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1.
J Expo Sci Environ Epidemiol ; 32(6): 900-907, 2022 11.
Article in English | MEDLINE | ID: mdl-35474345

ABSTRACT

BACKGROUND: Presenting a comprehensive picture of geographic data comprising multiple factors is an inherently integrative undertaking. Visualizing such data in an interactive form is essential for public sharing and geographic information systems (GIS) analysis. The Toxicological Prioritization Index (ToxPi) framework offers a visual analytic integrating data that is compatible with geographic data. ArcGIS is a predominant geospatial software available for presenting and communicating geographic data, yet to our knowledge there is no methodology for integrating ToxPi profiles into ArcGIS maps. OBJECTIVE: We introduce an actively developed suite of software, the ToxPi*GIS Toolkit, for creating, viewing, sharing, and analyzing interactive ToxPi profiles in ArcGIS to allow for new GIS analysis and an avenue for providing geospatial results to the public. METHODS: The ToxPi*GIS Toolkit is a collection of methods for creating interactive feature layers that contain ToxPi profiles. It currently includes an ArcGIS Toolbox (ToxPiToolbox.tbx) for drawing location-specific ToxPi profiles in a single feature layer, a collection of modular Python scripts that create predesigned layer files containing ToxPi feature layers from the command line, and a collection of Python routines for useful data manipulation and preprocessing. We present workflows documenting ToxPi feature layer creation, sharing, and embedding for both novice and advanced users looking for additional customizability. RESULTS: Map visualizations created with the ToxPi*GIS Toolkit can be made freely available on public URLs, allowing users without ArcGIS Pro access or expertise to view and interact with them. Novice users with ArcGIS Pro access can create de novo custom maps, and advanced users can exploit additional customization options. The ArcGIS Toolbox provides a simple means for generating ToxPi feature layers. We illustrate its usage with current COVID-19 data to compare drivers of pandemic vulnerability in counties across the United States. SIGNIFICANCE: The integration of ToxPi profiles with ArcGIS provides new avenues for geospatial analysis, visualization, and public sharing of multi-factor data. This allows for comparison of data across a region, which can support decisions that help address issues such as disease prevention, environmental health, natural disaster prevention, chemical risk, and many others. Development of new features, which will advance the interests of the scientific community in many fields, is ongoing for the ToxPi*GIS Toolkit, which can be accessed from www.toxpi.org .


Subject(s)
COVID-19 , Geographic Information Systems , Humans
2.
medRxiv ; 2021 Oct 12.
Article in English | MEDLINE | ID: mdl-34671776

ABSTRACT

BACKGROUND: Presenting a comprehensive picture of geographic data comprising multiple factors is an inherently integrative undertaking. Visualizing such data in an interactive form is essential for public sharing and geographic information systems (GIS) analysis. The Toxicological Prioritization Index (ToxPi) framework has been used as an integrative model layered atop geospatial data, and its deployment within the dynamic ArcGIS universe would open up powerful new avenues for sophisticated, interactive GIS analysis. OBJECTIVE: We propose an actively developed suite of software, the ToxPi*GIS Toolkit, for creating, viewing, sharing, and analyzing interactive ToxPi figures in ArcGIS. METHODS: The ToxPi*GIS Toolkit is a collection of methods for creating interactive feature layers that contain ToxPi diagrams. It currently includes an ArcGIS Toolbox ( ToxPiToolbox . tbx ) for drawing geographically located ToxPi diagrams onto a feature layer, a collection of modular Python scripts that create predesigned layer files containing ToxPi feature layers from the command line, and a collection of Python routines for useful data manipulation and preprocessing. We present workflows documenting ToxPi feature layer creation, sharing, and embedding for both novice and advanced users looking for additional customizability. RESULTS: Map visualizations created with the ToxPi*GIS Toolkit can be made freely available on public URLs, allowing users without ArcGIS Pro access or expertise to view and interact with them. Novice users with ArcGIS Pro access can create de novo custom maps, and advanced users can exploit additional customization options. The ArcGIS Toolbox provides a simple means for generating ToxPi feature layers. We illustrate its usage with current COVID-19 data to compare drivers of pandemic vulnerability in counties across the United States. SIGNIFICANCE: Development of new features, which will advance the interests of the scientific community in many fields, is ongoing for the ToxPi*GIS Toolkit, which can be accessed from www.toxpi.org . IMPACT STATEMENT: Presenting a comprehensive picture of geographic data comprising multiple factors is an inherently integrative undertaking. Visualizing this data in an interactive form is essential for public sharing and geographic analysis. The ToxPi framework provides such integration, and ArcGIS offers interactive geographic mapping capability, but, so far, producing ToxPi figures in ArcGIS maps has not been possible. We propose the ToxPi*ArcGIS Toolkit, which enables the generation of ArcGIS feature layers that include interactive ToxPi figures. Further, we document the living code repository created for this method and outline workflows for sharing, creating, and embedding maps within a web dashboard. AVAILABILITY AND IMPLEMENTATION: All applications, usage instructions, sample data, example visualizations, and open-source code are freely available from a dedicated GitHub page linked from www.toxpi.org . ArcGIS Pro can be obtained at https://www.esri.com/en-us/arcgis/products/arcgis-pro/overview .

4.
medRxiv ; 2020 Sep 13.
Article in English | MEDLINE | ID: mdl-32817964

ABSTRACT

BACKGROUND: While the COVID-19 pandemic presents a global challenge, the U.S. response places substantial responsibility for both decision-making and communication on local health authorities, necessitating tools to support decision-making at the community level. OBJECTIVES: We created a Pandemic Vulnerability Index (PVI) to support counties and municipalities by integrating baseline data on relevant community vulnerabilities with dynamic data on local infection rates and interventions. The PVI visually synthesizes county-level vulnerability indicators, enabling their comparison in regional, state, and nationwide contexts. METHODS: We describe the data streams used and how these are combined to calculate the PVI, detail the supporting epidemiological modeling and machine-learning forecasts, and outline the deployment of an interactive web Dashboard. Finally, we describe the practical application of the PVI for real-world decision-making. RESULTS: Considering an outlook horizon from 1 to 28 days, the overall PVI scores are significantly associated with key vulnerability-related outcome metrics of cumulative deaths, population adjusted cumulative deaths, and the proportion of deaths from cases. The modeling results indicate the most significant predictors of case counts are population size, proportion of black residents, and mean PM2.5. The machine learning forecast results were strongly predictive of observed cases and deaths up to 14 days ahead. The modeling reinforces an integrated concept of vulnerability that accounts for both dynamic and static data streams and highlights the drivers of inequities in COVID-19 cases and deaths. These results also indicate that local areas with a highly ranked PVI should take near-term action to mitigate vulnerability. DISCUSSION: The COVID-19 PVI Dashboard monitors multiple data streams to communicate county-level trends and vulnerabilities and facilitates decision-making and communication among government officials, scientists, community leaders, and the public to enable effective and coordinated action to combat the pandemic.

5.
Article in English | MEDLINE | ID: mdl-32053902

ABSTRACT

The Houston-Galveston-Brazoria (HGB) region faces numerous environmental and public health challenges from both natural disasters and industrial activity, but the historically disadvantaged communities most often impacted by such risks have limited ability to access and utilize big data for advocacy efforts. We developed HGBEnviroScreen to identify and prioritize regions of heightened vulnerability, in part to assist communities in understanding risk factors and developing environmental justice action plans. While similar in objectives to existing environmental justice tools, HGBEnviroScreen is unique in its ability to integrate and visualize national and local data to address regional concerns. For the 1090 census tracts in the HGB region, we accrued data into five domains: (i) social vulnerability, (ii) baseline health, (iii) environmental exposures and risks, (iv) environmental sources, and (v) flooding. We then integrated and visualized these data using the Toxicological Prioritization Index (ToxPi). We found that the highest vulnerability census tracts have multifactorial risk factors, with common drivers being flooding, social vulnerability, and proximity to environmental sources. Thus, HGBEnviroScreen is not only helping identify communities of greatest overall vulnerability but is also providing insights into which domains would most benefit from improved planning, policy, and action in order to reduce future vulnerability.


Subject(s)
Community Participation , Disasters , Environmental Exposure , Accidents, Occupational , Floods , Humans , Public Health , Risk Assessment , Risk Factors , Vulnerable Populations
6.
Arch Toxicol ; 94(2): 469-484, 2020 02.
Article in English | MEDLINE | ID: mdl-31822930

ABSTRACT

The US Environmental Protection Agency's ToxCast program has generated toxicity data for thousands of chemicals but does not adequately assess potential neurotoxicity. Networks of neurons grown on microelectrode arrays (MEAs) offer an efficient approach to screen compounds for neuroactivity and distinguish between compound effects on firing, bursting, and connectivity patterns. Previously, single concentrations of the ToxCast Phase II library were screened for effects on mean firing rate (MFR) in rat primary cortical networks. Here, we expand this approach by retesting 384 of those compounds (including 222 active in the previous screen) in concentration-response across 43 network activity parameters to evaluate neural network function. Using hierarchical clustering and machine learning methods on the full suite of chemical-parameter response data, we identified 15 network activity parameters crucial in characterizing activity of 237 compounds that were response actives ("hits"). Recognized neurotoxic compounds in this network function assay were often more potent compared to other ToxCast assays. Of these chemical-parameter responses, we identified three k-means clusters of chemical-parameter activity (i.e., multivariate MEA response patterns). Next, we evaluated the MEA clusters for enrichment of chemical features using a subset of ToxPrint chemotypes, revealing chemical structural features that distinguished the MEA clusters. Finally, we assessed distribution of neurotoxicants with known pharmacology within the clusters and found that compounds segregated differentially. Collectively, these results demonstrate that multivariate MEA activity patterns can efficiently screen for diverse chemical activities relevant to neurotoxicity, and that response patterns may have predictive value related to chemical structural features.


Subject(s)
Databases, Chemical , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical/methods , Neurotoxicity Syndromes/pathology , Toxicity Tests/methods , Animals , Cell Culture Techniques/instrumentation , Cell Culture Techniques/methods , Machine Learning , Microelectrodes , Nerve Net/drug effects , Neural Networks, Computer , Neurons/drug effects , Rats, Long-Evans
7.
Comput Toxicol ; 122019 Nov.
Article in English | MEDLINE | ID: mdl-31453412

ABSTRACT

Addressing the complex relationship between public health and environmental exposure requires multiple types and sources of data. An important source of chemical data derives from high-throughput screening (HTS) efforts, such as the Tox21/ToxCast program, which aim to identify chemical hazard using primarily in vitro assays to probe toxicity. While most of these assays target specific genes, assessing the disease-relevance of these assays remains challenging. Integration with additional data sets may help to resolve these questions by providing broader context for individual assay results. The Comparative Toxicogenomics Database (CTD), a publicly available database that builds networks of chemical, gene, and disease information from manually curated literature sources, offers a promising solution for contextual integration with HTS data. Here, we tested the value of integrating data across Tox21/ToxCast and CTD by linking elements common to both databases (i.e., assays, genes, and chemicals). Using polymarcine and Parkinson's disease as a case study, we found that their union significantly increased chemical-gene associations and disease-pathway coverage. Integration also enabled new disease associations to be made with HTS assays, expanding coverage of chemical-gene data associated with diseases. We demonstrate how integration enables development of predictive adverse outcome pathways using 4-nonylphenol, branched as an example. Thus, we demonstrate enhancements to each data source through database integration, including scenarios where HTS data can efficiently probe chemical space that may be understudied in the literature, as well as how CTD can add biological context to those results.

8.
Diabetes ; 67(7): 1428-1440, 2018 07.
Article in English | MEDLINE | ID: mdl-29650774

ABSTRACT

Metformin is the first-line treatment for type 2 diabetes (T2D). Although widely prescribed, the glucose-lowering mechanism for metformin is incompletely understood. Here, we used a genome-wide association approach in a diverse group of individuals with T2D from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) clinical trial to identify common and rare variants associated with HbA1c response to metformin treatment and followed up these findings in four replication cohorts. Common variants in PRPF31 and CPA6 were associated with worse and better metformin response, respectively (P < 5 × 10-6), and meta-analysis in independent cohorts displayed similar associations with metformin response (P = 1.2 × 10-8 and P = 0.005, respectively). Previous studies have shown that PRPF31(+/-) knockout mice have increased total body fat (P = 1.78 × 10-6) and increased fasted circulating glucose (P = 5.73 × 10-6). Furthermore, rare variants in STAT3 associated with worse metformin response (q <0.1). STAT3 is a ubiquitously expressed pleiotropic transcriptional activator that participates in the regulation of metabolism and feeding behavior. Here, we provide novel evidence for associations of common and rare variants in PRPF31, CPA6, and STAT3 with metformin response that may provide insight into mechanisms important for metformin efficacy in T2D.


Subject(s)
Carboxypeptidases A/genetics , Diabetes Mellitus, Type 2/drug therapy , Diabetes Mellitus, Type 2/genetics , Eye Proteins/genetics , Metformin/therapeutic use , Pharmacogenomic Variants , Cohort Studies , Double-Blind Method , Female , Genome-Wide Association Study , Humans , Male , Middle Aged , Polymorphism, Single Nucleotide , STAT3 Transcription Factor/genetics , Treatment Outcome
9.
BMC Bioinformatics ; 19(1): 80, 2018 03 05.
Article in English | MEDLINE | ID: mdl-29506467

ABSTRACT

BACKGROUND: Drawing integrated conclusions from diverse source data requires synthesis across multiple types of information. The ToxPi (Toxicological Prioritization Index) is an analytical framework that was developed to enable integration of multiple sources of evidence by transforming data into integrated, visual profiles. Methodological improvements have advanced ToxPi and expanded its applicability, necessitating a new, consolidated software platform to provide functionality, while preserving flexibility for future updates. RESULTS: We detail the implementation of a new graphical user interface for ToxPi (Toxicological Prioritization Index) that provides interactive visualization, analysis, reporting, and portability. The interface is deployed as a stand-alone, platform-independent Java application, with a modular design to accommodate inclusion of future analytics. The new ToxPi interface introduces several features, from flexible data import formats (including legacy formats that permit backward compatibility) to similarity-based clustering to options for high-resolution graphical output. CONCLUSIONS: We present the new ToxPi interface for dynamic exploration, visualization, and sharing of integrated data models. The ToxPi interface is freely-available as a single compressed download that includes the main Java executable, all libraries, example data files, and a complete user manual from http://toxpi.org .


Subject(s)
Information Dissemination , Models, Theoretical , Software , User-Computer Interface , Cluster Analysis , Information Storage and Retrieval
10.
Clin Pharmacol Ther ; 103(4): 712-721, 2018 04.
Article in English | MEDLINE | ID: mdl-28736931

ABSTRACT

Individuals with type 2 diabetes (T2D) and dyslipidemia are at an increased risk of cardiovascular disease. Fibrates are a class of drugs prescribed to treat dyslipidemia, but variation in response has been observed. To evaluate common and rare genetic variants that impact lipid responses to fenofibrate in statin-treated patients with T2D, we examined lipid changes in response to fenofibrate therapy using a genomewide association study (GWAS). Associations were followed-up using gene expression studies in mice. Common variants in SMAD3 and IPO11 were marginally associated with lipid changes in black subjects (P < 5 × 10-6 ). Rare variant and gene expression changes were assessed using a false discovery rate approach. AKR7A3 and HSD17B13 were associated with lipid changes in white subjects (q < 0.2). Mice fed fenofibrate displayed reductions in Hsd17b13 gene expression (q < 0.1). Associations of variants in SMAD3, IPO11, and HSD17B13, with gene expression changes in mice indicate that transforming growth factor-beta (TGF-ß) and NRF2 signaling pathways may influence fenofibrate effects on dyslipidemia in patients with T2D.


Subject(s)
Aldehyde Reductase/genetics , Diabetes Mellitus, Type 2 , Dyslipidemias , Fenofibrate , Lipid Metabolism , Smad3 Protein/genetics , beta Karyopherins/genetics , Animals , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/genetics , Diabetes Mellitus, Type 2/metabolism , Dyslipidemias/blood , Dyslipidemias/complications , Dyslipidemias/drug therapy , Dyslipidemias/genetics , Female , Fenofibrate/administration & dosage , Fenofibrate/pharmacokinetics , Gene Expression Profiling/methods , Genome-Wide Association Study , Humans , Hypolipidemic Agents/administration & dosage , Hypolipidemic Agents/pharmacokinetics , Lipid Metabolism/drug effects , Lipid Metabolism/genetics , Male , Mice , Middle Aged , Pharmacogenomic Testing/methods , Signal Transduction/drug effects
11.
Toxicol Appl Pharmacol ; 329: 148-157, 2017 08 15.
Article in English | MEDLINE | ID: mdl-28583304

ABSTRACT

Benzo[a]pyrene (B[a]P) is a well-known genotoxic polycylic aromatic compound whose toxicity is dependent on signaling via the aryl hydrocarbon receptor (AHR). It is unclear to what extent detrimental effects of B[a]P exposures might impact future generations and whether transgenerational effects might be AHR-dependent. This study examined the effects of developmental B[a]P exposure on 3 generations of zebrafish. Zebrafish embryos were exposed from 6 to 120h post fertilization (hpf) to 5 and 10µM B[a]P and raised in chemical-free water until adulthood (F0). Two generations were raised from F0 fish to evaluate transgenerational inheritance. Morphological, physiological and neurobehavioral parameters were measured at two life stages. Juveniles of the F0 and F2 exhibited hyper locomotor activity, decreased heartbeat and mitochondrial function. B[a]P exposure during development resulted in decreased global DNA methylation levels and generally reduced expression of DNA methyltransferases in wild type zebrafish, with the latter effect largely reversed in an AHR2-null background. Adults from the F0 B[a]P exposed lineage displayed social anxiety-like behavior. Adults in the F2 transgeneration manifested gender-specific increased body mass index (BMI), increased oxygen consumption and hyper-avoidance behavior. Exposure to benzo[a]pyrene during development resulted in transgenerational inheritance of neurobehavioral and physiological deficiencies. Indirect evidence suggested the potential for an AHR2-dependent epigenetic route.


Subject(s)
Behavior, Animal/drug effects , Benzo(a)pyrene/toxicity , Epigenesis, Genetic/drug effects , Inheritance Patterns/drug effects , Neurotoxicity Syndromes/genetics , Repressor Proteins/agonists , Water Pollutants, Chemical/toxicity , Zebrafish Proteins/agonists , Zebrafish/genetics , Animals , Animals, Genetically Modified , DNA Methylation/drug effects , DNA Modification Methylases/metabolism , Dose-Response Relationship, Drug , Genotype , Heart Rate/drug effects , Heredity , Learning/drug effects , Mitochondria/drug effects , Mitochondria/metabolism , Motor Activity/drug effects , Neurotoxicity Syndromes/metabolism , Neurotoxicity Syndromes/physiopathology , Phenotype , Repressor Proteins/deficiency , Repressor Proteins/genetics , Respiration/drug effects , Risk Assessment , Social Behavior , Time Factors , Zebrafish/growth & development , Zebrafish/metabolism , Zebrafish Proteins/deficiency , Zebrafish Proteins/genetics
12.
PeerJ ; 5: e3187, 2017.
Article in English | MEDLINE | ID: mdl-28480134

ABSTRACT

BACKGROUND: Individuals with type 2 diabetes are at an increased risk of cardiovascular disease. Alterations in circulating lipid levels, total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglycerides (TG) are heritable risk factors for cardiovascular disease. Here we conduct a genome-wide association study (GWAS) of common and rare variants to investigate associations with baseline lipid levels in 7,844 individuals with type 2 diabetes from the ACCORD clinical trial. METHODS: DNA extracted from stored blood samples from ACCORD participants were genotyped using the Affymetrix Axiom Biobank 1 Genotyping Array. After quality control and genotype imputation, association of common genetic variants (CV), defined as minor allele frequency (MAF) ≥ 3%, with baseline levels of TC, LDL, HDL, and TG was tested using a linear model. Rare variant (RV) associations (MAF < 3%) were conducted using a suite of methods that collapse multiple RV within individual genes. RESULTS: Many statistically significant CV (p < 1 × 10-8) replicate findings in large meta-analyses in non-diabetic subjects. RV analyses also confirmed findings in other studies, whereas significant RV associations with CNOT2, HPN-AS1, and SIRPD appear to be novel (q < 0.1). DISCUSSION: Here we present findings for the largest GWAS of lipid levels in people with type 2 diabetes to date. We identified 17 statistically significant (p < 1 × 10-8) associations of CV with lipid levels in 11 genes or chromosomal regions, all of which were previously identified in meta-analyses of mostly non-diabetic cohorts. We also identified 13 associations in 11 genes based on RV, several of which represent novel findings.

13.
BMC Genomics ; 17(1): 976, 2016 11 25.
Article in English | MEDLINE | ID: mdl-27887572

ABSTRACT

BACKGROUND: Children exposed to maternal smoking during pregnancy exhibit increased risk for many adverse health effects. Maternal smoking influences methylation in newborns at specific CpG sites (CpGs). Here, we extend evaluation of individual CpGs to gene-level and pathway-level analyses among 1062 participants in the Norwegian Mother and Child Cohort Study (MoBa) using the Illumina 450 K platform to measure methylation in newborn DNA and maternal smoking in pregnancy, assessed using the biomarker, plasma cotinine. We used novel implementations of bioinformatics tools to collapse epigenome-wide methylation data into gene- and pathway-level effects to test whether exposure to maternal smoking in utero differentially methylated CpGs in genes enriched in biologic pathways. Unlike most pathway analysis applications, our approach allows replication in an independent cohort. RESULTS: Data on 485,577 CpGs, mapping to a total of 20,199 genes, were used to create gene scores that were tested for association with maternal plasma cotinine levels using Sequence Kernel Association Test (SKAT), and 15 genes were found to be associated (q < 0.25). Six of these 15 genes (GFI1, MYO1G, CYP1A1, RUNX1, LCTL, and AHRR) contained individual CpGs that were differentially methylated with regards to cotinine levels (p < 1.06 × 10-7). Nine of the 15 genes (FCRLA, MIR641, SLC25A24, TRAK1, C1orf180, ITLN2, GLIS1, LRFN1, and MIR451) were associated with cotinine at the gene-level (q < 0.25) but had no genome-wide significant individual CpGs (p > 1.06 × 10-7). Pathway analyses using gene scores resulted in 51 significantly associated pathways, which we tested for replication in an independent cohort (q < 0.05). Of those 32 replicated in an independent cohort, which clustered into six groups. The largest cluster consisted of pathways related to cancer, cell cycle, ERα receptor signaling, and angiogenesis. The second cluster, organized into five smaller pathway groups, related to immune system function, such as T-cell regulation and other white blood cell related pathways. CONCLUSIONS: Here we use novel implementations of bioinformatics tools to determine biological pathways impacted through epigenetic changes in utero by maternal smoking in 1062 participants in the MoBa, and successfully replicate these findings in an independent cohort. The results provide new insight into biological mechanisms that may contribute to adverse health effects from exposure to tobacco smoke in utero.


Subject(s)
Epigenesis, Genetic , Gene Expression Regulation , Maternal Exposure , Prenatal Exposure Delayed Effects , Signal Transduction , Smoking/adverse effects , Cluster Analysis , CpG Islands , DNA Methylation , Female , Humans , Pregnancy
14.
Front Genet ; 7: 138, 2016.
Article in English | MEDLINE | ID: mdl-27775101

ABSTRACT

Given the high costs of conducting a drug-response trial, researchers are now aiming to use retrospective analyses to conduct genome-wide association studies (GWAS) to identify underlying genetic contributions to drug-response variation. To prevent confounding results from a GWAS to investigate drug response, it is necessary to account for concomitant medications, defined as any medication taken concurrently with the primary medication being investigated. We use data from the Action to Control Cardiovascular Disease (ACCORD) trial in order to implement a novel scoring procedure for incorporating concomitant medication information into a linear regression model in preparation for GWAS. In order to accomplish this, two primary medications were selected: thiazolidinediones and metformin because of the wide-spread use of these medications and large sample sizes available within the ACCORD trial. A third medication, fenofibrate, along with a known confounding medication, statin, were chosen as a proof-of-principle for the scoring procedure. Previous studies have identified SNP rs7412 as being associated with statin response. Here we hypothesize that including the score for statin as a covariate in the GWAS model will correct for confounding of statin and yield a change in association at rs7412. The response of the confounded signal was successfully diminished from p = 3.19 × 10-7 to p = 1.76 × 10-5, by accounting for statin using the scoring procedure presented here. This approach provides the ability for researchers to account for concomitant medications in complex trial designs where monotherapy treatment regimens are not available.

15.
BMC Syst Biol ; 6: 21, 2012 Mar 21.
Article in English | MEDLINE | ID: mdl-22436240

ABSTRACT

BACKGROUND: Experimental design approaches for biological systems are needed to help conserve the limited resources that are allocated for performing experiments. The assumptions used when assigning probability density functions to characterize uncertainty in biological systems are unwarranted when only a small number of measurements can be obtained. In these situations, the uncertainty in biological systems is more appropriately characterized in a bounded-error context. Additionally, effort must be made to improve the connection between modelers and experimentalists by relating design metrics to biologically relevant information. Bounded-error experimental design approaches that can assess the impact of additional measurements on model uncertainty are needed to identify the most appropriate balance between the collection of data and the availability of resources. RESULTS: In this work we develop a bounded-error experimental design framework for nonlinear continuous-time systems when few data measurements are available. This approach leverages many of the recent advances in bounded-error parameter and state estimation methods that use interval analysis to generate parameter sets and state bounds consistent with uncertain data measurements. We devise a novel approach using set-based uncertainty propagation to estimate measurement ranges at candidate time points. We then use these estimated measurements at the candidate time points to evaluate which candidate measurements furthest reduce model uncertainty. A method for quickly combining multiple candidate time points is presented and allows for determining the effect of adding multiple measurements. Biologically relevant metrics are developed and used to predict when new data measurements should be acquired, which system components should be measured and how many additional measurements should be obtained. CONCLUSIONS: The practicability of our approach is illustrated with a case study. This study shows that our approach is able to 1) identify candidate measurement time points that maximize information corresponding to biologically relevant metrics and 2) determine the number at which additional measurements begin to provide insignificant information. This framework can be used to balance the availability of resources with the addition of one or more measurement time points to improve the predictability of resulting models.


Subject(s)
Models, Biological , Research Design , Uncertainty
16.
Ann Biomed Eng ; 37(5): 955-65, 2009 May.
Article in English | MEDLINE | ID: mdl-19229619

ABSTRACT

We investigated the effects of two types of cyclic tensile strain, continuous and rest inserted, on osteogenic differentiation of human adipose-derived adult stem cells (hASCs). The influence of these mechanical strains was tested on two hASC lines having different mineral deposition potential, with one cell line depositing approximately nine times as much calcium as the other hASC line after 14 days of culture in osteogenic medium on tissue culture plastic. Results showed that both continuous (10% strain, 1 Hz) and rest inserted cyclic tensile strain (10% strain, 1 Hz, 10 s rest after each cycle) regimens increased the amount and rate of calcium deposition for both high and low calcium depositing hASC lines as compared to unstrained controls. The response was similar for both types of tensile strain for a given cell line, however, cyclic tensile strain had a much stronger osteogenic effect on the high calcium depositing hASC line, suggesting that mechanical loading has a greater effect on cell lines that already have an innate ability to produce bone as compared to cell lines that do not. This is the first study to investigate the osteodifferentiation effects of cyclic tensile strain on hASCs and the first to show that both continuous (10%, 1 Hz) and rest inserted (10%, 1 Hz, 10 s rest) cyclic tensile strain accelerate hASC osteodifferentiation and increase calcium accretion.


Subject(s)
Models, Biological , Osteogenesis/physiology , Adipose Tissue/cytology , Adult Stem Cells , Calcium/metabolism , Cell Differentiation , Cell Proliferation , Cells, Cultured , Humans , Mesenchymal Stem Cells , Stress, Mechanical , Tensile Strength , Tissue Engineering/methods
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