Self-regulation in the pre-adolescent brain.

Self-regulation refers to the ability to monitor and modulate emotions, behavior, and cognition, which in turn allows us to achieve goals and adapt to ever changing circumstances. This trait develops from early infancy well into adulthood, and features both low-level executive functions such as reactive inhibition, as well as higher level executive functions such as proactive inhibition. Development of self-regulation is linked to brain maturation in adolescence and adulthood. However, how self-regulation in daily life relates to brain functioning in pre-adolescent children is not known. To this aim, we have analyzed data from 640 children aged 8-11, who performed a stop-signal anticipation task combined with functional magnetic resonance imaging, in addition to questionnaire data on self-regulation. We find that pre-adolescent boys and girls who display higher levels of self-regulation, are better able to employ proactive inhibitory control strategies, exhibit stronger frontal activation and more functional coupling between cortical and subcortical areas of the brain. Furthermore, we demonstrate that pre-adolescent children show significant activation in areas of the brain that were previously only associated with reactive and proactive inhibition in adults and adolescents. Thus, already in pre-adolescent children, frontal-striatal brain areas are active during self-regulatory behavior.

Ventral striatum is related to within-subject learning performance.

Learning from feedback involves a network of various cortical and subcortical regions. Although activation in this network has been shown to be especially strong in successful learners, it is currently unclear which of these regions are related to within-subject variation in learning performance. To this aim, 21 subjects performed a probabilistic feedback-learning task consisting of multiple independent Learning blocks and non-learning Control blocks, while functional magnetic resonance imaging data were acquired. In agreement with previous studies, activation in anterior, lateral and medial left prefrontal cortex, insula and superior and inferior parietal cortical regions were found when contrasting Learning and Control blocks. Furthermore, activation in the supplementary motor area, anterior cingulate cortex and bilateral striatum was associated specifically with the learning phase and not the application phase during Learning blocks. Finally, activation only in the ventral striatum was associated with within-subject learning performance across the Learning blocks. Taken together, these latter two results are argued to provide the answer to the main research question: ventral striatum activation is associated with within-subject variations in learning performance. The ventral striatum appears to play a vital role in learning by adjusting behavior based on feedback.

Control of maximal and submaximal vertical jumps.

PURPOSE: It was investigated to what extent control signals used by human subjects to perform submaximal vertical jumps are related to control signals used to perform maximal vertical jumps. METHODS: Eight subjects performed both maximal and submaximal height jumps from a static squatting position. Kinematic and kinetic data were recorded as well as electromyographic (EMG) signals from eight leg muscles. Principal component analysis was used analyze the shape of smoothed rectified EMG (SREMG) histories. Jumps were also simulated with a forward dynamic model of the musculoskeletal system, comprising four segments and six muscles. First, a maximal height jump was simulated by finding the optimal stimulation pattern, i.e., the pattern resulting in a maximum height of the mass center of the body. Subsequently, submaximal jumps were simulated by adapting the optimal stimulation pattern using strategies derived from the experimental SREMG histories. RESULTS: SREMG histories of maximal and submaximal jumps revealed only minor differences in relative timing of the muscles between maximal and submaximal jumps, but SREMG amplitude was reduced in the biarticular muscles. The shape of the SREMG recordings was not much different between the two conditions, even for the biarticular muscles. The simulated submaximal jump resembled to some extent the submaximal jumps found in the experiment, suggesting that differences in control signals as inferred from the experimental data could indeed be sufficient to get the observed behavior. CONCLUSIONS: The results fit in with theories on the existence of generalized motor programs within the central nervous system, the output of which is determined by the setting of parameters such as amplitude and relative timing of control signals.

Headache in adolescents in Dutch general practice.

We set out to describe the occurrence of headache in adolescents in general practice, the diagnoses made, the referrals to specialised care and the role of psychosocial problems in idiopathic headache. Data from the Dutch national survey of morbidity and interventions in general practice were used. The practice population (103 practices) comprised 37,187 children aged 12-18 years. In 650 episodes headache was a reason for encounter. The incidence of headache as presented to the GP was 69.9 per 1000 person years. The incidence in girls was twice as high as in boys. Half of the episodes with headache complaints were related to an infectious disease. The incidence rate of idiopathic headache was 18.0 per 1000 person years. Eight percent of all headache episodes were diagnosed as a psychosocial problem. Of all episodes, 25% percent were diagnosed as idiopathic headache (i.e. headache as symptom diagnosis, tension headache or migraine). Of these episodes, 21% were associated with an underlying psychosocial problem. Referrals were made by the GP in three percent of all headache episodes and four percent of idiopathic headache episodes. Headache in adolescents is a common reason for visiting a general practice. The symptom is often associated with an infectious disease. The GP is aware of underlying psychosocial problems. Only few children are referred for specialist care.

Headache in children in Dutch general practice.

AIM: To describe the occurrence of headache in general practice, the diagnoses made in general practice, and the management. METHOD: Data from the Dutch national survey of morbidity and interventions in general practice were used. The practice population (103 practices) comprised 63,753 children aged 0-14 years. RESULTS: In 634 episodes, headache was a reason for encounter. The incidence of headache presented to the general practitioner was 40.2 per 1000 person years. More than half of the episodes were related to an infectious disease, among which upper respiratory tract infections predominated. The incidence rate of the diagnosis idiopathic headache was 7.3 episodes per 1000 person years. The incidence increased with age and was higher in girls than in boys. In only 12% of cases of idiopathic headache were special investigations carried out, mostly blood examinations. Medication was prescribed in 27% of all episodes of idiopathic headache. In the absence of an infectious disease, many headache episodes were associated with psychosocial problems. Family problems and school problems were mentioned most often. CONCLUSION: Headache in children as reason for encounter is a common problem in general practice, often associated with an infectious disease. When confronted with a child with idiopathic headache, the general practitioner should be aware of a possible psychosocial component.

Force-time characteristics of the rowing stroke and corresponding physiological muscle adaptations.

The force-time characteristics of the rowing stroke was examined in a coxless pair. Sixteen highly trained rowers were evaluated in their usual training positions (stroke or bow). Stroke rowers had higher stroke speed and stroke force in the first part of the stroke than bow rowers. This finding was more prominent during competition speed rowing than during endurance training. Higher blood lactate levels and lower base excess were found at both speeds in stroke rowers. During and incremental ergometer rowing test, lactate performance curves were shifted to the left in the stroke rowers. Analysis of morphometric data in the left deltoid muscle demonstrated higher FT fiber content and lower oxidative fiber capacity and fiber areas in the stroke rowers. The results demonstrate adaptation to years of training in a specific boat position.

Two-colour combination enzyme-linked immunosorbent assay for the simultaneous detection of HBV and HIV infection.

To reduce the cost, time and waste in screening for HIV and HBV infections a combined assay for HIV-1 and -2 antibodies and HBsAg has been developed. Monoclonal anti-HBs antibodies were co-immobilized with synthetic peptides representing immunodominant regions of HIV-1 and -2. The presence of anti-HIV antibodies in the samples was detected with alkaline phosphatase-labelled anti-human IgG and of HBsAg with horseradish peroxidase-labelled monoclonal anti-HBs antibodies by a sequential substrate reaction. In this assay, HBsAg was detectable in a concentration range between 0.25 and 0.30 U/ml and the results were available within 3 h. The specificity, tested on 5000 serum samples from blood donors after confirmation, was 99.8% for HBsAg and 99.5% for anti-HIV antibody detection. All serum samples taken from 600 HIV-1- and 115 HIV-2-infected individuals were correctly classified as reactive. The two-colour HBsAg-anti-HIV-1/-2 combination ELISA meets all the requirements of single parameter assays with regard to precision, stability and robustness.

Comparison of four anti-HIV screening assays which belong to different test generations.

There are three different test generations of enzyme-linked immunosorbent assays (ELISA) for the detection of human immunodeficiency virus (HIV) infection, depending on whether virus lysate, recombinant proteins or synthetic peptides are used as solid phase antigen. Four different assays, i.e., three sandwich ELISAs and one competitive test, were used to demonstrate differences between the three systems with regard to the content of different diagnostically relevant virus proteins. The sensitivities and specificities of these assays were compared by using 312 anti-HIV positive sera and 500 sera of healthy blood donors. The highest sensitivity and specificity were achieved by the competitive ELISA based on recombinant proteins, and by the sandwich ELISA based on synthetic peptides.

Cu/Zn superoxide dismutase quantification from fetal erythrocytes--an efficient confirmatory test for Down's syndrome after maternal serum screening and sonographic investigations.

An enzyme immunoassay especially designed for the quantification of Cu/Zn superoxide dismutase (SOD) in erythrocytes has been applied to measure the SOD of outcomes with high risk for Down's syndrome. From 148 fetuses SOD was quantified from erythrocytes of umbilical vein blood and related to the number of cells, the content of haemoglobin (Hb), and to the haematocrit (Hc). Comparative studies between the SOD content of erythrocytes from the fetuses and their mothers resulted in similar SOD levels (14.09 +/- 1.20 for fetal and 14.48 +/- 1.63 for maternal cells) with a 1.84-fold smaller variance for fetal cells. The best differentiation between normal fetuses and fetuses with Down's syndrome resulted from the SOD/cell ratio followed by the SOD/Hb ratio. Fixing a cut-off value from the probability density functions that the method results in a specificity of 99.99 per cent, the sensitivity to detect cases of Down's syndrome was 99.71 per cent for the SOD/cell ratio, 70.92 per cent for the SOD/Hb ratio, and 60.21 per cent for the SOD/He ratio. Nine cases with Down's syndrome were correctly diagnosed by the SOD/cell ratio determination. Eight of these were confirmed as free trisomy 21 by karyotype analysis and one was found to be a triploidy. The latter was not detected by the SOD/Hb and SOD/Hc ratios because of the one-third higher content of haemoglobin and the larger volume of the erythrocytes which resulted in ratios within the normal range.

Development of an immunoenzymometric assay for alpha 1-microglobulin and measurement of its serum concentration in normal and HIV-infected persons.

alpha 1-Microglobulin was purified from urine to a purity of 97.7% in a yield of 25.8%, and was used to produce antibodies in sheep. These antibodies, purified by affinity chromatography, were used to develop a rapid one-step and a two-step immunoenzymometric assay (IEMA). The equilibrium in the reaction between solid phase-adsorbed antibodies and antigen and between the antigen and enzyme-labelled antibodies was attained within 30 and 100 min, respectively. The one-step IEMA permits a good differentiation of low alpha 1-microglobulin concentrations after 30 min reaction time. Its detection limit is 0.35 micrograms/l, and its measurement range is between 0.5 and 100 micrograms/l. The IEMA correlates well with radial immunodiffusion (r = 0.973). The mean alpha 1-microglobulin serum concentration in women is insignificantly lower (33.2 mg/l) than in men (36.1 mg/l). In both sexes the alpha 1-microglobulin concentration increases with age. HIV-infected symptomless men have a significantly lower (15.9 mg/l) alpha 1-microglobulin concentration in serum than normal persons, whereas in AIDS patients it is significantly higher (45.5 mg/l).

Binding behaviour of antibodies reacting specifically with an immunodominant region of the transmembrane protein gp41 of HIV-1.

A highly conserved region of the transmembrane protein gp41 of the HIV-1 was found in which the amino acid sequence 606 to 620 was characterized as an immunodominant region. The binding behaviours of a human monoclonal antibody and of polyclonal specific antibodies in sera of HIV-infected persons to this particular sequence have been studied. In two sandwich-type ELISAs with synthetic peptides as antigen representing this region, sera of 312 HIV-infected persons at all stages could be clearly discriminated against 500 anti-HIV antibody negative sera of healthy blood donors.

Predictive value of various parameters for the antihypertensive effect of the beta blocker ICI 66,082 (1).

The antihypertensive effect of the new beta-blocker, ICI 66,082 was studied in 37 patients with renal or essential hypertension. A daily dose of 75 mg produced a significant antihypertensive effect and a further blood pressure decrease was obtained by increasing the daily dose up to 300 mg; at this treatment level, the antihypertensive effect averaged 29.4/24.0 mm Hg. Increasing the dose from 300 to 600 mg daily did not produce a significant additional blood pressure decrease. Six of the 37 patients retained fluid, producing a loss in the antihypertensive effect. No significant correlation was found between the percentage systolic blood pressure fall and the following parameters determined before therapy: systolic blood pressure and its variability, heart rate (at rest and after stimulation by exercise or isoproterenol), cardiac output and total peripheral resistance, renin concentration (at rest and after stimulation) and urinary excretion of catecholamines and derivates.