Brain Monoamine Changes in Rats After Short Periods of Ozone Exposure

We have shown in our laboratory that cat's and rat's sleep disturbances are produced by 24 h of ozone (O₃) exposure, indicating that the central nervous system is affected by this gas. To demonstrate the probable changes in brain neurotransmitters, we evaluated the monoamine contents of the midbrain and striatum of rats exposed to 1 part per million O₃ for 1 or 3 hours periods. The results were compared with rats exposed to fresh air and to those exposed to 3 hours of O₃ followed by 1 or 3 hours of fresh air. We found a significant increase in dopamine (DA) and its metabolites noradrenaline (NA) and 3,4 dihydroxyphenylacetic acid (DOPAC), as well as an increase in the 5-hydroxyindolacetic acid (5-HIAA) contents of the striatum. There were no changes in homovanillic acid (HVA) and serotonin (5-HT) levels during O₃ exposure. Additionally, an increase in DA, NA and 5-HIAA in the midbrain during O₃ exposure was observed. Turnover analysis revealed that DA increased more than its metabolites in both the midbrain and striatum. However, the metabolite of 5-HT, i.e. 5-HIAA, increased more than its precursor, this reaching statistical significance only in the midbrain. These findings demonstrate that O₃ or its reaction products affect the metabolism of major neurotransmitter systems as rapidly as after 1 h of exposition.     

Analysis of Microbial Population Dynamics in a Partial Nitrifying SBR at Ambient Temperature

In this study, a lab-scale partial nitrifying sequencing batch reactor (SBR) was developed to investigate partial nitrification at ambient temperature (16–22 °C). Techniques of denaturing gradient gel electrophoresis (DGGE), cloning, and fluorescence in situ hybridization (FISH) were utilized simultaneously to study microbial population dynamics. Partial nitrification was effectively achieved in response to shifts of influent ammonium concentrations. DGGE results showed that higher ammonia concentration referred to lower ammonia-oxidizing bacteria (AOB) diversity in the SBR. Phylogenetic analysis revealed that all the predominant AOB was affiliated with Nitrosomonas genus. FISH analysis illustrated AOB was the predominant nitrifying bacteria of microbial compositions when SBR achieved partial nitrification (PN) at ambient temperature.     

Biochemical Modifications and Neuronal Damage in Brain of Young and Adult Rats After Long-Term Exposure to Mobile Phone Radiations

This study investigated the effect of exposure to mobile phone radiations on oxidative stress and apoptosis in brain of rats. Rats were allocated into six groups (three young and three adult). Groups 1 and 4 were not subjected to the radiation source and served as control groups. In groups 2 and 5, the mobile phones were only connected to the global system for mobile communication, while in groups 3 and 6, the option of calling was in use. Microwaves were generated by a mobile test phone (SAR = 1.13 W/kg) during 60 days (2 h/day). Significant increments in conjugated dienes, protein carbonyls, total oxidant status, and oxidative stress index along with a significant reduction of total antioxidant capacity levels were evident after exposure. Bax/Bcl-2 ratio, caspase-3 activity, and tumor necrosis factor-alpha level were enhanced, whereas no DNA fragmentation was detected. The relative brain weight of young rats was greatly affected, and histopathological examination reinforced the neuronal damage. The study highlights the detrimental effects of mobile phone radiations on brain during young and adult ages. The interaction of these radiations with brain is via dissipating its antioxidant status and/or triggering apoptotic cell death.     

The Toxicological Effects in Brain of Mice Following Exposure to Cerium Chloride

Cerium (Ce) compounds are now widely applied in medicine, agriculture, animal breeding, and daily life; however, the effects of Ce on human body, especially on the central nervous system, are still unclear. In order to investigate whether Ce exposure cause neurotoxicological effects, ICR mice were exposed to CeCl(3) through intragastric administration at 0, 2, 10, and 20?mg/kg body weight doses everyday for 60?days. The behaviors of spatial recognition memory, brain histopathology, the brain elements and neurochemicals, as well as enzymes activities in mice were determined. The Y-maze test showed that CeCl(3) exposure could significantly impair the behaviors of spatial recognition memory. Specifically, in these Ln(3+)-treated mice, the contents of Ca, Mg, Na, K, Fe, and Zn in brain were significantly altered, the activities of Na(+)/K(+)-ATPase, Ca(2+)-ATPase, Ca(2+)/Mg(2+)-ATPase, acetylcholine esterase, and nitric oxide synthase were significantly inhibited; monoamines neurotransmitters such as norepinephrine, dopamine, and 5-hydroxytryptamine were significantly decreased, while the contents of acetylcholine, glutamate, and nitric oxide were significantly increased. These results indicated that CeCl(3) exposure could impair the learning ability, which is attributed to the disturbance of the homeostasis of trace elements, enzymes, and neurotransmitter systems in the mouse brain. Therefore, our study aroused the attention of Ln application and long-term exposure effects.     

Angiotensin-Converting Enzyme Activity Is Reduced in Brain Microvessels of Spontaneously Hypertensive Rats

Abstract: Angiotensin-converting enzyme (ACE) activity in brain microvessels of spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) controls was measured. Cerebral microvessels, prepared from the cerebral cortices by the albumin flotation and glass bead filtration technique, were free of neuronal and glial elements. ACE activity in brain microvessels of SHR was lower than that of WKY. A Woolf-Augustinsson-Hofstee plot showed that the reduction of the enzyme activity in SHR was due to a 30% decrease in V_max without any change in K_m for substrate. The decrease of ACE activity in brain micro-vessels of SHR may indicate an impairment of the central renin-angiotensin system and may be related to cerebral microvascular dysfunctions occurring in hypertension.     

Exposure to Palladium Nanoparticles Affects Serum Levels of Cytokines in Female Wistar Rats

Background

Information currently available on the impact of palladium on the immune system mainly derives from studies assessing the biological effects of palladium salts. However, in the last years, there has been a notable increase in occupational and environmental levels of fine and ultrafine palladium particles released from automobile catalytic converters, which may play a role in palladium sensitization. In this context, the evaluation of the possible effects exerted by palladium nanoparticles (Pd-NPs) on the immune system is essential to comprehensively assess palladium immunotoxic potential.

Aim

Therefore, the aim of this study was to investigate the effects of Pd-NPs on the immune system of female Wistar rats exposed to this xenobiotic for 14 days, by assessing possible quantitative changes in a number of cytokines: IL-1α, IL-2, IL-4, IL-6, IL-10, IL-12, GM-CSF, INF-γ and TNF-α.

Methods

Twenty rats were randomly divided into four exposure groups and one of control. Animals were given a single tail vein injection of vehicle (control group) and different concentrations of Pd-NPs (0.012, 0.12, 1.2 and 12 μg/kg). A multiplex biometric enzyme linked immunosorbent assay was used to evaluate cytokine serum levels.

Results

The mean serum concentrations of all cytokines decreased after the administration of 0.012 μg/kg of Pd-NPs, whereas exceeded the control levels at higher exposure doses. The highest concentration of Pd-NPs (12 μg/kg) induced a significant increase of IL-1α, IL-4, IL-6, IL-10, IL-12, GM-CSF and INF-γ compared to controls.

Discussion and Conclusions

These results demonstrated that Pd-NP exposure can affect the immune response of rats inducing a stimulatory action that becomes significant at the highest administered dose. Our findings did not show an imbalance between cytokines produced by CD4⁺ T helper (Th) cells 1 and 2, thus suggesting a generalized stimulation of the immune system with a simultaneous activation and polarization of the naïve T cells towards Th1 and Th2 phenotype.     

Catecholamine Content Changes in Brain Regions of Spontaneously Hypertensive Rats Under Immobilization Stress

We compared the effect of immobilization stress on noradrenaline (NA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) content in two brain regions--diencephalon and pons-medulla oblongata--in young and adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). In SHR, NA content decreased with time after the onset of the stress, whereas levels of its metabolite MHPG increased. In WKY, NA and MHPG showed no change. The MHPG/NA ratio in both regions increased relative to the duration of the stress in SHR, whereas it remained almost constant in WKY. The rate of increase in the ratio was much higher in the diencephalon of adult (12-week-old) than of young (4-week-old) SHR. In SHR, NA turnover in the brain is readily affected by environmental stress, and these changes in the noradrenergic system may induce or sustain hypertension.     

Plasticity of Neurons and Glia Following Neonatal Hypoxic-Ischemic Brain Injury in Rats

Periventricular white matter injury in premature infants is linked to chronic neurological dysfunction. Periventricular white matter injury is caused by many mechanisms including hypoxia-ischemia (HI). Animal models of HI in the neonatal rodent brain can replicate some important features of periventricular white matter injury. Most rodent studies have focused upon early cellular and tissue events following unilateral neonatal HI that is elicited by unilateral carotid artery ligation and followed by timed exposure to moderate hypoxia. Milder hypoxic-ischemic insults elicit preferential white matter injury. Little information is available about long-term cellular effects of unilateral HI. One month after unilateral neonatal hypoxia ischemia, we show that all the components for structural reorganization of the brain are present in moderately injured rats. These components in the injured side include extensive influx of neurites, axonal and dendritic growth cones, abundant immature synapses, and myelination of many small axons. Surprisingly, this neural recovery is often found in and adjacent to cysts that have the ultrastructural features of bone extracellular matrix. In contrast, brains with severe hypoxia ischemia one month after injury still undergo massive neuronal degeneration. While massive destruction of neurons and glia are striking events shortly after brain HI, neural cells re-express their intrinsic properties and attempt an anatomical recovery long after injury. Special issue dedicated to Anthony Campagnoni.     

Delayed Increase of Brain Noradrenaline After Acute Footshock Stress in Rats

Several lines of evidence strongly suggest that accumulation of noradrenaline (NA) in the brain may underlie the hyperarousal symptoms experienced in post-traumatic stress disorder. In animal experiments, however, the effect of stress on NA content appears complex; acute stress reduces the level, while chronic stress tends to increase it. To explain this discrepancy, it is necessary to observe the long-term effects of acute stress on NA metabolism in the brain. In this study, rats were exposed to intermittent intense footshock stress for 1 h, and the brain NA content was measured for 7 days after the stress stimulus. Hypothalamic NA content was immediately reduced and recovered within 24 h. However, a significant NA increase was observed 7 days after the footshock. In the cerebral cortex and hippocampus, an increase in NA content was observed 1 day after the stress and lasted for at least 7 days. The fact that the content of 3-methoxy-4-hydroxyphenylglycol, a major NA metabolite, only transiently increased in all these regions possibly reflects NA release. These results indicate that increase in the brain NA content can be induced by acute stress, though its emergence is delayed. Importantly, this suggests that both acute and chronic stress may lead to NA accumulation under the same mechanism.     

Increased Reactive Oxygen Species Production in the Brain After Repeated Low-Dose Pesticide Paraquat Exposure in Rats. A Comparison with Peripheral Tissues

The pesticide paraquat (PQ) was found to be a suitable xenobiotic to model Parkinson’s disease. The reactive oxygen species (ROS) production was suggested to be the main cause of PQ toxicity but very few evidences were found for its generation in the brain in vivo after ip administration. We compared the effects of PQ-induced ROS generation between the brain structures and the peripheral tissues using two different hydroxyl radical generation markers. Repeated but not single ip PQ administration increased the levels of ROS in the striatal homogenates but, when measured in the extracellular microdialysis filtrate, no change was observed. The increased dopamine release was detected in the striatum after the fourth PQ administration and its basal levels were decreased. A single treatment with the pesticide did not influence ROS production in the lungs or kidneys but repeated intoxication decreased its levels. These results suggest that repeated, systemic administration of a low dose of PQ triggers intracellular ROS formation in the brain and can cause slowly progressing degenerative processes, without the toxic effects in the peripheral tissues.     

Brain Localization and Neurotoxicity Evaluation of Polysorbate 80-Modified Chitosan Nanoparticles in Rats

The toxicity evaluation of inorganic nanoparticles has been reported by an increasing number of studies, but toxicity studies concerned with biodegradable nanoparticles, especially the neurotoxicity evaluation, are still limited. For example, the potential neurotoxicity of Polysorbate 80-modified chitosan nanoparticles (Tween 80-modified chitosan nanoparticles, TmCS-NPs), one of the most widely used brain targeting vehicles, remains unknown. In the present study, TmCS-NPs with a particle size of 240 nm were firstly prepared by ionic cross-linking of chitosan with tripolyphosphate. Then, these TmCS-NPs were demonstrated to be entered into the brain and specially deposited in the frontal cortex and cerebellum after systemic injection. Moreover, the concentration of TmCS-NPs in these two regions was found to decrease over time. Although no obvious changes were observed for oxidative stress in the in vivo rat model, the body weight was found to remarkably decreased in a dose-dependent manner after exposure to TmCS-NPs for seven days. Besides, apoptosis and necrosis of neurons, slight inflammatory response in the frontal cortex, and decrease of GFAP expression in the cerebellum were also detected in mouse injected with TmCS-NPs. This study is the first report on the sub-brain biodistribution and neurotoxicity studies of TmCS-NPs. Our results provide new insights into the toxicity evaluation of nanoparticles and our findings would help contribute to a better understanding of the neurotoxicity of biodegradable nanomaterials used in pharmaceutics.     

Protective Effects of Cornel Iridoid Glycoside in Rats After Traumatic Brain Injury

Cornel iridoid glycoside (CIG) is the active ingredient extracted from Cornus officinalis. Our previous studies showed that CIG had protective effects on several brain injury models. In the present study, we aimed to examine the effects and elucidate the mechanisms of CIG against traumatic brain injury (TBI). TBI was induced in the right cerebral cortex of male adult rats. The neurological and cognitive functions were evaluated by modified neurological severity score (mNSS) and object recognition test (ORT), respectively. The level of serum S100β was measured by an ELISA method. Nissl staining was used to estimate the neuron survival in the brain. The expression of proteins was determined by western blot and/or immunohistochemical staining. We found that intragastric administration of CIG in TBI rats ameliorated the neurological defects and cognitive impairment, and alleviated the neuronal loss in the injured brain. In the acute stage of TBI (24–72 h), CIG decreased the level of S100β in the serum and brain, increased the ratio of Bcl-2/Bax and decreased the expression of caspase-3 in the injured cortex. Moreover, the treatment with CIG for 30 days increased the levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), enhanced the expression of synapsin I, synaptophysin and postsynaptic density protein 95 (PSD-95), and inhibited the apoptosis-regulating factors in the chronic stage of TBI. The present study demonstrated that CIG had neuroprotective effects against TBI through inhibiting apoptosis in the acute stage and promoting neurorestoration in the chronic stage. The results suggest that CIG may be beneficial to TBI therapy.     

Age-Related Changes in the DNA and RNA Content of the Brain in Spontaneously Hypertensive Rats

To elucidate the effects of aging accompanied with hypertension on brain nucleic acid, we measured both the DNA and RNA contents of six specific brain regions in adult (5–6 months old) and aged (18–22 months old) female spontaneously hypertensive rats (SHRs). Although no statistical difference was observed in the RNA content, the DNA content did tend to increase in the hippocampal CA1 of aged SHR (4.24 ± 0.55 ng/g protein, mean ± SD, n = 6) in comparison to that of adult SHR (3.21 ± 0.71 ng/g protein, n = 4). Hence, aged SHRs showed a significant decrease in the RNA to DNA ratio in the CA1 subfield of the hippocampus (3.79 ± 0.61) compared to adult SHR (5.27 ± 0.81). On the other hand, no other regions, except for the dorsolateral region of the striatum, showed any difference in the RNA/DNA ratio between aged and adult SHR. We therefore conclude that subtle changes in the nucleic acid occur in vulnerable regions of the brain in aged SHRs.     

Strain Differences in SA Gene Expression in Brain and Kidney of Normotensive and Hypertensive Rats

SUMMARY 1. In situ hybridization done using a ³⁵S-cRNA probe was carried out to obtain information on the expressions of the SA gene in brains and kidneys of the spontaneously hypertensive rat (SHR) strain obtained from the Izumo colony (/Izm) and from Charles River Laboratories (/Crj).2. In the brain, SA mRNA expression was most abundantly observed in epithelial cells of the choroid plexus. High to moderate levels was present on neurons of the CA1–CA4 pyramidal cell layer and the dentate gyrus of the hippocampus and the cerebellar Purkinje cell layer. The solitary tract nucleus and the dorsal motor nucleus of the vagus expressed the SA gene at very low levels. An increase in the expression was noted in the choroid plexus of WKY/Crj; there was no difference, however, in expression levels of other brain areas between WKY/Izm, SHR/Izm, and SHRSP/Izm, and between WKY/Crj and SHR/Crj.3. In the kidney, expression signals of SA mRNA were observed in renal medullary rays and focal cortex of WKY/Izm, SHR/Izm, SHRSP/Izm, and SHR/Crj, whereas mRNA expression in the WKY/Crj kidney was observed in medullary rays and outer strips of the outer medulla. Microscopically, hybridization signals were predominant in the proximal tubules.4. Expression densities decreased only in the kidney of WKY/Crj in 4-and 8-week-old rats, but not in the WKY/Izm kidney, compared with findings in SHR and SHRSP kidneys. These observations are in good agreement with data from Northern blot analysis.5. The SA gene expressions in the brain and the kidney seem not to relate to states of elevated blood pressure, but rather to strain differences. Abundant expressions in the brain and the kidney may mean that the SA gene plays a role in the water–electrolyte transport system. It is noteworthy that there are neuronal expressions of the SA gene in hippocampal pyramidal cells and cerebellar Purkinje cells.     

Clomipramine Treatment and Repeated Restraint Stress Alter Parameters of Oxidative Stress in Brain Regions of Male Rats

This study aimed to compare the effects of repeated restraint stress alone and the combination with clomipramine treatment on parameters of oxidative stress in cerebral cortex, striatum and hippocampus of male rats. Animals were divided into control and repeated restraint stress, and subdivided into treated or not with clomipramine. After 40 days of stress and 27 days of clomipramine treatment with 30 mg/kg, the repeated restraint stress alone reduced levels of Na⁺, K⁺-ATPase in all tissues studied. The combination of repeated restraint stress and clomipramine increased the lipid peroxidation, free radicals and CAT activity as well as decreased levels of NP-SH in the tissues studied. However, Na⁺, K⁺-ATPase level decreased in striatum and cerebral cortex and the SOD activity increased in hippocampus and striatum. Results indicated that clomipramine may have deleterious effects on the central nervous system especially when associated with repeated restraint stress and chronically administered in non therapeutic levels.     

Hematotoxicity and Genotoxicity of Mercuric Chloride Following Subchronic Exposure Through Drinking Water in Male Rats

Erythrocytes are a convenient model to understand the subsequent oxidative deterioration of biological macromolecules in metal toxicities. The present study examined the variation of hematoxic and genotoxic parameters following subchronic exposure of mercuric chloride via drinking water and their possible association with oxidative stress. Male rats were exposed to 50 ppm (HG1) and 100 ppm (HG2) of mercuric chloride daily for 90 days. A significant dose-dependent decrease was observed in red blood cell count, hemoglobin, hematocrit, and mean cell hemoglobin concentration in treated groups (HG1 and HG2) compared with controls. A significant dose-dependent increase was observed in lipid peroxidation; therefore, a significant variation was found in the antioxidant enzyme activities, such as superoxide dismutase, catalase, and glutathione peroxidase. Interestingly, mercuric chloride treatment showed a significant dose-dependent increase in frequency of total chromosomal aberration and in percentage of aberrant bone marrow metaphase of treated groups (p < 0.01). The oxidative stress induced by mercury treatment may be the major cause for chromosomal aberration as free radicals lead to DNA damage. These data will be useful in screening the antioxidant activities of natural products, which may be specific to the bone marrow tissue.     

Changes in Glycoprotein Metabolism in the Cerebral Cortex Following First Exposure of Dark-reared Rats to Light

Abstract: The level of incorporation of [³H]fucose or [³H]lysine into subcel-lular fractions of the visual and motor cortices of 50-day-old dark-reared (D) and light-exposed (L) rats was determined. No differences were found between D and L rats in the incorporation of either precursor into subcellular fractions of the motor cortex, or in any fraction of the visual cortex except the synaptic-membrane fraction. After a 3-h light exposure the incorporation of [³H]fucose into the visual cortex synaptic-membrane fraction was elevated (L/D = 136%). Incorporation of [³H]lysine was elevated in the visual cortex synaptic-membrane fraction of L compared to D rats after a 1-h exposure (L/D = 118%). However, after a 3-h exposure the incorporation was depressed in this fraction (L/D = 79%). No differences could be found in the levels of activity of fucosyl transferase following first exposure to light but dark-rearing itself resulted in increased enzyme activity in the motor cortex compared to normal controls. First exposure of 20-day-old dark-reared rats to light led to an increase in the incorporation of [³H]fucose into soluble glycoproteins of both the visual and motor cortex and into particulate glycoproteins of the visual cortex only. These results are in contrast with those found with 50-day-old animals and suggest that the effects of light-exposure on [³H]fucose incorporation may be age-dependent.     

Effect of Selective Brain Hypothermia on Regional Cerebral Blood Flow and Tissue Metabolism Using Brain Thermo-Regulator in Spontaneously Hypertensive Rats

To investigate the effect of selective hypothermia of the brain (brain cooling) on regional cerebral blood flow and tissue metabolism, we have developed a brain thermo-regulator. Brain temperature was modulated by a water-cooled metallic plate placed on the surface of the rats' scalp to get the appropriate brain temperature precisely with ease. Regional cerebral blood flow and brain temperature were measured simultaneously using a Teflon-coated platinum electrode and thermocouple probe inserted stereotaxically into the parietal cortex and thalamus in spontaneously hypertensive rats. Experimental forebrain ischemia was induced by the occlusion of bilateral common carotid artery under normo- and hypothermic brain condition, and the supratentorial brain tissue metabolites were measured enzymatically after 60 min of forebrain ischemia. When cortical temperature was set to hypothermia, cortical blood flow was significantly lowered by 40% at 30°C and 20% at 33°C as compared with that at 36°C (p < 0.0001 and p < 0.05, respectively). Thalamic blood flow was also significantly reduced by 20% when cortical temperature was set to 30°C as compared with 36°C (p < 0.05). There were no significant differences in arterial blood pressure and gas parameters throughout these experiments. In the rats with selective brain hypothermia (30°C) immediately after the induction of cerebral ischemia, the level of brain ATP concentration after 60 min of ischemia was significantly higher than that in normothermia rats (36°C) (p < 0.05). Our findings indicate that: 1) the metallic plate brain thermo-regulator is useful in small animal experiments; 2) regional brain temperature regulates regional cerebral blood flow; and 3) selective brain hypothermia, even started after the forebrain ischemia, ameliorates the derangement of brain metabolism, suggesting its effectiveness as a cytoprotective strategy.