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J C Leza

Publications and source records attributed to J C Leza.

At least 37 records · Page 2Linked to original sources
PubMed1999

Nitric oxide synthase activity in human squamous cell carcinoma of the head and neck.

OBJECTIVES: To test whether nitric oxide synthase (NOS) is expressed in primary otolaryngologic tumors and whether this expression is associated with the degree of malignancy. STUDY DESIGN: Twenty-six samples from the primary localization of human pharyngolaryngeal squamous cell carcinoma. MATERIALS AND METHODS: the activity of calcium-dependent and calcium-independent NOS was analyzed by the conversion of L-[14C]-arginine into L-[14C]-citrulline. RESULTS: NOS activity is below detectable levels in pharyngolaryngeal mucosa from noncancer patients. In the primary localization of the tumor, calcium-independent NOS activity is maximal at early stages of tumor growth, whereas calcium-dependent activity increases from early to advanced stages. CONCLUSIONS: These data suggest that tumor growth and malignancy is associated with a change in the enzymatic source of NO from calcium-independent NOS to calcium-dependent NOS isoform in primary localization. These data suggest that the inhibition of calcium-independent NOS activity in early stages and/or inhibition of calcium-dependent NOS activity in later stages could delay growth of solid tumors.

Adult↗
PubMed1998

Neuronal and inducible nitric oxide synthase and nitrotyrosine immunoreactivities in the cerebral cortex of the aging rat.

Neuronal and inducible nitric oxide synthase (nNOS and iNOS) and nitrotyrosine immunoreactivities were localized and semiquantitatively assessed in the cerebral cortex of aged rats by means of light microscopic immunocytochemistry and Western blotting, using a new series of specific polyclonal antibodies. In the aged rats the strongly nNOS-immunoreactive multipolar neurons found in layers II-VI of the cortex of young rats were seen in similar numbers, but showed varicose, vacuolated, and fragmented processes, with an irregular outline and loss of spines. A large number of more weakly nNOS-positive neurons, characterized by a ring of immunoreactive cytoplasm, and not seen in young rats, were observed in layers II-VI of aged rat cortex. While no iNOS-immunopositive neurons were found in the cortex of young rats, a large number of such neurons appeared throughout the aged rat cortex. Nitrotyrosine-positive cells outnumbered total NOS-positive neurons in the cortex of young rats, but this relation was inverted in the aged rats, although these showed a slight increase in the number and staining intensity of nitrotyrosine-positive cells. Western blots of brain extracts showed a several-fold increase in both nNOS- and iNOS-immunoreactive bands in the aged rat, but a less marked increase in nitrotyrosine-containing proteins. The results suggest that while nNOS and iNOS expression is substantially increased in the aged rat cortex, this is not necessarily accompanied by a proportionate increase in nitric oxide synthesis. The mechanisms underlying the increased expression of nNOS and iNOS, and the functional implications of this increase, require elucidation.

Aging↗
PubMed1998

Protective effect of N-(3-(aminomethyl)benzyl) acetamidine, an inducible nitric oxide synthase inhibitor, in brain slices exposed to oxygen-glucose deprivation.

It has been suggested that large amounts of nitric oxide (NO) produced by inducible NO synthase are involved in the mechanisms of neurotoxicity after cerebral ischaemia. We have recently demonstrated that inducible NO synthase was expressed within hours after rat forebrain slices were exposed to oxygen-glucose deprivation. Therefore, we sought to determine whether NO produced by inducible NO synthase contributes to tissue damage in this model, by using a new, highly selective, inhibitor of inducible NO synthase, N-(3-(aminomethyl)benzyl)acetamidine (1400W). We found that incubation with 1400W from the start of the oxygen-glucose deprivation period until the end of the experiment decreases tissue damage determined as lactate dehydrogenase (LDH) efflux 4 h after the oxygen-glucose deprivation period, the time at which inducible NO synthase expression is maximal in this model. This effect may be a result of direct inhibition of inducible NO synthase activity, raising the possibility of a clinical use of selective inhibitors of this NO synthase isoform in the management of cerebral ischaemia.

Amidines↗
PubMed1998

Neuronal death induced by SIN-1 in the presence of superoxide dismutase: protection by cyclic GMP.

The nitrovasodilator 3-morpholinosydnonimine (SIN-1) slowly decomposes to release both nitric oxide (NO) and superoxide (O2-) and thereby produces peroxynitrite (ONOO-), a powerful oxidant which has been proposed to mediate the toxic actions caused by NO. Indeed, ONOO has been shown to cause neuronal death and it has been proposed to occur in different disorders of the CNS such as brain ischaemia, AIDS-associated dementia, amyothrophic lateral sclerosis, etc. We have found that SIN-1 was only slightly toxic to 1-week-old rat cortical neurones in primary culture (LC50=2.5+/-0.5 mM). Superoxide dismutase (SOD; 100 U/ml) significantly increased SIN-1-induced toxicity, an effect that was enhanced in the presence of HbO2, abolished by catalase and accompanied by the formation of hydrogen peroxide (H2O2). We have also found that 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ), a selective inhibitor of soluble guanylate cyclase, enhances cell death induced by SIN-1 (0.2-0.5 mM) + SOD (100 U/ml) in a concentration-dependent way (EC50=0.073+/-0.004 microM). Simultaneously, ODQ inhibits the elevation of cyclic GMP concentrations induced by SIN-1 + SOD in cortical cells (IC50=0.022+/-0.014 microM). Finally, we have also shown that the cyclic GMP mimetic, 8-bromo-cyclic GMP reverses the potentiating effect induced by ODQ on SIN-1 + SOD-induced neuronal death and inhibits the neurotoxicity induced by H2O2 (100 microM). Taken together, these data suggest that H2O2 is the species responsible for the potentiation by SOD of SIN-1-induced cell death and that cyclic GMP elevations confer selective cytoprotection against this H2O2-mediated component of cell death.

Animals↗
PubMed1998

Neuronal expression of inducible nitric oxide synthase after oxygen and glucose deprivation in rat forebrain slices.

Nitric oxide (NO) overproduction has been postulated to contribute significantly to ischaemia-reperfusion neurotoxicity. Inducible or type II NO synthase (iNOS) synthesizes NO in large quantities for long periods of time. Therefore we investigated the expression and localization of iNOS after oxygen and glucose deprivation in rat forebrain slices. In this experimental model, calcium-independent NOS activity reached a maximum 180 min after the end of a 20 min oxygen-glucose deprivation period. During the same period of time, the calcium-independent activity was absent in control forebrain slices. To test whether this calcium-independent NOS activity was due to the expression of iNOS, the effects of the addition of dexamethasone, cycloheximide and pyrrolidine dithiocarbamate were determined. All of them inhibited the induction of the calcium-independent NOS activity measured in the rat forebrain slices after oxygen and glucose deprivation. Furthermore, oxygen and glucose deprivation caused the expression of the gene encoding iNOS in rat forebrain slices, as assessed by the detection of iNOS message and protein in these samples. A sixfold increase in the iNOS mRNA levels was observed at 180 min and the time-course of the expression of iNOS mRNA was in agreement with the temporal profile of iNOS enzymatic activity. Immunohistochemistry analysis revealed that iNOS was highly expressed in neurones, astrocytes and microglial cells. These results demonstrate for the first time that iNOS is expressed in neurones after oxygen and glucose deprivation, and that this expression occurs in short periods of time. These findings suggest that NO can play an important pathogenic role in the tissue damage that occurs after cerebral ischaemia.

Animals↗
PubMed1998

Peroxynitrite causes aspartate release from dissociated rat cerebellar granule neurones.

Peroxynitrite (ONOO-) is a powerful oxidant which is formed from the reaction between nitric oxide (NO) and superoxide anion. It has therefore been proposed to mediate the toxic actions caused by NO. Since ONOO- may be formed in the central nervous system (CNS) in pathological conditions such as brain ischaemia, we decided to investigate whether this molecule induces the release of the endogenous excitatory amino acids glutamate and aspartate from neurones. We selected as biological model acutely dissociated rat cerebellar granule neurones in suspension to allow a direct interaction between ONOO- and target cells. Peroxynitrite caused a concentration-dependent release of aspartate but not of glutamate from dissociated cerebellar granule neurones. Peroxynitrite-induced aspartate release was inhibited by dithiothreitol, tetrodotoxin, and in Na+-deprived solutions and not affected by EGTA or pre-incubation with the cytosolic Ca2+ chelator BAPTA/AM. Peroxynitrite also induced an increase in intracellular Ca2+ concentration which was not affected in the presence of EGTA. These data show that ONOO- causes release of aspartate from cerebellar granule neurones and that this effect might arise from an alteration of Na+ membrane permeability leading subsequently to reversal of a Na+-dependent plasma membrane transporter of this excitatory amino acid. In addition, ONOO- alters Ca2+ homeostasis likely due to Na+ overload. Taken together, these findings may help and elucidate some of the intimate mechanisms of NO-induced neuronal damage in pathological circumstances.

Animals↗
PubMed1998

The effects of stress on homeostasis in JCR-LA-cp rats: the role of nitric oxide.

We have investigated the effects of early phases of chronic stress on generation and actions of nitric oxide (NO) in JCR:LA-cp rats both lean (+/+) and obese (cp/cp). Restraint stress was carried out for a 15-min single exposure or for 1 hr every day during 4, 9 or 14 days. The stress reaction was evidenced by significant increase in plasma cortisol. The exposure to stress for 14 days led to a neuronal damage in lean rats as evidenced by a decrease in glutamate uptake and an increase in the release of lactate in synaptosomes. This effect was not observed in obese rats. Concomitantly, the levels of glutamate increased in the hippocampus at 14 days in lean, but not obese rats, that showed higher basal levels of glutamate than lean rats. The activity of NO synthase (NOS) and guanosine cyclic monophosphate levels increased in the hippocampus preceding the neuronal damage. The neuronal lesions were prevented by inhibition of NOS without affecting cortisol levels. In the cardiovascular system, chronic stress exerted no significant effect on blood pressure, aortic contractility or platelet aggregation. However, there were significant changes in plasma nitrite/nitrate that reached maximum at 4 to 9 days. It is concluded that the generation of NO contributes to the systemic response to the organism to stress. In the brain, NO appears to be detrimental as this molecule mediates glutamate-dependent hippocampal damage, this effect being cortisol-independent. In contrast, in the vascular system, increased generation of NO may attenuate the vasoconstrictor and platelet aggregatory effects of catecholamines and other mediators of stress.

Animals↗
PubMed1996

Inhibition of morphine withdrawal by lamotrigine: involvement of nitric oxide.

We studied the effects of lamotrigine [3,5-diamino-6-(2,3-dichlorophenyl)- 1,2,4-triazine], a new antiepileptic compound, on naloxone-precipitated morphine withdrawal in mice. Pretreatment with lamotrigine (5-100 mg/kg, s.c.) reversed in a dose-dependent way the withdrawal-induced increase in cerebellar Ca(2+)-dependent nitric oxide (NO) synthase activity and reduced the number of escape jumps and other motor symptoms of abstinence, at doses that did not modify locomotor activity (25-50 mg/kg). Pretreatment with the NMDA receptor antagonist MK-801 [(+)-5-methyl-10,11-dihydroxy-5H- dibenzo[a,d]cyclohepten-5,10-imine; dizocilpine] (0.1-0.3 mg/kg, s.c.) also reversed the increase in cerebellar Ca(2+)-dependent NO synthase activity. However, although MK-801 reduced the number of escape jumps and other motor symptoms of abstinence, its effects were not clearly dose-dependent. Furthermore, the highest dose of MK-801 tested (0.3 mg/kg) caused an impairment of the locomotor behaviour in naive mice. Thus, lamotrigine may represent a new and useful agent for the treatment of opiate abstinence.

Animals↗
PubMed1996

Correlation between brain nitric oxide synthase activity and opiate withdrawal.

The opiate withdrawal induced by administration of naloxone to morphine-dependent mice correlates with an increment of calcium- dependent nitric oxide synthase (NOS) activity in the cerebellum. L-NAME, an irreversible competitive inhibitor of NOS (0.5, 5, 25, 50 mg/kg) injected sc. 45 min. prior to naloxone significantly reduced the number of escape jumps and other motor symptoms of abstinence. In addition, L-NAME also decreased NOS activity in cerebellum. L-arginine, but not D-arginine, when coadministered with L-NAME, prevented both the inhibition of NOS activity and the reduction of withdrawal symptoms induced by L-NAME in morphine-withdrawn animals. These results demonstrate a hyperactivity of the L-arginine: NO pathway in opiate withdrawal and suggests the possibility of a therapeutic use of NOS inhibitors in this state.

Animals↗
PubMed1996

Effects of trepelennamine on brain monoamine turnover in morphine dependent and abstinent mice.

Previous studies have reported that the histamine H1 receptor blocker tripelennamine potentiates morphine withdrawal. In this paper, the in vivo effects produced by tripelennamine on the turnover of serotonin (5-HT), dopamine (DA) and noradrenaline (NA) in the whole brain, excluding the cerebellum, were studied in control, morphine-dependent (by SC implantation of a 75 mg morphine pellet) and morphine-dependent male CD1 mice just before naloxone-precipitated withdrawal. Tripelennamine (1-10 mg/kg) was administered SC 45 min. before the animals were killed. Serotonin, 5-hydroxyindole-3-acetic acid (5-HIAA), dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and noradrenaline were measured by high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) was measured by HPLC coupled with fluorimetric detection. Ratios 5-HIAA/ 5-HT, DOPAC + HVA/DA and MHPG/NA were taken as an index of serotonin, dopamine and noradrenaline turnovers, respectively. Tripelennamine (1 and 10 mg/kg) significantly reduced serotonin turnover in control and morphine-dependent mice, and potentiated the serotonin turnover reduction when it was administered 30 min before naloxone injection. The dopamine turnover was diminished by tripelennamine (1 and 10 mg/kg) in the morphine-dependent group. Tripelennamine (10 mg/kg) reduced noradrenaline turnover during abstinence. These results suggest that the potentiation of opiate abstinence by tripelennamine could be related to its antiserotonergic profile.

Animals↗
PubMed1995

Morphine-induced changes in cerebral and cerebellar nitric oxide synthase activity.

The effect of acute and chronic morphine treatment on nitric oxide (NO) synthase activity (determined by the rate of conversion of [14C]arginine into [14C]citrulline) on mouse brain was studied. Acute morphine treatment induced an increased in Ca2+ -dependent NO synthase in cerebellum. This effect was blocked by coadministration with naloxone. Chronic morphine treatment (by s.c. pellet) also produced an increase in cerebellar NO synthase, with a maximum on the second day of implantation. No significant changes were found in frontal cortex and forebrain during acute or chronic morphine treatment. The relationship between opiate effects and the L-arginine: NO pathway is discussed.

Animals↗
PubMed1995

Changes induced by sodium cromoglycate in brain catecholamine turnover in morphine dependent and abstinent mice.

The effects of sodium cromoglycate (CRO) were studied in relation to the metabolism of brain catecholamines: dopamine (DA) and noradrenaline (NA), and their metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenylethyleneglycol (MHPG). CRO was injected SC in control mice, morphine-tolerant mice (tolerance was induced by SC implantation of a 75 mg morphine pellet; CRO was administered on day 4 of addiction) and 30 min before abstinence (withdrawal was induced by SC injection of naloxone (1 mg/kg) on day 4 of addiction). Brain catecholamines and their metabolites were measured using high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD), for DA, NA, DOPAC and HVA, and coupled with fluorescence detection for MHPG. The ratios of DOPAC + HVA/DA and MHPG/NA were kept as an index of DA and NA turnovers, respectively. CRO administered 30 min before naloxone-precipitated withdrawal diminished significantly NA levels in frontal cortex. CRO increased DA turnover in striatum and frontal cortex in naive animals and significantly diminished DA levels in frontal cortex and DOPAC levels in frontal cortex and midbrain in morphine-dependent mice. These findings are discussed in relation to the protective effects of CRO on opiate withdrawal and the effects of CRO on locomotor activity.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Group B Streptococcus and E. coli LPS-induced NO-dependent hyporesponsiveness to noradrenaline in isolated intrapulmonary arteries of neonatal piglets.

1. The effects of endotoxin (E. coli lipopolysaccharide, LPS) and heat inactivated group B Streptococcus (GBS) were studied on the contractile responses to noradrenaline (NA) in isolated pulmonary arteries and on the activity of the constitutive and inducible nitric oxide synthase (NOS) in lung fragments of neonatal piglets. 2. Short-term (< or = 5 h) incubation with LPS (1 micrograms ml-1) or GBS (3 x 10(7) colonies forming units ml-1) did not modify the vascular responsiveness to NA (10(-8) M-10(-4) M) in isolated intrapulmonary arteries. However, long-term incubation (20 h) with LPS or GBS produced a significant reduction in the maximal contractile responses and shifted the concentration-response curve for NA downwards. 3. Endothelium removal or the cyclo-oxygenase inhibitor meclofenamate (10(-5) M) did not affect the GBS- and LPS-induced hyporesponsiveness to NA. 4. The presence of the nitric oxide (NO) precursor, L-arginine (10(-5) M), 30 min prior to the contractility challenge increased the LPS- and GBS-induced pulmonary vascular hyporesponsiveness to NA. In contrast, the addition, prior to the challenge with NA, of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) or coincubation with dexamethasone (3 x 10(-6) M), a potent inhibitor of the induction of NOS, or with the protein synthesis inhibitor cycloheximide (10(-5) M) completely restored the reactivity to NA in LPS- and GBS-treated pulmonary arteries. 5. The incubation for 20 h of lung fragments with LPS and GBS produced a significant increase in the Ca2+-independent (inducible) NOS activity determined by the conversion of radiolabelled L-arginine to citrulline, but did not modify the constitutive NOS activity. This NOS induction was abolished by coincubation with dexamethasone (3 X 10-6 M).6. These results demonstrated that prolonged incubation with GBS and LPS causes an induction of NOS activity which results in a reduced vascular responsiveness to NA in pulmonary arteries of neonatal piglets. Thus, induction of NOS seems to be responsible for the delayed pulmonary vascular hyporesponsiveness induced by GBS (a Gram-positive) and E. coli (a Gram-negative), the most common causal agents of neonatal sepsis.

Amino Acid Oxidoreductases↗
PubMed1995

Suppression of immune parameters in animal models of morphine dependence.

Implantation of pellets containing 75 mg of morphine induced short term (4 day) morphine dependence and markedly reduced total number of spleen cells of BALB/c mice, without affecting total body or liver weight. Polyclonal responses induced by anti-CD3 antibodies, Concanavalin A or Escherichia coli lipopolysaccharide in the remaining spleen cells of morphine-treated mice were also inhibited. Cytofluorimetric analysis indicated that the proportion of major functional lymphocyte populations (Ig+, CD3+, CD4+ and CD8+ lymphocytes) were not significantly changed in the spleen from morphine-dependent mice. Furthermore, expression levels of surface Ig, CD3, CD4, and CD8, were similar in spleen cells from control or morphine-treated mice. So, morphine dependence in BALB/c mice under these controlled conditions results in a specific defect in lymphoid cell number and function, with no incidence on body weight or particular lymphocyte subsets.

Animals↗
PubMed1993

Changes induced by sodium cromoglycate on brain serotonin turnover in morphine dependent and abstinent mice.

This study was designed to explain the action of sodium cromoglycate (CRO) on the brain serotonergic system in control, morphine tolerant (by SC implantation of a 75 mg morphine pellet), and also in morphine dependent mice just before naloxone-precipitated withdrawal. After SC injections of CRO in control mice, morphine tolerant mice (day 4 of addiction), and 1 h before abstinence (withdrawal was induced by SC injection of 1 mg/kg naloxone on day 4 of addiction), animals were decapitated and various brain areas were rapidly removed. 5HT (Serotonin) and 5HIAA (5-hydroxyindole-3-acetic acid) were measured by high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD). The ratio 5HIAA/5HT provided one index by which the turnover of the indoleamine was measured. CRO increased the turnover of 5HT in most of the brain areas studied in both control and morphine dependent mice. Furthermore, previous administration of CRO prior to naloxone challenge induced a significant increase in the 5HIAA/5HT ratio in the hypothalamus and striatum. These results are discussed as the reason for the preventive effect of CRO on jumping behaviour in morphine abstinent mice.

Animals↗
PubMed1992

Role of sodium cromoglycate on analgesia, locomotor activity and opiate withdrawal in mice.

The role of sodium cromoglycate (CRO) on analgesia, locomotor activity and morphine withdrawal in mice was studied in morphine-dependent and drug-naive mice. CRO (0.5, 1, 5, 10, 30, 50 and 100 mg/kg, SC) induces analgesia (hot plate), an effect blocked by previous administration of the opiate antagonist naloxone (1 mg/kg). Furthermore, CRO (30 mg/kg) potentiates morphine analgesia. In morphine-tolerant mice, moderate doses of CRO (0.5, 1, 5, 10 and 30 mg/kg) do not induce analgesia, which suggested the development of cross tolerance between CRO and morphine, whereas coadministration of CRO and morphine in morphine tolerant animals restored the sensitivity to morphine. Administration of CRO (10 and 30 mg/kg) induces an increase in spontaneous locomotor activity, and previous administration of naloxone (1 mg/kg) blocks this effect, whereas CRO (10 mg/kg) blocks morphine (10 mg/kg) and amphetamine (3 mg/kg)-induced hyperactivity. CRO (10, 50 and 100 mg/kg) induces a significant and dose-dependent reduction in the number of jumps ("jumping up") during naloxone (1 mg/kg)-induced withdrawal in morphine-dependent mice. Finally, CRO (100 mg/kg) reduces the "wet dog shake" phenomenom during naloxone-induced withdrawal in morphine-dependent mice. These results suggest a possible stabilizing effect of CRO on the membranes of neurones that mediate analgesia, locomotor activity and opiate abstinence. Changes and inhibition of DA, NA and 5-HT release may also explain these effects.

Analgesics↗
PubMed1991

Influence of psychogenetics in opiate tolerance and abstinence in mice.

1. Four different strains of mice were used to study the influence of psychogenetics in opiate tolerance and abstinence. 2. The CD1 strain seemed to be more sensitive to naloxone administration after four days of morphine implantation, because administration of the antagonist induces a number of jumps in the withdrawal phase higher than in the case of the DBA or C3H strains. 3. DBA and C3H mice elicit analgesia before the CD1 strain, whereas the C3H mice lose body weight at a faster rate than the other strains. 4. C57 bl mice died after morphine implantation (100%). 5. These findings are discussed in relation with neurochemical and receptor variations.

Animals↗