不同月龄婴儿接种DTP后血清中百日咳抗体水平的观测

本文对比观察了２１３例２月龄、３月龄婴儿接种ＤＴＰ后百日咳抗体水平的变化,探讨了母传抗体对免后抗体增长的影响。结果表明２月龄、３月龄婴儿ＤＴＰ免疫后１个月和３个月血清中百日咳抗体达保护水平的百分率无显著性差异（ｘ￣２＝０．０３６,ｐ＞０．９;ｘ￣２＝０．３２７,ｐ＞０．５）,免后１个月抗体ＧＭＴ无显著性差异（ｔ＝０．１７,ｐ＞０．５）,免后３个月抗体ＧＭＴ３月龄组高于２月龄组（ｔ＝２．２２,ｐ＜０．０５）。我们还发现免前抗体水平与免后１个月ＧＭＴ虽有负相关（ｒ＝—０,７５４）的倾向,但总体上对抑制免后抗体应答不明显,因而建议将儿童ＤＴＰ基础免疫的起始月龄提前至２月龄进行。     

紫外激光消融过程的等效模型研究

本文引用等效模型,对激光消融过程进行了推导与计算,和实验结果比较表明,所得公式与实验结果能较好相符,可用于描述紫外激光消融过程。     

南瓜果肉色素的提取及稳定性的研究

本文研究了从南瓜果肉中提取色素的方法,并对它的光、热、酸、碱稳定性进行了研究,发现其性质较稳定,且原料来源广泛,提取工艺简单,着色效果好,是食品、医药、化妆品等领域的理想添加剂。     

温度对黄粉虫成虫繁殖的影响

黄粉虫是多种小型经济动物的常用优良饵料,本试验在20.1℃,24.0℃、28.5℃、31.7℃和36.5五种恒温下饲养该成虫结果,成虫寿命平均分别为63.0、54.2、38.8、38.0和26.1天;每雌平均产卵量则分别为200.3、207.3、122.3、115.8和81.2粒,成虫平均生产1g卵消耗麸皮量分别为2.66、2.00、2.19、2.14和4.15g。结果说明人工繁殖黄粉虫的成虫期温度以24℃为最适宜。     

Kinetics of the Competitive Degradation of Deoxyribose and Other Molecules by Hydroxyl Radicals Produced by the Fenton Reaction in the Presence of Ascorbic Acid

The competition method in which the Fenton reaction is employed as an OH radical generator and deoxyribose as a detecting molecule, has been used to determine the rate constants for reactions of the OH radical with its scavengers. Nonlinear competition plots were obtained for those scavengers which reacted with the Fenton reagents (Fe²⁺ or H₂O₂). Ascorbic acid is believed to overcome this problem. We have investigated the kinetics of deoxyribose degradation by -OH radicals generated by the Fenton reaction in the presence of ascorbic acid, and observed that the inclusion of ascorbic acid in the Fenton system greatly increased the rate of OH radical generation. As a result, the interaction between some scavengers and the Fenton reagents became negligeable and linear competition plots of A7A vs scavenger concentrations were obtained. The effects of experimental conditions such as, the concentrations of ascorbic acid, deoxyribose, H₂O₂ and Fe²⁺-EDTA, the EDTA/Fe²⁺ ratio as well as the incubation time, on the deoxyribose degradation and the determination of the rate constant for mercaptoethanol chosen as a reference compound were studied. The small standard error, (6.76± 0.21) ±' 10⁹M^-1s^-1 observed for the rate constant values for mercaptoethanol determined under 13 different experimental conditions, indicates the latter did not influence the rate constant determination. This is in fact assured by introducing a term, k_x, into the kinetic equation. This term represents the rate of-OH reactions with other reagents such as ascorbic acid, Fe²⁺-EDTA, H₂O₂ etc. The agreement of the rate constants obtained in this work with that determined by pulse radiolysis techniques for cysteine, thiourea and many other scavengers, suggests that this simple competition method is applicable to a wide range of compounds, including those which react with the Fenton reagents and those whose solubility in water is low.     

几种细胞分裂素诱导石竹外植体直接再分化成花芽的机理

用ＭＳ＋２,４－Ｄ０．１ｍｇ／Ｌ为基本培养基,分别附加不同浓度的ＺＴ、ＢＡ和ＫＴ,对石竹的叶片、茎和花等外植体直接再分化成花芽的试验表明：叶片的外植体在有ＢＡ时可再分化出只有红色花瓣的不正常花芽;在含ＺＴ的培养基中再分化出具有１～２片叶或无叶的花芽,其花有两性花,雌花和仅单个雌蕊的不正常花,两性花可发育成结籽的果实;ＫＴ未能诱导花芽分化。茎外植体,３种ＣＴＫ都不能诱导出花芽。花等外植体仅在ＫＴ３ｍｇ／Ｌ的培养中再分化出无叶的不正常花芽,ＺＴ和ＢＡ的处理均不能诱导出花芽。     

The reductive acetyl coenzyme A pathway: sequence and heterologous expression of active methyltetrahydrofolate:corrinoid/iron-sulfur protein methyltransferase from Clostridium thermoaceticum.

The methyltransferase (MeTr) from Clostridium thermoaceticum transfers the N5-methyl group of (6S)-methyltetrahydrofolate to the cobalt center of a corrinoid/iron-sulfur protein in the acetyl coenzyme A pathway. MeTr was purified to homogeneity and shown to lack metals. The acsE gene encoding MeTr was sequenced and actively expressed in Escherichia coli at a level of 9% of cell protein. Regions in the sequence of MeTr and the E. coli cobalamin-dependent methionine synthase were found to share significant homology, suggesting that they may represent tetrahydrofolate-binding domains.     

Characterization of the interaction of the glp repressor of Escherichia coli K-12 with single and tandem glp operator variants.

The glp operons of Escherichia coli are negatively controlled by the glp repressor. Comparison of the repressor-binding affinities for consensus and altered consensus operators in vivo showed that all base substitutions at positions 3, 4, 5, and 8 from the center of the palindromic operator caused a striking decrease in repressor binding. Substitutions at other positions had a severe to no effect on repressor binding, depending on the base substitution. The results obtained indicate that the repressor binds with highest affinity to operators with the half-site WATKYTCGWW, where W is A or T, K is G or T, and Y is C or T. Strong cooperative binding of the repressor to tandem operators was demonstrated in vivo. Cooperativity was maximal when two 20-bp operators were directly repeated or when 2 bp separated the two operators. Cooperativity decreased with the deletion of 2 bp or the addition of 4 bp between the individual operators. Cooperativity was eliminated with a 6-bp insertion between the operators.     

Extractable sulphate and organic sulphur in soils and their availability to plants

Ten soils collected from the major arable areas in Britain were used to assess the availability of soil sulphur (S) to spring wheat in a pot experiment. Soils were extracted with various reagents and the extractable inorganic SO₄-S and total soluble S(SO₄-S plus a fraction of organic S) were determined using ion chromatography (IC) or inductively-coupled plasma atomic emission spectrometry (ICP-AES), respectively. Water, 0.016 M KH₂PO₄, 0.01 M CaCl₂ and 0.01 M Ca(H₂PO₄)₂ extracted similar amounts of SO₄-S, as measured by IC, which were consistently smaller than the total extractable S as measured by ICP-AES. The amounts of organic S extracted varied widely between different extractants, with 0.5 M NaHCO₃ (pH 8.5) giving the largest amounts and 0.01 M CaCl₂ the least. Organic S accounted for approximately 30–60% of total S extracted with 0.016 M KH₂PO₄ and the organic C:S ratios in this extract varied typically between 50 and 70. The concentrations of this S fraction decreased in all soils without added S after two months growth of spring wheat, indicating a release of organic S through mineralisation. All methods tested except 0.5 M NaHCO₃-ICP-AES produced satisfactory results in the regression with plant dry matter response and S uptake in the pot experiment. In general, 0.016 M KH₂PO₄ appeared to be the best extractant and this extraction followed by ICP-AES determination was considered to be a good method to standardise on.