coat protein subunits, were isolated using coat-protein-specific antibodies. The identity of the protected fragments was determined by direct RNA sequencing. These approaches allowed us to study the specific RNA-protein interactions in the rp-complex obtained from dissociated virus particles. The location of one protected fragment downstream from the amber terminator codon in the first and largest of the three viral open reading frames suggests that the coat protein may play a role in the regulation of the expression of the polymerase gene. We have also identified an additional cluster of T1-protected fragments in the region of the coat protein gene that may represent further high-affinity sites involved in assembly recognition.