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PubMed2000

Differential acetylcholine release mechanisms in the ischemic and non-ischemic myocardium.

To understand better the pathophysiological roles of the vagal efferent system in ischemic heart diseases, we examined endogenous acetylcholine (ACh) release in the myocardium in vivo. Acute myocardial ischemia was induced in anesthetized cats by a 60-min occlusion of the left anterior descending coronary artery (LAD). We implanted dialysis probes in the left ventricular free wall and measured the dialysate ACh concentration using liquid chromatography. In the ischemic region, the ACh level increased from 0.68+/-0.12 to 12.3+/-3.3 n M (mean+/-S.E., P<0.01) by LAD occlusion. Bilateral vagotomy did not inhibit ischemia-induced ACh release (20.3+/-6.4 n M). In vagotomized animals, inhibition of the N-type Ca(2+)channel by intravenous administration of omega-conotoxin GVIA (10microg/kg) also failed to suppress ACh release (15.9+/-2.0 n M). However, the inhibition of intracellular Ca(2+)mobilization by local administration of 3,4,5-trimethoxybenzoic acid 8-(dietyl amino)-octyl ester (1 m M) suppressed ACh release (4.4+/-0.8 n M, P<0.05 compared with no pharmacological intervention). In the non-ischemic region, the ACh level increased from 1.9+/-0.4 to 6. 0+/-1.0 n M (P<0.05) by LAD occlusion, which was completely abolished by vagotomy. We concluded that ACh release in the ischemic region was mainly attributed to a local release mechanism, whereas that in the non-ischemic region depended on the presence of intact vagal activity. The local release mechanism would depend on intracellular Ca(2+)mobilization but not on N-type Ca(2+)channel opening.

Acetylcholine↗
PubMed2003

Anti-endotoxic effects of syringic acid of Radix Isatidis.

The anti-endotoxic effect of syringic acid (SA) isolated from Radix Isatidis (Banlangen, BLG) was studied. SA was extracted and isolated from BLG and diluted into 1% solution. The content of SA-pretreated endotoxin (ET) was quantitatively determined using Limulus test. The ability of fever induction of ET pretreated with SA was measured using endotoxin-induced fever test in rabbits. The LPS-induced death in mice pretreated with and without SA was compared. Results showed that after pretreatment with SA, 83.16% of ET was destroyed, the ET-induced fever in rabbits relieved markedly and the LPS-induced death rate in mice dropped from 68% to 20%. It was concluded that SA isolated from BLG had anti-endotoxic effects.

Animals↗
PubMed1985

Studies on the mechanism of phorbol ester-induced inhibition of intercellular junctional communication.

Intercellular gap-junctional communication was measured using [14C]citrulline incorporation in co-cultures of argininosuccinate lyase-deficient human fibroblasts and argininosuccinate synthetase-deficient Chinese Hamster V79 cells. As previously shown, in this system junctional communication is completely inhibited by the tumor promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). In the absence of extracellular calcium, TPA inhibition was less pronounced. However, synergism with calcium ionophore A23187 could not be demonstrated. Chlorpromazine, trifluoperazine and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester partially antagonised the effect of TPA. No antagonism was demonstrable between calmidazolium and TPA. Treatment of co-cultures with exogenous phospholipase C or 1-oleoyl-2-acetylglycerol (OAG) resulted in communication inhibition, suggesting that protein kinase C activation is involved in the mechanism of phorbol ester-mediated communication inhibition. However co-cultures which had been made refractory to TPA by prolonged exposure to high concentrations remained sensitive to inhibition by phospholipase C and OAG. These results suggest either that diacylglycerol can produce other effects independent of protein kinase C activation, or that refractoriness to phorbol esters is not simply due to a decrease in the amount of protein kinase C.

Animals↗
PubMed1983

Effect of calcium antagonists on leukotriene D4-induced contractions of the guinea-pig trachea and lung parenchyma.

The directly mediated contractile activity of leukotriene (LT) D4 on isolated guinea-pig trachea and lung parenchyma was dependent upon the presence of calcium in the bathing buffer. Whereas 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8), a calcium antagonist believed to act intracellularly, completely antagonized the LTD4-induced contraction, the calcium channel entry blockers, nifedipine and verapamil, only partially inhibited LTD4 contractile activity; diltiazem was inactive. TMB-8, nifedipine and verapamil were more effective in blocking the contraction of the trachea elicited by KCl-induced membrane depolarization than the contraction induced by LTD4. Of the channel entry blockers, only nifedipine appeared capable of partially relaxing an established LTD4-contracted trachea, whereas TMB-8 almost completely reversed the LTD4 contraction. On the lung parenchyma, the LTD4-induced contraction was suppressed, but not abolished in Ca++-free buffer; this contraction was antagonized by meclofenamic acid, thus suggesting it could be due in part to the indirect thromboxane (Tx) A2-mediated pathway of LT action. In Ca++-free buffer, LTD4 was still capable of generating TxB2, although lower amounts were found when compared to Ca++-containing buffer. Incremental addition of calcium to the parenchyma in Ca++-free buffer containing LTD4 elicited greater than control LTD4-induced contraction and TxB2 generation. Neither the contraction of the parenchyma nor the generation of TxB2 was antagonized by nifedipine; conversely, TMB-8 blocked both completely. Thus, based upon the use of pharmacological antagonists of calcium, these results suggest that LTD4 contractile activity in the respiratory system is dependent upon calcium, with calcium of intracellular origin potentially of significance.

Animals↗
PubMedDate not supplied

Anti-AIDS agents, 1. Isolation and characterization of four new tetragalloylquinic acids as a new class of HIV reverse transcriptase inhibitors from tannic acid.

Four new tetragalloylquinic acids, 3,5-di-O-galloyl-4-O-digalloylquinic acid, 3,4-di-O-galloyl-5-O-digalloylquinic acid, 3-O-digalloyl-4,5-di-O-galloylquinic acid, and 1,3,4,5-tetra-O-galloylquinic acid, were isolated and characterized from a commercial tannic acid as a new class of human immunodeficiency virus (HIV) reverse transcriptase (RT) inhibitor. Compounds 2, 3, and 4 inhibit HIV RT activity 90, 89, and 84% at 100 microM and 73, 70, and 63% at 30 microM, respectively. Compounds 2-5 also inhibit the HIV growth in cells in the range of 61-70% with low cytotoxicity at 25 microM. The HIV cell growth inhibitory effects of these compounds at 25 microM and 6.25 microM (44-57%) are comparable to their effects against the HIV RT at 30 microM and 10 microM, respectively. The inhibitory effect of 3 against DNA polymerases indicates that the selective antiviral action of 3 is determined by more than its action with HIV RT.

Antiviral Agents↗
PubMed1995

The effects of calcium antagonists on anthrone skin tumor promotion and promoter-related effects in SENCAR mice.

The present study investigated a possible role for Ca2+ in skin tumor promotion by anthrones. This was accomplished by testing the effects of two Ca2+ antagonists, verapamil and 3,4,5-trimethoxybenzoic acid 8-(diethylamino) octyl ester (TMB-8), on tumor promotion and promoter-related effects induced by the anthrone chrysarobin in SENCAR mice. Verapamil and TMB-8 both effectively inhibited epidermal ornithine decarboxylase (ODC) induction by a single application of chrysarobin. Both Ca2+ antagonists inhibited anthrone-induced skin edema and epidermal hyperplasia. Additionally, both verapamil and TMB-8 slightly inhibited (20-21% at the highest doses) tumor promotion with chrysarobin. Although the inhibition by both Ca2+ antagonists was not statistically significant (P > 0.05) in either case, the fact that both compounds produced a similar inhibition suggests that this effect may be biologically relevant. Collectively, the data suggest a possible role for Ca2+ in the process of skin tumor promotion by anthrones.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2006

Simulated digestion of Vitis vinifera seed powder: polyphenolic content and antioxidant properties.

There is increasing evidence that reactive oxygen species arising from several enzymatic reactions are mediators of inflammatory events. Plant preparations have the potential for scavenging such reactive oxygen species. Flavans and procyanidins are bioavailable and stable during the process of cooking. This study used conditions that mimicked digestion of Vitis vinifera seed powder in the stomach (acidic preparation) and small intestine (neutral preparation). The flavonoids of these two preparations were released during simulated digestion and were determined with HPLC analysis. Biochemical model reactions relevant for the formation of reactive oxygen species in vivo at inflammatory sites were used to determine the antioxidant properties of the two preparations. The inhibition of the indicator reaction for the formation of reactive oxygen species represents a potential mechanism of the physiological activity of the corresponding preparation. The results of this work show clearly that the polyphenols released during the simulated digestion of the two preparations have good scavenging potential against superoxide radicals, hydroxyl radicals, and singlet oxygen. They protect low-density lipoprotein against copper-induced oxidation due to the copper-chelating properties and their chain-breaking abilities in lipid peroxidation.

Antioxidants↗
PubMed2004

Characterization of the 3-O-methylgallate dioxygenase gene and evidence of multiple 3-O-methylgallate catabolic pathways in Sphingomonas paucimobilis SYK-6.

Sphingomonas paucimobilis SYK-6 is able to grow on various lignin-derived biaryls as the sole source of carbon and energy. These compounds are degraded to vanillate and syringate by the unique and specific enzymes in this strain. Vanillate and syringate are converted to protocatechuate (PCA) and 3-O-methylgallate (3MGA), respectively, by the tetrahydrofolate-dependent O-demethylases. Previous studies have suggested that these compounds are further degraded via the PCA 4,5-cleavage pathway. However, our subsequent analysis of the ligB insertion mutant, which encodes the beta subunit of PCA 4,5-dioxygenase, suggested that at least one alternative route is involved in 3MGA degradation. In the present study, we isolated the desZ gene, which confers 3MGA degradation activity on Escherichia coli. The deduced amino acid sequence of desZ showed ca. 20 to 43% identity with the type II extradiol dioxygenases. Gas chromatography-mass spectrometry analysis suggested that DesZ catalyzes the 3,4-cleavage of 3MGA. Disruption of both desZ and ligB in SYK-6 resulted in loss of the dioxygen-dependent 3MGA transformation activity, but the resulting mutant retained the ability to grow on syringate. We found that the cell extract of the desZ ligB double mutant was able to convert 3MGA to gallate when tetrahydrofolate was added to the reaction mixture, and the cell extract of this mutant degraded gallate to the same degree as the wild type did. All these results suggest that syringate is degraded through multiple 3MGA degradation pathways in which ligAB, desZ, 3MGA O-demethylase, and gallate dioxygenase are participants.

Biodegradation, Environmental↗
PubMed1992

Modulation by intracellular calcium pool of arginine vasopressin-induced cellular cyclic AMP production in rat renal papillary collecting tubule cells in culture.

The present study was undertaken to determine whether endoplasmic reticulum is involved in the cellular action of arginine vasopressin (AVP) in rat renal papillary collecting tubule cells in culture, using three dissimilar agents. 1 x 10(-7) M AVP increased cytosolic free Ca++ concentration ([Ca++]i) from 93.2 to 188.6 nM (P < .01). Exposure to 1 x 10(-4) M 3, 4, 5-trimethoxybenzoic acid, 8-(diethylamino) octylester hydrochloride (TMB-8), which inhibits intracellular Ca++ mobilization and blocks the function of endoplasmic reticulum, attenuated the [Ca++]i response to AVP. A significant increase in [Ca++]i in response to 1 x 10(-7) M AVP was obtained with Ca(++)-free medium containing 1 x 10(-4) M ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid (EGTA) (52.3 to 98.3 nM). However, when cells were preincubated with Ca(++)-free medium containing a mixture of 1 x 10(-4) M EGTA and 1 x 10(-4) M TMB-8, the 1 x 10(-7) M AVP-mobilized [Ca++]i was completely abolished. In the presence of 5 x 10(-4) M 3-isobutyl-1-methylxanthine, AVP increased cellular cyclic AMP (cAMP) production in a dose-dependent manner. Such an AVP-induced cAMP production was significantly reduced in cells exposed to Ca(++)-free medium containing 1 x 10(-4) M EGTA. After exposure to Ca(++)-free medium containing a mixture of 1 x 10(-4) M EGTA and 1 x 10(-4) M TMB-8, the cAMP response to AVP was markedly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[The effect of a decrease in the mobilization of Ca+ and its chemo-controlled intake into the cytoplasm on the modulation of cholinoreceptor neuronal plasticity in Helix lucorum snails by 15-hydroxyeicosatetraenoic acid].

The effects of extracellular solution without Ca2+ and inhibitors of Ca2+ mobilization dependent of Ca2+ (tetracaine) and inositol-1,4,5-trisphosphate (TMB-8) on the modulation of cholinoreceptor (ChR) plasticity of identified Helix lucorum RPa3 and LPa3 neurons by 15(S)-hydroxy-(5Z,8Z,11Z,13E)-eicosatetraenoic acid (15-HETE) were investigated. Using the double-electrode voltage-clamp technique, the inward current, induced by local ionophoretic acetylcholine application (ACh-current), was recorded. ChR plasticity was evaluated by extinction of ACh-current developed in a process of rhythmic ACh applications on the soma with an interval 60-240 s. Tetracaine and TMB-8 disturbed long-latent modulatory effect of 15-HETE and did not influence short-latent one. Extraction of Ca2+ from extracellular solution did not affect the modulatory effect of 15-HETE. It was concluded that one of the molecular mechanisms of ChR plasticity deepening due 15-HETE (in long-latent phase) induces potentiation of Ca(2+)- and inositol-1,4,5-trisphosphate-dependent Ca2+ mobilization evoked by 5-lipoxygenase eicosanoids.

Acetylcholine↗
PubMed1976

Contact dermatitis from antioxidants.

In a search for contact sensitivity to antioxidants we patch tested consecutive patients referred with eczematous dermatitis. Six cases of allergic contact sensitivity to nordihydroguairetic acid (NDGA) were observed. Three had been sensitized by one brand of cream containing 0.1% NDGA, in three patients the source of sensitization could not be traced. In four patients we found positive patch tests to butylated hydroxyanisole and/or to butylated hydroxytoluene. In two cases the positive patch tests were relevant, since both patients remained asymptomatic when antioxidants were avoided in food. They both had acute flares of vesicular eczema on the fingers after oral administration of small amounts. Gallate esters and Vitamin E (d,l-alpha-tocopherol) each gave one unexplained positive patch test. The present data suggest that further search for hidden sensitizers in topical medicaments and cosmetics is warranted. A declaration of all ingredients in industrial products should be placed on the label.

Adolescent↗
PubMed1986

Effects of calcium antagonist TMB-8 on active Na and Cl transport in rabbit ileum.

The effects of 3,4,5-trimethoxybenzoate 8-(N,N-diethylamino)octyl ester (TMB-8), an agent that traps calcium within intracellular stores, were studied on active electrolyte transport in rabbit ileum under basal conditions and after altering transport by increasing the intracellular cAMP content or by exposure to two agonists that act by altering intracellular Ca2+ (carbachol and serotonin). TMB-8 decreased the ileal short-circuit current and increased active Na and Cl absorption by increasing the mucosal-to-serosal Na and Cl fluxes. These effects were reversed by increasing the bathing solution Ca2+ to 4 mM, a concentration that itself did not alter basal ileal transport. The maximum glucose- and amino acid (alanine)-induced increase in Na absorption in the ileum was not affected by TMB-8. The effects on basal transport of TMB-8 were not associated with a change in 45Ca2+ entry across the ileal serosal surface. TMB-8 did not alter cAMP-induced secretion, as judged by its lack of effect on the increase in short-circuit current caused by 8-bromo-cAMP (10(-4) M). TMB-8 totally prevented the transport effects of carbachol but did not inhibit the effects of serotonin. These data suggest a role for intracellular Ca2+ in regulation of basal ileal Na and Cl transport but not in cAMP-induced secretion. There appear to be several pools of intracellular Ca2+ involved in neurohumoral effects on active electrolyte transport.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2003

Antioxidant protection of low density lipoprotein by procyanidins: structure/activity relationships.

The antioxidant activity of catechins and oligomeric procyanidins against low density lipoproteins peroxidation was studied by means of three distinct methods: cis-parinaric acid fluorescence decay, conjugated-dienes detection, and oxygen consumption. A relationship between the radical trapping efficiency of procyanidins and their structure was investigated. The results indicated that: (i) interflavan linkage type (C4[bond]C6 or C4[bond]C8) exerts a significant effect upon radical-trapping antioxidant activity of procyanidins. It is suggested that the conformation adopted by each procyanidin in aqueous solution influence their hydrophilic character, hence affecting their interaction with the peroxyl radicals present in aqueous phase and those in LDL particle (lipidic nature); (ii) antioxidant activity increase with the degree of polymerization for the compounds with (-)-epicatechin (epi) as structural unit (epi, dimer B2 (epi-epi) and trimer C1 (epi-epi-epi)); (iii) galloylation increases antioxidant activity of procyanidins, specially in the case of B2-3"-O-gallate dimer, which revealed the maximal trapping efficiency.

Biflavonoids↗
PubMed1996

Allosteric regulation of the binding of [3H]acetylcholine to m2 muscarinic receptors.

Muscarinic receptors of the m2 subtype expressed in Chinese hamster ovary cells were labeled with [methyl-3H]acetylcholine([3H]ACh), and the rate of dissociation in the presence and absence of several compounds known to exert allosteric effects on labeled antagonist binding was observed. At 25 degrees C, [3H]ACh bound to the receptors with a Kd of 1.2 nM and dissociated with a half-time of 1.6 min. This binding was sensitive to appropriate concentrations of guanine nucleotide and the muscarinic antagonist N-methylscopolamine (NMS). Gallamine, tetrahydroaminoacridine, physostigmine, obidoxime, and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester (TMB-8) all inhibited the binding of [3H]ACh and all slowed the rate of dissociation of [3H]ACh in a concentration-dependent manner. However, the nature of some of the allosteric effects differed from previous studies that used other labeled ligands. In particular, TMB-8, which is very effective in slowing the dissociation of the antagonist [3H]NMS, had much weaker effects on the dissociation of [3H]ACh. Furthermore, TMB-8 was able to partially reverse the stronger effects of gallamine on the dissociation of [3H]ACh, consistent with the possibility that TMB-8 and gallamine share a common site on the receptor. In summary, the binding of ACh to muscarinic receptors is subject to allosteric regulation, and assays using [3H]ACh may be especially useful in the evaluation of potential allosteric regulators of muscarinic systems.

Acetylcholine↗
PubMed1994

Thiopurine methyltransferase activity in a French population: h.p.l.c. assay conditions and effects of drugs and inhibitors.

1. Thiopurine methyltransferase (TPMT) is a cytosolic enzyme involved in the catabolism of thiopurine drugs, which are used to treat cancer patients and organ transplant recipients. Because TPMT activity is polymorphic and under genetic control, large interindividual variations in the immunosuppressive activity and toxicity of these drugs may, at least in part, be inherited. 2. We have developed a specific h.p.l.c. method for measuring 6-methyl mercaptopurine formed from 6-mercaptopurine (6-MP) in red blood cell lysates during the TPMT assay procedure. In blinded assays of 55 samples from adult blood donors, the results of the h.p.l.c. method correlated with those of the radiochemical reference method (r = 0.83, P < 0.001). 3. Using this h.p.l.c. assay, we tested the effect of known inhibitors of TPMT activity (syringic acid, p-anisic acid and tropolone) in vitro and showed that they were highly inhibitory. We also found that drugs often administered concomitantly with 6-MP (prednisone, prednisolone, 6-methylprednisolone, cyclophosphamide, methotrexate, and trimethoprim-sulphamethoxazole) had little or no effect on TPMT activity in vitro. 4. In a group of 300 French individuals, TMPT activity was highly variable, ranging from 4.7 to 35.3 nmol h-1 ml-1 of packed red blood cells (nmol h-1 ml-1 PRBC) with a mean value of 19.3 +/- 4.9. TMPT activity was not influenced by sex. 5. This sensitive and reproducible h.p.l.c. assay for TPMT activity in red blood cells may prove useful for prospective clinical studies designed to optimise dosage regimens of thiopurine drugs (detection limit for 6-methyl mercaptopurine is 5 ng ml-1, intra- and inter-assay variations are 6.8 and 8.2%, respectively).

Adult↗
PubMed2003

[Study on the pharmacokinetics and bioavailability of syringic acid in rabbits].

OBJECTIVE: To study the pharmacokinetics and bioavailability of syringic acid(SA) in rabbits by HPLC. METHOD: After the rabbits were injected SA injection via ear vein and peritoneal cavity, blood was collected also via ear vein at different time-point. Then the concentration of SA in blood was determined by HPLC and the concentration-time curve was mapped to simulate a compartment model. So the pharmacokinetic parameters were calculated out. Several days after this injection, the drug was administered to the rabbits via i.p. and using the same method, another concentration-time curve was obtained. By comparing the AUC of the two curves, bioavailability was obtained. RESULTS: The concentration-time curve of SA in rabbits after i.v. fitted in a two-compartment open model and the absolute bioavailability was 86.27%. CONCLUSION: The results were valuable for the clinical application of new anti-endotoxic drug from Radix Isatidis.

Animals↗
PubMed2003

Changes in the activity of the alternative oxidase in Orobanche seeds during conditioning and their possible physiological function.

The appearance of the activity of the cyanide insensitive, alternative oxidase (AOX), pathway of oxygen uptake was followed in seeds of Orobanche aegyptiaca during conditioning. The pathway becomes operative during conditioning, up to day three as determined by inhibition of oxygen uptake of the seeds by propyl gallate. At the same time an increasing percentage of oxygen uptake is insensitive to cyanide and an increased oxygen uptake, responsive to propyl gallate, is induced by brief salicylic acid treatment of seeds. By day six of conditioning, these responses decrease and the AOX pathway could not be detected in germinating seeds, after treatment with a germination stimulant. These results were confirmed by following the reaction of extracts of fractions enriched with mitochondria from the conditioned seeds, using a specific antibody against AOX. Treatment of the seeds with inhibitors of AOX during conditioning significantly inhibited their subsequent germination. Addition of hydrogen peroxide after 4 and 7 days of conditioning resulted in reduced germination. In addition treatment of seed with propyl or octyl gallate during conditioning reduced the infection of tomato plants by Orobanche seeds and the development of tubercles of the parasite on the host roots. These results together indicate that the operation of AOX during conditioning has a significant function on the subsequent germination behaviour and pathogenicity of the root parasite. Some potential practical applications of these findings are discussed.

Cyanides↗
PubMed2002

Peroxynitrite scavenging activity of herb extracts.

Peroxynitrite (ONOO(-)) is a cytotoxicant with strong oxidizing properties toward various cellular constituents, including sulphydryls, lipids, amino acids and nucleotides and can cause cell death, lipid peroxidation, carcinogenesis and aging. The aim of this study was to characterize ONOO(-) scavenging constituents from herbs. Twenty-eight herbs were screened for their ONOO(-) scavenging activities with the use of a fluorometric method. The potency of scavenging activity following the addition of authentic ONOO(-) was in the following order: witch hazel bark > rosemary > jasmine tea > sage > slippery elm > black walnut leaf > Queen Anne's lace > Linden flower. The extracts exhibited dose-dependent ONOO(-) scavenging activities. We found that witch hazel (Hamamelis virginiana L.) bark showed the strongest effect for scavenging ONOO(-) of the 28 herbs. Hamamelitannin, the major active component of witch hazel bark, was shown to have a strong ability to scavenge ONOO(-). It is suggested that hamamelitannin might be developed as an effective peroxynitrite scavenger for the prevention of ONOO(-) involved diseases.

Antioxidants↗