Biomedical subjects

T Dine

Publications and source records attributed to T Dine.

At least 19 recordsLinked to original sources

PubMed1997

Metabolism of clozapine by human neutrophils: evidence for a specific oxidation of clozapine by the myeloperoxidase system with inhibition of enzymatic chlorination cycle.

The use of clozapine, an unique antipsychotic drug, raises the real problem of drug-induced polymorphonuclear neutrophil cytotoxicity. Clozapine prescription has been restricted due to a 1-2% incidence of drug-induced agranulocytosis. The exact mechanism of this adverse effect is not yet known. The myeloperoxidase-hydrogen peroxide system could play a key role in the initiation of agranulocytosis. Therefore, we have investigated the clozapine effects on hydrogen peroxide and hypochlorous acid, evaluated the peroxidase-mediated metabolism of clozapine by mass spectrometry analysis because myeloperoxidase uses hydrogen peroxide and chloride producing hypochlorous acid in its chlorination cycle, and thus could oxidise clozapine in its peroxidation cycle. First, evidence for inhibition of hypochlorous acid production and scavenging of hydrogen peroxide by clozapine were demonstrated in vitro, in different cell-free and cellular systems. Results are consistent with an inhibition of the myeloperoxidase chlorination cycle when clozapine is oxidised in the peroxidation cycle. Secondly, ion-spray mass spectrometry analysis allowed us to confirm clozapine oxidation by the myeloperoxidase system. Actually, clozapine N-oxide with a m/z at 343 was formed. It could be the final step of the metabolisation of clozapine via two successive univalent oxidations mediated by peroxidase. We suggest that generation of a free cation radical, CLZ(o+), was the initial step. CLZ(o+) is a very reactive species and may play an important role in the onset of agranulocytosis either by direct toxicity or via an immunological mechanism. However, this assumption does not exclude the possible role of other metabolic ways involving, in particular, N-desmethylclozapine.

Antipsychotic Agents↗

PubMed1997

In vitro interaction between dirithromycin or its metabolite, erythromycylamine, and oxidative polymorphonuclear metabolism.

The direct stimulation by neutrophil-infectious bacteria induces an increase in the production of reactive oxygen species which is an important host defense mechanism. Antibiotics that enter rapidly and are concentrated in neutrophils, can stimulate or damage this function. In this study, an in vitro evaluation has been made of the macrolide, dirithromycin, and its active metabolite, erythromycylamine, on the superoxide anion generation by neutrophils in three systems of stimulation: the oligopeptide fMLP, an analogue of bacterial chemotactic factors; the phorbol ester PMA, a direct activator of protein kinase C; and a bacteria strain, Staphylococcus aureus. It has been demonstrated that dirithromycin, at therapeutic plasma concentrations, and its active metabolite have a significant pro-oxidant effect on the two systems: fMLP and bacteria. This effect is greater for dirithromycin than that for erythromycylamine. At higher non-therapeutic concentrations, these substances decrease superoxide generation in the three systems. The effects of these two agents seem to be the result of an intracellular mechanism resulting in the intervention of the oxidative metabolism of neutrophils since no effect was found in the cell-free systems. Therefore, this in vitro study suggests that at therapeutic concentrations, dirithromycin and erythromycylamine could benefit therapy by stimulation of the oxidative metabolism of neutrophils.

Anti-Bacterial Agents↗

PubMed1997

Antioxidant activities of polyphenolic extracts from flowers, in vitro callus and cell suspension cultures of Crataegus monogyna.

Numerous plants synthesize among their secondary metabolites phenolic compounds which possess antioxidant effects. The aim of the present work was to assay the antioxidant activities of phenolics from Crataegus monogyna Jacq. flowers and in vitro tissue culture (calli and cell suspensions) extracts. In the case of tissue culture extracts, the phenolic production is studied at three different stages of one subculture period (initial growth period, increasing and maximal phenolic synthesis phases). Attention was paid to the main categories: flavonoids and proanthocyanidins, and to the principal individual components. Total phenolic amounts decrease in the order: fresh flowers > cell suspension cultures > callus cultures. The antioxidant activities of these different extracts against H2O2 and HOCl, have been determined in vitro. All the extracts are efficient and the scavenging capacity is clearly related to the total phenol content. The scavenging effects of the cell suspension extracts are similar to those of the flowers. Among individual compounds, the flavanol-type derivatives, specially the proanthocyanidin B2, are more efficient. Thus, in vitro plant tissues could be an interesting source of bioactive molecules.

Anthocyanins↗

PubMed1996

Effects of calcium antagonist diltiazem on leukocyte elastase and on reactive oxygen species production in human neutrophils.

During inflammatory disorders, some proteases and very reactive oxygen metabolites are produced by activated phagocytic cells. These proteases and oxidants are involved in many diseases like tissue injury or atherosclerosis. It was shown in vitro that diltiazem, a calcium channel blocker, had antielastase and antioxidant properties. This drug inhibited the release of elastase by neutrophils in a dose dependent manner when these cells were stimulated by phorbol-myristate-acetate (PMA) or by formyl-methionyl-leucylphenylalanine (fMLP) with an IC50 of 144.5 microM, and 132.8 microM, respectively. Towards the oxidants, the 50% inhibitory concentrations (IC50) of diltiazem are 422 microM, 138 microM and 165 microM for superoxide anion, hypochlorous acid and hydroxyl radical production by PMA stimulated human neutrophils, respectively. In the case of fMLP stimulated human neutrophils, the IC50 for superoxide anion is 78 microM. When human neutrophils were stimulated by dioctanoylglycerol (DiC8) or by calcium ionophore (Ca.I), the IC50 for superoxide anion were 175.5 microM and 186 microM, respectively. When human neutrophils were stimulated by opsonized zymosan (OZ), diltiazem did not show an inhibition of superoxide production in a dose dependent manner. This drug did not act by scavenging elastase or oxidants as demonstrated by cell free models. A mechanism of elastase and oxygen metabolites inhibition by diltiazem has been considered specially toward the mobilization of cytosolic calcium and an inhibition of protein kinase C cannot be excluded. The results suggest that diltiazem might contribute to attenuate the development and the progression of atheroma where oxidants and elastase have been implicated.

Diltiazem↗

PubMed1996

Neuroleptic monitoring: relation between antipsychotic efficiency and radioreceptor assay of serum haloperidol.

OBJECTIVE: We report preliminary results from use of a radioreceptor assay (RRA) to measure serum haloperidol levels and their relation to clinical response and adverse effects in 19 psychotic patients with positive symptoms treated with haloperidol. METHODS: Blood samples were taken on Days 7, 14 and 21. Clinical evaluation was based on the PANSS, and UKU scales. The D2 antidopaminergic RRA was used to measure haloperidol serum levels. RESULTS: Our results show a correlation between psychosis with positive symptoms assessed by positive scores in the PANSS and the serum drug level measured by RRA concentrations. The observed relationship made it possible to establish a therapeutic serum range of haloperidol equivalents 15-30 ng/ml-1. This range contained no "non-responders". Analysis of the correlation between each item on the positive subscale of the PANSS and the RRA concentration suggested that there was no specific symptom of psychosis closely related to RRA concentration during the first 15 days of treatment. In the third week, however, certain specific symptoms were closely connected to the RRA concentration. CONCLUSION: From these results, it can be concluded that antipsychotic activity can be related to blockade of serum D2 dopamine receptors. In future would be desirable to monitor neuroleptic treatment in this way. The study also showed that the antipsychotic treatment did not correct any specific component of the psychosis during the first stage of the treatment but that it did so at later times.

Adult↗

PubMed1996

Stability and compatibility studies of zorubicin in intravenous fluids and PVC infusion bags.

The stability of zorubicin (ZOR) in admixtures for continuous intravenous infusion was studied. ZOR was reconstituted and diluted to 600 micrograms ml-1 for simulated infusion and to 250 and 1000 micrograms ml-1 for storage in poly(vinyl chloride) (PVC) bags containing 5% dextrose injection or 0.9% sodium chloride injection (0.9% NaCl). Bags were then stored at refrigerated temperature (4 degrees C) and in the dark for 24 h. ZOR concentrations in each admixture were tested by stability-indicating high-performance liquid chromatographic (HPLC) assay with ultraviolet detection. No substantial loss of ZOR was observed during simulated infusions (n = 4) using PVC infusion bags and administration sets over a 1 h infusion. The drug stored at 4 degrees C in the dark in PVC bags showed that it is highly unstable at 250 micrograms ml-1 in 0.9% NaCl injection and in 5% dextrose injection. On the other hand, under the same storage conditions, at 1000 micrograms ml-1, ZOR is more stable in 0.9% NaCl injection (6 h) than in 5% dextrose (4 h). The reported superior stability of the 1000 micrograms ml-1 in 0.9% NaCl can be explained, at least in part, by the difference in pH. Changes in pH, particularly a decrease, seem to affect adversely the stability of ZOR. In fact, ZOR is rapidly converted into daunorubicin, the dominant degradation product, which is more cardiotoxic than the parent drug. Therefore, several precautions must be observed when the commercial product (Rubidazone) is prepared and reconstituted in i.v. fluids and containers.

Antibiotics, Antineoplastic↗

PubMed1996

Effect of the protein kinase C inhibitor GF 109 203X on elastase release and respiratory burst of human neutrophils.

1. The effects of bisindolylmaleimide GF 109 203X, reported to be a potent and highly selective inhibitor of protein kinase C (PKC), have been investigated on some human neutrophil functions. 2. GF 109 203X prevented O.2- production by NADPH-oxidase whatever the stimulus used for polymorphonuclear neutrophil (PMN) activation: directs PKC activators like phorbol myristate acetate (PMA) and dioctanoylglycerol, calcium ionophore (A23187), or receptor agonists like fMet-Leu-Phe (fMLP) and opsonized zymosan. 3. The effect of GF 109 203X was also examined on elastase exocytosis by neutrophils. PMA-mediated release was prevented by GF 109 203X. However, GF 109 203X had no effect on exocytosis induced by A23187 and the effect of this compound on the fMLP response changed according to its concentration. 4. These data suggest that PKC might be essential for stimulus-mediated O.2- production and also that PKC plays only a minor role in elastase secretion as compared to the role of the cytosolic calcium level.

Calcimycin↗

PubMed1996

Effect of dialysis on exogenous dopamine in haemodialysed critically ill patients.

A sensitive and specific high performance liquid chromatographic method (HPLC) was developed for measuring dopamine (DA) in human plasma samples. Dihydroxybenzylamine (DHBA) was employed as an internal standard. Following solvent extraction and separation on a C18 ion-pairing reversed phase column, the drug was detected by a fluorescence detector with excitation and emission wavelengths of 233 nm and 345 nm, respectively. This method was employed to evaluate dopamine dialysability in seven haemodialysed patients under continuous infusion of a positive inotropic agent. Results showed a high dialyser extraction ratio averaging 38.3%, but a low dialysis clearance of 67 ml/min. The fraction removed by dialysis is 2.5%. We concluded that haemodialysis has little effect on dopamine blood levels, and consequently on drug pharmacokinetics, when the drug is delivered to haemodialysed patients under intravenous infusion.

Calibration↗

PubMed1996

Determination of clozapine in serum by radioreceptor assay versus high-performance liquid chromatography: possible detection of hydroxy-metabolites.

Clozapine is an antipsychotic drug with few extra-pyramidal motor side-effects, used to treat schizophrenia which is resistant to classical neuroleptic therapy. This report shows that norclozapine but not clozapine-N-oxide has the same D2 receptor affinity as clozapine. Assay results suggest a bimodal distribution which may be explained by CYP1A2 polymorphism. Extensive metabolizers could produce other active metabolites, probably other hydroxy-clozapine derivatives.

Animals↗

PubMed1996

Free gadolinium and gadodiamide, a gadolinium chelate used in magnetic resonance imaging: evaluation of their in vitro effects on human neutrophil viability.

Gadolinium (Gd3+) is known to be the most paramagnetic ion but is also a very toxic cation often used in pharmacology as a putative stretch-activated channel inhibitor. Gadodiamide, a nonionic Gd3+ chelate, is frequently injected i.v. into magnetic resonance imaging (MRI) to enhance contrast. To determine whether this complex is innocuous in humans, a cytotoxicity study was performed on artificially stimulated human neutrophils (HN). HN were incubated with gadodiamide and with free Gd3+ (GdCl3). The purpose of the study was to estimate possible cell damage after incubation, and to validate further trials based on stimulated cellular models. Measurement of lactate dehydrogenase (LDH) release and the Trypan blue exclusion test were used to assess viability. HN were separated from the blood of healthy volunteers and stimulated by phorbol 12-myristate 13-acetate, a pharmacological reactive which induces protein kinase C activation, superoxide generation, and degranulation by leukotcytes. This study demonstrated that an acellular model is necessary to interpret LDH results. In addition, the experimental conditions of the study demonstrated GdCl3 toxicity on HN viability, while gadodiamide was not harmful.

Analysis of Variance↗

PubMed1996

Oxygen species scavenging activity of phenolic extracts from hawthorn fresh plant organs and pharmaceutical preparations.

Different extracts of fresh vegetative and reproductive organs from Crataegus monogyna harvested during a whole season and from some pharmaceutical hawthorn preparations exhibit in vitro antioxidant activities using three different models of oxygen reactive species generation (superoxide anion, hydrogen peroxide and hypochlorous acid). All the tested samples show low IC50 values, the most efficient being fresh young leaves, fresh floral buds and pharmaceutical dried flowers. The activities seem to be especially bound to the total phenolic proanthocyanidin and flavonoid contents.

Anthocyanins↗

PubMed1996

Involvement of the extracellular calcium in the release of elastase and the human neutrophils oxidative burst.

Some proteases (particularly elastase) and metabolites of very reactive oxygen species (superoxide anion, hydrogen peroxide, hypochlorous acid and hydroxyl radicals) are generated by polymorphonuclear neutrophils (PMNs) during inflammatory disorders. Divalent cations, especially calcium (Ca2+) play an important regulatory role in the different PMNs functions. The aim of this study is to determine the role of extracellular calcium during the liberation of elastase and of reactive oxygen species production by human PMNs. Consequently, in order to stimulate PMNs, phorbolmyristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (fMLP) and opsonized zymosan (OZ) have been used. PMNs stimulated by OZ did not release elastase to reverse the PMA and fMLP systems. The production of elastase by PMNs stimulated by PMA to reverse the fMLP system is independent from the extracellular calcium, between 0.0 and 1.5 mM. With various higher concentrations of calcium, varying from 1.5 to 4.0 mM, the release of elastase by PMNs stimulated by PMA is extracellular calcium-dependent to reverse the fMLP system. The superoxide anion (O2-) generated by PMNs activated by fMLP is dependent from the extracellular calcium in the medium, whereas O2- production by PMA or OZ stimulated neutrophils was extracellular calcium-independent. These observations suggest that an influx of calcium may play an important role in the production of elastase and in the capacity of PMNs stimulated by fMLP to produce O2- to reverse the PMA and OZ systems.

Calcium↗

PubMed1995

Scavenging of reactive oxygen species by letosteine, a molecule with two blocked-SH groups. Comparison with free-SH drugs.

Acute production of reactive oxygen species by polymorphonuclear neutrophils during the respiratory burst may induce tissue injuries. In this in vitro study, it was demonstrated that letosteine, a mucolytic agent containing two blocked thiol groups, had antioxidant activity, but only when it was first submitted to alkaline hydrolysis. In a cell-free system, hydrogen peroxide, hypochlorous acid and hydroxyl radical concentrations were reduced by half by letosteine concentrations of 200, 15 and 350 mumol/l, respectively. The mechanism of letosteine action may be related to the -SH group liberated in vitro by hydrolysis, which seemed to react by scavenging the reactive oxygen species in the same way as acetylcysteine and MESNA, free-thiol drugs known for their antioxidant properties. So, letosteine, a compound with blocked -SH groups which in vivo can metabolically become free, may have a therapeutic application in preventing oxidative tissue injury damage induced by the respiratory burst.

Acetylcysteine↗

PubMed1995

High-performance liquid chromatographic method for the determination of budesonide in bronchoalveolar lavage of asthmatic patients.

A simple, sensitive and selective method for the determination of budesonide in bronchoalveolar lavage (BAL) using high-performance liquid chromatography (HPLC) with UV detection was developed. BAL samples were extracted twice with methylene chloride, the extracts were centrifuged and the organic layer separated and dried under nitrogen. The samples were reconstituted in the mobile phase and 80 microliters were injected on to a Spherisorb ODS column with UV absorbance detection at 250 nm. The mobile phase was methanol-aqueous buffer (69:31, v/v). Inter-assay coefficients of variation were measured at 7.81 and 500 ng/ml with ranges of 0.89-7.31%. Average recoveries were 97% or greater. This method was successfully implemented for the analysis of BAL from asthmatics, in order to establish the amount of budesonide available to the lung and to investigate the efficacy of inhaler systems. Patients (n = 9) inhaled four puffs of 200 micrograms of budesonide and BAL was performed 10 min after the last inhalation. Only four BAL out of the nine presented detectable amounts of budesonide. The concentrations in BAL in these four patients were 13.44-84.18 ng/ml, corresponding to total amounts of 0.847-7.997 micrograms.

Administration, Inhalation↗

PubMed1995

Stability, compatibility and plasticizer extraction of miconazole injection added to infusion solutions and stored in PVC containers.

The stability of miconazole in various diluents and polyvinyl chloride (PVC) containers was determined and the release of diethylhexyl phthalate (DEHP) from PVC bags into intravenous infusions of miconazole was measured. An injection formulation (80 ml) containing a 1% solution of miconazole with 11.5% of Cremophor EL was added to 250-ml PVC infusion bags containing 5% glucose injection or 0.9% sodium chloride injection, to give an initial nominal miconazole concentration of 2.42 mg ml-1, the mean concentration commonly used in clinical practice. Samples were assayed by stability-indicating high-performance liquid chromatography (HPLC) and the clarity was determined visually. Experiments were conducted to determine whether the stability and compatibility of miconazole would be compromised, and whether DEHP would be leached from PVC bags and PVC administration sets during storage and simulated infusion. There was no substantial loss of miconazole over 2 h simulated infusion irrespective of the diluent, and over 24 h storage irrespective of temperature (2-6 degrees C and 22-26 degrees C). All the solutions initially appeared slightly hazy. Leaching of DEHP was also detected during simulated delivery using PVC bags and PVC administration sets. There was a substantial difference between the amounts of DEHP released from PVC bags and from administration sets, and also between the amounts released in solutions stored in PVC bags at 2-6 degrees C and 22-26 degrees C over 24 h. At the dilution studied, miconazole was visually and chemically stable for up to 24 h. The storage of miconazole solutions in PVC bags seems to be limited by the leaching of DEHP rather than by degradation. To minimize patient exposure to DEHP, miconazole solutions should be infused immediately after their preparation in PVC bags.

Antifungal Agents↗

PubMed1994

Stability and compatibility studies of cephamandole nafate with PVC infusion bags.

A rapid isocratic technique was developed for the analysis of cephamandole nafate and cephamandole in parenteral solutions using high-performance liquid chromatography (HPLC) with UV detection and C18 column. The availability and compatibility of drugs from solutions infused via plastic infusion bags through plastic administration sets have been examined. No significant drugs loss was observed during simulated infusions (n = 4) for 1 h using PVC infusion bags and administration sets. No significant difference was found between infusion solutions (5% glucose or 0.9% NaCl). The stability of drugs was also studied in solution in PVC bags after storage at room temperature and at 4 degrees C without protection from light. The results show the stability of cephamandole nafate during 24 h at room temperature and 7 days storage at 4 degrees C to be satisfactory, irrespective of the infusion solution (5% glucose or 0.9% NaCl). However, an almost immediate and total transformation of cephamandole nafate to cephamandole in 5% glucose has been observed, whereas in 0.9% NaCl both forms were found in similar proportions.

Calibration↗

PubMed1994

Stability and compatibility of cisplatin and carboplatin with PVC infusion bags.

The availability and compatibility of drugs from solutions infused via PVC infusion bags through PVC administration sets have been examined. No significant drug loss was observed during simulated infusions using PVC infusion bags and administration sets over time periods used in hospitals (cisplatin, 2 h; carboplatin, 1 h). The stability of carboplatin was studied in 5% dextrose. In 0.9% NaCl, we observed that carboplatin could be converted to cisplatin in the presence of chloride ions. With cisplatin, no significant difference was found between infusion solutions (5% dextrose or 0.9% NaCl). The stability of cisplatin (5% dextrose or 0.9% NaCl) and carboplatin (5% dextrose) was also studied in PVC bags after storage in the dark at room temperature. The results show that the drugs were stable over the 9-day storage period studied.

Biocompatible Materials↗

PubMed1994

Protective role of glutathione on alpha 1 proteinase inhibitor inactivation by the myeloperoxidase system. Hypothetic study for therapeutic strategy in the management of smokers' emphysema.

In smoking subjects with obvious emphysema, the interaction between neutrophil-derived MPO and H2O2 produced by alveolar inflammatory cells (alveolar macrophages (AM) and polymorphonuclear neutrophils (PMN)) has the ability to spontaneously inactivate, in vitro, the alpha 1 proteinase inhibitor (alpha 1PI). This inactivation can induce a desequilibrium of the protease-antiprotease balance in the lungs. In this study, we investigated the ability of glutathione to protect alpha 1PI. In a cellular model of alpha 1PI inactivation mimicking the effects of alveolar inflammatory cells present in the lower respiratory tract of smoking patients with emphysema, we demonstrated that glutathione can protect alpha 1PI against the oxidative inactivation by these activated cells. This protection has been computed in a cellular experimentation (AM and MPO-system) with a 50% inhibitory concentration of 62 microM. Moreover, glutathione has an important inhibitory effect directly on H2O2 released by PMA-stimulated AM (IC50 = 30 microM) or PMA stimulated PMN (IC50 = 70 microM). The mechanism, which governs glutathione may be a result of a scavenging effect on H2O2 as demonstrated in a free cellular experiment. With this in vitro demonstrated effectiveness, glutathione as a therapeutic antioxidant, via the aerosol, has been proposed, in order to prevent tissue damage, inflicted by an excess of activated phagocytic cells, in some lung diseases such as smoking patients with emphysema.

Glutathione↗