Interrelationship between late gestational ewe factor and early life lamb factors in semi-arid tropical region.

The limitation in feed availability in the semi-arid region during the lean period can result in a variation of the body condition, body weight of pregnant ewe which in turn may affect the lamb birth weight, colostrum immunoglobulin, growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Therefore, the present study was initiated to assess the interrelationship between late gestational ewe factor and early life lamb factors in the semi-arid tropical region. For this purpose, 83 Malpura and 45 Avikaline pregnant ewes were selected and their body condition score (BCS) at late gestation, body weight at lambing, and birth weight of lambs was recorded. The BCS of ewes in late gestation had significant (P < 0.001) positive correlation (r2 = 0.465) with the birth weight of lambs. The body weight at lambing was significantly (P < 0.05) higher in single-lamber ewes as compared to twin-bearing ewes. The plasma IGF-1 of lamb increased significantly (P < 0.05) with the increase of BCS of ewe at the late gestation as well as body weight after lambing. The colostrum of twin-lamb producing ewes had higher (P < 0.05) IgG content than single-lamb producing ewes. The concentration of IGF-1 was significantly (P < 0.05) higher in single-born lamb as compared to twin-born lamb. Based on the results of the present study, it is to conclude that higher BCS at late gestation and higher body weight of ewes at lambing is desirable for producing lambs with a higher birth weight having higher growth potential as well as chances of survival.

The effects of L-carnitine on the combination of, inhalation anesthetic-induced developmental, neuronal apoptosis in the rat frontal cortex.

The anesthetic gas nitrous oxide (N2O) and the volatile anesthetic isoflurane (ISO) are commonly used in surgical procedures for human infants and in veterinary and laboratory animal practice to produce loss of consciousness and analgesia. Recent reports indicate that exposure of the developing brain to general anesthetics that block N-methyl-D-aspartate (NMDA) glutamate receptors or potentiate GABA(A) receptors can trigger widespread apoptotic neurodegeneration. In the present study, the question arises whether a relatively low dose of ISO alone or its combination with N2O entails significant risk of inducing enhanced apoptosis. In addition, the role of L-carnitine to attenuate these effects was also examined. Postnatal day 7 (PND-7) rat pups were exposed to N2O (75%) or a low dose of ISO (0.55%) alone, or N2O plus ISO for 2, 4, 6 or 8 h with or without L-carnitine. The neurotoxic effects were evaluated 6 h after completion of anesthetic administration. No significant neurotoxic effects were observed for the animals exposed to N2O or ISO alone. However, enhanced apoptotic cell death was apparent when N2O was combined with ISO at exposure durations of 6 h or more. Co-administration of L-carnitine (300 or 500 mg/kg, i.p.) effectively protected neurons from the anesthetic-induced damage. These data indicate that 6 h or more of inhaled anesthetic exposure consisting of a combination of N2O and ISO results in enhanced neuronal apoptosis, and L-carnitine effectively blocks the neuronal apoptosis caused by inhalation anesthetics in the developing rat brain.

Acute toxicity of carbonyl iron and sodium iron EDTA compared with ferrous sulfate in young rats.

According to the American Association of Poison Control Centers, exposures to excessive doses of iron supplements still occur in children less than 6 years of age. Since 1998, there has been one death among U.S. children in this age group. Exposures, including adverse events, to iron supplements and iron-containing vitamins for the years 1999 and 2000 were 23,215 and 24,249, respectively. To reduce the potential seriousness of such exposures, carbonyl iron (Fe(0)) has been suggested as a possible replacement for ferrous sulfate (FeSO(4)). Carbonyl Fe is a unique form of elemental iron because of its small particle size. It is highly bioavailable when used to correct iron deficiency anemia. There is also current interest in using sodium iron(III) ethylenediaminetetraacetate (NaFeEDTA) for food fortification. In this study both NaFeEDTA and carbonyl Fe were compared with FeSO(4), the most common form of iron for dietary supplements, to obtain information relevant to the acute toxicological profile in young rats. With FeSO(4) and NaFeEDTA, total liver nonheme iron increased with increasing dose, but the response was approximately 50% lower with NaFeEDTA compared with FeSO(4). Serum iron peaked at approximately 0.5 to 1 h for both FeSO(4) and carbonyl Fe, while NaFeEDTA was elevated up to 4 h. FeSO(4) had an LD(50) of 1.1 g Fe/kg and was approximately 45 times more toxic than carbonyl Fe, which had an LD(50) greater then 50 g Fe/kg. NaFeEDTA had an LD(50) of 1.3 g Fe/kg and, when compared with FeSO(4), had approximately the same level of toxicity.

Effect of L-carnitine pretreatment on 3-nitropropionic acid-induced inhibition of rat brain succinate dehydrogenase activity.

L-Carnitine (LC) plays an important regulatory role in the mitochondrial transport of long chain free fatty acids (FFA). 3-Nitropropionic acid (3-NPA) is known to induce cellular energy deficit and oxidative stress-related neurotoxicity via an irreversible inhibition of mitochondrial succinate dehydrogenase (SDH). In the present study, activity of SDH was measured in order to evaluate neuroprotective effects of LC against the 3-NPA-induced neurotoxicity. Male, CD Sprague-Dawley rats, three months old, were injected with either 50 or 100 mg/kg of LC, i.p., 30 min prior to 3-NPA (30 mg/kg, s.c.) or with 3-NPA alone. The activity of brain SDH was quantified spectrophotometrically in caudate nucleus (CN), frontal cortex (FC), and hippocampus (HIP) 60 min after the 3-NPA injection. The SDH activity in the animals treated with 3-NPA alone was 38% (CN), 50% (FC), and 36% (HIP) that of saline controls. Pretreatment with LC prior to 3-NPA injection attenuated decreases of SDH activity by approximately 15 and 29% (LC low and high dose, respectively). Despite the attenuation of SDH inhibition, the activity of SDH in these regions remained significantly lower in treated than in control rats (p < 0.05). It appears that the protective effect of LC against 3-NPA-induced oxidative stress cannot be explained by the direct action of LC to interfere with the SDH inhibition but are rather achieved by LC actions downstream of the SDH inhibition.

Selenium, an antioxidant, attenuates methamphetamine-induced dopaminergic toxicity and peroxynitrite generation.

Methamphetamine (METH) has been known to produce neurotoxicity via generation of reactive oxygen and nitrogen species. Selenium, an antioxidant, was reported to protect against METH-induced dopaminergic neurotoxicity in mouse caudate nucleus. In the present study, the in vitro and in vivo efficacy of the supplementation of selenium was studied in METH-induced generation of peroxynitrite. PC12 cell cultures were exposed to 200 microM METH either with or without 10 microM and 20 microM selenium (30 min prior to METH exposure). After 24 h, METH exposure resulted in the significant depletion of dopamine, and its metabolites DOPAC and HVA, as well as the significant formation of 3-nitrotyrosine (3-NT), a marker of peroxynitrite generation, in PC12 cell cultures. Selenium supplementation attenuated the depletion of dopamine and its metabolites, DOPAC and HVA and the formation of 3-NT in PC12 cells. For in vivo studies, adult male mice were supplemented with selenium in drinking water, 1 week before and 1 week after the multiple injections of METH (4x10 mg/kg, i.p. at 2-h interval) or an equivalent volume of saline. The supplementation of Se attenuated the formation of 3-NT in the striatum resulting from METH treatment. These data suggest that METH-induced neurotoxicity is mediated by the production of peroxynitrite, and selenium plays a protective role in METH-induced neurotoxicity.

Manganese-induced developmental neurotoxicity in the CD rat: is oxidative damage a mechanism of action?

Inhalation of high concentrations of manganese (Mn) is associated with an extrapyramidal motor disorder in humans. Oxidative damage, mediated by increased levels of Mn in dopaminergic brain regions and mitochondria, is a hypothesized mechanism of action for Mn-induced neuronal degeneration and loss. To test this proposed mechanism, developing CD rats, which may be at an increased risk for Mn-induced neurotoxicity, were exposed orally to 0, 25, or 50 mg/kg/day of MnCl2 from postnatal day (PND) 1 to 49 Brain regional and mitochondrial Mn levels, brain regional reactive oxygen species (ROS) levels, and whole-brain nuclear and mitochondrial 8-OHdG levels were used to evaluate Mn-mediated oxidative damage. High-dose Mn exposure was associated with increased spontaneous motor activity on PND 21 and decreased body weights on PND 49. On PND 21, Mn concentrations were increased in brain regions and mitochondrial fractions in both low- and high-dose groups. ROS levels were elevated in cerebellum but not striatum. On PND 49, Mn concentrations in brain regions and mitochondrial fractions were increased only in the high-dose group. Mn exposure did not significantly alter 8-OHdG levels in either mitochondrial or nuclear DNA. Selective uptake of Mn by the striatum or mitochondrial fraction was not demonstrated at either time point. These data allow us to conclude that oral exposure to high levels of Mn in developing CD rats resulted in increased brain regional and mitochondrial Mn levels, increased motor activity, and decreased body weights but not in selective accumulation of Mn in the striatum or mitochondrial fraction of any brain region or elevations in striatal ROS or whole-brain 8-OHdG levels. These findings do not support the hypothesis that oxidative damage, as assessed by ROS and 8-OHdG levels, is a mechanism of action in Mn-induced developmental neurotoxicity in the CD rat.

Selenium, an antioxidant, protects against methamphetamine-induced dopaminergic neurotoxicity.

Dopaminergic changes were studied in the caudate nucleus of adult female mice after pre- and post-treatment with an antioxidant, selenium, 72 h after the multiple injections of methamphetamine (METH, 4x10 mg/kg, i.p. at 2-h interval) or an equivalent volume of saline. Selenium treatment prevented the depletion of dopamine (DA) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in caudate nucleus resulting from the METH treatment. These data suggest that METH-induced neurotoxicity is mediated by free radical and selenium plays a protective role against METH-induced dopaminergic neurotoxicity.

Acute ibogaine injection induces expression of the immediate early genes, egr-1 and c-fos, in mouse brain.

The aim of the present study was to evaluate if an acute injection of ibogaine (IBO) induces immediate early gene expression in different regions of mouse brain. Adult male C57 mice received a single injection of IBO and were perfused transcardially with 1% paraformaldehyde 30 min after the drug administration. A single injection of IBO produced a significant increase of egr-1 messenger RNA induction in nucleus accumbens (NAc), caudate-putamen (CPu), frontal cortex (FCx), septum, dentate gyrus (DG) and CA3 region of hippocampus, whereas c-fos gene was induced in CPu, FCx, DG, septum and CA1 region of hippocampus. This gene expression may be due, in part, to the stimulant properties of IBO, as we found with other psychostimulants.

Effect of acute exposure to 3-nitropropionic acid on activities of endogenous antioxidants in the rat brain.

The response of endogenous antioxidants to acute exposure of the mitochondrial inhibitor, 3-nitropropionic acid (3-NPA), was investigated in selected rat brain regions. Rats treated with 3-NPA (30 mg/kg, s.c.) were sacrificed at 30, 60, 90 and 120 min after injection to examine the alterations in reduced glutathione levels (GSH), and activities of antioxidant enzymes, superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) in the hippocampus (HIP), frontal cortex (FC), and caudate nucleus (CN). CAT activity increased in the HIP 90 min after 3-NPA treatment. While cytosolic copper/zinc SOD (CuZn-SOD) and mitochondrial manganese SOD (Mn-SOD) levels increased in the FC at 120 min, only the Mn-SOD increased in the CN 90 min after treatment. The activity of GPx decreased in the HIP 120 min after 3-NPA injection. When compared with the control, administration of 3-NPA led to GSH depletion in HIP within 120 min. The depletion of GSH and induction of antioxidant enzyme activities after the 3-NPA exposure suggest conditions favorable for oxidative stress.

Systemic administration of MPTP induces thalamic neuronal degeneration in mice.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a known neurotoxicant primarily selective for catecholaminergic neurons, including those of the nigrostriatal dopaminergic system, thereby mimicking the pathology of Parkinson's disease (PD). In this study, serial transbrain sectioning, followed by staining with a newly developed fluorochrome (Fluoro-Jade) specific for degenerating neurons, was used to detect additional sites of MPTP-induced neuronal degeneration in mice. Male CD-1 mice received a single 50 mg/kg dose of MPTP intraperitoneally at room temperature or at a reduced temperature (6 degrees C), which has been shown to potentiate striatal dopamine depletion. Neuronal degeneration was observed in the substantia nigra pars compacta (SN), ventral tegmental area (VTA) and retrorubral field (RRF) of only animals dosed in the low temperature environment. Neuronal degeneration was also observed in other catecholaminergic nuclei in both treatment groups. In addition, degenerating cell bodies and fibers were detected in the midline and intralaminar thalamic nuclei of all dosed animals, regardless of the dosing environment. Pharmacological manipulations which prevented nigral degeneration (deprenyl and nomifensine pretreatment) also prevented the degeneration of thalamic neurons. MK-801 pretreatment, however, resulted in a disproportionate protection of the thalamic neurons. These findings confirm and extend our previous observations regarding the protective effect of hyperthermia in CD-1 mice and also suggest that regions of the thalamus may be relevant to the pathophysiology of PD.

Neonatal MSG reduces hypothalamic DA, beta-endorphin, and delays weight gain in genetically obese (A viable yellow/alpha) mice.

Neonatal treatment with monosodium glutamate (MSG) decreases proopiomelanocortin (POMC) peptides and results in obesity. The yellow mouse is a model of obesity induced by the viable yellow (Avy) gene at the agouti locus on Chromosome 2, which results in overproduction of a POMC receptor antagonist. Thus we hypothesized that MSG, when imposed on the genetically susceptible model, would alter the development of obesity. Both yellow obese (Avy) and black lean (alpha/alpha) males were injected on Postnatal Days 1, 3, 5, 7, and 9 with 2.0 mg/g body weight MSG or saline SC. Their food intake, growth parameters, and neurochemical status were examined. Paradoxically, MSG interacted with the yellow phenotype to delay the rapid rate of weight gain characteristic of this model (p < 0.05). Food intake was decreased (p < 0.05) in both phenotypes treated with MSG, as was hypothalamic content of dopamine (p < 0.05) and of the POMC peptide, beta-endorphin (p < 0.001). The yellow obese phenotype was more sensitive than the black lean phenotype to the neurochemical effect of early postnatal MSG administration. Recent reports suggest the agouti locus protein is an antagonist of the receptor for another POMC peptide, melanocyte-stimulating hormone (MSH). Therefore, the balance of functional activity between various POMC peptides appears to be an important factor in the development of both acquired and genetic obesity.

Iron/ascorbate-induced lipid peroxidation changes membrane fluidity and muscarinic cholinergic receptor binding in rat frontal cortex.

Lipid peroxidation (LP) is a complex process which involves the formation of lipid free radicals and leads to oxidative damage. LP has also been implicated in several neurodegenerative diseases as well as aging. In the present study, we evaluated the effects of the induction of LP in vitro on muscarinic cholinergic (Mch) receptor binding and membrane fluidity in rat brain. Membranes from the rat frontal cortex were peroxidized by adding ferrous sulphate (84 microM) and ascorbic acid (400 microM). Peroxidation was measured as the amount of thiobarbituric acid reactive products formed (nmol malondialdehyde/mg protein). Mch receptor binding was measured 10, 20 and 30 min after peroxidation. Membrane fluidity was evaluated by fluorescence polarization studies using two probes; 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4(trimethylamino)phenyl]-1,3,5-hexatriene (TMA-DPH). Significant alterations in Mch receptor binding (decreased Bmax and increased Kd) were found after peroxidation. Membrane fluidity was also significantly decreased after peroxidation as observed with both probes. The decrease in membrane fluidity was due to an increased cholesterol to phospholipid molar ratio after peroxidation. These data suggest that lipid peroxidation induces changes in membrane dynamics as detected by the fluorescent probes and such changes in membrane microviscosity may be the cause for alterations in Mch receptor kinetics.

Development of dopamine and N-methyl-D-aspartate systems in rat brain: the effect of prenatal phencyclidine exposure.

Phencyclidine (PCP) inhibits the uptake of the neurotransmitter dopamine (DA), and blocks N-methyl-D-aspartate (NMDA) receptor-regulated ion channels. PCP also binds to sigma receptors in vivo and in vitro in rat brain. Prolonged exposure to PCP in adults has been observed to reduce the number of PCP binding sites in brain. We designed these experiments to evaluate whether prolonged prenatal exposure to PCP produces alterations in the development of DA and NMDA systems in brain. To do so, we characterized the normal course of development of basal and stimulated DA release in striatal slices, the ontogeny of striatal DA concentrations, and the development of NMDA receptor channels and associated glutamate binding sites in frontal cortex. We compared these developmental profiles to those in rats exposed to prenatal PCP, in an attempt to characterize the effect of prenatal PCP exposure on the pattern of brain development. Pregnant CD rats were injected s.c. with either 0, 10 or 20 mg/kg PCP daily on gestational days 8 through 20. On postnatal days (PND) 8, 21, 45, or 100, rats were sacrificed and brain tissues isolated for in vitro assessment. In vitro [3H]DA release from striatal slices evoked by either 40 microM glutamate or 15 mM K+ increased over 250% from PND 8 to PND 45, and glutamate-stimulated release was still significantly below adult levels at PND 45. In contrast, D-methamphetamine (D-METH)-evoked [3H]DA release, frontal cortical glutamate binding sites and NMDA channels developed early, reaching adult levels on or before PND 21.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of chronic delta-9-tetrahydrocannabinol (THC) administration on neurotransmitter concentrations and receptor binding in the rat brain.

THC is the major psychoactive constituent of marijuana and is also known as an hallucinogenic compound. Numerous reports have shown that large doses of THC produce significant alterations in various neurotransmitter systems. The present study was designed to determine whether chronic exposure to THC produces significant alterations in selected neurotransmitter systems (dopamine, serotonin, acetylcholine, GABAergic, benzodiazepine, and opiate) in the rat brain. In Experiment 1, male Sprague-Dawley rats were gavaged with vehicle, 10 or 20 mg THC/kg body weight daily, 5 days/week for 90 days. Animals were killed either 24 hours or two months after the last dose. Brains were dissected into different regions for neurochemical analyses. Two months after the cessation of chronic administration, there was a significant decrease in GABA receptor binding in the hippocampus of animals in the high dose group. However, no other significant changes were found in neurotransmitter receptor binding characteristics in the hippocampus or in neurotransmitter concentrations in the caudate nucleus, hypothalamus or septum after chronic THC administration. In an attempt to replicate the GABA receptor binding changes and also to determine the [35S]TBPS binding in hippocampus, we designed Experiment 2. In this experiment, we dosed the animals by gavage with 0, 5, 10 or 20 mg THC/kg daily, 5 days/week or with 20 mg THC/kg Monday through Thursday and 60 mg/kg on Friday for 90 days. Results from this experiment failed to replicate the dose-dependent effect of THC on GABA receptor binding in hippocampus. Modulation of [35S]TBPS binding by GABA or 3 alpha-OH-DHP or inhibition by cold TBPS in frontal cortex did not show any significant dose-related effects. Results from these experiments suggest that chronic exposure to THC does not produce significant alterations in catecholamine or indoleamine neurotransmitter systems or in opiate or GABA receptor systems in the rat brain.

Behavioral evaluation of rats prenatally exposed to the adrenergic agonists clonidine and lofexidine.

Clonidine (CLON), is a widely used antihypertensive agent with a potential for expanded therapeutic application in combating drug withdrawal symptoms in opiate and alcohol addiction. Recently, CLON and an analogue lofexidine (LOF) have been shown to block the opiate withdrawal syndrome in a variety of species, including man. One new application of these agents may be as an alternative to methadone maintenance for pregnant opiate addicts. Any consideration along these lines will require screening for reproductive outcome and behavioral teratogenic effects. Dams were given s.c. injections of CLON (0.16 or 0.64 mg/kg) of LOF (0.64 or 2.56 mg/kg) once daily from gestational day (GD) 8-20. Neonatal body weights, at postnatal days (PNDs) 2, 15 and 30 were reduced in a dose-dependent manner, with LOF-induced reduction twice that of CLON. No significant differences were obtained on negative geotaxis, an auditory startle test, or a series of swimming immobilization tests across the periadolescent period. A series of activity measures carried out on PND 12, 14, 16 and 18 showed minor differences in the high dose LOF male animals, but not in any of the other drug-treated groups.

Adrenocortical, beta-endorphin and behavioral responses to graded stressors in differentially reared rats.

Isolation rearing has long been suspected to alter hormonal and behavioral responses to stress. Two experiments were conducted to test the hypothesis that isolates are more timid or fearful than socially reared rats when exposed to novel test environments. In both, isolate response to 3 graded stressors was compared to that of socially-reared rats. In the first experiment, animals were handled, shocked or not treated prior to testing to produce three levels of conditioned fear. They were then tested on four paradigms previously shown sensitive to conditioned fear: open field activity, emergence latency, auditory startle, and latency to accept food from the experimenter. In the second experiment, rats were given a 0-, 5- or 20-min forced swim, then sacrificed for analysis of plasma corticosterone and pituitary and hypothalamic beta-endorphin. It was found that isolates showed little evidence of enhanced behavioral timidity, although rearing effects were seen on all 4 behavioral measures. Plasma corticosterone levels increased in a graded fashion over the course of the forced swim, but there was no effect of rearing conditions. While there were no effects of rearing or stress on hypothalamic beta-endorphin, pituitary beta-endorphin content was lower in females than in males, and isolate males had lower pituitary endorphin than social males. In summary, these experiments provide no evidence that isolation rearing produces a primary, global increase in fearfulness, but identify several behavioral and hormonal differences associated with differential housing in rats.

Neurochemical evaluation of rats prenatally exposed to the adrenergic agonists clonidine and lofexidine.

Clonidine (CLON), an alpha-2 adrenergic agonist, is widely used to reduce hypertension; it is also recommended for blocking acute opiate withdrawal. Lofexidine (LOF), a CLON analog, is an investigational compound being readied for the marketplace. Since exposure to both drugs is likely to occur in the last two trimesters of human pregnancy, it is important to determine whether such exposure can have effects upon brain or behavior of offspring. Pregnant CD rat dams were given daily subcutaneous injections of saline, CLON, or LOF on days 8 through 20 of gestation. Maternal weight during gestation, neonatal weight and neurochemical measures were monitored. Maternal body weight was reduced in a dose dependent manner. At PND 1 brain ornithine decarboxylase (ODC) activity was reduced in LOF- but not CLON-exposed pups of both sexes. At this age no alteration was seen in whole brain catecholamine levels or in whole brain alpha-2-adrenergic binding.

Modulation of anterior pituitary dopamine receptors by estradiol 17-beta: dose-response relationship.

Exposure of ovariectomized rats to estradiol-17-beta for 48-96 hr resulted in a dose-dependent reduction in the number but not the Kd of D-2 dopamine receptors of the anterior pituitary. No influence of estrogen was observed on dopamine or muscarinic acetylcholine receptors of caudate or hypothalamus. The dose-response relationship observed suggested that the influence of estrogen is directly on the pituitary, not secondary to the alteration of dopaminergic systems in the hypothalamus.