Mapping quantitative trait loci affecting circadian photosensitivity in retinally degenerate mice

It is known that retinally degenerate C57BL/6J (rd/rd) mice have unattenuated circadian photosensitivity. However, the authors have previously found that CBA/J (rd/rd) mice that carry the same rd mutation have attenuated circadian photosensitivity compared to normal CBA/N (+/+) mice. In the present study, a quantitative trait locus (QTL) analysis using C57BL/6J (rd/rd) and CBA/J (rd/rd) mice was conducted in order to identify the genes affecting circadian photosensitivity of the rd mice. As a result, several putative QTLs onthree separate chromosomes (8, 12, 17) were detected, which indicates that circadian photosensitivity in rd mice is altered by multiple genes. Identification of these genes may provide new insights into the understanding of regulation of circadian photoentrainment and sleep-wake disorders.     

A role of heparin-binding epidermal growth factor-like growth factor in cardiac remodeling after myocardial infarction

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is known to induce cell growth in various cell types via transactivation of epidermal growth factor receptor (EGFR). To investigate the involvement of HB-EGF and EGFR in cardiac remodeling after myocardial infarction (MI), we examined the expressions of mRNA and protein in rat hearts 6 weeks after MI-induction. Where increased expressions of HB-EGF mRNA and protein were observed, infarcted myocardium was replaced by extracellular matrix and interstitial fibroblasts. EGFR mRNA and protein expression did not show significant changes in sham-operated heart tissues, non-infarcted region, and infarcted region. In vitro study demonstrated that HB-EGF mRNA was expressed mainly in cultured fibroblasts rather than in myocytes. We suggest that the interaction between HB-EGF and EGFR transactivation is closely related to the proliferation of cardiac fibroblasts and cardiac remodeling after MI in an autocrine, paracrine, and juxtacrine manner.     

Cloning and Molecular Analysis of Poly(3-Hydroxyalkanoate) Biosynthesis Genes in Pseudomonas aureofaciens

Pseudomonas aureofaciens grown on octanoate or gluconate synthesized medium-chain-length polyhydroxyalkanoates (mcl-PHAs). To clone the PHA synthase gene(s) (phaC), the genomic library of P. aureofaciens was constructed using a cosmid vector. The recombinant cosmids that clone phaC were detected by the complementation with a PHA-negative mutant, P. putida GPp104. The resulting recombinant cosmid, named pVK6, contained a 13-kbp DNA insert. Genetic analysis of the pha locus in pVK6 revealed the presence of six ORFs, genes encoding two PHA synthases, 1 and 2 (phaC1 and phaC2), PHA depolymerase (phaZ), two PHA granule-associated proteins (phaF and phaI), and an unknown protein (phaD). The heterologous expression of pha genes from P. aureofaciens was confirmed. P. putida GPp104 regained the ability to accumulate PHA on introduction of pVK6. Wild-type strains P. oleovorans and P. fluorescens, which were unable to accumulate PHA when grown on gluconate, acquired the ability to accumulate PHA from gluconate when they possessed pVK6. Received: 10 January 2001 / Accepted: 7 June 2001     

Phosphatidylglycerol is essential for the development of thylakoid membranes in Arabidopsis thaliana

Phosphatidylglycerol is a ubiquitous phospholipid in the biological membranes of many organisms. In plants, phosphatidylglycerol is mainly present in thylakoid membranes and has been suggested to play specific roles in photosynthesis. Here, we have isolated two T-DNA tagged lines of Arabidopsis thaliana that have a T-DNA insertion in the PGP1 gene encoding a phosphatidylglycerolphosphate synthase involved in the biosynthesis of phosphatidylglycerol. In homozygous plants of the T-DNA tagged lines, the PGP1 gene was completely disrupted. The growth of these knockout mutants was dependent on the presence of sucrose in the growth medium, and these plants had pale yellow-green leaves. The leaves of the mutants had remarkably large intercellular spaces due to the reduction in the number of mesophyll cells. The development of chloroplasts in the leaf cells was severely arrested in the mutants. Mesophyll cells with chloroplast particles are only found around vascular structures, whereas epidermal cells are enlarged but largely conserved. The content of phosphatidylglycerol in the mutants was reduced to 12% of that of the wild type. These results demonstrate that PGP1 plays a major role in the biosynthesis of phosphatidylglycerol in chloroplasts, and that phosphatidylglycerol is essential for the development of thylakoid membranes in A. thaliana.     

Effects of dietary medium-chain triacylglycerols on serum lipoproteins and biochemical parameters in healthy men

The objective of this study was to investigate effects of dietary medium-chain triacylglycerols (MCTs) on serum lipid levels, liver function, and hepatic fat accumulations in healthy men. Eleven subjects consumed 2200-2600 kcal daily, of which 70-80 g was fat; the fat included 40 g of MCTs or else 40 g of long-chain triacylglycerols (blended vegetable oil). The diet was followed for 4 weeks in this controlled double-blind study. At the end of the experiment, significant differences were not found in the concentrations of serum total cholesterol, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, and high density lipoprotein cholesterol between the groups. Serum triglycerol levels were not significantly different in the groups. Adverse effects from ingestion of MCTs on liver functions, the liver-to-spleen ratio on computed tomography (an index of fatty liver), or results of blood tests were not seen. The results suggest that the long-term effects of dietary MCTs on serum cholesterol were similar to those of unsaturated fatty acids found abundantly in vegetable oil, and that consumption of MCTs in the amount of 40 g/day for a month does not cause liver fat accumulation or liver dysfunction.     

Requirement of phosphatidylglycerol for maintenance of photosynthetic machinery

Phosphatidylglycerol (PG) is a ubiquitous component of thylakoid membranes. Experiments with the pgsA mutant of the cyanobacterium Synechocystis sp. PCC6803 defective in biosynthesis of PG have demonstrated an indispensable role of PG in photosynthesis. In the present study, we have investigated the light susceptibility of the pgsA mutant with regard to the maintenance of the photosynthetic machinery. Growth of the mutant cells without PG increased the light susceptibility of the cells and resulted in severe photoinhibition of photosynthesis upon a high-light treatment, whereas the growth in the presence of PG was protected against photoinhibition. Photoinhibition induced by PG deprivation was mainly caused by an impairment of the restoration process. The primary target of the light-induced damage in thylakoid membranes, the D1 protein of photosystem (PS) II was, however, synthesized and degraded with similar rates irrespective of whether the mutant cells were incubated with PG or not. Intriguingly, it was found that instead of the synthesis of the D1 protein, the dimerization of the PSII core monomers was impaired in the PG-deprived mutant cells. Addition of PG to photoinhibited cells restored the dimerization capacity of PSII core monomers. These results suggest that PG plays an important role in the maintenance of the photosynthetic machinery through the dimerization and reactivation of the PSII core complex.     

Biosynthesis of 5-alkylresorcinol in rice: incorporation of a putative fatty acid unit in the 5-alkylresorcinol carbon chain

A previously unspecified "starter" unit in the predicted biosynthesis pathway of 5-alkylresorcinols has now identified as a fatty acid or its equivalent, using an efficient 5-alkylresorcinol production system of etiolated rice seedlings. Feeding saturated, odd-carbon fatty acid ester substrates from C11 to C19 specifically and markedly increased the amount of the corresponding 5-alkylresorcinol homologs with even-carbon chains that are shorter by one carbon than those of the supplied fatty acids. The amount of these homologs depended on substrate concentration. Some of the homologs whose amounts increased had linear carbon chains and the dodecyl homolog was shown to be 5-n-dodecylresorcinol. Moreover, the 13C label in the dodecyl homolog that was biosynthesized from the [1-13C]tridecanoate substrate was localized on the C-5 carbon of the resorcinol ring. These results obviously show that the fatty acid unit acts as a direct precursor and forms the side-chain moiety of 5-n-alkylresorcinol via the predicted biosynthesis pathway.     

Correlation between expression of oncogene products and resistance to anticancer drugs in cultured ovarian cancer cell lines

Despite recent advances in the application of chemotherapy to ovarian cancer, the development of alternative therapies that retain activity against drug-resistant-tumors remains a high priority. We analyzed a number of cultured ovarian cancer cell lines of different tissue types for the presence or absence of sensitivity to various anticancer drugs as well as expression patterns of oncogene products (erbB-2, EGFR, bcl-2). As a result, we identified oncogene products that were related to resistance. Using 9 cultured cell lines of ovarian cancers (serous, mucinous, endometrioid, clear, undifferentiated), sensitivities to anticancer drugs were investigated using the MTT assay. The phenotypes of oncogene products expressed by the above cultured cell lines were analyzed by Western blotting. The oncogene products involved in resistance to anticancer drugs were identified by multivariate analysis. Positive correlation between the resistance to anticancer drugs and the oncogene products was obtained by multivariate analysis for (a) CDDP and erbB-2 (b) x p-16 and erbB-2, and (c) MMC and EGFR. Correlation between resistance to anticancer drugs and expression of certain oncogene products was obtained in ovarian cancers, suggesting that sensitivity to anticancer drugs could be predicated prior to chemotherapy.     

Putative homologs of SSK22 MAPKK kinase and PBS2 MAPK kinase of Saccharomyces cerevisiae encoded by os-4 and os-5 genes for osmotic sensitivity and fungicide resistance in Neurospora crassa

We cloned and characterized Neurospora NcSSK22 and NcPBS2 genes, similar to yeast SSK22 mitogen-activated protein (MAP) kinase kinase kinase and the PBS2 MAP kinase kinase genes, respectively. Disruptants of the NcSSK22 gene were sensitive to osmotic stress and resistant to iprodione and fludioxonil. Their phenotypes were similar to those of osmotic-sensitive (os) mutants os-1, os-2, os-4, and os-5. The os-4 mutant strain transformed with the wild-type NcSSK22 gene grew on a medium containing 4% NaCl and was sensitive to iprodione and fludioxonil. In contrast, the NcPBS2 gene complemented the osmotic sensitivity and fungicide resistance of the os-5 mutant strain. We sequenced the NcPBS2 gene of the os-5 mutant strain (NM216o) and found five nucleotides deleted within the kinase domain. This result suggests that the gene products of os-4 and os-5 are components of the MAP kinase cascade, which is probably regulated upstream by two-component histidine kinase encoded by the os-1/nik1 gene.