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PubMed2000

Changes in electrocortical arousal following acute trimethylbenzene administration in rats.

The purpose of this investigation was to compare the neurotoxic potential of trimethylbenzene (TMB) isomers (the solvents) with that of benzene derivatives with a smaller number of methyl groups (toluene). The experiments were performed on WAG/Rij rats with EEG recording electrodes implanted in the fronto-parietal cortex. The solvents, toluene or TMB isomers: 1,3,5-TMB (mesitylene), 1,2,3-TMB (hemimellitene) or 1,2,4-TMB (pseudocumene), were diluted with olive oil and administered intragastrically via gavage at an acute dose of 0.002, 0.008, or 0.032 mol/kg. The electrocortical activity was recorded for 20 min before, and for 60 min after the solvent administration. The electrocorticograms were analysed with respect to the number and duration of the high-voltage spindles (HVS), a form of activity sensitive to the arousal level. In case of each solvent the observed effect--inhibition of the HVS activity--was dose-related. However, the effect produced by TMB isomers was in each case less pronounced than that of toluene. Among TMBs, pseudocumene displayed the least significant effect, and the efficacy of two other TMB isomers was similar.

Analysis of Variance↗
PubMed1986

A characterization of the antinociception produced by intracerebroventricular injection of 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate in mice.

There is evidence that 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) acts as an intracellular Ca++ antagonist producing decreases in free intracellular Ca++ and inhibiting many cellular processes dependent upon intracellular Ca++. Intracerebroventricularly administered TMB-8 was active in the mouse tail-flick test (ED50 = 50 micrograms), and this antinociceptive response was antagonized by naloxone (AD50 = 0.28 mg/kg s.c.), Ca++ (0.2-0.4 mumol i.c.v.) and, to a lesser degree, by ethylene glycol bis (beta-aminoethyl ether)N,N1-tetraacetic acid (0.02 and 0.06 mumol i.c.v.). TMB-8 (i.c.v.) was only marginally active in the p-phenylquinone test. The potency of TMB-8 (i.c.v.) was potentiated 10-fold in morphine-tolerant mice in the tail-flick test (ED50 = 2.5 micrograms). TMB-8 inhibited contraction of stimulated ilea (IC50 = 2.2 microM), an effect which was neither antagonized nor reversed by naloxone (1 microM). TMB-8 did not potentiate morphine, or was it potentiated by morphine, in the stimulated guinea pig ileum. Procaine, but not lidocaine showed dose-dependent activity in the tail-flick and p-phenylquinone tests (ED50 values, 136 and 83 micrograms, respectively, i.c.v.). The antinociception produced by procaine (i.c.v.) in the tail-flick test was antagonized by naloxone (AD50 = 0.4 mg/kg s.c.) Lidocaine (100 micrograms i.c.v.) produced only 30% maximum possible effect in the tail-flick tests, and was inactive in p-phenylquinone tests. Doses of lidocaine greater than 100 micrograms i.c.v. resulted in lethality of greater than 50% of the animals tested. Thus, the activity of TMB-8 resembles that of opiates in that both are antagonized by Ca++ or naloxone in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1987

[Effect of trimebutine on the motility of the normal human small intestines: mechanism of action].

The effects of intravenous trimebutine (TMB) on duodenojejunal motility were investigated in normal subjects in fed and fasted states. The motility was recorded manometrically. In the fasting state TMB 100 mg, 25 min after a spontaneous phase 3 (P3) constantly induced a premature P3. The mean period (means +/- SE) of the migrating motor complex (MMC) cycle decreased from 84 +/- 10.9 to 32.5 +/- 1.0 min. TMB 50 mg, 3 and 25 min after a spontaneous P3 did not significantly modify the periodicity of MMC. TMB 100 mg initiated P3-like activity in post-prandial state. Previous administration of a low dose of naloxone suppressed the stimulating action of TMB. After a TMB injection the motilin plasma level did not vary; a brief increated of PP plasma level was observed. It may be concluded that in the human small intestine TMB included a typical modification of the motility pattern. Opiate receptors might be involved.

Adult↗
PubMed2000

[8-(Diethylamino)octyl-3,4,5-trimethoxybenzoate, HCl], the inhibitor of intracellular calcium mobilization, blocked mitogen-induced T cell proliferation by interfering with the sustained phase of protein kinase C activation.

The physiological role of IP(3)-dependent Ca(2+) release in T cell activation was in question due to the contradictory findings that [8-(Diethylamino)octyl-3,4,5-trimethoxybenzoate, HCl] (TMB-8), an inhibitor of intracellular Ca(2+) mobilization, blocked T cell proliferation, curtailing specifically the level of released Ca(2+) did not affect T cell activation and T cell line lacking IP(3) receptor was defective in IL-2 production in response to TCR/CD3 ligand. In the present study we found that TMB-8 inhibited Concanavalin A (Con A)- but not PMA/Ionomycin-induced T cell proliferation in a reversible and dose-dependent manner. The kinetic study revealed that TMB-8 exerted the inhibitory effect at a very early step of T cell activation. The Ca(2+) ionophore ionomycin augmented instead of overcoming the inhibitory effect of TMB-8, although the same doses of ionomycin alone had no effect on Con A-induced T cell proliferation. PMA the metabolically stable, but not diacylglycerol (DAG) the metabolically labile, activator of protein Kinase C (PKC) completely overcome the antiproliferative effect of TMB-8. A specific DAG lipase inhibitor RHC80267 also overcome the effect of TMB-8. Taken together, these results showed that the process of Ca(2+) release through IP(3) receptor, not the released Ca(2+), is essential for the sustained phase of PKC activation during T cell proliferation.

Animals↗
PubMed1996

Oxidation of 1,2,4,5-tetramethoxybenzene by lignin peroxidase of Phanerochaete chrysosporium.

We have reinvestigated the lignin peroxidase-catalyzed oxidation of 1,2,4,5-tetramethoxybenzene (TMB) by using presteady-state and steady-state kinetic methods. Our presteady-state kinetic results show that the reaction of compound I with TMB obeyed second order kinetics with a rate constant of 1.1 x 10(7) M-1s-1. The reaction of compound II with TMB exhibits a hyperbolic concentration dependence with a Kd of 16 microM and K = 24 s-1. The stoichiometry of TMB oxidation during steady state is two TMB cation radicals formed per H2O2 consumed. These results clearly show that TMB is a good substrate for both compounds I and II of lignin peroxidase.

Anisoles↗
PubMed1994

A stable water-soluble tetramethylbenzidine-2-hydroxypropyl-beta-cyclodextrin inclusion complex and its applications in enzyme assays.

3,3',5,5'-Tetramethylbenzidine (TMB), a hydrophobic and noncarcinogenic chromogen with a high absorption coefficient widely used in solid-phase assays involving labeled horseradish peroxidase was rendered soluble (up to 40 mM) and more stable for at least 2 months at 22-24 degrees C by forming a water-soluble inclusion complex with 2-hydroxypropyl-beta-cyclodextrin (hp-beta-CyD). Cyclic voltammetry and absorbency measurement were employed to characterize the TMB-hp-beta-CyD complex. Well-defined cyclic voltammograms of TMB exhibited two oxidation waves which merged into a single wave with increasing hp-beta-CyD concentrations. Cyclic voltammetry was then used to examine the effect of complexation with hp-beta-CyD on the oxidation potential of TMB and provided evidence of a 1:1 complex between TMB and the cyclodextrin molecule with a formation constant of 1.6 M-1. Enzyme assays for D-glucose, lactate, and glutamate were performed by coupling the TMB-hp-beta-CyD/horseradish peroxidase system to the respective oxidase enzymes with the formation of either a blue (absorption coefficient of 35,800 M-1 cm-1 at 650 nm) or a yellow color (absorption coefficient of 67,300 M-1 cm-1 at 450 nm) as an indication of the metabolite concentration. These assays possessed a sensitivity limit below 10 microM and the results obtained were in excellent agreement with standard enzymatic assays when tested in various food and clinical samples.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1999

Physiologically based modeling of 1,2,4-trimethylbenzene inhalation toxicokinetics.

A physiologically based toxicokinetic model was developed for inhalation exposure of 1,2,4-trimethylbenzene (TMB) in man. The model consists of six compartments for TMB and one compartment for the metabolite 3,4-dimethylhippuric acid (DMHA). Based on previous experimental findings from human exposures to TMB, liver metabolism was divided in two pathways, one of the first order and one of the Michaelis-Menten type. Muscle tissue was split in two compartments to account for working and resting muscle tissues during bicycle exercise. The model was used to investigate how various factors influence potential biomarkers of exposure, i.e., TMB in blood and exhaled air and DMHA in urine. Increasing the work load from rest to moderate exercise (100 W) more than doubled all biomarker levels end of shift. The effect on next morning levels was even more pronounced, illustrated by a fivefold increase in the DMHA excretion rate. Simulations of five daily 8-h exposures suggest that biomarker levels end of shift remain fairly constant whereas the levels prior to shift increase gradually during the week. This suggests that end of shift levels reflect the exposure of the same day whereas levels Friday morning reflect exposure during the entire working week. Simulations with randomly generated exposures show that the variability due to fluctuating exposure is lower next morning than end of shift. End of shift exhalation rate of TMB is more sensitive to fluctuation than TMB in venous blood and DMHA in urine. Biomarker levels for 25 ppm exposure at different sampling times are given.

Administration, Inhalation↗
PubMed1993

Inhibitors of the intracellular Ca2+ release mechanism prevent muscarinic-induced Ca2+ influx in rat sublingual mucous acini.

The effects of inhibitors of the intracellular Ca2+ release mechanism on divalent cation fluxes were examined in acinar cells loaded with the Ca(2+)-sensitive, Mn(2+)-quenchable dye, fura-2. TMB-8 and dantrolene (DTL) dramatically inhibited the carbachol (CCh)-stimulated increase in [Ca2+]i and Mn2+ influx. These agents do not directly inhibit divalent cation entry since addition of TMB-8 or DTL after CCh stimulation did not block Mn2+ influx. TMB-8 did not influence the [Ca2+]i increase or the Mn2+ influx produced by thapsigargin. These results indicate that TMB-8 and DTL do not interfere with divalent cation influx by inhibiting a step distal to depletion of the intracellular Ca2+ pool. TMB-8 and DTL did not significantly influence the muscarinic-stimulated production of inositol trisphosphate (IP3) and inositol tetrakisphosphate (IP4), although TMB-8, but not DTL, did decrease the CCh-stimulated 1,4,5-IP3 levels approximately 55%. The above results directly demonstrate that the filling state of the intracellular Ca2+ store primarily regulates the Ca2+ entry mechanism in sublingual mucous acinar cells.

Animals↗
PubMed1989

Improvement of the tetramethyl benzidine reaction with ammonium molybdate as a stabilizer for light and electron microscopic ligand-HRP neurohistochemistry, immunocytochemistry and double-labelling.

Ammonium heptamolybdate (AHM) was used as a stabilizing agent in the tetramethyl benzidine (TMB) reaction of choleragen subunit B conjugated horseradish peroxidase (CB-HRP) neurohistochemistry (TMB-AHM method). In comparison with Mesulam's TMB method employing sodium nitroprusside as a stabilizing agent (TMB-SNP method), the TMB-AHM procedure offers a similar sensitivity with regard to the visualization of CB-HRP labelled neurons and their extranuclear Golgi-phobic dendrites. However, it is less sensitive for the demonstration of anterogradely transported CB-HRP in axon terminals. At the nearly physiological pH value of the reaction medium (pH 6-8), it demonstrates better preservation of tissue and cell structures in the reacted sections. Under the electron microscope, the specific reaction product can be clearly distinguished and little damage of cellular and subcellular structures occurred. Preliminary application of TMB-AHM method to choleragen subunit B (CB) immunocytochemistry and double labelling technique which paired the neuronal tracing methods of HRP neurohistochemistry and CB immunocytochemistry, was also carried out with small modification.

Animals↗
PubMed2004

Peroxidase-catalyzed co-oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of substituted phenols and their polydisulfides.

The steady-state kinetics of the horseradish peroxidase (HRP)-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) has been studied in the presence of 2-amino-4-nitrophenol (ANP), gallic acid (GA) or 4,4'-dihydroxydiphenylsulfone (DDS) and their polydisulfides poly(ADSNP), poly(DSGA), poly(DSDDS) at 20 degrees C in 10 mM phosphate buffer, pH 6.4, supplemented with 5-10% dimethylformamide. The second-order rate constants for the reactions of ANP, GA, poly(DSGA) and poly(DSDDS) with HRP-Compound I (k2) and Compound II (k3) have been determined at 25 degrees C in 10 mM phosphate buffer, pH 6.0 by stopped-flow spectrophotometry. ANP, GA and their polydisulfides strongly inhibited HRP-catalyzed TMB oxidation. Inhibition constants (Ki) and stoichiometric coefficients of inhibition (f) have been determined for these reactions. The most effective inhibitor was poly(DSGA) (Ki=1.3 microM, f=35.6). The oxidation of substrate pairs by HRP, i.e., TMB-DDS and TMB-poly(DSDDS) at pH 7.2 resulted in a approximately 8- and approximately 12-fold stimulation of TMB oxidation rates, respectively. The mechanisms of the HRP-catalyzed co-oxidation of TMB-phenol pairs are discussed.

Antioxidants↗
PubMedDate not supplied

Behavioral changes following 4-week inhalation exposure to pseudocumene (1,2,4-trimethylbenzene) in the rat.

Pseudocumene (1,2,4-trimethylbenzene, TMB) is a component of several solvent mixtures. During recent studies on rats we investigated the effect of a 4-week (6 h/day, 5 days/week) inhalation exposure to TMB at concentrations of 0, 25, 100, or 250 ppm on radial maze performance, open field activity, passive avoidance, active two-way avoidance, and shock-induced changes in the pain sensitivity reflecting the magnitude of the shock-induced fear response (hot plate test). The tests were performed between days 14 and 54 after the last exposure. The radial maze performance was not disturbed in any dose group. During testing in the open field grooming was significantly increased in rats exposed to 100 ppm TMB. In rats exposed to 100 and 250 ppm TNB, a foot shock applied after stepping off an elevated platform (a safe area) resulted in a significantly smaller increase in the step-down latency (i.e., passive avoidance, on days 3 and 7 after the foot shock) than in sham-exposed animals. Learning of a two-way active avoidance was slightly retarded in rats exposed to 250 ppm of TMB. Results of the hot plate test revealed no differences between groups in the paw sensitivity to heat (54.5 degrees C) before a 2-min intermittent food shock, but in rats exposed to 100 and 250 ppm of TMB the foot shock-induced fear response persisted apparently longer. These results suggest that inhalation exposure to TMB may lead to long-lasting disturbances in CNS functions.

Animals↗
PubMed1997

Degradation of Trimethylbenzene Isomers by an Enrichment Culture under N(inf2)O-Reducing Conditions.

A microbial culture enriched from a diesel fuel-contaminated aquifer was able to grow on 1,3,5-trimethylbenzene (1,3,5-TMB) and 1,2,4-TMB under N(inf2)O-reducing conditions, but it did not degrade 1,2,3-TMB. The oxidation of 1,3,5-TMB to CO(inf2) was coupled to the production of biomass and the reduction of N(inf2)O. N(inf2)O was used to avoid toxic effects caused by NO(inf2)(sup-) accumulation during growth with NO(inf3)(sup-) as the electron acceptor. In addition to 1,3,5-TMB and 1,2,4-TMB, the culture degraded toluene, m-xylene, p-xylene, 3-ethyltoluene, and 4-ethyltoluene.

Journal Article↗
PubMedDate not supplied

A comparison of cerebral hemodynamic parameters between transient monocular blindness patients, transient ischemic attack patients and control subjects.

PURPOSE: To assess whether patients with transient monocular blindness (TMB) and patients with hemispheric transient ischemic attacks (hTIA) differ from each other with respect to cerebral hemodynamic parameters. METHODS: Seventeen TMB patients and 23 hTIA patients with a moderate to severe stenosis or an occlusion of the internal carotid artery (ICA) underwent magnetic resonance (MR) angiography, (1)H MR spectroscopy and transcranial Doppler sonography. Thirty-one control subjects were investigated to obtain reference values for the MR investigations. Quantitative flow was measured in the ICAs, the basilar artery and the middle cerebral arteries (MCA). Metabolic changes in the MCA territory were studied by assessing N-acetyl-aspartate (NAA)/choline ratios and prevalences of lactate. The prevalence of collateral flow was assessed in the circle of Willis and the ophthalmic arteries. The vasomotor reactivity was studied by measuring the CO(2) reactivity of the MCA territories. RESULTS: Quantitative flow in the cerebropetal arteries and the MCAs did not differ between TMB patients and hTIA patients. Also patterns of collateral flow, prevalence of lactate and CO(2) reactivity were similar. The mean ipsilateral NAA/choline ratio was lower in hTIA patients compared with TMB patients (p < 0.01), and was predominantly correlated with symptomatology (p < 0.01), i.e. whether patients had TMB or hTIA, and not with ipsilateral MCA flow (p = 0.2) or ipsilateral CO(2) reactivity (p = 0.7). CONCLUSION: The results of this study indicate that there are no cerebral hemodynamic differences between TMB patients and hTIA patients. It is therefore unlikely that hemodynamic factors account for differences in clinical characteristics between the two patient groups.

Amaurosis Fugax↗
PubMed1999

Effects of acute exposure to aromatic hydrocarbons C 9 on locomotor activity in rats. Trimethylbenzene isomers.

This study was performed to find out whether in acute exposure to trimethylbenzene (TMB) isomers the dose effect relationship is linear or biphasic. In experiments performed on rats, the effect of four solvents was studied: three TMB isomers: 1,3,5-TMB (mesitylene), 1,2,3-TMB (hemimellitene), and 1,2,4-TMB (pseudocumene), and toluene, known for its biphasic activity, was used as a reference compound. The solvents were dissolved in olive oil and administered to rats orally at the doses of 0.008, 0.016, and 0.032 mol/kg. Spontaneous locomotor activity was assessed with the open-field test. Solvent concentrations in peripheral blood were determined parallelly by gas chromatography on separate groups of animals. Statistics employed a two-way analysis of variance (ANOVA) and Tukey's test. The results showed that oral administration of toluene at a dose of 0.008 mol/kg induced biphasic changes in the animal locomotor activity. It was found that TMB at applied doses increased slightly the animal locomotor activity, but the magnitude of changes did not indicate their stimulating effect. Contrary to toluene, no time-effect relationship was observed after administration of trimethylbenzene isomers. The mean blood concentrations of solvents were dose-related. The highest concentrations were observed after toluene administration.

Animals↗
PubMed1987

[Involvement of opiate receptors in the mode of action of trimebutine].

Several studies in dogs, cats, rabbits and humans have suggested that the motility stimulating properties of trimebutine (TMB) are mediated by peripheral opiate receptors. The present work deals with the capacity of TMB and its N-desmethyl metabolite (NDTMB) to displace mu, delta and kappa specific ligands from their receptors using guinea-pig brain membranes and ileal myenteric plexus synaptosomal membrane preparations. The activity of both compounds on the twitch response induced by transmural stimulation on the guinea-pig ileum as well as the mouse and rabbit vas deferens was also investigated. These preparations have been proposed to be specific for the mu, delta and kappa receptor subtypes respectively. TMB (0.2 to 1.8 microM) and NDTMB (0.3 to 6 microM) displayed a good affinity for all receptor subtypes in brain and myenteric plexus preparations. Both compounds also inhibited the twitch response of all three isolated organ preparations. The decreasing order of IC50's of TMB ranged from 0.75 microM in the guinea-pig ileum to 7.1 and 39 microM in the vas deferens of the rabbit and the mouse respectively. These results indicate that TMB and NDTMB possess mu, delta as well as kappa agonist properties without true specificity for one or the other of these subtypes. They also confirm that activation of peripheral mu, delta and kappa opiate receptors mediate the gastrointestinal motility effect of TMB.

Animals↗
PubMed1987

Effects of orally vs. parenterally administrated trimebutine on gastrointestinal and colonic motility in dogs.

The influence of oral administration and intravenous infusion of trimebutine maleate (TMB) and N-desmethyl TMB (NDTMB), its main metabolite, was investigated in conscious dogs equipped with chronically implanted strain-gauges. In fasted dogs, TMB (10 to 20 mg/kg per os) delayed the occurrence of the next activity front on both stomach and duodenum by reinforcing the duration of the intestinal phase II. It also induced the occurrence of an additional migrating phase III. These effects were associated with a colonic stimulation generally followed by an inhibition. Comparatively NDTMB at similar dosages disrupted the antral cyclic phases which were replaced by continuous low amplitude contractions during 5-7 h. The MMC pattern persisted with a significant increase in the duration of phase II, and the colonic motility was inhibited during 4.3 to 6.7 h. Infused intravenously at a dose of 3 mg X kg-1 X h-1, TMB immediately inhibited the gastric cyclic contractions in fasted dogs. As for the oral route, the small bowel exhibited an increase in the duration of phase II frequently associated with the occurrence of an additional phase III. Furthermore an inhibition of the colonic motility was observed only at the end of the infusion and lasted at least 4 h. At similar dosage NDTMB had less pronounced inhibitory effects on gastric activity fronts and in contrast with TMB, the inhibitory effect on the colonic motility was observed as soon as the infusion of NDTMB started. These data demonstrate that orally administered TMB stimulates intestinal motility as previously described for i.v. route but in contrast to parenteral administration also stimulates antral and colonic motility.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1982

Cooxidation of the clinical reagent 3,5,3'5'-tetramethylbenzidine by prostaglandin synthase.

Prostaglandin synthase catalyzes the oxidation of arachidonic acid to prostaglandin H2 via a hydroperoxide intermediate, prostaglandin G2. The prostaglandin synthase system cooxidizes 3,5,3'5'-tetramethylbenzidine (TMB), a derivative of the human carcinogen benzidine, to colored products. This process is arachidonic acid dependent and indomethacin sensitive. The reaction is also supported by hydroperoxides, and, in this case, indomethacin has no effect. This suggests that the cooxidation is mediated by the hydroperoxidase activity of prostaglandin synthase. The products of TMB oxidation by this system are the same as those obtained with lactoperoxidase and H2O2 or with horseradish peroxidase and H202. The initial products of TMB oxidation are the TMB radical cation and a charge-transfer complex composed of TMB and its two-electron (diimine) oxidation product. The TMB radical cation was identified by electron spin resonance spectroscopy. Ascorbic acid reduces the products, regenerating the parent compound.

Benzidines↗
PubMed1993

Effects of nifedipine, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride and atrial natriuretic peptide on endothelin-induced antinatriuresis in dogs.

Nifedipine, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) or atrial natriuretic peptide (ANP) was infused into the renal artery before and during intrarenal arterial infusion of endothelin-1 (ET) in anesthetized dogs. Before ET infusion, nifedipine (0.1 micrograms kg-1 min-1), TMB-8 (75 micrograms kg-1 min-1) or ANP (10 ng kg-1 min-1) increased the urine flow rate, urinary sodium excretion and fractional sodium excretion with little change in renal blood flow or glomerular filtration rate. ET (2 ng kg-1 min-1) reduced the basal renal blood flow, glomerular filtration rate, urine flow rate, urinary sodium excretion and fractional sodium excretion. Both nifedipine and TMB-8 induced natriuresis during ET infusion; but only TMB-8 completely reversed the ET-induced reduction in fractional sodium excretion and partially antagonized the reductions in urine flow rate and urinary sodium excretion. ANP did not induce substantial urinary responses during ET infusion. Neither nifedipine, TMB-8 nor ANP reversed the ET-induced decreases in renal blood flow and glomerular filtration rate. The present study suggests that in the dog kidney 1) the ET-induced antinatriuresis is caused in part by enhancement of tubular sodium reabsorption, 2) the tubular action of ET depends on TMB-8-sensitive calcium movements but not calcium influx through dihydropyridine-sensitive channels and 3) ANP cannot counteract the ET-induced antinatriuresis.

Animals↗