Antimutagenic effect of garlic (Allium sativum L.) on 4NQO-induced mutagenesis in Escherichia coli WP2

Aqueous extract prepared from garlic bulbs markedly suppressed the mutagenesis in both E. coli WP2 trp- and E. coli WP2 trp- uvrA- induced by 4-nitroquinoline 1-oxide (4NQO), but not that induced by UV. Cellular toxicity, inhibition of the expression of the Trp+ phenotype and delay of the first cell division after 4NQO treatment were not observed in the presence of the extract. Since the extract showed identical antimutagenic effects against 4NQO in both test strains but no effect on the mutagenesis of UV, it seems that the extract might act by inactivating the electrophilic group(s) of 4NQO or inhibiting its metabolic activation.     

Molecular approaches to problems in biogeochemical cycling

Summary By using molecular probe techniques in combination with activity and expression measurements, it is possible to estimate bacterial populations in nature. This information can be expooited to study a number of important environmental problems. For instance, it will be possible to study ecosystem perturbation and microbial competition, by altering an ecosystem or a laboratory model of an ecosystem, and assessing corresponding changes in key activities and populations. In addition, regulation of activities in the laboratory can be compared to the response of activities and populations in situ, to develop an understanding of the key parameters that control these processes in nature. These types of approaches are important steps for determining the role of microorganisms in geochemical cycling, in both specific habitats and on a global basis.     

Calicotyle urolophi n. sp. (Monogenea: Monocotylidae) from stingarees,Urolophus spp. (Elasmobranchii: Urolophidae) taken in coastal waters of Southern Australia

Calicotyle urolophi n. sp. is proposed for calicotylines found in the cloaca of three stingaree species, Urolophus cruciatus, U. bucculentus and U. paucimaculatus, collected off the southeastern coast of Tasmania. Variations in the soft body parts were observed between specimens taken from U. cruciatus and U. bucculentus but were not considered sufficient for separation into two species. C. urolophi is differentiated from other Calicotyle spp. found in the South Pacific by the configuration of the tubular male copulatory organ, the structure of the intestinal caeca and the arrangement of the vaginae. Amended diagnoses for the subfamily Calicotylinae and the genus Calicotyle are provided.     

Deregulation of arginine biosynthesis in Synechococcus sp. PCC7942

Summary In order to deregulate arginine biosynthesis in Synechococcus sp. PCC7942, d-arginine-resistant cell lines were selected following ethyl methanesulfonate mutagenesis of wild-type (WT) cells. Three of these arginine-producing mutant (APM) cell lines, APM1, APM31 and APM40, were putative regulatory mutants based upon secretion of l-arginine into their growth medium. HPLC of lyophilized post-harvest supernatants of APM 31 and 40 resolved two predominant amino acids, arginine and citrulline. In-vitro activity of N-acetylglutamate kinase (NAGK), the proposed regulatory enzyme of the arginine pathway, was about 100-fold less sensitive to l-arginine inhibition in extracts from APM 31 and 40 than the enzyme in WT extracts. The enzyme from APM 1 was 20-fold less sensitive to l-arginine inhibition than WT. The most likely site of mutation in each of the APM cell lines is in the gene for NAGK, rendering the enzymes insensitive to l-arginine feedback control. These strains can be utilized for the phototrophic production of arginine. Offprint requests to: S. E. Bingham     

Cationic probes: Specificity of distribution of metal-binding sites in bovine sperm

Salts of transition elements that alter the rate of sperm cell movement act at or near calcium-binding sites. After living bull sperm cells had been preincubated in VO₄^3?, Ni²⁺, Zn²⁺, Mn²⁺, and also La³⁺, they were then fixed. Crisply defined organelles and the absence of particulate deposits in the morphological controls contrasted sharply with the treated specimens; the latter contained regions of increased electron density, the nature and distribution of which depended on the test substance, reflecting the differential affinities of the specific ions. La³⁺ formed fine dense areas, mainly at the exocytic surface of the plasma membrane. VO₄^3? marks the cell surface but also left particulate densities within the cell. Ni²⁺ caused a nearly uniformly dense deposit at the surface and on the satellite fibers and axonemal microtubules. Zn²⁺ formed less uniform but coarser deposits, while in Mn²⁺ the distribution was similar to that in Zn²⁺ but much denser in the axonemal matrix and on the satellite fibers. Verapamil restricted the size and number of the opacities, while procaine permitted a similar distribution of slightly larger size reaction product. The differences in size and distribution of the enhanced densities were consistent and replicable for the individual assay substances. Vanadate, which specifically inhibits Na, K-ATPase, bound to ouabain-sensitive enzyme loci, however, completely disrupting the axonemal complex. This suggests that an important role of dynein in flagellar motion may relate to intracellular transport of Ca²⁺.     

海枣曲霉β-半乳糖苷酶的提纯与性质

 通过过聚乙二醇6000-磷酸钾缓冲液双相分离、Sephadex G-100凝胶过滤、DEAE-Sephadex A-50离子交换层析、羟基磷灰石层析及SephadexG-100凝胶过滤等提纯步骤,从海枣曲霉(Aspergillus phoenicis)麦麸培养物抽提液中提纯得到凝胶电泳均一的β-半乳糖苷酶。该酶的最适pH为3.5—4.0,最适温度为60℃(反应15分钟),在pH5.0—8.5之间及60℃以下稳定。在65℃和70℃保温时失活50％的时间分别为27和2分钟。用SDS凝胶电泳法和梯度凝胶电泳法分别测得该酶的分子量为115,000和118,000。薄层凝胶等电聚焦法测得其等电点为pH4.6。     

Study of Chromosomes in the Newborn after Ultrasonic Fetal Heart Monitoring in Labour

The effect of continuous-wave ultrasound on the chromosomes of newborn infants has been investigated. Twenty-four women were studied during labour. The fetal heart was monitored by a Sonicaid FM2 monitor applied to the abdomen, and continuous monitoring undertaken for intervals varying from 1 hour 5 minutes to 9 hours 25 minutes. There was no increase in the number of chromosome aberrations in cultures of blood taken from the insonated babies when compared with controls.