Multilayer biological structure and mixing in the upper water column of Lake Biwa during summer 2008

We carried out a 24-h station experiment at Lake Biwa (Japan) to measure mixing events and concurrent biological signals using a free-fall microstructure profiler (TurboMAP-L), conventional hydrographic measurement device (F-probe), and the Tracker acoustic profiling system (TAPS). A clearly defined three-layer physical system was observed. Two layers were actively mixed: the surface-mixed layer and the subsurface-mixed layer. Both winds and night-time convection create the surface-mixed layer, and vertical shear due to a counterclockwise gyre maintains turbulence in the subsurface mixing layer. A strongly stratified layer between these two mixing layers is almost turbulence free, so no material flux is expected. A local oxygen maximum layer, a local oxygen minimum layer, and layers of increased chlorophyll and zooplankton abundance are all located in this strongly stratified layer. The data show the intricate influence of physical processes on the structure of biological systems and their combined influence on biogeochemical and trophic transfers in aquatic systems.     

Production of mannosylerythritol lipids as biosurfactants by resting cells ofCandida antarctica

Summary The resting cells ofCandida antarctica strain T-34 was found to produce a large amount of mannosylerythritol lipids as biosurfactants when incubated in the medium containing only the carbon source. The resting cells prepared from different water-soluble carbon sources were able to produce the lipids abundantly from water-insoluble carbon sources. Under the optimal conditions in a shake culture, the concentration of the total lipids amounted to about 47 g/l after 6 days, and the yield of the lipids became higher than that obtained by using the growing cells of the strain.     

A 570-kb DNA Sequence of the Escherichia coli K-12 Genome Corresponding to the 28.0-40.1 min Region on the Linkage Map

The 569,750 base pair sequence corresponding to the 28.0–40.1min region on the genetic map of Escherichia coli K-12 (W3110)was determined. This region includes the replication terminusregion and contained at least 549 potential open reading frames.Among them, 160 (29%) were previously reported, 174 (32%) werehomologous to other known genes, 102 (18%) were identical orsimilar to hypothetical genes registered in databases, and theremaining 113 (21%) did not show a significant similarity toany other gene. Of interest was the finding of a large numberof genes and gene clusters in andnear the replication terminationregion which had been thought to be genetically silent. Thoseincludeda cluster of genes for fatty acid ß-oxidation,the third copy of the pot (spermidine/putrescine transport system)gene cluster, the second dpp (dipeptide transport system) operon,the second dsm (anaerobic dimethyl sulfoxide reductase) operon,a cluster of fim (fimbrial) genes anda DNA helicase-like genewith a high molecular weight. In addition, we found the dnaC-and dnaT-like genes in the cryptic prophage, Rac, anda numberof genes originated probably from plasmids.     

Epr Spectroscopic Studies of Detection of a Carbon-Centered Free Radical During Acetylcholine-Induced and Endothelium-Dependent Relaxation of Guinea Pig Pulmonary Artery

Vascular smooth muscle relaxation by several vasodilators, including acetylcholine (Ach) and ATP, depends on the presence of intact endothelium. Ach is thought to activate muscarinic receptors on endothelium to release an endothelium-derived relaxing factor (EDRF) which brings about relaxation of smooth muscle. In order to assess the role of free radicals in the endothelium-dependent relaxation of blood vessel, we have studied the effect of a spin-trapping agent, phenyl t-butyl nitrone (PBN). on Ach-, ATP-, and sodium nitroprusside-induced relaxation of guinea pig pulmonary artery. Arterial strips were mounted in a 5-ml organ bath containing Krebs solution equilibrated with 95% O₂ and 5% CO₂ at 37°C. After increasing vascular tone by a synthetic prostaglandin endoperoxide analog (50 ng/ml), the strips relaxed dose-dependently in response to Ach (5 × 10^-8M), ATP (1.5 × 10^-6M) or sodium nitroprusside (6 × 10^-9 M). Removal of the endothelium abolished the relaxation by Ach or ATP, but did not affect the relaxation by sodium nitroprusside. PBN inhibited Ach-induced relaxation of pulmonary artery dose-dependently, but had no effect on relaxations by ATP or sodium nitroprusside. PBN did not block radioligand binding to muscarinic cholinergic membrane receptors on both chick embryonic heart and guinea pig pulmonary artery endothelial cells indicating that it does not block the muscarinic receptors. Spin trapping in combination with electron paramagnetic resonance (EPR) spectral analysis revealed a carbon-centered radical with hyperfine splitting constants of a_N = 16.0 G and a_β^H: = 3.85 G in the lipid extracts of pulmonary artery (0.2-0.4g) incubated with PBN (14mM) and Ach (3 × 10^-6M) for 20min. No signal was detected when endothelium was removed. Our data suggest that the endothelium-dependent relaxation of pulmonary artery by Ach is associated with the generation of a free-radical and can be prevented by a spin-trapping agent. ATP, however, relaxes the arterial smooth muscle by a different mechanism.     

Identification of DNA topoisomerases involved in immediate and transient DNA relaxation induced by heat shock inEscherichia coli

The linking number of plasmid DNA in exponentially growingEscherichia coli increases immediately and transiently after heat shock. The purpose of this study was to search for DNA topoisomerases that catalyze this relaxation of DNA. Neither introduction of atopA deletion mutation nor treatment of cells with DNA gyrase inhibitors affected the DNA relaxation induced by heat shock. Thus, DNA topoisomerase I and DNA gyrase are apparently not involved in the process. However, the reaction was inhibited by nalidixic acid or by oxolinic acid in thetopA mutant and the reaction was resistant to nalidixic acid in atopA mutant carrying, in addition, thenalA26 mutation. These results are interpreted as indicating that both DNA topoisomerase I and DNA gyrase are involved in the DNA relaxation induced by heat shock.     

Hyaluronidase expression in cultured growth plate chondrocytes during differentiation

Hyaluronan (HA) is a major component of the extracellular matrix of cartilage, contributes to its structural and functional integrity, and has various important roles in the differentiation of chondrocytes. HA metabolism is regulated by both anabolic and catabolic processes; however, the details have not yet been clarified. The purpose of this study was to clarify the expression patterns of hyaluronidase (HAase) mRNAs (from the relevant HAase genes: the HYALs) and HAase activity during chondrocyte differentiation. Cartilage tissue and growth plate chondrocytes were isolated from the ribs of 4-week-old male Japanese rabbits. The expression of HYAL mRNAs in cartilage was analyzed by in situ hybridization. The expression levels of HYAL mRNAs in the culture were analyzed for each of the chondrocyte differentiation stages by means of quantitative real-time polymerase chain reaction analysis. Enzymatic activity in the conditioned medium from the cultures was examined by using HA zymography and an enzyme-linked immunosorbent-like assay. The expression levels of HYAL1 and HYAL2 mRNAs were enhanced about 2.8-fold and 3.2-fold at the maximum during the early matrix forming stage, respectively, and by about 3.2-fold and 2.0-fold at the maximum in the hypertrophic stage, respectively. HYAL3 mRNA was not detected throughout the experimental period. HAase activity was enhanced at the early matrix forming and hypertrophic stages. These results suggest that selective expression of HYALs is essential for extracellular HA metabolism during chondrocyte differentiation.This research was supported by Grants-in-Aid (no. 11557166) for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan     

Preparation of N-substituted aryl and alkyl carbamates and their inhibitory effect on oat seed germination

A series of N-substituted aryl and alkyl carbamates (RNHCOOR'; R: aryl, alkyl; R': aryl, alkyl) was prepared and screened for inhibitory activity toward the germination of oat seeds. The activity of each compound was compared with that of chlorpropham (isopropyl 3-chlorocarbanilate). Some of the synthetic carbamates possessing the N-(phenylthio)methyl group, PhSCH2NHCOOR', showed inhibitory activity close or comparable to that of chlorpropham.     

Synthesis and Toxicity of Allethrin-(Z)-metabolites

(±)-trans-Allethrin-(Z)-ol (IV), (±)-trans-allethrin-(Z)-al (V) and (±)-trans-allethrin-(Z)-acid (VI), the minor components of allethrin metabolites in the insect body, were synthesized. The toxicities of newly synthesized allethrin derivatives (IV, V, VI) and of (±)-trans-allethrin-(E)-acid (Xc) to houseflies (Musca domestica L.) were examined by the injection method. And their low toxicities seem to support the hypothesis that oxidation at the isobutenyl side chain of the acid moiety of the allethrin molecule is a detoxication process in the insect body.