Lateral Prefrontal Theta Oscillations Reflect Proactive Cognitive Control Impairment in Males With Attention Deficit Hyperactivity Disorder

Attention Deficit Hyperactivity Disorder (ADHD) is a common neuropsychiatric disorder in which children present prefrontal cortex (PFC) related functions deficit. Proactive cognitive control is a process that anticipates the requirement of cognitive control and crucially depends on the maturity of the PFC. Since this process is important to ADHD symptomatology, we here test the hypothesis that children with ADHD have proactive cognitive control impairments and that these impairments are reflected in the PFC oscillatory activity. We recorded EEG signals from 29 male children with ADHD and 25 typically developing (TD) male children while they performed a Go-Nogo task, where the likelihood of a Nogo stimulus increased while a sequence of consecutive Go stimuli elapsed. TD children showed proactive cognitive control by increasing their reaction time (RT) concerning the number of preceding Go stimuli, whereas children with ADHD did not. This adaptation was related to modulations in both P3a potential and lateral prefrontal theta oscillation for TD children. Children with ADHD as a group did not demonstrate either P3a or theta modulation. But, individual variation in theta activity was correlated with the ADHD symptomatology. The results depict a neurobiological mechanism of proactive cognitive control impairments in children with ADHD.

Impact of acute stress on itch sensation and scratching behaviour in patients with atopic dermatitis and healthy controls

BACKGROUND

Patients with atopic dermatitis (AD) often report that stress aggravates their itch. However, no study has investigated if and how acute stress influences itch sensation and scratching behaviour in these patients.

OBJECTIVES

We evaluated the impact of acute stress on experimentally induced cowhage itch perception and scratching behaviour in 16 healthy subjects and 15 patients with AD.

METHODS

The Trier Social Stress Test (TSST) was used to induce acute stress. The itch sensation, provoked by applying cowhage to the forearms, and off-site scratching behaviour (not directed at the cowhage application site) were compared before and after performing the TSST or the control condition (watching a video of landscape scenes).

RESULTS

In patients with AD, stress induced by TSST caused a significant reduction of cowhage-evoked itch but significantly increased off-site scratching behaviour. Such changes in itch perception and scratching behaviour were not observed in healthy controls. In addition, a significant positive correlation was noted between stress induced by TSST and clinical severity of eczema.

CONCLUSIONS

We speculate that psychological stress increases spontaneous scratching in patients with AD, which may enhance the vicious cycle of itching and scratching, resulting in aggravation of the skin eczema. These results provide new insights on the mechanism of acute stress-related exacerbation of itch in patients with AD.

Ethanol production from eucalyptus wood hemicellulose hydrolysate by Pichia stipitis

Ethanol production was evaluated from eucalyptus wood hemicellulose acid hydrolysate using Pichia stipitis NRRL Y-7124. An initial lag phase characterized by flocculation and viability loss of the yeast inoculated was observed. Subsequently, cell regrowth occurred with sequential consumption of sugars and production of ethanol. Polyol formation was detected. Acetic acid present in the hydrolysate was an important inhibitor of the fermentation, reducing the rate and the yield. Its toxic effect was due essentially to its undissociated form. The fermentation was more effective at an oxygen transfer rate between 1.2 and 2.4 mmol/L h and an initial pH of 6.5. The hydrolysate used in the experiences had the following composition (expressed in grams per liter): xylose 30, arabinose 2.8, glucose 1.5, galactose 3.7, mannose 1.0, cellobiose 0.5, acetic acid 10, glucuronic acid 1.5, and galacturonic acid 1.0. The best values obtained were maximum ethanol concentration 12.6 g/L, fermentation time 75 h, fermentable sugar consumption 99% ethanol yield 0.35 g/g sugars consumed, and volumetric ethanol productivity 4 g/L day. (

[Prevalence of asthma in Chilean students. Descriptive study of 24,470 children. ISAAC-Chile]

BACKGROUND

There is little information about the prevalence of asthma in Latin American children.

AIM

To determine the prevalence of asthma among Chilean school age children.

SUBJECTS AND METHODS

The prevalence of respiratory symptoms related to asthma in schoolchildren aged 7 and 13 years, coming from South Santiago, Central Santiago, Valdivia and Punta Arenas, was determined using the methodology of the International Study on Asthma and Allergies in Childhood (ISMC). A random sample of school children aged 6-7 and 13-14 years from each locality was selected. This resulted in 24)470 surveyed children (11,723 aged 6-7 years and 12,747 aged 13-14 years).

RESULTS

The current prevalence of wheezing ("wheezing in the last 12 months") ranged from 16.5% to 20.0% in children aged 67 years, and from 6.8% to 11.7% in children aged 13-14 years. The cumulative prevalence of asthma ("asthma ever"), ranged from 9.7% and 16.5% in the 6-7 years group and from 7.3% to 12.4% in those aged 13-14 years.

CONCLUSIONS

This study found much higher figures for prevalence of respiratory symptoms related to asthma in school children than those previously reported in this country, with a significant variability between centers (p < 0.05). The prevalence of asthma in Chilean schoolchildren is as high and variable as that reported in industrialized countries.

Occurrence of heterotrophic bacteria and fungi in an aviation fuel handling system and its relationship with fuel fouling

Clean, dry and contaminant-free fuel is necessary for safe and economical aircraft operation. Microbial growth in aviation fuel handling systems can alter the quality of the product. This paper reports the occurrence of heterotrophic bacteria and fungi in a handling system of jet A-1 aviation turbine fuel. A total of 350 samples were collected during 1990-1996. The aerobic microorganisms in fuel samples were mainly fungi, 85% of samples containing < or = 100 cfu/l (range 0 (< 1 cfu/l) to 2000 cfu/l). The predominant fungi were Cladosporium and Aspergillus. Water was observed mainly in samples extracted from the drainage pipes of two tanks used frequently as intermediate storage tanks. The aerobic heterotrophic microorganisms found in water samples were mostly bacteria, counts varying from 100 to 8.8 x 10(7) cfu/ml, with 85% of samples containing 10(4)-10(7) cfu/ml. There was a preponderance of Pseudomonas spp. Bacterial contaminants belonging to the genus Flavobacterium and Aeromonas were also identified. Sulphate reducing bacteria were detected in 80% of water samples. It was not possible to assign a maximum microbial contamination level above which maintenance is required and it is suggested that analysis of successive samples from the same site are necessary for this purpose. Microbial sludges produced in the laboratory and collected from a contaminated tank bottom were analysed chemically. The data are presented and discussed. Samples collected from the supply pipes of tanks and refueller trucks during the period surveyed always met the standard specifications.

Correlation between the clinical classification of bronchial asthma severity and the methacholine test in children

The purpose of this study was to validate the Methacholine Bronchial Challenge Test in its different degrees and to compare them with the different clinical classifications of bronchial asthma. Fifty-four child asthmatic patients over 6 years of age from the Respiratory Outpatient Clinic at La Union Hospital (Chile) were submitted to the clinical classification of bronchial asthma and later to the Methacholine Bronchial Challenge Test, which classified the children as mildly, moderately or severely hyperreactive to the test. In mildly asthmatic children, the Methacholine Test showed both a high sensitivity (100%) and specificity (92.3%). In moderately asthmatic children, the sensitivity decreased to 84.5%, whilst the specificity was maintained (92.3%). In severely asthmatic children, however, the sensitivity decreased to 53.5%, whilst the specificity increased 97.2%. The latter could be explained as a consequence of the previous exposure of this group of children to either inhaled or oral corticoids. According to our experience, the Methacholine Test is not only useful for the diagnosis of bronchial hyperreactivity in dubious cases, but also for contributing together with the clinical findings to the adequate classification of these patients.

[Biodegradability in soil of residual hydrocarbons in petroleum tank bottoms]

Biodegradability of hydrocarbons on soils can be applied to the treatment of residues (land treatment) from petroleum refinery as well as the cleaning of contaminated soils (bioremediation). In this paper we have studied the biodegradability of hydrocarbons from petroleum tank bottom sludges on soil by the autochthonous microbial community. Lab assays were conducted in 1l-beakers under the following conditions: hydrocarbon load 5.3%, total aerobic microorganisms 2.7 x 10(7) CFU/g, hydrocarbon degrading microorganisms (HDM) 2.5 x 10(5) cells/g, incubation temperature 25 degrees C, pH 7.0-7.6, and moisture 10-15%. Soil had the following composition: sand 25%, silt 15%, and clay 20%. Different levels and kind of fertilizers were evaluated. Fertilization increased the rate and the quantity of hydrocarbons degraded. It was degraded about 40% of hydrocarbons in 30-90 days according to the fertilization effected. During biodegradation, the HDM increased 760 times. Assays conducted outdoor on trays showed a similar limit of biodegradation. Changes with time in the fungi population, hydrocarbon class, carbon level, and saturated hydrocarbon profiles were measured too. Data suggests the use of microorganisms having a greater metabolic capacity, specially to degrade those hydrocarbon classes that they have shown to be more resistant to biodegradation (aromatics, resins and asphaltenes).

Ten-year follow-up in pediatric patients with allergic bronchial asthma: evaluation of specific immunotherapy

Specific immunotherapy as a treatment for bronchial asthma has been a controversial field. A collaborative study was designed in an attempt to further define the possible contribution of specific immunotherapy in a pediatric population. One hundred and sixty-six patients were treated with immunotherapy and 248 received no immunotherapy. The results were compared during 10 years of follow-up in both groups. There was a significant decrease in the number of acute crisis in the treated group (p < 0.05). However, no differences were seen in the number of hospital admissions or in the quality of life between the treated and untreated groups. The treated group required significantly fewer drugs (p < 0.05). Thus, it is probable that the untreated group shows the same clinical indexes as the treated group due to their increased use of medication. Specific immunotherapy represents an effective treatment that changes the natural course of allergic bronchial asthma in pediatric patients.

[Hodgkin's disease in children. Modified COPP combined treatment and radiotherapy in advanced stages]

Twenty two children, under 15 years of age, from southern Chile's Tenth Region, with advanced stages of Hodgkin's disease (8 III-A, 6 III-B and 8 IV-B) were treated with chemotherapy (modified COPP protocol) and radiotherapy between 1976 and 1985 at Valdivia's Regional Hospital. Overall survival rate was 77.3% and disease-free survival rate was 64.5% after a follow-up period from 3 to 13 years (median 70 months). Five patients died during the first two years. One relapsed 10 years after beginning of therapy, but achieved a second complete remission. The survival rate in patients with lymphocytic depletion type (5 cases) was 20.0%, whereas that of the mixed cellularity type (14 cases) was 92.9% (p less than 0.01). No cases of second neoplasms related to chemotherapy and radiotherapy were seen in this series.