Glandular Structure Formation of LS174T Human Colon Cancer Cells Cultured with Collagen Gels

LS174T human colon cancer cells formed glandular structures with microvilli, tight junctions, desmosomes and basal laminae arranged in order as in normal intestinal epithelial cells when combined with fetal rat mesenchymes in organ culture. When cultured with type I collagen gel, they also formed glandular structures, but less efficiently than with the mesenchyme. In collagen gel-induced glandular structures, microvilli, tight junctions and desmosomes were arranged in order as in mesenchyme-induced ones, but basal laminae were never observed in contrast with mesenchyme-induced ones. These results indicate that basal lamina formation is not necessary for the glandular structure formation and that mesenchymes promote glandular structure formation of LS174T cells by supplying components necessary for basal lamina formation.     

(+)-5α,9α-dihydroxymatrine,a new lupin alkaloid from Euchresta horsfeldii

A new lupin alkaloid (+)-5α,9α-dihydroxymatrine has been isolated from the leaves of Euchresta horsfeldii (E. formosana cv riukiuensis) together with matrine, matrine N-oxide, sophoranol, sophoranol N-oxide, anagyrine, N-methylcytisine, N-formylcytisine and cytisine.     

Role of p38 mitogen-activated protein kinase (MAPK) for vacuole formation in lipopolysaccharide (LPS)-stimulated macrophages

The role of p38 mitogen-activated protein kinase (MAPK) on vacuole formation in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells was examined. LPS definitely induced the formation of vacuoles in RAW 264.7 cells and SB202190 as a p38 specific inhibitor also induced slight vacuole formation. The simultaneous treatment with LPS and SB202190 induced many more vacuoles in RAW 264.7 cells than the treatment with LPS or SB202190 alone, and the vacuoles were extraordinarily large in size. On the other hand, an inactive inhibitor of p38 MAPK did not augment LPS-induced vacuole formation. Further, the inhibitors of other MAPKs and nuclear factor (NF)-kappaB pathways did not affect it. The extraordinarily large vacuoles in RAW 264.7 cells treated with LPS and SB202190 were possibly formed via fusion of small vacuoles. However, SB202190 did not augment vacuole formation in CpG DNA or interferon (IFN)-gamma-stimulated RAW 264.7 cells. The role of p38 MAPK in the vacuole formation in LPS-stimulated macrophages is discussed.     

Regulation of Aspartate Family Amino Acid Biosynthesis in Brevibacterium flavum

Dihydrodipicolinate (DDP)* synthetase and DDP-reductase were partially purified about 30 and 15 folds, respectively, from sonic extracts of Brevibacterium flavum.

In contrast with DDP-synthetase from Escherichia coli, the B. flavum enzyme was only slightly inhibited by α, ε-diaminopimelate, a precursor of lysine, but not by lysine itself. Single or simultaneous addition of any other amino acid(s) of aspartate family did not affect the activity significantly. Optimum pH for DDP-synthetase was 8.4 with Tris-HCl buffer. Kms for aspartic-β-semialdehyde and pyruvate at pH 7.5 were 2×10^?4m and 1×10^?4m, respectively. The formation of DDP-synthetase was not significantly repressed by lysine.

DDP-reductase of B. flavum required NADH or NADPH as the cofactor. This enzyme was not inhibited by single or simultaneous addition of aspartate family amino acid(s).

From the above results, the regulation mechanism of lysine biosynthesis in B. flavum was discussed.     

Dose limits below which the effect of radiation on health becomes undetectable due to background variation

To clarify the low-dose limit at which the effect of radiation on health becomes undetectable is important in the regulation of radiation. As one of a series of cytogenetical studies on the effect of radiation on health, we present low-dose limits determined by analyzing the background frequencies of translocations in the lymphocytes of people living in normal circumstances. The frequencies of translocations in the lymphocytes were analyzed in 20 non-smokers (61.2-year-old on the average) in a large city, and 16 non-smokers (64.4-year-old on the average) and 8 children (12.3-year-old on the average) in a remote village. The radiation dose was calculated based on the background frequencies of translocations assuming that all the translocations had been induced by radiation. The calculated doses were 384+/-200, 336+/-124 and 128+/-80 mSv in the case of chronic exposure, and 248+/-153, 225+/-104 and 107+/-72 mSv in acute exposure. Standard deviation of the calculated doses is considered to be the dose level below which the effect of radiation becomes undetectable due to the background variation in the effects of all kind of mutagenic factors, i.e., the dose level below which an epidemiological study will not be able to show any significant increase in malignant diseases. The results obtained from epidemiological studies are in fairly good agreement with our results.     

N-acylhomoserine lactone regulates violacein production in Chromobacterium violaceum type strain ATCC 12472

In tests, Chromobacterium violaceum ATCC 12472 produced several N-acyl-L-homoserine lactones (AHLs). Of these, N-(3-hydroxydecanoyl)-L-homoserine lactone was dominant, and controlled violacein production by quorum sensing. Strain VIR07, an AHL-deficient mutant, did not produce violacein. Violacein production in VIR07 was induced by adding long-chain AHLs (C10-C16), but was inhibited by adding short-chain AHLs (C4-C8). Strain VIR07 showed the response of violacein production when AHLs diffused from a variety of AHL-producing bacteria on agar plates, and thus might be a useful biosensor for recognizing exogenous AHLs.     

The trichothecene biosynthesis gene cluster of Fusarium graminearum F15 contains a limited number of essential pathway genes and expressed non-essential genes

We report for the first time the complete structure and sequence of the trichothecene biosynthesis gene cluster (i.e. Tri5-cluster) from Fusarium graminearum F15, a strain that produces 3-acetyldeoxynivalenol (3-ADON). A putative tyrosinase and polysaccharide deacetylase gene flank the Tri5-cluster: the number of pathway genes between them is less than half the total number of steps necessary for 3-ADON biosynthesis. In comparison with partial Tri5-cluster sequences of strains with 15-acetyldeoxynivalenol and 4-acetylnivalenol chemotypes, the Tri5-cluster from strain F15 contains three genes that are apparently unnecessary for the biosynthesis of 3-ADON (i.e. Tri8 and Tri3, which are expressed, and pseudo-Tri13, which is not expressed). In addition, the Tri7 gene was missing from the cluster. Recombinant TRI3 protein showed limited trichothecene C-15 acetylase activity. In contrast, recombinant TRI8 protein displayed no C-3 deacetylase activity, suggesting that the loss or alteration of function contribute directly to the chemotype difference.