Biomedical subjects

N Castagnoli

Publications and source records attributed to N Castagnoli.

At least 109 records · Page 6Linked to original sources

PubMed1986

Oxidative ionic metabolites of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP): correlation of electroreduction with physiological behavior.

Electrochemical studies (reduction potential and reversibility) were performed on 1-methyl-4-phenylpyridinium (MPP+) and 1-methyl-4-phenyl-2,3-dihydropyridinium (MPDP+). MPP+ gave reduction potentials in the range of -1.09 to -1.11 V in organic solvents in a process which was reversible. The reduction potential of MPDP+ was -0.64 V (irreversible). Possible relationships involving the electrochemical properties, oxy radical formation, and biological activity of these and related iminium species are discussed.

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

PubMed1985

Stimulation of pheomelanogenesis in cultured B16 melanoma cells by 4-tertiary butylcatechol.

Intermediates of pheomelanin in tissue cultured B16 melanoma cells were analyzed by high performance liquid chromatography, and reduced glutathione (GSH), L-dopa, 2-[(L)-S-cysteinyl]-L-dopa (2-SCD) and 5-[(L)-S-cysteinyl]-L-dopa (5-SCD) were quantified. The effects of 4-tertiary butylcatechol (TBC), an antioxidant which causes skin depigmentation, on the levels of the intermediate were then examined. A concentration of 10(-4) M TBC increased the intracellular levels of GSH, 2-SCD and 5-SCD, whereas the L-dopa level was unchanged. The time-course of the increased intermediates corresponded to the elevation of glutathione-metabolizing enzyme activities previously reported by Kawashima et al. [J. invest. Derm. 82, 53 (1984)] in the same cell line exposed to 10(-4) M TBC. The findings establish chemical evidence that TBC stimulates pheomelanogenesis in melanocytes.

Animals↗

PubMed1985

Active uptake of MPP+, a metabolite of MPTP, by brain synaptosomes.

Mouse brain synaptosomal preparations were used to study uptake of N-methyl-4-phenylpyridine (MPP+), a metabolite of the neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). The uptake of [3H]-MPP+ by striatal synaptosomes was approximately 25 X greater than that of [3H]-MPTP, with a KM of 0.48 microM and a Vmax of 5.3 nmoles/g tissue/min. Uptake was Na+ dependent and inhibited by ouabain, cocaine and dopamine (Ki 0.12 microM). Synaptosomes prepared from the corpus striatum accumulated [3H]-MPP+ at a rate 5-10 times higher than preparations from other brain regions. This selective uptake of MPP+ may contribute to the specificity of the toxic effects of MPTP on nigrostriatal dopaminergic neurons.

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

PubMed1985

Potential bioactivation pathways for the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

The metabolism of the selective nigrostriatal toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been studied in rat brain mitochondrial incubation mixtures. The 1-methyl-4-phenylpyridinium species MPP+ has been characterized by chemical ionization mass spectral and 1H NMR analysis. Evidence also was obtained for the formation of an intermediate product which, with the aid of deuterium incorporation studies, was tentatively identified as the alpha-carbon oxidation product, the 1-methyl-4-phenyl-2,3-dihydropyridinium species MPDP+. Comparison of the diode array UV spectrum of this metabolite with that of the synthetic perchlorate salt of MPDP+ confirmed this assignment. The oxidation of MPTP to MPDP+ but not of MPDP+ to MPP+ is completely inhibited by 10(-7) M pargyline. MPDP+, on the other hand, is unstable and rapidly undergoes disproportionation to MPTP and MPP+. Based on these results, we speculate that the neurotoxicity of MPTP is mediated by its intraneuronal oxidation to MPDP+, a reaction which appears to be catalyzed by MAO. The interactions of MPDP+ and/or MPP+ with dopamine, a readily oxidizable compound present in high concentration in the nigrostriatum, to form neurotoxic species may account for the selective toxic properties of the parent drug.

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

PubMed1985

Metabolism of the nigrostriatal toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine by liver homogenate fractions.

The metabolic fate of the nigrostriatal toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been examined in rat and rabbit liver mitochondrial and rabbit liver microsomal preparations. The mitochondrial preparations rapidly oxidized MPTP, in a pargyline-sensitive reaction, to a polar material that was shown to contain the 1-methyl-4-phenylpyridinium species as the principal product. NADPH-supplemented microsomal preparations converted MPTP to two principal products: 4-phenyl-1,2,3,6-tetrahydropyridine and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine N-oxide. Carbon monoxide and SKF 525A selectively inhibited the oxidation of MPTP to the nor compound, indicating that this N-demethylation reaction is cytochrome P-450 catalyzed. Attempts to trap possible unstable iminium metabolites of MPTP in microsomal incubation mixtures with sodium cyanide led to the isolation of a monocyano adduct that proved to be the N-cyanomethyl derivative. Thus, hepatic mitochondrial and microsomal enzyme systems catalyze the oxidation of MPTP by different pathways, the former leading to the generation of species that may possess neurotoxic properties.

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

PubMed1985

Studies on the 1-methyl-4-phenyl-2,3-dihydropyridinium species 2,3-MPDP+, the monoamine oxidase catalyzed oxidation product of the nigrostriatal toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

The nigrostriatal toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is biotransformed by brain monoamine oxidase (MAO) to an unstable dihydropyridinium intermediate that reacts with cyanide ion to form an alpha-cyano-tetrahydropyridine adduct and, in the absence of cyanide ion, undergoes disproportionation to the 1-methyl-4-phenylpyridinium species MPP+ and MPTP. Comparison of the HPLC retention times, diode array UV, and chemical ion mass spectral characteristics of these products with those of synthetic standards led us to propose the 1-methyl-4-phenyl-2,3-dihydropyridinium species 2,3-MPDP+ and 6-cyano-1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine as tentative structure assignments for the dihydropyridinium metabolite and the cyano adduct, respectively. Results presented in this paper confirm the first assignment and establish that, although the proposed 6-cyano adduct is initially formed, the product that was isolated from the mitochondrial incubation mixtures of MPTP and sodium cyanide actually is the isomeric 2-cyano-1-methyl-4-phenyl-1,2,3,6 -tetrahydropyridine. On the basis of the selective incorporation of deuterium into these products, we provide rational mechanistic interpretations of the disproportionation reaction and the rearrangement of the cyano adducts. These results establish that the MAO-catalyzed bioactivation of MPTP leads to the formation of a variety of reactive molecules that are potentially cytotoxic to nigrostriatal cells.

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

PubMed1985

Conjugates of catecholamines. 5. Synthesis and beta-adrenergic activity of N-(aminoalkyl)norepinephrine derivatives.

A novel series of N-aminoalkyl congeners and model derivatives of norepinephrine has been synthesized. Compounds that were structurally related to epinephrine were prepared from fully protected intermediates. Alternatively, isoproterenol-related compounds were synthesized via reductive amination of preformed methyl ketone derivatives with norepinephrine. The beta-adrenergic activities of these new compounds were assessed through measurement of intracellular cyclic AMP accumulation in S49 mouse lymphoma cells and displacement of iodocyanopindolol (ICYP) from membrane preparations. Congeners that contained an underivatized primary amine function exhibited virtually no activity in these assays. However, when this amine function was acylated (e.g., to an amide, carbamate, urea, sulfonamide, etc.), the products exhibited generally increased beta-adrenergic activity, which was, however, strongly dependent on the nature of the acylating group and also the length of the spacer. In particular, a benzyl carbamate derivative containing a branched, seven-carbon spacer group was 40 times more potent than isoproterenol in the in vitro S49 assay.

Adrenergic beta-Agonists↗

PubMed1985

Conjugates of catecholamines. 6. Synthesis and beta-adrenergic activity of N-(hydroxyalkyl)catecholamine derivatives.

A new series of catecholamines has been prepared in which the N-alkyl substituent of dl-epinephrine or dl-isoproterenol has been extended by a methylene chain terminated by a hydroxyl group or derived functionality (e.g., carbamate or ester). These functionalized catecholamines (congeners) and model compounds were prepared with the goal of eventual attachment to polymeric carrier molecules. The beta-adrenergic agonist activity of the derivatives was evaluated in vitro by measuring the intracellular accumulation of cyclic AMP in S49 mouse lymphoma cells and by the displacement of iodocyanopindolol (ICYP). A n-butylcarbamate derivative (compound 15) was the most active compound in this series with a potency 190 times greater than dl-isoproterenol in the S49 assay. The biological results indicate that minor modifications in structure in the N-alkyl substituent of the catecholamine can influence the pharmacologic activity.

Adrenergic beta-Agonists↗

PubMed1984

Oxidation of the neurotoxic amine 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by monoamine oxidases A and B and suicide inactivation of the enzymes by MPTP.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a thermal breakdown product of a meperidine-like narcotic analgetic used by drug abusers as a synthetic heroin, causes Parkinsonian symptoms in humans and degeneration of the substantia nigra in monkeys. MPTP is oxidized by brain mitochondrial preparations in a process which is blocked by deprenyl and pargyline, implying catalysis by monoamine oxidase B. The present paper demonstrates that pure MAO B isolated from beef liver oxidizes MPTP 38% as fast as benzylamine with a comparable Km value. Additionally, MAO A, isolated from human placenta, oxidizes MPTP to the same product at about 12% of the rate of kynuramine, again with a comparable Km value. The latter reaction is blocked by clorgyline. Both forms of MAO are progressively inactivated by MPTP by a process which follows first order kinetics. This progressive inactivation and the fact that the activity of MAO B is not significantly regenerated following gel exclusion chromatography suggest the formation of a covalent adduct with enzyme. Thus, MPTP appears to be a suicide inactivator of MAO.

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

PubMed1984

Morphine metabolism revisited. II. Isolation and chemical characterization of a glutathionylmorphine adduct from rat liver microsomal preparations.

Incubation of tritium-labeled morphine and cold glutathione (GSH) or cold morphine and tritiated GSH with liver microsomal preparations obtained from phenobarbital-treated rats led to the identification by high performance liquid chromatography (HPLC) of a glutathionylmorphine adduct. Liquid secondary ion mass spectral analysis established the molecular weight of the metabolite to be 590 which corresponds to the mass of a mono-GSH-morphine adduct. High resolution (360 and 500 MHz) 1H-NMR experiments have led to the tentative assignment of the structure of this metabolite as 10-alpha-S-glutathionylmorphine. Based on both in vivo and in vitro data, the formation of this product appears to be mediated by cytochrome P-450 and to involve a reactive intermediate that may be responsible for the observed covalent binding of radiolabeled morphine to proteins and, at least in part, for the morphine-induced depletion of GSH in the rat.

Animals↗

PubMed1984

Metabolism of the neurotoxic tertiary amine, MPTP, by brain monoamine oxidase.

The neurotoxic chemical MPTP (1-methyl-4-phenyl-1,2,4,5-tetrahydropyridine) is metabolized by rat brain mitochondrial fractions at a rate of 0.91 +/- 0.02 nmoles/mg protein/min. The major metabolite has been identified as the 1-methyl-4- phenylpyridinium species. This biotransformation process is blocked by 10(-7) M deprenyl and pargyline. MPTP itself inhibited the metabolism of benzylamine by brain mitochondrial fractions. These results are discussed in terms of possible bioactivation mechanisms that may be associated with the neurodegenerative properties of MPTP .

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

PubMed1984

Dermatitis from cashew nuts.

Between April 4 and May 10, 1982, fifty-four individuals developed a poison ivy-like dermatitis 1 to 8 days after eating imported cashew nuts. The patients had a very pruritic, erythematous, maculopapular eruption that was accentuated in the flexural areas of the body. Three had blistering of the mouth and four had rectal itching. Nineteen volunteers (eleven ill and eight well) were patch-tested with 2.5 micrograms of poison ivy urushiol and an acetone extract of cashew nut shells. Patch testing did not predict illness since positive tests to both materials occurred in those who had been ill as well as in those who had been well. Absence of cashew nut shells from two thirds of the bags probably accounted for the lack of correlation between patch testing and illness. All nine who reacted to the cashew extract also reacted to poison ivy urushiol. The three who were not sensitive to poison ivy had no reaction to cashew extract. Mass spectrometry of the cashew shell extract suggested the presence of cardol , one of the allergens in cashew shell oil.

Adolescent↗

PubMed1984

Synthesis and physicochemical and neurotoxicity studies of 1-(4-substituted-2,5-dihydroxyphenyl)-2-aminoethane analogues of 6-hydroxydopamine.

In an attempt to evaluate the possible relationship between the neurotoxicity of 6-hydroxydopamine and the redox properties and electrophilic reactivity of the 6-hydroxydopamine-p-hydroquinone/p-quinone system, we have synthesized a series of 6-hydroxydopamine analogues in which the C4-hydroxy group is replaced with various electron-donating and electron-withdrawing substituents. With the aid of cyclic voltammetry, the formal oxidation potentials (E degrees ') for the p-hydroquinone/p-quinone redox couples and the rates of cyclization of the p-quinones to the corresponding p-iminoquinones were determined. As expected, electron-rich p-hydroquinones were easily oxidized to the p-quinones, which underwent cyclization slowly, whereas the oxidation of electron-poor p-hydroquinones required higher voltages and yielded p-quinones, which cyclized readily at pH 7.4. The neurotoxic potential of these compounds showed that in vivo destruction of noradrenergic terminals, as measured by inhibition of norepinephrine uptake by rat heart slices, occurred only with those analogues bearing electron-donating substituents. Potent neurotoxic properties were associated only with the 4-amino and 4-hydroxy derivatives, both of which form p-quinones, which do not cyclize readily at pH 7.4. These results support the thesis that the p-quinone derived from 6-hydroxydopamine may be an important species in the mediation of the neurodestruction caused by 6-hydrodopamine.

Animals↗

PubMed1984

Induction of suppressor T cells for lymph node cell proliferation after contact sensitization of mice with a poison oak urushiol component.

Contact sensitivity with properties of delayed-type hypersensitivity (DTH) can be induced in mice by 3-heptadecylcatechol (HDC, a component of poison oak urushiol oil). Sensitization is effected by painting on abdominal skin and is assessed by measuring ear swelling produced after ear challenge. Further studies on the nature of this sensitization were made by monitoring the induction of lymph node cell (LNC) proliferation (as indicated by increased in vitro uptake of [14C]-thymidine into DNA) after cutaneous treatment with HDC. Draining inguinal LNC proliferation peaked 5-6 days after abdominal application of HDC. LNC taken from sensitized mice at times later than this peak suppressed HDC-induced proliferation when transferred into recipient mice. Such suppressor cells were T lymphocytes as implied by their sensitivity to anti-Thy-1.2 antibody and complement. The suppressive effect appeared to have both specific and non-specific components. LNC containing these T suppressor cells could not suppress the optimal proliferation in vitro of previously sensitized cells, nor was suppressive activity observed against the induction of contact sensitization itself. Thus, although the suppressor cells appeared to act on the afferent phase of sensitization, they may not be directed against the effector cells of DTH.

Animals↗

PubMed1983

Pharmacokinetics and pharmacodynamics of vecuronium (ORG NC45) and pancuronium in anesthetized humans.

The pharmacokinetics and pharmacodynamics of vecuronium (25-50 micrograms/kg) and pancuronium (25-50 micrograms/kg) were determined in nine ASA class I or II patients anesthetized with nitrous oxide and halothane. Force of thumb adduction in response to supramaximal stimulation of the ulnar nerve was quantified and recorded. Serum concentrations of the muscle relaxants were determined for eight hours after their administration using a mass spectrometry assay. Data were analyzed by nonlinear regression and fit to a three-compartment pharmacokinetic model and a four-compartment pharmacodynamic model. Vecuronium had a more rapid clearance (5.2 +/- 0.7 ml X kg-1 X min-1; mean +/- SD) and a shorter elimination half-life (71 +/- 20 min) as compared with pancuronium (1.8 +/- 0.4 ml X kg-1 X min-1; 140 +/- 25 min). No other pharmacokinetic differences were found between the drugs. Pharmacodynamic analysis showed that the plasma concentration at steady state which produced a 50% neuromuscular blockade (Cpss 50) was similar for vecuronium and pancuronium. The authors conclude that the drugs are equivalent in their onset and potency; however, the more rapid clearance and shorter elimination half-life for vecuronium provides a kinetic basis for its shorter duration of neuromuscular blockade as compared with pancuronium.

Adult↗

PubMed1983

Pharmacokinetics and pharmacodynamics of 4-aminopyridine in anesthetized dogs.

The pharmacokinetics and pharmacodynamics of 4-aminopyridine (4-AP), a drug which antagonizes nondepolarizing neuromuscular blockade, were studied in seven anesthetized dogs. Using a constant infusion of pancuronium, force of the anterior tibialis contraction in response to stimulation of the sciatic nerve was depressed to 10% of the control tension (90% depression of twitch tension). After 20 min of steady state, 4-AP (1.0 mg/kg) was administered i.v. Serum, urine and bile samples were analyzed for 4-AP concentration at several intervals for 10 hr after administration of 4-AP, using a sensitive high-performance liquid chromatographic assay (1 ng/ml). Serum data best fit a three-compartment pharmacokinetic model. The volume of the central compartment was 412 +/- 352 ml/kg (mean +/- S.D.) and the volume of distribution at steady state was 2517 +/- 363 ml/kg. Initial half-lives were 1.1 +/- 0.7 and 25.4 +/- 11 min. The terminal elimination half-life was 125 +/- 23 min and total clearance was 21 +/- 4 ml/kg/min. Of the injected dose, 60 +/- 9% was recovered in the urine and only 0.01 +/- 0.01% of the dose was recovered in the bile in 10 hr. Inasmuch as renal clearance of 4-AP exceeded glomerular filtration rate we conclude that 4-AP undergoes tubular secretion into the urine. The pharmacodynamic results included an onset time of 14 +/- 8 min, peak effect (maximum percentage of antagonism of twitch tension depression) 97 +/- 27% and duration of action 219 +/- 54 min. We conclude that 4-AP has a longer serum elimination half-life and a longer and more variable duration of action than other antagonists (i.e., neostigmine and pyridostigmine) of nondepolarizing neuromuscular blockade.

4-Aminopyridine↗

PubMed1982

Ion-pair high-performance liquid chromatographic assay of 4-aminopyridine in serum.

An assay for the quantitative estimation of 4-aminopyridine in biological fluids has been developed using 2-aminopyridine as internal standard and ion-pair reversed-phase (C18) high-performance liquid chromatography with detection at 263 nm. A 7.5% solution o acetonitrile in water containing tetrabutylammonium iodide and sodium heptanesulfonate buffered at pH 3.0 provided excellent separation of the analytes from each other and from an interfering peak that was occasionally observed in the outdated human sera used in these studies. Sensitivity, specificity, precision, accuracy and reproducibility all were judged sufficient for the routine use of this assay for pharmacokinetic and pharmacodynamic studies.

4-Aminopyridine↗

PubMed1982

Derivatization of chiral amines with (S,S)-N-trifluoroacetylproline anhydride for GC estimation of enantiomeric composition.

The reaction characteristics of (S,S)-N-trifluoroacetylproline anhydride were examined in an attempt to develop a quantitative GC assay of the enantiomers of the sterically hindered, chiral amine ketamine. With the aid of the individual enantiomers of ketamine and the corresponding synthetic N-trifluoroacetylprolyl amides, it was found that the derivatization reaction proceeds stereoselectively, in poor yield, and with some degree of racemization of the acylating reagent. The results indicate that care must be exercised when prolyl derivatizing reagents are chosen for assaying chiral amines.

Amines↗