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PubMed1984

The modes of binding methyl-alpha (and beta)-D-glucopyranosides and some of their derivatives to concanavalin A--a theoretical approach.

The probable modes of binding of Methyl--alpha (and beta)-D-glucopyranosides and some of their derivatives to concanavalin A have been proposed from theoretical studies. Theory predicts that beta-MeGlcP can bind to ConA in three different modes whereas alpha-MeGlcP can bind only in one mode. beta-MeGlcP in its most favourable mode of binding differs from alpha-MeGlcP in its alignment in the active-site of the lectin where it binds in a flipped or inverted orientation. Methyl substitution at the C-2 atom of the alpha-MeGlcP does not significantly affect the possible orientations of the sugar in the active-site of the lectin. Methyl substitution at C-3 or C-4, however, affects the allowed orientations drastically leading to the poor inhibiting power of Methyl-3-O-methyl-alpha-D-glucopyranoside and the inactivity of Methyl-4-O-methyl-alpha-D-glycopyranoside. These studies suggest that the increased activity of the alpha-MeGlcP over beta-MeGlcP may be due to the possibility of formation of better hydrogen bonds and to hydrophobic interactions rather than to steric factors as suggested by earlier workers. These models explain the available NMR and other binding studies.

Binding Sites↗

PubMed2026

Two Genomes, one Outcome: Stratifying Donor and Recipient Polygenic Risk Score to Improve Kidney Allograft Longevity.

Kidney transplantation outcomes arise from complex interactions among donor organ quality, recipient susceptibility, and immunologic compatibility, yet conventional clinical risk models explain only a modest fraction of outcome variability. Polygenic risk scores (PRS) offer a promising framework to enhance transplant risk assessment by integrating genome-wide genetic information from both donor and recipient into biologically informed models. This narrative review examines the mechanistic basis for PRS application in kidney transplantation and variant clustering approaches that link polygenic signals to specific biological pathways underlying alloimmunity, fibrosis, and metabolic dysfunction. We compare current PRS construction methodologies, highlighting their respective strengths and limitations in transplant cohorts. Transplant PRS are distinguished from single-genome disease models by their capacity to capture dual-genome interactions, simultaneously quantifying inherited donor organ liability and recipient genetic susceptibility within an integrated framework. This dual-genome architecture requires novel risk stratification paradigms in which combined donor-recipient polygenic profiles inform pretransplant decision-making in ways that neither genome alone can achieve. However, current PRS contribute only incremental variance beyond established clinical predictors, and critical limitations persist, including European ancestry bias, small cohort sizes, incomplete replication, and undefined clinical actionability thresholds. We critically evaluate these implementation barriers and outline future directions for integrating dual-genome PRS with clinical, molecular, and environmental data. The longer-term goal is to advance precision kidney transplantation through applications such as donor selection, immunosuppression tailoring, and individualized posttransplant surveillance. Realizing this potential will require validation in adequately powered, ancestry diverse, prospective transplant cohorts.

Journal Article↗

PubMed2007

Age estimation by pulp/tooth ratio in canines by peri-apical X-rays.

Estimation of age in individuals has received considerable attention in forensic science, in which it is a widely used method for individual identification, together with paleo-demographic analyses to establish mortality patterns in past populations. The present investigation, which is a continuation of a previously published pilot study, was conducted to examine the possible application of the pulp/tooth area ratio by peri-apical images as an indicator of age at death. A total of 200 peri-apical X-rays of upper and lower canines were assembled from 57 male and 43 female skeletons of Caucasian origin, aged between 20 and 79 years. They belong to the Frassetto osteological collection of Sassari (Sardinia) and are housed in the Museum of Anthropology, Department of Experimental and Evolutionistic Biology, University of Bologna. For each skeleton, dental maturity was evaluated by measuring the pulp/tooth area ratio on upper (x(1)) and lower (x(2)) canines. Very good agreement was found between intraobserver measurements. Statistical analysis was performed in order to obtain multiple regression formulae for dental age calculation, with chronological age as dependent variable, and gender, and upper and lower canines as independent variables. Stepwise regression analysis showed that gender did not contribute significantly to the fit (p=0.881) whereas variables x(1) and x(2) and the first-order interaction between them did. These two variables explained 92.5% of variations in estimated chronological age and the residual standard error was 4.06 years. Lastly, two simple linear regression equations were obtained for age estimation using canines from the maxilla and mandible separately. Both models explained 86% of variations in estimated chronological age and allowed an age-at-death estimate with a residual standard error of about 5.4 years.

Adult↗

PubMed2001

Models of respiratory rhythm generation in the pre-Bötzinger complex. III. Experimental tests of model predictions.

We used the testable predictions of mathematical models proposed by Butera et al. to evaluate cellular, synaptic, and population-level components of the hypothesis that respiratory rhythm in mammals is generated in vitro in the pre-Bötzinger complex (pre-BötC) by a heterogeneous population of pacemaker neurons coupled by fast excitatory synapses. We prepared thin brain stem slices from neonatal rats that capture the pre-BötC and maintain inspiratory-related motor activity in vitro. We recorded pacemaker neurons extracellularly and found: intrinsic bursting behavior that did not depend on Ca(2+) currents and persisted after blocking synaptic transmission; multistate behavior with transitions from quiescence to bursting and tonic spiking states as cellular excitability was increased via extracellular K(+) concentration ([K(+)](o)); a monotonic increase in burst frequency and decrease in burst duration with increasing [K(+)](o); heterogeneity among different cells sampled; and an increase in inspiratory burst duration and decrease in burst frequency by excitatory synaptic coupling in the respiratory network. These data affirm the basis for the network model, which is composed of heterogeneous pacemaker cells having a voltage-dependent burst-generating mechanism dominated by persistent Na(+) current (I(NaP)) and excitatory synaptic coupling that synchronizes cell activity. We investigated population-level activity in the pre-BötC using local "macropatch" recordings and confirmed these model predictions: pre-BötC activity preceded respiratory-related motor output by 100-400 ms, consistent with a heterogeneous pacemaker-cell population generating inspiratory rhythm in the pre-BötC; pre-BötC population burst amplitude decreased monotonically with increasing [K(+)](o) (while frequency increased), which can be attributed to pacemaker cell properties; and burst amplitude fluctuated from cycle to cycle after decreasing bilateral synaptic coupling surgically as predicted from stability analyses of the model. We conclude that the pacemaker cell and network models explain features of inspiratory rhythm generation in vitro.

Animals↗

PubMed2004

Localizing P300 generators in visual target and distractor processing: a combined event-related potential and functional magnetic resonance imaging study.

Constraints from functional magnetic resonance imaging (fMRI) were used to identify the sources of the visual P300 event-related potential (ERP). Healthy subjects performed a visual three-stimulus oddball paradigm with a difficult discrimination task while fMRI and high-density ERP data were acquired in separate sessions. This paradigm allowed us to differentiate the P3b component of the P300, which has been implicated in the detection of rare events in general (target and distractor), from the P3a component, which is mainly evoked by distractor events. The fMRI-constrained source model explained >99% of the variance of the scalp ERP for both components. The P3b was mainly produced by parietal and inferior temporal areas, whereas frontal areas and the insula contributed mainly to the P3a. This source model reveals that both higher visual and supramodal association areas contribute to the visual P3b and that the P3a has a strong frontal contribution, which is compatible with its more anterior distribution on the scalp. The results point to the involvement of distinct attentional subsystems in target and distractor processing.

Adult↗

PubMed1991

Academic achievement among undergraduate nursing students: the development and test of a causal model.

This article tested relationships among variables depicted in a causal learning model of academic achievement developed by the authors. The Learning and Study Skills (LASSI), Life Experience Survey (LES), and ASSET test were administered to 134 first-semester nursing students at a 2-year community college. The path analysis supported 11 of the 14 pathways tested. Language ability, reading ability, and self-efficacy were found to be direct effects on academic achievement. When self-efficacy was the criterion, students' language ability, math ability, motivation, and concentration and preparation for class were direct effects. Life stress, motivation, and self-monitoring/use of study strategies were found to be direct effects on students' concentration and preparation for class. In turn, when the ability to self-monitor and use study strategies was the criterion, motivation was the only direct effect. Overall, the model explained 46% of the variance in academic achievement.

Adult↗

PubMedDate not supplied

Explaining breast self-examination practice.

Research efforts to discover why women do or do not perform breast self-examination (BSE) have produced contradictory findings with poor explanatory power. In this study, ethnoscience was used to elicit the perceptions of women who perform BSE and of those who do not. The components of the emerging taxonomies are broader than those currently thought to be associated with this practice. A new model (BSE frequency model) explaining compliance with BSE was developed.

Adult↗

PubMed2004

Estimated risk for altered fetal growth resulting from exposure to fine particles during pregnancy: an epidemiologic prospective cohort study in Poland.

The purpose of this study was to estimate exposure of pregnant women in Poland to fine particulate matter [less than or equal to 2.5 microm in diameter (PM 2.5)] and to assess its effect on the birth outcomes. The cohort consisted of 362 pregnant women who gave birth between 34 and 43 weeks of gestation. The enrollment included only nonsmoking women with singleton pregnancies, 18-35 years of age, who were free from chronic diseases such as diabetes and hypertension. PM 2.5 was measured by personal air monitoring over 48 hr during the second trimester of pregnancy. All assessed birth effects were adjusted in multiple linear regression models for potential confounding factors such as the size of mother (maternal height, prepregnancy weight), parity, sex of child, gestational age, season of birth, and self-reported environmental tobacco smoke (ETS). The regression model explained 35% of the variability in birth weight (beta = -200.8, p = 0.03), and both regression coefficients for PM 2.5 and birth length (beta = -1.44, p = 0.01) and head circumference (HC; beta = -0.73, p = 0.02) were significant as well. In all regression models, the effect of ETS was insignificant. Predicted reduction in birth weight at an increase of exposure from 10 to 50 microg/m3 was 140.3 g. The corresponding predicted reduction of birth length would be 1.0 cm, and of HC, 0.5 cm. The study provides new and convincing epidemiologic evidence that high personal exposure to fine particles is associated with adverse effects on the developing fetus. These results indicate the need to reduce ambient fine particulate concentrations. However, further research should establish possible biologic mechanisms explaining the observed relationship.

Adolescent↗

PubMed1995

Health and its determining factors in the Tokyo megacity.

This study was designed to (i) analyze community health in post-industrial, densely populated Tokyo, and (ii) find a statistical-based prediction model for the health level of the communities from the environment. For this purpose, we compiled health-level indicators for each city-ward, and indicators for demography, infrastructure, land-use, amenities, education, working conditions, economics, and medical and welfare services. The health factors and the environmental factors were obtained by using weighted principal factor analysis; their relation was examined by weighted correlation analysis and weighted linear regression analysis. One to six environmental factors correlating significantly to health were found for each health-level indicator or factor. The prediction model explained up to 0.98 of the variance of the health-level factors and indicators. This analysis elicited health-determinant factors in various fields. The community health level was well reproduced by the present method; the model will be conducive to decision making pertaining to health policies.

Aged↗

PubMed2005

Health-related quality of life measured by the SF12 in working populations: associations with psychosocial work characteristics.

This study investigated the contribution of psychosocial work characteristics (decision latitude, job demand, social support at work, and effort-reward imbalance) to health-related quality of life. Data were derived from 2 aircraft manufacturing plants (N=1,855) at the start of a longitudinal study. Regression analysis showed that work characteristics (1st model) explained 19% of the variance in the mental summary score of the Short Form-12 Health Survey. R2 change for work characteristics decreased to 13%, accounting for demographics, socioeconomic status, body mass index, and medical condition (5th model). Including health behavior and personality factors (full model), R2 change for work characteristics remained significant. Psychosocial work characteristics account for relevant proportions in the subjective perception of mental health beyond a wide array of medical variables and personality factors.

Adult↗

PubMedDate not supplied

Alcohol outlet density and violence: a geospatial analysis.

AIMS: To examine the relationship between alcohol outlet density and violent crime controlling for neighbourhood sociostructural characteristics and the effects of spatially autocorrelated error. DESIGN: The sample for this ecologic study comprised 188 census tracts from the City of Austin, Texas and 263 tracts from the City of San Antonio, Texas. Data pertaining to neighbourhood social structure, alcohol density and violent crime were collected from archival sources, and analysed using bivariate, multivariate and geospatial analyses. RESULTS: Using ordinary least squares analysis, the neighbourhood sociostructural covariates explained close to 59% of the variability in violent crime rates in Austin and close to 39% in San Antonio. Adding alcohol outlet density in the target and adjacent census tracts improved the explanatory power of both models. Alcohol outlet density in the target census tract remained a significant predictor of violent crime rates in both cities when the effects of autocorrelated error were controlled for. In Austin, the effects of alcohol outlet density in the adjacent census tracts also remained significant. The final model explains 71% of the variance in violent crime in Austin and 56% in San Antonio. CONCLUSIONS: The findings show a clear association between alcohol outlet density and violence, and suggest that the issues of alcohol availability and access are fundamental to the prevention of alcohol-related problems within communities.

Adolescent↗

PubMed2006

Modelling environmental variation in Young's modulus for Pinus radiata and implications for determination of critical buckling height.

BACKGROUND AND AIMS: Although density-specific stiffness, E/rho, (where E is Young's modulus and rho is wood density) is often assumed constant by the elastic similarity model, and in determination of critical buckling height (H(crit)), few studies have tested this assumption within species. Here this assumption is tested for Pinus radiata growing across an environmental gradient, and theory is combined with data to develop a model of Young's modulus. METHODS: Analyses use an extensive series of environmental plots covering the range of climatic and edaphic conditions over which P. radiata is grown in New Zealand. Reduced major axis regression was used to determine scaling exponents between log-log plots of H(crit) vs. groundline diameter (D), and E/rho vs. D. Path analysis was used to identify significant direct and indirect (through stem slenderness) edaphic and climatic influences on E. KEY RESULTS: Density-specific stiffness exhibited 3-fold variation. As E/rho scaled positively with D, the exponent of 0.95 between H(crit) and D exceeded the assumed value of 0.67 under constant E/rho. The final path analysis model included mean air temperature in early autumn (T(aut)) and slenderness as significant (P < 0.05) positive direct influences on E. Tree leaf area index and T(aut) were indirectly associated with E through their significant (P < 0.05) positive direct relationship with stem slenderness. Young's modulus was most sensitive to T(aut), followed by stem slenderness then leaf area index, and the final model explained 76 % of the variance in E. CONCLUSIONS: The findings suggest that within species E/rho variation may influence H(crit) and the scaling exponent between D and H(crit) so important in assumptions regarding allometric relationships. The model presented may provide a useful means of determining variation in E, E/rho and H(crit) across environmental gradients.

Ecosystem↗

PubMed2006

Poor response inhibition as a predictor of problem drinking and illicit drug use in adolescents at risk for alcoholism and other substance use disorders.

OBJECTIVE: To evaluate the predictive power of executive functions, in particular, response inhibition, in relation to alcohol-related problems and illicit drug use in adolescence. METHOD: A total of 498 children from 275 families from a longitudinal high-risk study completed executive function measures in early and late adolescence and lifetime drinking and drug-related ratings at multiple time points including late adolescence (ages 15-17). Multi-informant measures of attention-deficit/hyperactivity disorder and conduct disorder were obtained in early childhood (ages 3-5), middle childhood, and adolescence. RESULTS: In multilevel models, poor response inhibition predicted aggregate alcohol-related problems, the number of illicit drugs used, and comorbid alcohol and drug use (but not the number of drug-related problems), independently of IQ, parental alcoholism and antisocial personality disorder, child attention-deficit/hyperactivity disorder and conduct symptoms, or age. Multivariate models explained 8% to 20% of residual variance in outcome scores. The incremental predictive power of response inhibition was modest, explaining about 1% of the variance in most outcomes, but more than 9% of the residual variance in problem outcomes within the highest risk families. Other measured executive functions did not independently predict substance use onset. CONCLUSION: Models of alcoholism and other drug risks that invoke executive functions may benefit from specifying response inhibition as an incremental component.

Adolescent↗

PubMed2000

Do patients matter? Contribution of patient and care provider characteristics to the adherence of general practitioners and midwives to the Dutch national guidelines on imminent miscarriage.

OBJECTIVE: To assess the relative contribution of patient and care provider characteristics to the adherence of general practitioners (GPs) and midwives to two specific recommendations in the Dutch national guidelines on imminent miscarriage. The study focused on performing physical examinations at the first contact and making a follow up appointment after 10 days because these are essential recommendations and there was much variation in adherence between different groups of providers. DESIGN: Prospective recording by GPs and midwives of care provided for patients with symptoms of imminent miscarriage. SETTING: General practices and midwifery practices in the Netherlands. SUBJECTS: 73 GPs and 38 midwives who agreed to adhere to the guidelines; 391 patients were recorded during a period of 12 months. MAIN MEASURES: Adherence to physical examinations and making a follow up appointment were measured as part of a larger prospective recording study on adherence to the guidelines on imminent miscarriage. Patient and care provider characteristics were obtained from case recordings and interviews, respectively. Multilevel analysis was performed to assess the contribution of several care provider and patient characteristics to adherence to two selected recommendations: the number of recommended physical examinations at the first contact and the number of days before a follow up appointment took place. RESULTS: In the multilevel model explaining variance in adherence to physical examinations, the care provider's acceptance of the recommendations was the most important factor. Severity of symptoms and referral to an obstetrician were significant factors at the patient level. In the model for follow up appointments the characteristics of the care provider were less important. Referral to an obstetrician and probability diagnosis were significant factors at the patient level. CONCLUSIONS: The study showed that characteristics of both the patient and care provider contribute to the variability in adherence. Furthermore, the contribution of the characteristics differed per recommendation. It is therefore advised that the contribution of both patient and care provider characteristics per recommendation should be carefully examined. If implementation is to be successful, strategies should be developed to address these specific contributions.

Abortion, Spontaneous↗

PubMed2004

Estimates of diffuse phosphorus sources in surface waters of the United States using a spatially referenced watershed model.

The statistical watershed model SPARROW (SPAtially Referenced Regression On Watershed attributes) was used to estimate the sources and transport of total phosphorus (TP) in surface waters of the United States. We calibrated the model using stream measurements of TP from 336 watersheds of mixed land use and spatial data on topography, soils, stream hydrography, and land use (agriculture, forest, shrub/grass, urban). The model explained 87% of the spatial variability in log transformed stream TP flux (kg yr(-1)). Predictions of stream yield (kg ha(-1) yr(-1)) were typically within 45% of the observed values at the monitoring sites. The model identified appreciable effects of soils, streams, and reservoirs on TP transport. The estimated aquatic rates of phosphorus removal declined with increasing stream size and rates of water flushing in reservoirs (i.e. areal hydraulic loads). A phosphorus budget for the 2.9 million km2 Mississippi River Basin provides a detailed accounting of TP delivery to streams, the removal of TP in surface waters, and the stream export of TP from major interior watersheds for sources associated with each land-use type.

Agriculture↗

PubMed1994

Deletion and duplication sequences induced in CHO cells by teniposide (VM-26), a topoisomerase II targeting drug, can be explained by the processing of DNA nicks produced by the drug-topoisomerase interaction.

Frameshift mutations induced by acridines in bacteriophage T4 have been shown to be due to the ability of these mutagens to cause DNA cleavage by the type II topoisomerase of T4 and the subsequent processing of the 3' ends at DNA nicks by DNA polymerase or its associated 3' exonuclease followed by ligation of the processed end to the original 5' end. An analysis of the ability of nick-processing models is presented here to test the ability of nick processing to account for the DNA sequences of duplications and deletions induced in the aprt gene of CHO cells by teniposide (VM-26) [Han et al. (1993) J. Mol. Biol., 229, 52]. Although teniposide is not an acridine, it induces topoisomerase II-mediated DNA cutting in aprt sequences in vitro and mutagenesis in vivo. Although the previous study noted a correlation between mutation sites and nearby DNA discontinuities induced by the enzyme in vitro, neither the nick-processing model responsible for T4 mutations, nor double-strand break models alone were able to account for most of the mutant sequences. Thus, no single model explained the correlation between teniposide-induced DNA cleavage and mutagenic specificity. This report describes an expanded analysis of the ways that nick-processing models might be related to mutagenesis and demonstrates that a modified nick-processing model provides a biochemical rationale for the mutant specificities. The successful nick-processing model proposes that either 3' ends at nicks are elongated by DNA polymerase and/or that 5' ends of nicks are subject to nuclease activity; 3'-nuclease activity is not implicated. The mutagenesis model for nick-processing of teniposide-induced nicks in CHO cells when compared to the mechanism of nick-processing in bacteriophage T4 at acridine-induced nicks provides a framework for considering whether the differences may be due to cell-specific modes of DNA processing and/or due to the precise characteristics of topoisomerase-DNA intermediates created by teniposide or acridine that lead to mutagenesis.

Acridines↗

PubMed1987

Mass transport in dissolution kinetics. I: Convective diffusion to assess the role of fluid viscosity under forced flow conditions.

The quantitative influence of viscosity on dissolution kinetics is assessed under laminar flow conditions by utilizing a convective diffusion model for drug dissolution. Functional dependency of three types of viscosity inducing agents is established with respect to the parameters of fluid flow rate, diffusivity, and solubility. Studies of aqueous solutions of sucrose and of glycerol demonstrate that the decrease in dissolution rate of ethyl p-aminobenzoate is related to the decrease in solute diffusivity in these solutions, whereas the solubility change in the glycerol solutions has an additional independent simultaneous effect. Dissolution in hydroxypropyl cellulose solutions remains constant under fixed fluid flow conditions because of the negligible effect of the polymer upon the drug diffusivity. A change in fluid flow rate, however, alters the dissolution rate and correlates quantitatively with the rate of shear in the convective diffusion model. The interpretation of the effect of viscosity on dissolution kinetics with the convective diffusion model explains these phenomena quantitatively in terms of the fundamental mass transport processes.

Cellulose↗

PubMed1991

Associations with social networks, social support, health status and psychiatric morbidity in three samples of elderly people.

The effects of social network structure, support and physical health status on psychiatric morbidity were investigated among 1415 people over retirement age who took part in three independent but comparable surveys in London (urban area) and Essex (semi rural area). Multivariate analysis showed that the model explained between 14.3% and 28.6% of the variation in psychiatric morbidity in the three samples. Poor health status was a more powerful predictor of psychiatric morbidity than the social network variables. Age and sex contributed little to the model. The model was strongest among the two samples of Hackney respondents.

Activities of Daily Living↗