Chitosan staple fibers and their chemical modification with some aldehydes

Nine wet-spinning conditions were examined for the preparation of chitosan staple fibers, and novel five N-alkylidene and N-arylidene-chitosan staple fibers were obtained by the post-treatment of the chitosan fibers with aldehydes including vanillin. The tenacity and elongation values of the chitosan filaments were almost unchanged by their post-treatment with monoaldehydes except that with formaldehyde and glyoxal. However, these values decreased significantly in the partially N-modified filaments, which were obtained by the pre-treatment with vanillin. The chitosan filaments (31–79 μm in diameter) had a scaly structure on the filament surface as examined by SEM observation.     

Synthesis of 8,2'-ethano-cyclo-2'-deoxyadenosines

The radical- or photo-cyclization of protected 2'-iodoethyl or 2'-phenylthioethyl derivatives of 2'-deoxyadenosine afforded the 8,2'-ethano-cyclo-2'-deoxyadenosine, a new carbon-bridged adenine cyclonucleoside.     

In vitro effects of juvenile hormone analog on wing disc morphogenesis under ecdysteroid treatment in the female-wingless bagworm moth Eumeta variegata (Insecta: Lepidoptera, Psychidae)

Female adults of the bagworm moth, Eumeta variegata, lack wings completely, whereas male adults of this species have functional wings. We previously found that ecdysteroid induces apoptotic events in the female wing rudiment of E. variegata in vitro, whereas the male wing discs cultured with 20-hydroxyecdysone (20E) underwent apolysis and then cell differentiation. To investigate whether juvenile hormone (JH) in involved in sex-specific cellular response to ecdysteroid during wing development between sexes of E. variegata, we tested the effects of juvenile hormone analog (JHA), methoprene, and 20E on wing disc morphogenesis between sexes in vitro. Using transmission electron microscopy (TEM), we found that both higher concentration of JHA (5 μg/ml) and 20E (1 μg/ml) addition induced cell death (apoptosis) in the male wing discs but not induced cell death in the female wing rudiments in vitro in E. variegata. These culture experiments clearly detected the differential responses of wing discs to JHA under ecdysteroid treatment between sexes. We propose two important hypotheses: (1) JH is not significantly involved in the suppression of the female wing rudiment morphogenesis under 20E treatment, (2) female wing rudiment has lost the ability for cell proliferation in response to the stimulus of 20E.     

Phenylalanine 171 is a molecular brake for translesion synthesis across benzo[a]pyrene-guanine adducts by human DNA polymerase kappa

Human cells possess multiple specialized DNA polymerases (Pols) that bypass a variety of DNA lesions which otherwise would block chromosome replication. Human polymerase kappa (Pol κ) bypasses benzo[a]pyrene diolepoxide-N(2)-deoxyguanine (BPDE-N(2)-dG) DNA adducts in an almost error-free manner. To better understand the relationship between the structural features in the active site and lesion bypass by Pol κ, we mutated codons corresponding to amino acids appearing close to the adducts in the active site, and compared bypass efficiencies. Remarkably, the substitution of alanine for phenylalanine 171 (F171), an amino acid conserved between Pol κ and its bacterial counterpart Escherichia coli DinB, enhanced the efficiencies of dCMP incorporation opposite (-)- and (+)-trans-anti-BPDE-N(2)-dG 18-fold. This substitution affected neither the fidelity of TLS nor the efficiency of dCMP incorporation opposite normal guanine. This amino acid change also enhanced the binding affinity of Pol κ to template/primer DNA containing (-)-trans-anti-BPDE-N(2)-dG. These results suggest that F171 functions as a molecular brake for TLS across BPDE-N(2)-dG by Pol κ and that the F171A derivative of Pol κ bypasses these DNA lesions more actively than does the wild-type enzyme.     

Effect of salinity on growth and toxin production of <Emphasis Type="Italic">Alexandrium minutum</Emphasis> isolated from a shrimp culture pond in northern Vietnam

A clonal culture of a Vietnamese strain of Alexandrium minutum, AlexSp17, was subjected to different salinity treatments to determine the growth and toxin production of this strain that produces a novel toxin analogue, deoxy GTX4-12ol. The experiment was carried out in batch cultures without pre-acclimatization at seven salinity treatments from 5 to 35 psu, under constant temperature of 25°C, illumination of 140 μmol photon m⁻² s⁻¹, and 12:12 light/dark photoperiod. The strain grew in all salinity treatments, with optimum growth at 10–15 psu. However, the specific growth rate (0.2 day⁻¹) was lower than those reported in Malaysian strains and other strains from different geographical areas. The optimum range of salinity for the growth of this species agreed with field observations of the locality of origin. No significant change in toxin profiles was observed at different salinities. The cellular toxin quota, Qt, was not affected by the salinity-dependent growth rate. The toxin GTX4-12ol is presumed to be a transformation product of GTX4 from specific cellular reductase enzymes. Further investigation at the molecular level of toxin biosynthesis and subcellular enzyme activities is needed to provide insight in the production of this unique toxin analogue.     

Schwann-spheres derived from injured peripheral nerves in adult mice--their in vitro characterization and therapeutic potential

Multipotent somatic stem cells have been identified in various adult tissues. However, the stem/progenitor cells of the peripheral nerves have been isolated only from fetal tissues. Here, we isolated Schwann-cell precursors/immature Schwann cells from the injured peripheral nerves of adult mice using a floating culture technique that we call "Schwann-spheres." The Schwann-spheres were derived from de-differentiated mature Schwann cells harvested 24 hours to 6 weeks after peripheral nerve injury. They had extensive self-renewal and differentiation capabilities. They strongly expressed the immature-Schwann-cell marker p75, and differentiated only into the Schwann-cell lineage. The spheres showed enhanced myelin formation and neurite growth compared to mature Schwann cells in vitro. Mature Schwann cells have been considered a promising candidate for cell-transplantation therapies to repair the damaged nervous system, whereas these "Schwann-spheres" would provide a more potential autologous cell source for such transplantation.     

Microarray-based target identification using drug hypersensitive fission yeast expressing ORFeome

Identification of the cellular target of small molecules is a major challenge to developing biological tools and drug leads. Here we report a novel microarray-based system for identification of the target or the target pathway of small molecules using a set of drug-hypersensitive fission yeast strains that collectively overexpress each gene in the open reading frame-ome. The major advantage of this method is that it provides genome-wide interrogation but requires a relatively small amount of the test compound. Using this system, we identified 28 genes linked to etoposide sensitivity, which included genes for the drug target topoisomerase II and other plausible factors that regulate etoposide tolerance. Thus, our approach can accelerate the process of target identification of small molecules, which has the potential to reveal highly conserved genes of clinical relevance.     

Draft Genome Sequencing and Comparative Analysis of Aspergillus sojae NBRC4239

We conducted genome sequencing of the filamentous fungus Aspergillus sojae NBRC4239 isolated from the koji used to prepare Japanese soy sauce. We used the 454 pyrosequencing technology and investigated the genome with respect to enzymes and secondary metabolites in comparison with other Aspergilli sequenced. Assembly of 454 reads generated a non-redundant sequence of 39.5-Mb possessing 13 033 putative genes and 65 scaffolds composed of 557 contigs. Of the 2847 open reading frames with Pfam domain scores of >150 found in A. sojae NBRC4239, 81.7% had a high degree of similarity with the genes of A. oryzae. Comparative analysis identified serine carboxypeptidase and aspartic protease genes unique to A. sojae NBRC4239. While A. oryzae possessed three copies of α-amyalse gene, A. sojae NBRC4239 possessed only a single copy. Comparison of 56 gene clusters for secondary metabolites between A. sojae NBRC4239 and A. oryzae revealed that 24 clusters were conserved, whereas 32 clusters differed between them that included a deletion of 18 508 bp containing mfs1, mao1, dmaT, and pks-nrps for the cyclopiazonic acid (CPA) biosynthesis, explaining the no productivity of CPA in A. sojae. The A. sojae NBRC4239 genome data will be useful to characterize functional features of the koji moulds used in Japanese industries.