A magnetic glassy phase in Fe(1+y)Se(x)Te(1-x) single crystals

The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content. At the same time all the tested samples manifest a marked glassy character that vanishes for high Se contents. The presence of local electronic/compositional inhomogeneities most likely favours the growth of clusters whose magnetic moment 'freezes' at low temperature. This glassy magnetic phase justifies both the coherent muon precession seen at short times in the asymmetry data, as well as the glassy behaviour evidenced by both dc and ac magnetometry.

Imaging the essential role of spin fluctuations in high-T(c) superconductivity

We have used scanning tunneling spectroscopy to investigate short-length electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+delta) (Bi-2223). We show that the superconducting gap and the energy Omega(dip), defined as the difference between the dip minimum and the gap, are both modulated in space following the lattice superstructure and are locally anticorrelated. Based on fits of our data to a microscopic strong-coupling model, we show that Omega(dip) is an accurate measure of the collective-mode energy in Bi-2223. We conclude that the collective mode responsible for the dip is a local excitation with a doping dependent energy and is most likely the (pi, pi) spin resonance.

DHA-enriched phospholipid diets modulate age-related alterations in rat hippocampus

Our previous work on rat hippocampus showed that a loss of docosahexaenoic acid (DHA) occurs in the fatty acid composition of phosphatidylethanolamine (PE), plasmenylethanolamine (PmE) and phosphatidylserine (PS) with increasing age. The present study investigated whether a DHA-enriched phospholipid dietary supplement could restore DHA levels and cholinergic activity. Male rats were fed a balanced diet containing both linoleic and alpha-linolenic acids until the age of 2, 18 and 21 months. From 18 to 21 months, one subgroup received a diet supplemented with DHA-enriched phospholipids from egg yolk (E-PL), and another a diet with DHA-enriched phospholipids from pig brain (B-PL). Compared to the control diet, the E-PL diet restored the proportion of polyunsaturated fatty acids (PUFAs: 22:6n-3 and 20:4n-6) in PE and PmE, while enhancing spontaneous and evoked-acetylcholine (Ach) release. The B-PL diet had no effect on PUFAs, but increased basal extracellular levels of Ach in 21-month-old rats as compared to the age-matched control. Our results show that supplementation with DHA-enriched egg PL can enhance Ach release and correct PUFA composition.

Impairment of the neuronal dopamine transporter activity in MPP(+)-treated rat was not prevented by treatments with nitric oxide synthase or poly(ADP-ribose) polymerase inhibitors

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes, via its metabolite MPP(+), damages of the nigrostriatal dopaminergic pathway, similar to those observed in Parkinson's disease. An intranigral injection of 10 microg MPP(+) in rat induced a decrease of about 30% of the neuronal dopamine transporter (DAT) activity 21 days after lesion. Based on the hypothesis that MPTP/MPP(+) neurotoxicity involves the nitric oxide (NO) production and/or an activation of poly(ADP-ribose) polymerase (PARP), we investigated the preventive effects of a treatment either with L-Name, a NO synthase (NOS) inhibitor or 3-aminobenzamide, a PARP inhibitor on the reduction of dopamine uptake induced by MPP(+). Rats received a daily injection i.p. of 50 mg/kg L-Name or 10 mg/kg 3-aminobenzamide 3 days before and during 21 days after the MPP(+) lesion. The results showed that inhibitors of NOS and PARP did not prevent the alteration of DAT activity induced by 10 microg MPP(+), indicating that NO and PARP were not involved in the biochemical cascade leading to the inhibition of rat DAT activity by MPP(+) in our experimental conditions.

Evidence against a major role of plasmalogens in the resistance of astrocytes in lactic acid-induced oxidative stress in vitro

Astrocytes are known to play a key role in buffering extracellular pH variations and, in addition, they are particularly resistant to oxidative stress and subsequent lipid peroxidation. This great resistance may be ascribed to the presence of high concentrations of certain antioxidants, but another explanation may be the presence of a high quantity of plasmalogens, which are a special group of glycerophospholipids characterized by a vinyl ether bond instead of an ester bond in the sn-1 position of the glycerol backbone. Plasmalogens are sensitive to free radical attack and acidity, and numerous works have supported the hypothesis that they may be antioxidant molecules that protect cells from oxidative stress. The aim of this work was to investigate, on astrocytes in lactic acid-induced oxidative stress (pH 5.5), the behavior of phospholipids and, in particular, plasmalogens. Two main techniques, based on the susceptibility of the vinyl ether bond to hydrolysis, were employed in this study to measure plasmalogen levels. In both cases, the sn-1 vinyl ether linkage was cleaved using mercuric chloride, producing a lysophospholipid that was assessed by phosphorus measurement or using HCl treatment, producing a long-chain fatty aldehyde assayed by gas chromatography/mass spectrometry. On astrocytes in culture, only plasmenylethanolamine (PlmEtn) was evidenced, representing 40% of glycerophosphoethanolamine lipids. When astrocytes were incubated with lactic acid, no modification in the amount of PlmEtn was seen. Furthermore, free aldehydes and aldehydes corresponding to the quantity of intact plasmalogens were similar to those observed on controls. In addition, the constancy of two lipid peroxidation markers, thiobarbituric acid reactive substances and polyunsaturated fatty acids, was clear evidence of the resistance of these cells in lactic acid conditions. In conclusion, our results fail to demonstrate a major role of plasmalogens in the resistance of astrocytes in lactic acid-induced oxidative stress.

Age-related changes in ethanolamine glycerophospholipid fatty acid levels in rat frontal cortex and hippocampus

Morphological and biochemical alterations are associated with a progressive age-related cognitive deficit. Plasmenylethanolamine, the major brain plasmalogen, may be modified during aging because of a possible antioxidant role and involvement in synaptic transmission. Two- and 18-month-old rats were used to study the effect of aging on the levels and acyl composition of plasmenylethanolamine (PmE), phosphatidylethanolamine (PE), and phosphatidylserine (PS) in the frontal cortex and hippocampus. Aging only reduced significantly the PE levels in the frontal cortex. In 18-month-old rats, the fatty acid composition of the three phospholipid classes studied showed an increase of monounsaturated fatty acid (18:1 n-9 and 20:1 n-9) and a decrease in polyunsaturated fatty acid (PUFAs), essentially docosahexaenoic acid (DHA). DHA was markedly decreased in hippocampus PE. DHA, but also arachidonic acid, were considerably lower in frontal cortex PmE. PS modifications were similar in both regions. Hippocampus and frontal cortex underwent specific age-induced modifications in PmE and PE acyl composition. This could produce different effects on the functional ability of these two structures involved in the processes of specific memorization.

Non-thermal effects of continuous 2.45 GHz microwaves on Fas-induced apoptosis in human Jurkat T-cell line

Non-thermal effects of microwaves (MWs) are one of the main issues studied for revising standards. The effects of MW exposure on apoptosis at non-thermal level (48 h, 2.45 GHz, 5 mW/cm2) have been studied. Results obtained assess non-thermal MW effects on Fas, but neither on butyrate- nor on ceramide-induced apoptosis in human Jurkat T-cell line. These data show that MW interacts either with Fas pathway between receptor and caspase-3 activation or on membrane proteins (i.e. Fas receptor or neurosphyngomyelinase).

Origin of 4-hydroxynonenal incubation-induced inhibition of dopamine transporter and Na+/K+ adenosine triphosphate in rat striatal synaptosomes

Previous experiments reported that an incubation of striatal synaptosomes with 4-hydroxynonenal (4-HNE) resulted in an inhibition of dopamine (DA) uptake and Na+/K+ adenosine triphosphate (ATPase) activity. The present work investigated whether theses inhibitions are related to a 4-HNE binding to the DA transporter (DAT) and the Na+/K+ ATPase. The number of specific [125I]-PE21 binding sites on the DAT was significantly reduced after incubation with 4-HNE. The Na+/K+ ATPase activity decrease induced by 4-HNE was partially reversed, in a dose-dependent manner, by veratridine, a pump stimulator agent. Our previous data (Morel, P., Tallineau, C., Pontcharraud, R., Piriou, A. and Huguet, F., Effects of 4-hydroxynonenal, a lipid peroxidation product, on dopamine transport and Na+/K+ ATPase in rat striatal synaptosomes. Neurochem. Int., 33 (1999) 531-540) combining with the data observed in this study suggest that changes in DA uptake in striatal synaptosomes are directly related to 4-HNE binding to the DAT, whereas the decrease in Na+/K+ ATPase activity resulted only partially from 4-HNE binding to the pump and is mainly secondary to membrane lipid disruption.

Synthesis and antioxidant activity of new tetraarylpyrroles

The synthesis and in vitro antioxidant activity of 17 new tetraarylpyrroles are investigated by 2 tests highly documented in the literature: capability to prevent Fe(2+)-induced lipid peroxidation on microsomes, which is a membrane preparation rich in polyunsaturated fatty acids, and direct scavenging effect on a stable free radical, 1,l-diphenyl-2-picryl-hydrazyl (DPPH). For the Fe(2+)-induced microsomal lipid peroxidation system, the results show that molecules which possess 2-pyrazinyl or 2-pyridyl in the 3- and 4-positions on the pyrrole ring are the most efficient. Introduction of methoxy groups on the phenyl ring in the 2- and 5-positions increases the effects but the higher activity is obtained with 2-furyl or 2-thienyl. The only compounds which possess a direct scavenger effect on trapping the stable free radical DPPH are those which have 2-pyridyl in the 3- and 4-positions and 2-furyl or 2-thienyl in the 2- and 5-positions.

Lactic acid-induced increase of extracellular dopamine measured by microdialysis in rat striatum: evidence for glutamatergic and oxidative mechanisms

Striatal lactacidosis was induced by direct lactic acid perfusion to obtain a local pH as close as possible to that observed in ischemia. In a previous study we showed that such lactacidosis produces a diphasic increase in extracellular dopamine (DA). The present work investigated whether DA accumulation is related to a glutamatergic mechanism and/or production of reactive oxygen species (ROS) in the striatum. Concentrations of extracellular DA, glutamate and hydroxyl radicals ((.)OH) were measured in the presence or absence of an N-methyl-D-aspartate (NMDA) receptor blocker (dizocilpine, MK-801) or an antioxidant (Trolox). Measurements were performed using high-performance liquid chromatography (HPLC) with electrochemical and fluorimetric detection on samples obtained by an in vivo microdialysis perfusion technique and stored at -80 degrees C. The increase in lactic acid-induced DA was entirely suppressed by MK-801 and Trolox. Lactacidosis also induced an increase in extracellular glutamate and (.)OH concentrations at the same time as the first DA accumulation, as well as another (.)OH accumulation which preceded and accompanied the second DA concentration peak. Glutamate release was totally inhibited by MK-801 or Trolox. The first peak of (.)OH production was completely suppressed by MK-801 and Trolox, but the second one was only suppressed by Trolox. These data showed that the increase in DA induced by lactic acid was related to glutamatergic excitotoxicity and ROS production, suggested that the kinetic of events was different for the two DA accumulations.

Origin of extracellular dopamine increase induced by lactic acid striatal perfusion monitored by microdialysis in the awake rat

In previous studies we showed that a striatal lactic acid perfusion-induced lactacidosis produces a diphasic increase in extracellular dopamine (DA). In the present study, different pharmacological reagents were used to determine the origin of accumulated DA. Our data show that both DA accumulations were totally suppressed by tetrodotoxin and nicardipine, indicating a relationship with membrane depolarization and a Ca(2+)-dependent effect. The first DA peak was largely reduced by a specific inhibitor of DA uptake such as GBR-12935, and the second was totally suppressed by tyramine and reserpine and lowered and delayed by GBR-12935. These results compared to data in the literature suggest that the first increase in extracellular DA resulted mainly from a release of cytosolic DA by reversal of the DA transporter, while the second was mainly due to a release of vesicular DA by exocytosis. These data indicate that lactic acid perfusion helps clarify the mechanisms involved in this process and could be useful for the study of new treatments against the hyperactive dopaminergic reaction occuring during ischemia.

[Evaluation of six rapid tests for screening of cannabis in sweat, saliva and tears]

In order to demonstrate an intake of cannabis, there are a number of rapid tests, all of them being focused on urine. In this study, we evaluated the results of six tests when applied to sweat (DrugWipe), saliva and urine (Syva Rapidtest, Biomedix, Frontline, DrugWipe, Cortez Dako). Fifty regular users of cannabis and fifty persons who denied consuming it were studied. The results obtained with DrugWipe in sweat were compared with anamnesis data, whereas results obtained in saliva and urine were compared with those of gas chromatography--mass spectrometry. The results indicate that DrugWipe may be useful for screening cannabis in sweat when the intake took place less than two hours before. The results obtained in saliva showed that none of the tests studied are reliable to be used with this medium, because of the great number of false positive and false negative results. With urine, four tests (Syva Rapidtest, Biomedix, Cortez, Dako) led to very good results and may be recommended when an immediate presumptive test result is required.

[Tox-Didact:CD-ROM for toxicology education. Value in hospital toxicology]

New teaching techniques should allow students more independence in their training, particularly in learning from problems and using clinical reasoning. We designed Tox-Didact, a modular multimedia educational software program, which is suitable for both students and professionals, regardless of their orientation (pharmacy or medicine) or level. Each module concerns four domains: diagnosis, biological monitoring, curative treatment and prevention. Tox-Didact is multidisciplinary, interactive, simple to use and reliable. Nineteen modules are now being prepared. In final form, Tox-Didact will cover all the acute and chronic pathologies of toxicology.

Effects of 4-hydroxynonenal, a lipid peroxidation product, on dopamine transport and Na+/K+ ATPase in rat striatal synaptosomes

Incubation of rat striatal synaptosomes in ascorbic acid induced the production of thiobarbituric acid reactive substances, a marker of lipid peroxidation, and 4-hydroxynonenal (4-HNE), a lipid peroxidation aldehydic product. Incubations with 4-HNE, used at a range of concentrations comparable to those obtained during peroxidation, induced a simultaneous, dose-dependent decrease of dopamine (DA) uptake and Na+/K+ ATPase activity and a loss of sulfhydryl (SH) groups. Similar results were observed in a previous study when lipid peroxidation was induced after incubation of synaptosomes in ascorbic acid. Taken together, these data suggest that 4-HNE is an important mediator of oxidative stress and may alter DA uptake after binding to SH groups of the DA transporter and to Na+/K+ ATPase. These toxic events may contribute to the onset and progression of Parkinson's disease.

Characterization of both dopamine uptake systems in rat striatal slices by specific pharmacological tools

Previous results have shown that modifications of dopamine (DA) high-affinity uptake1 and those of DA low-affinity uptake2 in rat striatal slices were different after autoxidation of this model and in the presence of antioxidants. The aim of this study was to determine whether these two DA uptake systems correspond to two different dopamine transporters or rather to a single one. A lesion into the substantia nigra of animals by injection of 6-hydroxydopamine, a neurotoxic substance of nigrostriatal dopaminergic neurons led to the suppression of both DA uptake systems. These two DA uptake systems were not modified when animals were treated by reserpine or tetrabenazine, which inhibit the vesicular monoamine transporter. Moreover, they were sodium- and temperature-dependent. Experiments with specific inhibitors showed that 1-[2-(diphenylmethoxy) ethyl]-4-(3-phenylpropyl)-piperazine dihydrochloride (GBR-12935) and (E)-N-(3-iodoprop-2-enyl)-2beta-carbomethoxy-3beta-(4'-tolyl ) nortropane chloride (PE2I), two selective DA uptake inhibitors, were significantly more potent than fluoxetine and nisoxetine (selective serotonin and norepinephrine uptake inhibitors respectively) in both DA uptake systems. However, the concentrations of these products inhibiting low-affinity uptake2 by 50% were much greater than those for high-affinity uptake1. Our data indicate that both DA uptake systems are neuronal, independent of the vesicular monoamine transporter, active and specific for dopamine. Our results suggest that high-affinity uptake1 and low-affinity uptake2 correspond to the same dopamine transporter, but would be situated at different levels in the striatal slice model. Uptake1 could take place at the periphery of the slice whereas uptake2 in the depth of the slice.

Membrane carbohydrate conjugates desialylation does not alter [3H]-dopamine uptake in rat striatal slices

Incubation of rat striatal slices induced a large decrease (about 50%) of DA uptake and a slight desialylation of polysialogangliosides (GT1b, GD1b, GD1a) with an increase of monosialogangliosides (GM1). Moreover, a pretreatment of slices by exogenous added neuraminidase of Vibrio cholerae did not modify DA uptake, although the pattern of gangliosides was modified and there was considerable loss (about 45%) of sialic acid in gangliosides and glycoproteins. It was verified that neuraminidase activity occured in synaptic membrane. Thus, DA uptake was apparently not altered by desialylation of plasma membrane carbohydrate conjugates.

Extracellular dopamine and catabolites in rat striatum during lactic acid perfusion as determined by in vivo microdialysis

Many experimental studies concerning hypoxia or ischemia have reported a decrease in intra/extracellular pH and massive dopamine (DA) release in the striatum. The present work investigated whether the increase in striatal extracellular DA is related to acidification or to lactate production. Striatal perfusion of lactic acid (pH 5.5) by microdialysis in conscious freely-moving rats induced an increase in extracellular concentrations of DA and catabolites, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC), as a probable result of acidification. Perfusion with sodium lactate (pH 7.4) failed to modify DA and catabolite release, whereas orthophosphoric acid produced the same effect as lactic acid. As lactic acidosis is known to induce a displacement of iron from its uptake sites, the possible role of this metal in response to acidosis was studied by perfusing ferrozine, an iron complexing agent, at the same time as lactic acid. The results showed that ferrous ions are involved in the process and suggested that oxygen free radicals play a role in the extracellular release of DA. Thus, lactic acid perfusion in rat striatum would appear to be a useful model for in vivo studies of the mechanisms responsible for increases in extracellular DA during hypoxia and ischemia.

Possible relationship between changes in [3H]DA uptake and autoxidation in rat striatal slices

Many recent studies have suggested that oxidative damage is an important factor in several neurodegenerative disorders. Our investigations considered whether autoxidation of rat striatal slices modified dopamine uptake. Biochemical assays (TBARS, MDA-TBA complex, aldehydes, and fluorescent lipid-soluble products) and a [3H]DA uptake assay were performed on nonincubated striatal slices and on slices incubated for 150 min at 37 degreesC in Krebs-Ringer buffer without addition of free-radical generators. The results showed that spontaneous lipid peroxidation occured during incubation and that DA uptake kinetic was biphasic (high-affinity uptake1 and low-affinity uptake2) with a significant decrease of maximal velocity of uptake. Ascorbate, a known antioxidant, was used to determine whether a relationship existed between lipid peroxidation and reduced dopamine uptake. Addition of ascorbate (100 and 500 microM) in Krebs-Ringer buffer for 150 min at 37 degreesC failed to indicate whether decreased [3H]DA uptake resulted from lipid peroxidation. In fact, ascorbate acted as a prooxidant, only preventing decreased DA uptake2 at 100 microM. Trolox, another antioxidant, inhibited lipid peroxidation by about 95% with a concentration of 700 microM and protected only uptake1. With a concentration of 5000 microM, Trolox also protected uptake2. On the whole, these results indicate that spontaneous autoxidation in rat striatal slices was associated with a lipid peroxidation process that altered the DA uptake system.

MPTP toxicity in rat striatal slices: dopamine uptake alteration does not appear to be related to lipid peroxidation

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which is used to create experimental models of parkinsonism, induces both dopaminergic neurotoxicity and peroxidation reactions. The present work investigated the interaction between the dopamine (DA) uptake system, lipid peroxidation and MPTP in a rat striatum slice model. [3H]DA uptake was decreased and the concentration of thiobarbituric acid reactive substances (TBARS) increased after a plain preincubation in Krebs-Ringer bicarbonate buffer for 150 min. The decrease in [3H]DA uptake and the increase in TBARS were suppressed by the iron-chelating agent desferrioxamine. Inhibition of [3H]DA uptake was intensified, [3H]GBR 12 935 binding to DA uptake sites was decreased and TBARS production was inhibited in slices after preincubation with MPTP. MPTP effects were inhibited by L-deprenyl, a MAO-B inhibitor. These results suggest that the spontaneous decrease in DA uptake during simple preincubation in pure Krebs-Ringer solution was related to spontaneous TBARS generation. During MPTP preincubation, alteration of the DA uptake mechanism was not due to additional lipid peroxidation since TBARS production was decreased. MPTP effects could have resulted from other events which are discussed.

Alterations in the ganglioside composition of rat cortical brain slices during experimental lactic acidosis: implications of an enzymatic process independent of the oxidative stress

Several in vitro studies have shown that lactic acidosis plays a role in brain damage by enhancing free radical formation and lipid peroxidation. The purpose of this study was to determine whether gangliosides are affected by lactic acid-induced oxidation in rat brain tissues. Cortical brain slices were incubated at 37 degrees C for 5 or 17 h in Krebs-Ringer buffer containing 20 mM lactic acid (final pH 5.5) previously equilibrated with 100% O2. Damage from lipid peroxidation was estimated by measurement of thiobarbituric acid-reactive substances (TBARS) and analysis of polyunsaturated fatty acids (PUFAs). Gangliosides were studied by high-performance thin-layer chromatography. Incubation with lactic acid induced overproduction of TBARS, whereas PUFAs were only slightly degraded, even after 17 h of incubation. However, the major modifications in the ganglioside profile occurred after 17 h of incubation. Gangliosides GD1a and GT1b decreased in conjunction with a substantial increase in the GM1 percentage. The addition of butylated-hydroxytoluene and desferrioxamine in the incubation medium, or incubation under 100% nitrogen, abolished TBARS production but not the ganglioside modifications, indicating that the change in ganglioside distribution was not related to oxidative stress induced by lactic acid. To investigate the possibility of an enzymatic process activated by the pH shift, slices were incubated with lactic acid in presence of 2,3-dehydro-2-deoxy-N-acetylneuraminic acid, a specific inhibitor of sialidase. In these conditions, no change in gangliosides profile occurred. These results demonstrate that sialidase is responsible for the alterations in the gangliosides composition of rat cortical brain slices during lactic acidosis.

In vitro study of the antiseborrheic activity of zinc L-cysteate, a novel zinc compound, on rat preputial gland

The antiseborrheic effect of zinc L-cysteate, a new zinc compound, was evaluated in vitro by determining the lipidic metabolic activity of rat preputial glands as measured by incorporation of 14C-sodium acetate. At 10(-3) and 10(-4) mol/l, zinc L-cysteate was more active than S-carboxymethyl L-cysteine used as reference in corresponding concentrations (p < 0.05 and p < 0.01, respectively). The pharmacologic results seem promising for clinical studies in dermatology.

Nephrotoxicity of gentamicin and vancomycin given alone and in combination as determined by enzymuria and cortical antibiotic levels in rats

The purpose of this study was to compare the nephrotoxicity of gentamicin and vancomycin alone and in combination. Thirty-two male Sprague-Dawley rats were randomized into 4 groups of 8 animals. Each group received 200mg/kg gentamicin (G) i.m., or 300 mg/kg vancomycin (V) i.v., or an association of 200 mg/kg gentamicin + 300 mg/kg vancomycin (i.m. and i.v., respectively), or 0.9% NaCl solution i.m. and i.v. (controls). To determine AAP, GGT, and NAG enzyme excretions, urine samples were taken over 24-h periods before and after the start of the experiment. A single renal cortical sample was obtained at necropsy for quantitation of antibiotic levels. No significant modifications of urinary excretions of creatinine and enzymuria were noted during the 24-h period before each drug administration or in controls. AAP, GGT, and NAG excretions were significantly increased after G and G + V injections (p < 0.001), whereas only AAP and GGT were statistically higher in rats receiving V (p < 0.05). NAG elimination (mean +/- SD) was higher in G + V (16.0 +/- 0.2 IU/mmol creatinine/24 h; p < 0.001) than g (8.8 +/- 0.6) or V (1.7 +/- 0.2). Surprisingly, mean vancomycin cortical levels decreased in the combination (827 +/- 131 vs. 1964 +/- 23 micrograms/g for V alone; p < 0.001), whereas gentamicin concentration was unchanged (826 +/- 66 vs. 839 +/- 28 micrograms/g for G alone). Determination of enzymuria allowed the nephrotoxicity of the antibiotics to be graded in the following order: vancomycin + gentamicin > gentamicin > vancomycin.

Absence of gastrointestinal absorption or urinary excretion of aluminium from an allantoinate complex contained in two antacid formulations in patients with normal renal function

We studied the plasma and urinary excretion levels of aluminum (Al) on day 0, 10 and 30 in 79 patients with gastrointestinal symptoms and normal renal function who were receiving a complex based on Al allantoinates [C4H5N4 O3 Al (OH)2] and [C4H5N4 O3 Cl Al2 (OH)4]. We evaluated the extent of Al absorption after repeated administration of this complex in two antacid formulations, Ulfon Lyoc in lyophilised tablet form (group 1; n = 40) and Ulfon suspension (group 2; n = 39). The total Al load for each antacid and patient was 512 mg daily for a total of 15360 mg during the 30-day treatment. No significant rise in plasma Al concentration was noted with either formulation between day 0 and 10, day 0 and 30 or day 10 and 30, nor was there any significant increase in urinary excretion levels. Al absorption was not increased and no toxic effects were noted, indicating that such formulations are suitable for long-term therapy in patients with gastrointestinal symptoms.

Interaction of metaiodobenzylguanidine with cardioactive drugs: an in vitro study

Metaiodobenzylguanidine (MIBG), an analogue of noradrenaline, is used to explore the functional integrity of sympathetic nerve endings in the human heart. Various drugs inhibit noradrenaline transport systems and may block the uptake of MIBG. As in vivo studies of the effect of these drugs on myocardial [123I]MIBG uptake are often difficult to perform, we used an in vitro human blood platelet model for this purpose. A platelet preparation from healthy volunteers was incubated with [125I]MIBG alone or different concentrations of drugs currently used in cardiology. Labetalol and propranolol inhibited [125I]MIBG uptake, whereas all other drugs tested (other beta-blockers, calcium inhibitors, digoxin and amiodarone) had no effect even at doses exceeding 50 microM. The labetalol dose inhibiting 50% of [125I]MIBG uptake was lower than the plasma concentration of this drug in treated patients, whereas the propranolol dose was higher. This in vitro study of the effect of drugs on MIBG uptake by human blood platelets is predictive of their in vivo effect on myocardial uptake of [123I]MIBG in treated patients, provided that plasma concentration is taken into account.

Gentamicin-induced kidney damage and lipid peroxidation in rats

Although it has been reported that injections of gentamicin induces lipid peroxidation in rat renal cortex (Ramsammy et al. (1985) Biochem. Pharmacol. 34, 3895-3900), our results showed no modification of thiobarbituric-reagent substances (TBARS) or in analysis of the polyunsaturated fatty acid profile. Moreover, endogenous vitamin E and glutathione were not consumed. In in vitro systems, gentamicin incubated with microsomes, homogenates and kidney slices from the normal rat failed to induce lipid peroxidation. We show that the increase in TBARS in vivo detected by Ramsammy et al. was wrongly attributed to the oxidant power of gentamicin. As this antibiotic does react positively to thiobarbituric acid in the presence of a system generating free radicals, it is possible that these authors accidentally introduced such a system into their experiments.

Rapid and specific high-performance liquid chromatographic method for the determination of iodide in urine

A rapid and specific method for the determination of iodide in urine by high-performance liquid chromatography on an anion-exchange column with electrochemical detection is described. The assay is reproducible as judged by the coefficient of variation of less than 4% at all concentrations used. The limit of detection was 0.1 mumol, and the calibration graph was linear for concentrations between 0.1 and 200 mumol. Using this method, healthy volunteers were found to excrete 69 +/- 39 mumol of iodide per mole of creatinine.

Lack of correlation between TBARS production and PUFA degradation during incubation of membrane erythrocytes in an OH. (Fe2+/H2O2) generator system

We investigated the effects of an OH. (Fe2+/H2O2) generator system on erythrocyte membrane, particularly the time-course of lipid peroxidation as estimated by measurement of conjugated dienes, thiobarbituric reactive substances (TBARS), lipofuscin-like pigments, and alpha-tocopherol. Polyunsaturated fatty acids (PUFAs), especially arachidonic acid (20:4 omega 6) and docosahexenoic acid (22:6 omega 3), were also measured. Erythrocyte membranes were suspended in phosphate buffer containing Fe2+ (200 microM) and H2O2 (1.42 mM), and incubated in a shaking water bath at 37 degrees C. Initially, there was an increase in TBARS and lipofuscin-like pigments, two well-known end products of PUFA oxidative degradation, whereas PUFAs remained unchanged (incubation time: 1 h). After two or more hours of incubation, marked lipid peroxidation was noted, with the appearance of conjugated dienes and a decrease of PUFAs, indicating that lipid peroxidation had occurred after a lag phase during which TBARS were not produced from PUFAs. This suggests that another OH. target was involved.

Decreased cerebral 5-HT1A receptors during ageing: reversal by Ginkgo biloba extract (EGb 761)

Investigation of [3H]8-hydroxy-2(di-n-propylamino)tetralin binding to 5-HT1A receptors in cerebral cortex membranes of Wistar rats showed that the maximal number of binding sites (Bmax) was reduced significantly (22%) in aged (24-month-old) as compared with young (4-month-old) animals. Chronic treatment with Ginkgo biloba extract did not alter binding in young rats but increased binding density significantly (33%) in aged rats. These results confirm previously described age-related 5-hydroxytryptaminergic alterations. Together with data in the literature, they also suggest a restorative effect in aged rats, associated with decreased receptor density resulting from the protective action of Ginkgo biloba extract treatment on neuronal membrane.

Iron- and lactic acid-induced lipid peroxidation in rat kidney homogenates and slices

Lactic acid 4 mM acted as a lipoperoxidant by increasing production of thiobarbituric acid-reactive substances (TBARS) in rat kidney slices and homogenates. This effect occurred mainly when slices and homogenates were incubated in a pH 5.4 medium conductive to full expression of compound acidity. TBARS increase was only slight when incubation was performed in Krebs buffer, pH 7.4. Moreover, sodium lactate 4 mM increased TBARS production only when homogenates were incubated in the pH 5.4 medium. Deferoxamine (1 mM) inhibited the prooxidant effect of lactic acid 4 mM, and TBARS increase was correlated with iron release. The iron mobilized may come from reserves where it is weakly bound or from ferritin; and ascorbic acid, present in low quantities in kidney, might trigger the release of this product.

Age-related changes of noradrenergic-NPY interaction in rat brain: norepinephrine, NPY levels and alpha-adrenoceptors

Noradrenergic-neuropeptide Y interaction, which is implicated in different physiological functions, was studied in senescent rats. Norepinephrine (NE) and neuropeptide Y (NPY) levels were measured in brainstem and hypothalamus, and alpha-adrenergic binding was investigated in brainstem in young (4 months) and old (34 months) Wistar rats. NE concentration was the same in senescent rats, whereas NPY concentration was decreased both in brainstem and hypothalamus compared to levels in young rats. [3H]prazosin binding to alpha 1-adrenoceptors was not modified, but [3H]rauwolscine binding to alpha 2-adrenoceptors was altered with age. In fact, the density of alpha 2-adrenoceptors (Bmax) was lower, while the binding affinity (Kd) was increased in old compared to young rats. These results suggest that the decrease of NPY levels could be one of the possible reasons for changes in [3H]rauwolscine binding to alpha 2-adrenoceptors in old rats. The G-protein-adenylate cyclase system, which is impaired in senescent rats, could be involved in the disorganization of noradrenergic-NPY interaction.

Endothelin modulates dihydropyridine receptor decreased binding in hippocampal slices from normotensive and spontaneously hypertensive rats

Previous studies in rats have demonstrated both the link between voltage-operated calcium channels and endothelin and their cerebral involvement in the pathophysiology of spontaneous hypertension. In the present study, the interaction of endothelin with specific dihydropyridine (DHP) binding sites was investigated using the brain slices model. In rat hippocampal slices, pre-incubation with Bay K 8644 decreased [3H] (+) PN 200-110 binding. There was no difference in agonist-induced decrease of DHP binding in normotensive and spontaneously hypertensive (SH) rats. The effect of Bay K 8644 was partially inhibited by endothelin but not by angiotensin in both normotensive and hypertensive rats. These data compared to those of other studies suggest that DHP binding sites which are regulated by endothelin are post-synaptic. We conclude that brain slices provide a good in vitro model to study DHP receptor regulation and to explore endothelin interactions with DHP-sensitive Ca2+ channels.

Evidence of lipoperoxidation induced by lactic acid on kidney homogenates

Sawas and Gilbert (Arch. Int. Pharmacodyn. Ther., 276 (1985) 301-312) reported that the commercial solution of haloperidol induces lipoperoxidation of kidney homogenates from Sprague-Dawley rats. However, it would appear that this effect is attributable to the excipient, lactic acid, rather than to haloperidol itself. Lactic acid enhances susceptibility to lipoperoxidation of kidney homogenates in a dose- and time-dependent manner by increasing production of thiobarbituric acid-reactive substances and slightly decreasing polyunsaturated fatty acids such as arachidonic acid and docosahexaenoic acid. This stimulation of lipoperoxidation may be attributed to a mechanism less dependent on enzymatic action than on Fe2+ and Fe3+. Lactic acid may facilitate iron release and formation of iron complexes, factors which increase susceptibility to oxidative stress.

A comparative study of enzymuria, in the rat, of the drug combinations amikacin/vancomycin and amikacin/teicoplanin

The aim of this study was to compare nephrotoxicity of the combinations amikacin/vancomycin and amikacin/teicoplanin. Eighteen male Wistar rats were divided into 3 groups of 6 animals each. The first group received 50 mg.kg-1 of amikacin (i.m. route) and 100 mg.kg-1 of vancomycin (i.p. route). The second group received 50 mg.kg-1 of amikacin (i.m. route) and 40 mg.kg-1 of teicoplanin (i.p. route). The third group received an isotonic solution of sodium chloride. The antibiotics were injected for a period of 6 days. Urine samples of animals were taken 24 h before the beginning of the experiment, then every day, throughout the duration of the treatment (6 days), continuing for an additional 3 days following completion of the administration of the drugs. There were no significant modifications in the urinary excretions of alanine aminopeptidase and the creatinine between the 3 groups; but in the group receiving amikacin/teicoplanin, we observed between days 3 and 8 an increase in the excretion of N-acetyl-beta-D- glucosaminidase when compared to the group receiving amikacin/vancomycin (p < or = 0.05) and to the control group (p < or = 0.01).

Cu(2+)-induced lipid oxidation in plasma: questionable relation between cholesterol oxidation and LDL modification

Oxidatively modified low-density lipoproteins (LDL) may be involved in the process of cholesterol deposition in arteries. Because of their cytotoxicity, oxysterols resulting from cholesterol oxidation could be a contributing factor in this process. Studies in this area have generally been performed on purified LDL, but in our research whole plasma was exposed to the oxidizing action of copper. Oxidation of the ring structure, which is at the origin of oxysterols, apparently occurs once most polyunsaturated fatty acids have disappeared. Hydrated LDL density reaches a value identical to that obtained during oxidation of LDL by endothelial cells, whereas the ring structure remains unmodified.

Chrononephrotoxicity in Rat of a Vancomycin and Gentamicin Combination

The effect of time of administration on excretion of two brush border enzymes--alanine aminopeptidase (AAP) and gamma-glutamyl transferase (gamma GT), and a lysosomal enzyme, N-acetyl-beta-D-glucosaminidase (NAG) with a single high dose of vancomycin, gentamicin or a combination of vancomycin and gentamicin was studied in male Wistar rats and compared with elimination of a control group. The rats received vancomycin intraperitoneally (200 mg.kg-1), gentamicin intramuscularly (100 mg.kg-1) or the combination of the drugs by the same route. A control group received isotonic NaCl solution. The four groups of animals received a single injection at 8 a.m., 2 p.m., 8 p.m., and 2 a.m. and urine excretion values for AAP, gamma GT and NAG were determined 24 hr later. The results show that the nephrotoxicity of gentamicin + vancomycin is greater than that observed with gentamicin, which again is greater than that observed with vancomycin. Furthermore, circadian variations in renal toxicity were observed, the least occurring at 8 a.m.

Rapid high-performance liquid chromatographic assay of chlorophacinone in human serum

A simple procedure for the determination of chlorophacinone in human serum by high-performance liquid chromatography is reported. After addition of a suitable internal standard, unknown samples were extracted at acid pH with ethyl acetate. The reconstituted methanolic extract was directly injected into the liquid chromatograph. Separation was performed with a Lichrospher C18 5-microns column with a methanol-phosphate buffer (85:15, v/v) mobile phase. The eluent was monitored with UV detection at 286 nm. The method was found to be sufficiently rapid, reproducible, selective, and sensitive for use in clinical and experimental pharmacokinetic studies. Application of this method to 20 intoxicated patients indicated that the risk of bleeding syndrome, which is always associated with this kind of intoxication, is no longer present when chlorophacinone levels drop to below 1 microgram/mL.

[Circadian variations in the nephrotoxicity of the vancomycin-gentamicin combination in rats]

Male Wistar rats were used to evaluate the influence of time of administration of a single high dose of vancomycin (V), gentamicin (G) or vancomycin-gentamicin combination (V/G) on excretion of a brush border enzyme, alanine aminopeptidase (AAP) and of a lysosomal enzyme, N-acetyl-beta-D-glucosaminidase (NAG). Increased urinary excretion is considered as an early manifestation of renal toxicity. The rats were placed in temperature-controlled quarters with intermittent lighting (12 hours light/12 hours dark). V was given intraperitoneally in a dose of 200 mg/kg, G was given intramuscularly in a dose of 100 mg/kg, and the V/G combination was given in the same doses and by the same routes as each drug alone. A control batch of rats received an intraperitoneal injection of saline. In the four batches, the injection was given at 8 am, 2 pm, 8 pm and 2 am. Substantial brush border toxicity was found. Toxicity of G was greatest at 2 pm and lowest at 2 am, whereas for V, toxicity was greatest at 2 am and lowest at 2 pm. With the V/G combination, brush border toxicity was greatest at 2 am and lowest at 8 am. Lysosomal toxicity was no significant after administration of V or G. In contrast, the V/G combination induced very significant lysosomal toxicity which was greatest at 2 pm and smallest at 8 am. These results show that circadian variations in renal toxicity occur not only with V and G alone but also with the V/G combination.

Aluminum transfer as glutamate complex through blood-brain barrier. Possible implication in dialysis encephalopathy

In vitro distribution of aluminium between plasma and erythrocytes has been studied in the presence of variable amounts of sodium L-glutamate. With a red blood cell suspension in isotonic sodium chloride, aluminium remains confined in erythrocytes even when the sodium L-glutamate concentration increases in the medium. Aluminium initially present in plasma penetrates red blood cells when sodium L-glutamate increases in whole blood, showing that this metal is able in vitro to cross the erythrocyte membrane as glutamate complex. In vivo experiments with male Wistar rats prove that aluminium is also able to pass the blood--brain barrier as glutamate complex and deposit in the brain cortex.

Seasonal effects on the daily variations of gentamicin-induced nephrotoxicity

The effect on kidney damage of the season of year at which gentamicin was administered to rats was studied. Rats received a single intramuscular dose of 200 mg/kg gentamicin at four different times of the day (08.00, 14.00, 20.00 or 02.00 hours. Studies were carried out in January-February, March-April, June-July and October-November. The nephrotoxicity was assessed by the increase of three urinary enzymes: two brush border enzymes, gamma-glutamyl transferase and alanine aminopeptidase, and a lysosomal enzyme: N-acetyl-beta-D-glucosaminidase. The results show that when the injection is administered at 20.00 hours in the January-February and the October-November studies and at 08.00 hours in the March-April study and at 14.00 hours in the June-July study there is a significant increase in the excretion of these enzymes. The renal toxicity of gentamicin therefore has circadian variations as well as seasonal variations. The peak enzyme level is displaced from the start to the end of the rest period of rats depending upon the time of year.

Polyunsaturated fatty acid profiles and alpha-tocopherol levels in plasma and whole blood incubated with copper. Evidence of inhibition of lipoperoxidation in plasma by hemolysate

Polyunsaturated fatty acid (PUFA) profiles and alpha-tocopherol levels were studied in human plasma and whole blood incubated with copper under air or nitrogen. In plasma, both PUFAs and alpha-tocopherol disappeared. The results were completely different in whole blood: (i) in plasma, while alpha-tocopherol decreased in the same manner as in plasma incubated alone, profiles of PUFA were only slightly modified. So, in spite of the absence of alpha-tocopherol, lipoperoxidation was not very marked. That is why the release of a protective factor from erythrocytes during hemolysis was under consideration. This was confirmed by the complete inhibition of degradation of PUFAs in plasma when hemolysate was added; (ii) In erythrocytes, no modification in PUFA profiles could be detected while alpha-tocopherol decreased slightly. Thus, not only do erythrocytes resist the copper-dependent oxidative stress in an incredible manner, but they also seem to protect plasma at the time of hemolysis.