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PubMed1996

Effects of 8-(N-N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) on skinned myocardial fibres of the rat: reversible inhibition of calcium release from the sarcoplasmic reticulum.

The effects of 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-3), which is reported to inhibit the release of intracellularly stored Ca2+ in skeletal and smooth muscles, were examined in ventricular myocardia of the adult rat. In skinned papillary muscle fibres with functional sarcoplasmic reticulum (SR) preserved, application of 100 or 300 microM TMB-8 during the Ca2+ loading period had no significant effect on the peak tension of subsequent caffeine-induced contraction, but when applied during exposure to caffeine, concentration-dependent reduction of the peak tension was observed. At 1000 microM, TMB-8 reduced the peak tension of caffeine-induced contraction when applied either during Ca2+ loading or during exposure to caffeine. TMB-8 had no substantial influence on the Ca(2+)-tension of skinned fibres without functional SR. In isolated papillary muscle preparations, TMB-8 prolonged the action potential duration and decreased the maximum rate of rise of potential, leading to abolition of contraction at 100 microM. In conclusion, TMB-8 may be a useful pharmacological tool for inhibiting Ca2+ release from SR, but only in skinned myocardial preparations.

Action Potentials↗
PubMed1995

A comparison of the effects of TMB-8 and nifedipine on pressor responses to alpha 1- and alpha 2-adrenoceptor agonists in pithed rats.

TMB-8 has been characterized as an inhibitor of the release of Ca2+ from intracellular pools. We have studied the modification of the pressor responses to selective alpha 1-adrenoceptor agonists (methoxamine and phenylephrine), and to selective alpha 2-adrenoceptor agonists (B-HT 920 and B-HT 933) in pithed rats, produced by TMB-8. We have compared this modification with that produced by the calcium antagonist nifedipine. Nifedipine (100 micrograms/kg, 300 micrograms/kg, and 1000 micrograms/kg) inhibited in a dose-dependent manner the pressor responses to the alpha 1- and alpha 2-adrenoceptor agonists, the dose-response curves to the alpha 2-adrenoceptor agonists being shifted further to the right. TMB-8 at a dose of 3000 micrograms/kg did not modify the pressor effects of the alpha 1-adrenoceptor agonists, and neither did it reinforce the inhibition of such responses produced by nifedipine. By contrast, TMB-8 pretreatment (0.03 micrograms/kg, 0.3 micrograms/kg, 3 micrograms/kg, 30 micrograms/kg, 300 micrograms/kg and 3000 micrograms/kg) inhibited the responses to both alpha 2-adrenoceptor agonists, the inhibition being more pronounced with B-HT 920. A similar effect was obtained with 0.03 micrograms/kg TMB-8 and 0.3 microgram/kg TMB-8, particularly in the case of B-HT 920. It was stronger with higher doses, but similar for all doses over 3 micrograms/kg. The inhibition of the pressor responses mediated by the stimulation of alpha 2-adrenoceptors by TMB-8 was less in rats treated with the Ca2+ entry promoter BAY K 8644 (300 micrograms/kg), and could also be reduced by the continuous infusion of CaCl2 (0.25 microgram/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-1 Receptor Agonists↗
PubMed1991

Structural organization of male-specific visual neurons in calliphorid optic lobes.

The superiority of male flies over female flies in locating and intercepting small rapidly moving targets has been ascribed to differences in their visual systems. In males, this sexual dimorphism is externally expressed by an area of high visual acuity called the acute zone. Selective cobalt uptake reveals 12 types of male-specific visual interneurons in the male lobula, the axons of which terminate in neuropil supplying premotor descending neurons to neck and flight motor circuits. The dendritic fields of the individual male-specific neurons can be extrapolated out into visual space to demonstrate that each is assigned a discrete area of the visual panorama. The dendritic fields of 10 of the 12 male-specific neurons subtend areas of the retina associated with the male acute zone. The functional significance of male-specific neurons is discussed with respect to their putative receptive field and a model circuit for target location by male flies.

Animals↗
PubMed1975

Gomori-positive elementary granules in inner and outer layer of the infundibulum.

With the gallocyanine technique (Wittkowski, Bock and Franken, 1970) Gomori-positive substances of the infundibulum can be stained for light- and electron-microscopic examination. In various mammalian species, the size of Gomori-positive elementary granules in the outer layer is markedly different from that in the inner layer of the infundibulum. In general, the granules of the outer layer have less then half the diameter of those of the inner layer. In birds and fish, however, only small differences were found between the granules of both layers. The significance of the results is discussed.

Animals↗
PubMed1989

The differential effect of calcium antagonists on the positive inotropic effects induced by calcium and monensin in cardiac preparations of rats and guinea-pigs.

It was the aim of the present study to gain more insight into the role of extracellular calcium and of calcium from intracellular sources in the development of contractile force in the mammalian heart. In rat Langendorff hearts the effect of nifedipine, verapamil, diltiazem, bepridil and lidoflazine as well as of the intracellularly acting calcium antagonists ryanodine and TMB-8 on the increase of the left ventricular pressure induced by calcium and the sodium ionophore monensin, respectively, was studied. In rat and guinea-pig papillary muscles the influence of nifedipine, ryanodine and lidoflazine on the effect of monensin on the force of contraction was evaluated. Calcium and monensin concentration-dependently increased the left ventricular pressure in rat Langendorff hearts. The calcium-induced effect was characterized by a sharp initial rise of the left ventricular pressure which stabilized at a lower level while monensin elicited a gradual rise of the left ventricular pressure. Nifedipine, verapamil and diltiazem, applied at the EC50 and the EC80 for the reduction of the left ventricular pressure under control conditions, shifted the concentration-response curves for calcium and monensin into the right. Ryanodine, TMB-8, lidoflazine and bepridil, applied at the EC50, displaced the concentration-response curves for calcium and monensin to the right but reduced the maximal increase of the left ventricular pressure. At the EC80, these drugs almost completely abolished the positive inotropic effects elicited by calcium and monensin, respectively. In rat papillary muscles monensin did not influence the basal force of contraction. A clear positive inotropic effect was only observed in the presence of nifedipine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Reversible histochemical modifications of endoplasmic reticulum following arginine vasopressin stimulation of granular cells of toad bladder.

The endoplasmic reticulum is generally absent from schematic representations of transport phenomena, although it shows a well-organized network in most transport epithelial cells. In order to examine the correlation between this organelle and cellular activity, bladders of Bufo marinus were studied under different experimental conditions and fixed by immersion in glutaraldehyde, followed by OsO4 impregnation for 3 days. Normal granular and mitochondria-rich cells showed a rich cytoplasmic network of canaliculi, well-impregnated by osmium deposits. Following a 2 to 15-min stimulation (serosal bath) with arginine vasopressin, the V2 receptor agonist dD-arginine-vasopressin or cyclic AMP (cAMP), the staining of endoplasmic reticulum in granular cells disappeared. After washing out of the hormone or the agonist, impregnation of the endoplasmic reticulum could be observed once again. Arginine vasopressin did not modify the impregnation of endoplasmic reticulum of either mitochondria-rich or basal cells. Our data indicate a correlation between the reactivity of endoplasmic reticulum to osmium, and a cAMP-dependent effect of arginine vasopressin through its V2 receptors. Incubation of arginine vasopressin through its V2 receptors. Incubation of toad bladders carried out with agents interfering with cellular calcium (calcium ionophores, high or low bath calcium) or with calcium release from the endoplasmic reticulum (TMB-8, thapsigargin) suggested that an early step in the cAMP-dependent effect of arginine vasopressin must involve the release of intracellular calcium from the endoplasmic reticulum. However, calcium ATPases in this organelle do not seem to participate in the hormonal effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

A comparison of four quantitative cytochemical methods directed toward demonstration of DNA.

Populations of nuclei isolated from mouse brain tissue were stained by the following cytochemical methods considered stoichiometric for DNA: (1) the Feulgen reaction; (2) gallocyanin-chromalum after RNase; (3) pH 4.0 methylene blue after RNase; and (4) methyl green used in the presence of 2M magnesium chloride. Replicate preparations to be stained with gallocyanin-chromalum, methylene blue, and methyl green were acetylated prior to staining. All of these groups were examined by high-resolution scanning microspectrophotometry. The results indicated that of the methods examined, the Feulgen reaction, gallocyanin-chromalum used without prior acetylation, and methylene blue used with prior acetylation were the most useful in revealing differences attributable to variability in chromatin organization. The greatest variability in total extinction measurements was observed in acetylated, methylene blue-stained nuclei, while the least variability was observed in nuclei stained with methyl green in the presence of 2 M magnesium chloride. Acetylation produced different effects on dye-binding in different groups. It greatly increased binding in nuclei stained with methylene blue; it reduced binding in the methyl green-2 M magnesium chloride series.

Acetylation↗
PubMed1990

Enhancement by cytochalasin B of ouabain-stimulated catecholamine secretion from cultured bovine adrenal chromaffin cells: possible relation to alteration in Na+/K(+)-pump activity.

1. Catecholamine secretion evoked by ouabain from cultured bovine adrenal chromaffin cells has previously been shown to be markedly enhanced by pretreatment of the cells with cytochalasin B (Morita et al., 1988). To elucidate a possible mechanism of this enhancement, the stimulatory action of ouabain on Ca2+ influx as well as catecholamine secretion was then examined in the cells pretreated with or without cytochalasin B. The effect of cytochalasin B pretreatment on the inhibitory action of ouabain on the Na+/K+ pump was also examined by measuring 86Rb+ uptake into the cells. 2. Pretreatment of the cells with cytochalasin B caused enhancement of ouabain-induced catecholamine secretion, and this enhancement was accompanied by the elevation of ouabain-stimulated 45Ca2+ uptake into the cells. The inhibitory action of ouabain on 86Rb+ uptake was significantly enhanced by pretreatment of the cells with cytochalasin B under the same conditions. 3. These results indicate that the enhancement of ouabain-induced catecholamine secretion caused by cytochalasin B pretreatment may be due to the increase in ouabain-stimulated Ca2+ influx into the cells and, furthermore, suggest the possibility that this increase in Ca2+ influx may be attributed to the potentiation of the inhibitory action of ouabain on the Na+/K+ pump in the adrenal chromaffin cell. Thus, the present study provides an evidence for a possible role of microfilaments as one of the intrinsic factors modulating the plasma membrane functions.

Adrenal Medulla↗
PubMed1994

Use of scanning cytometry in studying bradykinin binding in MRC-5 cells.

Ligand-receptor affinity is classically demonstrated by measuring ligand binding density to a specific site on membrane preparations, and receptor function is studied by measuring calcium flux, cell by cell, using microspectrofluorimetry. In order to study these phenomena in a large cell population, calcium flux was measured in MRC-5 cell line expressing the B2 receptor for bradykinin using an ACAS 570 scanning cytometer. Following incorporation of fluo3/AM, different ligands were studied, singly or in association with bradykinin. This study confirmed that only the B2 receptor is present on the plasma membrane of MRC-5 cells. Bradykinin binding to the B2 receptor was not modified by a B1 agonist (Des-Arg9-bradykinin) or by a B1 antagonist (Des-Arg9-[Leu8]-bradykinin) but was inhibited by a B2 agonist ([Hyp3]-bradykinin) and a B2 antagonist (HOE 140). The source of free calcium was also studied in comparison with ionomycin. The intensity of the calcium peak after binding of bradykinin is independent of the concentration of extracellular calcium. Preincubation with diltiazem or TMB-8 did not modify calcium flux, indicating that transduction of the signal after bradykinin binding in this cell line is independent of voltage-dependent channels and does not require mobilization of intracellular calcium blocked by TMB-8. In conclusion, scanning cytometry can be used to study ligand-receptor binding and to obtain results rapidly from multiple cells. Recording of individual cell variations and kinetics enables identification of active agonists or antagonists and consequently the selection of new compounds.

Bradykinin↗
PubMed1980

Characteristics of N-formyl-methionyl-leucyl-phenylalanine as an inducer of lysosomal enzyme release from human neutrophils.

N-formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated a time- and concentration-dependent release of granule associated beta-glucuronidase and lysozyme but not cytoplasmic lactate dehydrogenase from human neutrophils. Maximum discharge of lysome activity released is insignificant when cells are not preincubated with cytochalasin B prior to being exposed to FMLP (10(-10)-10(-7) M); although 11.2 +/- 1.3 and 12.4 +/- 1.1% of total activity for beta-glucuronidase and lysozyme, respectively, is secreteer, had no effect on FMLP-elicited lysosomal enzyme extrusion. 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8), a purported antagonist of intracidating the role of calcium in the mechanism of lysosomal enzyme release.

Calcium↗
PubMed1989

Possible roles of cAMP and Ca2+ in the regulation of miracidial transformation in Schistosoma mansoni.

The triggering action of physiological saline in the miracidial transformation of Schistosoma mansoni was analyzed using various agents affecting cAMP- and Ca2+-dependent pathways. Potent activators of adenylate cyclase, such as forskolin and serotonin, strongly inhibited the transformation provoked by saline in RPMI-1640. These inhibitory actions were diminished by the combined administration of phosphodiesterase activators such as ammonium salts or imidazole. Furthermore, the exposure of miracidia to ammonium salts or imidazole in dechlorinated tap water "mimicked" the transformation, i.e., the cessation, of swimming and then shedding of epithelial plates. This mimic transformation was also inhibited by serotonin or forskolin. In contrast, treatment of miracidia with Ca2+ antagonists such as TMB-8 (an inhibitor of Ca2+ release), nicardipine (a Ca2+ channel blocker), or W-7 (a calmodulin inhibitor) in tap water produced severe vesiculation on their body surfaces and resulted in death. However, these toxic effects were abolished by a combined administration of these Ca2+ antagonists with saline or NH4Cl, and the transformation was reestablished except with W-7 treatment. W-7 strongly inhibited the triggering action of saline and NH4Cl and the worms swam slowly, whereas W-5, an inactive analogue of W-7, had no inhibitory effect on the transformation. These results suggest that the initiation of micracidial transformation to young sporocysts may be synergistically regulated by cAMP and Ca2+ and that a decrease in cAMP levels and an increase in Ca2+ mobilization may be provoked in worms transformed by saline, ammonium salts, or imidazole.

Animals↗
PubMed1983

Calcium, calmodulin, and the production of prostacyclin by cultured vascular endothelial cells.

The production of prostacyclin (PGI2) by cultured porcine aortic endothelial cells, in response to serum and the calcium ionophore A23187, was inhibited by TMB-8, an antagonist of intracellular calcium mobilization. The calcium-channel blocker methoxyverapamil (D600) inhibited serum-induced PGI2 production in but had little effect on A23187-induced PGI2 production. Calmodulin activity was detected in endothelial-cell lysates and was inhibited by the calmodulin antagonist W7, which also inhibited PGI2 production in response to both agonists. Calcium and calmodulin appear to play an important role in mediating PGI2 production by the vascular endothelium.

Animals↗
PubMed1977

[Determination of antioxidants in foodstuffs (authors' transl)].

We had seen, that after preliminary fat extraction the antioxidants are only incompletly extracted, contray to prior publications of other authors, the antioxidants were extracted from the foodstuffs directly, methylated with diazomethane and estimated by gaschromatography. Propyl, octyl and dodecyl gallate as well as butylated hydroxyanisol and butylated hydroxytoluene were estimated.

Antioxidants↗
PubMed1988

Methyl gallate, methyl-3,4,5-trihydroxybenzoate, is a potent and highly specific inhibitor of herpes simplex virus in vitro. I. Purification and characterization of methyl gallate from Sapium sebiferum.

A potent anti-herpetic compound was identified and purified to homogeneity from the leaves of Sapium sebiferum by plaque reduction assay using herpes simplex virus type 2. The chemical structure of the purified compound was determined by mass spectroscopy and proton and carbon-13 nuclear magnetic resonance as methyl gallate, methyl-3,4,5-trihydroxybenzoate. This is the first demonstration that methyl gallate is a potent anti-herpetic compound in vitro, present in high concentration in the leaves of S. sebiferum, a Chinese folk medicine for shingles.

Antiviral Agents↗
PubMed1988

Methyl gallate, methyl-3,4,5-trihydoxybenzoate, is a potent and highly specific inhibitor of herpes simplex virus in vitro. II. Antiviral activity of methyl gallate and its derivatives.

Methyl gallate (MG), methyl-3,4,5-trihydroxybenzoate, was highly active against herpes viruses as determined by plaque reduction assay. Herpes simplex virus type 2, MS strain, was sensitive to MG at a mean 50% inhibitory concentration (IC50) of 0.224 micrograms/ml in monkey kidney cells. MG was specific for herpes viruses with the relative sensitivity HSV-2 greater than HSV-1 greater than CMV. Two RNA viruses tested were significantly less sensitive to MG. The structural components of MG which modulate the anti-herpetic activity were identified by analysis of chemical analogues. Our structural analyses indicated that three hydroxyl groups were required but were not sufficient for the anti-herpetic action of MG. The presence and chain length of the alkyl ester were also important to the anti-herpetic activity of MG. Methyl gallate may interact with virus proteins and alter the adsorption and penetration of the virion.

Antiviral Agents↗