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Multivariate
Terms modified by Multivariate Selected AbstractsMultivariate correlates of extinction proneness in a naturally fragmented landscapeDIVERSITY AND DISTRIBUTIONS, Issue 4 2007James I. Watling ABSTRACT Habitat loss and fragmentation threaten a large proportion of terrestrial biodiversity, and identifying the ecological traits associated with extinction proneness is of widespread interest. We used a multivariate statistical approach to identify combinations of ecological traits that best allowed us to identify extinction-prone amphibians and reptiles in a fragmented landscape in north-eastern Bolivia. Extinction-prone amphibians were rare and did not utilize the savannah matrix separating forest islands, whereas extinction-prone reptiles were trophically specialized. Rarity and matrix aversion are among the most widely reported correlates to extinction proneness, and we argue that an increased understanding of their role as drivers of extinction processes is necessary. We suggest that the absence of reptilian vertebrate predators may exacerbate trophic cascades in habitat patches. [source] Association between serum bicarbonate and death in hemodialysis patients: Is it better to be acidotic or alkalotic?HEMODIALYSIS INTERNATIONAL, Issue 1 2005D.Y.J. Wu The optimal acid base status for survival in maintenance hemo-dialysis (MHD) patients (pts) remains controversial. According to some reports acidosis is associated with improved survival in MHD pts, i.e., reverse epidemiology. We examined associations between baseline (first 3-month averaged) serum bicarbonate (HCO3), divided into 12 categories, and 2-yr mortality in 56,376 MHD pts across the US after controlling for confounding effects of malnutrition-inflammation complex syndrome (MICS). Three sets of Cox regression models were evaluated to estimate hazard ratios (HR) of death and 95% confidence intervals (CI): (1) Unadjusted; (2) Multivariate adjusted for case-mix (age, gender, diabetes, race, insurance, marital status, vintage, standardized mortality ratio, residual renal function, dialysate HCO3, and Kt/V); and (3) Additional adjustments for 8 markers of MICS (body mass index, serum albumin, creatinine, ferritin, TIBC, dietary protein intake, WBC and lymphocyte counts). See Figure for HR and 95% CI: We conclude that, although high HCO3 levels appear to be associated with increased mortality in MHD pts, this paradoxical effect is almost entirely due to the overwhelming impact of MICS on survival. [source] Use of Medicare and Department of Veterans Affairs Health Care by Veterans with Dementia: A Longitudinal AnalysisJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 10 2009Carolyn W. Zhu PhD The objectives of this study were to examine longitudinal patterns of Department of Veterans Affairs (VA),only use, dual VA and Medicare use, and Medicare-only use by veterans with dementia. Data on VA and Medicare use were obtained from VA administrative datasets and Medicare claims (1998,2001) for 2,137 male veterans who, in 1997, used some VA services, had a formal diagnosis of Alzheimer's disease or vascular dementia in the VA, and were aged 65 and older. Generalized ordered logit models were used to estimate the effects of patient characteristics on use group over time. In 1998, 41.7% of the sample were VA-only users, 55.4% were dual users, and 2.9% were Medicare-only users. By 2001, 30.4% were VA-only users, 51.5% were dual users, and 18.1% were Medicare-only users. Multivariate results show that greater likelihood of Medicare use was associated with older age, being white, being married, having higher education, having private insurance or Medicaid, having low VA priority level, and living in a nursing home or dying during the year. Higher comorbidities were associated with greater likelihood of dual use as opposed to any single system use. Alternatively, number of functional limitations was associated with greater likelihood of Medicare-only use and less likelihood of VA-only use. These results imply that different aspects of veterans' needs have differential effects on where they seek care. Efforts to coordinate care between VA and Medicare providers are necessary to ensure that patients receive high-quality care, especially patients with multiple comorbidities. [source] Movement trajectories and habitat partitioning of small mammals in logged and unlogged rain forests on BorneoJOURNAL OF ANIMAL ECOLOGY, Issue 5 2006KONSTANS WELLS Summary 1Non-volant animals in tropical rain forests differ in their ability to exploit the habitat above the forest floor and also in their response to habitat variability. It is predicted that specific movement trajectories are determined both by intrinsic factors such as ecological specialization, morphology and body size and by structural features of the surrounding habitat such as undergrowth and availability of supportive structures. 2We applied spool-and-line tracking in order to describe movement trajectories and habitat segregation of eight species of small mammals from an assemblage of Muridae, Tupaiidae and Sciuridae in the rain forest of Borneo where we followed a total of 13 525 m path. We also analysed specific changes in the movement patterns of the small mammals in relation to habitat stratification between logged and unlogged forests. Variables related to climbing activity of the tracked species as well as the supportive structures of the vegetation and undergrowth density were measured along their tracks. 3Movement patterns of the small mammals differed significantly between species. Most similarities were found in congeneric species that converged strongly in body size and morphology. All species were affected in their movement patterns by the altered forest structure in logged forests with most differences found in Leopoldamys sabanus. However, the large proportions of short step lengths found in all species for both forest types and similar path tortuosity suggest that the main movement strategies of the small mammals were not influenced by logging but comprised generally a response to the heterogeneous habitat as opposed to random movement strategies predicted for homogeneous environments. 4Overall shifts in microhabitat use showed no coherent trend among species. Multivariate (principal component) analysis revealed contrasting trends for convergent species, in particular for Maxomys rajah and M. surifer as well as for Tupaia longipes and T. tana, suggesting that each species was uniquely affected in its movement trajectories by a multiple set of environmental and intrinsic features. [source] Multivariate and geometric morphometrics in the analysis of sexual dimorphism variation in Podarcis lizardsJOURNAL OF MORPHOLOGY, Issue 2 2007Antigoni Kaliontzopoulou Abstract Podarcis bocagei and P. carbonelli are two closely related lacertid species, very similar morphologically and ecologically. We investigated sexual dimorphism patterns presented by both species in allopatry and in sympatry. Sexual size and shape dimorphism patterns were analyzed using both multivariate and geometric morphometric techniques. Multivariate morphometrics revealed a marked sexual dimorphism in both species,males being larger with more robust habitus and females presenting a longer trunk. General patterns of sexual size dimorphism are not modified in sympatry, although there is evidence for some morphological change in male head size. The application of geometric morphometrics offered a more detailed image of head shape and revealed that males present a more developed tympanic area than do females, while females have a more rounded head. Differences in the degree of sexual shape dimorphism were detected in sympatry, but no consistent patterns were observed. From the results of the study, and based on previous knowledge on the populations studied, we conclude that the morphological differences observed are probably not caused by exploitative competition between the species, but rather appear attributable to the modification of the relative influence of sexual and natural selection on both sexes. J. Morphol., 2007. © 2007 Wiley-Liss, Inc. [source] Range-wide phylogeography and gene zones in Pinus pinaster Ait. revealed by chloroplast microsatellite markersMOLECULAR ECOLOGY, Issue 10 2007GABRIELE BUCCI Abstract Some 1339 trees from 48 Pinus pinaster stands were characterized by five chloroplast microsatellites, detecting a total of 103 distinct haplotypes. Frequencies for the 16 most abundant haplotypes (pk > 0.01) were spatially interpolated over a lattice made by 430 grid points. Fitting of spatially interpolated values on raw haplotype frequencies at the same geographical location was tested by regression analysis. A range-wide ,diversity map' based on interpolated haplotype frequencies allowed the identification of one ,hotspot' of diversity in central and southeastern Spain, and two areas of low haplotypic diversity located in the western Iberian peninsula and Morocco. Principal component analysis (PCA) carried out on haplotypes frequency surfaces allowed the construction of a colour-based ,synthetic' map of the first three PC components, enabling the detection of the main range-scale genetic trends and the identification of three main ,gene pools' for the species: (i) a ,southeastern' gene pool, including southeastern France, Italy, Corsica, Sardinia, Pantelleria and northern Africa; (ii) an ,Atlantic' gene pool, including all the western areas of the Iberian peninsula; and (iii) a ,central' gene pool, located in southeastern Spain. Multivariate and amova analyses carried out on interpolated grid point frequency values revealed the existence of eight major clusters (,gene zones'), whose genetic relationships were related with the history of the species. In addition, demographic models showed more ancient expansions in the eastern and southern ranges of maritime pine probably associated to early postglacial recolonization. The delineation of the gene zones provides a baseline for designing conservation areas in this key Mediterranean pine. [source] Evidence of genetic distinction and long-term population decline in wolves (Canis lupus) in the Italian ApenninesMOLECULAR ECOLOGY, Issue 3 2004V. Lucchini Abstract Historical information suggests the occurrence of an extensive human-caused contraction in the distribution range of wolves (Canis lupus) during the last few centuries in Europe. Wolves disappeared from the Alps in the 1920s, and thereafter continued to decline in peninsular Italy until the 1970s, when approximately 100 individuals survived, isolated in the central Apennines. In this study we performed a coalescent analysis of multilocus DNA markers to infer patterns and timing of historical population changes in wolves surviving in the Apennines. This population showed a unique mitochondrial DNA control-region haplotype, the absence of private alleles and lower heterozygosity at microsatellite loci, as compared to other wolf populations. Multivariate, clustering and Bayesian assignment procedures consistently assigned all the wolf genotypes sampled in Italy to a single group, supporting their genetic distinction. Bottleneck tests showed evidences of population decline in the Italian wolves, but not in other populations. Results of a Bayesian coalescent model indicate that wolves in Italy underwent a 100- to 1000-fold population contraction over the past 2000,10 000 years. The population decline was stronger and longer in peninsular Italy than elsewhere in Europe, suggesting that wolves have apparently been genetically isolated for thousands of generations south of the Alps. Ice caps covering the Alps at the Last Glacial Maximum (c. 18 000 years before present), and the wide expansion of the Po River, which cut the alluvial plains throughout the Holocene, might have provided effective geographical barriers to wolf dispersal. More recently, the admixture of Alpine and Apennine wolf populations could have been prevented by deforestation, which was already widespread in the fifteenth century in northern Italy. This study suggests that, despite the high potential rates of dispersal and gene flow, local wolf populations may not have mixed for long periods of time. [source] Age-Specific Differences in Women with Implantable Cardioverter Defibrillators: An International Multi Center StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2008LAUREN D. VAZQUEZ M.S. Background: Common psychological adjustment difficulties have been identified for groups of implantable cardioverter defibrillator patients, such as those who are young (<50 years old), have been shocked, and are female. Specific aspects and concerns, such as fears of death or shock and body image concerns, that increase the chance of distress, have not been examined in different aged female implantable cardioverter defibrillator (ICD) recipients. The aim of the study was to investigate these areas of adjustment across three age groups of women from multiple centers. Methods: Eighty-eight female ICD patients were recruited at three medical centers: Shands Hospital at the University of Florida, Brigham and Women's Hospital in Boston, and Royal North Shore Hospital in Sydney, Australia. Women completed individual psychological assessment batteries, measuring the constructs of shock anxiety, death anxiety, and body image concerns. Medical record review was conducted for all patients regarding cardiac illnesses and ICD-specific data. Results: Multivariate and univariate analyses of variance revealed that younger women reported significantly higher rates of shock and death anxiety (Pillai's F = 3.053, P = 0.018, ,2p= 0.067) and significantly greater body image concerns (Pillai's F = 4.198, P = 0.018, ,2p= 0.090) than middle- and older-aged women. Conclusions: Women under the age of 50 appear to be at greater risk for the development of psychosocial distress associated with shock anxiety, death anxiety, and body image. Clinical-based strategies and interventions targeting these types of adjustment difficulties in younger women may allow for improved psychosocial and quality of life outcomes. [source] Clinical Predictors of Defibrillation Thresholds with an Active Pectoral Pulse Generator Lead SystemPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2002DENICE M. HODGSON HODGSON, D.M., et al.: Clinical Predictors of Defibrillation Thresholds with an Active Pectoral Pulse Generator Lead System. Active pectoral pulse generators are used routinely for initial ICD placement because they reduce DFTs and simplify the implantation procedure. Despite the common use of these systems, little is known regarding the clinical predictors of defibrillation efficacy with active pulse generator lead configurations. Such predictors would be helpful to identify patients likely to require higher output devices or more complicated implantations. This was a prospective evaluation of DFT using a uniform testing protocol in 102 consecutive patients with an active pectoral can and dual coil transvenous lead. For each patient, the DFT was measured with a step-down protocol. In addition, 34 parameters were assessed including standard clinical echocardiographic and radiographic measures. Multivariate stepwise regression analysis was performed to identify independent predictors of the DFT. The mean DFT was 9.3 ± 4.6 J and 93% (95/102) of patients had a DFT , 15 J. The QRS duration, interventricular septum thickness, left ventricular mass, and mass index were significant but weak (R < 0.3) univariate predictors of DFT. The left ventricular mass was the only independent predictor by multivariate analysis, but this parameter accounted for < 5% of the variability of DFT measured (adjusted R2= 0.047, P = 0.017). The authors concluded that an acceptable DFT (< 15 J) is observed in > 90% of patients with this dual coil and active pectoral can lead system. Clinical factors are of limited use for predicting DFTs and identifying those patients who will have high thresholds. [source] Growth curves of pediatric patients with biliary atresia following living donor liver transplantation: Factors that influence post-transplantation growthPEDIATRIC TRANSPLANTATION, Issue 7 2007Takeshi Saito Abstract:, We evaluated the growth curves of children with BA after LDLT, and identified factors influencing growth velocity one-yr after LDLT (,Z). The clinical data of 51 children with BA, who had an LDLT at our center from 2001 to 2005, were retrospectively reviewed. The Z scores for height and weight, and ,Z were studied. The correlation between ,Z and various clinical factors was evaluated statistically. Multivariate stepwise analyses were performed for ,Z. The average height and weight Z scores at the time of LDLT were ,1.34 ± 1.36 (±s.d.) and ,0.78 ± 1.15, respectively. Among 30 BA recipients with stable liver function after transplant, weight returned to normal one-yr post-transplantation. However, height did not return to normal even by the third post-transplantation year. On multivariate analyses, 73% of the variance in height ,Z could be accounted for by factors such as standardized height at the time of LDLT (proportion of variance: 38%), number of steroid pulse treatments (17%), donor age (10%), and the presence of HVS (9%). Fifty-four percentage of the variance in weight ,Z could be accounted for by factors such as standardized weight at the time of LDLT (37%) and the total steroid dose given (17%). Height and weight status at the time of LDLT likely have the strongest impact on ,Z. Additional factors include steroid exposure, age of the living donor, and presence of HVS, all of which should be considered to improve post-transplantation growth. [source] Risk Factors for Mortality of Bacteremic Patients in the Emergency DepartmentACADEMIC EMERGENCY MEDICINE, Issue 8 2009Jiun-Nong Lin MD Abstract Objectives:, Patients with bacteremia have a high mortality and generally require urgent treatment. The authors conducted a study to describe bacteremic patients in emergency departments (EDs) and to identify risk factors for mortality. Methods:, Bacteremic patients in EDs were identified retrospectively at a university hospital from January 2007 to December 2007. Demographic characteristics, underlying illness, clinical conditions, microbiology, and the source of bacteremia were collected and analyzed for their association with 28-day mortality. Results:, During the study period, 621 cases (50.2% male) were included, with a mean (±SD) age of 62.8 (±17.4) years. The most common underlying disease was diabetes mellitus (39.3%). Escherichia coli (39.2%) was the most frequently isolated pathogen. The most common source of bacteremia was urinary tract infection (41.2%), followed by primary bacteremia (13.2%). The overall 28-day mortality rate was 12.6%. Multivariate stepwise logistic regression analysis showed age > 60 years (odds ratio [OR] = 2.52, 95% confidence interval [CI] = 1.29 to 4.92, p = 0.007), malignancy (OR = 2.66, 95% CI = 1.44 to 4.91, p = 0.002), liver cirrhosis (OR = 2.08, 95% CI = 1.02 to 4.26, p = 0.044), alcohol use (OR = 5.73, 95% CI = 2.10 to 15.63, p = 0.001), polymicrobial bacteremia (OR = 3.99, 95% CI = 1.75 to 9.10, p = 0.001), anemia (OR = 2.33, 95% CI = 1.34 to 4.03, p = 0.003), and sepsis (OR = 1.94, 95% CI = 1.16 to 3.37, p = 0.019) were independent risk factors for 28-day mortality. Conclusions:, Bacteremic patients in the ED have a high mortality, particularly with these risk factors. It is important for physicians to recognize the factors that potentially contribute to mortality of bacteremic patients in the ED. [source] Linear Model Theory: Univariate, Multivariate, and Mixed Models edited by Muller, K. E. and Stewart, P. W.BIOMETRICS, Issue 1 2007Article first published online: 16 APR 200 No abstract is available for this article. [source] Spontaneous tumour rupture and prognosis in patients with hepatocellular carcinomaBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 9 2002C.-N. Yeh Background: Hepatocellular carcinoma (HCC) is a common disease in Taiwan. Ruptured HCC is an uncommon and potentially fatal complication of the condition. Information on the impact of ruptured HCC on hepatic resection is, however, limited. Methods: The clinical features of 60 patients with ruptured HCC who underwent hepatic resection from 1986 to 1998 were reviewed. Clinical features and factors influencing the outcome of 475 patients with non-ruptured HCC were used for comparison. Results: Of 535 surgically resected HCCs, 60 (11·2 per cent) were ruptured. Univariate analysis showed that sudden onset of abdominal pain, physical signs of haemodynamic unstability, reduced haemoglobin level and a raised aspartate aminotransferase level were more frequently found in patients with ruptured HCC than in those with non-ruptured tumours. Multivariate stepwise logistic regression analysis revealed sudden-onset abdominal pain to be the only independently significant factor in patients in the ruptured HCC group. The 1-, 3- and 5-year survival rates of patients with non-ruptured HCC were 72·1, 47·3 and 33·9 per cent, and those of patients with ruptured HCC were 54·2, 35·0 and 21·2 per cent respectively. Similar overall survival rates were found in patients with ruptured and non-ruptured HCC, although patients in the non-ruptured HCC group had a significantly better disease-free survival rate (P = 0·023). Conclusion: The presence of sudden-onset abdominal pain is the only independent indicator of ruptured HCC. Hepatic resection, when feasible, is the treatment of choice and can result in an overall survival rate comparable to that of patients with non-ruptured HCC. © 2002 British Journal of Surgery Society Ltd [source] Cutting to cope , a modern adolescent phenomenonCHILD: CARE, HEALTH AND DEVELOPMENT, Issue 5 2010B. Hall Abstract Background The frequency of young people cutting themselves appears to be increasing, with one review estimating the current prevalence across the UK to be between 1 in 12 and 1 in 15. Aim To identify factors that are associated with self-harm by cutting, and more especially coping strategies that if encouraged might reduce such behaviour. Method Multivariate and exploratory factor analysis were used to analyse the results from a survey of the pupils attending four large comprehensive schools in the North of England where the frequency of cutting behaviour was causing concern. Results Three factors were identified from the analysis , Social & Active Coping, Seeking External Solutions and Non-Productive Coping. The Social & Active Coping was the only factor that significantly correlated with non-cutting behaviour. Conclusions The fostering of the elements that make up Social & Active Coping , namely working successfully and feeling a sense of achievement, together with positive friendship networks and positive diversions, including physical recreation, will help to minimize young people's sense of needing to cope by cutting themselves. [source] Interpolation processes using multivariate geostatistics for mapping of climatological precipitation mean in the Sannio Mountains (southern Italy)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2005Nazzareno Diodato Abstract The spatial variability of precipitation has often been a topic of research, since accurate modelling of precipitation is a crucial condition for obtaining reliable results in hydrology and geomorphology. In mountainous areas, the sparsity of the measurement networks makes an accurate and reliable spatialization of rainfall amounts at the local scale difficult. The purpose of this paper is to show how the use of a digital elevation model can improve interpolation processes at the subregional scale for mapping the mean annual and monthly precipitation from rainfall observations (40 years) recorded in a region of 1400 km2 in southern Italy. Besides linear regression of precipitation against elevation, two methods of interpolation are applied: inverse squared distance and ordinary cokriging. Cross-validation indicates that the inverse distance interpolation, which ignores the information on elevation, yields the largest prediction errors. Smaller prediction errors are produced by linear regression and ordinary cokriging. However, the results seem to favour the multivariate geostatistical method including auxiliary information (related to elevation). We conclude that ordinary cokriging is a very flexible and robust interpolation method because it can take into account several properties of the landscape; it should therefore be applicable in other mountainous regions, especially where precipitation is an important geomorphological factor. Copyright © 2005 John Wiley & Sons, Ltd. [source] Statistical approaches in landscape genetics: an evaluation of methods for linking landscape and genetic dataECOGRAPHY, Issue 5 2009Niko Balkenhol The goal of landscape genetics is to detect and explain landscape effects on genetic diversity and structure. Despite the increasing popularity of landscape genetic approaches, the statistical methods for linking genetic and landscape data remain largely untested. This lack of method evaluation makes it difficult to compare studies utilizing different statistics, and compromises the future development and application of the field. To investigate the suitability and comparability of various statistical approaches used in landscape genetics, we simulated data sets corresponding to five landscape-genetic scenarios. We then analyzed these data with eleven methods, and compared the methods based on their statistical power, type-1 error rates, and their overall ability to lead researchers to accurate conclusions about landscape-genetic relationships. Results suggest that some of the most commonly applied techniques (e.g. Mantel and partial Mantel tests) have high type-1 error rates, and that multivariate, non-linear methods are better suited for landscape genetic data analysis. Furthermore, different methods generally show only moderate levels of agreement. Thus, analyzing a data set with only one method could yield method-dependent results, potentially leading to erroneous conclusions. Based on these findings, we give recommendations for choosing optimal combinations of statistical methods, and identify future research needs for landscape genetic data analyses. [source] Analysis of dust pollution in slate and granite transformation plantsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2007Celestino Ordóñez Abstract The production of dust in natural stone transformation plants causes respiratory illnesses in workers that, over time, may seriously affect their physical health. In this article we study dust contamination in a number of ornamental slate and granite transformation plants located in Galicia, in northwest Spain. Using dust concentration measures combined with other factors that increase or decrease the noxious effects of dust (noise, duration over time, etc.), and applying multivariate and geostatistical techniques, we were able to construct dust concentration and associated environmental impact maps. The results were integrated in a GIS (Geographical Information System), which allows us to view the contamination maps, as also information on the machinery used, the associated work stations, the most contaminated areas of each plant, etc. This information was then used to analyze the problem in each plant and to compare results between plants. We propose a method designed to reduce worker exposure to dust using an individualised dust capture system at each of the work stations. The pollution control system and its characteristics were finally incorporated into the GIS to allow interested parties such as the managers of the plants studied or people interested in designing a new plant to consult the available information. © 2007 American Institute of Chemical Engineers Environ Prog, 2007. [source] A test of the community conditioning hypothesis: Persistence of effects in model ecological structures dosed with the jet fuel jp-8ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2000Wayne G. Landis Abstract The foundation of the community conditioning hypothesis, the persistence of effects, was tested in a series of microcosm experiments. Experiments were conducted with the water-soluble fraction of the turbine fuel JP-8 using the standard protocols for the standardized aquatic microcosm (SAM). A repeat trial was conducted using the SAM protocol but with a 126-d test period, twice the standard duration. The results were examined using a variety of conventional univariate, multivariate, and graphical techniques. The principal conclusions were as follows. Effects are persistent in these model ecological systems long after the degradation of the toxicant. Patterns of impacts are detectable at concentrations 15 times lower than an experimentally derived single-species EC50. The replicate experiments are not replicable in the specific, but the broad pattern of the disruption of algal- herbivore dynamics followed by more subtle effects are consistently repeated. The durability of the indirect effects and therefore the information about historical events appears to be a consistent feature of these microcosm systems. The identity of the treatment groups persists. The critical features of the community conditioning hypothesis,persistence of information within ecologicalsystems and the reappearance of patterns and therefore the nonequilibrium dynamics,are again confirmed. The implications of these findings for environmental toxicology, monitoring, and ecological risk assessment are discussed. [source] Testing for separability of space,time covariancesENVIRONMETRICS, Issue 8 2005Matthew W. Mitchell Abstract Separable space,time covariance models are often used for modeling in environmental sciences because of their computational benefits. Unfortunately, there are few formal statistical tests for separability. We adapt a likelihood ratio test based on multivariate repeated measures to the spatio,temporal context. We apply this test to an environmental monitoring data set. Copyright © 2005 John Wiley & Sons, Ltd. [source] Valproate-induced thrombocytopenia: a prospective monotherapy studyEPILEPSIA, Issue 3 2008Wassim Nasreddine Summary Purpose: The frequency of valproate (VPA)-induced thrombocytopenia varied widely in previous studies, due to methodological differences. Our objective was to evaluate the relationship between trough VPA plasma levels and platelet counts and assess risk factors for the development of thrombocytopenia. Methods: Patients with refractory partial epilepsy were enrolled in this double-blind, multicenter, concentration,response trial that evaluated the efficacy and safety of high versus low trough plasma VPA concentrations following administration of divalproex sodium as monotherapy. Trough VPA concentrations and concomitant platelet counts were drawn at baseline and intermittently throughout the 24-week trial. Bivariate correlations and multivariate stepwise regression analysis were performed between platelet counts and multiple variables. A logistic regression analysis was done to determine the probability of developing thrombocytopenia at various VPA levels. Results: A total of 851 VPA levels and concomitant platelet counts were analyzed in 265 patients. Of these, 17.7% of patients experienced at least one episode of thrombocytopenia (platelet count , 100,000/,l) after exposure to divalproex sodium. A significant negative correlation was found between VPA levels and platelet counts. Women were significantly more likely to develop thrombocytopenia. The probability of developing thrombocytopenia substantially increased at trough VPA levels above 100 ,g/ml in women and above 130 ,g/ml in men. Discussion: Our data strongly support a causal relationship between rising plasma VPA levels and reduced platelet counts, with additional risk factors including female gender and lower baseline platelet counts. [source] Multivariate Neuropsychological Prediction of Seizure Lateralization in Temporal Epilepsy Surgical CasesEPILEPSIA, Issue 8 2007Therese A. Keary Summary:,Purpose: Neuropsychological assessment can be of assistance in determining seizure lateralization in cases where EEG and MRI findings do not provide clear lateralizing data. While several studies have examined the lateralizing value of individual neuropsychological measures, clinicians are still in need of a statistically sound method that permits the incorporation of multiple neuropsychological variables to predict seizure lateralization in the individual patient. Method: The present study investigated the lateralizing value of several commonly used neuropsychological measures in a large sample of patients (n = 217) who eventually underwent surgical resection to treat their epilepsy. Side of surgery was used to operationally define seizure lateralization. A comparison of the relative utility of a multivariate versus univariate approach to predict seizure lateralization was conducted in temporal epilepsy cases. Results: The results provide evidence for the incremental validity of neuropsychological measures, other than memory and IQ tests, in the prediction of seizure lateralization in patients with medically intractable epilepsy. These data indicate that a multivariate approach increases the accuracy of prediction of seizure lateralization for temporal lobe epilepsy cases. Conclusion: This study supports the use of a multivariate approach using neuropsychological measures to predict seizure lateralization in temporal epilepsy surgical candidates. Regression formulas are provided to enhance the clinical utility of these findings. [source] EVOLUTIONARY DYNAMICS OF A SEXUAL ORNAMENT IN THE HOUSE SPARROW (PASSER DOMESTICUS): THE ROLE OF INDIRECT SELECTION WITHIN AND BETWEEN SEXESEVOLUTION, Issue 6 2008Henrik Jensen The relative contribution of sexual and natural selection to evolution of sexual ornaments has rarely been quantified under natural conditions. In this study we used a long-term dataset of house sparrows in which parents and offspring were matched genetically to estimate the within- and across-sex genetic basis for variation and covariation among morphological traits. By applying two-sex multivariate "animal models" to estimate genetic parameters, we estimated evolutionary changes in a male sexual ornament, badge size, from the contribution of direct and indirect selection on correlated traits within males and females, after accounting for overlapping generations and age-structure. Indirect natural selection on genetically correlated traits in males and females was the major force causing evolutionary change in the male ornament. Thus, natural selection on female morphology may cause indirect evolutionary changes in male ornaments. We observed however no directional phenotypic change in the ornament size of one-year-old males during the study period. On the other hand, changes were recorded in other morphological characters of both sexes. Our analyses of evolutionary dynamics in sexual characters require application of appropriate two-sex models to account for how selection on correlated traits in both sexes affects the evolutionary outcome of sexual selection. [source] COMPARING STRENGTHS OF DIRECTIONAL SELECTION: HOW STRONG IS STRONG?EVOLUTION, Issue 10 2004Joe Hereford Abstract The fundamental equation in evolutionary quantitative genetics, the Lande equation, describes the response to directional selection as a product of the additive genetic variance and the selection gradient of trait value on relative fitness. Comparisons of both genetic variances and selection gradients across traits or populations require standardization, as both are scale dependent. The Lande equation can be standardized in two ways. Standardizing by the variance of the selected trait yields the response in units of standard deviation as the product of the heritability and the variance-standardized selection gradient. This standardization conflates selection and variation because the phenotypic variance is a function of the genetic variance. Alternatively, one can standardize the Lande equation using the trait mean, yielding the proportional response to selection as the product of the squared coefficient of additive genetic variance and the mean-standardized selection gradient. Mean-standardized selection gradients are particularly useful for summarizing the strength of selection because the mean-standardized gradient for fitness itself is one, a convenient benchmark for strong selection. We review published estimates of directional selection in natural populations using mean-standardized selection gradients. Only 38 published studies provided all the necessary information for calculation of mean-standardized gradients. The median absolute value of multivariate mean-standardized gradients shows that selection is on average 54% as strong as selection on fitness. Correcting for the upward bias introduced by taking absolute values lowers the median to 31%, still very strong selection. Such large estimates clearly cannot be representative of selection on all traits. Some possible sources of overestimation of the strength of selection include confounding environmental and genotypic effects on fitness, the use of fitness components as proxies for fitness, and biases in publication or choice of traits to study. [source] The use of periphytic diatoms as a means of assessing impacts of point source inorganic nutrient pollution in south-eastern AustraliaFRESHWATER BIOLOGY, Issue 5 2006JOCELYN DELA-CRUZ Summary 1. Periphytic diatoms are used as indicators of water quality because their ecological tolerances or preferences to environmental variables are thought to be predictable. However, much of the present autecological information for periphytic diatoms has been derived from studies conducted in the northern hemisphere. In this present study we used periphytic diatoms to determine the impacts of inorganic nutrient pollution in a tidal river system in the temperate latitudes of south-east Australia. In so doing, we assess the suitability of the use of the ,northern hemisphere' ecological tolerance/preference data for periphytic diatoms. 2. Artificial substrates were used to collect periphytic diatoms at 35 sites, which were positioned along the riverbanks and the middle of the river at various distances upstream and downstream of the sewage outfall. The sampling design took into account tidal excursions and the observed sewage plume dynamics. Periphytic diatoms were collected during the austral winter month of August and the austral spring months of September and October. We deployed the artificial substrates for 4 weeks to allow the periphytic diatoms to recruit and colonise, before identifying and enumerating the assemblages. 3. Data analysis included two approaches: multivariate visualisations of combinations of environmental and biological data to investigate shifts in species structure of the periphytic diatom assemblage and multimetric indices based on ecological tolerance/preference data. 4. We found that the spatial patterns inferred from multivariate and multimetric analyses were consistent. Temporal variation in the composition of the periphytic diatom assemblage was greater than the spatial variation along horizontal sections of the river (in any one deployment) due mainly to shifts between winter and spring species. 5. Outfall effects were most apparent in winter, possibly because subsequent deployments were swamped by growth of spring periphytic diatoms. The outfall effects included a shift towards pollutant tolerant species and a reduction in the variability of the periphytic diatom assemblage across the river. 6. We conclude that the use of periphytic diatoms and associated ecological tolerance/preference data as a means of assessing impacts of point source inorganic nutrient pollution is effective. An understanding of river and sewage flow patterns is essential to the design of appropriate monitoring programmes and to the interpretation of results, especially as periphytic diatoms are sensitive to many environmental variables. [source] Energetic trade-off between maintenance costs and flight capacity in the sand cricket (Gryllus firmus)FUNCTIONAL ECOLOGY, Issue 4 2008R. F. Nespolo Summary 1Energetic trade-offs are those compromises that appear when the energy budget of an individual's life history closely matches or exceeds the net available energy in the environment in a given moment. In these situations, two or more functions can compete and organisms face physiological decisions in order to survive and reproduce. 2In insects, one of the most costly investments is flight capacity, which increases dispersal capacity but is energetically expensive. Adult sand crickets (Gryllus firmus) can vary drastically in this capacity, being macropterous or micropterous depending on whether they exhibit flight-capable wings. However, this binary phenotype has a continuous subjacent determinant in the macropterous morph which is the mass of the muscles that power flight, the dorso-longitudinal muscles (DLM). 3Using respirometric measurements, we studied a potential trade-off between body parts, the mass of the DLM and energy metabolism (including both maximum and average metabolism). By recording the metabolic rate of c. 180 crickets and then dissecting and weighing their body parts, we took advantage of the correlational structure to infer associations between energetic and morphological variables. We found that the residual mass of the DLM shows a quadratic relationship with residual resting and average metabolism: at low DLM mass there is a negative relationship, which becomes positive at higher DLM mass. 4We suggest that this pattern of covariance is a consequence of the negative correlation between DLM mass and gonad mass, and the relative contribution of functional vs. non-functional DLM. Then, by using energetics and a combination of multivariate and correlational statistics we were able to show how two important life-history functions (i.e. Dispersal and fecundity) compete for the same resources in an insect species. [source] Factors Influencing Migraineur-Consulting Behavior in a University PopulationHEADACHE, Issue 5 2006Monica L. Skomo PharmD Objective.,The purpose of this study was to identify factors that contribute to treatment-seeking behavior in migraineurs in a large employer population. Specifically, the impact of psychographic variables, such as social support, attitudes toward medication, locus of control, and migraine-associated disability, are considered concomitantly with demographic and disease severity variables. Background.,Migraine remains an underconsulted condition. Previous explorations of demographic factors and headache characteristics have not adequately predicted migraineur physician-consulting behavior. Methods.,University employees and students experiencing headaches were interviewed by pharmacists to determine whether they suffer from migraine using the International Headache Society (IHS) criteria for migraine. Identified migraineurs were categorized into 3 groups: (1) never-consulter, (2) lapsed-consulter, and (3) current-consulter. Each group was asked to complete an instrument that assesses perceived social support (Headache Social Support Questionnaire), medication attitudes (Beliefs about Medicines Questionnaire), locus of control (Headache-Specific Locus of Control Scale), and migraine-associated disability (Migraine Disability Assessment Questionnaire). Univariate (ANOVA) and multivariate (logistic regression) approaches were used to identify factors associated with migraineur-consulting behavior. Results.,A total of 100 subjects participated in the study. Eighty-two participants met IHS criteria for migraine, of whom 22 were never-consulters, 20 were lapsed-consulters, and 40 were current-consulters. The consulter groups differed on scores acquired from the Social Support Active Involvement subscale (P= .04) and the Healthcare Professional Locus of Control subscale (P= .010). The logistic regression procedures confirmed the contributions of social support and healthcare locus of control in predicting migraineur-consulting behavior. Conclusion.,Results suggest that attitudes concerning the role of healthcare professionals and the presence of a supportive social network have greater influence on migraineur-consulting behavior than do patient demographic characteristics, beliefs about medications, and migraine frequency and severity. With an understanding of the link between psychosocial variables and consulting behavior, healthcare professionals may be able to positively impact migraineur physician consultation rates, drug therapy, and quality of life. [source] Time to Send the Preemie Home?HEALTH SERVICES RESEARCH, Issue 2p1 2009Additional Maturity at Discharge, Outcomes, Subsequent Health Care Costs Objective. To determine whether longer stays of premature infants allowing for increased physical maturity result in subsequent postdischarge cost savings that help counterbalance increased inpatient costs. Data Sources. One thousand four hundred and two premature infants born in the Northern California Kaiser Permanente Medical Care Program between 1998 and 2002. Study Design/Methods. Using multivariate matching with a time-dependent propensity score we matched 701 "Early" babies to 701 "Late" babies (developmentally similar at the time the earlier baby was sent home but who were discharged on average 3 days later) and assessed subsequent costs and clinical outcomes. Principal Findings. Late babies accrued inpatient costs after the Early baby was already home, yet costs after discharge through 6 months were virtually identical across groups, as were clinical outcomes. Overall, after the Early baby went home, the Late,Early cost difference was $5,016 (p<.0001). A sensitivity analysis suggests our conclusions would not easily be altered by failure to match on some unmeasured covariate. Conclusions. In a large integrated health care system, if a baby is ready for discharge (as defined by the typical criteria), staying longer increased inpatient costs but did not reduce postdischarge costs nor improve postdischarge clinical outcomes. [source] Cytoplasmic ,-catenin accumulation is a good prognostic marker in upper and lower gastrointestinal adenocarcinomasHISTOPATHOLOGY, Issue 1 2010Michael G A Norwood Norwood M G A, Bailey N, Nanji M, Gillies R S, Nicholson A, Ubhi S, Darnton J J, Steyn R S, Womack C, Hughes A, Hemingway D, Harrison R, Waters R & Jankowski J A (2010) Histopathology,57, 101,111 Cytoplasmic ,-catenin accumulation is a good prognostic marker in upper and lower gastrointestinal adenocarcinomas Aims:, ,-Catenin is an important molecule in cancer biology. Membranous ,-catenin enhances cellular differentiation and inhibits invasion by its action on E-cadherin. The aim was to ascertain whether the cellular expression of these molecules in colorectal and oesophageal cancer specimens is associated with survival in patients with gastrointestinal cancer. Methods and results:, Tumour samples from 149 patients undergoing resection for colorectal adenocarcinoma and 147 patients undergoing resection for oesophageal adenocarcinoma were retrospectively analysed using immunohistochemical techniques to assess ,-catenin expression. Increasing ,-catenin expression in the cytoplasm was associated with improved survival for colorectal cancer cases on both univariate (P = 0.003) and multivariate (P = 0.01) analysis. In addition, increased expression in the most recent cohort of oesophageal adenocarcinoma patients was associated with improved TNM staging (P = 0.007). Membrane expression was weakly associated with survival in colorectal cancer on univariate analysis (P = 0.09), but not on multivariate analysis (P = 0.21). Complete absence of ,-catenin expression at all three sites was associated with reduced 5-year survival in colorectal cancer. Conclusions:, This is one of the largest prognostic studies of ,-catenin in gastrointestinal adenocarcinoma. It shows that low levels of cytoplasmic ,-catenin expression are associated with reduced survival in patients with colorectal cancer as well as worse TNM staging in oesophageal adenocarcinoma (a recognized surrogate end-point for survival). We believe this is the first time that this has been reported. This finding should be tested prospectively in oncological trials to validate whether the presence of cytoplasmic ,-catenin could be used as a prognostic marker for less aggressive disease. [source] Outcome prediction and risk assessment by quantitative pyrosequencing methylation analysis of the SFN gene in advanced stage, high-risk, neuroblastic tumor patientsINTERNATIONAL JOURNAL OF CANCER, Issue 3 2010Barbara Banelli Abstract The aim of our study was to identify threshold levels of DNA methylation predictive of the outcome to better define the risk group of stage 4 neuroblastic tumor patients. Quantitative pyrosequencing analysis was applied to a training set of 50 stage 4, high risk patients and to a validation cohort of 72 consecutive patients. Stage 4 patients at lower risk and ganglioneuroma patients were included as control groups. Predictive thresholds of methylation were identified by ROC curve analysis. The prognostic end points of the study were the overall and progression-free survival at 60 months. Data were analyzed with the Cox proportional hazard model. In a multivariate model the methylation threshold identified for the SFN gene (14.3.3,) distinguished the patients presenting favorable outcome from those with progressing disease, independently from all known predictors (Training set: Overall Survival HR 8.53, p = 0.001; Validation set: HR 4.07, p = 0.008). The level of methylation in the tumors of high-risk patients surviving more than 60 months was comparable to that of tumors derived from lower risk patients and to that of benign ganglioneuroma. Methylation above the threshold level was associated with reduced SFN expression in comparison with samples below the threshold. Quantitative methylation is a promising tool to predict survival in neuroblastic tumor patients. Our results lead to the hypothesis that a subset of patients considered at high risk,but displaying low levels of methylation,could be assigned at a lower risk group. [source] Prospective study of body mass index, height, physical activity and incidence of bladder cancer in US men and womenINTERNATIONAL JOURNAL OF CANCER, Issue 1 2007Crystal N. Holick Abstract We evaluated prospectively the association between body mass index (BMI), height, recreational physical activity and the risk of bladder cancer among US adults. Data were used from 2 ongoing cohorts, the Health Professionals Follow-up Study and the Nurses' Health Study, with 3,542,012 years of follow-up and 866 incident bladder cancer cases (men = 507; women = 359) for the anthropometric analysis and 1,890,476 years of follow-up and 706 incident bladder cancer cases (men = 502; women = 204) for the physical activity analysis. Cox proportional hazard models were used to estimate incidence rate ratios (RR) and 95% confidence intervals (CI) between BMI, height, physical activity and bladder cancer risk adjusting for age, pack-years of cigarette smoking and current smoking. Estimates from each cohort were pooled using a random-effects model. We observed no association between baseline BMI and bladder cancer risk, even when we compared a BMI of ,30 kg/m2 to a BMI of 18,22.9 kg/m2 [pooled multivariate (MV) RR, 1.16; 95% CI: 0.89,1.52]. A weak, but statistically significant, association was observed for the same comparison after excluding bladder cancer cases diagnosed within the first 4 years of follow-up (pooled MV RR, 1.33; 95% CI: 1.01,1.76). Height was not related to bladder cancer risk (pooled MV RR, 0.82; 95% CI: 0.65,1.03, top vs. bottom quintile). Total recreational physical activity also was not associated with the risk of bladder cancer (pooled MV RR, 0.97; 95% CI: 0.77,1.24, top vs. bottom quintile). Our findings do not support a role for BMI, height or physical activity in bladder carcinogenesis. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||