Anterograde Axonal Transport of Peptidylglycine α-Amidating Monooxygenase in Rat Sciatic Nerves

Axonal transport of peptidylglycine alpha-amidating monooxygenase (PAM) activity was studied in rat sciatic nerves from 12 to 120 h after double ligations. The anterograde axonal transport increased and reached a plateau between 48 and 72 h and then decreased. The flow rate was 100 mm/day, and the molecular mass of the active entity was 70 kDa, which was determined by gel filtration. In contrast, there was no evidence for significant retrograde axonal transport. Anterograde axonal transport of immunoreactive cholecystokinin, a carboxy-terminal-amidated putative neuropeptide, was also found. These results suggest that PAM is transported by a rapid axonal flow and may play a role as a processing enzyme during transport or in the terminals of rat sciatic nerves.     

Mitochondrial DNA haplogrouping of the brown bear,Ursus arctos (Carnivora: Ursidae) in Asia,based on a newly developed APLP analysis

Sequence analyses of the complete brown bear, Ursus arctos, mitochondrial DNA (mtDNA) genome have detected scattered single nucleotide polymorphisms (SNPs) that define distinct mtDNA haplogroups in phylogeographical studies. The degraded DNA in historical samples, such as stuffed or excavated specimens, however, is often not suitable for sequence analyses. To address this problem, we developed an amplified product length polymorphism (APLP) analysis for mtDNA‐haplogrouping U. arctos specimens by detecting haplogroup‐specific SNPs. We verified the validity and utility of this method by analysing up to 170‐year‐old skin samples from U. arctos specimens collected widely across continental Eurasia. We detected some of the same haplogroups as those occurring in eastern Hokkaido (Japan) and eastern Alaska in continental Eurasia (the Altai and the Caucasus). Our results show that U. arctos in eastern Hokkaido and eastern Alaska descended from a common ancestor in continental Eurasia, and suggest that U. arctos occupied several refugia in southern Asia during the Last Glacial Maximum. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 627–635.     

Heterogeneity of intercellular adhesion in rat liver cells in culture

The intercellular homotypic adhesive properties of 14 clones derived from a nontumorigenic rat liver epithelial cell line (LEC), derived from neonatal Fischer rats, were examined and compared to those of the hepatoma H4-II-E cell line. Each clone was assayed also for the degree of chromosomal aneuploidy and the ability to grow in soft agar. Over 100-fold differences in adhesive properties were observed among the clones, but no correlation was observed between the degree of aneuploidy in the clones and intercellular adhesive properties. The parent LEC cell line and the clones derived from it were unable to grow in soft agar. The H4-II-E cells showed negligible capacity to reaggregate after dissociation into single cells and these cells readily formed colonies in soft agar. Many of the LEC clones were similar to the H4-II-E cells in their adhesive properties, which suggests that reduced cell-to-cell adhesiveness per se is not a necessary prerequisite of epithelial cells to be able to grow independent of anchorage. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) of concanavalin A (Con A)-binding glycoproteins in the "most adhesive" clone 67 and the "least adhesive" clone 201 showed markedly elevated amounts of acidic 105 and 67-kDa glycoproteins in clone 67. Proteins with similar migration patterns in 2D-PAGE have previously been reported to participate in specific homotypic intercellular adhesion of liver cells. The Con A-binding glycoprotein pattern in H4-II-E cells was markedly different from that of LEC cells with a set of six proteins missing and nine proteins appearing new in the H4-II-E cells. It is suggested that, in addition to identifying known epithelial cell polypeptides, systematic screening of cell surface-associated glycoproteins in normal and transformed epithelial cells in vitro and in vivo may lead to identification of novel polypeptides intimately associated with the transformed phenotype.     

Two distinct O-methyltransferases in aflatoxin biosynthesis

The substances belonging to the sterigmatocystin group bear a close structural relationship to aflatoxins. When demethylsterigmatocystin (DMST) was fed to Aspergillus parasiticus NIAH-26, which endogenously produces neither aflatoxins nor precursors in YES medium, aflatoxins B1 and G1 were produced. When dihydrodemethylsterigmatocystin (DHDMST) was fed to this mutant, aflatoxins B2 and G2 were produced. Results of the cell-free experiment with S-adenosyl-[methyl-3H]methionine showed that first the C-6-OH groups of DMST and DHDMST are methylated to produce sterigmatocystin and dihydrosterigmatocystin (O-methyltransferase I) and then the C-7-OH groups are methylated to produce O-methylsterigmatocystin (OMST) and dihydro-O-methylsterigmatocystin (DHOMST) (O-methyltransferase II). However, no methyltransferase activity was observed when either OMST, DHOMST, 5,6-dimethoxysterigmatocystin, 5-methoxysterigmatocystin, or sterigmatin was incubated with the cell extract. Treatment of the cell extract with N-ethylmaleimide inhibited O-methyltransferase I activity but not that of O-methyltransferase II. Furthermore, these O-methyltransferases were different in their protein molecules and were involved in both the reactions from DMST to OMST and DHDMST to DHOMST. The reactions described in this paper were not observed when the same mold had been cultured in YEP medium.     

Selective growth of a mutant in continuous culture of Bacillus caldolyticus for production of α-amylase

Summary In a continuous culture of Bacillus caldolyticus strain SP, which requires maltose as an inducer for production of -amylase in batch culture, a predominant mutant strain M1 which produced high amounts of -amylase in the absence of maltose in batch culture, developed. The change of cell population from strain SP to strain M1 in maltose-casitone medium was linear with time in the transient state after the change from batch to continuous culture at a dilution rate of 0.17 h^-1, and was completed in about 11 generations of bacterial growth. The dilution rate effect of continuous culture on -amylase activity was almost the same with both strains SP and M1. The maximum -amylase activity of 380 units/ml was observed at an intermediate dilution rate that was 11.5 times higher than -amylase activity at the end of a batch culture using the same medium. It was deduced that the enhancement of -amylase production in continuous culture was attributed partly to the predominant growth of a mutant strain with higher -amylase productivity.     

Two distinct O-methyltransferases in aflatoxin biosynthesis.

The substances belonging to the sterigmatocystin group bear a close structural relationship to aflatoxins. When demethylsterigmatocystin (DMST) was fed to Aspergillus parasiticus NIAH-26, which endogenously produces neither aflatoxins nor precursors in YES medium, aflatoxins B1 and G1 were produced. When dihydrodemethylsterigmatocystin (DHDMST) was fed to this mutant, aflatoxins B2 and G2 were produced. Results of the cell-free experiment with S-adenosyl-[methyl-3H]methionine showed that first the C-6-OH groups of DMST and DHDMST are methylated to produce sterigmatocystin and dihydrosterigmatocystin (O-methyltransferase I) and then the C-7-OH groups are methylated to produce O-methylsterigmatocystin (OMST) and dihydro-O-methylsterigmatocystin (DHOMST) (O-methyltransferase II). However, no methyltransferase activity was observed when either OMST, DHOMST, 5,6-dimethoxysterigmatocystin, 5-methoxysterigmatocystin, or sterigmatin was incubated with the cell extract. Treatment of the cell extract with N-ethylmaleimide inhibited O-methyltransferase I activity but not that of O-methyltransferase II. Furthermore, these O-methyltransferases were different in their protein molecules and were involved in both the reactions from DMST to OMST and DHDMST to DHOMST. The reactions described in this paper were not observed when the same mold had been cultured in YEP medium.     

Enzymatic conversion of norsolorinic acid to averufin in aflatoxin biosynthesis

5'-Hydroxyaverantin (HAVN) was isolated from a mold, Emericella heterothallica IFO 30842. Aspergillus parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4, produced neither aflatoxins nor precursors in yeast extract-sucrose (YES) medium. When the postmicrosome (cytosol) fraction of NIAH-26, which had been prepared from the culture in YES medium, was incubated with norsolorinic acid (NA) in the presence of NADH or NADPH, averantin (AVN) was produced. The reverse reaction from AVN to NA was promoted by the addition of NAD or NADP (dehydrogenase reaction). When the microsome fraction of NIAH-26 was incubated with AVN, HAVN was produced in the presence of NADPH (monooxygenase reaction). HAVN was, furthermore, oxidized to averufin (AVR) by the cytosol fraction of NIAH-26 in the presence of NAD or NADP (dehydrogenase reaction). In the feeding experiments with A. parasiticus NIAH-26, aflatoxins were produced from AVN, HAVN, NA, and AVR but not from averufanin or averythrin. These results indicate that the reaction sequence NA in equilibrium AVN----HAVN----AVR is involved in the biosynthetic pathway of aflatoxins. The enzyme activities described here were dependent on the culture medium, and no enzyme activities were observed in the nonaflatoxigenic strain A. oryzae SYS-2 (IFO 4251).     

Biosynthetic relationship among aflatoxins B1, B2, G1, and G2.

Aspergillus parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4 (NRRL 2999), produces neither aflatoxins nor precursors. When sterigmatocystin (ST) or O-methylsterigmatocystin was fed to this mutant in YES medium, aflatoxins B1 (AFB1) and G1 (AFG1) were produced. When dihydrosterigmatocystin (DHST) or dihydro-O-methylsterigmatocystin was fed to this mold, aflatoxins B2 (AFB2) and G2 (AFG2) were produced. The reactions from ST to AFB1 and DHST to AFB2 were also observed in the cell-free system and were catalyzed stepwise by the methyltransferase and oxidoreductase enzymes. In the feeding experiments of strain NIAH-26, the convertibility from ST to AFB1-AFG1 was found to be remarkably suppressed by the coexistence of DHST in the medium, and the convertibility from DHST to AFB2-AFG2 was also suppressed by the presence of ST. When some other mutants which endogenously produce a small amount of aflatoxins (mainly AFB1 and AFG1) were cultured with DHST, the amounts of AFB1 and AFG1 produced were significantly decreased, whereas AFB2 and AFG2 were newly produced. In similar feeding experiments in which 27 kinds of mutants including these mutants were used, most of the mutants which were able to convert exogenous ST to AFB1-AFG1 were also found to convert exogenous DHST to AFB2-AFG2. These results suggest that the same enzymes may be involved in the both biosynthetic pathways from ST to AFB1-AFG1 and DHST to AFB2-AFG2. The reactions described herein were not observed when the molds had been cultured in the YEP medium.     

Enhanced formation of mouse hybridomas without hat treatment in a serum-free medium

Summary A newly developed, serum-free medium (NYSF-404) selects for antibody-producing hybridomas after fusion of antigen-sensitized mouse spleen cells with myeloma cell lines P3-X63-Ag8-U1 (P3-U1), P3-X63-Ag8-6.5.3 (Ag8.653), or P3-NSI/1-Ag4-1 (NS-1). Without the need for hypoxanthine-aminopterinthymidine (HAT) selection of hybrid cells, frequency of hybridoma formation in medium NYSF-404 is higher (twice) than that in serum- and HAT-containing medium. Colonies developed upon limiting dilution in the presence of the mortal parent myeloma cells in medium NYSF-404 and pure culture of antibody-secreting cells could be subsequently established. The results suggest that fusions can be done in serum-free medium and that the clonal growth of hybridomas is dependent on factors produced by parent myeloma cells under serum-free culture conditions. Such factors seem deficient in serum- and HAT-containing medium or are masked by serum.