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PubMed2002

In situ characterization of a NO-sensitive peroxidase in the lignifying xylem of Zinnia elegans.

The lignifying xylem from Zinnia elegans stems gives an intense reaction with 3,3',5,5'-tetramethylbenzidine (TMB), a reagent previously reported to be specific for peroxidase/H2O2. However, the staining of lignifying xylem cells with TMB is apparently the result of two independent mechanisms: one, the catalase-sensitive (H2O2-dependent) peroxidase-mediated oxidation of TMB, and the other, the catalase-insensitive oxidation of TMB, probably mediated by xylem oxidases which are specific from lignifying tissues. The catalase-insensitive oxidation of TMB by the Z. elegans xylem was sensitive to sodium nitroprusside (SNP), a nitric oxide (NO)-releasing compound that, when used at 5.0 mM, is capable of sustaining NO concentrations of 6.1 &mgr;M in the aqueous phase. This effect of SNP was totally reversed by 150 &mgr;M 2-phenyl-4,4,5,5-tetramethyl imidazoline-1-oxyl-3-oxide (PTIO), an efficient NO scavenger in biological systems, so the above-mentioned effect must be ascribed to NO, and not to other nitrogen oxides. This response of the catalase-insensitive TMB-oxidase activity of the lignifying Z. elegans xylem was similar to that shown by a basic peroxidase isolated from the intercellular washing fluid, which showed TMB-oxidase activity, and which was also inhibited by 5 mM SNP, the effect of SNP also being reversed by 150 &mgr;M PTIO. These results suggest that peroxidase was the enzyme responsible for the NO-sensitive catalase-insensitive TMB-oxidase activity of the lignifying Z. elegans xylem. Further support for this statement was obtained from competitive inhibitor-dissected histochemistry, which showed that this stain responded to peroxidase-selective competitive inhibitors, such as ferulic acid and ferrocyanide, in a similar way to the Z. elegans basic peroxidase. From these results, we conclude that this NO-sensitive catalase-insensitive oxidation of TMB is apparently performed by the Z. elegans basic peroxidase, and that the regulation of this enzyme by NO may constitute an intrinsically programmed event during the differentiation and death of the xylem.

Journal Article↗
PubMed1991

8-Diethylamino-octyl-3,4,5-trimethoxybenzoate, a calcium store blocker, increases calcium influx, inhibits alpha-1 adrenergic receptor calcium mobilization, and alters iodide transport in FRTL-5 rat thyroid cells.

8-Diethylamino-octyl-3,4,5-trimethoxybenzoate (TMB-8) is known to inhibit mobilization of calcium from intracellular stores but, more recently, other cellular effects have been described. In the present study, the effects of TMB-8 on cytosolic free calcium [Ca2+]i levels in FRTL-5 rat thyroid cells were determined using the fluorescent dye, Indo-1. TMB-8 increased [Ca2+]i in a dose-dependent manner, with a maximum rise from 120 +/- 7 nM to 229 +/- 16 nM (90 +/- 5% increase) at 5 x 10(-4) M. This effect was considerably reduced in Ca2+ free buffer, demonstrating a dependency upon extracellular calcium influx but not upon membrane potential and which did not involve the Na+/Ca2+ exchanger. In Ca2+ free buffer TMB-8, at a dose which did not affect [Ca2+]i, completely prevented norepinephrine (10(-5) M) from mobilizing intracellular Ca2+. To determine whether TMB-8 affected differentiated functions, iodide uptake and efflux studies were performed with 125I. TMB-8 (10(-4) M) inhibited iodide uptake by approximately 40% without affecting efflux. At 10(-3) M TMB-8, efflux was also enhanced. These studies demonstrate that TMB-8 has at least two effects on [Ca2+]i, promoting calcium influx and preventing alpha-1 adrenergic mobilization from intracellular stores. TMB-8 also has multiple effects on 125I transport, both inhibiting influx and increasing efflux. The results emphasize the importance of characterizing the behavior of this compound in any cell system before using it as a biological probe.

Animals↗
PubMed2003

In vitro evaluation of the efficacy of skin barrier creams and protective gloves on percutaneous absorption of industrial solvents.

OBJECTIVES: The aim of the experiments was to evaluate the efficacy of skin barrier creams (SBCs) and protective gloves and its potential for reduction of percutaneous absorption of industrial solvents. METHODS: We assessed percutaneous absorption of ethylene glycol (EG), isopropyl alcohol (IA) and 1,2,4-trimethylbenzene (TMB), using static diffusion cells. These solvents were applied neat (EG, TMB) as well as in 10% and 50% aqueous solution (EG, IA) or in 10% and 50% ethanol-diluted solution (TMB). Furthermore, we tested the percutaneous absorption of IA mixed in one cleaning agent (CA), used in newspaper printing shops to clean the rollers of printing machines. Additionally, the penetration behaviour of 10% and 50% solutions of EG, IA and TMB was tested. The experiments were carried out on untreated and on SBC-treated excised human skin from one donor, and on protective gloves. Saline was used as receptor fluid for EG and IA, and neat ethanol for TMB. RESULTS: The penetration of 50% EG, IA and TMB solutions through SBC-treated skin was higher than in untreated skin (factor 3.9 for EG, 0.32 for IA and 0.06 for TMB). The penetration of IA in the IA-CA mixture was five-times higher through untreated skin as for the single compound in 10% aqueous solution. In skin, treated with SBC, we found a 17-fold penetration enhancement of IA in the IA-CA mixture. No appreciable penetration of EG and IA was observed through nitrile rubber gloves. CONCLUSIONS: Our in vitro experiments could not demonstrate an efficacy of SBC to protect skin penetration for the tested solvents. The percutaneous absorption of all solvents in 50% solution was increased through skin treated with SBCs. Furthermore, SBCs enhance the penetration rates of solvents from complex mixtures compared with the single solvents. The tested gloves showed sufficient protection for the hydrophilic solvents, but not for TMB.

2-Propanol↗
PubMed1984

Calcium dependence of the stimulatory action of hypertonicity on renal medullary prostaglandin synthesis.

Previous studies have shown that hypertonic mannitol or NaCl increases the release of [3H]arachidonate and immunoreactive prostaglandin E in inner medullary slices incubated in Ca2+-free media containing EGTA. By contrast, the stimulation of these parameters by ionophore A23187 and by arginine-vasopressin are abolished in Ca2+-free media plus EGTA. In the present study, the effects of Ca2+ deprivation and the intracellular Ca2+ antagonist TMB-8 [8-N,N-diethylamino)octyl-3,4,5 -trimethoxybenzoate-HCl) were further examined to assess the Ca2+ dependence of the actions of different stimuli of prostaglandin E synthesis in rat renal inner medulla. Ca2+-free media without EGTA abolished increases in [3H]arachidonate and immunoreactive prostaglandin E release induced by ionophore A23187, but not those induced by arginine-vasopressin, suggesting that different pools of Ca2+ subserve expression of the actions of these two stimuli. At low concentrations, TMB-8 (10-25 microM) inhibited increases in [3H]arachidonate and immunoreactive prostaglandin E release induced by arginine-vasopressin, but did not influence effects of Ca2+ plus ionophore A23187 or hypertonicity on these parameters. At higher concentrations (100-500 microM), TMB-8 suppressed effects of ionophore A23187, hyperosmolar NaCl and mannitol on immunoreactive prostaglandin E and [3H]arachidonate release from slices. The effects of a sub-optimal inhibitory concentration of TMB-8 on ionophore A23187 actions were overcome by increasing Ca2+ in the media from 1.5 to 5 mM. Ca2+ deprivation, or concentrations of EGTA or TMB-8, that were effective in suppressing increases in immunoreactive prostaglandin E induced by ionophore A23187, arginine-vasopressin or hypertonicity, did not modify increases in immunoreactive prostaglandin E induced by exogenous arachidonate. Moreover, in microsomal fractions of inner medulla, TMB-8 suppressed Ca2+-dependent increases in phospholipase A2 and C activities, an effect which was competitive with Ca2+. Thus, Ca2+ deprivation and TMB-8 act at a step in the immunoreactive prostaglandin E synthetic pathway proximal to cyclooxygenase activity, and probably at the level of Ca2+-dependent acyl hydrolase activity. The results with TMB-8 indicate that an intracellular pool of Ca2+ is involved in expression of the actions of hypertonicity to increase [3H]arachidonate release and immunoreactive prostaglandin E in inner medulla.

Animals↗
PubMed2003

Optimization of media for detection of hydrogen peroxide production by Lactobacillus species.

A healthy vaginal ecosystem has been shown to be protective against the acquisition of human immunodeficiency virus and gonorrhea, and women who are colonized with H(2)O(2)-producing lactobacilli are more likely to maintain a normal vaginal flora than women with lactobacilli that do not produce H(2)O(2). The purpose of this study was to formulate a testing medium that better supports the growth and detection of H(2)O(2) by a broader range of lactobacilli than a published, widely used agar formulation (TMB). The new medium (TMB-Plus) consists of brucella agar base, 3,3',5,5'-tetramethylbenzidine, horseradish peroxidase, starch, vitamin K, hemin, magnesium sulfate, manganese sulfate, and horse serum. To validate the new formula, 256 vaginal isolates and ATCC strains were inoculated onto TMB-Plus and, for comparison, onto TMB. Growth was enhanced for 69% of the isolates on TMB-Plus, and 48% had enhanced color production. The percentage of H(2)O(2)-positive isolates increased from 71% on TMB to 79% on TMB-Plus. Formulations using Rogosa or MRS agar base in combination with peroxidase and a chromogen did not support the growth of all of the strains of Lactobacillus, and fewer H(2)O(2)-producing strains were detected on these formulations than on TMB-Plus. This new medium better supports the growth of a wider range of Lactobacillus strains isolated from the vagina and enhances the color production of H(2)O(2)-producing strains.

Agar↗
PubMed1999

Characterization of interaction of 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester with Torpedo californica nicotinic acetylcholine receptor and 5-hydroxytryptamine3 receptor.

The widely used calcium channel antagonist 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester (TMB-8) has been identified as a noncompetitive antagonist (NCA) and open-channel blocker of both muscle- and neuronal-type nicotinic acetylcholine receptors (AChRs). To further examine the interaction of TMB-8 with the AChR, the compound was tested as a competitor for the binding of two NCAs of the Torpedo californica AChR, phencyclidine and 3-trifluoromethyl-3-(m[125I]iodophenyl)diazirine, for which the binding to the AChR has been pharmacologically well characterized and a channel binding loci has been established. TMB-8 fully inhibited specific photoincorporation of 3-trifluoromethyl-3-(m[125I]iodophenyl)diazirine into the resting AChR channel (IC50 = 3.1 microM) and inhibited high-affinity [3H]phencyclidine binding to the desensitized AChR (IC50 = 2.4 microM). We conclude that TMB-8 is a potent NCA of the nicotinic AChR, interacting with the resting, open-channel, and desensitized channel conformations. TMB-8 was next tested as an inhibitor of the structurally homologous 5-hydroxytryptamine (5-HT)3 receptor (5-HT3R). Using 5-HT3R containing Sf21 cell membranes, TMB-8 completely inhibited specific binding of the radiolabeled 5-HT3R antagonist [3H]GR65630 (Ki = 2.5 microM). Furthermore, TMB-8 antagonized 5-HT-evoked currents of both mouse and human 5-HT3Rs expressed in Xenopus laevis oocytes, and additional analysis was consistent with a competitive antagonistic mechanism of action. These results, taken together, indicate that TMB-8 antagonizes the function of the AChR and 5-HT3R by different mechanisms. Given the sequence similarity and emerging evidence of structural homology in the channels of these two receptors, these results underscore the existence of subtle yet important structural differences in each channel.

Amino Acid Sequence↗
PubMed1999

Time management behaviors as potential explanatory factors in dental academic achievement.

DAT scores and predental GPAs have made the greatest but an imperfect contribution to the reliable estimation of dental students' academic success. One variable unaddressed yet having potential in accounting for unexplained variability in dental school performance is time management behaviors (TMB), a multidimensional attribute that is critical to success in a dental curriculum. Research has indicated a relationship of TMB dimensions (Setting Goals and Priorities, Mechanics of Time Management, Preference for Organization) with undergraduate academic achievement. The purposes of this study were: 1) to ascertain the levels of TMB dimensions reflected in predental students; 2) to validate in predental students the relationship of TMB dimensions and undergraduate academic achievement; and 3) to explore the relationship of TMB dimensions of predental students as explanatory variables of their early academic achievement in the dental curriculum. All individuals who were applicants interviewed for the 1997 entering D.D.S. class and the majority of members of the 1996 entering D.D.S. class participated in this study (n = 192). Each completed the TMB scale. High levels of TMB across dimensions were observed in predental and dental students. Unlike prior research, results showed virtually no relationship of TMB dimensions with undergraduate GPA of these subjects. Though a small relationship was found between dimensions and first-year dental GPAs, no dimension explained a significant amount of variance in any of these dental GPAs beyond that of undergraduate science GPA.

Achievement↗
PubMed2003

[8-(N,N-diethylamino)-n-octyl-3,4,5-trimethoxybenzoate inhibited the reduction of cerebral blood flow evoked by 5-HT and KCl in rats].

AIM: To investigate the impact of 8-(N,N-diethylamino)-n-octyl-3,4,5-trimethoxybenzoate (TMB-8) on the change of cerebral blood flow(CBF) induced by 5-HT or KCl in rats. METHODS: The CBF in rats was measured by a Laser-Doppler flowmeter. The cranial window field was superfused with artificial cerebral spinal fluid containing TMB-8, 5-HT or KCl. RESULTS: 12.5, 25 and 50 mumol.L-1 TMB-8 showed no significant effect on rest CBF in rats. 12.5, 25 and 50 mumol.L-1 TMB-8 apparently inhibited the decline of CBF evoked by 1 or 2 mumol.L-1 5-HT. When persistent reduction of CBF were evoked by 1 mumol.L-1 5-HT, TMB-8 markedly increased the CBF in a concentration-dependent manner. The reduction of CBF induced by 20 or 40 mmol.L-1 KCl was also suppressed by 12.5, 25 and 50 mumol.L-1 TMB-8. While persistent reduction of CBF was evoked by 20 mmol.L-1 KCl. TMB-8 markedly increased the CBF in a concentration-dependent manner. CONCLUSION: These results indicate that TMB-8 is effective in preventing and treating the reduction of CBF induced by 5-HT or KCl, and improved the supply of blood in rat brain during ischemia.

Animals↗
PubMed1985

Action of trimebutine in cat and rabbit colon: evidence of an opioid-like effect.

Because trimebutine (TMB) is a drug that modulates colonic motility, we have attempted to determine the modifications of electrical activity underlying the motor effects of this drug. Experiments have been carried out on cat colon in vivo and on rabbit proximal colon in vivo and in vitro. The action of TMB (0.5-2 mg/kg in vivo; 10(-7) M-10(-6) M in vitro) consisted of an initiation or of an increase of spike potential activity that was unaffected by atropine (0.1 mg/kg for the cat, 2-3 mg/kg in vivo and 10(-6) M in vitro for the rabbit) and by hexamethonium (1.5 mg/kg for the cat and 2 mg/kg in vivo or 10(-6) M in vitro for the rabbit). In the cat under atropine, spike activity became cyclical, i.e., bursts of spikes were interrupted by periods of electrical silence. In the cat, TMB decreased the amplitude of excitatory junction potentials. Under atropine, TMB induced rhythmic variations in the amplitude of inhibitory junction potentials for 30 to 40 min. In the rabbit under TMB, excitatory junction potentials were enhanced whereas inhibitory junction potential amplitude was decreased. All the effects of TMB on spontaneous activity as well as on junction potentials are very similar to those observed in a previous work with morphine and enkephalins. The effects of TMB, unaffected by guanethidine, were antagonized by naloxone (2 mg/kg in vivo, 10(-6) M in vitro). These results suggest that opiate receptors, presumably located on intramural neurons, are involved in the effects of TMB.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1994

[Determination of dimethylbenzoic acid isomers in urine by gas chromatography].

Trimethylobenzene (TMB) is a main ingredient of many organic solvents used in industry. In Farbasol (Polish trade name of the solvent) TMB occurs as a mixture of three isomers: pseudocumene (1, 2, 4-TMB) 30%; mesitylene (1, 3, 5-TMB) 15%; hemimellitene (1,2,3-TMB) 5%. As it is known in human organism, TMB is metabolized mainly to dimethylbenzoic (DMBA) and dimethylhippuric (DMHA) acids, and some authors suggest, that the acids excreted in urine can be biological indicators of exposure to TMB. This study was aimed at developing the method of determination of DMBA isomers in urine. Biological material was hydrolyzed with sodium hydroxide and next extracted with diethyl ether. DMBA concentration in urine was determined by gas chromatography using a variant of quantitative analysis with internal standard (5-methyl-2-isopropylphenol, thymol). Analytical parameters of the developed method of determination of DMBA isomers in urine such as linearity, precision, reproducibility, stability (192 days, when urine samples stored at-18 degrees C), detectability limit (400 micrograms/dm3) have been fully compatible with the requirements of biological monitoring. In order to confirm the presence of DMBA isomers in urine, four volunteers were exposed (8 hours) to Farbasol in toxicological chamber. The TMB concentration in the air, determined by means of gas chromatograph (HP 5890), amounted to 100 mg/m3 (MAC value in Poland). In urine samples collected 2,3-; 2,4-; 2,5-; 2,6-; 3,4-; 3,5-dimethylbenzoic acids were identified by means of GC/MSD.(ABSTRACT TRUNCATED AT 250 WORDS)

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

8-(Diethylamino)-octyl-3,4,5-trimethoxybenzoate inhibits cromakalim-induced 86Rb efflux from the rat aorta.

The effects of 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8) on cromakalim-induced 86Rb efflux and vasorelaxation in the rat aorta have been assessed. TMB-8 inhibited cromakalim (10 microM)-induced 86Rb efflux with an IC50 of 0.50 +/- 0.15 microM (n = 4; IC50 for glyburide 0.17 +/- 0.05 microM, n = 4), but it produced minimal antagonism of the cromakalim-induced vasorelaxation (rings precontracted with 30 mM KCl-PSS) at TMB-8 concentrations < or = 3 microM. TMB-8 at 10 microM produced significant inhibition of the cromakalim-induced vasodilation. Inhibition of cromakalim-induced 86Rb efflux produced by TMB-8 was little affected by raising the KCl concentration to 30 mM (inhibition by 0.5 microM TMB-8: 62.9 +/- 6.9 and 52.5 +/- 10.9% in 4.6 and 30 mM KCl, respectively; n = 4 for both). Similarly, the inhibitory effects of glyburide on the cromakalim-induced 86Rb efflux were minimally affected by this maneuver. TMB-8 was approximately equipotent against the increase in 86Rb efflux generated by either 1 or 10 microM cromakalim (IC50: 0.73 +/- 0.11 and 0.65 +/- 0.33 microM, respectively; n = 4 of both). In contrast, the glyburide IC50 was reduced approximately 10-fold by reducing the concentration of cromakalim used from 10 to 1 microM (IC50: 182.5 +/- 4.8 and 19.5 +/- 2.6 nM, respectively; n = 4 for both). We hypothesize that TMB-8 inhibits the potassium channel that is opened by cromakalim.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Toxicokinetics of inhaled trimethylbenzenes in man.

The objective of this study was to determine the uptake and disposition of inhaled trimethylbenzenes (TMBs) in man. The toxicokinetics were studied in 10 male, healthy volunteers exposed to TMB vapor in an exposure chamber for 2 hr during a work load of 50 W. The subjects were exposed on four occasions to 25 ppm of 1,2,4-TMB, 1,2,3-TMB, and 1,3,5-TMB, and to 2 ppm of 1,2,4-TMB. The TMB isomers were analyzed in blood, urine, and exhaled air by gas chromatography. The relative respiratory uptake was in the range 56-64%. The elimination of TMBs was moderate compared to other aromatic solvents, with a total blood clearance of 0.6-1.0 liter hr(-1) kg(-1). Large volumes of distribution (30-39 liters/kg) and long terminal half-lives of the TMBs in blood (78-120 hr) imply extensive accumulation in adipose tissue. Exhalation during and postexposure accounted for 20-37% of the absorbed amount, whereas the urinary excretion of unchanged TMBs was low (< or = 0.002%). The kinetics of 1,2,4-TMB seemed linear up to 25 ppm. In addition, the occurrence of symptoms of acute effects was studied by means of a questionnaire. The subjects rated the degree of irritation and central nervous system symptoms on a 100-mm visual analog scale. No discomfort was reported at these exposure conditions.

Administration, Inhalation↗
PubMed2001

Behavioral effects following subacute inhalation exposure to m-xylene or trimethylbenzene in the rat: a comparative study.

Trimethylbenzene (TMB), like xylene (dimethylbenzene), is a significant constituent of some industrial solvent mixtures. In earlier studies, we found that in the rat a subacute low-level inhalation exposure to some of the TMB isomers may result in behavioral alterations detectable weeks after the exposure [Neurotoxicol Teratol 19;1997:327; Int J Occup Med Environ Health 11;1998:319]. The purpose of the present study was to compare m-xylene (XYL) and each of the TMB isomers: 1,2,3-TMB (hemimellitene - HM), 1,2,4-TMB (pseudocumene - PS), and 1,3,5-TMB (mesitylene - MES) with respect to the ability for inducing behavioral effects in the rat. The rats (10-11 animals per group) were exposed repeatedly for 4 weeks (6 h per day, 5 days per week) to XYL (XYL group), HM (HM group), PS (PS group) or MES (MES group) at 100 ppm, or sham exposed (C group) in 1.3 cu/m dynamic inhalation chambers. Starting 2 weeks after exposure the following forms of rat's behavior were assessed: radial maze performance, spontaneous activity in an open field, learning and retention of passive and active (two-way) avoidance response, and heat-induced paw licking before and after a 2 min footshock (a test for assessment of the stress response). None of the solvent-exposed groups differed considerably from the control one with respect to the radial maze performance. Compared to control rats, the rats of the XYL, PS and MES groups, but not those of HM group, showed a significantly higher spontaneous locomotor activity in the open field, an impaired passive avoidance learning and significantly longer paw-lick latencies 24 h after footshock. Acquisition, but not retention, of the two-way active avoidance response was significantly impaired in all solvent-exposed groups. The XYL group did not differ significantly from PS, MES or HM group in any of the behavioral parameters. The above results show that a short-term exposure to any of the TMB isomers or m-xylene at concentration as low as 100 ppm may induce persistent behavioral alterations in the rat.

Administration, Inhalation↗
PubMed1997

Mechanism of the oxidation of 3,5,3',5'-tetramethylbenzidine by myeloperoxidase determined by transient- and steady-state kinetics.

Earlier investigations of the oxidation of 3,5,3',5'-tetramethylbenzidine (TMB) using horseradish peroxidase and prostaglandin H-synthase have shown the formation of a cation free radical of TMB in equilibrium with a charge-transfer complex, consistent with either a two- or a one-electron initial oxidation. In this work, we exploited the distinct spectroscopic properties of myeloperoxidase and its oxidized intermediates, compounds I and II, to establish two successive one-electron oxidations of TMB. By employing stopped-flow techniques under transient-state and steady-state conditions, we also determined the rate constants for the elementary steps of the myeloperoxidase-catalyzed oxidation of TMB at pH 5.4 and 20 degrees C. The second-order rate constant for compound I formation from the reaction of native enzyme with H2O2 is 2.6 x 10(7) M-1 s-1. Compound I undergoes a one-electron reduction to compound II in the presence of TMB, and the rate constant for this reaction was determined to be (3.6 +/- 0.1) x 10(6) M-1 s-1. The spectral scans show that compound II accumulates in the steady state. The rate constant for compound II reduction to native enzyme by TMB obtained under steady-state conditions is (9.4 +/- 0.6) x 10(5) M-1 s-1. The results are applied to a new, more accurate assay for myeloperoxidase based upon the formation of the charge-transfer complex between TMB and its diimine final product.

Animals↗
PubMed2003

Activation of peroxidase-catalyzed oxidation of aromatic amines with 2-aminothiazole and melamine.

The peroxidase-catalyzed oxidation of 3,3;,5,5;-tetramethylbenzidine (TMB), ortho-phenylenediamine (PDA), and 5-aminosalicylic acid (5-ASA) is significantly accelerated in the presence of 2-aminothiazole (AT) and melamine (MA), and an increase in their concentrations is associated with a parallel increase in the k(cat) and K(m) values for TMB and PDA. The activation of the peroxidase-catalyzed oxidation of TMB and PDA is quantitatively characterized by a coefficient (degree) alpha (M(-1)) which significantly depends on pH in the range 6.2-6.4, 6.4-7.4, and 6.0-7.4 for the TMB-AT, TMB-MA, and PDA-MA pairs, respectively. An increase in the coefficient alpha with increase in pH confirms nucleophilicity of activation of the peroxidase-catalyzed oxidation of the aromatic amines in the presence of AT and MA. Under optimal conditions the coefficients alpha for the TMB-AT, PDA-AT, TMB-MA, and PDA-MA pairs vary in the limits of (1.90-3.53)*10(3) M(-1).

Amines↗
PubMed2001

Concurrent and construct validity of scores on the Timed Movement Battery.

BACKGROUND AND PURPOSE: The Timed Movement Battery (TMB) is a new assessment tool designed to measure mobility in elderly individuals. "Mobility" was defined as a person's ability to maneuver his or her body independently in order to accomplish everyday tasks. The purpose of this study was to assess the concurrent and construct validity of scores obtained with the TMB as a measure of mobility in a group of elderly individuals who reported moderate or no difficulty in performing either basic or instrumental activities of daily living (BADL or IADL). SUBJECTS: Thirty community-dwelling elderly people, with a mean age of 77.5 years (SD=7.0, range=65-92), participated in this study. METHODS: Subjects responded to 2 questionnaires regarding their activities of daily living (ADL) (ie, Barthel Index and an 18-item ADL/IADL scale) and completed 3 assessments of mobility (ie, Berg Balance Scale, Timed "Up & Go" Test, and the TMB). Subjects were asked to perform the items on the TMB at a "self-selected" speed (their normal speed) and at a "maximum-movement" speed (as quickly as they could safely perform the items). Subjects' scores on the TMB were cross-correlated with data for 4 criterion tests (ie, Berg Balance Scale, Timed "Up & Go" Test, Barthel Index, and the 18-item ADL/IADL scale) using Spearman rank correlations and Pearson product moment correlations. RESULTS: Composite scores of the TMB performed at self-selected speeds correlated highly with data for the criterion tests and differentiated between those subjects reporting difficulty with ADL and those reporting no difficulty. CONCLUSION AND DISCUSSION: These results support the validity of scores obtained with the TMB as a measure of mobility in this sample of elderly individuals with moderate or no reported difficulty with ADL.

Activities of Daily Living↗
PubMed1975

Studies on the mechanism of action of a new Ca-2+ antagonist, 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride in smooth and skeletal muscles.

1. The rabbit aortic strip, guinea-pig ileum and rabbit skeletal muscle sarcoplasmic reticulum preparations were used to determine at which sites and in what manner 8-(N,N-diethylamino)-octyl 3,4,5,-trimethoxybenzoate (TMB-8) interferes with Ca2+ availability in smooth and skeletal muscles. 2. TMB-8 (50 muM) significantly inhibited equivalent responses of the rabbit aortic strip to KCl and noradrenaline. 3. TMB-8 (65 muM) produced no significant alteration in the extracellular space of the guinea-pig ileum as measured with [3H]-sorbitol. 4. The resting cellular Ca2+ influx as well as the resting 45Ca2+ efflux in the guinea-pig ileum preparation were significantly inhibited by TMB-8 (65 muM). 5. TMB-8 (5 muM and 50 muM) had no significant effect on the uptake of 45Ca2+ by the sarcoplasmic reticulum preparation of skeletal muscle; however, TMB-8 (5 muM) did significantly inhibit the caffeine (20 mM)-induced release of 45Ca2+ from this preparation. 6. It is concluded that TMB-8 reduces Ca2+ availability in smooth and skeletal muscles by stabilizing Ca2+ binding to cellular Ca2+ stores and thereby inhibits the release of this Ca2+ by contractile stimuli.

Animals↗
PubMedDate not supplied

Liquid/air partition coefficients of the trimethylbenzenes.

Liquid/air partition coefficients (lambda) of the three isomers of trimethylbenzene (1,2,3-,1,2,4-, and 1,3,5-TMB) were determined in vitro using automated head space gas chromatography. The liquids used were water (physiological saline), fresh human blood, and olive oil. The lambda water/air were 1.23 (95% confidence interval 1.11-1.35) for 1,3,5-TMB, 1.61 (1.47-1.75) for 1,2,4-TMB, and 2.73 (2.54-2.92) for 1,2,3-TMB. Corresponding lambda blood/air were 43.0 (40.8-45.2), 59.1 (56.9-61.3), and 66.5 (63.7-69.3). As expected, the TMBs have a high affinity for olive oil, the lambda oil/air being 9,880 (9,620-10,140), 10,200 (9,900-10,400), and 10,900 (10,500-11,300), respectively. It is notable that all partition coefficients increase in the order 1,3,5-TMB < 1,2,4-TMB < 1,2,3-TMB.

Air↗