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Biomedical subjects

M Naoi

Publications and source records attributed to M Naoi.

At least 19 recordsLinked to original sources
PubMed1992

Endogenous synthesis of N-methylsalsolinol, an analogue of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, in rat brain during in vivo microdialysis with salsolinol, as demonstrated by gas chromatography-mass spectrometry.

N-Methylsalsolinol, an analogue of 1,2,3,6-tetrahydropyridine, is present in the brains of patients with Parkinson's disease. To determine the metabolic pathway for the synthesis of N-Methylsalsolinol in the brain, salsolinol was perfused through the striatum or the substantia nigra of the rat brain by in vivo microdialysis. N-Methylsalsolinol was detected in the brain dialysate samples during microdialysis with salsolinol using gas chromatography-mass spectrometry with selected-ion monitoring. These results demonstrate that endogenous N-methylation of salsolinol into N-methylsalsolinol occurs in the brain in vivo.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Multiple colorectal carcinomas and colorectal carcinoma associated with extracolonic malignancies.

In this study, we analyzed 149 surgical cases of colorectal cancer between January 1983 and August 1989. Thirteen cases (8.7 percent) of colorectal primary cancer associated with extracolonic primary malignancy of 14 lesions and 10 cases (6.7 percent) of multiple primary colorectal cancers were included. Among the 14 lesions of extracolonic primary malignancy, there were 6 gastric carcinomas, 2 endometrial carcinomas, 2 urinary bladder carcinomas, and one each in the esophagus, liver, bile duct and jejunum. The second tumor was not detected preoperatively in 3 of 4 cases of synchronous multiple primary colorectal carcinoma. A curative resection was done in 10 (77 percent) out of 13 cases of colorectal cancer associated with extracolonic malignancy, while 7 (88 percent) out of 8 cases of multiple colorectal cancers had a curative resection. Nine patients (69 percent) with colorectal cancer associated with extracolonic malignancy were disease-free for 2 months to 14 years. Seven patients (88 percent) with multiple colorectal cancers were disease-free for one to 22 years. We recommend, therefore, that in any patient with colorectal cancer, the entire large bowel should be thoroughly searched for any other primary tumors, by taking the existence of extracolonic tumors into account. A curative resection should be performed, and the follow-up period should be life-long.

Adenocarcinoma↗
PubMed1992

Efficacy of combination treatment--(TAE with adriamycin and ethanol)--for hepatocellular carcinoma.

Among 44 patients with hepatocellular carcinoma (HCC), combination treatment with both transhepatic arterial embolization (TAE) and ethanol injection therapy (EIT) was performed in 10 patients. Only two had tumors measuring less than 3 cm in diameter. In all, eight patients had solitary tumors and two had multiple tumors. The tumor was classified as stage I in one patient, stage II in six subjects, stage III in two patients, and stage IV in one subject prior to TAE, but one stage II case was changed to stage III after laparotomy. The clinical stage was I in two patients, II in six subjects and III in two patients. Five patients with tumors of stages I and II achieved either a complete response (CR) or partial response (PR). However, three patients with tumors of stages III and IV showed progressive disease (PD). Thus, the response rate (CR+PR) was 50%. For tumor stages I and II, the 1-, 2-, and 3-year survival values were 100%, 100%, and 83%, respectively. For tumor stages III and IV, the 1- and 2-year survival values were 75% and 25%, respectively. Combination treatment of HCC appears to be efficacious for tumor stages I and II.

Adult↗
PubMed1992

The mechanism of perturbation in monoamine metabolism by L-dopa therapy: in vivo and in vitro studies.

In the cerebrospinal fluid of the patients with Parkinson's disease treated with L-DOPA, L-3-O-methyldopa was the major metabolite of administered L-DOPA. Using a dopaminergic cell model, clonal rat phenochromocytoma PC 12h cells, and by microdialysis of the rat striatum it was proved that L-3-O-methyldopa was taken up into monoamine neurons by transport system specific for aromatic L-amino acids and inhibited transport of L-DOPA and other amino acids competitively. L-3-O-Methyldopa depleted allosteric regulation of the biopterin cofactor on activity of tyrosine hydroxylase, the rate-limiting enzyme of catecholamine synthesis. Depletion of the allostery may perturb the buffer action of endogenous L-DOPA synthesis that stabilizes dopamine level in the brain. By these mechanisms L-3-O-methyldopa may reduce clinical effectiveness of administered L-DOPA and be involved in wearing-off phenomenon. L-DOPA inhibited the activity of tryptophan hydroxylase and thus serotonin synthesis, which may be related to psychiatric side-effects in the patients under L-DOPA therapy.

Aged↗
PubMed1992

Allosteric effect of tetrahydrobiopterin cofactors on tyrosine hydroxylase activity.

Allostery of tyrosine hydroxylase was found by kinetical studies of partially purified tyrosine hydroxylase from clonal rat pheochromocytoma PC12h cells. Positive cooperativity toward the cofactors, (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin [(6R)BH4] and (6S)-L-erythro-5,6,7,8-tetrahydrobiopterin [(6S)BH4], was observed. It is indicated that biopterin might be the regulatory factor of the enzyme polymers, which changes the affinity for the cofactor itself. Moreover, the stereochemical structure of (6R)BH4, the naturally-occurring cofactor, took an important role on the kinetical properties of the enzyme in concern with L-tyrosine.

Allosteric Regulation↗
PubMed1992

Inhibition of tryptophan hydroxylase by (R)- and (S)-1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinolines (salsolinols).

The (R)- and (S)-enantiomers of salsolinol, the dopamine-derived tetrahydroisoquinolines, were found to inhibit the activity of tryptophan hydroxylase (TPH), prepared from serotonin-producing murine mastocytoma P-815 cells. Inhibition of TPH by salsolinols was found to be non-competitive with the substrate L-tryptophan. Tryptophan hydroxylase is composed of two elements with different kinetic properties in terms of cofactor (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin and these two elements were inhibited by salsolinols in competitive and uncompetitive ways, respectively. Stereoselectivity of salsolinol was not observed, concerning the potency and the type of inhibition on PTH. These data indicate that salsolinols might be naturally occurring inhibitors of indoleamine metabolism.

Animals↗
PubMed1992

N-methylation of dopamine-derived 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, (R)-salsolinol, in rat brains: in vivo microdialysis study.

N-Methylation of (R)-1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)-salsolinol] derived from dopamine was proved by in vivo microdialysis study in the rat brain. The striatum was perfused with (R)-salsolinol and N-methylated compound was identified in the dialysate using HPLC and electrochemical detection with multichanneled electrodes. N-Methylation of (R)-salsolinol was confirmed in three other regions of the brain, the substantia nigra, hypothalamus, and hippocampus. In the substantia nigra, the amount of N-methylated (R)-salsolinol was significantly larger than in the other three regions. These results indicate that around dopaminergic neurons, particularly in the substantia nigra, (R)-salsolinol was methylated into N-methyl-(R)-salsolinol, which has a chemical structure similar to that of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, the selective dopaminergic neurotoxin. N-Methylation of tetrahydroisoquinolines and beta-carbolines have already been proven to increase their toxicity to dopaminergic neurons and N-methylation might be an essential step for these alkaloids to increase their toxicity. On the other hand, after perfusion of (R)-salsolinol, release of dopamine and 5-hydroxytryptamine was observed and inhibition of monoamine oxidase was indicated. (R)-Salsolinol and its derivatives may be candidates for being dopaminergic neurotoxins.

Animals↗
PubMed1992

Inhibition of tyrosine hydroxylase by R and S enantiomers of salsolinol, 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline.

Salsolinol is one of the dopamine-derived tetrahydroisoquinolines and is synthesized from pyruvate or acetaldehyde and dopamine. As it cannot cross the blood-brain barrier, salsolinol as the R enantiomer in the brain is considered to be synthesized in situ in dopaminergic neurons. Effects of R and S enantiomers of salsolinol on kinetic properties of tyrosine hydroxylase [tyrosine, tetrahydrobiopterin:oxygen oxidoreductase (3-hydroxylating); EC 1.14.16.2], the rate-limiting enzyme of catecholamine biosynthesis, were examined. The naturally occurring cofactor of tyrosine hydroxylase, L-erythro-5,6,7,8-tetrahydrobiopterin, was found to induce allostery to the enzyme polymers and to change the affinity to the biopterin itself. Using L-erythro-5,6,7,8-tetrahydrobiopterin, tyrosine hydroxylase recognized the stereochemical structures of the salsolinols differently. The asymmetric center of salsolinol at C-1 played an important role in changing the affinity to L-tyrosine. The allostery of tyrosine hydroxylase toward biopterin cofactors disappeared, and at low concentrations of biopterin such as in brain tissue, the affinity to the cofactor changed markedly. A new type of inhibition of tyrosine hydroxylase, by depleting the allosteric effect of the endogenous biopterin, was found. It is suggested that under physiological conditions, such a conformational change may alter the regulation of DOPA biosynthesis in the brain.

Adrenal Gland Neoplasms↗
PubMed1991

Presence of 2-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline and 1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, novel endogenous amines, in parkinsonian and normal human brains.

2-Methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline and 1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline were identified for the first time as novel endogenous amines in parkinsonian and normal human brains by gas chromatography-mass spectrometry. It is of interest that these tetrahydroisoquinolines are analogues of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) which produces Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1991

Reduction of enzymatic activity of tyrosine hydroxylase by a heterocyclic amine, 3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole (Trp-P-1), was due to reduced affinity to a cofactor biopterin.

A carcinogenic, food-derived heterocyclic amine, 3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole (Trp-P-1) was found to reduce the enzymatic activity of tyrosine hydroxylase in clonal rat pheochromocytoma PC12h cells, by its supplement to the culture medium. The reduction was observed with 10 microM Trp-P-1, and at this concentration the amount of cell protein and the activity of a non-specific enzyme, beta-galactosidase, were not affected. The mechanism of the reduction of the enzyme activity was clarified by kinetical studies. The amine reduced the affinity of tyrosine hydroxylase to a cofactor, tetrahydrobiopterin. The alteration of the enzymatic properties by Trp-P-1 was discussed in relation to the possible effect on catecholamine metabolism in the brain.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Inhibition of tryptophan hydroxylase by food-derived carcinogenic heterocyclic amines, 3-amino-1-methyl-5H-pyrido[4,3-b]indole and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole.

Food-derived and carcinogenic heterocyclic amines, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), were found to inhibit the activity of tryptophan hydroxylase (TPH) prepared from serotonin-producing murine mastocytomas, P-815 cells. Inhibition of TPH by Trp-P-2 was found to be competitive with the substrate L-tryptophan and non-competitive with the cofactor (6R)-L-erythro-5,6,7, 8-tetrahydrobiopterin. The inhibition proved to be reversible; by dialyzing the sample incubated with Trp-P-2, the enzyme activity could be fully recovered. Among a series of heterocyclic amines examined, Trp-P-1, Trp-P-2 and some other heterocyclic amines inhibited TPH activity. Trp-P-2 and other heterocyclic amines were the newly discovered naturally occurring inhibitors of the indoleamine metabolism.

Animals↗
PubMed1991

Effects of morphine administration on catecholamine levels in rat brain; specific reduction of epinephrine concentration in hypothalamus.

The effects of morphine administration on concentrations of epinephrine, norepinephrine and dopamine were examined in the rat brain. Morphine injection reduced the epinephrine level only in the hypothalamus, while the norepinephrine level was reduced in the hypothalamus, medulla, and locus coeruleus. The dopamine concentration was elevated in all regions examined. These changes were blocked by administration of naloxone. Repeated injection of morphine for 14 days did not affect any catecholamine level. In naloxone-induced withdrawal, epinephrine was most markedly depleted in hypothalamus. These observations suggest that the epinephrine level in hypothalamus is affected by morphine acting on opioid receptors.

Animals↗
PubMed1991

Effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in prenatal stage on the dopamine system in the postnatal mouse brain.

A dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP), administered to a pregnant female was found to affect postnatally the catecholamine metabolism of the pups. MPTP (5 mg/kg body weight/day) was administered to pregnant C57 Black BYA mice daily for 7 days between the 12th and 18th day of gestation. Dopamine levels and tyrosine hydroxylase (TH) activity were measured in the whole brain from the pups sacrificed after birth. In MPTP-treated pups at 7 days of age, TH total activity (TH activity/brain) did not change (92% of the control value), while TH specific activity (TH activity/mg protein) was increased to 163% of that in control mice. Thus, TH homospecific activity (TH activity/mg TH protein) doubled compared to the control mice. At 28 days of age, both the total activity and the specific activity of TH in the brains of postnatal mice were reduced to 50% and 78% of the control, respectively. Dopamine concentration in the striatum was also reduced significantly. Reduction in the TH activity and dopamine concentration were also observed at the age of 12 weeks. These data suggest that the prenatal exposure to MPTP induced a prolonged reduction of TH activity in the brains of mice with a transient increase of TH homospecific activity during the postnatal period.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1991

Distribution of peptidases in cultured cells from middle ear mucosa: prolyl endopeptidase is localized in fibroblasts and dipeptidyl peptidase IV and II in epithelial cells.

To examine the distribution of prolyl endopeptidase (PEP), dipeptidyl peptidase IV (DPP IV), and dipeptidyl peptidase II (DPP II) in specific cell types, fibroblasts and epithelial cells were selectively cultured from middle ear mucosal tissues of guinea pigs. In fibroblasts, PEP had the highest activity, 12.28 +/- 4.00 nmole/min/mg protein (mean +/- SD), 45-fold higher than corresponding DPP II levels. In epithelial cells, DPP IV activity was the highest, 6.48 +/- 0.90 nmole/min/mg protein. This communication describes, for the first time, the distribution of the enzyme activities of PEP, DPP IV, and DPP II in fibroblasts and epithelial cells, and the occurrence of PEP in fibroblasts.

Animals↗
PubMed1991

[Combination of transarterial chemoembolization and endocrine therapy for liver metastases of breast cancer].

Nine patients with multiple metastases including liver from breast cancer were treated with transarterial chemoembolization through hepatic artery using 40-50 mg of 4'-epi-adriamycin and Lipiodol, followed by 800-1,200 mg/day of medroxyprogesterone acetate. Of 9 patients thus treated, there were 4 partial response (44%), 2 no change and 3 progressive disease. Duration of disease control ranged from 4 to 46 months (mean 24.5 months). Seven out of 9 patients died within 6 to 37 months (mean 15.3 months) after diagnosis of liver metastases. The 3- and 5-year survival rates were 45% and 11%, respectively. We conclude that this therapy is a useful treatment modality for controlling liver metastases of breast cancer.

Adult↗