<Emphasis Type="Italic">Trichomonas vaginalis</Emphasis>: cytochemical localization of a NTPDase1 and an ecto-5′-nucleotidase and effects of adenine nucleotides on cellular viability

Nucleoside triphosphate diphosphohydrolase 1 (NTPDase1), which hydrolyzes extracellular ATP and ADP, and ecto-5-nucleotidase, which hydrolyzes AMP, are characterized for Trichomonas vaginalis. Ultrastructural cytochemical microscopy showed NTPDase1 and ecto-5-nucleotidase activities on the surface of the parasites. High levels of extracellular adenine nucleotides and adenosine did not exert cytolytic effects in intact cells of T. vaginalis. Our results suggest that these enzymes are relevant for the survival of the parasite during exposure to extracellular nucleotides. Since the ecto-localization of these enzymes is essential for the maintenance of adenosine extracellular levels, this nucleoside could be important for the purine salvage pathway in the parasite.     

The cortical stab injury induces beading of fibers expressing ecto-nucleoside triphosphate diphosphohydrolase 3

The ecto-nucleoside triphosphate diphosphohydrolase 3 (NTPDase3), an enzyme involved in degradation of extracellular adenosine triphosphate (ATP), is expressed on nerve fibers in different brain regions, including cortex. Here we studied the expression and role of this enzyme after unilateral cortical stab injury in rats. In cortical sections of control rats, NTPDase3 immunoreactivity was associated with two types of fibers: thin processes, occasionally with small mushroom-like protrusions and slightly thicker fibers with more pronounced and more frequent varicosities, whereas immunopositive neuronal perycaria were never observed. Although NTPDase3–positive thin processes and thicker fibers, by general appearance, size and shape, could be dendrites and axons, respectively, they were never immunopositive for microtubule associated protein-2 or neurofilament H subunit. Cortical stab injury induced rapid (within 4 hours) focal varicose swelling that evolved over time to prominent beading of NTPDase3–positive fibers. The NTPDase3–positive fibers in all experimental groups also abundantly express NTPDase1, ecto-5′-nucleotidase and P2X2 receptor channels. Because the brain injury causes a massive ATP release, it is reasonable to conclude that purinoreceptors and ectonucleotidases play an important role in the process of neuritic beading.     

Peroxynitrite treatment reduces adenosine uptake via the equilibrative nucleoside transporter in rat astrocytes

In the oxidative stress-loaded brain, extracellular adenosine levels are elevated and thereby neuronal damage is attenuated, but mechanisms underlying alteration of the extracellular kinetics of adenosine remain unclear. Here we investigated whether oxidative stress might alter functional expression of nucleoside transporters (NTs), a predominant regulatory system for nucleoside kinetics, in cultured rat astrocytes. Treatment of astrocytes with 0.5 mM SIN-1 for 3 h caused apparent cellular accumulation of nitrotyrosine, but had no effect on their viability, indicating load of oxidative stress to astrocytes without any change in their viability. Under the condition, [³H]adenosine uptake was significantly less than that by control cells. This decreased uptake was due to decrease in adenosine uptake mediated by an equilibrative NT (ENT) 1 which was inhibited by low concentrations (≤0.1 μM) of nitrobenzylthioinosine (NBMPR), but not by sodium-dependent or high concentrations (≥1 μM) of NBMPR-inhibitable nucleoside transporters. The expression level of ENT1 was not altered, while the Michaelis constant, but not the maximum rate, of adenosine uptake was increased. These findings suggest that under oxidative stress-loaded conditions, decreased adenosine clearance via astrocytic ENT1 might involve, at least in part, in an elevated extracellular adenosine level in the brain.     

Adenosine and adenine nucleotides are independently released from both the nerve terminals and the muscle fibres upon electrical stimulation of the innervated skeletal muscle of the frog

The independent release of adenosine and adenine nucleotides upon electrical stimulation was studied in the innervated sartorius muscle of the frog after blockade of the extracellular catabolism of adenosine monophosphate (AMP) through exo-AMP deaminase and ecto-5-nucleotidase. Nerve stimulation (30 min, 0.2Hz) induced the release of both adenosine (19±3 pmol) and adenine nucleotides (101±7 pmol). Experiments performed in the presence of tubocurarine (5 M) to prevent purine release due to nerve-evoked muscle twitching, or under direct stimulation of the muscle in low calcium solutions to prevent pre-synaptic release of purines, showed that there was an evoked release of adenosine and adenine nucleotides both from the nerve endings and from the twitching muscle fibres. Removal of ecto-5-nucleotidase inhibition shows that the catabolism of adenine nucleotides released during stimulation contributes in about 50% to the amount of endogenous extracellular adenosine. When only one of the enzymes catabolizing AMP (ecto-5-nucleotidase or exo-AMP deaminase) was inhibited, the evoked release of adenine nucleotides was undetectable, suggesting that each enzyme is able to catabolize all the AMP formed from adenine nucleotides released upon stimulation. It is concluded that the concentration of endogenous extracellular adenosine is under the control of the relative activities of exo-AMP deaminase and ecto-5-nucleotidase.Brief accounts of some of the results in this study have been published previously (refs. [6, 7]).     

Differential hippocampal pharmacokinetics of phenobarbital and carbamazepine in repetitive seizures induced by 3-mercaptopropionic acid

Previous evidence has shown that chronic 3-mercaptopropionic acid (MP) administration induced brain P-glycoprotein (P-gp) overexpression altering target site accumulation of phenytoin. The aim of the present work was to assess the involvement of P-glycoprotein in carbamazepine and phenobarbital hippocampal pharmacokinetics in an experimental model of epilepsy, induced by repetitive MP administration. Seizures were induced in Wistar rats by injection of MP (45 mg kg⁻¹, i.p.) during 10 days. Control rats (C) were injected with saline solution. In order to monitor extracellular brain antiepileptic levels, a concentric probe was inserted into the hippocampus. Animals were administered with carbamazepine (10 mg kg⁻¹, i.v.) or phenobarbital (20 mg kg⁻¹, i.v.) 30 min after intraperitoneal administration of vehicle or nimodipine (2 mg kg⁻¹), a well known P-glycoprotein inhibitor. No differences were found in hippocampal concentrations of carbamazepine comparing all groups. In vehicle pre-treated rats, hippocampal phenobarbital concentrations were lower in MP (maximal concentration, C_max: 6.0 ± 0.6 μg ml⁻¹, p < 0.05) than in C animals (C_max: 9.4 ± 0.9 μg ml⁻¹). Control rats pre-treated with nimodipine showed similar results (C_max: 10.7 ± 0.6 μg ml⁻¹) than those pre-treated with vehicle. Nimodipine pre-treatment in MP rats enhanced hippocampal phenobarbital concentrations (C_max: 10.2 ± 1.0 μg ml⁻¹, p < 0.05) as compared with vehicle pre-treatment.     

Allergen-induced airway hyperresponsiveness is absent in ecto-5′-nucleotidase (CD73)-deficient mice

Adenosine is formed from extracellular purines by ecto-5′-nucleotidase (CD73) and is an essential player in allergic airway inflammation. The contribution of adenosine and other purines to electrolyte transport and mucociliary clearance was studied in airways of allergen challenged mice. No signs for allergen-induced inflammation were found in CD73−/− mice, and adenosine monophosphate (AMP) was unable to elicit airway Cl⁻ secretion in these animals. Tracheas of ovalbumin (OVA)-treated BALB/c and CD73+/+ mice were hyperresponsive towards methacholine when assessed by Penh and direct optical measurement of contraction. In addition Cl⁻ secretion activated by ATP and ADP was enhanced. These changes were not observed in CD73−/− mice. Expression of CFTR or CLCA was unchanged upon OVA treatment of CD73 mice, suggesting enhanced Cl⁻ secretion due to upregulated purinergic pathways. Mucociliary clearance was determined by measuring particle transport in excised mouse tracheas and was strongly enhanced in OVA-challenged CD73+/+ mice, but remained unchanged in CD73−/− mice. While mucociliary clearance is activated by allergen exposure independent of functional ecto-5′-nucleotidase, airway inflammation is largely dependent on CD73. Thus, ecto-5′-nucleotidase may provide a novel target for therapeutic intervention, probably by local application of ecto-5′-nucleotidase inhibitors through inhalation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Changes in sensory perception of sports drinks when consumed pre, during and post exercise

The aim of this study was to examine sensory perceptions towards different formulations of sports drinks when consumed before, at various points during, and following exercise. Following familiarisation 14 recreational runners underwent four trials in a single blind counterbalanced design. Each trial utilised one of four different solutions: 7.5% carbohydrate, 421 mg L^− 1 electrolyte (HiC-HiE); 7.5% carbohydrate, 140 mg L^− 1 electrolyte (HiC-LoE); 1.3% carbohydrate, 421 mg L^− 1 electrolyte (LoC-HiE) and water. Subjects were provided with 50-ml samples to ingest and then rate (using a 100-mm line scale) the intensity of sweetness, saltiness, thirst-quenching ability and overall liking before (− 30 min), during (0, 30 and 60 min) and following (90 and 120 min) treadmill running exercise. Ratings of sweetness for all energy-containing drinks were higher during exercise relative to pre- and post-exercise conditions (P < 0.05); ratings also increased with duration of exercise (P < 0.001). Sweetness ratings for LoC-HiE increased during exercise (P < 0.05) but remained the same for other beverages. Ratings of saltiness decreased for all energy-containing drinks during exercise relative to pre-exercise (P < 0.05); ratings decreased with duration of exercise in these drinks (P < 0.05). Ratings of thirst-quenching ability (P = 0.039) and overall liking (P = 0.013) increased with duration of exercise with all beverages. Significant changes in sensory perception occur when consuming sports drinks during exercise relative to non-exercise conditions. Temporal changes also occur during exercise itself which leads to enhanced liking of all beverages.     

Intracerebroventricular injection of human prostatic acid phosphatase has potent neuroprotective effects against transient focal cerebral ischemia in rats

Though the potential use of adenosine as a neuroprotective agent has long been realized, there are currently no adenosine-based therapies for the prevention or treatment of cerebral ischemia and reperfusion injury. Prostatic acid phosphatase (PAP), an enzyme that has long served as a diagnostic marker for prostate cancer, has been recently demonstrated to exhibit ecto-5′-nucleotidase activity, and dephosphorylate endogenous extracellular AMP to adenosine. We therefore tested the hypothesis that PAP has sustained and potent neuroprotective effects against cerebral ischemia in the rat model of middle cerebral artery occlusion. We found that hPAP produced significant neuroprotection against focal cerebral ischemia, as evident from significant reduction in cerebral infarction and neurological deficits. The therapeutic time window for hPAP in rat focal cerebral ischemia model was limited from 6 h before ischemia to 1.5 h after reperfusion. The present study suggested that PAP is a potential candidate for the prevention and treatment of cerebral ischemic injury, especially during perioperative period.     

NO and cGMP facilitate adenosine production in rat hearts via activation of ecto-5′-nucleotidase

 We examined whether nitric oxide (NO), a possible cardioprotective substance, can increase the production of interstitial adenosine in the ventricular myocardium. A flexibly mounted microdialysis technique was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5′-nucleotidase in in vivo rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5′-monophosphate (AMP) at a rate of 1.0 μl min^–1. The concentration of adenosine in the effluent (dialysate) was measured by high-performance liquid chromatography. Dialysate adenosine obtained during perfusion with the AMP-containing solution through the probe originated from the hydrolysis of AMP by endogenous ecto-5′-nucleotidase, and the level of adenosine reflected the activity of ecto-5′-nucleotidase in the tissue. S-Nitroso-N-acetylpenicillamine (SNAP, 0.3–3 mM), an NO donor, increased the dialysate adenosine measured in the presence of AMP (100 μM) in a concentration-dependent manner. However, in the presence of an NO-oxidizing agent, 2-(4-carboxyphenyl-4,4,5,5-tetramethylimidazoline)-1-oxyl 3-oxide (carboxy-PTIO, 1 mM), the effect of SNAP was abolished. Another NO donor, (±)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (FK409, 1 mM) also increased adenosine production. 8-Bromo-cGMP (0.1–3 mM), a membrane-permeable cGMP analogue and a potent activator of cGMP-dependent protein kinase, increased the level of AMP-primed dialysate adenosine in a concentration-dependent manner. These results suggest that NO facilitates the production of interstitial adenosine in rat hearts in situ, via cGMP-mediated activation of ecto-5′-nucleotidase. Received: 20 February 1998 / Received after revision and accepted: 9 July 1998     

Enzymes of purine metabolism in lymphoid neoplasms,clinical relevance for treatment with enzyme inhibitors

Summary A few enzymes of the purine degradative pathway have proved valuable in diagnosis and treatment of lymphomas and lymphocytic leukemia. Of particular interest are the enzymes adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and ecto-5-nucleotidase (5NT). Intact activities of ADA and PNP have been shown to be vital for lymphoid cells. During development, lymphoid precursors go through remarkable changes in the concentrations of these enzymes and the neoplasma derived from them show a frozen biochemical profile similar to the corresponding normal cell of origin. Knowledge of the role of these enzymes has led to the pharmacological use of enzyme inhibitors for the specific treatment of lymphoid neoplasms. This review concerns the enzymatic make-up of normal and neoplastic lymphocytes and exploitation of this knowledge for the treatment of lymphomas. Special emphasis will be put on the clinical use of an ADA-inhibitor, deoxycoformycin.Abbreviations ADA Adenosine deaminase - ALL Acutelymphocytic leukemia - CdA 2-Chloradeoxyadenosine - CLL Chronic lymphocytic leukemia - dATP Deoxyadenosine triphosphate - dCTP Deoxycytidine triphosphate - dGTP Deoxyguanosine triphosphate - 5NT Ecto-5-nucleotidase - PNP Purine nucleoside phosphorylase - SAH S-adenosylhomocysteine - SAM S-adenosyl-methionine - SCID Severe combined immunodeficiency disease Dedicated to Professor Werner Hunstein on the occasion of his 60th birthday     

Enzymatic and extraenzymatic role of ecto-adenosine deaminase in lymphocytes

Summary: Adenosine deaminase (ADA, EC 3.5.4.4) is an enzyme of the purine metabolism which has been the object of considerable interest mainly because the congenital defect causes severe combined immunodeficiency (SCID). In the last 10 years, ADA, which was considered to be cytosolic, has been found on the cell surface of many ceils and, therefore, it can be considered an ecto-enzyme. There is recent evidence about a specific role of ecto-ADA, which is different from bat of intracellular ADA. Apart from degrading extracellular adenosine (Ado) or 2'-deoxyadenosLne (dAdo), which are toxic for lymphocytes, ecto-ADA has an extraenzymatic function via its interaction with GD26. ADA/CD26 interaction results in co-stimulatory signals in T cells. This co-stimulation is blocked by HIV-1, thus evidencing a role for ecto-ADA in the pathophysiology of AIDS. The fact that, besides CD26, ADA can interact with different cell-surface proteins opens new perspectives in the research for a role of ecto-ADA in the function of the immune system and in the Interactions that take place between different cells in the development of the immune system. The most interesting aspect is the possible participation of the ecto-enzyme in cell-to-cell contacts during ontogenesis and maturation of immunocompetent cells.     

Pharmacocinétique du linézolide chez des patients souffrant de brûlures sévères

The aims of this multicentre open-label study was to evaluate the pharmacokinetics of linezolid in patients with burn injury above 20 % BSA and to compare them with healthy volunteers, matched in age, sex and weight. After a single 600 mg IV dose of linezolid, multiple blood and urine samples were taken from subjects, in order to determine linezolid concentrations, using a HPLC assay. C_max and volume of distribution at steady state were not different between the two groups. Values describing clearance were altered in burns, leading to a reduction by half in AUC in these patients (42,5 versus 98,1 mg h L⁻¹). The enhancement of clearance was due to which of non renal clearance (323 ± 191 versus 80,4 ± 27,5 mL min⁻¹). We conclude that pharmacokinetics of linezolid are altered in burn patients, in a magnitude sufficient that linezolid concentration may be subtherapeutic in some patients and we suggest that the dosage interval may need to be decreased in this patient population.     

The ectonucleotidases alkaline phosphatase and nucleoside triphosphate diphosphohydrolase 2 are associated with subsets of progenitor cell populations in the mouse embryonic, postnatal and adult neurogenic zones

Subventricular zone (SVZ)–derived adult neurospheres express two ectonucleotidases, nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) and tissue non-specific alkaline phosphatase (TNAP). Agonists of the nucleotide receptors P2Y₁ and P2Y₂ as well as adenosine augment growth factor–mediated progenitor cell proliferation. NTPDase2 converts ATP and UTP to ADP and UDP, respectively, which are all P2Y receptor agonists. TNAP hydrolyzes nucleoside triphosphates and diphosphates and produces the P1 receptor agonist adenosine. In the SVZ, NTPDase2 is specifically expressed by type B cells. In order to further scrutinize the association of key molecules of the purinergic signaling pathway with neurogenic regions, we analyzed the expression of TNAP at the lateral ventricles of the adult and developing mouse brain. In the adult brain, TNAP was expressed by type B, type A and at least subsets of type C cells of the SVZ and throughout the rostral migratory stream. Almost 100% of the proliferating, Ki-67-positive cells of the adult SVZ stained for TNAP, supporting the notion of a ubiquitous association of TNAP with SVZ progenitors. In contrast, NTPDase2-positive progenitors of the dentate gyrus were TNAP-negative. Essentially all cells of the telencephalic vesicle at embryonic day (E) 14 revealed TNAP activity, including doublecortin-positive neuroblasts. During further embryonic development, enhanced TNAP activity became restricted to cells of the ventricular and SVZ. In contrast to TNAP, NTPDase2 was first expressed in the SVZ perinatally, in association with TNAP-positive SVZ border cells. During later development, NTPDase2-positive cells disappeared from the ventricular surface and began to form sheaths around clusters of subventricular doublecortin-positive cells, apparently transforming into type B cells. Our results identify TNAP and NTPDase2 as novel markers for subsets of progenitors in the adult and developing mouse brain. They further support the notion that signaling via extracellular nucleotides and nucleosides contributes to embryonic and adult neurogenesis.     

Protective effects of coumarin and coumarin derivatives against carbon tetrachloride-induced acute hepatotoxicity in rats

The comparison of the antioxidant activity of some coumarins with their molecular structure is well determined. However, the protective function of coumarins with various chemical structures against liver toxicity has not yet been well established. Therefore, the aim of this study was to evaluate the possible cytoprotective properties of coumarin and some coumarin derivatives against CCl₄ (carbon tetrachloride)-induced hepatotoxicity. Coumarin (1,2-benzopyrone) and coumarin derivatives esculetin (6,7-dihydroxycoumarin), scoparone (6,7-dimethoxycoumarin) and 4-methylumbelliferone (7-hyroxy-4-methyl) were examined for their protective effect against CCl₄-induced hepatotoxicity in Male Sprague-Dawley rats. A single toxic dose of CCl₄ (1.25 ml kg⁻¹, orally) produced liver damage in rats, seen histologically as centrilobular necrosis. Administration of CCl₄ increased serum enzyme levels of aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP). Pre-treatment of rats with esculetin (31.15 mg kg⁻¹, orally) and scoparone (35 mg kg⁻¹, orally) significantly prevented CCl₄-induced increase in serum enzymes, whereas 4-methylumbelliferone (35 mg kg⁻¹) and coumarin (30 mg kg⁻¹) had no effect against CCl₄-induced rise in serum enzymes. Morphological findings were consistent with the plasma transaminase observations. Among the coumarin analogs, esculetin, which possesses orthodihydroxy coumarins, showed the strongest protective effect against CCl₄-induced liver damage, followed by scoparone, 4-methylumbelliferone and coumarin, respectively. The results of this study indicate that the chemical structures of coumarins play an important role in the prevention of liver toxicity.     

BIOCHEMISTRY, LOCALIZATION AND FUNCTIONAL ROLES OF ECTO-NUCLEOTIDASES IN THE NERVOUS SYSTEM

Nucleotides such as ATP, ADP, UTP or the diadenosine polyphosphates and possibly even NAD⁺ are extracellular signaling substances in the brain and in other tissues. Enzymes located on the cell surface catalyze the hydrolysis of these compounds and thus limit their spatio-temporal activity. As a final hydrolysis product they generate the nucleoside and phosphate. The paper discusses the biochemical properties, cellular localization and functional properties of surface-located enzymes that hydrolyse nucleotides released from nervous tissue. This is preceded by a brief discussion of nucleotide receptors, cellular storage and mechanisms of nucleotide release. In nervous tissue nucleoside 5′-triphosphates are hydrolysed by ecto-ATP-diphosphohydrolase and possibly in addition also by ecto-nucleoside triphosphatase and ecto-nucleoside diphosphatase. The molecular identity of the ATP-diphosphohydrolase has now been revealed. The hydrolysis of nucleoside 5′-monophosphates is catalysed by 5′-nucleotidase whose biochemical properties and molecular structure have been studied in detail. Little is known about the molecular properties of the diadenosine polyphosphatases. Surface located enzymes for the extracellular hydrolysis of NAD⁺ and also ecto-protein kinases are discussed briefly. The cellular localization of the ecto-nucleotidases is only partly defined. Whereas in adult mammalian brain activity for hydrolysis of ATP and ADP may be associated with nerve cells or glial cells 5′-nucleotidase appears to have a preferential glial allocation in the adult mammal. The extracellular hydrolysis of the nucleotides is of functional importance not only during synaptic transmission where it functions in signal elimination. It plays a crucial role also for the survival and differentiation of neural cells in vitro and presumably during neuronal development in vivo. Copyright © 1996 Elsevier Science Ltd.     

Neuroprotective effect of 20(R)-ginsenoside Rg3 against transient focal cerebral ischemia in rats

Gensenosides, the active ingredients of Chinese herbal medicine Panax ginseng, have a wide spectrum of medical effects, such as anti-tumorigenic, angiosuppressive, adaptogenic, and anti-fatigue activities. In the present study, we have investigated the neuroprotective effect of 20(R)-ginsenoside Rg₃ (20(R)-Rg₃) against transient focal cerebral ischemia in male Sprague-Dawley (SD) rats. The middle cerebral artery was occluded for 2 h in rats and then reperfused for 24 h. The behavioral disturbance was evaluated according to neurological deficit scores, and the infarct volumes were evaluated by 2,3,5-triphenyltetrazolium chloride (TTC) staining; in addition, ischemia-mediated apoptosis was examined using the method of terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP nick end labeling (TUNEL). The expressions of calpain I and caspase-3 mRNA in hippocampal CA1 region were further assayed using in situ hybridization, in order to clarify the neuroprotective mechanism of 20(R)-Rg₃. 20(R)-Rg₃ at the doses of 10 and 20 mg kg⁻¹ i.p., but not 5 mg kg⁻¹, showed significant neuroprotective effect in rats against focal cerebral ischemic injury by markedly reducing cerebral infarct volumes and degrading infarct rate of TTC-stained coronal brain sections, and improving behavior of the animals. Our results also suggested that 20(R)-Rg₃ (10 and 20 mg kg⁻¹) could significantly suppress the expressions of calpain I and caspase-3 mRNA. These results indicated that 20(R)-Rg₃ attenuates the neuronal apoptosis caused by cerebral ischemia–reperfusion injury and its neuprotective effect may be involved in the downregulation of calpain I and caspase-3.     

Taurine prevents enhancement of acetylcholinesterase activity induced by acute ethanol exposure and decreases the level of markers of oxidative stress in zebrafish brain

Ethanol (EtOH) is a drug widely consumed throughout the world that promotes several neurochemical disorders. Its deleterious effects are generally associated with modifications in oxidative stress parameters, signaling transduction pathways, and neurotransmitter systems, leading to distinct behavioral changes. Taurine (2-aminoethanesulfonic acid) is a β-amino acid not incorporated into proteins found in mM range in the central nervous system (CNS). The actions of taurine as an inhibitory neurotransmitter, neuromodulator, and antioxidant make it attractive for studying a potential protective role against EtOH-mediated neurotoxicity. In this study, we investigated whether acute taurine cotreatment or pretreatment (1 h) prevent EtOH-induced changes in acetylcholinesterase (AChE) activity and in oxidative stress parameters in zebrafish brain. The results showed that EtOH exposure (1% in volume) during 1 h increased AChE activity, whereas the cotreatment with 400 mg·L(-1) taurine prevented this enhancement. A similar protective effect of 150 and 400 mg·L(-1) taurine was also observed when the animals were pretreated with this amino acid. Taurine treatments also prevented the alterations promoted in superoxide dismutase and catalase activities by EtOH, suggesting a modulatory role in enzymatic antioxidant defenses. The pretreatment with 150 and 400 mg·L(-1) taurine significantly increased the sulfydryl levels as compared to control and EtOH groups. Moreover, 150 and 400 mg·L(-1) taurine significantly decreased thiobarbituric acid reactive species (TBARS) levels, but the cotreatment with EtOH plus 400 mg·L(-1) taurine did not prevent the EtOH-induced lipoperoxidation. In contrast, the pretreatment with 150 and 400 mg·L(-1) taurine prevented the TBARS increase besides decreased the basal levels of lipid peroxides. Altogether, our data showed for the first time that EtOH induced oxidative stress in adult zebrafish brain and reinforce the idea that this vertebrate is an attractive alternative model to evaluate the beneficial effect of taurine against acute EtOH exposure.     

Urethane inhibits genioglossal long-term facilitation in un-paralyzed anesthetized rats

For ∼3 decades, urethane has been (partially or solely) used as a successful anesthetic in numerous respiratory long-term facilitation (LTF) studies, which were performed on anesthetized, paralyzed, vagotomized and artificially ventilated animals of several different species. However, things become complicated when LTF of muscle activity is studied in un-paralyzed animals. For example, a commonly used acute intermittent hypoxia (AIH) protocol failed to induce muscle LTF in anesthetized, spontaneously breathing rats. But muscle LTF could be induced when hypoxic episode number was increased and/or anesthetics other than urethane were used. In these studies however, neither anesthetic nor paralysis was mentioned as a potential factor influencing AIH-induced muscle LTF. This study tested whether urethane inhibits AIH-induced genioglossal LTF (gLTF) in un-paralyzed ventilated rats, and if so, determined whether reducing urethane dose reverses this inhibition. Three groups of adult male Sprague–Dawley rats were anesthetized (Group 1: ∼1.6 g kg⁻¹ urethane; Group 2: 50 mg kg⁻¹ α-chloralose +0.9–1.2 g kg⁻¹ urethane; Group 3: 0.9 g kg⁻¹ urethane +200–400 μg kg⁻¹ min⁻¹ alphaxalone), vagotomized and mechanically ventilated. Integrated genioglossus activity was measured before, during and after AIH (5 episodes of 3-min isocapnic 12% O₂, separated by 3-min hyperoxic intervals). The AIH-induced gLTF was absent in Group 1 rats (success rate was only ∼1/7), but was present in Group 2 (in 10/12 rats) and Group 3 (in 11/11 rats) rats. The genioglossal response to hypoxia was not significantly different among the 3 groups. Collectively, these data suggest that urethane dose-dependently inhibits gLTF in un-paralyzed anesthetized rats.