Flavonoids as superoxide scavengers and antioxidants

The superoxide anions scavenging activity and antioxidation of seven flavonoids--quercetin, rutin, morin, acacetin, hispidulin, hesperidin, and naringin--were studied. The superoxide anions were generated in a phenazin methosulphate-NADH system and were assayed by reduction of nitroblue tetrazolium. The scavenging activity ranked: rutin was the strongest, and quercetin and naringin the second, while morin and hispidulin were very weak. The concentration values yielding 50% inhibition of lipid peroxidation in mouse liver homogenate were in order of 10(-6) M for quercetin, rutin, and morin; and of 10(-5) M for acacetin and hispidulin, while naringin and hesperidin had no antioxidative action. In comparison with the antioxidative and scavenging activities of flavonoids, there are no correlations.     

云南建水早第三纪哺乳类的发现

本文记述了在云南省建水县岔科地区发现的哺乳动物化石。根据豫鼠(Yuomys),定地层时代为晚始新世。这套地层暂称岔科组,以示滇南地区第一个含早第三纪哺乳动物的地点和层位。     

小麦—天兰偃麦草—黑麦三属杂种花粉植株诱导条件的研究

研究表明,三属杂种处于单核中晚期阶段的花粉最适于诱导形成愈伤组织。低温预处理对促进三属杂种花粉愈伤组织的诱导有一定的作用。利用以马铃薯提取物为基础物质的马铃薯-Ⅱ培养基作诱导培养基,其愈伤组织诱导与分化的频率比目前两个较好的合成培养基要高。同一个三属杂种F_1春、秋播种植株之间在形成愈伤组织的能力上有较大的差异,秋播材料形成愈伤组织的能力明显高于春播材料。F_(?)杂种植株诱导愈伤组织和分化植株的频率均比F_1杂种明显提高。     

Physical identification of branched intron side-products of splicing in Trypanosoma brucei.

Every mRNA in trypanosomes consists of two exons, a common 5' capped mini-exon or spliced leader and a coding-exon. All evidence suggests that the exons are joined by trans-splicing of two individual precursor RNAs, the mini-exon donor RNA or spliced leader precursor RNA (medRNA) and the pre-mRNA. We studied intermediates of the splicing reaction using denaturing two-dimensional PAGE and structurally identified a group of small (approximately 180-300 nt) non-polyadenylated, Y-shaped branched RNAs. The branched Y-shaped RNAs contain the 105 nt medRNA derived intron, joined in a 2'-5' phosphodiester bond to small heterogeneously sized RNAs. These non-polyadenylated branched Y-shaped RNA molecules are analogous to the lariat shaped introns of higher eukaryotes and presumably represent the released intron-like by-products of a trans-splicing reaction which joins the mini-exon and the major coding-exon.     

Transposition of the Streptococcus lactis ssp. lactis Z270 lactose plasmid to pVA797: demonstration of an insertion sequence and its relationship to an inverted repeat sequence isolated by self-annealing

The lactose plasmid pUCL22 of the single plasmid strain Streptococcus lactis ssp. lactis Z270 was demonstrated to fuse with the heterologous conjugative plasmid pVA797. The fusion of pUCL22 with pVA797 occurred by recombination between a specific sequence of pUCL22 and different sites of pVA797. The cointegrates of pUCL22::pVA797 were unstable: in the absence of lactose selection, they segregated plasmids that corresponded to pVA797 enlarged by one sequence of 1.2 kb, common to all derivative plasmids. This resolution sequence (RS) was shown to originate in the 9.7 kb BstEII restriction fragment of pUCL22 and to duplicate during replicon fusion. In addition, after nuclease S1 treatment of pUCL22 DNA, a self-annealing sequence was isolated; the two copies of this inverted repeat (IR) sequence were located on the 18 kb BamHI segment of the plasmid. This latter sequence was distinct from the RS with which it hybridized weakly. The RS was responsible for the transposition of the entire lactose plasmid; the role of the IR remains to be elucidated.     

Effects of ATP on Phosphatidylinositol-Phospholipase C and Inositol 1-Phosphate Accumulation in Rat Brain Synaptosomes

Incubation of rat brain synaptosomes prelabeled with [2-3H]inositol resulted in a time-dependent release of labeled inositol 1-phosphate. This process was Ca2+ dependent, and ATP (1 mM) enhanced the inositol 1-phosphate formation three- to fivefold. Using [1-14C]arachidonoyl-phosphatidylinositol which was introduced into saponin-permeabilized synaptosomes, ATP (1 mM) and free Ca2+ (approximately 20 microM) enhanced the phospholipase C hydrolysis of this substrate to form labeled diacylglycerol. When the same permeabilized synaptosomal preparation was incubated with [2-3H]inositol-phosphatidylinositol, ATP not only enhanced the formation of labeled inositol 1-phosphate, but also inhibited the conversion of inositol 1-phosphate to inositol. Furthermore, ATP appeared to reduce the Ca2+ requirement of the phosphatidylinositol-phospholipase C. Inhibition of the conversion of inositol 1-phosphate to inositol could not be overcome by increasing the Mg2+ concentration in the incubation medium. Although the ATP effect is not viewed as a receptor-mediated event, it is possible that such an event may occur in synaptosomes under conditions in which intrasynaptic Ca2+ concentration becomes elevated.     

Two specific topoisomerase II inhibitors prevent replication of human cytomegalovirus DNA: an implied role in replication of the viral genome.

In this study, we show that human cytomegalovirus DNA synthesis is inhibited in infected confluent human embryonic lung cells treated with the DNA-intercalative topoisomerase II inhibitor 4-9'-(acridinylamino)methanesulfon-m-anisidide (m-AMSA). Similar inhibitory effects were observed with VM-26, a nonintercalative topoisomerase II inhibitor. This antiviral effect is not attributable to cytotoxic effects per se. Furthermore, m-AMSA appears to have a notably irreversible inhibitory effect on human cytomegalovirus DNA replication. No inhibition of viral DNA synthesis was observed with o-AMSA, a DNA-intercalative isomer of m-AMSA that does not inhibit topoisomerase II.     

Detection of a single-copy gene on plant chromosomes by in situ hybridization

Summary DNA recombinant technology, combined with improvements in hybridization efficiency and quality of chromosome spreads, has made the method of in situ hybridization a reliable tool for gene mapping used by mammalian cytogeneticists to complement other methods. By appropriate alterations of the method, we demonstrate that detection of unique genes can be achieved along plant chromosomes despite some inherent disadvantages of the plant material. Using genomic subclones homologous to 6.6 kb of the single-copy chalcone synthase gene in parsley, we report the first example of chromosomal detection and localization of a unique endogenous gene in plants.