Biodegradation of a polyvinyl alcohol-starch blend plastic film

Attempts were made to elucidate the degradation mechanism of a polyvinyl alcohol (PVA)-starch blend plastic. A part of the starch fraction of this plastic was dissolved into an aqueous phase in a control test. Treatment with a PVA-degrading bacterium or enzyme gave a maximal weight loss of approximately 70% and film breakage occurred. Since this plastic contains 40% PVA, it is apparent that not only the PVA fraction but also a considerable portion of the starch fraction was lost from the film by treatment with the PVA-degrading enzyme. As the PVA-degrading bacterium and enzyme used here showed no starch-degrading activity, loss of the starch fraction seems to depend on its dissolution with degradation of the PVA fraction. These experimental results indicated that the degradation of the PVA fraction is an important requisite for complete degradation or decomposition of this plastic film.     

Phosphorylation-dependent scaffolding role of JSAP1/JIP3 in the ASK1-JNK signaling pathway. A new mode of regulation of the MAP kinase cascade

JSAP1 (also termed JIP3) is a scaffold protein that interacts with specific components of the JNK signaling pathway. Apoptosis signal-regulating kinase (ASK) 1 is a MAP kinase kinase kinase that activates the JNK and p38 mitogen-activated protein (MAP) kinase cascades in response to environmental stresses such as reactive oxygen species. Here we show that JSAP1 bound ASK1 and enhanced ASK1- and H(2)O(2)-induced JNK activity. ASK1 phosphorylated JSAP1 in vitro and in vivo, and the phosphorylation facilitated interactions of JSAP1 with SEK1/MKK4, MKK7 and JNK3. Furthermore, ASK1-dependent phosphorylation was required for JSAP1 to recruit and thereby activate JNK in response to H(2)O(2). We thus conclude that JSAP1 functions not only as a simple scaffold, but it dynamically participates in signal transduction by forming a phosphorylation-dependent signaling complex in the ASK1-JNK signaling module.     

Sarcolipin inhibits polymerization of phospholamban to induce superinhibition of sarco(endo)plasmic reticulum Ca2+-ATPases (SERCAs)

Sarcolipin (SLN), a regulator of the sarco(endo)plasmic reticulum Ca(2+)-ATPase of fast-twitch skeletal muscle (SERCA1a), is also expressed in cardiac and slow-twitch skeletal muscles where phospholamban (PLN) and SERCA2a are expressed. Co-expression in HEK-293 cells of SLN tagged N-terminally with a FLAG epitope (NF-SLN), PLN, and SERCAs followed by measurement of the Ca(2+) dependence of Ca(2+) transport activity in isolated microsomal fractions showed that NF-SLN can reduce the apparent Ca(2+) affinity of both SERCA1a (DeltaK(Ca) = -0.22 +/- 0.01 pCa units) and SERCA2a (DeltaK(Ca) = -0.37 +/- 0.04 pCa units). When SERCA1a or SERCA2a were co-expressed with both NF-SLN and PLN, inhibition was synergistic, reducing DeltaK(Ca) by about -1.0 pCa units. Co-immunoprecipitation showed that NF-SLN increased the binding of PLN to SERCA, whereas PLN did not increase the binding of NF-SLN to SERCA. Elevated Ca(2+) dissociates both PLN and NF-SLN from their complexes with both SERCA1a and SERCA2a, but NF-SLN induced resistance to Ca(2+) dissociation of the PLN.SERCA complex. Co-immunoprecipitation of PLN and NF-SLN without SERCA showed that NF-SLN binds directly to PLN and that NF-SLN inhibits the formation of PLN pentamers. Thus the ability of NF-SLN to elevate the content of PLN monomers can account, at least in part, for the superinhibitory effects of NF-SLN in the presence of PLN.     

The human MYOD1 transgene is suppressed by 5-bromodeoxyuridine in mouse myoblasts

5-Bromodeoxyuridine (BrdU) immediately and clearly suppresses expression of the mouse Myod1 and human MYOD1 genes in myoblastic cells. Despite various studies, its molecular mechanism remains unknown. We failed to identify a BrdU-responsive element of the genes in experiments in which reporter constructs containing known regulatory sequences were transferred to mouse C2C12 myoblasts. Therefore, we transferred human chromosome 11 containing the MYOD1 gene to the cells by microcell-mediated chromosome transfer. In the resulting microcell hybrids, BrdU suppressed expression of the transgene, as determined by quantitative real-time RT-PCR analysis. We then transfected human PAC clones containing the MYOD1 gene to the cells. In the resulting transfectants, BrdU suppressed the transgene similarly. Deletion analysis suggested that a BrdU-responsive element or chromatin structure exists between 24 and 47 kb upstream of the gene. These results are the first demonstrating BrdU-responsiveness of a transgene for the known BrdU-responsive genes and facilitating determination of its precise responsible structure.     

Laboratory-scale continuous reactor for soluble selenium removal using selenate-reducing bacterium,Bacillus sp. SF-1

A model continuous flow bioreactor (volume 0.5 L) was constructed for removing toxic soluble selenium (selenate/selenite) of high concentrations using a selenate-reducing bacterium, Bacillus sp. SF-1, which transforms selenate into elemental selenium via selenite for anaerobic respiration. Model wastewater contained 41.8 mg-Se/L selenate and excess lactate as the carbon and energy source; the bioreactor was operated as an anoxic, completely mixed chemostat with cell retention time between 2.2-95.2 h. At short cell retention times selenate was removed by the bioreactor, but accumulation of selenite was observed. At long cell retention times soluble selenium, both selenate and selenite, was successfully reduced into nontoxic elemental selenium. A simple mathematical model is proposed to evaluate Se reduction ability of strain SF-1. First-order kinetic constants for selenate and selenite reduction were estimated to be 2.9 x 10(-11) L/cells/h and 5.5 x 10(-13) L/cells/h, respectively. The yield of the bacterial cells by selenate reduction was estimated to be 2.2 x 10(9) cells/mg-Se.     

Inducible nitric oxide synthase augments injury elicited by oxidative stress in rat cardiac myocytes

The effects of nitric oxide (NO) produced by cardiac inducibleNO synthase (iNOS) on myocardial injury after oxidative stress wereexamined. Interleukin-1 induced cultured rat neonatal cardiac myocytes to express iNOS. After induction of iNOS,L-arginine enhanced NOproduction in a concentration-dependent manner. Glutathione peroxidase(GPX) activity in myocytes was attenuated by elevated iNOS activity andby an NO donor,S-nitroso-N-acetyl-penicillamine (SNAP). Although NO production by iNOS did not induce myocardial injury, NO augmented release of lactate dehydrogenase from myocyte cultures after addition ofH₂O₂(0.1 mM, 1 h). Inhibition of iNOS withN-nitro-L-argininemethyl ester ameliorated the effects of NO-enhancing treatments onmyocardial injury and GPX activity. SNAP augmented the myocardialinjury induced byH₂O₂.Inhibition of GPX activity with antisense oligodeoxyribonucleotide forGPX mRNA increased myocardial injury byH₂O₂.Results suggest that the induction of cardiac iNOS promotes myocardialinjury due to oxidative stress via inactivation of the intrinsicantioxidant enzyme, GPX.

     

Increased surface binding sites of insulin in ML236B (compactin)-resistant mutants of Chinese hamster cell line

Mutants resistant to ML236B (compactin) were isolated from the Chinese hamster lung V79 cell line (1). Three ML236B-resistant mutants, MF-1, MF-2 and MF-3, were enhanced in insulin-specific binding activity about 2 to 3 times over the parental V79 cell lines. Compared to V79, endocytosis of insulin was also increased 2 to 3-fold in ML236B-resistant mutants than V79. Scatchard analysis showed that 5,000 insulin binding sites per cell in V79 and 16,000 in a NL236B-resistant clone, MF-2. Insulin receptors in mutant and parental strains are down-regulated to a similar extent in the parental V79 treated with an excess insulin. This is the first somatic cell mutant with increased surface binding sites for insulin.     

Genetic analysis of a mutation affecting ribosomal protein S1 in Escherichia coli.

Summary Ribosomal protein S1 from a newly isolated Escherichia coli mutant has a molecular weight of about 54,000 which is smaller than the wild type S1 (M.W. 65,000). The isoelectric points of the smaller and the wild type S1 species are similar in the gel electrophoresis system of O'Farrell (1975). Genetic analyses by Hfr conjugation and P1 phage transduction indicate that the mutation affecting S1 (rpsA) is located close to the serC gene [20 min on the E. coli genetic map of Bachmann et al. (1976)], with a co-transduction frequency of 61%. The most probable gene order is serC-rpsA-cmlB.