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PubMed1983

[Methods and their evaluation for the estimation of vitamin B6 levels in man. 5. Serum pyridoxal-5-phosphate determination: method and comparison of methods].

Methods and Their Evaluation to Estimate the Vitamin B6-Status in Human Subjects. V. S-PLP-Determination: Method and Comparison of Methods. A method to determine the plasma pyridoxal 5-phosphate (PLP) basing on the enzymatic decarboxylation of 1-14C-l-tyrosine and the measurement of the radio-active 14CO2 is described. Its efficiency is discussed in comparison with other methods. High specificity, precision, accuracy, and sensitivity are demonstrated. The developed equipment allows to analyse a great number of samples and minimizes the risk of radio-active contamination. The commercial apoenzyme preparations are different in quality and require purification. Apoenzyme lots with high genuine content of PLP are useless. Storage tests at 4 degrees C, -18 degrees C, and -196 degrees C show stability of the samples for one day, 30 days, and at least 10 weeks.

Carbon Radioisotopes↗
PubMed1995

Modulation of key reactions of the catecholamine metabolism by extracts from Eschscholtzia californica and Corydalis cava.

Aqueous-alcoholic extracts from Eschscholtzia californica inhibit the enzymatic degradation of catecholamines as well as the synthesis of adrenaline, whereas aqueous-ethanolic extracts from Corydalis cava enhance the chemical oxidation of adrenaline and the synthesis of melanine from dihydroxyphenylalanine (DOPA). Both extracts dramatically shorten the lag phase in the catalysis of phenolase probably due to their o-diphenol content, where the Corydalis extracts are 10 times more active than the Eschscholtzia preparations. Dopamine beta-hydroxylase and monoamine oxidase (MAO-B) are especially inhibited by Eschscholtzia extracts. Diamine oxidases are inhibited by both preparations to a similar extent. The results of this study may be interpreted as a cooperative function of the two preparations in establishing and preserving high catecholamine levels thus explaining their sedative, antidepressive and hypnotic activities.

Alkaloids↗
PubMed1998

Effects of diabetes and difluoromethylornithine treatment on hyperplasia, activity of MAP-kinase, and activity and association with cyclin B of p34cdc2 kinase in rat jejunal mucosa.

BACKGROUND: The different signal transduction pathways of rapidly proliferating cells of the intestine are not clearly understood. We report here a possible signaling pathway that involves regulation of activity of two closely related kinases, MAP-K (mitogen-activated protein kinase) and p34cdc2 kinase, during hyperplasia of diabetic jejunal mucosa. Our aim was to investigate the activity and phosphorylation of MAP-K and activity and association of p34cdc2 kinase with cyclin B during diabetes-induced jejunal mucosal hyperplasia in vivo. METHODS: We studied untreated and difluoromethylornithine (DFMO) treated control rats and rats with streptozotocin-induced type I diabetes. Assays were done 10 days after the induction of diabetes. In diabetic rats there was jejunal hyperplasia as indicated by increases in the jejunal mucosal weight/cm and DNA content as well as increased activities of MAP-K and p34cdc2 kinase and association of the latter with cyclin B as compared to corresponding values in control rats. Administration of DFMO, an irreversible inhibitor of the proliferation-associated enzyme ornithine decarboxylase (ODC), prevented diabetes-I induced jejunal hyperplasia and decreased all of the above enzymic parameters in both diabetic and control rats. In our previous in vivo study, DFMO administration also blocked diabetic jejunal hyperplasia and in addition decreased ornithine decarboxylase and tyrosine kinase activities jejunal and tyrosine phosphorylation of proteins. CONCLUSION: Thus the jejunal mucosal hyperplasia found in diabetes appears to involve activation of signal transduction pathways involving tyrosine kinases, MAP-K, p34cdc2 kinase, and cyclin B.

Animals↗
PubMed1988

Effects of systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to mice on tyrosine hydroxylase, L-3,4-dihydroxyphenylalanine decarboxylase, dopamine beta-hydroxylase, and monoamine oxidase activities in the striatum and hypothalamus.

The effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (30 mg/kg subcutaneously per day for 8 days) to C57BL/6N mice were studied on tyrosine hydroxylase (TH), L-3,4-dihydroxyphenylalanine decarboxylase (DDC), and monoamine oxidase (MAO) activities in the striatum, and TH, DDC, dopamine-beta-hydroxylase (DBH), and MAO activities in the hypothalamus. Treatment with MPTP led to a large decrease in TH activity and a parallel decrease in DDC activity in the striatum, as compared with the saline controls. In contrast, MPTP administration did not cause a decrease of the activities of TH, DDC, and DBH in the hypothalamus. There was also no reduction in MAO activities of striatum and hypothalamus. These data indicate that MPTP administration to mice results in specific degeneration of the dopaminergic nigrostriatal pathway and that DDC in the mouse striatum may mainly be localized in the dopaminergic neurons with TH.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2001

Histamine deficiency suppresses murine haptoglobin production and modifies hepatic protein tyrosine phosphorylation.

Histidine decarboxylase (HDC) synthesizes endogenous histamine from histidine in mammals. HDC-deficient mice (HDC-/-), if kept on a histamine-free diet, have no histamine in their tissues. HDC-/- mice show multiple phenotypes. In this study we show that both the constitutively expressed and turpentine-induced level of an acute-phase protein, haptoglobin, is significantly lower in the serum of HDC-/- mice compared to that of wild-type animals. This effect was abolished if HDC gene-targeted mice received histamine-rich food. No differences were found when lipopolysaccharide (LPS) was used to induce the acute-phase reaction. Using specific antibodies to phosphorylated tyrosine, we showed that protein tyrosine phosphorylation (Y-P) of approximately 50- and 26- to 27-kDa liver proteins is significantly decreased in HDC-/- mice, but that the difference was largely diminished if the animals were kept on a histamine-rich diet, suggesting that the phenotype with lower haptoglobin production is diet inducible. Upon in vivo treatment with LPS, Y-P band intensity decreased, regardless of the presence or absence of histamine. Identification of elements of the signalling pathway with decreased phosphorylation may elucidate the molecular background of the effect of endogenous histamine in the hepatic acute-phase reaction.

Acute-Phase Reaction↗
PubMed1986

Evaluations of tyrosine apodecarboxylase assays for pyridoxal phosphate.

The alternate procedures used in the tyrosine apodecarboxylase assays for pyridoxal 5'-phosphate were evaluated to determine optimal conditions. Two preparations of tyrosine apodecarboxylase from Streptococcus faecalis were used: a cell suspension and a partially purified cell-free form. The activity of the decarboxylase was measured in two different assays using [14C]tyrosine or [3H]tyrosine as substrate. The presence of serum proteins caused greater inhibition of the assay for serum pyridoxal phosphate using [14C]tyrosine as substrate than the assay with [3H]tyrosine. In contrast, addition of deproteinized serum extract did not appear to inhibit either assay. The rate of reconstitution of the apodecarboxylase in the cell suspension was at least four times slower than that of the cell-free enzyme. The rate of reconstitution of the cell-free enzyme was faster in acetate than in citrate buffer. Inorganic sulfate or phosphate, at normal plasma concentrations, did not alter either the reconstitution rate of tyrosine decarboxylase or the final activity obtained in the assays using either substrate. The tyrosine apodecarboxylase assay for pyridoxal phosphate can be optimized by using deproteinized sera or plasma and incubating the cell-free apoenzyme with the coenzyme in acetate buffer for a time sufficient to obtain maximum reconstitution.

Acetates↗
PubMed1985

Inhibition of monoamine oxidase selectively in brain monoamine nerves using the bioprecursor (E)-beta-fluoromethylene-m-tyrosine (MDL 72394), a substrate for aromatic L-amino acid decarboxylase.

(E)-beta-Fluoromethylene-m-tyrosine (FMMT) is a dual-enzyme-activated inhibitor of monoamine oxidase (MAO). The compound is not an inhibitor per se but is decarboxylated by aromatic L-amino acid decarboxylase (AADC) to yield a potent enzyme-activated irreversible inhibitor of MAO, (E)-beta-fluoromethylene-m-tyramine, which shows some selectivity for inhibition of MAO type A. Decarboxylation of FMMT was demonstrated in vitro using hog kidney AADC and in vivo in rats by the ability of alpha-monofluoromethyldopa (MFMD), a potent inhibitor of AADC, to prevent MAO inhibition produced by FMMT. In isolated synaptosomes, FMMT was decarboxylated by AADC, and, furthermore, the compound was actively transported into these isolated nerve endings. An active transport into the CNS has also been demonstrated in vivo by performing competition experiments with leucine. To demonstrate that FMMT is preferentially decarboxylated within monoamine nerves of the CNS, the nigrostriatal 3,4-dihydroxyphenylethylamine (dopamine) pathway of rats was unilaterally lesioned with 6-hydroxydopamine or infused with MFMD. Under these conditions, MAO inhibition produced by orally administered FMMT in the striatum ipsilateral to the lesion or infusion was markedly attenuated. Combination of FMMT with an inhibitor of extracerebral AADC, such as carbidopa, protected peripheral organs against the MAO inhibitory effects and concomitantly enhanced MAO inhibition in the CNS. Such combinations had a greatly reduced propensity to augment the cardiovascular effects of intraduodenally administered tyramine, when compared with FMMT given alone or with clorgyline, a selective inhibitor of MAO type A. The results obtained with FMMT suggest the possibility of achieving selective inhibition of MAO within monoamine nerves of the CNS and, further, suggest that combination of FMMT with an inhibitor of extracerebral AADC will reduce the propensity of this inhibitor to produce adverse interactions with tyramine.

Animals↗