Separation of an ε-poly-L-lysine derivative by solvent extraction under a controlled interfacial potential difference

This paper describes the availability of a 1,2-dichloroethane (DCE)-water (W) interfacial system under a controlled interfacial potential difference for the separation of polycationic species. The system was applied to the production of polyethylene glycol-modified ε-poly-L-lysine (PEG-εPL). PEG-εPL is produced by a fermentation process, and the crude product contains a significant amount of non-modified εPL, which is hardly separated by conventional chromatographic techniques. Both εPL species exist in fully protonated forms under certain acidic conditions, and an extractant, dibenzo-18-crown-6 (DB18C6), associates with their ammonium groups to stabilize the polycations in DCE. Despite the polydispersity of the samples, the εPL and crude PEG-εPL give well-defined cyclic voltammetric waves due to the DB18C6-assisted transfer of the polycations at the polarizable DB18C6 (DCE) | (W, pH ~ 3) interface with midpoint potentials useful for a rough prediction of ion partition equilibria. Thus, the partition experiment was performed using the DB18C6, Bu4N[(CF3SO2)2N] (DCE) | crude PEG-εPL, Li[(CF3SO2)2N] (W, pH ~ 3) interfacial system, of which the potential difference was controlled to enable selective extraction of polycationic PEG-εPL by partition of the [(CF3SO2)2N]- ion. The extract could be collected from the DCE phase and was found to consist of highly purified PEG-εPL.

Peptide epimerase-dehydratase complex responsible for biosynthesis of the linaridin class ribosomal peptides

Grisemycin, salinipeptin, and cypemycin belong to the linaridin class of ribosomally synthesized and posttranslationally modified peptides that contain multiple dehydrobutyrine and D-amino acid residues. The biosynthetic gene clusters of these linaridins lack obvious candidate genes for the dehydratase and epimerase required to introduce dehydrobutyrine and D-amino acid residues, respectively. However, we previously demonstrated that the grisemycin (grm) cluster contained cryptic dehydratase and epimerase genes by heterologous expression of this biosynthetic gene cluster in Streptomyces lividans and proposed that two genes (grmH and grmL) with unknown functions catalyze dehydration and epimerization reactions. In this study, we confirmed that both GrmH and GrmL, which were shown to constitute a protein complex by a co-purification experiment, were required to catalyze the dehydration, epimerization, and proteolytic cleavage of a precursor peptide GrmA by in vivo experiments. Furthermore, we demonstrated that GrmH/GrmL complex accepted salinipeptin and cypemycin precursor peptides, which possess three additional amino acids.

Constitutive and high gene expression in the diaminopimelate pathway accelerates ε-poly-L-lysine production in Streptomyces albulus

Streptomyces albulus NBRC14147 produces a homopoly(amino acid), ε-poly-L-lysine (ε-PL). Due to its antibiotic activity, thermostability, biodegradability, and non-toxicity to humans, ε-PL is used as a food preservative. In this study, homology searches of diaminopimelate (DAP) pathway genes (dapB and dapE), in an S. albulus genome database, were shown to encode predicted enzymes using dapB or dapE in Escherichia coli strain complementation assays. We observed that dapB and dapE transcriptional levels were weak during ε-PL production stages. Therefore, we strengthened this expression using an ermE constitutive promoter. Engineered strains generated faster growth and ε-PL production rates when compared with the control strain. Moreover, maximum ε-PL yields in S. albulus, where dapB was constitutively expressed, were approximately 14% higher when compared with the control strain. These findings showed that enhanced lysine biosynthetic gene expression generated faster and higher ε-PL production levels.

N-Formimidoylation/-iminoacetylation modification in aminoglycosides requires FAD-dependent and ligand-protein NOS bridge dual chemistry

Oxidized cysteine residues are highly reactive and can form functional covalent conjugates, of which the allosteric redox switch formed by the lysine-cysteine NOS bridge is an example. Here, we report a noncanonical FAD-dependent enzyme Orf1 that adds a glycine-derived N-formimidoyl group to glycinothricin to form the antibiotic BD-12. X-ray crystallography was used to investigate this complex enzymatic process, which showed Orf1 has two substrate-binding sites that sit 13.5 Å apart unlike canonical FAD-dependent oxidoreductases. One site could accommodate glycine and the other glycinothricin or glycylthricin. Moreover, an intermediate-enzyme adduct with a NOS-covalent linkage was observed in the later site, where it acts as a two-scissile-bond linkage facilitating nucleophilic addition and cofactor-free decarboxylation. The chain length of nucleophilic acceptors vies with bond cleavage sites at either N-O or O-S accounting for N-formimidoylation or N-iminoacetylation. The resultant product is no longer sensitive to aminoglycoside-modifying enzymes, a strategy that antibiotic-producing species employ to counter drug resistance in competing species.

The Assembly-Line Enzymology of Nonribosomal Peptide Biosynthesis

Peptide natural products constitute a major class of secondary metabolites produced by microorganisms (mostly bacteria and fungi). In the past several decades, researchers have gained extensive knowledge about nonribosomal peptides (NRPs) generated by ribosome-independent systems, namely, NRP synthetases (NRPSs). NRPSs are multifunctional enzymes consisting of semiautonomous domains that form a peptide backbone. Using a thiotemplate mechanism that employs assembly-line logic with multiple modules, NRPSs activate, tether, and modify amino acid building blocks, sequentially elongating the peptide chain before releasing the complete peptide. Adenylation, thiolation, condensation, and thioesterase domains play central roles in these reactions. This chapter focuses on the current understanding of these central domains in NRPS assembly-line enzymology.

Mechanism of S-Adenosyl-l-methionine C-Methylation by Cobalamin-dependent Radical S-Adenosyl-l-methionine Methylase in 1-Amino-2-methylcyclopropanecarboxylic Acid Biosynthesis

The radical S-adenosyl-l-methionine (SAM) methylase Orf29 catalyzes the C-methylation of SAM in the biosynthesis of 1-amino-2-methylcyclopropanecarboxylic acid. Here, we determined that the methylation product is (4″R)-4″-methyl-SAM. Furthermore, we found that the 5'-deoxyadenosyl radical generated by Orf29 abstracts the pro-R hydrogen atom from the C-4″ position of SAM to generate the radical intermediate, which reacts with methylcobalamin to give (4″R)-4″-methyl-SAM. Consequently, the Orf29-catalyzed C-methylation was confirmed to proceed with retention of configuration.

Off-Loading Mechanism of Products in Polyunsaturated Fatty Acid Synthases

Marine microorganisms de novo biosynthesize polyunsaturated fatty acids such as docosahexaenoic acid and eicosapentaenoic acid by polyunsaturated fatty acid (PUFA) synthases composed of three or four polypeptides in a manner similar to fatty acid synthases (FASs). FASs usually possess thioesterase (TE) domains to release free fatty acids from acyl carrier protein (ACP)-tethered intermediates. Here, we investigated the off-loading mechanism with microalgal and bacterial PUFA synthases through in vivo and in vitro experiments. The in vitro experiments with acyltransferase (AT)-like domains and acyl-ACP substrates clearly demonstrated that the AT-like domains catalyzed the hydrolysis of acyl-ACPs to yield free fatty acids.

In vitro characterization of MitE and MitB: Formation of N-acetylglucosaminyl-3-amino-5-hydroxybenzoyl-MmcB as a key intermediate in the biosynthesis of antitumor antibiotic mitomycins

Mitomycins, produced by several Streptomyces strains, are potent anticancer antibiotics that comprise an aziridine ring fused to a tricyclic mitosane core. Mitomycins have remarkable ability to crosslink DNA with high efficiency. Despite long clinical history of mitomycin C, the biosynthesis of mitomycins, especially mitosane core formation, remains unknown. Here, we report in vitro characterization of three proteins, MmcB (acyl carrier protein), MitE (acyl AMP ligase), and MitB (glycosyltransferase) involved in mitosane core formation. We show that 3-amino-5-hydroxybenzoic acid (AHBA) is first loaded onto MmcB by MitE at the expense of ATP. MitB then catalyzes glycosylation of AHBA-MmcB with uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) to generate a key intermediate, GlcNAc-AHBA-MmcB, which contains all carbon and nitrogen atoms of the mitosane core. These results provide important insight into mitomycin biosynthesis.

Control Mechanism for cis Double-Bond Formation by Polyunsaturated Fatty-Acid Synthases

Polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) are essential fatty acids for humans. Some microorganisms biosynthesize these PUFAs through PUFA synthases composed of four subunits with multiple catalytic domains. These PUFA synthases each create a specific PUFA without undesirable byproducts, even though the multiple catalytic domains in each large subunit are very similar. However, the detailed biosynthetic pathways and mechanisms for controlling final-product profiles are still obscure. In this study, the FabA-type dehydratase domain (DH_FabA ) in the C-subunit and the polyketide synthase-type dehydratase domain (DH_PKS ) in the B-subunit of ARA synthase were revealed to be essential for ARA biosynthesis by in vivo gene exchange assays. Furthermore, in vitro analysis with truncated recombinant enzymes and C₄ - to C₈ -acyl ACP substrates showed that ARA and EPA synthases utilized two types of DH domains, DH_PKS and DH_FabA , depending on the carbon-chain length, to introduce either saturation or cis double bonds to growing acyl chains.

Promotion Effect of Streptothricin on a Glucose Oxidase Enzymatic Reaction and Its Application to a Colorimetric Assay

Previously, we reported that ε-poly-L-lysine (25 - 35 residues) significantly promoted a glucose oxidase enzymatic (GOx) reaction using ferricyanide ion as the oxidant, and that the effect was due to the formation of a polyion complex between anionic GOx and protonated (polycationic) ε-poly-L-lysine. Here, we show that streptothricins (STs), which have an L-β-lysine oligomer (1 - 7 residues) and possess only several positive charges at most, also effectively promote the GOx enzymatic reaction. Interestingly, the promotion effect increased with the size of the lysine oligomer of STs, suggesting that the ionic valence is a key factor determining the degree of the promotion effect. The GOx enzymatic reaction is accompanied by a color change due to the reduction of yellow ferricyanide ion to a colorless reductant. A more distinctive color change can be achieved by the addition of Fe(III) ions due to the formation of Prussian blue. Thus, the promotion effect allowed for colorimetric detection of STs at the 1 mg/L level. The detection method was simple and easy to carry out, and would become a helpful tool for the detection of STs.

Separation of Streptothricin Antibiotics from Culture Broth with Colorimetric Determination Using Dipicrylamine

Our earlier method for the detection and separation of ε-poly-L-lysine using a yellow anionic dye, the dipicrylamine (DPA^-) anion, was herein optimized for streptothricin antibiotics (ST), which contains the β-lysine oligopeptides moiety, H-[NH-(CH₂)₃-CH(NH₂)-CH₂-CO]_n-. We then applied this method to the detection and separation of ST in a commercially available nourseothricin, a mixture of ST species with n = 1, 2, 3, and 4. The ST species were precipitated with the DPA- anion. The precipitate was found to consist of the salts of the fully protonated ST species, ST^z+ (z = n + 1), with the DPA^- anion. The ST(DPA)_z precipitate was re-dissolved in acetonitrile. The solution was yellowish, and gave an absorption maximum at around 420 nm. Thus, the equivalent concentration of the ST species referred to the charge numbers of ST^z+ can be determined colorimetrically. By the addition of bis(triphenylphosphoranylidene)ammonium chloride, the ST species could be re-precipitated from the acetonitrile solution as hydrochloride salts. All of the ST species were found in the precipitate with high yields. The method was thus successfully applied to the detection and separation of ST species from the culture broth.

Functional analysis of methyltransferases participating in streptothricin-related antibiotic biosynthesis

Streptothricin (ST) and its related compounds produced by Streptomyces strains are broad-spectrum antibiotics that consist of carbamoylated d-gulosamine, amino-acid side chain, and streptolidine lactam moieties. BD-12, a streptothricin-related antibiotic, has a glycine-derived side chain and two N-methyl groups, whereas ST-F carrying the l-β-lysine side chain has no methyl group. In our previous studies, we identified and characterized the BD-12 and ST biosynthetic gene clusters. Here we report the functional analysis of two methyltransferase genes (orf 6 and orf 13) in the BD-12 biosynthetic gene cluster. Combinatorial biosynthesis using these two methyltransferase genes and the ST biosynthetic gene cluster resulted in the production of three methylated forms of ST-F. Among them, N,N'-dimethyl-ST-F, a novel compound generated in the present study, showed bacteria-specific antibiotic activities, although ST-F exhibits antibiotic activities against both prokaryotes and eukaryotes. Our findings also demonstrated that the orf 6 and orf 13 genes are responsible for the N-methylations of the amide bonds in the streptolidine lactam and in the amino-acid side chain linkage, respectively, and that N-methyl modification of the streptolidine lactam confers resistance in part against an ST hydrolase, SttH.

Colorimetric Detection of the Adenylation Activity in Nonribosomal Peptide Synthetases

Nonribosomal peptide synthetases (NRPSs) are multifunctional enzymes consisting of catalytic domains. The substrate specificities of adenylation (A) domains determine the amino-acid building blocks to be incorporated during nonribosomal peptide biosynthesis. The A-domains mediate ATP-dependent activation of amino-acid substrates as aminoacyl-O-AMP with pyrophosphate (PPi) release. Traditionally, the enzymatic activity of the A-domains has been measured by radioactive ATP-[(32)P]-PPi exchange assays with the detection of (32)P-labeled ATP. Recently, we developed a colorimetric assay for the direct detection of PPi as a yellow 18-molybdopyrophosphate anion ([(P2O7)Mo18O54](4-)). [(P2O7)Mo18O54](4-) was further reduced by ascorbic acid to give a more readily distinguishable blue coloration. Here we demonstrate the lab protocols for the colorimetric assay of PPi released in A-domain reactions.

Colorimetric method to detect ε-poly-l-lysine using glucose oxidase

We describe a new colorimetric assay method using glucose oxidase (GOx) to detect ε-poly-l-lysine (εPL). This method uses εPL's remarkable effect of promoting the enzymatic reaction of GOx with ferricyanide ion. This reaction reduces ferricyanide ion to ferrocyanide ion, accompanied by a color change from yellow to colorless. In this colorimetric assay, the detection limit of εPL was estimated to be approximately 0.5 mg/L when purified εPL samples were used. εPL has usually been produced by a fermentation process using Streptomyces albulus species. The components of the culture broth showed interference effects against the assay method. However, due to the high sensitivity of the assay method for εPL, εPL could be detected in the culture broth without any pretreatment. The detectable concentration of εPL in the culture broth, cPL,ac, was estimated to be approximately 20 mg/L. By combining the Berlin blue reaction with this method, the cPL,ac was reduced to 10 mg/L. In light of the proposed method's simplicity and sensitivity, it could be useful for screening εPL synthetic enzymes and microorganisms.

A peptide ligase and the ribosome cooperate to synthesize the peptide pheganomycin

Peptide antibiotics are typically biosynthesized by one of two distinct machineries in a ribosome-dependent or ribosome-independent manner. Pheganomycin (PGM (1)) and related analogs consist of the nonproteinogenic amino acid (S)-2-(3,5-dihydroxy-4-hydroxymethyl)phenyl-2-guanidinoacetic acid (2) and a proteinogenic core peptide, making their origin uncertain. We report the identification of the biosynthetic gene cluster from Streptomyces cirratus responsible for PGM production. Unexpectedly, the cluster contains a gene encoding multiple precursor peptides along with several genes plausibly encoding enzymes for the synthesis of amino acid 2. We identified PGM1, which has an ATP-grasp domain, as potentially capable of linking the precursor peptides with 2, and validate this hypothesis using deletion mutants and in vitro reconstitution. We document PGM1's substrate permissivity, which could be rationalized by a large binding pocket as confirmed via structural and mutagenesis experiments. This is to our knowledge the first example of cooperative peptide synthesis achieved by ribosomes and peptide ligases using a peptide nucleophile.

Analytical methods for the detection and purification of ε-poly-L-lysine for studying biopolymer synthetases, and bioelectroanalysis methods for its functional evaluation

This article describes new analytical methods for studying biopolymer ε-poly-L-lysine (εPL). The produced amount of εPL in culture broth can be determined based on the precipitation of polycationic εPL with a colored heteropolymolybdate anion and the color change of the supernatant. The product can be separated and purified by precipitation with the tetraphenylborate anion and reprecipitation in the form of the hydrochloride salt. These methods have been applied advantageously to the screening of εPL-synthetase. Also, pyrophosphate can be determined colorimetrically based on the formation of 18-molybdopyrophosphate species. The pyrophosphate determination has been successfully applied to the assay of adenylation enzyme, which plays important roles in the biosynthetic mechanism. Under certain conditions, εPL associates with a redox enzyme, glucose oxidase. The effect of the adduction on the stability and reaction rate of the enzyme can be evaluated by measuring the bioelectrocatalytic current, which is related to the enzyme activity. Electrochemical studies showed new applications of εPL as an enzyme stabilizer and a reaction enhancer.

Separation and purification of ε-poly-L-lysine from the culture broth based on precipitation with the tetraphenylborate anion

A biopolymer ε-poly-L-lysine (εPL) exists as a fully protonated form (εPLH(n+)) in solutions at pH < 4. Around pH 3.5, at which the tetraphenylborate (TPB(-)) anion is not decomposed immediately, the εPLH(n+) cation associates with the TPB(-) anion to form a precipitate of 1:n stoichiometry, εPLH(TPB)(n). By the addition of NaTPB to a culture broth containing εPL and NH(4)(+) and K(+) ions, not only the polycationic εPLH(n+) but also the monovalent cations would be precipitated with the TPB(-) anion. However, εPLH(TPB)(n) was purified by washing the mixed precipitate with acetone, in which NH(4)TPB and KTPB are soluble. By mixing the εPLH(TPB)(n) precipitate and a high-concentration HCl solution, the TPB(-) anion was decomposed immediately to hydrophobic molecules. By the addition of a much larger volume of acetone to the reaction mixture, the decomposition products dissolved in the solvent. Simultaneously, εPL was precipitated as the hydrochloride salt. Thus, εPL has been separated and purified from the culture broth. Also, the method has been successfully applied to the separation of oligomeric εPL species. The present chemical separation method is rapid, simple, and easy to carry out, and can be utilized in bioengineering studies of such basic peptides or polyamines.

Mutational analysis of the three tandem domains of ε-poly-L-lysine synthetase catalyzing the L-lysine polymerization reaction

ε-Poly-l-lysine (ε-PL) synthetase (Pls) is a nonribosomal peptide synthetase (NRPS)-like enzyme with three tandem domains to catalyze the l-lysine polymerization reaction. Mutational analysis of the three tandem domains demonstrated that the interconnected action of all three domains is essential for the enzyme activity.

A stand-alone adenylation domain forms amide bonds in streptothricin biosynthesis

The streptothricin (ST) antibiotics, produced by Streptomyces bacteria, contain L-β-lysine ((3S)-3,6-diaminohexanoic acid) oligopeptides as pendant chains. Here we describe three unusual nonribosomal peptide synthetases (NRPSs) involved in ST biosynthesis: ORF 5 (a stand-alone adenylation (A) domain), ORF 18 (containing thiolation (T) and condensation (C) domains) and ORF 19 (a stand-alone A domain). We demonstrate that ST biosynthesis begins with adenylation of L-β-lysine by ORF 5, followed by transfer to the T domain of ORF 18. In contrast, L-β-lysine molecules adenylated by ORF 19 are used to elongate an L-β-lysine peptide chain on ORF 18, a reaction unexpectedly catalyzed by ORF 19 itself. Finally, the C domain of ORF 18 catalyzes the condensation of L-β-lysine oligopeptides covalently bound to ORF 18 with a freely diffusible intermediate to release the ST products. These results highlight an unusual activity for an A domain and unique mechanisms of crosstalk within NRPS machinery.

Assay of enzymes forming AMP+PPi by the pyrophosphate determination based on the formation of 18-molybdopyrophosphate

The formation of 18-molybdopyrophosphate anion has been studied to develop a simple and rapid assay of the enzymatic reaction involving ATP→AMP+PPi(P(2)O(7)(4-)). By the addition of P(2)O(7)(4-) anion to an acidic acetonitrile-water solution containing MoO(4)(2-) anion, the colorless Mo(VI) solution immediately became yellow due to the formation of 18-molybdopyrophosphate anion. The absorbance of the P(2)O(7)(4-)-Mo(VI) mixture at, for example, 450nm was proportional to the analytical concentration of P(2)O(7)(4-) anion. Although the test Mo(VI) solution remained colorless by the addition of AMP, it gradually turned to yellow by ATP. The undesired color development is attributed to the formation of a yellow molybdophosphate species accompanied by the dissociation of PO(4)(3-) from the unstable ATP molecule. However, the color development became much slower when ethylenediaminetetraacetic acid was added into an assay mixture, where ATP may form a kinetically stable species. Thus, P(2)O(7)(4-) anion can be determined spectrophotometrically in the enzymatic reaction mixture containing ATP. By the addition of ascorbic acid, the yellow P(2)O(7)(4-)-Mo(VI) mixture turned to blue due to the reduction of the molybdopyrophosphate anion. Thus, P(2)O(7)(4-) anion can be detected colorimetrically by the blueness. The spectrophotometric and colorimetric methods could be applied advantageously to the assay of acetyl-CoA synthetase.

Development of a recombinant ε-poly-L-lysine synthetase expression system to perform mutational analysis

ε-Poly-L-lysine (ε-PL) synthetase (Pls), which is a membrane protein with adenylation and thiolation domains characteristic of the nonribosomal peptide synthetases, catalyzes polymerization of L-lysine molecules (25-mer to 35-mer). Here, we report on the development of a recombinant Pls expression system that allowed us to perform a site-directed mutational analysis.

Effects of short-term folic acid and/or riboflavin supplementation on serum folate and plasma total homocysteine concentrations in young Japanese male subjects

OBJECTIVE

To investigate the effects of short-term folic acid and/or riboflavin supplementation on serum folate and plasma plasma total homocysteine (tHcy) concentrations in young Japanese male subjects.

DESIGN

In a double blind, randomized controlled trial.

INTERVENTION

Subjects were randomly assigned to one of four groups and received a placebo (control group), 800 microg/day folic acid (FA group), 8.4 mg/day riboflavin (R group), or both (FAR group) for 2 weeks.

SETTING

Tokyo, Japan.

SUBJECTS

In total, 32 healthy male volunteers aged 20-29 years.

RESULTS

At the end of the 2 week supplementation period, the tHcy concentration decreased significantly in the FA group. Serum folate concentrations had increased between 2.7 and 2.0-fold in the FA and FAR groups, respectively, but the mean within-group changes in serum folate and plasma tHcy concentrations did not differ between these two groups. At the end of the study, alanine amino transferase was decreased in the R and FAR groups, while alanine amino transferase was increased in the FA group.

CONCLUSION

Supplementation with folic acid, 800 microg/day, for 2 weeks, increased the serum and red blood cell folate concentrations and decreased the plasma tHcy concentrations in healthy young male subjects. Riboflavin supplementation may have blunted the effect of folic acid, which resulted in a diminished reduction of tHcy in our subjects.

Role of genetic factors (CETP gene Taq I B polymorphism and Apo A-I gene Msp I polymorphism) in serum HDL-C levels in women

BACKGROUND AND AIM

Plasma high density lipoprotein cholesterol (HDL-C) levels are determined by a variety of environmental and genetic factors. The cholesteryl ester transfer protein (CETP) and apolipoprotein A-I (Apo A-I) are considered to be associated with HDL-C metabolism. The aim of this study was to investigate the relationship between the CETP gene Taq I B and Apo A-I gene Msp I polymorphisms and plasma lipid levels taking into account environmental factors, and to determine the combined effects of these polymorphisms on HDL-C levels in Japanese women.

METHODS AND RESULTS

The study involved 270 Japanese women aged 30-69 years. We found a significant association between the CETP genotypes and HDL-C levels (p=0.0020), which were also associated with the Apo A-I gene (M1) polymorphism. Stepwise multiple regression analysis revealed that both the CETP Taq I B and Apo A-I gene (M1) genotypes were independent predictive variables. The strength of the association between the Apo A-I (M1) subgroup and HDL-C levels was reduced in the subjects with a high Body Mass Index (BMI). The combination of genotypes provided more detailed information about HDL-C levels. The "high risk" combination of the M1+ (M1+/+) and B1B1 genotypes was associated with the lowest HDL-C level (1.52+/-0.36 mmol/L), and the "low risk" combination of the M1- (M1+/- or M1-/-) and B2B2 genotypes was associated with the highest HDL-C levels (2.06+/-0.34 mmol/L).

CONCLUSIONS

Our results suggest that the combination of the two polymorphisms influences HDL-C levels in women, and that the association between genetic factors and HDL-C levels is altered by environmental factors. They may also help to detect individuals with low HDL-C levels at high risk for coronary artery syndrome.

Cilnidipine more highly attenuates cold pressor stress-induced platelet activation in hypertension than does amlodipine

The clinical significance of N-type calcium channel blockade has not been fully examined. We here compared the effects of the N-type calcium channel blockers cilnidipine and amlodipine on the sympathetic nervous system and platelet function in hypertension under resting and stressed conditions. Thirty-two patients with hypertension (58+/-9 years) received cilnidipine or amlodipine for 4 weeks in this crossover study. On day 28 of each treatment, plasma levels of epinephrine (EP), norepinephrine (NEP), and beta-thromboglobulin (BTG), and EC50 of ADP-induced platelet aggregation (ADPE50) were determined at rest and after a cold pressor test. On day 29, the group receiving cilnidipine was switched to amlodipine treatment, and vice versa. At rest, the blood pressure, heart rates, EP, NEP, ADPEC50, and BTG, were similar in both treatments. After the cold pressor test, increases in EP (35+/-17 to 44+/-25 pg/ml; p<0.05) and BTG (40+/-13 to 49+/-22 ng/ml; p<0.01) and a decrease in ADPEC50 (32+/-26 to 27+/-24 micromol; p<0.05) were observed in the amlodipine treatment, but not in the cilnidipine treatment. In addition, the increase in NEP was significantly greater (p<0.05) in the amlodipine (276+/-78 to 318+/-87 pg/ml; p<0.01) than in the cilnidipine treatment (273+/-88 to 291+/-100 pg/ml; p<0.05). Cilnidipine more highly attenuates the activation of platelet function in response to cold pressor stress than does amlodipine. Attenuated activation of the sympathetic nervous system via N-type calcium channel blockade may contribute to this phenomenon.

Two-color allele-specific polymerase chain reaction (PCR-SSP) assay of the leptin receptor gene (Leprdb) for genotyping mouse diabetes mutation

An allele specific polymerase chain reaction (PCR-SSP) assay for genotyping the mouse leptin receptor (Leprdb) mutation and its wild type (Lepr+) gene was developed using two different fluorescent dye-labeled primers. First, we determined the Leprdb and Lepr+ allele by PCR-SSP assay with usual dye-unlabeled primers. However this method requires two separate PCR reactions because the amplified products specific for each allele are almost the same size. We further developed a simple and reliable two-color PCR-SSP method that uses a color complementation strategy to distinguish the Leprdb and Lepr+ alleles. Leprdb/Leprdb, Leprdb/Lepr+ and Lepr+/Lepr+ of mice (5 each) were clearly genotyped by the two-color PCR-SSP. We also performed PCR-direct sequencing for the same samples and confirmed the accuracy of this method. This method makes it possible to reduce the number of PCR reactions because both alleles are amplified in the same reaction mixture.

Diesel exhaust-induced airway hyperresponsiveness in c-Ha-ras transgenic mice

Recently the quantity of diesel exhaust (DE) emissions, which contain a variety of chemicals and can induce pulmonary carcinoma in animals, has been increasing in Japan. To assess the toxicity of DE, we evaluated airway hyperresponsiveness after exposure to DE in the rasH2 (CB6F1-TgHras2) mouse, which carries c-Ha-ras genes and shows marked sensitivity to treatment with various genotoxic carcinogens such as methylnitrosourea and dimethylbenzanthracene. We exposed rasH2 mice (n=18) and their nontransgenic littermates (n=19) to room air or 3 mg/m(3) DE for 4 weeks, measured their respiratory resistance (Rrs) during inhalation of acetylcholine (ACh; 0.005, 0.01, 0.02, 0.04, 0.08, 0.16, 0.31, 0.63, 1.28, 2.5, 5, or 10 mg/ml) for 2 min, and calculated the provocative ACh concentration needed to cause a 50% increase (PC(150)) in Rrs. At all doses of ACh, Rrs was significantly higher (P<0.05) in rasH2 mice exposed to DE than in those exposed to room air. In addition, Rrs in the DE-exposed rasH2 animals was significantly higher (P<0.05) at 0.16, 0.31, and 0.63 mg/ml ACh than in DE-exposed nontransgenic littermates. The PC(150) (mean+/-standard error) of DE-exposed rasH2 mice was 3.4+/-1.9 mg/ml, that in rasH2 mice exposed to room air was 10.6+/-2.5 mg/ml, and that in DE-exposed nontransgenic animals was 10.9+/-3.7 mg/ml. In conclusion, DE causes airway hyperresponsiveness in rasH2 mice and may induce the expression of c-Ha-ras genes.

Effects of tomato juice consumption on plasma and lipoprotein carotenoid concentrations and the susceptibility of low density lipoprotein to oxidative modification

Effects of tomato juice supplementation on the carotenoid concentration in lipoprotein fractions and the oxidative susceptibility of LDL were investigated in 31 healthy Japanese female students. These subjects were randomized to one of three treatment groups; Control, Low and High. The Control, Low and High groups consumed 480 g of a control drink, 160 g of tomato juice plus 320 g of the control drink, and 480 g of tomato juice, providing 0, 15 and 45 mg of lycopene, respectively, for one menstrual cycle. The ingestion of tomato juice, rich in lycopene but having little beta-carotene, increased both lycopene and beta-carotene. Sixty-nine percent of lycopene in plasma was distributed in the LDL fraction and 24% in the HDL fraction. In the Low group, the lycopene concentration increased 160% each in the VLDL+IDL, LDL and HDL fractions (p<0.01). In the High group, the lycopene concentration increased 270% each in the VLDL+IDL and LDL fractions, and 330% in the HDL fraction (p<0.01). Beta-carotene also increased 120% and 180% in LDL fractions of the Low and the High groups, respectively. Despite these carotenoid increases in LDL, the lag time before oxidation was not prolonged as compared with that of the Control group. The propagation rate decreased significantly after consumption in the High group. Multiple regression analysis showed a positive correlation between lag time changes and changes in the alpha-tocopherol concentration per triglyceride in LDL, and a negative correlation between propagation rate changes and changes in the lycopene concentration per phospholipid in LDL. These data suggest that alpha-tocopherol is a major determinant in protecting LDL from oxidation, while lycopene from tomato juice supplementaion may contribute to protect phospholipid in LDI, from oxidation. Thus, oral intake of lycopene might be beneficial for ameliorating atherosclerosis.

Overexpression of human H-ras transgene is responsible for tumors induced by chemical carcinogens in mice

Level of human prototype H-ras transgene expression in tumors induced by chemical carcinogens (N-ethyl-N-nitrosourea and N-methyl-N-nitrosourea) was analyzed in human H-ras transgenic mice (CB6F1-TgrasH2 Jic mice). All forestomach tumors examined revealed about 2-fold overexpression of the human H-ras transgene with or without point mutation at codon 12 or codon 61. However, endogenous mouse H- and K-ras genes exhibited neither point mutation nor overexpression. These results suggested that increased levels of ras gene products in the cell played an important role in facilitating chemical carcinogenesis in transgenic mice.

Gene expression profiling of mouse postnatal cerebellar development

Expression patterns of 1,869 genes were determined using adapter-tagged competitive PCR (ATAC-PCR) at 6 time points during mouse postnatal cerebellar development. The expression patterns were classified into 12 clusters that were further assembled into 3 groups by hierarchical cluster analysis. Among the 1,869 genes, 1,053 known genes were assigned to 90 functional categories. Statistically significant correlation between the clusters or groups of gene expression and the functional categories was ascertained. Genes involved in oncogenesis or protein synthesis were highly expressed during the earlier stages of development. Those responsible for brain functions such as neurotransmitter receptor and synapse components were more active during the later stages of development. Many other genes also showed expression patterns in accordance with literature information. The gene expression patterns and the inferred functions were in good agreement with anatomical as well as physiological observations made during the developmental process.

Vitamin E level changes in serum and red blood cells due to acute exhaustive exercise in collegiate women

The purpose of this study was to investigate the change in vitamin E level in both serum and red blood cells (RBC) during exercise and to clarify the effect of vitamin E supplementation. Ten young sedentary female subjects received 200 mg D-alpha-tocopherol acetate daily for 1 wk after the initial exercise bout. After 1 wk of vitamin E supplementation, the same subjects repeated the same exercise. Before vitamin E supplementation, the alpha-tocopherol level in the serum (serum-alpha-tocopherol) did not change after exercise, but a significant decrease in the alpha-tocopherol level in RBC (RBC-alpha-tocopherol) was observed after exercise (p < 0.05). On the other hand, after vitamin E supplementation, the serum-alpha-tocopherol level decreased significantly after exercise (p < 0.05), while the RBC-alpha-tocopherol level was maintained after exercise. Furthermore, a negative correlation between the changes in serum- and RBC-alpha-tocopherol levels was observed only after vitamin E supplementation (r = 0.667, p < 0.05). The present results suggest that as RBC suffers oxidative stress, vitamin E in RBC is consumed to protect RBC from oxidative damage during exercise. These results also suggest that when there is a sufficient amount of vitamin E in the serum, vitamin E is shifted from the serum to RBC, resulting in a steady RBC-alpha-tocopherol level and a decrease in the serum-alpha-tocopherol level under oxidative stress such as exercise.

Rapid induction of uterine tumors with p53 point mutations in heterozygous p53-deficient CBA mice given a single intraperitoneal administration of N-ethyl-N-nitrosourea

To investigate the sensitivity of heterozygous p53-deficient CBA mice to carcinogens, 20 female mice [p53(+/-)] and 20 wild-type littermates [p53(+/+)] were given an intraperitoneal injection of 120 mg/kg body wt of N-ethyl-N-nitrosourea (ENU) and were maintained without any other treatment for a further 26 weeks. Histopathology showed that uterine tumors (endometrial polyps and stromal sarcomas) and lung adenomas were induced in both p53(+/-) and p53(+/+) mice. The incidence of uterine tumors and lung adenomas (94% and 81%, respectively) in p53(+/-) mice was significantly greater than that in p53 (+/+) mice (37% and 42%, respectively). Malignant lymphomas were only induced in p53(+/-) mice, at an incidence of 31%. Concerning uterine tumors and preneoplastic lesions, there were endometrial stromal sarcomas and atypical hyperplasias of the endometrial gland in 90% and 63%, respectively, of p53(+/-) mice, with significantly greater incidences than in p53(+/+) mice. Gene analysis revealed GCG-->GTG point mutations in codon 135 of exon 5 of the p53 allele in all of the uterine endometrial stromal sarcomas examined. Our results suggest that female p53(+/-) CBA mice are very susceptible to uterine carcinogenesis, providing a useful model for ENU-induced uterine tumors.

Correlation between gene functions and developmental expression patterns in the mouse cerebellum

Quantitative changes of 419 gene transcripts during postnatal mouse cerebellar development were accurately determined with a novel polymerase chain reaction (PCR)-based technique. About 70% of the genes showed differences in expression levels, and the magnitude of difference was relatively small. By hierarchic cluster analysis of developmental expression patterns, the genes were categorized into 19 clusters, which were subsequently assembled into four major groups: group 1, with elevation of gene expression throughout the time course; group 2, with relatively unchanged levels; group 3, with transiently high expression at approximately 12 days; and group 4, with highest expression at approximately 4 days. Genes related to brain functions were segregated into several clusters of group 1 and group 3: the same clusters in which cerebellum-specific genes were also segregated. Genes for protein synthesis belonged to group 4. Genes with housekeeping functions belonged to group 2. Western blotting analysis of representative protein products of each group revealed correlation with the mRNA level for those belonging to group 1 and group 4, but not necessarily in the other groups. The close correlation of algorithmically categorized temporal expression patterns of genes with their functions will be useful for estimating the functions of thousands of novel genes.

Gene mapping of SEZ group genes and determination of pentylenetetrazol susceptible quantitative trait loci in the mouse chromosome

Gene mapping of the newly discovered SEZ genes (seizure-related genes) in the mouse was performed by linkage analysis. SEZ6 was on chromosome 11, SEZ12 on chromosome 16, SEZ15 on chromosome 3 and SEZ17 (PTZ17) on chromosome 18. The mouse chromosomal locus related to high susceptibility to pentylenetetrazol (PTZ) was also determined by linkage analysis using the recombinant inbred mouse, BXD (C57BLxDBA). A significant level of PTZ susceptibility was found on chromosome 2. Chromosomal loci of the newly discovered SEZ genes were not coincident with the significant chromosomal loci to PTZ susceptibility. Since epilepsy is assumed to be a disease syndrome which is probably manifested by abnormal expression of multifocal genes, determination of the role of each chromosomal locus in the provocation of seizure activity is important.

Gene expression in mouse cerebellum during its development

Genes expressed during the cerebellar development of the mouse were identified in 3'-directed cDNA libraries prepared from the postnatal day 4, day 12, and week 6 cerebellar tissues. Among about 5500 clones selected randomly from each library, there were approximately 3500 distinct species. A total of 7728 species were identified in the three libraries, 1346 of which were known genes in the GenBank, 3041 EST-matching genes, and 3341 new genes. Relative expression levels at the three postnatal stages were quantitated by adapter-tagged competitive PCR for 130 known genes that appeared six times or more in one of the libraries. Genes for ribosomal proteins and some cytoskeletal and nuclear proteins were abundantly expressed at the early stage, coincidently with extensive proliferation of granule cells as the major cerebellar component. Genes related to brain functions, including those for mitochondrial activities and some ion channel systems, were more active at a later stage when the majority of granule cells were engaged in axon extension and synapse formation or the cerebellum had reached maturity. Compared to these stage-specifically expressed genes, genes for transcriptional regulation, signal transduction, protein modification, and basic cellular functions, in general, were not abundantly expressed at any stage of development.

Structural studies of the vacuolar H(+)-pyrophosphatase: sequence analysis and identification of the residues modified by fluorescent cyclohexylcarbodiimide and maleimide

We determined the amino acid residues of the H(+)-translocating inorganic pyrophosphatase (H(+)-PPase) of pumpkin which are covalently labeled by two fluorescent labeling reagents; N-cyclohexyl-N'-[4-(dimethyl amino)-alpha-naphthyl] carbodiimide (NCD) and N-pyrenylmaleimide (NPM). NCD and NPM are fluorescent analogues of N,N-dicycrohexylcarbodiimide and N-ethylmaleimide, respectively, and inactivate H(+)-PPase activity. Excess Mg2+ protected the H(+)-PPase from the inactivation by these reagents. Furthermore, we identified the cDNA clone encoding the pumpkin H(+)-PPase in order to determine the position of labeled residues. The nucleotide sequence of the cDNA clone contains a 2,304 bp open reading frame encoding a polypeptide with 768 amino acids. Chemical sequence analysis of fluorescent peptide fragments revealed that Glu749 located in the C-terminal putative transmembrane alpha-helix was a NCD-labeled residue, and Cys632 was a NPM-labeled residue located in a putative cytosolic domain. The amino acid sequence of the region that includes Glu749 is highly conserved in H(+)-PPases from other plants and it also shows some sequence similarity with the region of the carbodiimide-reactive Glu (or Asp) of F0F1-ATPase c-subunit. The reactive glutamic acids in these proteins are located at the last C-terminal transmembrane alpha-helix. We also found that the H(+)-PPase shows significant amino acid sequence similarity to Kdp-ATPase A chain of E. coli. This similarity between the two different proteins suggest that they have evolved from a common ancestor and may utilize a common basic mechanism for ion transport.

Right side hepatic resection under right thoracoabdominal incision with special reference to a highly anatomical systematized method

The results of 31 right side hepatic resections approached through thoracoabdominal incision are described, with emphasis on the benefit of the approach and systematized liver resection. Regarding postoperative mortality rate (0%) and morbidity rate (32.3%), the thoracoabdominal approach for right side hepatic resection seemed as safe and effective as the conventional abdominal approach. Even though there were no significant differences in the complications, the fluctuation of alanine aminotransferase and the hospital stay, the average operation time for the right segmentectomy through the thoracoabdominal approach was 1.3 hours less (p = 0.0078) than that of the abdominal approach. Technically, this approach was accomplished in almost the same fashion as in the abdominal approach by the utilization of systematized hepatic resection. Thoracotomy itself was not more harmful than the abdominal approach, even in patients with impaired liver function. This combination could take the advantage of a shorter operation time.