Showing papers by "University of North Carolina at Chapel Hill published in 2000"

Whatever happened to qualitative description

Abstract: The general view of descriptive research as a lower level form of inquiry has influenced some researchers conducting qualitative research to claim methods they are really not using and not to claim the method they are using: namely, qualitative description. Qualitative descriptive studies have as their goal a comprehensive summary of events in the everyday terms of those events. Researchers conducting qualitative descriptive studies stay close to their data and to the surface of words and events. Qualitative descriptive designs typically are an eclectic but reasonable combination of sampling, and data collection, analysis, and re-presentation techniques. Qualitative descriptive study is the method of choice when straight descriptions of phenomena are desired.

The autism diagnostic observation schedule-generic: a standard measure of social and communication deficits associated with the spectrum of autism.

Abstract: The Autism Diagnostic Observation Schedule-Generic (ADOS-G) is a semistructured, standardized assessment of social interaction, communication, play, and imaginative use of materials for individuals suspected of having autism spectrum disorders. The observational schedule consists of four 30-minute modules, each designed to be administered to different individuals according to their level of expressive language. Psychometric data are presented for 223 children and adults with Autistic Disorder (autism), Pervasive Developmental Disorder Not Otherwise Specified (PDDNOS) or nonspectrum diagnoses. Within each module, diagnostic groups were equivalent on expressive language level. Results indicate substantial interrater and test-retest reliability for individual items, excellent interrater reliability within domains and excellent internal consistency. Comparisons of means indicated consistent differentiation of autism and PDDNOS from nonspectrum individuals, with some, but less consistent, differentiation of autism from PDDNOS. A priori operationalization of DSM-IV/ICD-10 criteria, factor analyses, and ROC curves were used to generate diagnostic algorithms with thresholds set for autism and broader autism spectrum/PDD. Algorithm sensitivities and specificities for autism and PDDNOS relative to nonspectrum disorders were excellent, with moderate differentiation of autism from PDDNOS.

Monolayer-Protected Cluster Molecules

Abstract: In this report, we evaluate the present state of the rapidly emerging field of monolayer-protected cluster (MPC) molecules with regard to their synthesis and monolayer functionalization, their core and monolayer structure, their composition, and their properties. Finally, we canvass some of the important remaining research opportunities involving MPCs.

Mechanisms Linking Work and Family: Clarifying the Relationship Between Work and Family Constructs

Abstract: Work-family research emphasizes the importance of mechanisms that link work and family. However, these mechanisms typically are described in metaphoric terms poorly suited to rigorous research. In this article we translate work-family linking mechanisms into causal relationships between work and family constructs. For each relationship we explain its sign and causal structure and how it is influenced by personal intent. We show how these respecified linking mechanisms constitute theoretical building blocks for developing comprehensive models of the work-family interface.

Service quality, profitability, and the economic worth of customers: What we know and what we need to learn

Abstract: In the past, expenditures on quality have not been explicitly linked to profits because costs and savings were the only variables on which information was available. More recently, evidence about the profit consequences of service quality stemming from other sources has been found. This article synthesizes recent evidence and identifies relationships between service quality and profits that have been and need to be examined. The article views the literature in six categories: (1) direct effects of service quality on profits; (2) offensive effects; (3) defensive effects; (4) the link between perceived service quality and purchase intentions; (5) customer and segment profitability; and (6) key service drivers of service quality, customer retention, and profitability. In each category, the author identifies what is known and then suggests an agenda of relationships needing validation and questions needing answers. The article is organized around a conceptual framework linking the six topics.

On the nature and direction of relationships between constructs and measures.

Abstract: Theory development typically focuses on relationships among theoretical constructs, placing little emphasis on relationships between constructs and measures. In most cases, constructs are treated as causes of their measures. However, this causal flow is sometimes reversed, such that measures are viewed as causes of constructs. Procedures have been developed to identify and estimate models that specify constructs as causes or effects of measures. However, these procedures provide little guidance for determining a priori whether constructs should be specified as causes or effects of their measures. Moreover, these procedures address few of the possible causal structures by which constructs and measures may be related. This article develops principles for specifying the direction and structure of relationships between constructs and measures. These principles are illustrated using examples from psychological, sociological, and organizational research.

The Measure of American Religion: Toward Improving the State of the Art

Abstract: Recently, scholars have devoted renewed attention to the role of religion in American life. Thus, it is important that they use the most effective means available to categorize and study religious groups. However, the most widely used classification scheme in survey research (T.W. Smith 1990) does not capture essential differences between American religious traditions and overlooks significant new trends in religious affiliation. We critique this scheme based on its historical, terminological, and taxonomical inaccuracy and offer a new approach that addresses its shortcomings by using denominational affiliation to place respondents into seven categories grounded in the historical development of American religious traditions. Most important, this new scheme yields more meaningful interpretations because the categories refer to concrete religious traditions. Because of increased accuracy in classification, it also improves model fit and reduces measurement error.

Combining qualitative and quantitative sampling, data collection, and analysis techniques in mixed-method studies.

Abstract: Researchers have increasingly turned to mixed-method techniques to expand the scope and improve the analytic power of their studies. Yet there is still relatively little direction on and much confusion about how to combine qualitative and quantitative techniques. These tech- niques are neither paradigm- nor method-linked; researchers' orientations to inquiry and their methodological commitments will influence how they use them. Examples of sampling combina- tions include criterion sampling from instrument scores, random purposeful sampling, and strat- ified purposeful sampling. Examples of data collection combinations include the use of instru- ments for fuller qualitative description, for validation, as guides for purposeful sampling, and as elicitation devices in interviews. Examples of data analysis combinations include interpretively linking qualitative and quantitative data sets and the transformation processes of qualitizing and quantitizing. © 2000 John Wiley & Sons, Inc. Res Nurs & Health 23:246-255, 2000

Nonstandard Employment Relations: Part-time, Temporary and Contract Work

Abstract: Nonstandard employment relations—such as part-time work, temporary help agency and contract company employment, short-term and contingent work, and independent contracting—have become increasingly prominent ways of organizing work in recent years. Our understanding of these nonstandard work arrangements has been hampered by inconsistent definitions, often inadequate measures, and the paucity of comparative research. This chapter reviews the emerging research on these nonstandard work arrangements. The review emphasizes the multidisciplinary nature of contributions to this field, including research by a variety of sociologists, economists, and psychologists. It also focuses on cross-national research, which is needed to investigate how macroeconomic, political, and institutional factors affect the nature of employment relations. Areas for future research are suggested.

Wnt Signaling in Oncogenesis and Embryogenesis--a Look Outside the Nucleus

Abstract: The Wnt cell-cell signaling pathway plays a critical and evolutionarily conserved role in directing cell fates during embryogenesis. In addition, inappropriate activation of the Wnt signal transduction pathway plays a role in a variety of human cancers. Many recent studies of Wnt signaling have provided mechanistic insight into these dual roles. Here we focus on two areas of rapid advance: (i) the machinery that regulates the stability of the key signal transducer, β-catenin, and (ii) the effect of Wnt signaling on cellular targets outside the nucleus, the actin and microtubule cytoskeletons.

Bad jobs in America: standard and nonstandard employment relations and job quality in the United States

Abstract: The prevalence of nonstandard jobs is a matter of concern if, as many assume, such jobs are bad. We examine the relationship between nonstandard employment (on-call work and day labor, temporary-help agency employment, employment with contract companies, independent contracting, other self-employment, and part-time employment in "conventional" jobs) and exposure to "bad" job characteristics, using data from the 1995 Current Population Survey. Of workers age 18 and over, 31 percent are in some type of nonstandard employment. To assess the link between type of employment and bad jobs, we conceptualize "bad jobs" as those with low pay and without access to health insurance and pension benefits. About one in seven jobs in the United States is bad on these three dimensions. Nonstandard employment strongly increases workers' exposure to bad job characteristics, net of controls for workers' personal characteristics, family status, occupation, and industry. Reprinted by permission of the publisher.

The Cost of Diversity: The Diversification Discount and Inefficient Investment

Abstract: We model the distortions that internal power struggles can generate in the allocation of resources between divisions of a diversified firm. The model predicts that if divisions are similar in the level of their resources and opportunities, funds will be transferred from divisions with poor opportunities to divisions with good opportunities. When diversity in resources and opportunities increases, however, resources can f low toward the most inefficient division, leading to more inefficient investment and less valuable firms. We test these predictions on a panel of diversified U.S. firms during the period from 1980 to 1993 and find evidence consistent with them. THE FUNDAMENTAL QUESTION IN THE THEORY of the firm, raised by Coase ~1937! more than 60 years ago, is how decisions taken inside a hierarchy differ from those taken in the marketplace. Coase suggested that decisions within a hierarchy are determined by power considerations rather than relative prices. If this is indeed the case, why, and when, does the hierarchy dominate the market? A major obstacle to progress in this area has been the lack of data. Data on internal decisions made by firms are generally proprietary. Even when they are available to researchers, it is difficult to find a comparable group of decisions taken in the market. A notable exception is the capital allocation decision in diversified firms. Since 1978, public U.S. companies have been forced to disclose their data on sales, profitability, and investments by major lines of business ~segments!. An analysis of a small sample of multisegment firms reveals that segments correspond, by and large, to distinct internal

Do Corporate Global Environmental Standards Create or Destroy Market Value

Abstract: Arguments can be made on both sides of the question of whether a stringent global corporate environmental standard represents a competitive asset or liability for multinational enterprises (MNEs) investing in emerging and developing markets. Analyzing the global environmental standards of a sample of U.S.-based MNEs in relation to their stock market performance, we find that firms adopting a single stringent global environmental standard have much higher market values, as measured by Tobin'sq, than firms defaulting to less stringent, or poorly enforced host country standards. Thus, developing countries that use lax environmental regulations to attract foreign direct investment may end up attracting poorer quality, and perhaps less competitive, firms. Our results also suggest that externalities are incorporated to a significant extent in firm valuation. We discuss plausible reasons for this observation.

Curvilinearity in the diversification–performance linkage: an examination of over three decades of research

Abstract: While an extensive literature examines the diversification-performance relationship, little agreement exists concerning the nature of this relationship. Both theoretical and empirical disagreements abound. This study synthesizes findings from three decades of research to address major theoretical issues that remain open to debate. We derive three competing models from the literature and empirically assess these using meta-analytic data drawn from 55 previously published studies. The results of our tests indicate that moderate levels of diversification yield higher levels of performance than either limited or extensive diversification. Thus, we provide support for the curvilinear model; that is, performance increases as firms shift from single-business strategies to related diversification, but performance decreases as firms change from related diversification to unrelated diversification. The results also indicate major effects from variation in diversification and performance operationalizations. Copyright © 2000 John Wiley & Sons, Ltd.

Practice parameter: Screening and diagnosis of autism Report of the Quality Standards Subcommittee of the American Academy of Neurology and the Child Neurology Society

Abstract: Autism is a common disorder of childhood, affecting 1 in 500 children. Yet, it often remains unrecognized and undiagnosed until or after late preschool age because appropriate tools for routine developmental screening and screening specifically for autism have not been available. Early identification of children with autism and intensive, early intervention during the toddler and preschool years improves outcome for most young children with autism. This practice parameter reviews the available empirical evidence and gives specific recommendations for the identification of children with autism. This approach requires a dual process: 1) routine developmental surveillance and screening specifically for autism to be performed on all children to first identify those at risk for any type of atypical development, and to identify those specifically at risk for autism; and 2) to diagnose and evaluate autism, to differentiate autism from other developmental disorders.

Varieties of repetitive behavior in autism: comparisons to mental retardation.

Abstract: Systematic study of abnormal repetitive behaviors in autism has been lacking despite the diagnostic significance of such behavior The occurrence of specific topographies of repetitive behaviors as well as their severity was assessed in individuals with mental retardation with and without autism The occurrence of each behavior category, except dyskinesias, was higher in the autism group and autistic subjects exhibited a significantly greater number of topographies of stereotypy and compulsions Both groups had significant patterns of repetitive behavior co-occurrence Autistic subjects had significantly greater severity ratings for compulsions, stereotypy, and self-injury Repetitive behavior severity also predicted severity of autism Although abnormal repetition is not specific to autism, an elevated pattern of occurrence and severity appears to characterize the disorder

Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings.

Abstract: Background and Methods The clinical significance of a distal colorectal polyp is uncertain. We determined the risk of advanced proximal neoplasia, defined as a polyp with villous features, a polyp with high-grade dysplasia, or cancer, among persons with distal hyperplastic or neoplastic polyps as compared with the risk among persons with no distal polyps. We analyzed data from 1994 consecutive asymptomatic adults (age, 50 years or older) who underwent colonoscopic screening for the first time between September 1995 and December 1998 as part of a program sponsored by an employer. The location and histologic features of all polyps were recorded. Colonoscopy to the level of the cecum was completed in 97.0 percent of the patients. Results Sixty-one patients (3.1 percent) had advanced lesions in the distal colon, including 5 with cancer, and 50 (2.5 percent) had advanced proximal lesions, including 7 with cancer. Twenty-three patients with advanced proximal neoplasms (46 percent) had no distal polyps. The prev...

The transcriptome of Arabidopsis thaliana during systemic acquired resistance.

Abstract: Infected plants undergo transcriptional reprogramming during initiation of both local defence and systemic acquired resistance (SAR). We monitored gene-expression changes in Arabidopsis thaliana under 14 different SAR-inducing or SAR-repressing conditions using a DNA microarray representing approximately 25-30% of all A. thaliana genes. We derived groups of genes with common regulation patterns, or regulons. The regulon containing PR-1, a reliable marker gene for SAR in A. thaliana, contains known PR genes and novel genes likely to function during SAR and disease resistance. We identified a common promoter element in genes of this regulon that binds members of a plant-specific transcription factor family. Our results extend expression profiling to definition of regulatory networks and gene discovery in plants.

Image-based visual hulls

Abstract: In this paper, we describe an efficient image-based approach to computing and shading visual hulls from silhouette image data. Our algorithm takes advantage of epipolar geometry and incremental computation to achieve a constant rendering cost per rendered pixel. It does not suffer from the computation complexity, limited resolution, or quantization artifacts of previous volumetric approaches. We demonstrate the use of this algorithm in a real-time virtualized reality application running off a small number of video streams.

Determinants of Adolescent Physical Activity and Inactivity Patterns

Abstract: Objectives. Despite recognition of the important influence of environmental determinants on physical activity patterns, minimal empirical research has been done to assess the impact of environmental/ contextual determinants of physical activity. This article aims to investigate environmental and sociodemographic determinants of physical activity and inactivity patterns among subpopulations of US adolescents. We define en- vironmental determinants as modifiable factors in the physical environment that impose a direct influence on the opportunity to engage in physical activity. The present research examines environmental and sociode- mographic determinants of physical activity and inactiv- ity with the implication that these findings can point toward societal-level intervention strategies for increas- ing physical activity and decreasing inactivity among adolescents. Study Design and Methodology. The study popula- tion consists of nationally representative data from the 1996 National Longitudinal Study of Adolescent Health on 17 766 US adolescents enrolled in US middle and high schools (including 3933 non-Hispanic blacks, 3148 His- panics, and 1337 Asians). Hours/week of inactivity (TV/ video viewing and video/computer games) and times/ week of moderate to vigorous physical activity were collected by questionnaire. Outcome variables were moderate to vigorous physical activity and inactivity, which were broken into categories (physical activity: 0 -2 times/week, 3- 4 times/week, and >5 times/week; inactiv- ity: 0 -10 hours/week, 11-24 hours/week, and >25 hours/ week). Sociodemographic and environmental correlates of physical activity and inactivity were used as exposure and control variables and included sex, age, urban resi- dence, participation in school physical education pro- gram, use of community recreation center, total reported incidents of serious crime in neighborhood, socioeco- nomic status, ethnicity, generation of residence in the United States, presence of mother/father in household, pregnancy status, work status, in-school status, region, and month of interview. Logistic regression models of high versus low and me- dium physical activity and inactivity were used to investi- gate sex and ethnic interactions in relation to environmen- tal and sociodemographic factors to examine evidence for the potential impact of physical education and recreation programs and sociodemographic factors on physical activ- ity and inactivity patterns. Results. Moderate to vigorous physical activity was lower and inactivity higher for non-Hispanic black and Hispanic adolescents. Participation in school physical education programs was considerably low for these ado- lescents and decreased with age. Participation in daily school physical education (PE) program classes (adjusted odds ratio (AOR): 2.21; confidence interval (CI): 1.82- 2.68) and use of a community recreation center (AOR: 1.75; CI: 1.56 -1.96) were associated with an increased likelihood of engaging in high level moderate to vigor- ous physical activity. Maternal education was inversely associated with high inactivity patterns; for example, having a mother with a graduate or professional degree was associated with an AOR of .61 (CI: .48-.76) for high inactivity. High family income was associated with in- creased moderate to vigorous physical activity (AOR: 1.43; CI: 1.22-1.67) and decreased inactivity (AOR: .70; CI: .59 -.82). High neighborhood serious crime level was as- sociated with a decreased likelihood of falling in the highest category of moderate to vigorous physical activ- ity (AOR: .77; CI: .66 -.91). Conclusions. These results show important associa- tions between modifiable environmental factors, such as participation in school PE and community recreation pro- grams, with activity patterns of adolescents. Despite the marked and significant impact of participation in school PE programs on physical activity patterns of US adoles- cents, few adolescents participated in such school PE programs; only 21.3% of all adolescents participated in 1

Noninvasive Diagnosis by Doppler Ultrasonography of Fetal Anemia Due to Maternal Red-Cell Alloimmunization

Abstract: Background Invasive techniques such as amniocentesis and cordocentesis are used for diagnosis and treatment in fetuses at risk for anemia due to maternal red-cell alloimmunization. The purpose of our study was to determine the value of noninvasive measurements of the velocity of blood flow in the fetal middle cerebral artery for the diagnosis of fetal anemia. Methods We measured the hemoglobin concentration in blood obtained by cordocentesis and also the peak velocity of systolic blood flow in the middle cerebral artery in 111 fetuses at risk for anemia due to maternal red-cell alloimmunization. Peak systolic velocity was measured by Doppler velocimetry. To identify the fetuses with anemia, the hemoglobin values of those at risk were compared with the values in 265 normal fetuses. Results Fetal hemoglobin concentrations increased with increasing gestational age in the 265 normal fetuses. Among the 111 fetuses at risk for anemia, 41 fetuses did not have anemia; 35 had mild anemia; 4 had moderate anemia; an...

Voluntary Disclosure and Equity Offerings: Reducing Information Asymmetry or Hyping the Stock?*

Abstract: We examine corporate disclosure activity around seasoned equity offerings and its relationship to stock prices. Beginning six months before the offering, our sample issuing firms dramatically increase their disclosure activity, particularly for the categories of disclosure over which firms have the most discretion. The increase is significant after controlling for the firm's current and future earnings performance and tends to be largest for firms with selling shareholders participating in the offering. However, there is no change in the frequency of forward-looking statements prior to the equity offering, something that is expressly discouraged by the securities law. Firms that maintain a consistent level of disclosure experience price increases prior to the offering, and only minor price declines at the offering announcement relative to the control firms, suggesting that disclosure may have reduced the information asymmetry inherent in the offering. Firms that substantially increase their disclosure activity in the six months before the offering also experience price increases prior to the offering relative to the control firms, but suffer much larger price declines at the announcement of their intent to issue equity, suggesting that the disclosure increase may have been used to “hype the stock” and the market may have partially corrected for the earlier price increase. Firms that maintain a consistent disclosure level have no unusual return behavior relative to the control firms subsequent to the announcement, while the firms that “hyped” their stock continue to suffer negative returns, providing further evidence that the increased disclosure activity may have been hype, and suggesting that the hype may have been successful in lowering the firms' cost of equity capital.

Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells.

Abstract: Biomethylation is considered a major detoxification pathway for inorganic arsenicals (iAs). According to the postulated metabolic scheme, the methylation of iAs yields methylated metabolites in which arsenic is present in both pentavalent and trivalent forms. Pentavalent mono- and dimethylated arsenicals are less acutely toxic than iAs. However, little is known about the toxicity of trivalent methylated species. In the work reported here the toxicities of iAs and trivalent and pentavalent methylated arsenicals were examined in cultured human cells derived from tissues that are considered a major site for iAs methylation (liver) or targets for carcinogenic effects associated with exposure to iAs (skin, urinary bladder, and lung). To characterize the role of methylation in the protection against toxicity of arsenicals, the capacities of cells to produce methylated metabolites were also examined. In addition to human cells, primary rat hepatocytes were used as methylating controls. Among the arsenicals examined, trivalent monomethylated species were the most cytotoxic in all cell types. Trivalent dimethylated arsenicals were at least as cytotoxic as trivalent iAs (arsenite) for most cell types. Pentavalent arsenicals were significantly less cytotoxic than their trivalent analogs. Among the cell types examined, primary rat hepatocytes exhibited the greatest methylation capacity for iAs followed by primary human hepatocytes, epidermal keratinocytes, and bronchial epithelial cells. Cells derived from human bladder did not methylate iAs. There was no apparent correlation between susceptibility of cells to arsenic toxicity and their capacity to methylate iAs. These results suggest that (1) trivalent methylated arsenicals, intermediary products of arsenic methylation, may significantly contribute to the adverse effects associated with exposure to iAs, and (2) high methylation capacity does not protect cells from the acute toxicity of trivalent arsenicals.

A new genotype of hepatitis B virus: complete genome and phylogenetic relatedness

Abstract: The hepatitis B virus (HBV) genotype was determined in a total of 121 plasma samples collected in France and the US from patients chronically infected with HBV HBV genotype A was predominant in this collection, appearing in 66 samples (54%), while genotypes B, C, D, E and F occurred in 4 (3%), 14 (12%), 23 (19%), 1 (1%) and 0 (0%) of samples, respectively However, the genotype of a total of 13 (11%) samples (2 from France, 11 from the US) could not be determined with the methodology used Sequence analysis, and subsequent phylogenetic analysis of the complete genome and the individual open reading frames, showed that the virus isolate from these samples was 3248 bp long and, phylogenetically, did not cluster with any of the known genotypes This strain was provisionally called HBV genotype G Virus isolates that were obtained from geographically separated regions like France and the US were closely related to each other All virus strains analysed contained some characteristic differences when compared to genotype A: a translational stop codon at aa 2 and 28 of the preCore region; a 36 nt (12 aa) insert in the amino-terminal part of the Core antigen (HBcAg); a 2 aa deletion in the carboxy-terminal part of HBcAg; and a 1 aa deletion in the preS1 open reading frame The deduced amino acid sequence of HBsAg suggests that this newly discovered genotype G strain belongs to serological group adw2

Financial Accounting Information, Organizational Complexity and Corporate Governance Systems

Abstract: The purpose of this paper is to investigate how governance systems of large public U.S. corporations vary with information properties of numbers produced by their financial accounting systems. We argue that in firms whose current accounting numbers do a relatively poor job of capturing the effects of the firm's current activities and outcomes on shareholder value, the accounting numbers are less effective in the governance setting. We predict that such firms will substitute costly governance mechanisms to compensate for their less useful accounting numbers. We explore whether governance systems vary with the timeliness of earnings by examining the cross-sectional relation between proxies for earnings timeliness and subsequent corporate governance systems of 784 firms in the Fortune 1000. The governance systems we consider include board composition, stockholdings of inside and outside directors, ownership concentration and the structure of executive compensation. Our results support a significant negative relation between our timeliness metrics and subsequent costly corporate governance mechanisms after controlling for other firm characteristics.

NF-κB-Induced Loss of MyoD Messenger RNA: Possible Role in Muscle Decay and Cachexia

Abstract: MyoD regulates skeletal muscle differentiation (SMD) and is essential for repair of damaged tissue. The transcription factor nuclear factor kappa B (NF-kappaB) is activated by the cytokine tumor necrosis factor (TNF), a mediator of skeletal muscle wasting in cachexia. Here, the role of NF-kappaB in cytokine-induced muscle degeneration was explored. In differentiating C2C12 myocytes, TNF-induced activation of NF-kappaB inhibited SMD by suppressing MyoD mRNA at the posttranscriptional level. In contrast, in differentiated myotubes, TNF plus interferon-gamma (IFN-gamma) signaling was required for NF-kappaB-dependent down-regulation of MyoD and dysfunction of skeletal myofibers. MyoD mRNA was also down-regulated by TNF and IFN-gamma expression in mouse muscle in vivo. These data elucidate a possible mechanism that may underlie the skeletal muscle decay in cachexia.

Structural basis of IAP recognition by Smac/DIABLO

Abstract: Apoptosis is an essential process in the development and homeostasis of all metazoans. The inhibitor-of-apoptosis (IAP) proteins suppress cell death by inhibiting the activity of caspases; this inhibition is performed by the zinc-binding BIR domains of the IAP proteins. The mitochondrial protein Smac/DIABLO promotes apoptosis by eliminating the inhibitory effect of IAPs through physical interactions. Amino-terminal sequences in Smac/DIABLO are required for this function, as mutation of the very first amino acid leads to loss of interaction with IAPs and concomitant loss of Smac/DIABLO function. Here we report the high-resolution crystal structure of Smac/DIABLO complexed with the third BIR domain (BIR3) of XIAP. Our results show that the N-terminal four residues (Ala-Val-Pro-Ile) in Smac/DIABLO recognize a surface groove on BIR3, with the first residue Ala binding a hydrophobic pocket and making five hydrogen bonds to neighbouring residues on BIR3. These observations provide a structural explanation for the roles of the Smac N terminus as well as the conserved N-terminal sequences in the Drosophila proteins Hid/Grim/Reaper. In conjunction with other observations, our results reveal how Smac may relieve IAP inhibition of caspase-9 activity. In addition to explaining a number of biological observations, our structural analysis identifies potential targets for drug screening.

Epidemiology of Concussion in Collegiate and High School Football Players

Abstract: Despite evolutionary changes in protective equipment, head injury remains common in football. We investigated concussion in football and associated epidemiologic issues such as 1) incidence of injury, 2) common signs and symptoms, and 3) patterns in making return-to-play decisions. We received 242 of 392 surveys (62%) that were sent to high school and collegiate certified athletic trainers at the beginning of three football seasons. Of the 17,549 football players represented, 888 (5.1%) sustained at least one concussion, and 131 (14.7% of the 888) sustained a second injury during the same season. The greatest incidence of concussion was found at the high school (5.6%) and collegiate division III (5.5%) levels, suggesting that there is an association between level of play and the proportion of players injured. Players who sustained one concussion in a season were three times more likely to sustain a second concussion in the same season compared with uninjured players. Contact with artificial turf appears to be associated with a more serious concussion than contact with natural grass. Only 8.9% of all injuries involved loss of consciousness, while 86% involved a headache. Overall, 30.8% of all players sustaining a concussion returned to participation on the same day of injury.