Effects of Selenium Administration on Erythrocyte and Blood Plasma Glutathione Peroxidase Activity in Goats

The activity of glutathione peroxidase (GSH-Px, E.G. 1.11.1.9.) was determined in heparinized whole blood, blood plasma and washed erythrocytes from goats before and up to 4 weeks after the administration of selenium (0.4 mg/10 kg BW) and vitamin E (20 mg/10 kg BW) or only vit. E (20 mg/10 kg BW). It was found that Se administration caused a significant increase in enzyme activity in whole blood and washed erythrocytes first detected 2 weeks after the intramuscular injection of Se. No changes were observed in plasma from the treated animals. Minor and insignificant changes were seen in the vit. E treated control animals. It is concluded that GSH-Px activity in blood plasma or serum is of no value as a short-term indicator of the selenium status of goats but whole blood is a good indicator of the long-term status.     

Administration of Dexamethasone Up-Regulates Protein Kinase C Activity and the Expression of γ and ε Protein Kinase C Isozymes in the Rat Brain

Abstract : Altered hypothalamic-pituitary-adrenal (HPA) function (increased plasma cortisol level) has been shown to be associated with mood and behavior. Protein kinase C (PKC), an important component of the phosphatidyl-inositol signal transduction system, plays a major role in mediating various physiological functions. The present study investigates the effects of acute (single) and repeated (10-day) administrations of 0.5 or 1.0 mg/kg doses of dexamethasone (DEX), a synthetic glucocorticoid, on B _max and K _D of [³H]phorbol 12,13-dibutyrate ([³H]PDBu) binding, PKC activity, and protein expression of PKC isozymes, α, β, γ, δ, and ε in the membrane and the cytosolic fractions of rat cortex and hippocampus. It was observed that repeated administration of 1.0 mg/kg DEX for 10 days caused a significant increase in B _max of [³H]PDBu binding to PKC, in PKC activity, and in expressed protein levels of the γ and ε isozymes in both the cytosolic and the membrane fractions of the cortex and the hippocampus, whereas a lower dose of DEX (0.5 mg/kg for 10 days) caused these changes only in the hippocampus. On the other hand, a single administration of DEX (0.5 or 1.0 mg/kg) had no significant effect on PKC in the cortex or in the hippocampus. These results suggest that alterations in HPA function from repeated administration of glucocorticoids may modulate PKC-mediated functions.     

Repeated Administration of Dexamethasone Increases Phosphoinositide-Specific Phospholipase C Activity and mRNA and Protein Expression of the Phospholipase C β1 Isozyme in Rat Brain

Altered hypothalamic-pituitary-adrenal (HPA) function has been shown to be associated with changes in mood and behavior. The enzyme phosphoinositide-specific phospholipase C (PI-PLC), an important component of the PI signal transduction system, plays a major role in mediating various physiological functions. In the present study, we investigated the effects of a single dose and of repeated administration (0.5 or 1.0 mg/kg for 10 days) of dexamethasone (DEX), a synthetic glucocorticoid, on PI-PLC activity and on expression of PLC isozymes (beta1, delta1, and gamma1) in rat brain. Repeated administration of DEX (1.0 mg/kg) caused a significant increase in PI-PLC activity and in protein expression of the PLC beta1 isozyme in both membrane and cytosol fractions of cortex and hippocampus; however, the repeated administration of a smaller dose of DEX (0.5 mg/kg) caused these changes only in hippocampus but not in cortex. The increase in PLC beta1 protein was associated with an increase in its mRNA level, as measured by competitive RT-PCR. A single administration of DEX (0.5 or 1.0 mg/kg) to rats had no significant effects on PI-PLC activity or on the protein expression of PLC isozymes. These results suggest that DEX up-regulates PI-PLC in rat brain, which presumably is due to a selective increase in expression of the PLC beta1 isozyme, and that these changes in PI-PLC may be related to HPA axis-mediated changes in mood and behavior.     

Brain monoamine oxidase in suckling rabbits treated with organophosphorus compound. I. Acute intoxication

In 16-day-old rabbits treated with dichlorvos 8 mg/kg per os the activity of monoamine oxidase A form (MAO A) in brain was studied. A short-lasting decrease of brain MAO A was followed by a recovery of enzyme activity within 120 min. In parallel to changes in MAO A activity breathing disturbances were observed. It is concluded that the decrease of MAO A was due rather to hypoxia than to a direct effect of dichlorvos. In 16-day-old rabbits clorgyline (2 mg/kg) and tranylcypromine (10 mg/kg) were potent inhibitors of MAO A but deprenyl and pargyline were ineffective.     

Picrotoxin-induced disruption of bidirectional active avoidance behavior and locomotor activity

The effects of picrotoxin (0.75 and 1.5 mg/kg), an antagonist of GABA mediated chloride ion conductance changes, were examined on the acquisition and performance of a bidirectional active avoidance (BAA) response and on locomotor activity. Treatment with this agent disrupted both the acquisition and performance of this task and decreased locomotor activity. This picrotoxin-induced suppression of BAA was reversed by pre-treatment with diazepam (2 mg/kg), d-amphetamine (d-AMP, 2.0 mg/kg) and lysergic acid diethylamide (LSD, 10 μmg/kg). Picrotoxin-induced activity decreases in locomotor activity were antagonized by d-AMP, were partially reversed by LSD but were not reversed by methysergide. It is proposed that picrotoxin disrupts bidirectional active avoidance behavior by increasing the response suppressive effects of aversive stimuli and by inducing a general depression of motility.     

Analgesic effect of tianeptine in mice

The effects of tianeptine, a novel and unusual tricyclic antidepressant drug, on tail-flick and hot-plate tests, which are two thermal analgesia evaluating methods, have been investigated in mice. Tianeptine (5 and 10 mg/kg), para-chlorophenylalanine (pCPA) (100 mg/kg) and a combination of pCPA and tianeptine (10 mg/kg) or saline were injected to mice intraperitoneally. pCPA (100 mg/kg) was injected 24 h before tianeptine or saline treatment when it was combined with tinaeptine (10 mg/kg) or tested alone. The tail-flick latencies and hot-plate reaction times of the mice were measured between 15th and 180th minutes following injections. Tianeptine (10 mg/kg) exhibited a significant antinociceptive activity that could be measured by both tests as compared to groups which were treated with saline or pCPA alone between 15th and 180th min of the observation period. The lower dose of tianeptine (5 mg/kg) or pCPA (100 mg/kg) did not produce any significant changes on tail-flick latency or hot-plate reaction time of the mice. However, pretreatment with pCPA completely blocked the antinociceptive effect induced by tianeptine (10 mg/kg) in both tests used in the present study. Furthermore, tianeptine (10 mg/kg) did not cause any significant impairment effects on rotarod performance of the mice. Our results suggested that tianeptine has a prominent thermal antinociceptive activity in mice and that increased serotonergic activity may be responsible for the analgesic effect of tianeptine.     

THE EFFECTS OF LITHIUM ON ATPase ACTIVITY IN SUBCELLULAR FRACTIONS FROM RAT BRAIN

Abstract— The effects of lithium chloride in vitro and in vivo were investigated on Na-K ATPase and Mg ATPase activities in synaptic plasma membrane, mitochondrial and synaptic vesicle fractions prepared from rat brain. In vitro , lithium chloride (10⁻³-10⁻⁸ m ) had no effect on ATPase activity in any of the fractions studied. Lithium chloride given chronically by i.p. injection (30 mg/rat/day) for 9 days had little effect on synaptic plasma membrane ATPases. Dietary administration of lithium chloride (60 mmol/kg food) produced a small but significant increase in synaptic plasma membrane Mg ATPase activity after 3 weeks administration and mitochondrial Mg ATPase activity after 1 week. There was no effect on synaptic plasma membrane Na-K ATPase activity. Salt supplementation reduced the toxic effects of lithium administration and it is suggested that toxicity may account for some of the previously reported changes in synaptic membrane ATPases produced by lithium.     

Modification of biochemical parameters of gentamicin nephrotoxicity by coenzyme Q10 and green tea in rats

The present study was designed to investigate the possible potential protective role of coenzymeQ10 (CoQ10; 10 mg/kg/day, ip) and/or green tea (GT; 25mg/kg/day, po) against gentamicin (GM) nephrotoxicity. Marked increase in the level of serum urea. creatinine and lipid peroxidation (LPO) content was found after administration of gentamicin (80 mg/kg/day, ip) for eight days along with significant decrease in the antioxidant enzymes, superoxide dismutase (SOD), reduced glutathione (GSH), catalase (CAT) as well as brush border enzymes (Na+/K+ ATPase, Mg(+2)ATPase and Ca2+ ATPase).Treatment with CoQ10 or green tea alone with GM showed significant decrease in serum urea, creatinine and tissue LPO content and significant increase in antioxidant and membrane bound enzymes. Combined treatment with CoQ10 and green tea was more effective in mitigating adverse effect of GM nephrotoxicity. The present work indicated that CoQ10 and green tea due to their antioxidant activity modified the biochemical changes occurred during gentamicin nephrotoxicity and thus had a potential protective effect.     

Toxicity of endosulfan on kidney of male rats in relation to drug metabolizing enzymes and microsomal lipid peroxidation

Endosulfan administration (po, 15 and 30 days at 7.5 and 10 mg/kg body wt respectively) inhibited the activity of microsomal mixed function oxidases in kidney tissue of male rats. Microsomal and cytosolic protein contents of kidney were significantly increased following 30 days endosulfan exposures. Profound induction in the activity profiles of alcohol dehydrogenase and cytosolic glutathione s-transferase was noticed, however, no such change was apparent in the activity of aldehyde dehydrogenase. Microsomal preparations from treated animals showed a dose and duration dependent increase in spontaneous lipid peroxidation. The observed biochemical changes persisted even after 7 days normalcy allowance provided after the endosulfan (10 mg/kg body wt) withdrawl. The results suggest a substantial renal toxicity of endosulfan to male rats in relation to microsomal mixed function oxidases and associated functions which possibly resulted from lipid peroxidative damage of microsomal membrane in treated animals.     

Role of the GABA-ergic systems of the brain in manifesting the activating effect of diazepam]

It was shown in experiments on rats that the selective blocker of GABA receptors bicuculline (2 mg/kg) does not decrease the activating effect of diazepam as to the reaction of self-stimulation. The GABA-mimetic muscimol (0.5 and 1 mg/kg) had no effect on self-stimulation rate, while in the dose of 2 mg/kg causing behavioral changes produced a powerful decrease in it (by 93.3%). During the combined administration of diazepam and muscimol (1 mg/kg and 0.5 mg/kg, respectively) no potentiation of diazepam effect was observed. It is suggested that diazepam-induced facilitation of the reaction of self-stimulation is not due to the alteration in the activity of GABA-ergic processes.     

Comparison of the ability of opioid analgesics to increase endogenous opioid-like activity in the cerebrospinal fluid of rabbits

We have previously demonstrated that the acute administration of morphine increases the level of endogenous substances, which have antinociceptive activity, in cerebrospinal fluid (CSF). The present study was conducted to determine whether other opioid analgesics exert a similar effect. CSF was withdrawn from the cisterna magna of anesthetized rabbits before and after s.c. injections of meperidine, pentazocine, levorphanol and methadone, and was bioassayed for opioid-like activity in the mouse tail-flick and phenylquinone writhing tests. The opioid-like activity of CSF taken 60 min after meperidine (50 mg/kg) was significantly increased in both bioassays, and the CSF level of meperidine was insufficient to account for this effect. Pentazocine (25-75 mg/kg) also significantly increased opioid-like activity in rabbit CSF, but the effects of methadone (5-10 mg/kg) and levorphanol (20 mg/kg) were less marked. Dextrorphan (20 mg/kg), diazepam (10 mg/kg) and pentobarbital (20 mg/kg) administration did not significantly increase opioid-like activity in CSF. It is concluded that the antinociceptive action of some opioid analgesics in rabbits may be mediated in part by the release of endogenous antinociceptive substances.     

Liver gamma-glutamyl transpeptidase activity following chronic treatment with acetylsalicylic acid in rats

In the present study, rats were administered acetylsalicylic acid (ASA), at low and high doses, by means of a gastric tube for 30 days. Chronic administration of a high dose of ASA (200 mg/kg body weight) resulted in a significant increase in liver plasma membrane gamma-glutamyl transpeptidase activity, cholesterol, and phospholipid levels. The enzymatic activity and lipid levels appeared not to be affected by ASA when given at a lower dose (50 mg/kg body weight). The changes in the enzymatic activity of plasma membrane were positively correlated to membrane cholesterol content. These findings suggest that the hepatotoxicity of high doses of ASA should not be overlooked during clinical use of the drug.     

Effect of strophanthin and digoxin on the activity of succinate and lactate dehydrogenases and membrane Na+, K+-ATPase in the heart of rats with experimental myocarditis

In rats with adrenaline-induced myocarditis conditionally therapeutic doses of strophanthin (2.7 mg/kg) and digoxin (0.89 mg/kg) were chosen according to performance of the test of swimming until the complete fatigue. The influence of drugs in these doses on enzymatic activity was evaluated by histochemical methods in heart of control and myocarditis rats. It was found out that both of cardiac glycosides decreased lactate dehydrogenase and membrane Na+, K+-ATPase activity and increased succinate dehydrogenase activity in rats with experimental myocarditis.     

Corticosterone synthesis and serum levels at the end of the perinatal period a study of the effects of stress, diazepam and polyethylene glycol treatments.

The effects of stress (intraperitoneal injections onece daily for three days), diazepam (Faustan, Germed) and polyethylene glycol (Macrogolum, Spofa) on the corticosterone production rate (BPR) and concurrent changes in serum corticosterone levels (BSL) were investigated in 4-day-old male rats. Stress stimulation increased the BSL but the BPR was affected only slightly and the difference was not statistically significant. A low dose of diazepam (1 mg/kg) prevented the stress-induced rise in BSL and decrease of BPR, in comparison to stressed animals. On the contrary, high doses of diazepam (10 mg/kg) increased the BSL, while BPR corresponded to control values. Polyethylene glycol (0.12 g/kg; substance of this class is contained in the diazepam vehiculum) decreased the BSL, but the BPR was increased above control values; a higher dose of this substance (1.2 g/kg) yielded only scattered, non-significant results. It is concluded that in preweaned animals 1. the changes in BSL may be associated with minor or transient changes in BPR which indicate small changes in brainpituitary adrenocorticotropic activity, 2. changes in peripheral corticosterone metabolism can play an exceptionally important role in the regulation of glucocorticoid activity in very young rats, 3. a comparison of controls with stressed animals which had received low doses of diazepam indicate a relatively high steady state activity of adrenal cortex and its regulation in 4-day-old control rats.     

Effect of beta-adrenoceptor antagonists and some related drugs on maximal electroshock seizures in mice

(+/-) Propranolol (1-50 mg/kg), (+) propranolol (50 mg/kg) and pindolol (10-50 mg/kg) exhibited significant protective effects against MES (maximum electroshock seizures), whereas, timolol (1 mg/kg), the propranolol analog, UM-272 (1 and 10 mg/kg), and the beta-agonist, terbutaline (1 and 10 mg/kg) were ineffective. Cholinergic agents, physostigmine (0.01-1.0 mg/kg), and atropine (1 and 10 mg/kg), the serotonin antagonist, cyproheptadine (0.05 mg/kg), and the prostaglandin synthesis inhibitor, indomethacin (10 mg/kg), were also without effect on the MES extensor phase. Further, pretreatment of mice with terbutaline, atropine, cyproheptadine or indomethacin did not influence the anti-MES effect of propranolol to any significant extent. The results indicate that the observed anticonvulsant effects of beta-adrenoceptor antagonists are unrelated to noradrenergic or other central neurotransmitter systems and that a non-specific mechanism, probably a membrane stabilizing effect is involved.     

Suppressive effect of coenzyme Q10 on phospholipase A2 activation in cardiac cells after prolonged swimming.

Phospholipase A2 (PLA2) activity is elevated in cardiac microsomal fractions and phospholipids (PL) are much reduced in both the cardiac mitochondria and microsomal fractions from rats subjected to prolonged swimming. Preadministration of coenzyme Q10 (CoQ10 i.v. 30 mg/kg) significantly suppressed these changes. Two groups of 8-week-old male Wistar rats were trained to swim, receiving 30 min of training for 4 days. On the fifth day they were given an intravenous injection of either 30 mg/kg CoQ10 in saline or 1 ml saline. Thirty minutes later they began to swim for 3 hours carrying a weight representing 3% of body weight. On completion of the swim they were sacrified by instantaneous decapitation, and cardiac mitochondria were isolated. Mitochondria were also prepared from saline injected, unexercised control rats. Phosphatidylethanolamine (PE) and phosphatidylcholine (PC) concentrations were measured with HPLC and PLA2 activity was assayed fluorometrically. The mitochondrial concentrations (means +/- SEM, n = 6) of PE and PC were respectively 126 +/- 22 and 140 +/- 22 nmol/mg protein in the exercise-CoQ10 group against 66 +/- 4 and 50 +/- 10 nmol/mg protein in the exercise-saline group. The specific PLA2 activities (expressed as nmol degraded dipyrene phosphorylethanolamine substrate/hr/mg protein) in the microsomes was 0.20 +/- 0.02 in the exercise-CoQ10 group against 0.30 +/- 0.02 in the exercise-saline group. These results suggest CoQ10 has a protective effect against an excessive reduction in mitochondrial membrane phospholipids during prolonged exercise.     

Protective effect of coleonol on biochemical changes produced in coronary ligation induced ischemia

Coleonol, a diterpine prevented biochemical changes induced by coronary artery ligation in rabbits at a dose of 10 mg/kg, iv. It increased the heart mitochondrial oxygen uptake and O ratio, which may be responsible for the stabilization of heart membrane. The decrease in serum creatine phosphokinase, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase phospholipase and lipid peroxide and increase in cytochrome P450, glycogen and superoxide dismutase activity by coleonol treatment could have contributed to restore myocardial integrity and cardiac function disturbed by coronary artery ligation. The cardioprotective activity of coleonol was found to be comparable to propranolol.     

The possible involvement of GABA mechanisms in the action of benzodiazepines on central catecholamine neurons.

With the use of quantitative microspectrofluorometry, it has been shown that diazepam (10 mg/kg) and chlordiazepoxide (10 mg/kg) reduce DA turnover in the tuberculum olfactorium, nuc. accumbens, the DA islands of the entorhinal cortex, and caput of nuc. caudatus, whereas DA turnover is increased in the lateral external layer of the median eminence after 10 mg/kg of diazepam. It is of considerable interest that with a dose of 1 mg/kg of diazepam a reduction of DA turnover can still be observed in the tuberculum olfactorium and nuc. accumbens but not in the nuc. caudatus, due to a high variability of the response in this area. A similar trend is also found with chlordiazepoxide. Thus, changes in limbic DA turnover are observed in doses close to the minimal effective dose (0.6 mg/kg) needed to release punished behavior and to cause anticonvulsive effects, and may therefore be related to these actions of diazepam. For various reasons it is speculated that an increased GABA receptor activity on the DA cell bodies and their dendrites could mainly be involved in causing the reduction of DA turnover observed after benzodiazepines by diminishing the firing rate in the ascending DA pathways, particularly the mesolimbic DA pathways. Evidence for a change of GABA turnover by diazepam has also been found. It is also suggested that the reduction of cortical NE turnover found after benzodiazepines can partly involve an increased GABA receptor activity on the locus ceruleus cells, although the activation of E receptors on these cells cannot be excluded. These effects on locus ceruleus may be partly responsible for the sedation found after benzodiazepines. Diazepam (1 mg/kg) mimics both clonidine and GABA-ergic drugs in reducing blood pressure and slowing respiration rate, but the effects are blocked by picrotoxin but not by piperoxane, an E receptor-blocking agent. In agreement with the view that blockade of the stress-induced increases of NE turnover by benzodiazepines may be related to their antianxiety actions, it was found that the increase in NE turnover elicited by yohimbine, a drug that causes anxiety in man, is blocked by diazepam.     

Toxicity of pure alkaloid of Tylophora asthamatica in male rat

Administration of pure alkaloid of T. asthamatica, suspended in peanut oil and given in single doses (12-100 mg/kg) by gavage, to male rats caused inactivity, respiratory distress, salivation, nasal discharge and diarrhoea. The oral LD50 value of the alkaloid was 35.32 mg/kg. In short term toxicity study daily doses of the alkaloid (1.25, 2.5, 5 and 10 mg/kg) were given to male rats for 15 days. Smaller doses of the alkaloid (1.25 and 2.5 mg/kg/day) produced no signs of poisoning or death in animals; while 5 mg/kg/day produced signs of poisoning and death of two animals, 10 mg/kg/day caused death of all the animals within 7 days. Activities of glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and alkaline phosphatase were significant and associated with morphological changes in liver. The alkaloid also caused marked changes in the morphology of seminiferous tubules and spermatogenic activity of experimental animals. Since the alkaloid is effective in microgram quantities, the non toxic effects observed after daily doses of 1.25 mg/kg in male rats assume great therapeutic significance.