Isolation and Structure Elucidation of Growth Inhibitors on Silkworm Larvae from Magnolia kobus DC

Two lignans were isolated from leaves of Magnolia kobus DC. as growth inhibitors on silkworm larvae and structurally elucidated as sesamin (I) and kobusin (II) which has been hitherto unknown.     

Fatty Acid Compositions of Triglyceride and Phospholipid from Candida tropicalis Grown on n-Alkanes

The content of total cellular lipid of Candida tropicalis grown on a mixture of n-alkanes (C₁₀–C₁₈) was about 20% of the dry cell weight at the exponential growth phase and 14% at the early stationary phase. Phospholipid corresponded to approximately 70 % of the total lipid independent of the growth phases. The composition of cellular lipid classes did not change significantly during the growth. On the other hand, a drastic time-course change in fatty acid composition was observed. The proportion of odd-chain fatty acids, one of the most specific cellular components of the yeast grown on the n-alkane mixture, increased in both phospholipid and triglyceride along with the yeast growth. In the meantime, the proportion of polyunsaturated fatty acids varied markedly during the course of cultivation, showing a peak at the early growth phase. The high content of polyunsaturated fatty acids at the early stages of growth correlated to the contents of these acids in phospholipid rather than in triglyceride.     

Biosynthesis of Piericidins A and B by Streptomyces mobaraensis

Biosynthesis of piericidins A and B (PA and PB) has been investigated using ¹⁴C-labeled compounds. Incorporation ratios of dl-methionine(methyl-¹⁴C), propionate-1-¹⁴C and acetate-1-¹⁴C and-2-¹⁴C were 7.4, 4,5, 1.2 and 0.9%, respectively, whereas dl-mevalonic lactone- 2-¹⁴C and formate-¹⁴C were not incorporated. Degradation studies on labeled PA show that in the biosynthesis of piericidins a long branched C₂₃-chain was formed from five propionate and four acetate units and then a nitrogen atom was introduced at the terminal part of the chain, followed by cyclization to form the pyridine ring. The two methoxyl groups on the rings of PA and PB as well as the one in the side chain of PB were derived from S-methyl of methionine.     

Aspochracin,a New Insecticidal Metabolite of Aspergillus ochraceus

A new insecticidal substance named aspochracin was isolated from the culture filtrate of Aspergillus ochraceus, a pathogenic fungus causing muscardine on insects. The compound was found to be a novel cyclotripeptide, composed of N-methyl-l-alanine, N-methyl-l-valine and l-ornithine, containing an octatrienoic acid side chain. Isolation procedure, structural elucidation and biological activities are described in detail.

Hexahydroaspochracin (II) derived on hydrogenation of aspochracin (I), an insecticidal metabolite of Aspergillus ochraceus, was synthesized by cyclization of N-methyl-l-valyl-N- methyl-l-alanyl-α-caprylyl-l-ornithine (XIV). In addition to II, isohexahydroaspochracin (XV) was isolated from the reaction mixture.     

Tumor necrosis factor-alpha and CD95 ligation suppress erythropoiesis in Fanconi anemia C gene knockout mice

Fanconi anemia (FA) is a genetic syndrome predisposing to hematopoietic failure. Little is known about the pathophysiology of FA, except that tumor necrosis factor-alpha (TNF-alpha) is overexpressed in patients. FA group C (Fac) gene knockout mice have been developed in order to model the human disease, but the mice do not spontaneously exhibit aplasia. To investigate secondary influences on hematopoiesis in the Fac-null mice, we studied the sensitivity of hematopoietic progenitor cells (HPC) to death receptor triggering by TNF-alpha and Fas receptor (CD95) ligation. Previously we had found that overexpression of a human FAC transgene protects hematopoietic progenitors from Fas-mediated apoptosis (Wang et al., 1998, Cancer Res 58:3538-3541). In the present experiments with Fac-null mice, growth of erythroid burst-forming units (BFU-E) was significantly inhibited by TNF-alpha and CD95 ligation. Flow cytometric analysis revealed that CD95 was induced more readily in the Fac-null CD34+ cell fraction. Apoptosis induced by TNF-alpha alone or with CD95 ligation also occurred more frequently in null mouse HPC. We then bred null mice against transgenic mice overexpressing TNF-alpha (at serum levels in the range of 100 pg/ml). Resultant Fac-null mice that overexpressed TNF-alpha not only yielded decreased numbers of BFU-E but also expressed higher levels of CD95 in the CD34+ fraction. We conclude that mutation in the Fac protein induces heightened sensitivity to TNF-alpha and Fas receptor ligation, results that may explain the mechanism of anemia in FA-C patients.     

Rapid detection of quinolone-resistant Salmonella by real time SNP genotyping

A total of 63 isolates were screened for the gyrA mutation (87Asp-Tyr) in Salmonella enterica serovars using real time PCR. All of the isolates were successfully identified as resistant or susceptible, consistent with the MIC result of the agar dilution method and gyrA sequencing.     

Pressure activates rat pancreatic stellate cells

Pancreatic stellate cells (PSCs) play a central role in development of pancreatic fibrosis. In chronic pancreatitis, pancreatic tissue pressure is higher than that of the normal pancreas. We here evaluate the effects of pressure on the activation of rat PSCs. PSCs were isolated from the pancreas of Wistar rat using collagenase digestion and centrifugation with Nycodenz gradient. Pressure was applied to cultured rat PSCs by adding compressed helium gas into the pressure-loading apparatus to raise the internal pressure. Cell proliferation rate was assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation. MAPK protein levels and alpha-smooth muscle actin (alpha-SMA) expression were evaluated by Western blot analysis. Concentration of activated transforming growth factor-beta1 (TGF-beta1) secreted from PSCs into culture medium was determined by ELISA. Collagen type I mRNA expression and collagen secretion were assessed by quantitative PCR and Sirius red dye binding assay, respectively. Application of pressure significantly increased BrdU incorporation and alpha-SMA expression. In addition, pressure rapidly increased the phosphorylation of p44/42 and p38 MAPK. Treatment of PSCs with an MEK inhibitor and p38 MAPK inhibitor suppressed pressure-induced cell proliferation and alpha-SMA expression, respectively. Moreover, pressure significantly promoted activated TGF-beta1 secretion, collagen type I mRNA expression, and collagen secretion. Our results demonstrate that pressure itself activates rat PSCs and suggest that increased pancreatic tissue pressure may accelerate the development of pancreatic fibrosis in chronic pancreatitis.