Mariana Bohns Michalowski

Effect of acute and repeated restraint stress on glucose oxidation to CO2 in hippocampal and cerebral cortex slices

It has been suggested that glucocorticoids released during stress might impair neuronal function by decreasing glucose uptake by hippocampal neurons. Previous work has demonstrated that glucose uptake is reduced in hippocampal and cerebral cortex slices 24 h after exposure to acute stress, while no effect was observed after repeated stress. Here, we report the effect of acute and repeated restraint stress on glucose oxidation to CO2 in hippocampal and cerebral cortex slices and on plasma glucose and corticosterone levels. Male adult Wistar rats were exposed to restraint 1 h/day for 50 days in the chronic model. In the acute model there was a single exposure. Immediately or 24 h after stress, the animals were sacrificed and the hippocampus and cerebral cortex were dissected, sliced, and incubated with Krebs buffer, pH 7.4, containing 5 mM glucose and 0.2 microCi D-[U-14C] glucose. CO2 production from glucose was estimated. Trunk blood was also collected, and both corticosterone and glucose were measured. The results showed that corticosterone levels after exposure to acute restraint were increased, but the increase was smaller when the animals were submitted to repeated stress. Blood glucose levels increased after both acute and repeated stress. However, glucose utilization, measured as CO2 production in hippocampal and cerebral cortex slices, was the same in stressed and control groups under conditions of both acute and chronic stress. We conclude that, although stress may induce a decrease in glucose uptake, this effect is not sufficient to affect the energy metabolism of these cells.

School dropout and conduct disorder in brazilian elementary school students

Objectives: To evaluate the association between DSM-IV conduct disorder (CD) and school dropout in a sample of students from the third and fourth elementary grades at state schools in the capital of the southernmost state of Brazil. Methods: In this case-control study, students that dropped out of schools (n = 44) and a control group who continued attending schools (n = 44) were assessed for CD and other prevalent mental disorders, using the Schedule for Affective Disorders and Schizophrenia for School Age Children, Epidemiological Version (K-SADS-E). Results: The prevalence of DSM-IV CD was significantly higher in the school-dropout group than in control subjects (P < 0.001), both in the entire sample and in a subsample including only subjects under age 12 years (P = 0.001). Also, the odds ratio (OR) for school dropout was significantly higher in the presence of DSM-IV CD, even after controlling for potential confounding factors (age, estimated IQ, school repetition, family structure, and income) (P < 0.01). Conclusion: Our results extend to children and young adolescents previous findings from studies of older adolescents, suggesting an association between school dropout and CD.

Effect of repeated restraint stress on memory in different tasks

The present study investigated the effect of repeated stress applied to female rats on memory evaluated by three behavioral tasks: two-way shuttle avoidance, inhibitory avoidance and habituation to an open field. Repeated stress had different effects on rat behavior when different tasks were considered. In the two-way active avoidance test the stressed animals presented memory of the task, but their memory scores were impaired when compared to all other groups. In the habituation to the open field, only the control group showed a significant difference in the number of rearings between training and testing sessions, which is interpreted as an adequate memory of the task. In the handled and chronically stressed animals, on the other hand, no memory was observed, suggesting that even a very mild repeated stress would be enough to alter habituation to this task. The performance in the inhibitory avoidance task presented no significant differences between groups. The findings suggest that repeated restraint stress might induce cognitive impairments that are dependent on the task and on stress intensity.

Estimated mental retardation and school dropout in a sample of students from state public schools in Porto Alegre, Brazil

OBJECTIVES: To assess the association between estimated Mental Retardation (MR) and school dropout in a sample of students of the third and fourth grades at state schools in Porto Alegre, the capital of the southernmost state of Brazil. METHOD: In this case - control study, students that dropped out from schools (n=44) and a control group who continued attending schools (n=44) had their intelligence quotient (IQ) determined by the vocabulary and cubes subtests of the Wescheler Intelligence Scale ¾ third edition (WISC¾III). Students with IQ lower than 70 were considered as potential cases of MR. Other prevalent mental disorders in this age range were assessed in both groups using the Schedule for Affective Disorders and Schizophrenia for School¾ Age Children, Epidemiological Version (K-SADS-E). RESULTS: The prevalence of potential MR was significantly higher in the dropped out group than in the control group (p<0.001). Odds ratio for school dropout was significantly higher in the presence of MR even after controlling for potentially confounding factors (age, conduct disorder, grade repetition, family structure and income) (p<0.01). CONCLUSION: Children with IQ lower than 70 (potential MR) were at higher risk for school dropout. These children need to be identified at school and specific educational strategies should be implemented to assure their inclusion in the learning process.

High prevalence of anemia in children and adult women in an urban population in southern Brazil.

This population-based study was designed to detect the prevalence of anemia in a healthy population of children (18 months to 7 years) and women (14 to 30 years) tested in 2006–2007 in the state of Rio Grande do Sul, Brazil as part of an effort to tackle this massive problem that still affects so many people in the XXI century. Anemia was defined according to the WHO. Capillary blood was measured and socioeconomic status was determined according to the Brazilian Association of Market Research Agencies. The median prevalence of anemia in 2198 children was 45.4% and in 1999 women 36.4%. Anemia decreased with age during childhood; although significantly more prevalent in lower classes individuals, it was also high in the upper classes. There are indirect evidences that the lack of iron supplementation and/or iron fortified food may play a role in it. Professionals and society wise measures of education have to be implemented in order to address possible biologic factors involved in childhood psychosocial development in southern Brazil.

Epinephrine effects on memory are not dependent on hepatic glucose release.

Abstract Epinephrine released or administered soon after a given training task modulates memory processes. Since epinephrine does not readily cross the blood–brain barrier, studies have suggested that some of the central effects of epinephrine might be mediated by peripheral release of glucose. These experiments examined the involvement of blood glucose levels in the posttraining effects of peripherally administered epinephrine. The effects of the administration of epinephrine (25 and 625 mg/kg) on memory of an inhibitory avoidance task were evaluated in fed and fasted rats (depleted glycogen stores in liver). Blood glucose levels after the task in each group were also measured. Female Wistar rats were divided in two groups. Fed and 48-h-fasted animals were submitted to the inhibitory avoidance task and received ip epinephrine or saline immediately after training. The test session was carried out 48 h after training. Epinephrine (25 or 625 mg/kg) caused an increased glycemia in fed rats, but no effect was observed in fasted animals. Administration of epinephrine 25 mg/kg induced a facilitation of memory, while epinephrine 625 mg/kg impaired retention (either in fasted or in fed animals). There was no relation between increased glycemia induced by epinephrine and its effects on memory, since this drug presented its classical effects independently of the previous state of the animal (fed or fasted). The results of the present study suggest that the effects of systemic released or administered epinephrine on memory processes are not dependent on hepatic glucose release.

Exposure to different intrauterine environments: implications for telomere attrition in early life

Abstract Objective: Studies focusing on telomere attrition in newborns and what factors could be involved in this issue are sparse; most reports have been in adult populations. Thereby, the aim of this study was to present an overview of what is currently known about the relationship between environmental exposure of the fetus during pregnancy and telomere length outcomes in early life. Methods: The MEDLINE (via PubMed) and Bireme databases were searched for studies published until 1 June 2016. Studies that reported telomere length measurement from birth to age 1 year were included. Results: Fifteen articles were selected that evaluated possible relationships between maternal smoking, hyperglycemia, hypertension, sleep apnea, psychological stress, folate concentration in early pregnancy, and radiation, in addition to small-for-gestational-age status and preterm birth. We found that sleep apnea, psychological stress, and folate concentration in early pregnancy were associated with telomere shortening in the newborn. No association was found with radiation, small-for-gestational-age status, or preterm birth. Results for maternal smoking, hyperglycemia, and hypertension were conflicting, and further studies should be considered. Conclusion: The actual clinical implications of these findings have yet to be investigated.