Effects of cytomegalovirus infection in human neural precursor cells depend on their differentiation state.

Cytomegalovirus (CMV) is the most common cause of congenital infection in developed countries and a major cause of neurological disability in children. Although CMV can affect multiple organs, the most important sequelae of intrauterine infection are related to lesions of the central nervous system. However, little is known about the pathogenesis and the cellular events responsible for neuronal damage in infants with congenital infection. Some studies have demonstrated that neural precursor cells (NPCs) show the greatest susceptibility to CMV infection in the developing brain. We sought to establish an in vitro model of CMV infection of the developing brain in order to analyze the cellular events associated with invasion by this virus. To this end, we employed two cell lines as a permanent source of NPC, avoiding the continuous use of human fetal tissue, the human SK-N-MC neuroblastoma cell line, and an immortalized cell line of human fetal neural origin, hNS-1. We also investigated the effect of the differentiation stage in relation to the susceptibility of these cell lines by comparing the neuroblastoma cell line with the multipotent cell line hNS-1. We found that the effects of the virus were more severe in the neuroblastoma cell line. Additionally, we induced hNS-1 to differentiate and evaluated the effect of CMV in these differentiated cells. Like SK-N-MC cells, hNS-1-differentiated cells were also susceptible to infection. Viability of differentiated hNS-1 cells decreased after CMV infection in contrast to undifferentiated cells. In addition, differentiated hNS-1 cells showed an extensive cytopathic effect whereas the effect was scarce in undifferentiated cells. We describe some of the effects of CMV in neural stem cells, and our observations suggest that the degree of differentiation is important in the acquisition of susceptibility.

Effect of arsenic on regulatory T cells.

INTRODUCTION: Arsenic (As) affects the function and survival of lymphocytes, and some arsenic compounds exert a relevant antineoplastic effect. We have explored the effect of As on T regulatory cells. RESULTS AND DISCUSSION: In vitro experiments with peripheral blood mononuclear cells from healthy subjects showed that low concentrations of As tended to increase the number of natural T regulatory (nTreg) lymphocytes, whereas concentrations >5.0 muM had an opposite effect. Furthermore, rats exposed to As showed redistribution of nTreg cells, and As administration to rats with experimental allergic encephalomyelitis increased the levels of nTreg cells in spleen and diminished the severity of this condition. On the other hand, in 47 apparently healthy subjects chronically exposed to As, we found significant inverse correlation between urinary As levels and the number and function of nTreg lymphocytes. Although most of these individuals showed enhanced levels of apoptotic lymphocytes in peripheral blood, with a diminution of mitochondrial membrane potential, no significant correlation between these parameters and urinary As was detected. CONCLUSION: Our data indicate that As seems to have a relevant and complex effect on nTreg cells.

Abnormal eating attitudes in Mexican female students: a study of prevalence and sociodemographic-clinical associated factors.

The objective of the study was to determine the prevalence of abnormal eating attitudes (AEA) in Mexican high school and university students in the city of San Luis Potosí, Mexico. By means of a transversal study with a weighted, random and multistage sampling process, we analyzed a representative sample of female students (N= 2006). The instrument was the Eating Disorder Inventory-2 (EDI-2), validated in Mexican population and a questionnaire of sociodemographic data. The prevalence of AEA was 12.6% and its frequency was significantly higher in high school than in university students. AEA cases were uniformly distributed among public and private institutions and a highly significant relationship between substances consumption and AEA was observed. A logistic regression model for AEA was obtained. Therefore, a profile of highly AEA was built based on sociodemographic data and a solid instrument validated in Mexican population, which can be employed as a screening and secondary prevention tool to design public health programs.

Differential control of cortical activity by the basal forebrain in rats: a role for both cholinergic and inhibitory influences.

Using microdialysis and high-performance liquid chromatography, we measured acetylcholine (ACh) release simultaneously from two cortical sites in anesthetized rats. One site was always in the somatosensory cortex, and the other was in either the visual or the motor cortex. After baseline measurements were obtained, selected sites in the basal forebrain (BF) were stimulated to increase ACh release. Some BF sites provoked more release in one microdialysis probe than in the other, suggesting some degree of corticotropic organization of the cholinergic projections from the BF. BF sites optimal for release from the visual cortex were separated from optimal sites for release from the somatosensory cortex by greater distances than were the best sites for release from the somatosensory and the motor cortex. Stimulation of a single BF site often provoked similar release from the latter two cortical areas. Electrical stimulation of the BF also modified cortical neuronal activity. Activation of some BF sites provoked an intense discharge of many neurons in the vicinity of the cortical recording electrode, and the same stimulus site in the BF provoked release of large amounts of ACh in the cortex. Stimulation of other BF sites produced strong inhibition of ongoing cortical activity and no increase in cortical ACh release. When other sites were stimulated, they had no effect or they generated stereotyped bursting patterns in the cortex without any observable effect on ACh release. BF sites that generated inhibition of cortical neural activity were generally located near the sites that activated the cortex and provoked release of ACh. These data suggest an elaborate control of the sensory cortex by a mechanism involving both gamma-aminobutyric acid-containing and cholinergic neurons of the BF.

Changes in cortical acetylcholine release in the rat during day and night: differences between motor and sensory areas.

By sampling simultaneously from two microdialysis probes placed in the left and right hindlimb somatosensory cortex, or in the somatosensory and visual or in the somatosensory and motor cortices, we compared the release of acetylcholine in functionally different regions. Samples were taken hourly from freely moving, adult male Sprague-Dawley rats for periods of 10-24h. A generalized increase in acetylcholine release occurred in all cortical regions with the transition to the night-time period of wakefulness and activity; however, the change was significantly greater in the two sensory regions (56%) than in the motor cortex (20%). Decrements in release during the active period seldom decreased the amount released below the values observed during sleep. During the active period, the amount of acetylcholine released in the somatosensory cortex was strongly correlated with the amount released in the contralateral somatosensory region and was only slightly less well correlated with the amount released in either the visual or motor cortex. The correlation between release in the somatosensory and motor cortex was not present during the day, when rats habitually sleep. These data confirm that a global change in the level of acetylcholine release occurs with a transition in behavioural state; however, because the change is not equal in all areas and, because the correlation between motor and sensory cortex can be uncoupled, it seems likely that there are additional mechanisms available for independent control of acetylcholine release within specific cortical regions.

Effects of oral exposure to mining waste on in vivo dopamine release from rat striatum.

Several single components of mining waste (arsenic, manganese, lead, cadmium) to which humans are exposed at the mining area of Villa de la Paz, Mexico, are known to provoke alterations of striatal dopaminergic parameters. In this study we used an animal model to examine neurochemical changes resulting from exposure to a metal mixture. We used microdialysis to compare in vivo dopamine release from adult rats subchronically exposed to a mining waste by oral route with those from a control group and from a sodium arsenite group (25 mg/kg/day). We found that arsenic and manganese do accumulate in rat brain after 2 weeks of oral exposure. The mining waste group showed significantly decreased basal levels of dihydroxyphenylacetic acid (DOPAC; 66.7 +/- 7.53 pg/ microl) when compared to a control group (113.7 +/- 14.3 pg/ microl). Although basal dopamine release rates were comparable among groups, when the system was challenged with a long-standing depolarization through high-potassium perfusion, animals exposed to mining waste were not able to sustain an increased dopamine release in response to depolarization (mining waste group 5.5 +/- 0.5 pg/ microl versus control group 21.7 +/- 5.8 pg/ microl). Also, DOPAC and homovanillic acid levels were significantly lower in exposed animals than in controls during stimulation with high potassium. The arsenite group showed a similar tendency to that from the mining waste group. In vivo microdialysis provides relevant data about the effects of a chemical mixture. Our results indicate that this mining waste may represent a health risk for the exposed population.

In vivo hydroxyl radical formation after quinolinic acid infusion into rat corpus striatum.

We studied the effect of an acute infusion of quinolinic acid (QUIN) on in vivo hydroxyl radical (.OH) formation in the striatum of awake rats. Using the microdialysis technique, the generation of.OH was assessed through electrochemical detection of the salicylate hydroxylation product 2,3-dihydroxybenzoic acid (2,3-DHBA). The .OH extracellular levels increased up to 30 times over basal levels after QUIN infusion (240 nmol/microl), returning to the baseline 2 h later. This response was attenuated, but not abolished, by pretreatment with the NMDA receptor antagonist MK-801 (10 mg/kg, i.p.) 60 min before QUIN infusion. The mitochondrial toxin 3-nitropropionic acid (3-NPA, 500 nmol/microl) had stronger effects than QUIN on .OH generation, as well as on other markers of oxidative stress explored as potential consequences of .OH increased levels. These results support the hypothesis that early .OH generation contributes to the pattern of toxicity elicited by QUIN. The partial protection by MK-801 suggests that QUIN neurotoxicity is not completely explained through NMDA receptor overactivation, but it may also involve intrinsic QUIN oxidative properties.

Daily changes in the release of acetylcholine from rat primary somatosensory cortex.

Using microdialysis, acetylcholine (ACh) release was measured in the somatosensory cortex of 14 rats over a 24-h period. The release of ACh was 0.195 pmol/min during the day and 0.344 pmol/min at night. The length of exposed dialysis membrane within the cortex was an important source of variability in the absolute amounts of ACh collected. Even after rejecting some cases where the membrane contacted only the superficial cortical layers, this factor accounted for 25% of the variation of absolute amounts collected in different animals. After correcting for the length of exposed membrane, the release of ACh was shown to increase 52% at night during the time when the animals were awake, feeding and grooming. Variability in the measures of ACh release obtained during periods of activity was greater than its variability during periods of inactivity. These data were interpreted in the context of several hypothesized roles for ACh in sensory cortex.

The effects of sodium arsenite exposure on behavioral parameters in the rat.

Arsenic is a metalloid widely present in the environment. It is found in well water, soil, and air, and is also released from mining residues and industrial debris, among other anthropogenic sources. It has been previously reported that the content of catecholamines in striatum, hippocampus, and other cerebral regions changes in mice and rats exposed to arsenic. Few studies have examined behavioral alterations after intoxication with arsenic, and both increased and decreased locomotor activity, as well as learning deficits, have been described. In order to characterize the behavioral alterations induced by arsenic exposure, we exposed adult male Sprague-Dawley rats to 5, 10, and 20 mg/kg of arsenic by intragastric route for 2 or 4 weeks. Exposed rats showed reduced locomotor activity, which returned to control levels at the end of the intoxication period. We also found an increase in the number of errors in an egocentric task, alterations in monoamine content in midbrain and cortex, and increases in arsenic brain concentration, which were related to time of the exposure but not dose. These results indicate that short-term arsenic exposure induces neural and behavioral changes that may reflect a neurotoxic effect, and that these alterations are correlated to dose, time of exposure, and experimental conditions.

The effects of arsenic exposure on the nervous system.

Arsenic (As) is a common environmental contaminant widely distributed around the world. Human exposure to this metalloid comes from well water and contaminated soil, from fish and other sea organisms rich in methylated arsenic species, and from occupational exposure. It has been reported that human arsenic exposure causes several health problems such as cancer, liver damage, dermatosis, and nervous system disturbances such as polyneuropathy, EEG abnormalities and, in extreme cases, hallucinations, disorientation and agitation. Although there is evidence that arsenic exposure has a toxic effect on the nervous system there are few studies that address this issue. The purpose of this review is to describe what is presently known about the effects of arsenic compounds on the nervous system in humans and rodents and to discuss its possible mechanisms of action.

Effects of arsenite on central monoamines and plasmatic levels of adrenocorticotropic hormone (ACTH) in mice.

We studied the effects of chronic arsenic exposure on brain monoamines and plasma levels of adrenocorticotropic hormone (ACTH) of mice. After weaning, mice received arsenic (0, 20, 40, 60 or 100 ppm) in drinking water over a period of 9 weeks. Monoamine content was quantified in different brain regions, arsenic was quantified in brain tissue and ACTH levels in plasma. Brain arsenic concentrations up to 200 ng/g showed a significant correlation with exposure levels and produced slight modifications in regional monoamine levels. ACTH plasma levels were significantly associated with norepinephrine (NE) concentrations in the medulla and pons, but not with hypothalamic NE levels. ACTH levels were significantly higher in the group exposed to 20 ppm. Dopamine showed significant dose-related decreases in the hypothalamus. These results show that chronic sodium arsenite exposure produces changes in central monoamines, which are not associated on a dose-dependent basis with major alterations in plasma ACTH.

Methylmercury increases glutamate extracellular levels in frontal cortex of awake rats.

A current hypothesis about methylmercury (MeHg) neurotoxicity proposes that neuronal damage is due to excitotoxicity following glutamate uptake alterations in the astrocyte. By sampling from a microdialysis probe implanted in the frontal cortex of adult Wistar rats, we measured the effects of acute exposure to either 10 or 100 microM MeHg through the microdialysis probe, on glutamate extracellular levels in 15 awake animals. After baseline measurements, the perfusion of MeHg during 90 min induced immediate and significant elevations in extracellular glutamate at 10 microM (9.8-fold, P<.001) and at 100 microM (2.4-fold, P=.001). This in vivo demonstration of increments of extracellular glutamate supports the hypothesis that dysfunction of glutamate neurotransmission plays a key role in MeHg-induced neural damage.

Behavioral effects of exposure to endosulfan and methyl parathion in adult rats.

Endosulfan (ES) and methyl parathion (MP) are widely used in Latin America, and simultaneous exposure to both products is documented. This exposure may have effects on the nervous system because their targets include the GABAergic and cholinergic systems, which are main modulators of neuronal excitability in the cortex and hippocampus. We tested whether low-level, repeated exposure of adult rats to commercial formulations containing ES and MP disrupts spatial learning in the water maze. Five groups of eight animals received subcutaneously appropriate dilutions of the commercial formulations to yield the following treatments during 10 days: saline, 25 mg/kg ES, 2 mg/kg MP (MP(2)), 25 mg/kg ES plus 1 mg/kg MP (ES+MP(1)) and 25 mg/kg ES plus 2 mg/kg MP (ES+MP(2)). In addition, markers of neurological function, renal and hepatic damage were explored as potential consequences of exposure. In the absence of overt toxicity, the groups exposed to the ES plus MP showed significantly longer escape latencies, higher number of failures to reach the platform and more time in the periphery of the tank than the control and single-exposed groups. This finding shows that commercial formulations of ES and MP have marginal effects when administered individually but can produce behavioral alterations when given in combination.

Effects of lead-arsenic combined exposure on central monoaminergic systems.

Lead acetate (116 mg/kg/day), arsenic (11 or 13.8 mg/kg/day as sodium arsenite), a lead-arsenic mixture or vehicle were administered to adult mice through gastric intubation during 14 days. Then, the regional content of norepinephrine (NE), dopamine (DA), serotonin (5-HT), 3,4 dihydroxyphenyl-acetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HIAA), arsenic, and lead were quantified. Compared with the accumulation after single element exposures, the mixture elicited a higher accumulation of lead and a lower arsenic accumulation in the brain. Compared to controls, lead induced only an augmentation of DOPAC (200%) in the hypothalamus. By contrast, the mixture provoked increases of DOPAC in the hypothalamus (250%), DA and 5-HIAA in the striatum (67 and 187%, respectively) and NE decreased in the hypothalamus (45%). Although these alterations were similar to those produced by arsenic alone, the mixture provoked a 38% decrease of NE in the hippocampus and increases of 5-HT in midbrain and frontal cortex (100 and 90%, respectively) over control values, alterations that were not elicited by either metal alone. These results demonstrate an interaction arsenic/lead on the central monoaminergic systems of the adult mouse.

Low-level subchronic arsenic exposure from prenatal developmental stages to adult life results in an impaired glucose homeostasis.

We evaluated how low-level (3 ppm) subchronic inorganic arsenic (iAs) exposure from prenatal developmental stages until adult life affects glucose homeostasis. Biochemical parameters of glucose and lipid metabolism, pancreatic insulin and glycosylated haemoglobin were determined in 4-month-old female offspring of adult Wistar rats. Pancreatic histology was also performed. Statistical comparisons between control and iAs-treated groups were performed by unpaired two-tailed Student's t-test. Statistical significance was set at p<0.05. We found that iAs treatment resulted in an impaired glucose tolerance test, suggestive of impaired glucose metabolism. This group was found to have hyperglycaemia and high levels of HOMA-IR, glycosylated haemoglobin, cholesterol and pancreatic insulin compared to control rats. However, plasma insulin, triglycerides and high-density lipoprotein cholesterol were not different from control rats. Moreover, ß-cell damage found in iAs-treated rats consisted of cells with a nucleus with dense chromatin and predominance of eosinophilic cytoplasm, as well as changes in the pancreatic vasculature. The current study provided evidence that subchronic iAs exposure at 3 ppm from prenatal developmental stages to adult life resulted in damage to pancreatic ß cells, affected insulin secretion and demonstrated altered glucose homeostasis, thus supporting a causal association between iAs exposure and diabetes.

Decreased nitric oxide markers and morphological changes in the brain of arsenic-exposed rats.

Epidemiological studies demonstrate an association between chronic consumption of arsenic contaminated water and cognitive deficits, especially when the exposure takes place during childhood. This study documents structural changes and nitrergic deficits in the striatum of adult female Wistar rats exposed to arsenic in drinking water (3 ppm, approximately 0.4 mg/kg per day) from gestation, throughout lactation and development until the age of 4 months. Kainic acid injected animals (10mg/kg, i.p.) were also analyzed as positive controls of neural cell damage. Morphological characteristics of cells, fiber tracts and axons were analyzed by means of light microscopy as well as immunoreactivity to neuronal nitric oxide synthase (nNOS). As nitrergic markers, nitrite/nitrate concentrations, nNOS levels and expression of nNOS-mRNA were quantified in striatal tissue. Reactive oxygen species (ROS) and lipid peroxidation (LPx) were determined as oxidative stress markers. Arsenic exposure resulted in moderate to severe alterations of thickness, organization, surrounding space and shape of fiber tracts and axons, while cell bodies remained healthy. These anomalies were not accompanied by ROS and/or LPx increases. By contrast, except the expression of nNOS-mRNA, all nitrergic markers including striatal nNOS immunoreactivity presented a significant decrease. These results indicate that arsenic targets the central nitrergic system and disturbs brain structural organization at low exposure levels.

Changes in extracellular levels of dopamine metabolites in somatosensory cortex after peripheral denervation.

This study examined the effects of a nerve transection on monoamine release from primary somatosensory cortex. The technique of microdialysis was employed to sample extracellular levels of norepinephrine (NE), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HIAA) and homovanillic acid (HVA) in the barrel field of freely moving rats following the surgical transection of the contralateral infraorbital nerve. Microdialysates obtained 3, 4, and 5 days after deafferentation were analyzed using high-performance liquid chromatography with electrochemical detection. We found a significant increase in the release of the dopamine metabolites, DOPAC and HVA from the deafferented cortex. Three days after deafferentation the release of DOPAC was three-fold higher in the deafferented than in the control animals, and remained about 100% higher in the next two days in this group of animals. The release of HVA showed a gradual increase following the deafferentation procedure, since a 92% larger value on day 3 increased to a 338% difference on day 5. On the other hand, the release rate of NE and the levels of the serotonin metabolite 5-HIAA were not significantly affected by the deafferentation procedure. These results are discussed in the context of the possible participation of dopamine in the reorganization of the deafferented somatosensory cortex.

[A method for assessing health risks in mining sites]. / Un método para la evaluación de riesgos para la salud en zonas mineras.

OBJECTIVE: Considering the health risk associated with mining areas, in this work a methodology for the health assessment of this kind of hazardous sites is proposed. MATERIAL AND METHODS: The methodology includes a toxicological assessment, an environmental monitoring of metals, and the exposure assessment of the high risk population. The scheme was evaluated in the mining area of Villa de la Paz, San Luis Potosi, Mexico. The toxicological studies were done in rats treated with mining waste, biomarkers of effect for liver and central nervous tissue were analyzed. Metals levels in surface soil, household dust and water were studied. Finally, urinary arsenic was quantified in children. RESULTS: Neurotoxicity and hepatotoxicity of the mining waste were shown in rats. Then, arsenic and lead levels were analyzed in surface soil, household dust, and water. In all three media, exposure points, heavily contaminated with both metals, were localized. Finally, high levels of urinary arsenic were found in children living in the vicinity of the mine. CONCLUSIONS: Taking into account all these results, the Mexican authorities concluded that a high health risk is present in Villa de la Paz, and a remediation program is in progress.

Exposure to arsenic and lead and neuropsychological development in Mexican children.

This cross-sectional study examined the effects of chronic exposure to lead (Pb), arsenic (AS) and undernutrition on the neuropsychological development of children. Two populations chronically exposed to either high (41 children) or low (39 children) levels of As and Pb were analyzed using the Wechsler Intelligence Scale for Children, Revised Version, for México (WISC-RM). Geometric means of urinary arsenic (AsU) and lead in blood (PbB) were 62.9+/-0.03 (microgAs/g creatinine) and 8.9+/-0.03 (microg/dl) for the exposed group and 40.2+/-0.03 (microgAs/g creatinine) and 9.7+/-0.02 (microg/dl) for the reference group. The height for age index (HAI) was used as an indicator of chronic malnutrition and sociodemographic information was obtained with a questionnaire. Lead and arsenic were measured by atomic absorption spectrophotometry. Data on full, verbal, and performance intelligence quotients (IQ) scores, long-term memory, linguistic abstraction, attention span, and visuospatial organization were obtained through the WISC-RM. After controlling for significant potential confounders verbal IQ (P<0.01) decreased with increasing concentrations of AsU. The HAI correlated positively with full-scale and performance IQ (P<0.01). Higher levels of AsU were significantly related to poorer performance on WISC-RM factors examining long-term memory and linguistic abstraction, while lower scores in WISC-RM factors measuring attention were obtained at increasing values of PbB. Our results suggest that exposure to As and chronic malnutrition could have an influence on verbal abilities and long-term memory, while Pb exposure could affect the attention process even at low levels.