ISOLATION OF ACTINOMYCIN D FROM MARINE DERIVED Streptomyces

The bioactive substance producing strain, a marine bacterium A5S-46 was found in the antibacterial screening. This strain was isolated from the artificial sponge set in the coastal seawater at Iriomote islands (Japan). The crude extract from culture broth of the strain A5S-46 was assayed to the antibacterial activity test against the seven kinds of bacterial test strains. The active substance accumulated in the both bacterial cells and culture supernatant. Based on the 1H NMR and the LC/PDA/MS data, the bioactive substance was identified to be actinomycin D.   Keywords: Marine bacteria, Actinomycin D, Antibacterial, Anticance

Intrauterine Pressures Adjusted by Reichert's Membrane Are Crucial for Early Mouse Morphogenesis

Mammalian embryogenesis proceeds in utero with the support of nutrients and gases from maternal tissues. However, the contribution of the mechanical environment provided by the uterus to embryogenesis remains unaddressed. Notably, how intrauterine pressures are produced, accurately adjusted, and exerted on embryos are completely unknown. Here, we find that Reichert’s membrane, a specialized basement membrane that wraps around the implanted mouse embryo, plays a crucial role as a shock absorber to protect embryos from intrauterine pressures. Notably, intrauterine pressures are produced by uterine smooth muscle contractions, showing the highest and most frequent periodic peaks just after implantation. Mechanistically, such pressures are adjusted within the sealed space between the embryo and uterus created by Reichert’s membrane and are involved in egg-cylinder morphogenesis as an important biomechanical environment in utero. Thus, we propose the buffer space sealed by Reichert’s membrane cushions and disperses intrauterine pressures exerted on embryos for egg-cylinder morphogenesis

LDL-C/HDL-C Ratio Predicts Carotid Intima-Media Thickness Progression Better Than HDL-C or LDL-C Alone

High-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) are strong predictors of atherosclerosis. Statin-induced changes in the ratio of LDL-C to HDL-C (LDL-C/HDL-C) predicted atherosclerosis progression better than LDL-C or HDL-C alone. However, the best predictor of subclinical atherosclerosis remains unknown. Our objective was to investigate this issue by measuring changes in carotid intima-media thickness (IMT). A total of 1,920 subjects received health examinations in 1999, and were followed up in 2007. Changes in IMT (follow-up IMT/baseline IMT × 100) were measured by ultrasonography. Our results showed that changes in IMT after eight years were significantly related to HDL-C (inversely, P < 0.05) and to LDL-C/HDL-C ratio (P < 0.05). When the LDL-C/HDL-C ratios were divided into quartiles, analysis of covariance showed that increases in the ratio were related to IMT progression (P < 0.05). This prospective study demonstrated the LDL-C/HDL-C ratio is a better predictor of IMT progression than HDL-C or LDL-C alone

Oxidative Stress Impairs the Heat Stress Response and Delays Unfolded Protein Recovery

Background: Environmental changes, air pollution and ozone depletion are increasing oxidative stress, and global warming threatens health by heat stress. We now face a high risk of simultaneous exposure to heat and oxidative stress. However, there have been few studies investigating their combined adverse effects on cell viability. Principal Findings: Pretreatment of hydrogen peroxide (H2O2) specifically and highly sensitized cells to heat stress, and enhanced loss of mitochondrial membrane potential. H 2O 2 exposure impaired the HSP40/HSP70 induction as heat shock response (HSR) and the unfolded protein recovery, and enhanced eIF2a phosphorylation and/or XBP1 splicing, land marks of ER stress. These H2O2-mediated effects mimicked enhanced heat sensitivity in HSF1 knockdown or knockout cells. Importantly, thermal preconditioning blocked H 2O 2–mediated inhibitory effects on refolding activity and rescued HSF1 +/+ MEFs, but neither blocked the effects nor rescued HSF1-/- MEFs. These data strongly suggest that inhibition of HSR and refolding activity is crucial for H2O2–mediated enhanced heat sensitivity. Conclusions: H2O2 blocks HSR and refolding activity under heat stress, thereby leading to insufficient quality control and enhancing ER stress. These uncontrolled stress responses may enhance cell death. Our data thus highlight oxidative stres

Collaborative Action of Brca1 and CtIP in Elimination of Covalent Modifications from Double-Strand Breaks to Facilitate Subsequent Break Repair

Topoisomerase inhibitors such as camptothecin and etoposide are used as anti-cancer drugs and induce double-strand breaks (DSBs) in genomic DNA in cycling cells. These DSBs are often covalently bound with polypeptides at the 3′ and 5′ ends. Such modifications must be eliminated before DSB repair can take place, but it remains elusive which nucleases are involved in this process. Previous studies show that CtIP plays a critical role in the generation of 3′ single-strand overhang at “clean” DSBs, thus initiating homologous recombination (HR)–dependent DSB repair. To analyze the function of CtIP in detail, we conditionally disrupted the CtIP gene in the chicken DT40 cell line. We found that CtIP is essential for cellular proliferation as well as for the formation of 3′ single-strand overhang, similar to what is observed in DT40 cells deficient in the Mre11/Rad50/Nbs1 complex. We also generated DT40 cell line harboring CtIP with an alanine substitution at residue Ser332, which is required for interaction with BRCA1. Although the resulting CtIPS332A/−/− cells exhibited accumulation of RPA and Rad51 upon DNA damage, and were proficient in HR, they showed a marked hypersensitivity to camptothecin and etoposide in comparison with CtIP+/−/− cells. Finally, CtIPS332A/−/−BRCA1−/− and CtIP+/−/−BRCA1−/− showed similar sensitivities to these reagents. Taken together, our data indicate that, in addition to its function in HR, CtIP plays a role in cellular tolerance to topoisomerase inhibitors. We propose that the BRCA1-CtIP complex plays a role in the nuclease-mediated elimination of oligonucleotides covalently bound to polypeptides from DSBs, thereby facilitating subsequent DSB repair