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Biomedical subjects

N Seiler

Publications and source records attributed to N Seiler.

At least 109 records · Page 6Linked to original sources
PubMed1985

Determination of amino acids by separation of their ion pairs with dodecyl sulphate.

The ion pairs of amino acids with dodecyl sulphate were separated on a reversed-phase column (Beckman Ultrasphere I.P.) using a sequence of eluents that are prepared by mixing 0.2 M phosphoric acid (containing 10 mM sodium dodecyl sulphate), 0.2 M sodium acetate (pH 4.50; containing 10 mM sodium dodecyl sulphate) and methanol. the amino acids commonly occurring in tissues, except taurine and related weakly basic amino acids, can be analysed at a rate of 95 min per sample at a sensitivity of less than 50 pmol per amino acid. Elution modes for specific amino acids (alpha-difluoromethylornithine, gamma-vinyl-4-aminobutyric acid, 4-aminobutyric acid, putreanine) and non-essential amino acids that allow higher separation rates are reported. The method is suitable for fully automated routine amino acid analysis.

Amino Acids↗
PubMed1985

Specific inhibition of polyamine oxidase in vivo is a method for the elucidation of its physiological role.

N1-Methyl-N2-(2,3-butadienyl)-1,4-butanediamine (MDL 72521) and N1,N2-bis(2,3-butadienyl)-1,4-butanediamine (MDL 72527) are specific, potent, enzyme-activated, irreversible inhibitors of polyamine oxidase in vitro. These compounds are also capable of completely inhibiting polyamine oxidase in mouse tissues at intraperitoneal doses greater than 20 mg/kg. Enzyme activity reappears in the various organs within 2-3 days to 50% of the control values. Irreversible inhibition of polyamine oxidase in mice led to decreased putrescine (30-40%) and spermidine (10-20%) levels in liver and some other organs. At the same time N1-acetylspermidine and, to a lesser extent, N1-acetylspermine were accumulating at rates which are assumed to be related to the rates of polyamine degradation. Even after treatment with polyamine oxidase inhibitors over a period of 6 weeks at doses which produced complete inhibition of polyamine oxidase in all organs, including the brain, neither toxic effects nor changes in body weight or behaviour were observed.

Animals↗
PubMed1985

The influence of catabolic reactions on polyamine excretion.

Complete inhibition of polyamine catabolism is possible by combined administration of two compounds. Aminoguanidine (25 mg/kg body wt., intraperitoneally) inhibits all reactions that are catalysed by copper-containing amine oxidases (CuAO). The products of the CuAO-catalysed reactions cannot be reconverted into polyamines (terminal catabolism) and therefore usually escape observation. N1-Methyl-N2-(buta-2,3-dienyl)butane-1,4-diamine (MDL 72521) is a new inhibitor of polyamine oxidase. It inhibits completely the degradation of N1-acetylspermidine and N1-acetylspermine. The enhanced excretion of N1-acetylspermidine in urine after administration of 20 mg of MDL 72521/day per kg body wt. is a measure of the rate of spermidine degradation in vivo to putrescine, and thus of the quantitative significance of the interconversion pathway. From the enhancement of total polyamine excretion by aminoguanidine-treated rats, one can calculate that only about 40% of the polyamines that are destined for elimination are usually observed in the urine, the other 60% being catabolized along the CuAO-catalysed pathways. The normally observed urinary polyamine pattern gives, therefore, an unsatisfactory picture of the actual polyamine elimination. Although aminoguanidine alone is sufficient to block terminal polyamine catabolism, rats that were treated with a combination of aminoguanidine and MDL 72521 excrete more polyamines than those that received aminoguanidine alone. The reason is that a certain proportion of putrescine, which is formed by degradation of spermidine, is normally reutilized for polyamine biosynthesis. In MDL 72521-treated animals this proportion appears in the urine in the form of N1-acetylspermidine. Thus it is possible to determine polyamine interconversion and re-utilization in vivo and to establish a polyamine balance in intact rats by using specific inhibitors of the CuAO and of polyamine oxidase.

Animals↗
PubMed1985

Polyamine reutilization and turnover in brain.

N1,N2-bis-(2,3-butadienyl)-1,4-butanediamine (MDL 72527) is an irreversible, specific inhibitor of polyamine oxidase, which allows one to completely inactivate this enzyme in all organs of an experimental animal. As a result one observes a linear increase of N1-acetylspermidine and N1-acetylspermine concentrations in brain. The rate of accumulation seems directly proportional to the rate of spermidine, and spermine degradation respectively, and since no compensatory changes of the polyamine synthetic enzymes were induced by inhibition of polyamine oxidase, the rate of acetyl-polyamine accumulation is assumed to be a measure for polyamine turnover. The decrease of brain putrescine levels by 70 percent in the brains of MDL 72527-treated animals suggests the quantitative significance of putrescine reutilisation. Pretreatment of the animals with D,L-alpha-difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase reduced both, polyamine turnover rate and the extent of putrescine reutilization. Inhibition of GABA-T produced a significant increase of polyamine turnover in brain, in agreement with the known induction of ornithine decarboxylase activity after treatment with inhibitors of GABA-T.

Alkynes↗
PubMed1985

Amplification by glycine of the anticonvulsant effect of THPO, a GABA uptake inhibitor.

THPO, a GABA uptake inhibitor, when given in doses of up to 4 mmol/kg (i.p.) to mice, had only a marginal protective effect against seizures induced 1 hr later by 3-mercaptopropionic acid (MPA). THPO (4 mmol/kg), when given in combination with 10 mmol/kg of glycine, protected 60% of the mice from MPA-induced convulsions. The combination of THPO and glycine delayed the onset of metrazol-induced clonic convulsions and protected 30% of the animals from seizures, although neither glycine or THPO alone had a significant anticonvulsant effect against metrazol induced seizures. In agreement with earlier findings, the results presented in this work seem to indicate that the synergistic anticonvulsant effects of glycine and GABAergic agents are independent of their mode of action: the effects of GABA agonists (muscimol) GABA-T inhibitors (vinylGABA), or an inhibitor of glial GABA uptake (THPO) are similarly amplified by glycine.

3-Mercaptopropionic Acid↗
PubMed1984

Decreased protein-synthetic activity is an early consequence of spermidine depletion in rat hepatoma tissue-culture cells.

Hepatoma tissue-culture (HTC) cells were exposed to DL-alpha-difluoromethylornithine (DFMeOrn), a specific irreversible inhibitor of ornithine decarboxylase. Concomitantly with the decrease in spermidine, a decrease in the amount of ribosomes in polyribosomes was observed. Spermine concentrations remained essentially comparable with those in cells not exposed to this inhibitor. Exposure of putrescine- and spermidine-depleted HTC cells to spermidine or spermine rapidly reversed the effect of DFMeOrn on polyribosome profiles, whereas addition of putrescine to the cell culture medium had an effect only after its transformation into spermidine and spermine. The results show that the perturbation of polyribosome formation in DFMeOrn-treated HTC cells is due to spermidine deficiency and that a normal polyamine complement is required for optimal protein-synthetic activity in these cells. The results also indicate that protein synthesis is perturbed before DNA synthesis during depletion of putrescine and spermidine in HTC cells.

Animals↗
PubMed1984

Synergistic anticonvulsant effects of GABA-T inhibitors and glycine.

The anticonvulsant effect of inhibitors of GABA-T (R/S-gamma-vinyl-GABA, ethanolamine-O-sulfate, gabaculine, aminooxyacetic acid) was enhanced by 10 mmol/kg glycine in animal seizure models which are based on a functional GABA deficit. Similar to glycine in their action, although less effective, were its close structural analogues (sarcosine, N,N-dimethylglycine) and homologous omega-aminoacids (beta-alanine, taurine, gamma-aminobutyric acid, delta-aminovaleric acid). It is assumed that glycine and its structural analogues act on supraspinal glycine receptors as glycine agonists. Our observation is the first example of the synergistic interaction of two inhibitory neuronal systems resulting in the amplification of the anticonvulsant effect. Combined treatment with GABA-T inhibitors and glycine may turn out to be of practical importance in the therapy of seizure disorders and other diseases, for which treatment with GABA-T inhibitors is considered a potentially useful therapeutic approach.

3-Mercaptopropionic Acid↗
PubMed1984

Polyamines and the development of isolated neurons in cell culture.

The possible role of polyamines in the development of isolated neuroblasts from the cerebral cortex of embryonic chick brain was studied by means of three enzyme activated irreversible inhibitors of ornithine decarboxylase. alpha-Difluoromethylornithine (MDL 71782) showed no effects on development at doses which depleted dramatically neuronal putrescine and spermidine levels. In contrast, the two other inhibitors, (E)-alpha-(fluoromethyl)dehydroputrescine (MDL 72197) and 6-heptyne-2,5-diamine (MDL 72175) blocked the formation of neuronal outgrowths completely at 100 microM and higher concentrations. Their effects on neuronal polyamines differed at this concentration considerably. The growth inhibitory effect of the ornithine decarboxylase inhibitors was in all cases reversible: cells which were grown after 3 days of exposure to the drugs in normal medium produced neuronal networks. The presence of putrescine at 10 microM concentration in the culture medium prevented the growth inhibitory effect of 100 microM concentrations of the drugs. This concentration of putrescine was not only capable of preventing, but also of reversing growth inhibition by the ornithine decarboxylase inhibitors. Although the cellular polyamine levels were not correlated with the morphological development of chick embryo cortical neurons, the present study leaves no doubt that putrescine plays an essential role in neuronal differentiation.

Alkynes↗
PubMed1984

Synergistic anticonvulsant effects of a GABA agonist and glycine.

Administration of muscimol to mice in subcutaneous doses between 0.34 and 1.25 mg/kg produced partial protection against 3-mercaptopropionic acid (MPA)-induced seizures. Glycine at a dose of 750 mg/kg (10 mmol/kg) protected 20% of the animals 45 min after its administration. Combined treatment with the two compounds gave a near to complete protection against MPA-induced seizures. These observations suggest that the concomitant enhancement of glycinergic and GABAergic activities amplify the anticonvulsant effect of these neuronal systems against seizures induced by impairment of GABA-mediated transmission.

3-Mercaptopropionic Acid↗
PubMed1984

The amplification of the anticonvulsant effect of vinyl GABA (4-aminohexenoic acid) by esters of glycine.

The synergistic amplification of the anticonvulsant effects of direct and indirect GABA agonists by glycine has previously been demonstrated. We show in the present report that the anticonvulsant effect of vinyl GABA, a GABA-T (4-aminobutyrate: 2-oxoglutarate aminotransferase) inhibitor with antiepileptic efficacy, can be amplified by esters of glycine. Among the compounds studied glycine tert. butylester was the most promising. It was effective at a lower dose and had a considerably longer duration of action than glycine. From the observed glycine and glycine tert. butylester levels it is evident that glycine tert. butylester is rapidly hydrolysed within brain and other tissues. It is therefore a pro-drug of glycine, capable of enhancing central glycinergic activity.

3-Mercaptopropionic Acid↗
PubMed1983

Anticonvulsant effects of some inhibitory neurotransmitter amino acids.

The anticonvulsive effects of GABA, taurine, and glycine were investigated on several chemically-induced and genetic seizure models. Intravenous injections of either GABA, taurine, or glycine provided protection against 3-mercaptopropionic acid (MPA)-induced convulsions in adult Swiss mice. GABA was partially effective against isonicotinic acid hydrazide and was without effect against bicuculline-induced convulsions. Prolonged administration of glycine prevented MPA-induced convulsions but not electrically induced seizures or seizures induced by strychnine or metrazol. Intragastric glycine protected young audiogenic seizure-susceptible DBA/2 mice against all three phases of sound-induced convulsions (wild running, clonic and tonic seizure), but GABA and taurine provided little or no protection. With increase of glycine, the cerebral levels of glutamine and serine also increased, but that of glutamic acid decreased. The endogenous glutamic and glycine levels were slightly higher in the brains of the audiogenic seizure-susceptible DBA/2 mice than in that of the resistant BALB/Cy strain.

Acoustic Stimulation↗
PubMed1983

N-(3-aminopropyl)pyrrolidin-2-one: a physiological excretory product deriving from spermidine.

Normal human and rat urine contain N-(3-aminopropyl)pyrrolidin-2-one. This compound was identified by its chromatographic behaviour on a reversed phase column, by thin-layer chromatography of its dansyl derivative, and by mass spectrometry. Evidence for the presence of conjugates of N-(3-aminopropyl)pyrrolidin-2-one in urine was obtained by the fact that partial acid hydrolysis increases the amount of this compound, whereas prolonged hydrolysis leads to its transformation into isoputreanine (N1-(3-carboxypropyl)-1,3-diamino-propane). Although it is likely that the monoacetylderivative of N-(3-aminopropyl)pyrrolidin-2-one is prominent among the conjugates, since this compound can be formed from N1-acetylspermidine, other types of conjugates are also likely. A method is reported suitable for the measurement of N-(3-aminopropyl)pyrrolidin-2-one and of isoputreanine in urine and urine hydrolysates, respectively. Administration of spermidine enhances the amount of urinary excretion of N-(3-aminopropyl)pyrrolidin-2-one. Of 0.1 mmol . kg-1 of spermidine administered intraperitoneally to rats around 12% are transformed into this compound and its conjugates. Treatment of rats with aminoguanidine sulfate, an inhibitor of diamine oxidase, causes a decrease in the excretion of N-(3-aminopropyl)pyrrolidin-2-one and its derivatives. These findings are in agreement with the assumption that N-(3-aminopropyl)pyrrolidin-2-one, the gamma-lactam of isoputreanine, is a physiological degradation product of spermidine. Its formation is catalyzed by an aminoguanidine sensitive, diamine oxidase-like enzyme.

Animals↗
PubMed1982

N-(3-aminopropyl)pyrrolidin-2-one, a product of spermidine catabolism in vivo.

A high-pressure-liquid-chromatographic method suitable for the separation and sensitive detection of putreanine and isoputreanine is described. This method allowed us to study the formation of the metabolites of the oxidative deamination of spermidine and N1-acetylspermidine. Administration of spermidine trishydrochloride to mice causes a time-dependent accumulation of putreanine and N-(3-aminopropyl)pyrrolidin-2-one in various organs. The latter compound yields isoputreanine by hydrolysis. It can be assumed that the analogous lactam. N-(3-acetamidopropyl)pyrrolidin-2-one is formed from N1-acetylspermidine, since hydrolysis of tissue extracts of N1-acetylspermidine-treated mice produced isoputreanine. No putreanine is formed under these conditions. Pretreatment of the animals with 25 mg of aminoguanidine sulphate/kg body wt. completely inhibits the formation of putreanine and of the respective isoputreanine precursor from spermidine and N1-acetylspermidine. This suggests a role for a diamine oxidase-like enzyme in the oxidative deamination of spermidine and N1-acetylspermidine.

Amino Acids, Diamino↗
PubMed1981

On the formation of amino acids deriving from spermidine and spermine.

Evidence obtained from experiments with rats and mice is presented suggesting that the naturally occurring amino acids putreanine and N8-(2-carboxyethyl)spermidine, and most probably also related compounds deriving from the polyamines spermidine and spermine by oxidative metabolism, are formed within two anatomical compartments. In the first step polyamines are converted into aldehydes by serum spermine oxidase in the circulation. A certain portion of these aldehydes can be taken up by liver and other organs and transformed by aldehyde dehydrogenase into the corresponding amino acids. Putreanine is not only derived from spermidine, but can also be formed from N8-(2-carboxyethyl)spermidine by oxidative deamination, catalysed by serum spermine oxidase, and subsequent spontaneous elimination of acrolein.

Amino Acids↗
PubMed1981

The determination of N1-acetylspermine in mouse liver.

N1-Acetylspermine has been postulated to be an intermediate in the conversion of spermine to spermidine. This compound, together with N1-acetylspermidine has now been detected in the liver of mice which were pretreated with tetrachloromethane. The following methods were used for the identification of N1-acetylspermine: (a) High-pressure liquid-chromatography of the non-derivatized amines on a reversed-phase column, using octane sulfonate for ion-pairing. (b) Thin-layer chromatography of the dansyl derivatives. (c) Mass spectrometry of the dansyl derivatives. Both chromatographic methods allowed the quantitative estimation of N1-acetylspermine and N1-acetylspermidine in the liver of tetrachloromethane-treated animals.

Animals↗
PubMed1981

UV-induced changes in urinary polyamine excretion in the mouse.

Exposure of hairless mice to the light of a germicidal lamp (254 nm) under conditions which are known to induce epidermal DNA synthesis, cell proliferation, and polyamine metabolism produced a marked increase of polyamine excretion in the urine which lasted for many days. The increase was about the same for free and acetylated polyamines. Although the ratio of N1-acetylspermidine/N8-acetylspermidine increased somewhat in the urine of animals exposed to UV, the increase was not significant enough to be useful as a marker of enhanced cell proliferation. A single topical dose of alpha-difluoromethylornithine, a selective inhibitor or ornithine decarboxylase, prevented the UV-induced increase of polyamine excretion in agreement with its effect on UV-induced epidermal polyamine turnover.

Acetylation↗