Overnight sleep duration and obesity in 2-5 year-old American Indian children.

BACKGROUND: Sleep has emerged as a potentially modifiable risk factor for obesity in children. OBJECTIVES: The purpose of this investigation was to evaluate the association between overnight sleep duration and obesity among American Indian (AI) children ages 2-5 years. METHODS: Data were examined from the baseline assessment of children enrolling in the Healthy Children, Strong Families study, which is a randomized lifestyle intervention trial in five diverse rural and urban AI communities nationally among children ages 2-5 years. Multivariable models were built to assess the relationship between sleep duration and BMI z-score while controlling for potential sociodemographic and behavioural covariates. RESULTS: Three hundred and ninety-eight children had sufficient data to be included in analysis. In multivariable models controlling for potential covariates, overnight sleep duration was significantly and inversely associated with BMI z-score (B = -0.158, t = -1.774, P = 0.006). Similarly, when controlling for covariates, children who slept 12 or more hours had significantly lower BMI z-scores compared with those who slept 8 to 10 h (P = 0.018) or less than 8 h (P = 0.035); the difference between 12+ hours and 10 to 12-h groups did not reach statistical significance (P = 0.073) but supported a linear relationship between overnight sleep duration and BMI. Weekday-to-weekend variability in overnight sleep duration was not associated with BMI z-score (B = 0.010, t = 0.206, P = 0.837). CONCLUSIONS: Overnight sleep duration is independently and inversely related to BMI z-score among AI children ages 2-5 years, even when controlling for important sociodemographic and obesogenic lifestyle factors. This represents the first report, to our knowledge, of sleep duration as a risk factor for obesity among AI children.

Event-related potentials in cross-modal divided attention in autism.

The behavior and event-related potentials (ERPs) of high functioning subjects with autism (Autism group) were contrasted with the results of normal controls (Control group) during a focused visual attention, a focused auditory attention and a visual/auditory divided attention task. Detecting targets by the Autism group in the cross-modal divided attention condition was more difficult (longer RTs, lower % of correct detections) than attending to one modality. However, both the Autism and Control groups performed all tasks above chance level. The slow negative wave (SNW) was the only negative component which reflected Focused vs Divided task effect in Controls, being largest to stimuli in single channel-focused attention, intermediate when attention was divided between targets of two modalities and smallest to unattended stimuli. Task effects were more evident in the positive peaks for the Autism group. No significant divided attention task effect was noted for P3b, although it was larger for attended than ignored stimuli, of normal morphology and only slightly decreased in size in the Autism group as compared to the Control group. The failure of the Autism group to modulate the slow negative wave in response to Focused/Divided/Ignored conditions in a normal manner, the presence of relatively normal morphology despite the reduced amplitude of the P3b and other positive components, together with the high level of correct target detections are discussed in the context of a selective inhibition deficit and an alternative mechanism of selective attention in autism.

Steroid modulation of the strychnine-sensitive glycine receptor.

Electrophysiological responses to glycine (0.25-5 mM) were obtained on preparations of rat optic nerve. The log dose-response curve for glycine was shifted to the left by a factor of 2 by 1 microM 20 alpha-dihydrocortisol and by a factor of about 1.5 by 1 microM alpha-cortol and 10 microM hydrocortisone. A similar effect was obtained with 100 microM chlormethiazole but the GABA-potentiating steroid alphaxalone (1 microM) was ineffective on responses to glycine. 20 alpha-Dihydrocortisol and chlormethiazole also appeared to increase the antagonistic potency of strychnine against glycine. These observations suggest that the active steroids and chlormethiazole increase the functional interaction of both glycine and strychnine with the glycine-gated chloride channel.

Differential antagonism by epipregnanolone of alphaxalone and pregnanolone potentiation of [3H]flunitrazepam binding suggests more than one class of binding site for steroids at GABAA receptors.

In rat brain membranes, the 3 alpha-hydroxy pregnane steroids, pregnanolone, allopregnanolone, alphaxalone and 5 beta-alphaxalone potentiated 1 nM [3H]flunitrazepam binding at the GABAA receptor, with maximal potentiations of 140-150% of control. The potencies of the 5 alpha isomers were greater than the 5 beta and the presence of an 11-keto group conferred lower potency. The potentiation produced by these steroids was antagonised by the 3 beta-OH isomers epipregnanolone, isopregnanolone and betaxalone (60 microM). The dose-effect curves for pregnanolone and allopregnanolone were shifted to the right, with no reduction in the maximal potentiation. In contrast, the maximal effect of alphaxalone and 5 beta-alphaxalone was reduced with no change in EC50. Alphaxalone (1 microM) caused an increase in the binding of [3H]flunitrazepam in the presence of maximal concentrations of pregnanolone or allopregnanolone. These results suggest multiple sites of action for neurosteroids in the brain.

Temperature and anion dependence of allosteric interactions at the gamma-aminobutyric acid-benzodiazepine receptor.

The temperature dependence of [3H]flunitrazepam ([3H]FNZ) binding to rat brain membranes was examined in the presence of the anaesthetics, pentobarbitone, alphaxalone and propofol. Van't Hoff plots showed the binding of FNZ to be largely enthalpy driven. Alphaxalone and propofol increased the entropy of the binding reaction but not the enthalpy and therefore did not show temperature dependence in their efficacy. In contrast, pentobarbitone increased the enthalpy of FNZ binding and, therefore, is more efficacious at low temperatures. The EC50 values of all three modulators increased with temperature indicating that their interactions with the receptor may be enthalpy driven. The EC50 values of all three modulators were also anion dependent, showing a decrease in the presence of gamma-aminobutyric acid (GABAA)-channel permeant anions. The efficacies of alphaxalone and pentobarbitone, but not that of propofol, also increased with increasing chloride ion concentration. The results indicate that all three modulators interact with the GABAA receptor at distinct recognition sites.

Modulation of nicotine-evoked [3H]dopamine release from rat striatal synaptosomes by voltage-sensitive calcium channel ligands.

The calcium channel subtypes mediating nicotine-evoked [3H]dopamine release from rat striatal synaptosomes were probed with L-, N-, and P-type calcium channel ligands. Responses to nicotine were blocked by the peptides omega-conotoxin GVIA and omega-agatoxin IVA. The affinity constants for these compounds were consistent with their actions at N- and P-type channels, respectively. Together, these channels mediate at least 90% of the calcium-dependent response to nicotine. The L-type antagonists nifedipine, verapamil, and nicardipine were also effective blockers of nicotine-evoked release with maximal effects of 80-100% inhibition. However, these effects occurred at concentrations 2-3 orders of magnitude higher than those necessary to block L-type channels. Moreover, Bay K8644, an L-type agonist, also blocked nicotine-evoked release. Together, these findings argue strongly against the involvement of L-type channels.

Propofol potentiates the binding of [3H]flunitrazepam to the GABAA receptor complex.

Propofol (2,6-diisopropylphenol) robustly stimulated the binding of 1 nM [3H]flunitrazepam (FNZ) to rat brain membranes with an EC50 of 146 microM in chloride-free buffer and 23 microM in buffer containing 200 mM NaCl. NaCl showed an EC50 of 40 mM for its ability to increase the potency of propofol. The ability of a range of anions to potentiate propofol's interactions with the GABAA-benzodiazepine receptor was closely correlated with their permeabilities at this ion channel. Propofol, at a concentration of 300 microM, decreased the EC50 for the potentiation of FNZ binding by NaCl from 39 mM to 13 mM, with no change in the maximal potentiation. At a concentration of 30 microM, propofol significantly decreased the EC50 for potentiation of FNZ binding by the neurosteroid alphaxalone whilst increasing that for potentiation by pentobarbitone. We conclude that propofol is a potent barbiturate-like modulator of [3H]flunitrazepam binding.

5 beta-pregnan-3 beta-ol-20-one, a specific antagonist at the neurosteroid site of the GABAA receptor-complex.

Studies were made on the potentiation of [3H]flunitrazepam binding to rat brain membranes by gamma-aminobutyric acid (GABA), pentobarbitone and pregnanolone (5 beta-pregnan-3 alpha-ol-20-one). Epipregnanolone, the 3 beta isomer of pregnanolone, inhibited competitively the potentiation by pregnanolone with a Ki of 10.5 microM without affecting that of GABA. The potentiation by pentobarbitone was slightly enhanced. Epipregnanolone alone showed only slight potentiation of benzodiazepine binding. These findings demonstrate that epipregnanolone is a specific antagonist of the neurosteroid site of the GABAA receptor and raise the possibility of a physiological role for 3 beta-hydroxysteroids in modulating this receptor.

Geophagy, iron status and anaemia among pregnant women on the coast of Kenya.

In a cross sectional survey based in an antenatal clinic at Kilifi District Hospital, Coast Province, Kenya, 154 of 275 pregnant women (56%) reported eating soil regularly. Geophagous women had lower haemoglobin and serum ferritin concentrations than non-geophagous women (mean haemoglobin level 9.1 vs. 10.0 g/dL, P < 0.001; median ferritin level 4.5 vs. 9.0 micrograms/L, P < 0.001). In multiple linear regression analyses, geophagy was a significant predictor of haemoglobin (beta = -6.4, P = 0.01) and serum ferritin concentrations (beta = -6.6, P = 0.002), while controlling for gestational age and malaria and hookworm infection. Another 38 pregnant women, who reported eating soil regularly, participated in focus group discussions and were interviewed on geophagy. The most commonly eaten soil was from the walls of houses. The median estimated daily intake was 41.5 g (range 2.5-219.0 g). Twenty-seven of these women assisted in the collection of soil samples which were then analysed for their content of iron, zinc and aluminium after extraction with 0.1 M HC1. The average daily soil intake supplied the geophagous women with 4.3 mg of iron, corresponding to 14% of the recommended dietary allowance of iron for pregnant women. The study revealed a strong negative association between geophagy and both haemoglobin and ferritin status. At the same time it demonstrated the potential of soil as a source of dietary iron for geophagous women. These seemingly contradictory results might be due to other components in the soil interfering with iron uptake or metabolism. Alternatively, it may be that the geophagous women had extremely depleted iron stores before starting to eat soil. From these cross-sectional data, no inference about causality could be made.

Effect of exogenous insulin on meal patterns and stomach emptying in the spiny mouse.

Male adult spiny mice (Acomys cahirinus) were acutely challenged with a single dose of regular insulin or saline vehicle SC; either food intake, meal frequency and meal duration, or stomach emptying were then measured. Meal frequency, as well as amount eaten, was significantly higher over a 6-hr period following both 10 and 30 U/kg of insulin than following vehicle injection. Meal duration remained essentially the same across all conditions. When 30 U/kg of insulin was administered either 15 min prior to, or immediately after, a solid food meal, stomach emptying (as measured by dry weight of recovered stomach contents) was accelerated relative to vehicle controls. These data are generally consistent with and extend the comparative literature suggesting a possible link between rate of stomach emptying and insulin-induced hyperphagia in some species.

Children and medicines: self-treatment of common illnesses among Luo schoolchildren in western Kenya.

In a rural area of western Kenya, primary schoolchildren's health seeking behaviour in response to common illnesses was investigated. 57 primary schoolchildren (age 11-17 years, median 13 years) were interviewed weekly about their health status and health seeking activities for 30 weeks. The children each experienced on average 25 illness episodes during this period. Most episodes could be categorised into 4 groups: 'cold', 'headache', 'abdominal complaints' and 'injuries'. One fifth (21%) of the illness episodes were serious enough to keep the children from school. In 28% of them, an adult was consulted, while 72% were not reported to an adult caretaker. Of the episodes without adult involvement, 81% remained untreated, while 19% were treated by the children themselves with either herbal or Western medicines. Of all the medicines taken by the children, two thirds were provided or facilitated by adults (assisted treatment) and one third taken by the children themselves without adult involvement (self-treatment). Among boys, the proportion of illnesses, which were self-treated increased with age from 12% in the youngest age group (< 13 years) to 34% in the oldest (> 14 years). In girls, the proportion of illnesses which were self-treated was consistently lower than among boys and remained constant around 9% for all age groups. The proportion of Western pharmaceuticals used for self-treatment increased with age from 44% in the youngest age group to 63% in the oldest (average 52% Western pharmaceuticals). Again, there were differences between boys and girls: among the youngest age group, boys were twice as likely to use pharmaceuticals than girls (62 versus 32% of the self-treatments, respectively) and in the oldest age group they were nearly three times more likely (75 versus 25%, respectively). These differences in self-treatment practices and choice of medicines between girls and boys may reflect the higher income potential of boys, who can earn money by fishing. Pharmaceuticals were generally preferred for the treatment of headache and fevers, or colds, while herbal remedies were the preferred choice for the treatment of abdominal complaints and wounds. The most commonly used pharmaceuticals were antimalarials (mainly chloroquine), painkillers and antipyretics (mainly aspirin and paracetamol), which were stocked in most small shops in the village at low prices and readily sold to children. Throughout primary school age Kenyan children are growing into a pluralistic medical practice, integrating Western pharmaceuticals into the local herbal medical system, and gradually become autonomous agents in their health care.

Perceptions of soil-eating and anaemia among pregnant women on the Kenyan coast.

After a clinical study at Kilifi District hospital had shown a high prevalence of geophagy among pregnant women, and a strong association of geophagy, anaemia and iron depletion, 52 pregnant women from the same hospital, and 4 traditional healers from the surroundings of Kilifi in Kenya were interviewed on the topic of soil-eating and its perceived causes and consequences. The findings were substantiated by results from an earlier anthropological study on maternal health and anaemia in the same study area. Most of the pregnant women (73%) ate soil regularly. They mainly ate the soil from walls of houses, and their estimated median daily ingestion was 41.5 g. They described soil-eating as a predominantly female practice with strong relations to fertility and reproduction. They made associations between soil-eating, the condition of the blood and certain bodily states: pregnancy, lack of blood (upungufu wa damu), an illness called safura involving "weak" blood, and worms (minyolo). The relationships the women described between soil-eating and illness resemble to some extent the causalities explored in biomedical research on soil-eating, anaemia and intestinal worm infections. However the women did not conceptualise the issue in terms of the single causal links characteristic of most scientific thought. Instead, they acknowledged the existence of multiple links between phenomena which they observed in their own and other women's bodies. The women's ideas about soil-eating and their bodies shows the significance of both social and cultural context on the ways in which women derive knowledge from, and make sense of their bodily states. The cultural associations of soil-eating with blood, fertility and femininity exist alongside knowledge of its links to illness. Our findings show that soil-eating is more than just a physiologically induced behaviour; it is a rich cultural practice.

The Barnum effect in a computerized Rorschach interpretation system.

Twelve psychiatric outpatients were administered the Rorschach test, and results were interpreted using the Exner (1983, 1986) Report for the Comprehensive System computer-based test interpretation (CBTI) program. Four psychiatrists made accuracy ratings for both real and bogus reports for each of their patients. Data were analyzed using two-way analyses of covariance (ANCOVAs), where report type was a repeated main effect, psychiatrist was a random main effect, and the number of statements in the report was the covariate. Results indicated that this CBTI provided only 5% discriminating power for any one patient, with 60% of the interpretive statements merely describing typical characteristics of the outpatient population. No significant psychiatrist, interaction, or covariate effects were encountered.

Epibatidine activates muscle acetylcholine receptors with unique site selectivity.

We recently showed that at desensitized muscle nicotinic receptors, epibatidine selects by 300-fold between the two agonist binding sites. To determine whether receptors in the resting, activatible state show similar site selectivity, we studied epibatidine-induced activation of mouse fetal and adult receptors expressed in 293 HEK cells. Kinetic analysis of single-channel currents reveals that (-)-epibatidine binds with 15-fold selectivity to sites of adult receptors and 75-fold selectivity to sites of fetal receptors. For each receptor subtype, site selectivity arises solely from different rates of epibatidine dissociation from the two sites. To determine the structural basis for epibatidine selectivity, we introduced mutations into either the gamma or the delta subunit and measured epibatidine binding and epibatidine-induced single-channel currents. Complexes formed by alpha and mutant gamma(K34S+F172I) subunits bind epibatidine with increased affinity compared to alphagamma complexes, whereas the kinetics of alpha2betadeltagamma(K34S+F172I) receptors reveal no change in affinity of the low-affinity site, but increased affinity of the high-affinity site. Conversely, complexes formed by alpha and mutant delta(S36K+I178F) subunits bind epibatidine with decreased affinity compared to alphadelta complexes, whereas the kinetics of alpha2betagammadelta(S36K+I178F) and alpha2betaepsilondelta(S36K+I178F) receptors show markedly reduced sensitivity to epibatidine. The overall data show that epibatidine activates muscle receptors by binding with high affinity to alphagamma and alphaepsilon sites, but with low affinity to the alphadelta site.

Epibatidine binds with unique site and state selectivity to muscle nicotinic acetylcholine receptors.

Ligand binding sites in fetal (alpha2betagammadelta) and adult (alpha2betadeltaepsilon) muscle acetylcholine receptors are formed by alphadelta, alphagamma, or alphaepsilon subunit pairs. Each type of binding site shows unique ligand selectivity due to different contributions by the delta, gamma, or epsilon subunits. The present study compares epibatidine and carbamylcholine binding in terms of their site and state selectivities for muscle receptors expressed in human embryonic kidney 293 cells. Measurements of binding to alphagamma, alphadelta, and alphaepsilon intracellular complexes reveal opposite site selectivities between epibatidine and carbamylcholine; for epibatidine the rank order of affinities is alphaepsilon > alphagamma > alphadelta, whereas for carbamylcholine the rank order is alphadelta congruent with alphaepsilon > alphagamma. Because the relative affinities of intracellular complexes resemble those of receptors in the closed activable state, the results suggest that epibatidine binds with unique site selectivity in activating the muscle receptor. Measurements of binding at equilibrium show that both enantiomers of epibatidine bind to adult and fetal receptors with shallow but monophasic binding curves. However, when receptors are fully desensitized, epibatidine binds in a biphasic manner, with dissociation constants of the two components differing by more than 170-fold. Studies of subunit-omitted receptors (alpha2betadelta2, alpha2betagamma2, and alpha2betaepsilon2) reveal that in the desensitized state, the alphadelta interface forms the low affinity epibatidine site, whereas the alphagamma and alphaepsilon interfaces form high affinity sites. In contrast to epibatidine, carbamylcholine shows little site selectivity for desensitized fetal or adult receptors. Thus epibatidine is a potentially valuable probe of acetylcholine receptor binding site structure and of elements that confer state-dependent selectivities of the binding sites.

Molecular dissection of subunit interfaces in the acetylcholine receptor. Identification of residues that determine agonist selectivity.

Agonists and antagonists select between the alphagamma and ns31744adelta binding sites of the fetal muscle acetylcholine receptor owing to different contributions by the gamma and delta subunits. To identify determinants of selectivity for agonists, we constructed a panel of gamma-delta subunit chimeras, co-expressed them with the alpha subunit in 293 HEK cells, and measured carbamylcholine binding affinity of intracellular complexes. Wild-type alphadelta complexes bind carbamylcholine about 30-fold more tightly than alphagamma complexes. This degree of selectivity is similar to that of the resting state of the receptor determined by kinetic analysis of single-channel events. We identify a primary set of determinants of selectivity, Lysgamma34/Serdelta36 and Phegamma172/Iledelta178, and a secondary set, Glugamma57/Aspdelta59 and Cysgamma115/Tyrdelta117. The contributions of all four determinants are subunit-dependent and are modified by interaction with one another. Coexpression of point mutant subunits with complementary wild-type subunits to form cell surface pentamers shows that Lysgamma34/Serdelta36 and Phegamma172/Iledelta178 contribute in a manner consistent with affecting selectivity of the resting state of the receptor, while Glugamma57 appears to contribute to the affinity of the desensitized state. The four determinants either coincide with or are close to residues known to contribute to the acetylcholine binding site. These results suggest that a minimum of four loops in the gamma and delta subunits contribute to the agonist binding site.

Acetylcholine and epibatidine binding to muscle acetylcholine receptors distinguish between concerted and uncoupled models.

The muscle acetylcholine receptor (AChR) has served as a prototype for understanding allosteric mechanisms of neurotransmitter-gated ion channels. The phenomenon of cooperative agonist binding is described by the model of Monod et al. (Monod, J., Wyman, J., and Changeux, J. P. (1965) J. Mol. Biol. 12, 88-118; MWC model), which requires concerted switching of the two binding sites between low and high affinity states. The present study examines binding of acetylcholine (ACh) and epibatidine, agonists with opposite selectivity for the two binding sites of mouse muscle AChRs. We expressed either fetal or adult AChRs in 293 HEK cells and measured agonist binding by competition against the initial rate of 125I-alpha-bungarotoxin binding. We fit predictions of the MWC model to epibatidine and ACh binding data simultaneously, taking as constants previously determined parameters for agonist binding and channel gating steps, and varying the agonist-independent parameters. We find that the MWC model describes the apparent dissociation constants for both agonists but predicts Hill coefficients that are far too steep. An Uncoupled model, which relaxes the requirement of concerted state transitions, accurately describes binding of both ACh and epibatidine and provides parameters for agonist-independent steps consistent with known aspects of AChR function.

The "calcium antagonist" TMB-8 [3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester] is a potent, non-competitive, functional antagonist at diverse nicotinic acetylcholine receptor subtypes.

[3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester] (TMB-8) has seen wide use as an "intracellular Ca2+ antagonist." However, this study shows that TMB-8 acts as a noncompetitive, functional antagonist at diverse nicotinic acetylcholine receptor (nAChR) subtypes with potencies that exceed those for other reported effects of TMB-8, including inhibition of intracellular Ca2+ mobilization. TMB-8 is a potent inhibitor (IC50 approximately 400 nM) of agonist-stimulated ion flux mediated by functional human muscle nAChR or ganglionic alpha 3 beta 4-nAChR subtypes expressed by TE671/RD or SH-SY5Y cells. TMB-8 is also a potent inhibitor (IC50 approximately 500 nM) of a functional, central nervous system nAChR subtype that mediates nicotinic agonist-stimulated [3H]dopamine release from rat brain synaptosomes. TMB-8 is much less potent (IC50 approximately 30-200 microM) as an inhibitor of high-affinity 3H-labeled acetylcholine or 125I-labeled alpha-bungarotoxin binding to human muscle nAChR, ganglionic alpha 3 beta 4-nAChR, or ganglionic alpha 7-nAChR subtypes. Moreover, functional inhibition by TMB-8 of muscle-type nAChR is due to a reduction in agonist efficacy, but not potency, and is proportionately stronger with increasing agonist concentration, thereby suggesting that TMB-8 acts as a noncompetitive inhibitor. Similar effects are observed for local anesthetics such as tetracaine and procaine (functional IC50 values of approximately 5 and approximately 50 microM, respectively), although TMB-8 is the most potent of these agents. Studies with TMB-8 or BAPTA [1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid] analogues indicate that the amino group of TMB-8 is essential and that Ca2+ chelation is not required for inhibition of nAChR function.(ABSTRACT TRUNCATED AT 250 WORDS)