Fluorescence properties of 2-aryl substituted indoles

The fluorescence properties of 2-phenylindole, 2-naphthylindole and 2-anthracenylindole were investigated. 2-Anthracenylindole was newly synthesized by Suzuki-Miyaura's coupling. The fluorescence quantum yield of 2-phenylindole was the highest and the fluorescence emission maximum wavelength of 2-anthracenylindole was the longest. The ab initio quantum chemical calculation of the 2-anthracenylindole showed that the HOMO and LUMO of 2-anthracenylindole were localized in the anthracene moiety.

Mutant mice and rats lacking D-amino acid oxidase

D-amino acid oxidase (DAO) catalyzes oxidative deamination of D-amino acids. Since D-amino acids are considered to be rare in eukaryotes, physiological function of this enzyme has been enigmatic for a long time. Mutant mice lacking DAO were found, and their strain was established. The urine of the mutant mice contained large amounts of D-amino acids. D-Amino acids were also present in their organs and blood. The origin of these D-amino acids was pursued. The results indicate that one of the physiological functions of DAO is the metabolism of D-amino acids of internal and external origin. A large amount of D-serine is shown to exist in the brain of mammals. It binds to the coagonist-binding site of N-methyl-D-aspartate (NMDA) subtype of glutamate receptors and enhances the neurotransmission. DAO metabolizes this D-serine and, therefore, modulates neurotransmission. Mutant mice displayed phenotypes resulting from the enhanced NMDA receptor function. Recent studies have shown that DAO is associated with schizophrenia. Mutant mice were resistant to the drugs which act on NMDA receptors and elicit schizophrenia-like symptoms. Recently, mutant rats lacking DAO have also been found. They were free from D-serine-induced nephrotoxicity, indicating involvement of DAO in this toxicity. The mutant mice and rats lacking DAO would be useful for the elucidation of the physiological functions of DAO and the etiology of neuronal diseases associated with DAO.

Brain-specific Phgdh deletion reveals a pivotal role for L-serine biosynthesis in controlling the level of D-serine, an N-methyl-D-aspartate receptor co-agonist, in adult brain

In mammalian brain, D-serine is synthesized from L-serine by serine racemase, and it functions as an obligatory co-agonist at the glycine modulatory site of N-methyl-D-aspartate (NMDA)-selective glutamate receptors. Although diminution in D-serine level has been implicated in NMDA receptor hypofunction, which is thought to occur in schizophrenia, the source of the precursor L-serine and its role in D-serine metabolism in adult brain have yet to be determined. We investigated whether L-serine synthesized in brain via the phosphorylated pathway is essential for D-serine synthesis by generating mice with a conditional deletion of D-3-phosphoglycerate dehydrogenase (Phgdh; EC 1.1.1.95). This enzyme catalyzes the first step in L-serine synthesis via the phosphorylated pathway. HPLC analysis of serine enantiomers demonstrated that both L- and D-serine levels were markedly decreased in the cerebral cortex and hippocampus of conditional knock-out mice, whereas the serine deficiency did not alter protein expression levels of serine racemase and NMDA receptor subunits in these regions. The present study provides definitive proof that L-serine-synthesized endogenously via the phosphorylated pathway is a key rate-limiting factor for maintaining steady-state levels of D-serine in adult brain. Furthermore, NMDA-evoked transcription of Arc, an immediate early gene, was diminished in the hippocampus of conditional knock-out mice. Thus, this study demonstrates that in mature neuronal circuits L-serine availability determines the rate of D-serine synthesis in the forebrain and controls NMDA receptor function at least in the hippocampus.

6,7-Difluoro-1,4-dihydro-1-methyl-4-oxo-3-quinolinecarboxylic acid, a newly designed fluorescence enhancement-type derivatizing reagent for amino compounds

A novel fluorescence enhancement-type derivatizing reagent for amino compounds, 6,7-difluoro-1,4-dihydro-1-methyl-4-oxo-3-quinolinecarboxylic acid (FMQC), was developed. FMQC reacts with aliphatic primary amino compounds to afford strong fluorescent derivatives having high photo-and thermo-stabilities. The FMQC derivatives of amino compounds showed 12-159 times higher fluorescence quantum efficiencies than those of FMQC in aqueous and polar organic media. Additionally, the absorption and fluorescence emission wavelength of the derivatives are red-shifted from those of FMQC. These differences in the fluorescence properties between FMQC and the fluorescent derivative enabled the simple and highly sensitive determination of amino compounds without removing any excess unreacted FMQC by using a simple spectrofluorometer as well as HPLC.

Analysis of small amounts of D-amino acids and the study of their physiological functions in mammals

D-amino acids, the enantiomers of L-amino acids, are candidates to be novel physiologically active substances and the biomarkers in mammals. However, the amounts of D-amino acids in the tissues and physiological fluids are extremely small in most cases, and sensitive and selective analytical methods are needed for their determination. In the present manuscript, we review the analytical technologies including our recent advances for the determinations of small amounts of D-amino acids in mammals and the applications to clarify their physiological meanings.

Simultaneous determination of hydrophilic amino acid enantiomers in mammalian tissues and physiological fluids applying a fully automated micro-two-dimensional high-performance liquid chromatographic concept

A validated two-dimensional HPLC system combining a microbore-monolithic ODS column and a narrowbore-enantioselective column has been established for a sensitive and simultaneous analysis of hydrophilic amino acid enantiomers (His, Asn, Ser, Gln, Arg, Asp, allo-Thr, Glu and Thr) and the non-chiral amino acid, Gly, in biological samples. To accomplish this goal, the amino acids were first tagged with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) to the respective fluorescent NBD derivatives which were separated in the first dimension by a micro-reversed-phase column. The automatically collected fractions of the target peaks were then transferred to the second dimension consisting of a Pirkle type enantioselective column generating separation factors higher than 1.13 for all the enantiomeric target analytes. The system was validated using standard amino acids and a rat plasma sample, and analytically satisfactory calibration and precision results were obtained. The present 2D-HPLC system enables the fully automated determination of hydrophilic amino acid enantiomers in mammalian samples. The d-isomers of all the investigated 9 amino acids were found in rat urine but at various enantiomeric ratios.

Chemiluminescence enhancement of 1,2-di[3,4,5-tri(3,4,5-trihydroxybenzoyloxy)benzoyloxy] benzene in the presence of quaternary ammonium ions

The chemiluminescence intensity of 1,2-di[3,4,5-tri(3,4,5-trihydroxybenzoyloxy)benzoyloxy] benzene increased in the presence of quaternary ammonium ions, such as acetylcholine chloride, choline chloride or benzyltrimethylammonium chloride. The complex of 1,2-di[3,4,5-tri(3,4,5-trihydroxybenzoyloxy)benzoyloxy] benzene with acetylcholine chloride, choline chloride or benzyltrimethylammonium chloride was investigated by (1)H-NMR spectroscopy. The structure of the complex formed from 1,2-di[3,4,5-tri(3,4,5-trihydroxybenzoyloxy)benzoyloxy] benzene with choline chloride was described by an ab initio quantum chemical calculation.

Determination of D-serine and D-alanine in the tissues and physiological fluids of mice with various D-amino-acid oxidase activities using two-dimensional high-performance liquid chromatography with fluorescence detection

Two-dimensional-HPLC procedures have been established for the sensitive and selective determination of D-serine (D-Ser) and D-alanine (D-Ala), and their amounts in the tissues and physiological fluids of mice with various D-amino-acid oxidase (DAO) activities have been demonstrated. These two D-amino acids are modulators of the N-methyl-D-aspartate receptor mediated neurotransmission, and the alterations in their amounts following the changes in the DAO activity are matters of interest. After pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), the D-amino acids were determined by the 2D-HPLC system with fluorescence detectors. As the first dimension, a microbore-monolithic-ODS column (750 mm x 0.53 mm I.D.) was adopted and a self-packed narrowbore-Pirkle type enantioselective column (Sumichiral OA-2500S, 250 mm x 1.5 mm I.D.) was selected for the second dimension. The lower limits of quantitation of D-Ser and D-Ala were 500 amol, and the within-day and day-to-day precisions were less than 6.8%. Using these methods, the amounts of D-Ser and D-Ala in 6 brain tissues, 4 peripheral tissues, serum and urine of mice having various DAO activities were determined; the amounts of these D-amino acids were drastically increased with a lowering of the DAO activity except for the cases of D-Ser in the frontal brain regions. The present micro-2D-HPLC procedures are powerful tools for the determination of small amounts of D-Ser and D-Ala in mammalian samples, and the obtained results would be useful for developing novel drugs that modulate the DAO activity, such as DAO inhibitors, against neuronal diseases.

Chemiluminescence change of polyphenol dendrimers with different core molecules

Second generation polyphenol dendrimers (PDs) with different core molecules were synthesized, and their chemiluminescence (CL) was measured by reacting the PDs with H2O2 under alkaline conditions. All of the PDs showed a strong CL, more than 120-fold greater than that of gallic acid. Various CL intensities of the PDs were obtained using different core molecules in the PDs. The distance between each dendron in the PD structure is crucial in the PD CL intensity.

Bisindolylmaleimides with large Stokes shift and long-lasting chemiluminescence properties

Various bisindolylmaleimides have fluorescence emission maxima wavelengths longer than 500 nm, large Stokes shifts longer than 200 nm, different fluorescence emission wavelengths at an excitation wavelength of 365 nm, and a long-lasting chemiluminescence. The expansion of the pi-conjugation, the pi-bond electronic structure, and oxidation of the C=C bond at the 2,3-position of the maleimide moiety are crucial for producing these fluorescence and chemiluminescence properties.

A genetic variant of the serine racemase gene is associated with schizophrenia

BACKGROUND

Serine racemase (SRR) is a brain-enriched enzyme that converts L-serine to D-serine, which acts as an endogenous ligand of N-methyl D-aspartate (NMDA) receptors. Dysfunction of SRR may reduce the function of NMDA receptors and susceptibility to schizophrenia.

METHODS

We genotyped three single-nucleotide polymorphisms (SNPs) of the 5' region of the SRR gene in 525 patients with schizophrenia and 524 healthy controls. Effects of SNPs on the promoter activity and on serum levels of total and D-serine were examined.

RESULTS

We found a significant excess of the IVS1a+465C allele of the SRR gene in schizophrenia, especially in the paranoid subtype (p = .0028). A reporter assay showed that the IVS1a+465C allele had 60% lower promoter activity than did the IVS1a+465G allele.

CONCLUSIONS

The IVS1a+465C allele of the SRR gene, which reduces expression of the gene, is a risk factor for schizophrenia, especially the paranoid subtype.

Immunohistochemical localization of d-alanine to β-cells in rat pancreas

A mouse monoclonal antibody against D-alanine (D-Ala) has been raised and the immunohistochemical localization of this D-amino acids in the rat pancreas is visualized. The obtained anti-D-Ala monoclonal antibody has no significant cross-reactivity to all proteinogenic L-amino acids and their D-enantiomers. Using this antibody, immunohistochemical staining was performed on the pancreas, and specific staining for d-Ala has been observed only in the Langerhans islets. To identify the types of D-Ala-immunopositive cells, double staining was carried out with antibodies against D-Ala and pancreatic hormones. Similar immunostaining patterns have been observed for D-Ala and insulin, while D-Ala is hardly co-localized with other hormones (glucagon, somatostatin, and pancreatic polypeptide). These results indicate for the first time that D-Ala is localized to insulin producing beta-cells in mammalian pancreas, suggesting that this D-amino acid would be involved in the regulation of the blood glucose level.

Comprehensive analysis of branched aliphatic d-amino acids in mammals using an integrated multi-loop two-dimensional column-switching high-performance liquid chromatographic system combining reversed-phase and enantioselective columns

A validated two-dimensional HPLC method for the comprehensive analysis of small quantities of branched aliphatic D-amino acids in the presence of large amounts of their L-congeners in mammalian tissues and physiological fluids is described. The quantitative analysis of these aliphatic amino acids (Val, allo-Ile, Ile, and Leu) is important for the diagnosis of various inherent metabolic disorders of amino acids, and the D-enantiomers are expected to be of particular interest from a pharmacological point of view. Target analytes were determined as their fluorescent derivatives, pre-column labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), using an automated two-dimensional column-switching high-performance liquid chromatographic system combining a narrow bore reversed-phase column and an enantioselective column connected with an integrated multi-loop peak fraction storage device. The described two-dimensional analysis concept proved to be successful for the given task in biological samples taken from mammals. Total analysis time for the reversed-phase separation of the four target NBD-amino acids is 60 min, and the integrated enantiomer separation of each of the four analytes is completed in approximately 5 min. In the rat, significant amounts of D-Leu were found in all tissues and physiological fluids tested (trace-1.3 nmol/g tissue), and in the urine, the presence of high amounts of D-allo-Ile (D-isomer of a non-proteinogenic amino acid, 22.2 nmol/ml) was demonstrated. D-allo-Ile was also found in the urine of dog and mouse, which indicates the ubiquitous presence of this unusual D-amino acid and the potential need to clarify its unique metabolism in mammals.

Metabolism of the recently encountered designer drug, methylone, in humans and rats

The urinary metabolites of methylone in humans and rats were investigated by analysing urine specimens from its abuser and after administrating to rats with gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-electrospray ionization mass spectrometry (LC-ESI MS), using authentic standards. The time-course excretion profiles of methylone and its three metabolites in rats were further investigated after a single intraperitoneal dosing of 5 mg kg-1 methylone hydrochloride. Two major metabolic pathways were revealed for both humans and rats as follows: (1) side-chain degradation by N-demethylation to the corresponding primary amine methylenedioxycathinone (MDC), partly conjugated; and (2) demethylenation followed by O-methylation of either a 3- or 4-OH group on the benzene ring to produce 4-hydroxy-3-methoxymethcathinone (HMMC) or 3-hydroxy-4-methoxymethcathinone (3-OH-4-MeO-MC), respectively, mostly conjugated. Of these metabolites, HMMC was the most abundant in humans and rats. The cumulative amount of urinary HMMC excreted within the first 48 h in rats was approximately 26% of the dose, and the amount of the parent methylone was not more than 3%. These results demonstrate that the analysis of HMMC will be indispensable for proof of the use of methylone in forensic urinalysis.

High-throughput determination of free d-aspartic acid in mammals by enzyme immunoassay using specific monoclonal antibody

A method for rapid determination of free D-aspartic acid (D-Asp) in mammals has been established using a highly specific mouse monoclonal antibody against D-Asp for the first time. An anti-D-Asp monoclonal antibody was obtained by the immunization of bovine-serum-albumin-conjugated D-Asp to BALB/c mice. The obtained antibody has a high specificity toward D-Asp but shows a slight cross-reactivity to all other D- and L- amino acids including L-Asp. The calibration range of the competitive enzyme linked immunosorbent assay (ELISA) is 0.016-16 micromol/mL D-Asp in rat serum samples. The precisions of this method were evaluated by inter-plate and intraplate assays, and the relative standard deviation values were 4.8% and 4.5%, respectively. The values of D-Asp determined by the present ELISA have a good correlation to those determined by high-performance liquid chromatography with the correlation coefficient of 0.963. Using this ELISA, the time course of D-Asp in the rat serum after intravenous administration was successfully demonstrated. The present method provides a simple and high-throughput determination of D-Asp in mammals, and is a useful tool for clarifying the physiological roles and diagnostic values of this D-amino acid.

Presence and origin of large amounts of d-proline in the urine of mutant mice lacking d-amino acid oxidase activity

Using a column-switching HPLC system combining a micro-ODS column and a chiral column, the amounts of D-proline (D-Pro) have been determined in 18 tissues, plasma and urine of mice. To avoid the enzymatic degradation of D-amino acids in vivo, a mutant mouse strain lacking D-amino acid oxidase activity (ddY/DAO(-) mouse) was used. In the brain, relatively large amounts of D-Pro were observed in the anterior pituitary, posterior pituitary and pineal glands. In the peripheral tissues, the amounts of D-Pro were high in the pancreas and kidney. Above all, it is surprising that the ddY/DAO(-) mice excreted large amounts of D-Pro in their urine (433 nmol/mL, 20 times that of L-Pro). The origin of D-Pro has also been investigated. By comparing germ-free mice and gnotobiotic mice, intestinal bacteria were shown to have no effect on the urinary D-Pro amount. Concerning the dietary origin, a notable amount of D-Pro was still excreted in the urine after starvation for 4 days, suggesting that some of the D-Pro is produced in the mice. Age-dependent changes in the urinary D-Pro amount have also been investigated from the postnatal 1st month up to 12 months, and ddY/DAO(-) mice were found to excrete large amounts of D-Pro in the urine constantly throughout their lives.

Alterations in D-amino acid levels in the brains of mice and rats after the administration of D-amino acids

To mutant ddY/DAO(-) mice lacking D-amino-acid oxidase activity and normal ddY/DAO(+) mice, five D-amino acids (D-Asp, D-Ser, D-Ala, D-Leu and D-Pro) were orally administered for two weeks, and the D-amino acid levels were examined in seven brain regions. The levels of D-Asp markedly increased in the pituitary and pineal glands in both strains. In the ddY/DAO(+) mice, the levels of the other D-amino acids did not significantly change in most of the brain regions. While in the ddY/DAO(-) mice the levels of D-Ser significantly increased in most of the brain regions except for the cerebrum and hippocampus. The levels of D-Ala and D-Leu increased in all regions but the levels of D-Pro did not significantly change. The same five D-amino acids were intravenously injected into Wistar rats and the D-amino acid levels in their brains were examined for 60 min after the administration. The levels of D-Asp markedly increased in the pineal gland 3 min after the administration, while the levels of D-Ser, D-Ala, and D-Pro increased both in the pineal and pituitary glands, the levels of D-Leu increased in all brain regions. These results are useful for the elucidation of the origins and regulation of D-amino acids in the mammalian body.

Sensitive determination of D-amino acids in mammals and the effect of D-amino-acid oxidase activity on their amounts

The determination of small amounts of D-amino acids in mammalian tissues is still a challenging theme in the separation sciences. In this review, various gas-chromatographic and high-performance liquid chromatographic methods are discussed including highly selective and sensitive column-switching procedures. Based on these methods, the distributions of D-aspartic acid, D-serine, D-alanine, D-leucine and D-proline have been clarified in the mouse brain. As the regulation mechanisms of D-amino acid amounts in mammals, we focused on the D-amino-acid oxidase, which catalyzes the degradation of D-amino acids. Using the mutant mouse strain lacking D-amino-acid oxidase activity, the effects of the enzymatic activity on the amounts and distributions of various D-amino acids have been investigated.

Sensitive high-performance liquid chromatographic assay for D-amino-acid oxidase activity in mammalian tissues using a fluorescent non-natural substrate, 5-fluoro-D-tryptophan

A sensitive assay for D-amino-acid oxidase (DAO) activity in mammalian tissues has been established. D-Tryptophan (D-Trp) analogs were tested as substrates for DAO, and 5-fluoro-D-tryptophan (D-FTP) was found to be the best substrate. By the enzymatic reaction, D-FTP was converted to 5-fluoroindole-3-acetic acid (FIAA), a highly fluorescent product, and the product was determined by an RP-HPLC system with a fluorescence detector. The detection limit for purified DAO (from hog kidney) was 0.25 microU, and the within-day and day-to-day precisions of the assays were 4.6% (RSD, n=5), and 13.8% (RSD, 5 days), respectively. By the present method, the detailed distribution of DAO activity in the mouse brain was determined using individual animals for the first time, and significant activities were observed in the cerebellum, medulla oblongata and midbrain. Because sensitive DAO assay is frequently required in small tissues or in limited-tissue regions, the present method is useful for various research studies concerning DAO and the related D-amino acids.

Synthesis of 61-bis(1-adamantylcarbamoyl)-1,2-methano[60]fullerene and its antagonistic effect on haloperidol-induced catalepsy in mice

The 61-bis(1-adamantylcarbamoyl)-1,2-methano[60]fullerene was synthesized from N,N'-di(1-adamantyl)malondiamide and C(60) in the presence of 1,8-diazabicyclo[5,4,0]-7-undecene. The intraperitoneal administration of this fullerene derivative (10mg/kg) caused an antagonistic effect on haloperidol-induced catalepsy in mice.

Assay method for Escherichia coli photolyase activity using single-strand cis-syn cyclobutane pyrimidine dimer DNA as substrate

A high-performance liquid chromatography method for the assay of Escherichia coli photolyase activity was developed. When cis-syn cyclobutane pyrimidine dimer was used as substrate, the Michaelis constant (K(m)) value for the photolyase activity was 100 nM. The linear range of the calibration curve of the photolyase activity was 0.026-6.64 microU/assay tube. The correlation coefficient for this linearity was 0.998. The limit of detection (S/N = 3) was 26 nU/assay tube. The photolyase activity was increased 1.6-fold in the presence of 5,10-methenyltetrahydrofolic acid in the enzyme reaction mixture.

Novel stable fluorophore, 6-methoxy-4-quinolone, with strong fluorescence in wide pH range of aqueous media, and its application as a fluorescent labeling reagent

6-Methoxy-4-quinolone (6-MOQ, 1), an oxidation product derived from 5-methoxyindole-3-acetic acid, is a novel fluorophore, which has several useful characteristics for biomedical analysis. Compound 1 has strong fluorescence with a large Stokes' shift in aqueous media, and the maximum fluorescence excitation and emission wavelengths are 243 nm and 374 nm, respectively. The molar absorptivity at the maximum excitation wavelength and fluorescence quantum yield in aqueous 10% (v/v) methanol are 32 600 L mol(-1) cm(-1) and 0.38, respectively. The fluorescence intensity of 1 is scarcely affected by changing the medium pH, showing strong fluorescence from pH 2.0 to 11.0. In addition, 1 is highly stable against light and heat, and no degradation was observed at 60 degrees C for 3 days with exposure to daylight. As a fluorescent labeling reagent, [(6-methoxy-4-oxo-1,4-dihydroquinolin-3-yl)methyl]amine (6-MOQ-NH2, 2) was synthesized, and determination of carboxylic acids was demonstrated; 50 pmol of standard propionic acid and isobutyric acid were derivatized, and the obtained S/N ratios for 10 fmol (injection amount) of these two acids were 206 and 164, respectively.

A sensitive internal standard method for the determination of melatonin in mammals using precolumn oxidation reversed-phase high-performance liquid chromatography

A sensitive and accurate internal standard method to determine melatonin in mammalian tissues and physiological fluids has been described. This method includes the oxidation of melatonin to a highly fluorescent compound, N-[(6-methoxy-4-oxo-1,4-dihydroquinolin-3-yl)methyl]acetamide (6-MOQMA), and the determination of 6-MOQMA by a reversed-phase HPLC system. For the accurate and reliable determination, several melatonin analogs were designed and utilized as the internal standards, and ethyl and isopropyl analogs (having the corresponding alkyl group via the amide bond of melatonin instead of the methyl group) were found to be promising. Using these internal standards, highly accurate and sensitive determination could be accomplished using rat pineal gland samples, and the clear circadian rhythms are demonstrated. This method was also successfully applied to the determination of melatonin in a small amount (20 microL) of human saliva.

Determination of d- and l-enantiomers of threonine and allo-threonine in mammals using two-step high-performance liquid chromatography

A sensitive and selective method for the determination of four threonine (Thr) isomers (L-Thr, D-Thr, L-allo-Thr and D-allo-Thr) in mammalian tissues has been established using two-step high-performance liquid chromatography. This method includes the precolumn fluorescence derivatization of amino acids with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), and the separation using a combination of a reversed-phase column and a chiral column. The calibration ranges of D-Thr, D-allo-Thr and L-allo-Thr spiked in the rat cerebellum sample are 2.5 fmol-5 pmol per injection, and that of L-Thr is 50 fmol-50 pmol. Within-day and day-to-day precisions of the determination of the four Thr isomers are approximately 5% in the rat cerebellum. By using this method, the tissue distributions of D-Thr, D-allo-Thr and L-allo-Thr in mammals have been demonstrated for the first time in rats, and found that significant amounts of D-Thr and D-allo-Thr are present in the frontal brain areas and urine. Among the 12 tissues tested, the highest amounts of D-Thr (0.85 +/- 0.05 nmol/g wet tissue) and D-allo-Thr (5.01 +/- 0.32 nmol/g wet tissue) were found in the corpus striatum. L-allo-Thr was not present in any of the tested tissues and physiological fluids.

Chronopharmacology of melatonin in mice to maximize the antitumor effect and minimize the rhythm disturbance effect

The influence of dosing time on the antitumor effect and the rhythm disturbance effect of melatonin (MLT) was investigated in ICR male mice under a light/dark (12:12) cycle. In tumor-bearing mice, the antitumor effect of MLT (1 mg/kg intraperitoneal) was most effective in the dark phase; and the rhythm disturbance effect of MLT on the locomotor activity was more serious in the light phase than in the dark phase. The antitumor effect and the rhythm disturbance effect of MLT increased when the specific binding of MLT receptor in target tissues, tumor or suprachiasmatic nucleus, increased and they decreased when the level decreased. Furthermore, because luzindole, an MT1 and MT2 blocker, caused the antitumor effect or rhythm disturbance effect of MLT to decrease, it is suggested that the time-dependent change of the pharmacological effects of MLT were influenced by that of MLT receptor(s) function. On the other hand, there was no significant dosing time-dependent change of MLT concentration in tumor or brain after injection. Thus, the pharmacokinetic factor does not seem to contribute to the dosing time-dependent effect of MLT. These results suggest that by choosing the most suitable dosing time for MLT, the efficacy of the drug can be increased, and the toxicity of the drug can be decreased in certain experimental and clinical situations.

2-amino-3-phenylpyrazine, a sensitive fluorescence prelabeling reagent for the chromatographic or electrophoretic determination of saccharides

2-Amino-3-phenylpyrazine is found to be a sensitive fluorescence labeling reagent for saccharides with a reducing end. The labeled monosaccharides show strong fluorescence under various pH conditions, and could be analyzed by both HPLC and HPCE techniques. Laser induced fluorescence detection is also applicable. Following derivatization with 2-amino-3-phenylpyrazine, six monosaccharides are separated by an HPCE system within 23 min in the calibration range of 5 or 10 fmol to 5 pmol (injection amount). The within-day and day-to-day precisions of the monosaccharide determinations are 3.83-4.86% (RSD) and 3.37-4.56% (RSD), respectively. This method was successfully applied to the determination of component monosaccharides in a glycoprotein, bovine serum fetuin.

Enhancement effect of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and cationic surfactant on the chemiluminescence of poly(3, 4, 5-trihydroxybenzoate ester)dendrimers

In the presence of l-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), the chemiluminescence (CL) intensities of poly(3, 4, 5-trihydroxybenzoateester)dendrimers, 1 and 2, having 1,2-pyrocatechol and 1,3,5-trihydroxybenzene as core molecules and also six and nine gallic acid units in the periphery, were respectively 7.4- and 2.4-fold stronger than those of 1 and 2 in the absence of EDC. Similarly, the CL intensities of 1 and 2 in the presence of cetyltrimethylammonium bromide (CTAB) were respectively 4- and 1.7-fold stronger than those of 1 and 2 in the absence of CTAB.

Determination of endogenous melatonin in the individual pineal glands of inbred mice using precolumn oxidation reversed-phase micro-high-performance liquid chromatography

The amount of endogenous melatonin in the individual pineal glands of inbred mice has been determined using reversed-phase micro-high-performance liquid chromatography after precolumn oxidation of melatonin to a compound having strong fluorescence. The fluorescent compound was identified as N-[(6-methoxy-4-oxo-1,4-dihydroquinolin-3-yl)methyl]acetamide. The excitation and emission wavelengths of this compound are 245 and 380 nm, respectively, and the fluorescence intensity is 6.8 times greater than that of melatonin. Molar absorptivity and fluorescence quantum yield of this compound are 46,300[L mol(-1)cm(-1)] and 0.31 (245 nm), respectively. The lower quantification limit of melatonin in biological samples using this precolumn oxidation method is 200 amol, and the calibration curve of spiked melatonin is linear from 200 amol to 50 fmol (r>0.999). The sensitivity of the present method is almost 10 times higher than that of the previous method. The values of endogenous melatonin obtained for ICR, C57BL, BALB/c, and AKR mice are 4.7, 6.1, 7.4, and 18.8 fmol/pineal gland, respectively. The amounts of endogenous pineal melatonin of these strains had not been clearly reported due to the poor enzymatic activities for melatonin biosynthesis; this is the first report that clearly demonstrates the existence of endogenous melatonin in these inbred mice.

Determination of D-alanine in the rat central nervous system and periphery using column-switching high-performance liquid chromatography

A column-switching chiral HPLC system for the determination of minute amounts of D-Ala in mammalian tissues has been established. D-Ala and its L-enantiomer are purified as a DL mixture on a micro-ODS column after precolumn fluorescence derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole and are introduced to a chiral column to determine each enantiomer. The calibration curve of D-Ala spiked into a rat cerebellum sample is linear from 5 to 5000 fmol with a correlation coefficient of 1.0000. The lower limit of quantitation of D-Ala is 5 fmol (S/N=5). Within-day and day-to-day precisions of spiked D-Ala (15 fmol) are 3.9 and 4.8% (R.S.D), respectively. With this system, the anatomical distribution of free D-Ala in the rat central nervous system and periphery has been investigated. Among the 22 examined tissues of the rat, the highest amount of D-Ala has been observed in the anterior pituitary gland (86.4+/-9.9 nmol/g wet tissue), and the second highest amount has been observed in the pancreas (29.2+/-5.0 nmol/g wet tissue). Postnatal and day-night changes in D-Ala amounts in the anterior pituitary gland have also been studied. The amount of D-Ala is highest at 6 weeks of age and significantly decreases with age, and the amount of D-Ala is significantly higher during the daytime than during the nighttime.

Lasting chemiluminescence of 3-indoleglyoxylyl chloride and its enhancement

The chemiluminescence (CL) intensities of various indole derivatives substituted with a glyoxylyl group at the 3-position and a hydroxyl group at the 5-position of the indole ring were compared upon the addition of H2O2 in alkaline media. The CL intensities of 3-indoleglyoxylyl chloride, 3-indoleglyoxylic acid, 5-hydroxyindole and 5-benzyloxyindole in CH3CN were 5.9-, 48-, 5.9- and 3.3-fold stronger than that of 3-methylindole. A lasting CL of 3-indoleglyoxylyl chloride was found. Under appropriate conditions, the CL emission reached a maximum within 10 min after the addition of H2O2 in the presence of NaOH, and the intensity was retained for 25 min. One of the final products via the CL reaction of 3-indoleglyoxylyl chloride was indole-3-carboxylic acid. 3-Indoleglyoxylyl chloride emitted light by decompositions via both dioxetane and dioxetanedione. An enhancement effect of beta-cyclodextrin and bovine serum albumin on the CL of 3-indoleglyoxylyl chloride was also found.

D-Amino acids in mammals and their diagnostic value

Substantial amounts of D-amino acids are present in mammalian tissues; their function, origin and relationship between pathophysiological processes have been of great interest over the last two decades. In the present article, analytical methods including chromatographic, electrophoretic and enzymatic methods to determine D-amino acids in mammalian tissues are reviewed, and the distribution of these D-amino acids in mammals is discussed. An overview of the function, origin and relationship between the amino acids and pathophysiological processes is also given.

Reversible fluorescence labeling of amino groups of protein using dansylaminomethylmaleic anhydride

The reversible fluorescence labeling of insulin, catalase and lysozyme has been demonstrated. As a derivatizing reagent, dansylaminomethylmaleic acid (DAM) has been used after investigating the precolumn and precapillary derivatization conditions. This reagent (DAM) reacts with the amino groups of proteins via its anhydride in the presence of a suitable dehydrating reagent, which then could be liberated under mild acidic conditions and the native proteins are regenerated. After the derivatization of insulin, catalase and lysozyme with DAM, no peaks of these native proteins were observed while several peaks of the derivatized proteins due to the multiple labeling were observed. However, after the regeneration, increasing amounts of the native proteins were observed as the regeneration period increased. For the lysozyme, the bacteriolytic activity of the enzyme decreased after the derivatization, and only 0.9% of the activity remained. The activity increases by the regeneration, and 95.6% of the bacteriolytic activity of the native enzyme was observed after a 48-h regeneration at pH 2.5 and 40 degrees C.

Determination of free D-proline and D-leucine in the brains of mutant mice lacking D-amino acid oxidase activity

A new procedure to accurately measure a trace amount of d-proline in biological samples has been developed. This D-amino acid was derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole and was determined by a column-switching HPLC system, a combination of a micro-ODS column and a chiral column. The detection limit for D-proline spiked in a mouse cerebrum sample is 1 fmol (injection amount, S/N = 3). Within-day precision and day-to-day precision obtained for spiked d-proline (10 fmol) are 2.14 and 5.35% (RSD), respectively. Using the new method, the amount of free D-proline in eight brain regions and sera of mutant ddY/DAO- mice, lacking D-amino acid oxidase activity, and control ddY/DAO+ mice was determined. The amount of free D-leucine was also investigated. The amount and distribution of D-proline in the brains of ddY/DAO+ mice and ddY/DAO- mice are almost the same, and relatively high amounts of D-proline have been observed in the pituitary gland and in the pineal gland. On the other hand, the amount of D-leucine is different between the two strains. In the brains of ddY/DAO+ mice, a relatively high amount of D-leucine has been observed in the pineal gland compared with other regions. In the brains of ddY/DAO- mice, D-leucine amounts are approximately 10 times higher than those obtained in ddY/DAO+ mice and regional difference has not been observed, while the amounts of L-proline and L-leucine are not significantly different between the two strains. In the serum, the amounts of both free D-proline and d-leucine are significantly higher in the ddY/DAO- mice than those obtained in ddY/DAO+ mice.

Determination of free D-aspartic acid, D-serine and D-alanine in the brain of mutant mice lacking D-amino acid oxidase activity

A simple and precise method for the simultaneous determination of free D-aspartic acid, D-serine and D-alanine in mouse brain tissues was established, using a reversed-phase HPLC system with widely used pre-column derivatizing reagents, o-phthaldialdehyde and N-t-butyloxycarbonyl-L-cysteine. With the present method, the contents of these three D-amino acids in hippocampus, hypothalamus, pituitary gland, pineal gland and medulla oblongata as well as cerebrum and cerebellum of mutant mice lacking D-amino-acid oxidase activity were determined and compared with those obtained for control mice. In both mice, extremely high contents of D-serine were observed in forebrain (100-400 nmol/g wet tissue), and the contents were small in pituitary and pineal glands. While, D-serine contents in cerebellum and medulla oblongata of mutant mice were about ten times higher than those in control mice. In contrast, D-alanine contents in mutant mice were higher than those in control mice in all brain regions and serum.