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PubMed2002

Induction of xCT gene expression and L-cystine transport activity by diethyl maleate at the inner blood-retinal barrier.

PURPOSE: In this study, the expression and regulation of the L-cystine transporter, system x(-)(c), at the inner blood-retinal barrier (inner BRB) was investigated using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) as an in vitro model. METHODS: For the uptake study, TR-iBRB2 cells were cultured at 33C in the presence or absence of diethyl maleate (DEM), and the uptake rate of [(14)C]L-cystine was measured at 37C. The mRNA levels of system x(-)(c), which consists of xCT and 4F2hc, were determined by quantitative real-time RT-PCR analysis with specific primers. RESULTS: The xCT and 4F2hc mRNAs were expressed in TR-iBRB2 cells. The [(14)C]L-cystine uptake by TR-iBRB2 cells appeared to be mediated through a saturable Na(+)-independent process. The corresponding Michaelis-Menten constant was 9.18 microM. At 100 microM DEM, the xCT mRNA level and L-cystine uptake activity in TR-iBRB2 cells were enhanced in a time-dependent manner. Concomitantly, the glutathione concentration in TR-iBRB2 cells was increased. In contrast, the 4F2hc mRNA level was unchanged up to 24 hours and was induced for more than 24 hours by DEM treatment. Under both normal and DEM treatment conditions, the uptake of [(14)C]L-cystine was strongly inhibited by L-glutamic acid, L-alpha-aminoadipic acid, L-homocysteic acid, and L-quisqualic acid, whereas L-aspartic acid and L-arginine had no effect, which is evidence of the induction of system x(-)(c). CONCLUSIONS: System x(-)(c)-mediated L-cystine uptake appears to be present at the inner BRB. DEM induces L-cystine transport through system x(-)(c) at the inner BRB by enhanced transcription of the xCT gene.

Animals↗

PubMed1976

Infrared identification of maleic acid in pharmaceutical maleate salts.

Difficulties are encountered in the USP melting point identification test for maleic acid extracted from chlorpheniramine maleate. A general procedure is described for the isolation and infrared identification of the maleic acid moiety of pharmaceutical salts from drug substances or dosage forms. This procedure permits the concurrent infrared identification of the amine moiety.

Amines↗

PubMed1957

Control of nausea and vomiting; observations on the use of chlortrimeton (chlorprophenpyridamine maleate) syrup.

Chlor-Trimeton (chlorprophenpyridamine maleate) syrup was effective in preventing and controlling nausea and vomiting in 53 of 57 patients. In doses of one to four teaspoonfuls (2 to 8 mg.), it controlled nausea and vomiting following operative procedures, vomiting due to nonspecific causes, hyperemesis gravidarum, vomiting in altitude and radiation sickness, and vomiting in patients with carcinoma of the colon, acute pancreatitis, and poorly controlled diabetes. No untoward effects from the drug were noted. The syrup was easy to administer, rapidly absorbed, and apparently provided a local anesthetic effect on gastric mucosa.

Anesthesia, Local↗

PubMed1992

Effect of dizocilpine maleate on monoamines and their metabolites in rat brain.

Systemic (ip) injection of dizocilpine maleate (DM, 0.1 and 0.5 mg.kg-1) increased the levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid but did not bring about any noticeable change in the dopamine (DA) level in the striatum and limbic area. DM also increased the levels of norepinephrine in the limbic area and 5-hydroxyindoleacetic acid in the hippocampus. Amphetamine increased DA level and reduced DOPAC level in the striatum and limbic area. The behavioral manifestations revealed that DM predominantly evoked circling behavior and ataxia. The results indicate that the mechanism of the behavioral effect of DM may be different from that of amphetamine.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1992

Effect of dizocilpine maleate on cerebral anoxia and ischemic damage in rodents.

The Protective effects of dizocilpine maleate (DM) against anoxia in mice and ischemic damage in rats of 4-vessel occlusion (4-VO) were studied. DM 0.5 or 1.0 mg.kg-1 ip significantly prolonged the survival time of mice in closed containers. DM 0.5 and 1.0 mg.kg-1 ip 30 min prior to 4-VO obviously accelerated the electroencephalographic recovery, reduced the neuronal loss in the hippocampus, and increased the survival rate after 72-h reperfusion. These effects followed a dose-dependent manner. Our results indicate that selective non-competitive N-methyl-D-aspartate receptor blocker DM protects against anoxic and ischemic cerebral damage.

Animals↗

PubMedDate not supplied

Detoxifying activities in alveolar macrophages of rats treated with acetylcysteine, diethyl maleate and/or aroclor.

Single or sequential treatment of rats with the thiol N-acetyl-L-cysteine (NAC), the glutathione depletor diethyl maleate (DEM) and the enzyme inducer Aroclor 1254 (AR) produced several significant variations on metabolic activities of pulmonary alveolar macrophages (PAM). Specifically, all three compounds elicited an increase in some oxidoreductase activities, including the two dehydrogenases involved in the hexose monophosphate shunt (G6PD and 6PGD) and NADH- or NADPH-dependent diaphorases. Diaphorase activities were especially increased by sequential treatments with AR and DEM or with DEM and NAC. Both NAC and AR also stimulated other detoxifying mechanisms, such as those related to GSH S-transferase activity and to the NADPH-dependent reduction of hexavalent chromium. Therefore, all the monitored parameters were significantly enhanced not only by the enzyme inducer, but also by the thiol, demonstrating its protective role in the biotransformation of mutagenic/carcinogenic compounds.

Acetylcysteine↗

PubMed1987

The effect of glutathione depletion by diamide, diethyl maleate or buthione sulfoximine on the surface structure of mouse L-cells.

Radiosensitizers that act by reducing glutathione levels have been studied by many workers as agents to enhance the killing of hypoxic tumour cells. In this paper we describe a scanning electron microscope (SEM) study of the surface morphology of mouse L-cells after exposure to three of these: diazenedicarboxylic acid bis N,N-dimethylamide (diamide), DL-buthionine-S,R-sulfoximine (BSO) and diethyl maleate (DEM). Diamide at 0.1 to 0.6 mMol/L for 10 min produced large blebs on the cell surface as seen in the SEM. Transmission electron microscope (TEM) images show that these are clear, featureless regions of cytoplasm. BSO treatment for 24 h at 0.5 to 2.0 mMol/L, by contrast, left the surface similar to control cells. DEM at 0.5 mMol/L for 2 h produces small blebs over the cell surface and a reduction in the number of microvilli. A combined 24 h BSO treatment with 2 h of DEM produced large blebs, which were similar in TEM micrographs to those produced by diamide. Thus, although all three sensitizers reduce glutathione levels, they have different effects on cellular morphology and hence such secondary effects may account for the different degrees of radiation sensitization seen with these agents.

Animals↗

PubMed1978

The anti-arrhythmic efficacy of perhexiline maleate, disopyramide and mexiletine in ventricular ectopic activity.

The anti-arrhythmic efficacy of perhexiline maleate, disopyramide and mexiletine has been evaluated in 27 patients with chronic ischaemic heart disease who exhibited frequent ventricular ectopic beats (i.e. greater than or equal to 8/h). Holter tape recordings were made during normal working hours before, during and after the sequential administration of the three drugs. Each drug was administered to each patient for a 2-month period. The drug had to be discontinued in 4 cases because of side-effects. A significant reduction (P less than 0,001) in ectopic beat frequency occurred with all three drugs. No significant difference in anti-arrhythmic potency could be demonstrated between the drugs.

Adult↗

PubMed1985

Differential lipid peroxidative response of rat liver and lung tissues to glutathione depletion induced in vivo by diethyl maleate: effect of the antioxidant flavonoid (+)-cyanidanol-3.

The administration of a single dose of diethyl maleate (DEM) to fed rats elicited a drastic decrease in the content of reduced glutathione (GSH) both in liver and lung tissues after 6 h of treatment. Cellular GSH depletion induced by DEM was accompanied by a marked increase in pulmonary lipid peroxidation which was completely abolished by (+)-cyanidanol-3, without changes in the liver. Superoxide dismutase (SOD) activity remained unchanged in both tissues in this situation. Hepatic and pulmonary GSH depletion induced by a second dose of DEM given 24 h later produced a further increase in lung lipid peroxidation and a diminution of pulmonary SOD activity. In this condition, hepatic lipid peroxidation and SOD activity were not altered. These results indicate that lung and liver tissues exhibit a different lipid peroxidative response to chemically-induced GSH depletion.

Animals↗

PubMed1978

Choleresis associated with metabolism and biliary excretion of diethyl maleate in the rat and dog.

Diethyl maleate (DEM) induces a choleresis in the rat and dog that appears to be canalicular in origin (bile flow and erythritol clearance increase equally) and occurs in the absence of an increase in bile salt excretion. Increased bile flow is probably accounted for by the osmotic activity of DEM compounds excreted into bile. These compounds represent the glutathione conjugate of DEM (DEM-GSH) and its subsequent metabolic products. Conjugation of DEM largely accounts for the depletion of hepatic GSH.

Animals↗

PubMed1981

Effect of timolol maleate on intraocular pressure and pupil cycle time in normal eyes.

One drop of 0.5% timolol maleate instilled into the normal eyes of four subjects produced a marked reduction of intraocular pressure that was maximal at 3 hours but not significant after 12 hours. Instillation of one drop a day for 30 days produced a reliable, maintained reduction of intraocular pressure in the treated eye. The pupil cycle time in both eyes was measured at least twice daily for 1 week before timolol treatment to assess the reproducibility of the test and then twice daily for the 30 days of treatment with timolol. The drug had no significant effect on the pupil cycle time. Measuring the pupil cycle time should afford the ophthalmologist a useful method of assessing the progress of glaucomatous damage to the optic nerve while the patient is undergoing treatment with timolol, an assessment that was not possible when patients were treated with pilocarpine.

Administration, Topical↗

PubMed1997

Alteration of transcriptional and post-transcriptional expression of gamma-glutamylcysteine synthetase by diethyl maleate.

Gamma-glutamylcysteine synthetase (gamma-GCS), also known as glutamate-cysteine ligase (EC 6.3.2.2), is the rate-limiting enzyme in the synthesis of glutathione (GSH). The gene GLCLC encodes the catalytic subunit while GLCLR encodes the regulatory subunit. Although it has been shown that GLCLC can respond to a variety of stresses by increased transcription, it is not known whether a similar response occurs for GLCLR. Nor is it known whether post-transcriptional regulation of either gene product is altered during stress. The present investigation was undertaken to explore transcriptional and post-transcriptional regulation of GLCLC and GLCLR gene products when HepG2 cells were challenged with the radiation sensitizer diethyl maleate (DEM). Expression of steady-state GLCLC and GLCLR mRNA was enhanced 5-20-fold after DEM challenge. Nuclear run-off assays were performed on unstressed and stressed cells to determine whether the increased expression of GLCLC and GLCLR mRNA was due to altered transcriptional activity of these genes. The DEM treatment increased the transcription rates of both genes 2-5-fold. In unstressed HepG2 cells, the half-life of GLCLC mRNA transcripts was approximately 4 h. In contrast, the half-life of GLCLR transcripts was approximately 8 h. In cells treated with DEM, the half-lives of all transcripts were increased, indicating that message stabilization contributed to the increased expression of gene products. Finally, a PEST algorithm has identified a PEST (proline, glutamate, serine, threonine) motif within the catalytic subunit of gamma-GCS, suggesting that this subunit might exhibit conditional proteolytic regulation. These results imply that regulation of the products of the GLCLC and GLCLR genes may be altered at multiple levels during exposure to stress.

Amino Acid Sequence↗

PubMed1998

Distribution of glutathione and technetium-99m-meso-HMPAO in normal and diethyl maleate-treated mouse brain mitochondria.

UNLABELLED: The aim of this study was to explain the contribution of mitochondria to the accumulation of 99mTc-meso-hexamethyl propyleneamine oxime (HMPAO) in the brain, after examinations were performed. METHODS: We studied subcellular distribution of 99mTc-meso-HMPAO and glutathione (GSH) in normal and diethyl maleate (DEM)-administered mice. RESULTS: In normal brain, major radioactivity was found in the mitochondrial (49.0%) and cytosolic fractions (33.0%), while the GSH content was high in the cytosol (63.2%) and mitochondria (30.6%). The radioactivity in mitochondrial, cytosolic, microsomal and nuclear fractions was decreased in a dose-dependent manner by DEM, a GSH depleting agent, to 32.2% (mitochondrial) and 24.7% (cytosolic) of the control by a dose of 550 mg/kg. The GSH content in mitochondrial and cytosolic fractions also decreased in a dose-dependent manner on DEM treatment to 29.3% (mitochondrial) and 30.0% (cytosolic) of the control by 550 mg/kg of DEM. A good correlation was found between the uptake of 99mTc-meso-HMPAO and GSH content in mitochondrial, cytosolic and nuclear fractions, with a correlation coefficient (r) of 0.814, 0.834 and 0.784, respectively. CONCLUSION: Mitochondria are a major subcellular fraction for the uptake of 99mTc-meso-HMPAO by the brain, and GSH in mitochondria contributes to the accumulation of 99mTc-meso-HMPAO.

Animals↗

PubMed1979

Timolol maleate: efficacy and safety.

A randomized, double-masked trial of various concentrations of timolol maleate ophthalmic solution (0.1%, 0.25%, 0.5%, and 1.0%) vs placebo demonstrated that all concentrations of timolol effectively lowered intraocular pressure (IOP). A 0.5% solution of timolol was as effective in reducing IOP as the 1.0% concentration. Blood pressure, visual acuity, and pupillary diameter were not altered significantly by any concentration of timolol tested during this study. There was a dose-dependent decrease in resting pulse rate with increasing concentrations of timolol. No objective signs of drug intolerance were found on external ocular examination, nor were any subjective symptoms elicited on questioning the subjects. Timolol applied topically twice daily in concentrations of 0.1% to 0.5% appeared to be an effective and safe ocular hypotensive agent.

Adult↗

PubMed1979

Lower extremity arterial insufficiency after long-term methysergide maleate therapy. Its evaluation with Doppler ultrasonic velocity detector.

Iatrogenic ergotism is the primary source of ergot intoxication. The patient whose case is reviewed had migraine headaches and received methysergide maleate for 13 years. She had, in July 1977, severe claudication of the lower extremities. Measurements of the peripheral arterial circulation were made using the Doppler ultrasonic velocity detector. The extent of disease and subsequent reversal were documented using arteriographic examination. Initial measurements showed the patient was able to walk for one minute and 34 seconds on a treadmill (2 mph, 10% grade) before stopping because of claudication. Symptoms cleared after drug withdrawal and repeated testing produced no claudication. The calculated index (posterior tibial/arm pressure) increased from a mean of 0.22 to 0.74 during the eight-month period following discontinuance of methysergide therapy with no recurrence of migraine headaches. A review of the literature is also presented.

Constriction, Pathologic↗

PubMed1993

Pharmacokinetics of fluvoxamine maleate after increasing single oral doses in healthy subjects.

The pharmacokinetics of fluvoxamine after single oral administration of 25, 50, and 100 mg fluvoxamine maleate was studied in a three-way cross-over study in 12 healthy male subjects. Fluvoxamine was administered orally in a solution. For dose-proportionality, AUC, and Cmax-dose relationships were evaluated by linear regression. Plasma concentrations increased in a linear dose-dependent manner in the dose range between 25 and 100 mg; t1/2 and Tmax showed no significant differences among treatments. Fluvoxamine was well tolerated.

Administration, Oral↗

PubMed1994

Enalapril maleate affects 2-oxoglutarate metabolism in mitochondria from the rat kidney cortex.

Enalapril maleate (EM) is the salt of N-[(S)-1-ethoxycarbonyl)-3-phenylpropyl]-L-alanyl-L-proline, used therapeutically as an anti-hypertensive agent. The effects of EM on some aspects of the energy metabolism and membrane properties of mitochondria from rat liver and kidney cortex were studied, but only the latter were significantly affected. With 0.8 mM of EM and 2-oxoglutarate as oxidizable substrate for isolated mitochondria from rat kidney cortex, the findings were: (a) inhibition of the respiratory rate in state III (37 per cent) and decrease (45 per cent) in respiratory control ratio (RCR), with only one addition of ADP; (b) reinforcement of the inhibition when a second addition of ADP was made; (c) no significant effect either on the rate of respiration in state IV or on the ADP/O ratio; (d) no effect on the ATPase activity of mitochondria from liver or kidney cortex; (e) inhibition of the transmembrane potential (delta psi) after a second addition of ADP; (f) inhibition of the 2-oxoglutarate dehydrogenase complex. It is suggested that in kidney mitochondria, EM interferes in the gluconeogenesis dependence of at least five substrates: 2-oxoglutarate, glutamine, glutamate, lactate, and pyruvate. Also, EM may inhibit Na+/H+ exchange causing natriuresis.

Animals↗

PubMed1984

Prolonged coronary vasoconstrictor effect of ergonovine maleate.

The duration of the coronary artery vasoconstrictor effect of ergonovine maleate is an important clinical parameter that has not been clearly defined. Since ergonovine is generally administered in incremental, cumulative doses and since this agent may have potentially serious toxic effects related to its vasoconstrictor properties, knowledge of duration of this effect is crucial to its safe and efficacious use. We present clinical evidence of ergonovine-induced coronary artery spasm recurring after pharmacologic relief of a first episode of ergonovine-induced spasm. Recurrent spasm occurred 18 minutes after a cumulative dose of 0.15 mg ergonovine and 14 minutes after intravenous nitroglycerin was given to ameliorate the initial spasm. Therefore, clinical monitoring of patients after ergonovine administration should be designed to identify a possibly prolonged duration of vasoconstrictor effect of the drug. Sequential doses of ergonovine at intervals of ten minutes or less should be recognized as having cumulative effect. The duration of action of pharmacologic agents utilized to alleviate ergonovine-induced coronary artery spasm should exceed the potential duration of action of ergonovine in order to minimize the possibility of late spasm.

Cardiac Catheterization↗