Glycerol kinase as a substitute for dihydroxyacetone kinase in a mutant of Klebsiella pneumoniae.

With dihydroxyacetone as the sole source of carbon and energy, constitutively synthesized glycerol kinase of the glp system supported aerobic growth of Klebsiella pneumoniae mutants lacking the inducible dihydroxyacetone kinase of the dha system. Glycerol kinase had an apparent Km of 0.01 mM for its physiological substrate and 1 mM for its surrogate substrate. However, the growth rate on dihydroxyacetone of cells relying on glycerol kinase increased with the concentration of the carbon and energy source up to 50 mM, suggesting that permeation is rate limiting.     

Catalysis by modified polyethylenimine of nucleophilic substitution reactions of azide ions

The reactions of azide ion with 4-chloro-3,5-dinitrobenzoate and with 4-acetoxy-3-nitrobenzoate catalyzed by laurylethyl polyethylenimine were examined at pH 5.72 and 25°C. In the presence of the polymer, marked accelerations were observed for nucleophilic attack of azide ion in the aromatic substitution reaction, but only small enhancements appeared in the acylation reaction. A detailed rate analysis indicates that the intrinsic reactivity of the reactants in the aromatic substitution reaction is increased in the environment of the polymer about 100 times more than is the reactivity of reactants in the acylation reaction. This difference is ascribed to the influence of the apolar environment of the polymer matrix on the more delocalized charge distribution in the transition state of the aromatic substitution reaction.     

Suppression of the immune response to immunotoxins with anti-CD4 monoclonal antibodies.

Treatment of normal mice with a mAb to CD4 (GK1.5) was explored as a means of inhibiting the antibody response to an immunotoxin. Three days of pretreatment with 200 micrograms of GK1.5 completely abrogated the primary antibody response to a 3-micrograms dose of a mutant diphtheria toxin conjugated to an anti-transferrin receptor antibody. The same dose and schedule of anti-CD4 antibody significantly reduced and delayed, but did not prevent, the anamnestic antitoxin response in animals that had been previously primed to the immunotoxin. Three daily injections of anti-CD4 antibodies followed by weekly doses of immunotoxin resulted in a 3-wk delay in the development of antitoxin antibodies, and the kinetics of the antitoxin response correlated with the kinetics of recovery of CD4+ T cells in the spleen and lymph nodes. The antitoxin response to repeated doses of immunotoxin was completely abrogated when anti-CD4 antibodies were given every 2 wk throughout the course of immunotoxin treatment. Thus, transient depletion of Th cells during treatment can block the immune response to an immunotoxin. There was no evidence of tolerance induction with this regimen.     

中国连香树科的系统研究——Ⅱ.次生木质部的显微和超微结构

本文报道连香树木材解剖和扫描电镜研究结果,连香树木材特征较为原始,具导管和管胞,导管端壁斜、梯状穿孔板、具有超出穿孔板的三生螺旋加厚,管胞为原始的梯纹管胞,木纤维壁上具裂隙状纹孔,木薄壁组织离管型,星散状分布,木射线异型。     

转移及非转移肿瘤移植后615小鼠血液流变学变化的研究

血道高转移瘤株FC、淋巴合并血道高转移瘤株U14、淋巴道高转移瘤株H22、非转移瘤株P615分别接种于336只纯系近交615小鼠.不同时间取血并处死动物,进行组织学及血液流变学检查.将转移瘤发展过程分为潜伏期、侵袭期、转移早、中、晚期,非转移瘤发展过程分为潜优期、增殖期、囊腔形成期及中心坏死期.本实验结果显示,不同转移能力及途径肿瘤发展的不同时期血液流变学变化规律不同,因而表明肿瘤侵袭、转移与血液流变学变化之间存在互为因果的紧密关系.其临床诊断及治疗意义被讨论.     

基因定点诱变删除及天然α型心钠素的分泌型表达

用基因定点诱变技术,删除了pO_1α ANF表达质粒中的33对碱基,使人α型心钠素结构基因直接与大肠杆菌分泌型表达质粒pIN-Ⅲ-OmPA中的信号肽酶切位点编码区相连,构成天然人α型心钠素的表达质粒pANF,在IPTG诱导下表达28肽的天然人α型心钠素。纯化后的表达产物具有天然心钠素的放免活性和很强的舒张血管的生物活性。     

Cloning and sequencing of IS1086, an Alcaligenes eutrophus insertion element related to IS30 and IS4351.

A new insertion sequence (IS), designated IS1086, was isolated from Alcaligenes eutrophus CH34 by being trapped in plasmid pJV240, which contains the Bacillus subtilis sacB and sacR genes. The 1,106-bp IS1086 element contains partially matched (22 of 28 bp) terminal-inverted repeats and a long open reading frame. Hybridization data suggest the presence of one copy of IS1086 in the strain CH34 heavy-metal resistance plasmid pMOL28 and at least two copies in its chromosome. Analysis of the IS1086 nucleotide sequence revealed striking homology with two other IS elements, IS30 and IS4351, suggesting that they are three close members in a family of phylogenetically related insertion sequences. One open reading frame of the Spiroplasma citri phage SpV1-R8A2 B was also found to be related to this IS family but to a lesser extent. Comparison of the G+C contents of IS30 and IS1086 revealed that they conform to their respective hosts (46 versus 50% for IS30 and Escherichia coli and 64.5% for IS1086 and A. eutrophus). The pressure on the AT/GC ratio led to a very different codon usage in these two closely related IS elements. Results suggesting that IS1086 transposition might be activated by some forms of stress are discussed.     

Incomplete fatty acid oxidation. The production and epimerization of 3-hydroxy fatty acids.

3-Hydroxydicarboxylic acids are major urinary metabolites derived from fatty acid metabolism. These compounds are produced from the omega-oxidation of 3-hydroxy fatty acids. The production of the precursor 3-hydroxy fatty acids from incomplete beta-oxidation of fatty acids in rat liver mitochondria was investigated. Independent of the chain length or the concentration of fatty acid substrates, the accumulation of 3-hydroxyacyl intermediates was relatively constant at the concentration of 3-5 nmol/mg of mitochondrial protein. The extent of the incomplete oxidation was the same in Percoll gradient-purified mitochondria. Rotenone treatment increased the production of 3-hydroxy fatty acids. 3-Hydroxy fatty acids did not exist as pure L-enantiomer as expected from beta-oxidation. Instead, these metabolites were epimerized to a near racemic mixture of D- and L-isomers with a slightly dominant D-isomer (58 +/- 3%). By using deuterium-isotope labeling, the mechanism of epimerizartion was shown to be a rapid dehydration-rehydration through trans-2-enoyl-CoA. In addition, cis-3 and trans-3 fatty acids were produced; these metabolites were derived from the isomerization of trans-2-enoyl-CoA. Epimerase and isomerase were thought to be enzymes involved in the oxidation of unsaturated fatty acids. Current data have shown that the metabolism of these acids is actually through NADPH-dependent reduction pathways. The activities of epimerase and isomerase detected in rat liver mitochondria possibly function mainly in the metabolism of saturated fatty acids in a reverse role to the conventional concept.