Conserved sequences in both coding and 5'' flanking regions of mammalian opal suppressor tRNA genes.

The rabbit genome encodes an opal suppressor tRNA gene. The coding region is strictly conserved between the rabbit gene and the corresponding gene in the human genome. The rabbit opal suppressor gene contains the consensus sequence in the 3' internal control region but like the human and chicken genes, the rabbit 5' internal control region contains two additional nucleotides. The 5' flanking sequences of the rabbit and the human opal suppressor genes contain extensive regions of homology. A subset of these homologies is also present 5' to the chicken opal suppressor gene. Both the rabbit and the human genomes also encode a pseudogene. That of the rabbit lacks the 3' half of the coding region. Neither pseudogene has homologous regions to the 5' flanking regions of the genes. The presence of 5' homologies flanking only the transcribed genes and not the pseudogenes suggests that these regions may be regulatory control elements specifically involved in the expression of the eukaryotic opal suppressor gene. Moreover the strict conservation of coding sequences indicates functional importance for the opal suppressor tRNA genes.     

黄素氧还蛋白参与的固氮链电子传递

棕色固氮菌中电子载体Fld直接向固氮酶铁蛋白传递电子。Fld_(ox)至Fld_R是双电子二步还原反应,极谱半波电位分别为-210、-550 mV。Fld_(ox)至Fld_(SR)的中点电位为-280 mV,Fld_(SR)至Fld_R为-500mV。铁蛋白中点电位为-256mV,加MgATP后为-390 mV。Fld_R与铁蛋白ox组成的电池电动势为244mV,电子传递可自发进行,反应的J△G~o为-23KJ/摩尔,铁蛋白被Fld_R还原的K_a=1.3×120~4,加入MgATP后△G~o为-10.6KJ/摩尔,K_a=72。因此,未加入MgATP时电子传递反应更易进行。     

不同发育年龄大鼠肝细胞及其溶酶体对急性低氧的应答

人工低压舱内模拟高原低氧24h,并与2300m对照组比较,观察不同发育年龄大鼠SGOT活力,肝溶酶体总酸性磷酸酶、非沉淀酸性磷酸酶和芳基硫酸酯酶活力及肝重、肝细胞糖原、蛋白和总脂含量的变化。在海拔5000m高度,10天鼠各酶活力、570天鼠总酸性磷酸酶和芳基硫酸酯酶活力明显升高;35和75天鼠各酶活力未见显著变化;在海拔8000m高度,各年龄组鼠上述各酶活力均显著升高。随着海拔高度的升高,各组大鼠肝重呈不同程度的下降,肝细胞糖原含量非常明显地减少,35和75天鼠8000m组全肝蛋白含量下降明显,10、35、75天鼠肝细胞总脂累积。上述结果综合分析表明:低氧致使大鼠肝细胞损伤属一普遍性效应,新生期和老年期大鼠肝细胞耐低氧能力不及幼年期和成年期大鼠。     

小蜉属小蜉亚属一新种：蜉蝣目：小蜉科

本文记述小蜉属小蜉亚属 subgenus Ephemerella Walsh 一新种,小蜉亚属种类多,全世界已知有40种左右,广布于北美、苏联、日本等国,但中国尚未发现,因此本文也是小蜉亚属在中国的首次报道。     

Inter-alpha-trypsin inhibitor. Inhibition spectrum of native and derived forms

The conversion of inter-alpha-trypsin inhibitor (I alpha I) into active, acid-stable derivatives by proteolytic degradation has been tested with 10 different proteinases. Of these, only plasma kallikrein, cathepsin G, neutrophil elastase, and the Staphylococcus aureus V-8 proteinase were found to be effective, each releasing more than 50% of this activity. However, a strong correlation between inhibitor degradation and significant release of acid-stable activity could only be found with the V-8 enzyme. Inhibition kinetics for the interaction of native I alpha I, the inhibitory fragment released by digestion with S. aureus V-8 proteinase, or the related urinary trypsin inhibitor, with seven different proteinases indicated that all had essentially identical Ki values with an individual enzyme and, where measurements were possible, nearly identical second order association rate constants. Significantly, none of the five human proteinases tested, including trypsin, chymotrypsin, plasmin, neutrophil elastase, and cathepsin G, would appear to have low enough Ki values to be physiologically relevant. Thus, the role of native I alpha I or its degradation products in controlling a specific proteolytic activity is still unknown.     

Reduced biopterin as a cofactor in the generation of nitrogen oxides by murine macrophages

Generation of nitric oxide (NO.), an autacoid with vasorelaxant and cytotoxic properties, requires at least three cytosolic components in mouse macrophages besides L-arginine and NADPH. One or more components appear after induction by immunologic stimuli; two or more are present in both activated and non-activated macrophages. The constitutive factors can be separated on a Mr approximately 30,000 cut-off filter into high Mr fraction (HF) and low Mr fraction (LF) (Stuehr, D. J., Kwon, N. S., Gross, S. S., Thiel, B. A., Levi, R., and Nathan, C. F. (1989) Biochem. Biophys. Res. Commun. 161, 420-426). Herein we characterize the major active component in LF. The active component was dialyzable (Mr less than approximately 1,000), water soluble, and cationic at acidic to neutral pH. Fractionation on a C18 column in an acetonitrile/water gradient yielded one broad peak of activity, most of which corresponded to a fluorophore with the excitation/emission spectra of biopterins. Gas chromatography isolated a species in this peak with the mass spectrum of biopterin. Of 14 pteridines tested, only 7,8-dihydrobiopterin (H2biopterin) or 5,6,7,8-tetrahydrobiopterin (H4biopterin) could replace LF in synergizing with HF and the inducible component(s) to generate NO-2 and NO-3, the accumulating oxidation products of NO.. Half-maximal activity required 20-30 nM reduced biopterins. LFs from three cell lines were active in proportion to their content of biopterins; addition of reduced biopterins restored activity to LF from biopterin-deficient cells. Enhancement of NO-2 generation in the presence of H2biopterin but not H4biopterin was abolished by methotrexate and aminopterin, inhibitors of dihydrofolate reductase. These findings implicate a redox cycle in which the generation of NO. is facilitated by catalytic amounts of H4biopterin.     

Nucleotide sequence and presumed secondary structure of the 28S rRNA of pea aphid implication for diversification of insect rRNA

Determination of the entire nucleotide sequence of the aphid 28S ribosomal RNA gene (28S rDNA) revealed that it is 4,147 by in length with a G + C content of 60.3%. Based on the nucleotide sequence, we constructed a presumed secondary-structure model of the aphid 28S rRNA which indicated that the aphid 28S rRNA is characterized by the length and high G + C content of its variable regions. The G + C content of the aphid's variable regions was much higher than that of the entire sequence of the 28S rRNA, which formed a striking contrast to those ofDrosophila with the G + C content much lower than the entire 28S molecule. In this respect, the aphid 28S rRNA somewhat resembled those of vertebrates. This is the third report of a complete large-subunit rRNA sequence from an arthropod, and the first 28S rRNA sequence for a nondipterous insect. Correspondence to: H. Ishikawa     

Chronic In Vivo Sodium Azide Infusion Induces Selective and Stable Inhibition of Cytochrome c Oxidase

Abstract: The effect of chronic subcutaneous infusion of sodium azide on the activity of mitochondrial respiratory chain enzymes was investigated in Sprague-Dawley rats. Treatment with ∼1 mg/kg/h sodium azide induced chronic, partial inhibition of cytochrome c oxidase, whereas the activities of respiratory complexes I and III were not significantly affected. The inhibition of cytochrome c oxidase was evident by 7 days after infusion began, and the effect was stable for at least 3 weeks. The selectivity of azide for cytochrome c oxidase is discussed in the context of other findings of azide effects on enzymes. The results of the present study indicate that the sodium azide infusion paradigm described here provides a useful tool for the evaluation of selective and stable cytochrome oxidase inhibition in vivo.