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Biomedical subjects

Linda Phillips

Publications and source records attributed to Linda Phillips.

11 recordsLinked to original sources
PubMed2005

Diffusion tensor imaging of neurodevelopment in children and young adults.

Diffusion tensor magnetic resonance imaging (DTI) was used to study regional changes in the brain's development from childhood (8-12 years, mean 11.1 +/- 1.3, N = 32) to young adulthood (21-27 years, mean 24.4 +/- 1.8, N = 28). Mean diffusivity (Trace/3 apparent diffusion coefficient, ADC) and fractional anisotropy (FA) were measured in 30 regions of interest (ROIs) in 13 distinct brain structures. Correlational analysis was performed to detect changes within 8-12 years and within 21-27 years, and group analysis to compare childhood diffusion properties with young adult values. Increases of fractional anisotropy were seen in the genu of the corpus callosum, splenium of the corpus callosum, corona radiata, putamen, and head of the caudate nucleus within 8-12 years, and also between childhood and young adulthood. Reductions in Trace/3 ADC were observed in 9 of 13 structures within 8-12 years and into young adulthood as well. DTI demonstrates more widespread changes in the brain's microstructure with maturation than previous reports using conventional T1-weighted MRI scans. These findings suggest a continuation of the brain's microstructural development through adolescence.

Adult↗
PubMed2005

Imaging brain connectivity in children with diverse reading ability.

Reading is a complex cognitive skill that requires the coordination of multiple brain regions. Although functional neuroimaging studies highlight the cortical brain regions associated with a specific cognitive task like reading, they do not directly address the underlying neural connections necessary for efficient performance of this task. Adults with reading disability have demonstrated lower regional white matter connectivity, but it is not known whether this relationship between neuronal wiring and reading performance also holds in younger readers. Using diffusion tensor magnetic resonance imaging (DTI) that highlights the structural integrity of the brain wiring, we show that regional brain connectivity in the left temporo-parietal white matter correlates with a wide range of reading ability in children as young as 8-12 years old. Diffusion tensor tractography suggests that the posterior limb of the internal capsule is consistent with the location of the largest cluster of correlation between reading ability (Word Identification subtest) and fractional anisotropy. The maturation of the white matter may play a key role in the development of cognitive processes such as reading.

Anisotropy↗
PubMed2003

Anaerobic regulation of Actinobacillus actinomycetemcomitans leukotoxin transcription is ArcA/FnrA-independent and requires a novel promoter element.

The periodontal pathogen, Actinobacillus actinomycetemcomitans, produces a 116-kDa leukotoxin that appears to help the bacterium evade the innate host immune response. The expression of leukotoxin is induced when cells are grown anaerobically, a condition found in the subgingival crevice. This regulation most likely occurs at the transcriptional stage since the levels of leukotoxin RNA are induced by hypoxic growth. In order to map the leukotoxin promoter element(s) responsible for oxygen regulation, deletion and linker-scanning mutations were cloned into a transcriptional reporter gene plasmid and then tested in A. actinomycetemcomitans grown aerobically or anaerobically. A 35-bp DNA element, at position -36 to -70, was found to be responsible for the repression of leukotoxin synthesis in aerobically grown A. actinomycetemcomitans. The sequence of this oxygen response element (ORE) does not match the consensus binding sites for known DNA binding proteins, not even Fnr or ArcA which play major roles in oxygen regulation in other bacteria. However, since sequence analysis alone cannot disprove a role for the Fnr or ArcAB pathways in leukotoxin regulation, the genes for the Fnr and ArcA homologues in A. actinomycetemcomitans were identified, mutated by targeted insertional mutagenesis and assessed for loss of oxygen regulation. Deletion of either fnr or arcA altered the expression of numerous A. actinomycetemcomitans proteins, but leukotoxin expression was still repressed by oxygen. These results, coupled with the promoter mutation analyses, lead to the conclusion that A. actinomycetemcomitans employs a novel pathway in the aerobic/anaerobic regulation of leukotoxin synthesis.

Aggregatibacter actinomycetemcomitans↗
PubMed2002

Overview of the use of the U.S. EPA exposure factors handbook.

Risk assessments are important components of the decision making process. At hazardous waste sites, they are used as tools to determine appropriate cleanup levels. Therefore, it is critical that the best up-to-date methods, models, and exposure data are available to the exposure and risk assessor to realistically estimate the potential for human and ecological exposures to environmental contaminants. The EPA Exposure Factors Handbook published in 1997 is a tool available to exposure assessors which summarizes statistical data on exposure factors necessary to conduct human health exposure assessments. Since it was first published by EPA in 1989, the handbook has been the primary source of data for human exposure assessments. The purpose of this paper is to provide an overview of the handbook, its impact, applications, discussion about data gaps, and future directions.

Decision Making↗
PubMed2002

Infant exposure to dioxin-like compounds in breast milk.

We used a one-compartment, first-order pharmacokinetic model to predict the infant body burden of dioxin-like compounds that results from breast-feeding. Validation testing of the model showed a good match between predictions and measurements of dioxin toxic equivalents (TEQs) in breast-fed infants, and the exercise highlighted the importance of the assumption of the rate of dissipation of TEQs in the infant. We evaluated five nursing scenarios: no nursing (i.e., formula only), and nursing for 6 weeks, 6 months, 1 year, and 2 years. We assumed that an infant weighs 3.3 kg at birth and is exposed to a total of 800 pg TEQ/day by consumption of breast milk, leading to an estimated body weight-based dose of 242 pg TEQ/kg-day, which drops to 18 pg TEQ/kg-day after 1 year. This decline is due to declines in dioxin concentration in mother's milk and infant body weight increases. This range is significantly higher, on a body-weight basis, than adult TEQ exposure, which has been estimated to average about 1 pg TEQ/kg-day. For the nursing scenarios of >or= 6 months, we predict that body burdens (expressed as a body lipid concentration) peak at around 9 weeks at 44 ppt TEQ lipid. We predict that the body burden of the formula-fed infants will remain below 10 ppt TEQ lipid during the first year. These results compare to the current adult average body burden of 25 ppt TEQ lipid. We also found that an infant who had been breast-fed for 1 year had an accumulated dose 6 times higher than a 1-year-old infant who had not been breast-fed. For a 70-year lifetime, individuals who had been breast-fed had an accumulated dose 3-18% higher than individuals who had not been breast-fed.

Adult↗
PubMedDate not supplied

Challenges in language, culture, and modality: translating English measures into American sign language.

BACKGROUND: Few health-related questionnaires have been translated into American Sign Language (ASL), precluding Deaf adults from full participation in health-related research. OBJECTIVES: To translate self-report measures (written English) into sign language and to evaluate the equivalence of the ASL versions to the original English versions of the measures. METHODS: A descriptive-comparative design with a derived etic (outsider) perspective was used to evaluate equivalency between the English version of the Self-Rated Abilities for Health Practices (SRAHP) and an ASL version. Both versions were administered to 24 bilingual (English and ASL) adults. Analysis included correlation between total scores and comparison of internal consistency of both versions; psychometric properties of the signed SRAHP were computed for 105 Deaf adults who participated in a study of the Deaf Heart Health Intervention (DHHI). RESULTS: The correlation between total scores on ASL and English versions was .92, item-to-total correlations ranged from .08 to .80 on the English version and from .33 to .80 on the ASL version. Cronbach's alpha was .91 for the English version and .90 for the ASL version. Mean scores on the ASL version were significantly lower for the all-Deaf DHHI sample (n = 105) than for the bilingual subjects (n = 24) although internal consistency remained high (Cronbach's alpha of .93 and item-to-total correlation of .38-.74) for the new ASL version. DISCUSSION: The use of an adapted translation model resulted in a sound ASL version of a health-related measure. Results support use of the derived etic strategy for translating measures from their original language into new languages. The approach is also appropriate for changing modalities from written form to other modalities, such as the visual-manual modality of ASL.

Adolescent↗
PubMedDate not supplied

Key informants' perceptions of health care for elders at the U.S.-Mexico border.

OBJECTIVE: This study was part of a systematic assessment to gain an understanding of aging in a rural community along the U.S.-Mexico border in Arizona. DESIGN: It used a participatory action research design. Interviews were conducted among key informants (n = 29), including health and social services providers and community leaders. Content analysis focused on identifying common themes and concerns related to elders. RESULTS: Major themes identified were (1) social infrastructure issues, (2) community awareness of health problems, (3) socioeconomic problems, (4) cultural influences on health beliefs, practice, and use of services, (5) image of aging, (6) border issues, and (7) educational needs for service providers. CONCLUSION: Elders living at the border are a particularly vulnerable population with strong cultural affiliations and health disparities. Although the population of elders has been growing at the border, the traditional focus on the health care needs of youth and children has contributed to the neglect of issues facing elders. This study provided community key informants' perspective of aging to community members, policy makers, service agencies, and health care providers for community development. A conceptual framework was developed for educational programs and research projects for health professionals who care for elders at the border.

Aged↗
PubMedDate not supplied

Metric equivalence assessment in cross-cultural research: using an example of the Center for Epidemiological Studies--Depression Scale.

Metric equivalence is a quantitative way to assess cross-cultural equivalences of translated instruments by examining the patterns of psychometric properties based on cross-cultural data derived from both versions of the instrument. Metric equivalence checks at item and instrument levels can be used as a valuable tool to refine cross-cultural instruments. Korean and English versions of the Center for Epidemiological Studies-Depression Scale (CES-D) were administered to 154 Korean Americans and 151 Anglo Americans to illustrate approaches to assessing their metric equivalence. Inter-item and item-total correlations, Cronbach's alpha coefficients, and factor analysis were used for metric equivalence checks. The alpha coefficient for the Korean-American sample was 0.85 and 0.92 for the Anglo American sample. Although all items of the CES-D surpassed the desirable minimum of 0.30 in the Anglo American sample, four items did not meet the standard in the Korean American sample. Differences in average inter-item correlations were also noted between the two groups (0.25 for Korean Americans and 0.37 for Anglo Americans). Factor analysis identified two factors for both groups, and factor loadings showed similar patterns and congruence coefficients. Results of the item analysis procedures suggest the possibility of bias in certain items that may influence the sensitivity of the Korean version of the CES-D. These item biases also provide a possible explanation for the alpha differences. Although factor loadings showed similar patterns for the Korean and English versions of the CES-D, factorial similarity alone is not sufficient for testing the universality of the structure underlying an instrument.

Adolescent↗
PubMedDate not supplied

While I was sleeping.

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Attitude of Health Personnel↗