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Search Results: 1 - 10 of 321074 matches for " Lisa J Martin "
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Aorta Measurements are Heritable and Influenced by Bicuspid Aortic Valve
Lisa J. Martin
Frontiers in Genetics , 2011, DOI: 10.3389/fgene.2011.00061
Abstract: Objectives: To determine whether the contributions of genetics and bicuspid aortic valve (BAV) independently influence aortic (Ao) dimensions. Background: Ao dilation is a risk factor for aneurysm, dissection, and sudden cardiac death. Frequent association of BAV with Ao dilation implicates a common underlying defect possibly due to genetic factors. Methods: Families enriched for BAV underwent standardized transthoracic echocardiography. In addition to BAV status, echocardiographic measures of Ao (annulus to descending Ao), pulmonary artery, and mitral valve annulus (MVA) diameters were obtained. Using variance components analysis, heritability was estimated with and without BAV status. Additionally, bivariate genetic analyses between Ao dimensions and BAV were performed. Results: Our cohort was obtained from 209 families enriched for BAV. After adjusting for age, body surface area, and sex, individuals with BAV had a statistically significant increase in all echocardiographic measurements (p < 0.006) except descending Ao and MVA. Individuals with BAV were at greater odds of having Ao dilation (OR = 4.44, 95% CI 2.93–6.72) than family members without BAV. All echocardiographic measurements exhibited moderate to strong heritability (0.25–0.53), and these estimates were not influenced by inclusion of BAV as a covariate. Bivariate genetic analyses supported that the genetic correlation between BAV and echo measures were not significantly different from zero. Conclusion: We show for the first time that echocardiographic measurements of Ao, pulmonary artery and MVA diameters are quantitative traits that exhibit significant heritability. In addition, our results suggest the presence of BAV independently influences the proximal Ao and pulmonary artery measures but not those in the descending Ao or MVA.
Mammographic density. Potential mechanisms of breast cancer risk associated with mammographic density: hypotheses based on epidemiological evidence
Lisa J Martin, Norman F Boyd
Breast Cancer Research , 2008, DOI: 10.1186/bcr1831
Abstract: Following Wolfe's original studies [1,2], the proportion of the breast area in the mammogram that is occupied by radiologically dense breast tissue (mammographic density) is now recognized to be a strong risk factor for breast cancer that may account for a large fraction of the disease [3,4] (see the review by Vachon and coworkers in this series [5]). In the present paper we review what is known of the aetiology of mammographic density and outline hypotheses for its association with risk for breast cancer.We describe below the evidence that mammographic density is a marker of susceptibility to breast cancer, and we review what is known of the histology of radiologically dense breast tissue, and the influence of other risk factors for breast cancer. We describe associations of hormones, growth factors and a mutagen with mammographic density, and the evidence that mammographic density is influenced by genetic variants.We propose that cumulative exposure to mammographic density may be an important determinant of breast cancer incidence, and that the risk for breast cancer associated with mammographic density may be explained by the combined effects of mitogens, which influence cell proliferation and the size of the cell population in the breast, and mutagens, which influence the likelihood of genetic damage to those cells. Figure 1 panels a and b, respectively, provide a schematic overview and a more detailed description of aspects of these hypotheses that are examined in the sections that follow. The available evidence is incomplete in many of these areas, however. In addition, all studies of the aetiology of mammographic density are constrained by the limitations of current methods of measuring density (see the review by Yaffe and coworkers in this series [5]).Ultimately, the risk for breast cancer associated with mammographic density will be elucidated by an improved understanding of the biology of the breast (see the review by Tisty and coworkers in this series [5]
Mammographic density
Norman F Boyd, Lisa J Martin, Martin Yaffe, Salomon Minkin
Breast Cancer Research , 2009, DOI: 10.1186/bcr2423
Abstract: McCormack and dos Santos Silva have reviewed the data on the association of percentage mammographic density (PMD) with risk of breast cancer in a systematic meta-analysis of data for >14,000 cases and 226,000 noncases from 42 studies [1]. They found that PMD was consistently associated with risk of breast cancer. Associations were stronger in studies in the general population, rather than in symptomatic women, for percentage density rather than for Wolfe categories, and in studies of incident cancer rather than prevalent cancer. The breast cancer risk associated with density did not differ by age, menopausal status or ethnicity and cannot be explained by the masking of cancers by dense tissue [2].A total of 10 cohort studies have been reported to date, all carried out as case-control studies nested within cohorts that used quantitative methods to classify PMD [2-10]. The interval between the mammogram used to classify PMD and the date of diagnosis of breast cancer varied from 1 year to 10 years. Methods of classifying PMD in analysis varied among these studies, but all showed a substantial increase in breast cancer risk across over the partitions of PMD examined, with most odds ratios being between 4 and 5. PMD is associated with a risk of breast cancer at screening and between screening examinations [2,11].Mammographic density expressed as either a percentage of the area of the breast (PMD) or as the area of dense tissue (cm2) in a mammogram are both positively associated with risk of breast cancer, but PMD is the stronger association [5].PMD has a consistent strong influence on breast cancer risk, is independent of other risk factors, has a larger gradient in risk than most other risk factors, has an increased risk that extends for at least 10 years after the mammogram used to classify density, and carries a risk not explained by masking.Examples of mammographic density of varying extents are shown in Figure 1. Four principal methods have been used to date to asse
Accounting for a Quantitative Trait Locus for Plasma Triglyceride Levels: Utilization of Variants in Multiple Genes
Lisa J. Martin, Ahmed H. Kissebah, Michael Olivier
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034614
Abstract: Background For decades, research efforts have tried to uncover the underlying genetic basis of human susceptibility to a variety of diseases. Linkage studies have resulted in highly replicated findings and helped identify quantitative trait loci (QTL) for many complex traits; however identification of specific alleles accounting for linkage remains elusive. The purpose of this study was to determine whether with a sufficient number of variants a linkage signal can be fully explained. Method We used comprehensive fine-mapping using a dense set of single nucleotide polymorphisms (SNPs) across the entire quantitative trait locus (QTL) on human chromosome 7q36 linked to plasma triglyceride levels. Analyses included measured genotype and combined linkage association analyses. Results Screening this linkage region, we found an over representation of nominally significant associations in five genes (MLL3, DPP6, PAXIP1, HTR5A, INSIG1). However, no single genetic variant was sufficient to account for the linkage. On the other hand, multiple variants capturing the variation in these five genes did account for the linkage at this locus. Permutation analyses suggested that this reduction in LOD score was unlikely to have occurred by chance (p = 0.008). Discussion With recent findings, it has become clear that most complex traits are influenced by a large number of genetic variants each contributing only a small percentage to the overall phenotype. We found that with a sufficient number of variants, the linkage can be fully explained. The results from this analysis suggest that perhaps the failure to identify causal variants for linkage peaks may be due to multiple variants under the linkage peak with small individual effect, rather than a single variant of large effect.
Quantitative criteria for improving performance of buccal DNA for high-throughput genetic analysis
Woo Jessica G,Martin Lisa J,Ding Lili,Brown W
BMC Genetics , 2012, DOI: 10.1186/1471-2156-13-75
Abstract: Background DNA from buccal brush samples is being used for high-throughput analyses in a variety of applications, but the impact of sample type on genotyping success and downstream statistical analysis remains unclear. The objective of the current study was to determine laboratory predictors of genotyping failure among buccal DNA samples, and to evaluate the successfully genotyped results with respect to analytic quality control metrics. Sample and genotyping characteristics were compared between buccal and blood samples collected in the population-based Genetic and Environmental Risk Factors for Hemorrhagic Stroke (GERFHS) study (https://gerfhs.phs.wfubmc.edu/public/index.cfm). Results Seven-hundred eight (708) buccal and 142 blood DNA samples were analyzed for laboratory-based and analysis metrics. Overall genotyping failure rates were not statistically different between buccal (11.3%) and blood (7.0%, p = 0.18) samples; however, both the Contrast Quality Control (cQC) rate and the dynamic model (DM) call rates were lower among buccal DNA samples (p < 0.0001). The ratio of double-stranded to total DNA (ds/total ratio) in the buccal samples was the only laboratory characteristic predicting sample success (p < 0.0001). A threshold of at least 34% ds/total DNA provided specificity of 98.7% with a 90.5% negative predictive value for eliminating probable failures. After genotyping, median sample call rates (99.1% vs. 99.4%, p < 0.0001) and heterozygosity rates (25.6% vs. 25.7%, p = 0.006) were lower for buccal versus blood DNA samples, respectively, but absolute differences were small. Minor allele frequency differences from HapMap were smaller for buccal than blood samples, and both sample types demonstrated tight genotyping clusters, even for rare alleles. Conclusions We identified a buccal sample characteristic, a ratio of ds/total DNA <34%, which distinguished buccal DNA samples likely to fail high-throughput genotyping. Applying this threshold, the quality of final genotyping resulting from buccal samples is somewhat lower, but compares favorably to blood. Caution is warranted if cases and controls have different sample types, but buccal samples provide comparable results to blood samples in large-scale genotyping analyses.
Mammographic density and breast cancer risk: current understanding and future prospects
Norman F Boyd, Lisa J Martin, Martin J Yaffe, Salomon Minkin
Breast Cancer Research , 2011, DOI: 10.1186/bcr2942
Abstract: Breast density, assessed by mammography and expressed as a percentage of the mammogram occupied by radiologically dense tissue (percent mammographic density, or PMD), reflects variations in breast tissue composition and is strongly associated with breast cancer risk [1]. Here, we review the evidence that PMD is a risk factor for breast cancer, histological and other factors associated with variations in PMD, and the biological plausibility of the associations with risk of breast cancer. We discuss the potential clinical applications of this risk factor in screening, in research on breast cancer prevention, and in risk prediction in individuals. Mammographic density has been the subject of a meta-analysis (see next section) [1] and a recent review [2] and readers are referred to these sources for additional information.The radiographic appearance of the breast on mammography varies among women, as illustrated in Figure 1, and reflects variations in breast tissue composition and the different x-ray attenuation characteristics of these tissues [3]. Fat is radiologically lucent and appears dark on a mammogram. Connective and epithelial tissues are radiologically dense and appear light. This appearance is usually expressed as a percentage of the breast area, or (as referred to here) as percent mammographic density (PMD).In a systematic meta-analysis of data for more than 14,000 cases and 226,000 non-cases from 42 studies, McCormack and dos Santos Silva [1] reviewed the data on the association of PMD with risk of breast cancer. The authors found that PMD was consistently associated with risk of breast cancer. Associations were stronger in studies in the general population rather than symptomatic women, in studies of incident rather than prevalent cancer, and for percent density rather than Wolfe's classification. Wolfe was the first to describe differences in breast cancer risk associated with variations in the mammographic appearance of the breast [4,5]; he used four cat
Risk factors for breast cancer in postmenopausal Caucasian and Chinese-Canadian women
Carolyn Y Tam, Lisa J Martin, Gregory Hislop, Anthony J Hanley, Salomon Minkin, Norman F Boyd
Breast Cancer Research , 2010, DOI: 10.1186/bcr2465
Abstract: We compared breast cancer risk factors among three groups of postmenopausal Canadian women at substantially different risk of developing breast cancer - Caucasians (N = 413), Chinese women born in the West or who migrated to the West before age 21 (N = 216), and recent Chinese migrants (N = 421). Information on risk factors and dietary acculturation were collected by telephone interviews using questionnaires, and anthropometric measurements were taken at a home visit.Compared to Caucasians, recent Chinese migrants weighed on average 14 kg less, were 6 cm shorter, had menarche a year later, were more often parous, less often had a family history of breast cancer or a benign breast biopsy, a higher Chinese dietary score, and a lower Western dietary score. For most of these variables, Western born Chinese and early Chinese migrants had values intermediate between those of Caucasians and recent Chinese migrants. We estimated five-year absolute risks for breast cancer using the Gail Model and found that risk estimates in Caucasians would be reduced by only 11% if they had the risk factor profile of recent Chinese migrants for the risk factors in the Gail Model.Our results suggest that in addition to the risk factors in the Gail Model, there likely are other factors that also contribute to the large difference in breast cancer risk between Canada and China.The age-adjusted incidence of breast cancer varies greatly around the world, with higher rates in developed than in developing regions [1]. For the period of 1998 to 2002, rates were 81 per 100,000 in Canada, 41 per 100 000 in Hong Kong, 31 and 35 per 100 000 respectively in Guangzhou City and Shanghai, urban areas in Mainland China, and 15 per 100 000 in rural areas in Mainland China [1]. Differences in age-specific breast cancer incidence between countries are especially large after menopause [1].The reasons for the international variation in incidence rates are unclear. However, rates in low-risk populations increase
Arterial Structure and Function in Ambulatory Adolescents with Cerebral Palsy Are Not Different from Healthy Controls
Audra A. Martin,Lisa M. Cotie,Brian W. Timmons,Jan Willem Gorter,Maureen J. MacDonald
International Journal of Pediatrics , 2012, DOI: 10.1155/2012/168209
Abstract: Physical inactivity in youth with cerebral palsy (CP) places them at increased risk of developing cardiovascular disease. The current study assessed indices of arterial health in adolescents with CP, classified as levels I-II of the Gross Motor Function Classification System (GMFCS) (=11, age 13.2±2.1 yr), in comparison to age- and sex-matched controls (=11, age 12.4±2.3 yr). Groups were similar in anthropometric measurements, resting blood pressures, and heart rates. There were no group differences in brachial flow-mediated dilation (11.1±7.8 versus 6.1±3.6), carotid intima-media thickness (0.42±0.04 versus 0.41±0.03 mm), and distensibility (0.008±0.002 versus 0.008±0.002 mmHg) or central (4.3±0.6 versus 4.1±0.9 m/s) and peripheral pulse wave velocity (7.1±1.7 versus 7.6±1.1 m/s); CP versus healthy controls, respectively. Vigorous intensity physical activity (PA) was lower in the CP group (CP: 38±80 min versus controls: 196±174 min); groups were similar in light and moderate intensity PA levels. Arterial health of ambulatory youth with CP is not different from a control group despite lower vigorous PA levels. Similar studies need to examine individuals with more pronounced mobility limitations (GMFCS level III–V).
Immobilized probe and glass surface chemistry as variables in microarray fabrication
Martin J Hessner, Lisa Meyer, Jennifer Tackes, Sanaa Muheisen, Xujing Wang
BMC Genomics , 2004, DOI: 10.1186/1471-2164-5-53
Abstract: When array element fluorescein intensity drops below 5,000 RFU/pixel, gene expression measurements become increasingly compressed, thereby validating this value as a prehybridization quality control threshold. We observe that the DNA retention capacity of in-house poly-L-lysine slides decreases rapidly over time (~50% reduction between 3 and 12 weeks post-coating; p < 0.0002) and that there are considerable differences in retention characteristics among commercially available poly-L-lysine and amino silane-coated slides.High DNA retention rates are necessary for accurate gene expression measurements. Therefore, an understanding of the characteristics and optimization of protocols to an array surface are prerequisites to fabrication of high quality arrays.The generation of reliable gene expression data with cDNA microarrays requires fabrication of quality arrays. This task encompasses the amplification of adequate amounts of concentrated PCR product for use as probe from the cDNA clone, followed by ordered arraying of the probes onto coated glass slides. The glass slide is a key variable in either spotted cDNA or oligonucleotide array fabrication since it must possess: 1) a uniform surface that yields spots of consistent shape and size, 2) low background fluorescence, and 3) high DNA retention capacity. Since the array is clearly a source of experimental variability, we have developed a novel three-color array approach where it is possible to directly visualize either cDNA or oligonucleotide arrays prior to hybridization [1-3]. For cDNA arrays, the probes are easily tagged with a third, Cy3/Cy5 compatible, fluorescent dye (fluorescein) during amplification. After purification of PCR products, which includes removal of unincorporated oligonucleotide primer, the detected fluorescein fluorescence represents deposited cDNA probe on the array. This three-color approach allows for assessment of slide fabrication independent of hybridization, thereby enabling 1) direct visu
Intimate femicide-suicide in South Africa: a cross-sectional study
Mathews,Shanaaz; Abrahams,Naeemah; Jewkes,Rachel; Martin,Lorna J; Lombard,Carl; Vetten,Lisa;
Bulletin of the World Health Organization , 2008, DOI: 10.1590/S0042-96862008000700015
Abstract: objective: to examine the incidence and patterns of intimate femicide-suicide in south africa and to describe the factors associated with an increase in the risk of suicide after intimate femicide (i.e. the killing of an intimate female partner). methods: a cross-sectional retrospective national mortuary-based study was conducted at a proportionate random sample of 25 legal laboratories to identify all homicides committed in 1999 of women aged over 13 years. data were collected from the mortuary file, autopsy report and a police interview. findings: among 1349 perpetrators of intimate femicide,19.4% committed suicide within a week of the murder. suicide after intimate femicide was more likely if the perpetrator was from a white rather than an african racial background (odds ratio, or: 5.8; 95% confidence interval, ci: 1.21-27.84); was employed as a professional or white-collar worker rather than a blue-collar worker (or: 37.28; 95% ci: 5.82-238.93); and owned a legal gun rather than not owning a legal gun (or: 45.26; 95% ci: 8.33-245.8). the attributable fraction shows that 91.5% of the deaths of legal gun-owning perpetrators and their victims may have been averted if this group of perpetrators did not own a legal gun. conclusion: south africa has a rate of intimate femicide-suicide that exceeds reported rates for other countries. this study highlights the public health impact of legal gun ownership in cases of intimate femicide-suicide.
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