Child eating behaviors are consistently linked to intake across meals that vary in portion size

Prior studies evaluating a single meal in children characterized an "obesogenic" style of eating marked by larger bites and faster eating. It is unclear if this style is consistent across portion sizes within children so we examined eating behaviors in 91 children (7-8 years, 45 F) without obesity (BMI<90th percentile). Children consumed 4 ad libitum meals in the laboratory consisting of chicken nuggets, macaroni, grapes, and broccoli that varied in portion size (100%, 133%, 166%, 200%) with a maximum of 30 min allotted per meal. Anthropometrics were assessed using age and sex adjusted body mass index (BMI) percentile and dual energy x-ray absorptiometry. Bites, sips, active eating time, and meal duration were coded from meal videos; bite size (kcal and g/bite), proportion of active eating (active eating time/meal duration), and eating rate (kcal and g/meal duration) were computed. Intraclass correlation coefficients (ICC) showed that most eating behaviors were moderately consistent across portions (>0.50). The consistency of associations between eating behaviors and total meal intake and adiposity were assessed with general linear models adjusted for food liking, pre-meal fullness, age, and sex. Across all portions, more bites, faster eating rate, and longer meal duration were associated with greater intake. While higher BMI percentile was associated with faster eating rates across all meals, greater fat mass index was only associated with faster eating at meals with portions typical for children (i.e., 100% and 133%). In a primarily healthy weight sample, an 'obesogenic' style of eating was a consistent predictor of greater intake across meals that varied in portion size. The consistent relationship of these behaviors with intake makes them promising targets to reduce overconsumption.

First Global-Scale Synoptic Imaging of Solar Eclipse Effects in the Thermosphere

A total solar eclipse occurred in the Southern Hemisphere on 2 July 2019 from approximately 17 to 22 UT. Its effect in the thermosphere over South America was imaged from geostationary orbit by NASA's Global-scale Observation of Limb and Disk (GOLD) instrument. GOLD observed a large brightness reduction (>80% around totality) in OI 135.6 nm and N₂ LBH band emissions compared to baseline measurements made 2 days prior. In addition, a significant enhancement (with respect to the baseline) in the ΣO/N₂ column density ratio (~80%) was observed within the eclipse's totality. This enhancement suggests that the eclipse induced compositional changes in the thermosphere. After the eclipse passed, a slight enhancement in ΣO/N₂ column density ratio (~7%) was also seen around the totality path when compared to measurements before the eclipse. These observations are the first synoptic imaging measurements of an eclipse's thermospheric effects with the potential to drastically improve and test our understanding of how the thermosphere responds to rapid, localized changes in solar short wavelength radiation.

First Global-Scale Synoptic Imaging of Solar Eclipse Effects in the Thermosphere

A total solar eclipse occurred in the Southern Hemisphere on 2 July 2019 from approximately 17 to 22 UT. Its effect in the thermosphere over South America was imaged from geostationary orbit by NASA's Global-scale Observation of Limb and Disk (GOLD) instrument. GOLD observed a large brightness reduction (>80% around totality) in OI 135.6 nm and N2 LBH band emissions compared to baseline measurements made 2 days prior. In addition, a significant enhancement (with respect to the baseline) in the ΣO/N2 column density ratio (~80%) was observed within the eclipse's totality. This enhancement suggests that the eclipse induced compositional changes in the thermosphere. After the eclipse passed, a slight enhancement in ΣO/N2 column density ratio (~7%) was also seen around the totality path when compared to measurements before the eclipse. These observations are the first synoptic imaging measurements of an eclipse's thermospheric effects with the potential to drastically improve and test our understanding of how the thermosphere responds to rapid, localized changes in solar short wavelength radiation.

Antigenic site changes in the rabies virus glycoprotein dictates functionality and neutralizing capability against divergent lyssaviruses

Lyssavirus infection has a near 100 % case fatality rate following the onset of clinical disease, and current rabies vaccines confer protection against all reported phylogroup I lyssaviruses. However, there is little or no protection against more divergent lyssaviruses and so investigation into epitopes within the glycoprotein (G) that dictate a neutralizing response against divergent lyssaviruses is warranted. Importantly, the facilities required to work with these pathogens, including wild-type and mutated forms of different lyssaviruses, are scarcely available and, as such, this type of study is inherently difficult to perform. The relevance of proposed immunogenic antigenic sites within the lyssavirus glycoprotein was assessed by swapping sites between phylogroup-I and -II glycoproteins. Demonstrable intra- but limited inter-phylogroup cross-neutralization was observed. Pseudotype viruses (PTVs) presenting a phylogroup-I glycoprotein containing phylogroup-II antigenic sites (I, II III or IV) were neutralized by antibodies raised against phylogroup-II PTV with the site II (IIb, aa 34-42 and IIa, aa 198-200)-swapped PTVs being efficiently neutralized, whilst site IV-swapped PTV was poorly neutralized. Specific antibodies raised against PTV-containing antigenic site swaps between phylogroup-I and -II glycoproteins neutralized phylogroup-I PTVs efficiently, indicating an immunodominance of antigenic site II. Live lyssaviruses containing antigenic site-swapped glycoproteins were generated and indicated that specific residues within the lyssavirus glycoprotein dictate functionality and enable differential neutralizing antibody responses to lyssaviruses.

Left ventricular outflow tract obstruction-be prepared!

The current trend to treat hypotension in critically ill patients is to place a greater emphasis on inotropic support and less on fluid resuscitation in order to limit the potential harm from fluid overload. This combination may trigger left ventricular outflow tract obstruction (LVOTO) in susceptible patients. Although LVOTO is classically described in patients with hypertrophic cardiomyopathy it has been reported in other conditions including septic shock, apical ballooning syndrome, myocardial infarction, respiratory failure, and post valvular surgery. It is more common in the elderly, females, and in patients with hypertension, diabetes, and chronic vascular disease because of predisposing anatomical conditions such as left ventricular hypertrophy, small left ventricle size, sigmoid septum and alterations in the positions of the aortic and mitral valve annular planes. The onset of LVOTO is largely unpredictable due to a complex interplay between preload, afterload, heart rhythm and rate in susceptible patients. The consequences of missing this treatable condition may lead to life-threatening hypotension refractory to, or exacerbated by, a further increase in inotropic support. Dynamic LVOTO should be considered in any hypotensive intensive care patient. Echocardiography is perhaps the best tool to assess LVOTO and its underlying pathophysiology in the critically ill. Detection of LVOTO is a relatively simple task using a combination of two-dimensional, M-mode and spectral Doppler imaging by an operator alert to the possible diagnosis.

The contribution of outdoor air pollution sources to premature mortality on a global scale

Assessment of the global burden of disease is based on epidemiological cohort studies that connect premature mortality to a wide range of causes, including the long-term health impacts of ozone and fine particulate matter with a diameter smaller than 2.5 micrometres (PM2.5). It has proved difficult to quantify premature mortality related to air pollution, notably in regions where air quality is not monitored, and also because the toxicity of particles from various sources may vary. Here we use a global atmospheric chemistry model to investigate the link between premature mortality and seven emission source categories in urban and rural environments. In accord with the global burden of disease for 2010 (ref. 5), we calculate that outdoor air pollution, mostly by PM2.5, leads to 3.3 (95 per cent confidence interval 1.61-4.81) million premature deaths per year worldwide, predominantly in Asia. We primarily assume that all particles are equally toxic, but also include a sensitivity study that accounts for differential toxicity. We find that emissions from residential energy use such as heating and cooking, prevalent in India and China, have the largest impact on premature mortality globally, being even more dominant if carbonaceous particles are assumed to be most toxic. Whereas in much of the USA and in a few other countries emissions from traffic and power generation are important, in eastern USA, Europe, Russia and East Asia agricultural emissions make the largest relative contribution to PM2.5, with the estimate of overall health impact depending on assumptions regarding particle toxicity. Model projections based on a business-as-usual emission scenario indicate that the contribution of outdoor air pollution to premature mortality could double by 2050.

War-related stressors are associated with asthma risk among older Kuwaitis following the 1990 Iraqi invasion and occupation

BACKGROUND

Contemporary warfare involving civilian populations is a growing public health concern. In addition to the psychological impact, war-related trauma may result in physiological alterations and even broader health effects. Associations were examined between war-related stressors and incident asthma in elderly Kuwaiti civilians following the Iraqi invasion.

METHODS

A random sample of all Kuwaiti nationals aged 50-69 years on the day prior to the invasion were identified. Among the 7873 meeting eligibility criteria, 5567 (71%) agreed to participate and 5028 completed the questionnaire (91% of those eligible). Of these, 3759 were in Kuwait during the invasion, of whom 2294 were alive at follow-up. After exclusions for prevalent asthma or missingness on covariates, 2066 were available for analysis. War-related experiences were summarised into a continuous score using Rasch modelling. Relative Cox proportional hazard rates (HR) were calculated for asthma adjusting for covariates.

RESULTS

Over 13 years of follow-up, physician-diagnosed asthma was reported by 66/996 (6.6%) men and 104/1070 (9.7%) women. In models adjusted for gender, socioeconomic status, smoking, BMI, and air pollution related to burning oil fires, those reporting highest stress exposure were more than twice as likely to report asthma (HR 2.3, 95% CI 1.3, 3.9) compared to civilians reporting no stressors. Experiences were more salient when anchored to fear for loss of life.

CONCLUSIONS

War-related trauma is associated with increased asthma risk in these elderly civilians. Although prior research has documented the significant and persistent psychological toll of war, these findings implicate even broader health effects.

Putting the ‘landscape’ in landscape genetics

Landscape genetics has emerged as a new research area that integrates population genetics, landscape ecology and spatial statistics. Researchers in this field can combine the high resolution of genetic markers with spatial data and a variety of statistical methods to evaluate the role that landscape variables play in shaping genetic diversity and population structure. While interest in this research area is growing rapidly, our ability to fully utilize landscape data, test explicit hypotheses and truly integrate these diverse disciplines has lagged behind. Part of the current challenge in the development of the field of landscape genetics is bridging the communication and knowledge gap between these highly specific and technical disciplines. The goal of this review is to help bridge this gap by exposing geneticists to terminology, sampling methods and analysis techniques widely used in landscape ecology and spatial statistics but rarely addressed in the genetics literature. We offer a definition for the term "landscape genetics", provide an overview of the landscape genetics literature, give guidelines for appropriate sampling design and useful analysis techniques, and discuss future directions in the field. We hope, this review will stimulate increased dialog and enhance interdisciplinary collaborations advancing this exciting new field.

Assessing the public health benefits of reduced ozone concentrations

In this paper we examine scientific evidence and related uncertainties in two steps of benefit-cost analyses of ozone reduction: estimating the health improvements attributable to reductions in ozone and determining the appropriate monetary values of these improvements. Although substantial evidence exists on molecular and physiologic impacts, the evidence needed to establish concentration-response functions is somewhat limited. Furthermore, because exposure to ozone depends on factors such as air conditioning use, past epidemiologic studies may not be directly applicable in unstudied settings. To evaluate the evidence likely to contribute significantly to benefits, we focus on four health outcomes: premature mortality, chronic asthma, respiratory hospital admissions, and minor restricted activity days. We determine concentration-response functions for these health outcomes for a hypothetical case study in Houston, Texas, using probabilistic weighting reflecting our judgment of the strength of the evidence and the possibility of confounding. We make a similar presentation for valuation, where uncertainty is due primarily to the lack of willingness-to-pay data for the population affected by ozone. We estimate that the annual monetary value of health benefits from reducing ozone concentrations in Houston is approximately $10 per person per microgram per cubic meter (24-hr average) reduced (95% confidence interval, $0.70-$40). The central estimate exceeds past estimates by approximately a factor of five, driven by the inclusion of mortality. We discuss the implications of our findings for future analyses and determine areas of research that might help reduce the uncertainties in benefit estimation.

Ab initio structure determination of BiPb2VO6 from powder diffraction data

The crystal structure of BiPb2VO6 has been determined from powder diffraction data using a combination of direct methods and the novel approach of applying simulated annealing methods simultaneously to X-ray and neutron data; BiPb2VO6 is a polar, noncentrosymmetric, second harmonic generation active material and its crystal structure is one of the more complex to be solved ab initio from powder diffraction data.

A space group assignment of ZrP2O7 obtained by 31P solid state NMR

2-D 31P dipolar recoupling magic angle spinning NMR has been used to determine the true symmetry of the low temperature structure of ZrP2O7 for the first time.

Modeling for health care and other policy decisions: uses, roles, and validity

The role of models to support recommendations on the cost-effective use of medical technologies and pharmaceuticals is controversial. At the heart of the controversy is the degree to which experimental or other empirical evidence should be required prior to model use. The controversy stems in part from a misconception that the role of models is to establish truth rather than to guide clinical and policy decisions. In other domains of public policy that involve human life and health, such as environmental protection and defense strategy, models are generally accepted as decision aids, and many models have been formally incorporated into regulatory processes and governmental decision making. We formulate an analytical framework for evaluating the role of models as aids to decision making. Implications for the implementation of Section 114 of the Food and Drug Administration Modernization Act (FDAMA) are derived from this framework.

Reproductive and developmental risks from ethylene oxide: a probabilistic characterization of possible regulatory thresholds

Ethylene oxide is a gas produced in large quantities in the United States that is used primarily as a chemical intermediate in the production of ethylene glycol, propylene glycol, non-ionic surfactants, ethanolamines, glycol ethers, and other chemicals. It has been well established that ethylene oxide can induce cancer, genetic, reproductive and developmental, and acute health effects in animals. The U.S. Environmental Protection Agency is currently developing both a cancer potency factor and a reference concentration (RfC) for ethylene oxide. This study used the rich database on the reproductive and developmental effects of ethylene oxide to develop a probabilistic characterization of possible regulatory thresholds for ethylene oxide. This analysis was based on the standard regulatory approach for noncancer risk assessment, but involved several innovative elements, such as: (1) the use of advanced statistical methods to account for correlations in developmental outcomes among littermates and allow for simultaneous control of covariates (such as litter size); (2) the application of a probabilistic approach for characterizing the uncertainty in extrapolating the animal results to humans; and (3) the use of a quantitative approach to account for the variation in heterogeneity among the human population. This article presents several classes of results, including: (1) probabilistic characterizations of ED10s for two quantal reproductive outcomes-resorption and fetal death, (2) probabilistic characterizations of one developmental outcome-the dose expected to yield a 5% reduction in fetal (or pup) weight, (3) estimates of the RfCs that would result from using these values in the standard regulatory approach for noncancer risk assessment, and (4) a probabilistic characterization of the level of ethylene oxide exposure that would be expected to yield a 1/1,000 increase in the risk of reproductive or developmental outcomes in exposed human populations.

Limitations to empirical extrapolation studies: the case of BMD ratios

Extrapolation relationships are of keen interest to chemical risk assessment in which they play a prominent role in translating experimentally derived (usually in animals) toxicity estimates into estimates more relevant to human populations. A standard approach for characterizing each extrapolation relies on ratios of pre-existing toxicity estimates. Applications of this "ratio approach" have overlooked several sources of error. This article examines the case of ratios of benchmark doses, trying to better understand their informativeness. The approach involves mathematically modeling the process by which the ratios are generated in practice. Both closed form and simulation-based models of this "data-generating process" (DGP) are developed, paying special attention to the influence of experimental design. The results show the potential for significant limits to informativeness, and revealing dependencies. Future applications of the ratio approach should take imprecision and bias into account. Bootstrap techniques are recommended for gauging imprecision, but more complicated techniques will be required for gauging bias (and capturing dependencies). Strategies for mitigating the errors are suggested.

Necessity, possibility and belief: a study of syllogistic reasoning

The present study extended the investigation of the belief bias effect in syllogistic reasoning in two ways: (1) The effect was studied under instructions to decide whether conclusions were possible, as well as necessary, given the premises; and (2) the effect was studied for types of syllogism where people rarely endorse the conclusions as well as those (valid and fallacious) where endorsements are common. Three experiments are reported, which show first that there is a marked tendency to reject unbelievable conclusions relative to abstract or neutral controls on all kinds of syllogism and under both types of instruction. There was also significant evidence of positive belief bias (increased acceptance of believable conclusions) and of interactions between belief bias effects and logical form. The results are discussed with particular respect to accounts of belief bias offered by theorists in the mental-model tradition.

Use of expert judgment in exposure assessment. Part I. Characterization of personal exposure to benzene

This paper presents the results of the first phase of a study, conducted as an element of the National Human Exposure Assessment Survey (NHEXAS), to demonstrate the use of expert subjective judgment elicitation techniques to characterize the magnitude of and uncertainty in environmental exposure to benzene. In decisions about the value of exposure research or of regulatory controls, the characterization of uncertainty can play an influential role. Classical methods for characterizing uncertainty may be sufficient when adequate amounts of relevant data are available. Frequently, however, data are neither abundant nor directly relevant, making it necessary to rely to varying degrees on subjective judgment. Since the 1950s, methods to elicit and quantify subjective judgments have been explored but have rarely been applied to the field of environmental exposure assessment. In this phase of the project, seven experts in benzene exposure assessment were selected through a peer nomination process, participated in a 2-day workshop, and were interviewed individually to elicit their judgments about the distributions of residential ambient, residential indoor, and personal air benzene concentrations (6-day integrated average) experienced by both the non-smoking, non-occupationally exposed target and study populations of the US EPA Region V pilot study. Specifically, each expert was asked to characterize, in probabilistic form, the arithmetic means and the 90th percentiles of these distributions. This paper presents the experts' judgments about the concentrations of benzene encountered by the target population. The experts' judgments about levels of benzene in personal air were demonstrative of patterns observed in the judgments about the other distributions. They were in closest agreement about their predictions of the mean; with one exception, their best estimates of the mean fell within 7-11 microg/m(3) although they exhibited striking differences in the degree of uncertainty expressed. Their estimates of the 90th percentile were more varied with the best estimates ranging from 12 to 26 microg/m(3) for all but one expert. However, their predictions of the 90th percentile were far more uncertain. The paper demonstrates that coherent subjective judgments can be elicited from exposure assessment scientists and critically examines the challenges and potential benefits of a subjective judgment approach. The results of the second phase of the project, in which measurements from the NHEXAS field study in Region V are used to calibrate the experts' judgments about the benzene exposures in the study population, will be presented in a second paper.

Cytoplasmic interactions between phospholamban residues 1-20 and the calcium-activated ATPase of the sarcoplasmic reticulum

Phospholamban regulates the activity of the calcium-activated ATPase (CaATPase) of cardiac sarcoplasmic reticulum. Equilibrium fluorescence studies have shown that the N-terminal cytoplasmic region of phospholamban (residues 1-20, domain 1) causes a decrease in the intrinsic tryptophan fluorescence of the CaATPase. The interaction of phospholamban residues 1-20 with the CaATPase also results in spectral changes for the extrinsic chromophore FITC covalently attached to the cytoplasmic region of the calcium pump. The fluorescence changes for both reporter groups correlate with a dissociation constant of approximately 40 microM for the complex between phospholamban residues 1-20 and the CaATPase. Complex formation is notably weaker when phospholamban 1-20 is titrated into the CaATPase in the presence of calcium, with altered conformational effects resulting from binding. The interaction of domain 1 of phospholamban with the CaATPase is also reduced upon phosphorylation of phospholamban 1-20 at Ser-16. This region of phospholamban 1-20 is shown by isotope-edited NMR study to be involved in interaction with the CaATPase. Binding of the phosphorylated peptide is not abolished, however, indicating that phospholamban 1-20 remains associated with the CaATPase even after phosphorylation. The data provide direct evidence for the interaction between the cytoplasmic regions of phospholamban and the pump, and are discussed in the context of the mechanism for inhibition of cardiac CaATPase activity by phospholamban.

Modeling AFM-induced PEVK extension and the reversible unfolding of Ig/FNIII domains in single and multiple titin molecules

Molecular elasticity is associated with a select number of polypeptides and proteins, such as titin, Lustrin A, silk fibroin, and spider silk dragline protein. In the case of titin, the globular (Ig) and non-globular (PEVK) regions act as extensible springs under stretch; however, their unfolding behavior and force extension characteristics are different. Using our time-dependent macroscopic method for simulating AFM-induced titin Ig domain unfolding and refolding, we simulate the extension and relaxation of hypothetical titin chains containing Ig domains and a PEVK region. Two different models are explored: 1) a series-linked WLC expression that treats the PEVK region as a distinct entropic spring, and 2) a summation of N single WLC expressions that simulates the extension and release of a discrete number of parallel titin chains containing constant or variable amounts of PEVK. In addition to these simulations, we also modeled the extension of a hypothetical PEVK domain using a linear Hooke's spring model to account for "enthalpic" contributions to PEVK elasticity. We find that the modified WLC simulations feature chain length compensation, Ig domain unfolding/refolding, and force-extension behavior that more closely approximate AFM, laser tweezer, and immunolocalization experimental data. In addition, our simulations reveal the following: 1) PEVK extension overlaps with the onset of Ig domain unfolding, and 2) variations in PEVK content within a titin chain ensemble lead to elastic diversity within that ensemble.

Frequency versus probability formats in statistical word problems

Three experiments examined people's ability to incorporate base rate information when judging posterior probabilities. Specifically, we tested the (Cosmides, L., & Tooby, J. (1996). Are humans good intuitive statisticians after all? Rethinking some conclusions from the literature on judgement under uncertainty. Cognition, 58, 1-73) conclusion that people's reasoning appears to follow Bayesian principles when they are presented with information in a frequency format, but not when information is presented as one case probabilities. First, we found that frequency formats were not generally associated with better performance than probability formats unless they were presented in a manner which facilitated construction of a set inclusion mental model. Second, we demonstrated that the use of frequency information may promote biases in the weighting of information. When participants are asked to express their judgements in frequency rather than probability format, they were more likely to produce the base rate as their answer, ignoring diagnostic evidence.

Model peptide studies of sequence repeats derived from the intracrystalline biomineralization protein, SM50. II. Pro,Asn-rich tandem repeats

In the biomineralization process, a number of Pro-rich proteins participate in the formation of three-dimensional supramolecular structures. One such protein superfamily, the Pro,Gly-rich sea urchin intracrystalline spicule matrix proteins, form protein-protein supramolecular assemblies that modify the microstructure of the inorganic mineral phase (calcite) within embryonic sea urchin spicules and adult sea urchin spines. These proteins represent a useful model for understanding Pro sequence usage and the resulting generation of extended or "open" structures for protein-protein and/or protein-crystal recognition. In the sea urchin spicule matrix protein, SM50 (Strongylocentrotus purpuratus), there exists an unusual 20-residue Pro,Asn-containing repeat, &bond;PNNPNNPNPNNPNNPNNPNPbond which links the upstream 15-residue C-terminal domain and the downstream 211-residue beta-spiral repeat domain. To define the structural preferences of this 20-residue repeat, we created a 20-residue N- and C-terminal "capped" peptidomimetic of this sequence. Using far-uv CD dichroism, CH(alpha) and alpha-(15)N conformational shifts, (3)J(NH-CHalpha) coupling constants, sequential d(NN(i, i + 1)) rotating frame nuclear Overhauser effect connectivities, d(alphaN(i, i + 1))/d(NN(i, i + 1)) intensity ratios, amide temperature shift coefficients, amide solvent exchange, and simulated annealing refinement protocols, we have determined that this 20-residue repeat motif adopts an extended "twist" structure consisting of turn- and coil-like regions. These findings are consistent with previous studies, which have shown that Pro-rich tandem repeats adopt extended, flexible structures in solution. We hypothesize that this 20-residue repeat may fulfill the role of a mineral-binding domain, a protein-protein docking domain, or as an internal "molecular spacer" for the SM50 protein during spicule biocomposite formation.

Exposure efficiency: concept and application to perchloroethylene exposure from dry cleaners

Standard approaches for computing population exposures due to specific sources of air pollutants are relatively complex. In many cases, more simple and approximate methods would be useful. This paper develops an approach, based on the concept of exposure efficiency, that may be used for estimating the impact of a source (or source class) on the integrated population exposure. The approach is illustrated by an example, which uses the concept of exposure efficiency to examine the impact of perchloroethylene emissions from dry cleaners in the United States. The paper explores the geographic variability of exposure efficiency by evaluating it for each of 100 randomly selected dry cleaners. For perchloroethylene, which has a long atmospheric residence time, the site-to-site variability in exposure efficiency is found to be relatively small. This suggests that simple exposure assessments, based on generic distributional characterizations of exposure efficiency, may be used in risk assessments without introducing appreciable uncertainty. For many compounds, like perchloroethylene, the uncertainty inherent in the estimation of cancer potency or source emissions would dominate these small errors.

Assessing the impact of differential measurement error on estimates of fine particle mortality

In air pollution epidemiology, error in measurements of correlated pollutants has been advanced as a reason to distrust regressions that find statistically significant weak associations. Much of the related debate in the literature and elsewhere has been qualitative. To promote quantitative evaluation of such errors, this paper develops an air pollution time-series model based on correlations among unit-normal variables. Assuming there are no other sources of bias present, the model shows the expected amount of relative bias in the regression coefficients of a bivariate regression of coarse and fine particulate matter measurements on daily mortality. The model only requires information on instrumental error and spatial variability, along with the observed regression coefficients and information on the true fine-course correlation. Analytical results show that if one pollutant is truly more harmful than the other, then it must be measured more precisely than the other in order not to bias the ratio of the fine and course regression coefficients. Utilizing published data, a case study of the Harvard Six-Cities study illustrates use of the model and emphasizes the need for data on spatial variability across the study area. Current epidemiology time-series regressions can use this model to address the general concern of correlated pollutants with differing measurement errors.

Neurological recovery after prolonged verapamil-induced cardiac arrest

A 15-year-old female survived a total of 65 minutes cardiac arrest following ingestion of verapamil and selective serotonin re-uptake inhibitors. We consider that the lack of neurological damage, despite evidence of significant renal and myocardial injury, may be related to the possible neuroprotective effect of a large dose of verapamil.

Race-specific HIV-1 disease-modifying effects associated with CCR5 haplotypes

Genetic variation in CC chemokine receptor 5 (CCR5), the major HIV-1 coreceptor, has been shown to influence HIV-1 transmission and disease progression. However, it is generally assumed that the same CCR5 genotype (or haplotype) has similar phenotypic effects in different populations. To test this assumption, we used an evolutionary-based classification of CCR5 haplotypes to determine their associated HIV-1 disease-modifying effects in a large well-characterized racially mixed cohort of HIV-1-seropositive individuals. We demonstrate that the spectrum of CCR5 haplotypes associated with disease acceleration or retardation differs between African Americans and Caucasians. Also, we show that there is a strong interactive effect between CCR5 haplotypes with different evolutionary histories. The striking population-specific phenotypic effects associated with CCR5 haplotypes emphasize the importance of understanding the evolutionary context in which disease susceptibility genes are expressed.

Update on medications used to treat gastrointestinal disease in children

Progress in the pharmacotherapy of pediatric gastrointestinal diseases continued during 1998 despite ongoing obstacles encountered by clinicians and researchers. The major change involved warnings that cisapride, a widely used prokinetic agent, could cause potentially fatal arrythmias in susceptible people. The risk for children is unclear and a consensus of prescribing guidelines is needed. Excellent pediatric-oriented reviews have been published that summarize our knowledge of proton pump inhibitors, probiotics, 5-hydroxtryptamine-3 (5-HT3) antagonists, and the treatment of gastrointestinal infections and chronic abdominal pain. Triple medication therapy for the eradication of Helicobacter pylori is now the standard of care, but the optimal combination and duration of therapy needs to be determined. Also described are interesting developments requiring further confirmation: the treatments of infectious diarrhea with zinc; achalasia and Hirschsprung's disease with botulinum toxin; weight loss with megestrol acetate; and sialorrhea with glycopyrollate.

A kinetic molecular model of the reversible unfolding and refolding of titin under force extension

Molecular elasticity is a physicomechanical property that is associated with a select number of polypeptides and proteins, such as the giant muscle protein, titin, and the extracellular matrix protein, tenascin. Both proteins have been the subject of atomic force microscopy (AFM), laser tweezer, and other in vitro methods for examining the effects of force extension on the globular (FNIII/Ig-like) domains that comprise each protein. In this report we present a time-dependent method for simulating AFM force extension and its effect on FNIII/Ig domain unfolding and refolding. This method treats the unfolding and refolding process as a standard three-state protein folding model (U right arrow over left arrow T right arrow over left arrow F, where U is the unfolded state, T is the transition or intermediate state, and F is the fully folded state), and integrates this approach within the wormlike chain (WLC) concept. We simulated the effect of AFM tip extension on a hypothetical titin molecule comprised of 30 globular domains (Ig or FNIII) and 25% Pro-Glu-Val-Lys (PEVK) content, and analyzed the unfolding and refolding processes as a function of AFM tip extension, extension rate, and variation in PEVK content. In general, we find that the use of a three-state protein-folding kinetic-based model and the implicit inclusion of PEVK domains can accurately reproduce the experimental force-extension curves observed for both titin and tenascin proteins. Furthermore, our simulation data indicate that PEVK domains exhibit extensibility behavior, assist in the unfolding and refolding of FNIII/Ig domains in the titin molecule, and act as a force "buffer" for the FNIII/Ig domains, particularly at low and moderate extension forces.

PFG-omega1-filtered TOCSY experiments for the determination of long-range heteronuclear and homonuclear coupling constants and estimation of J-coupling "crosstalk" artifacts in 2-D omega1-filtered "E. COSY-style" spectra

We present novel one- and two-dimensional versions of the omega1-filtered TOCSY experiment. These experiments utilize pulsed-field gradient techniques and INEPT-reverse INEPT magnetization transfer to generate heteronuclear filtering by means of coherence pathway selection. The major advantages of this approach are twofold: first, each experiment requires a reasonable number of transmitter pulses, gradient pulses, and delays to implement. Second, the use of z-axis gradients at the beginning and termination of the pulse sequences prevents the recovery of dephased magnetization prior to FID detection. This technique was incorporated into 1-D and 2-D omega1-filtered JXH- and JHH-TOCSY-style experiments. As demonstrated on 15N-enriched peptide samples, the use of the pulsed-field-gradient coherence selection scheme effectively filters out unwanted magnetization components, thereby improving the overall sensitivity of the experiments. In addition to this suite of pulse sequences, we also present a method for correcting the reduction in J-coupling that results from crosspeak shifting in 2-D omega1-filtered E. COSY-style spectra. This correction is applicable to both Lorentzian and Gaussian 2-D crosspeak lineshapes.

Estimating noncancer uncertainty factors: are ratios NOAELs informative?

The prominent role of animal bioassay evidence in environmental regulatory decisions compels a careful characterization of extrapolation uncertainties. In noncancer risk assessment, uncertainty factors are incorporated to account for each of several extrapolations required to convert a bioassay outcome into a putative subthreshold dose for humans. Measures of relative toxicity taken between different dosing regimens, different endpoints, or different species serve as a reference for establishing the uncertainty factors. Ratios of no observed adverse effect levels (NOAELs) have been used for this purpose; statistical summaries of such ratios across sets of chemicals are widely used to guide the setting of uncertainty factors. Given the poor statistical properties of NOAELs, the informativeness of these summary statistics is open to question. To evaluate this, we develop an approach to "calibrate" the ability of NOAEL ratios to reveal true properties of a specified distribution for relative toxicity. A priority of this analysis is to account for dependencies of NOAEL ratios on experimental design and other exogenous factors. Our analysis of NOAEL ratio summary statistics finds (1) that such dependencies are complex and produce pronounced systematic errors and (2) that sampling error associated with typical sample sizes (50 chemicals) is nonnegligible. These uncertainties strongly suggest that NOAEL ratio summary statistics cannot be taken at face value; conclusions based on such ratios reported in well over a dozen published papers should be reconsidered.

Model peptide studies of sequence repeats derived from the intracrystalline biomineralization protein, SM50. I. GVGGR and GMGGQ repeats

We report solution-state pulsed field gradient nmr studies of a native sequence-derived 23-residue peptidomimetic, N alpha-acetyl-QPGVGGRQPGMGGQPGVGGRQPG-C alpha-amid, that incorporates the prevalent GVGGR and GMGGQ repeats found in the sea urchin embryo intracrystalline spicule matrix protein, SM50 (Strongylocentrotus purpuratus). These repeats are sequence homologues of elastin protein repeats (VPGVG, VGGVG, and APGVGV) and spider dragline silk protein repeats (GPGG, GQGG, and QPGYG). Using rotating frame nuclear Overhauser effect (ROE) connectivities, CH alpha proton conformational shifts, 3JNH-CH alpha coupling constants, amide temperature shift coefficients, and pulsed field gradient ROE spectroscopy solvent exchange measurements, we find that the 23-mer peptidomimetic possesses a multiple beta-turn structure in aqueous solution, in equilibria with an extended or coil structure (60% beta-turn: 40% random coil). The GVGGR sequence adopts a double beta-turn conformation that is stabilized by two hydrogen bonds (R7-->V4, R20-->V17; G6-->G3, G19-->G16). The GMGGQ region adopts a single beta-turn conformation that is stabilized by a hydrogen bond involving residues Q14 and M11. Repeating beta-turn structures, or beta-spirals, may play an important role with regard to matrix assembly, protein stability, molecular elasticity, and/or protein-crystal recognition within the spicule mineralized matrix.

Neonatal necrotizing enterocolitis: the long-term perspective

Ten years' experience with neonatal necrotizing enterocolitis (NNEC) was reviewed retrospectively to determine long-term survival and quality of life and to analyze risk factors associated with in-hospital mortality. Institutional records were queried to identify all neonates who required emergent surgical intervention for NNEC. These records were then reviewed and survivors' families interviewed by phone to determine patient status, persistent gastrointestinal problems, and overall quality of life. Once identified, long-term survivors (LTSs) were compared to in-hospital deaths by the analysis of birth weight, gestational age, time interval from birth to diagnosis, indications for laparotomy, and extent of intestinal involvement. Between 1986 and 1996, 69 patients required surgical intervention for NNEC. Eleven patients were lost to follow-up. Of the remaining 58 patients, 31 were ultimately discharged home, with 28 patients having survived an average of 4.18 years. The acute, or in-hospital, mortality rate was 39.1 per cent. Infants who died did so within an average of 23 days postoperatively, and those who were discharged home required an average of 121 days of inpatient convalescence. Twenty-one of the 28 LTSs achieved a normal quality of life with no persistent health problems. One patient required a hepatic-intestinal transplant, and another six had minor problems with frequent diarrhea. Average birth weight, age at NNEC diagnosis, and gestational age were not significantly different between LTSs and those with acute deaths. Aggressive in-hospital care is warranted for infants with NNEC. The excellent quality of life achieved in 75 per cent of survivors implies that the expense of heroic surgical care for these seriously ill premature infants is a worthwhile investment.

Primary cutaneous Aspergillus ustus infection: second reported case

We describe the second case of primary cutaneous Aspergillus ustus infection in an immunocompromised patient. Cutaneous aspergillosis was confirmed both by culture and positive fluorescent antibody staining. Few species of Aspergillus are pathogenic in human beings, and fewer still cause primary cutaneous disease. The only other reported case of aspergillosis from Aspergillus ustus occurred in an immunosuppressed patient who was temporally and geographically separated from ours.

Complications of retained internal bolster after pediatric percutaneous endoscopic gastrostomy

PURPOSE

Percutaneous endoscopic gastrostomy (PEG) has been widely accepted as an efficacious means of nutritional support in the infant and child. A well-described technique uses the Gauderer-Ponsky tube (CR Bard Incorporated, Tewksbury, MA) drawn antegrade through the gastric wall and secured by an internal and external SILASTIC (Dow Corning; Midland, MI) bolster. The majority of reported complications attendant to its use occur secondary to insertion. This report details a less well-described complication of tube removal.

METHODS

Since 1992, 234 pediatric PEGs have been performed using a Gauderer-Ponsky tube. Approximately 6 weeks after the procedure, all catheters were removed and replaced with gastric buttons. The internal bolster was left within the stomach to pass spontaneously.

RESULTS

Five children (2.1%), ages 6 months to 5 years, failed to pass this crossbar. Three subsequently presented with dysphagia and drooling with the internal bolster wedged in the proximal esophagus. All were left with significant residual stricture after endoscopic removal of the crossbar. Two required dilatation and the third underwent operative stricturoplasty. A fourth child returned with intermittent gastric outlet obstruction. The internal bolster was retained in the stomach 4 months after catheter removal. Endoscopic retrieval resulted in resolution of the symptomatology. The final case was found to have an asymptomatic bolster in the stomach approximately 18 months after catheter removal.

CONCLUSIONS

These cases highlight a potential sequelae of pediatric percutaneous endoscopic gastrostomy not previously acknowledged. The significant complications associated with the retained bolster in four of these five children suggests that follow-up should be altered to monitor prompt passage of the crossbar after tube removal.

Evaluation of effect profiles: Functional Observational Battery outcomes

The Functional Observational Battery (FOB) is a neurotoxicity screening assay composed of 25-30 descriptive, scalar, binary, and continuous endpoints. These outcomes have been grouped into six biologically logical domains as a means to interpret the neuroactive properties of tested chemicals (V. C. Moser, 1992, J. Am. Coll. Toxicol. 10(6), 661-669). However, no data-based exploration of these functional domains has been done. We investigated the degree to which experimental data correspond to the domain groupings by examining severity scores from 10 chemicals tested using a standardized protocol for acute exposure (V. C. Moser et al., 1995, J. Toxicol. Environ. Health 45, 173-210) and identifying endpoint groupings (factors) that best describe the interrelationships in the data, allowing a statistical assessment of whether the FOB endpoints break into domains. We also used a standard measure of bivariate association to confirm the results of the factor analysis. Our results show that while there are clear relationships among variables that compose some domains, there is often substantial correlation among endpoints in different domains. In addition, we investigated a related issue concerning the relative power of the chosen endpoint groupings for identifying significant domain effects. Results from a randomization analysis of the 10 chemicals suggest that the neurophysiologic domain structuring may provide some degree of statistical efficiency for identifying effects.

Serum levels of virus burden in early-stage human immunodeficiency virus type 1 disease in women

The fundamental clinical, viral, and immunologic features of early-stage human immunodeficiency virus type 1 (HIV-1) disease were examined in a seroprevalent cohort of 28 men and 14 women assessed longitudinally at three equally dispersed time points over a mean of 43 months. There were no gender differences in the relative risk of developing AIDS-defining end points or death. The median serum RNA levels assessed at the three study time points were 3.3-, 4.9-, and 1.5-fold lower, respectively, in women than in men. This suggests that while serum virus load may be as powerful a correlate of disease status in women as it is in men, the absolute values of the virus levels may be different in the 2 populations. These observations may have implications for the interpretation of levels of virus burden in women for the assessment of disease progression, transmission, and treatment.

On the mental representation of conditional sentences

Four experiments are reported which attempt to externalize subjects' mental representation of conditional sentences, using novel research methods. In Experiment 1, subjects were shown arrays of coloured shapes and asked to rate the degree to which they appeared to be true of conditional statements such as "If the figure is green then it is a triangle". The arrays contained different distributions of the four logically possible cases in which the antecedent or consequent is true or false: TT, TF, FT, and FF. For example, a blue triangle would be FT for the conditional quoted above. In Experiments 2 to 4, subjects were able to construct their own arrays to make conditional either true or false with any distribution of the four cases they wished to choose. The presence and absence of negative components was varied, as was the form of the conditional, being either "if then" as above or "only if": "The figure is green only if it is a triangle". The first findings was that subjects represent conditional in fuzzy way: conditional that include some counter-example TF cases (Experiment 1) may be rated as true, and such cases are often included when subjects construct an array to make the rule true (Experiments 2 to 4). Other findings included a strong tendency to include psychologically irrelevant FT and FF cases in constructed arrays, presumably to show that conditional statements only apply some of the time. A tendency to construct cases in line with the "matching bias" reported on analogous tasks in the literature was found, but only in Experiment 4, where the number of symbols available to construct each case was controlled. The findings are discussed in relation to the major contemporary theories of conditional reasoning based upon inference rules and mental models, neither of which can account for all the results.

Worker exposure to endotoxin, phenolic compounds, and formaldehyde in a fiberglass insulation manufacturing plant

Worker exposures in a fiberglass wool insulation manufacturing plant were studied. The plant used a continuous process and operated at full production during a six-week study. Area samples were used to characterize spatial variability of contaminant levels. Repeated personal samples were used to characterize the distribution and to explore within- and between-worker variability of exposures. The greatest potential for exposure to each of the contaminants was restricted to specific areas of the plant. Area geometric mean concentrations were 1 to 390 ng/m3 for endotoxin and 22 to 414 micrograms/m3 for formaldehyde. There was considerable within-area variation of endotoxin (geometric standard deviation [GSD] 2.6 to 5.5) and formaldehyde (GSD 2.0 to 4.5). Concentrations of phenolic compounds were correlated with endotoxin and were influenced by a relatively high limit of detection. The ranges of personal GM exposures across homogeneous groupings were smaller than the range for the corresponding areas (endotoxin 5.8 to 36.4 ng/m3; formaldehyde 18.1 to 67.4 micrograms/m3). Variability in personal exposure was high. Individual GSDs ranged up to 10, with the mean individual GSD of 3.4 for endotoxin, and up to 12 with mean 3.7 for formaldehyde. Suggested thresholds for acute respiratory effects of endotoxin exposure were frequently exceeded (46% of 8-hr personal samples > 10 ng/m3, 7% > 100 ng/m3). No personal samples exceeded the Occupational Safety and Health Administration permissible exposure level or the American Conference of Government Industrial Hygienists' threshold limit value for formaldehyde; however, 34% were greater than 60 micrograms/m3 and 11% were greater than 120 micrograms/m3. Thus, exposures fell in a range where important exposure-response relationship could be examined.