Biomedical subjects

David R Williams

Publications and source records attributed to David R Williams.

At least 55 records · Page 3Linked to original sources

PubMed2005

Stress, life events, and socioeconomic disparities in health: results from the Americans' Changing Lives Study.

It has been hypothesized that exposure to stress and negative life events is related to poor health outcomes, and that differential exposure to stress plays a role in socioeconomic disparities in health. Data from three waves of the Americans' Changing Lives study (n = 3,617) were analyzed to investigate prospectively the relationship among socioeconomic indicators, five measures of stress/negative life events, and the health outcomes of mortality, functional limitations, and self-rated health. The results revealed that (1) life events and other types of stressors are clearly related to socioeconomic position; (2) a count of negative lifetime events was positively associated with mortality; (3) a higher score on a financial stress scale was predictive of severe/moderate functional limitations and fair/poor self-rated health at wave 3; and (4) a higher score on a parental stress scale was predictive of fair/poor self-rated health at wave 3. The negative effects of low income on functional limitations attenuated to insignificance when waves 1 and 2 stress/life event measures were controlled for, but other socioeconomic disparities in health change remained sizable and significant when adjusted for exposure to stressors. The results support the hypothesis that differential exposure to stress and negative life events is one of many ways in which socioeconomic inequalities in health are produced in society.

Adult↗

PubMed2005

Effect of wavelength on in vivo images of the human cone mosaic.

In images of the human fundus, the fraction of the total returning light that comes from the choroidal layers behind the retina increases with wavelength [Appl. Opt. 28, 1061 (1989); Vision Res. 36, 2229 (1996)]. There is also evidence that light originating behind the receptors is not coupled into the receptor waveguides en route to the pupil [S. A. Burns et al., Noninvasive Assessment of the Visual System, Vol. 11 of 1997 Trends in Optics and Photonics Series, D. Yager, ed. (Optical Society of America, 1997), p. al; Invest. Ophthalmol. Visual Sci. 38, 1657 (1997)]. These observations imply that the contrast of images of the cone mosaic should be greatly reduced with increasing wavelength. This hypothesis was tested by imaging the light distributions in both the planes of the photoreceptors and the pupil at three wavelengths, 550, 650, and 750 nm, with the Rochester adaptive optics ophthalmoscope. Surprisingly, the contrast of the retinal images varied only slightly with wavelength. Furthermore, the ratio of the receptorally guided component to the total reflected light measured in the pupil plane was found to be similar at each wavelength, suggesting that, throughout this wavelength range, the scattered light from the deeper layers in the retina is guided through the receptors on its return path to the pupil.

Adult↗

PubMed2005

Assessment of simulated surgical skills in parabolic microgravity.

BACKGROUND: During spaceflight crew health is paramount in the success of flight missions. The delivery of healthcare during flight requires crew readiness for medical and surgical response. METHODS: There were 20 participants who were evaluated for accurate performance of 4 basic laparoscopic surgical skills (clip applying, cutting, grasping, and suturing) during parabolic weightlessness using an inanimate workstation aboard the NASA KC-135 aircraft. RESULTS: Data indicate that motor skill performance decreased within the parabolic microgravity flight environment. Performance in parabolic microgravity flight included futile effort with an increase in number of tasks attempted and a decrease in tasks completed successfully. CONCLUSIONS: There is a decreased frequency of accurate task completion in parabolic microgravity flight, but it is not an obstacle to implementation of effective training for providing in-flight medical care. The data reveal that individuals perform basic laparoscopic surgical simulation with greater effort in microgravity following simulation training.

Aerospace Medicine↗

PubMed2005

Animal surgery during spaceflight on the Neurolab Shuttle mission.

INTRODUCTION: A surgical procedure has never been required or performed on a human in space. Parabolic microgravity simulations have suggested that surgery would be technically feasible during spaceflight. PROCEDURES: Survival surgery was performed for the first time on rats during the STS-90 Neurolab Shuttle mission. Craniotomy, leg dissection, thoracotomy, laminectomy, and laparotomy were performed as a part of physiological investigations. RESULTS: Surgical techniques successfully demonstrated in rats during spaceflight included general anesthesia, wound closure, wound healing, hemostasis, control of surgical fluids, operator restraint, and control of surgical instruments. No decrement in manual dexterity was noted by the crew, although operative time was longer compared with ground experience due to the need to maintain restraint of surgical supplies and instruments. CONCLUSIONS: The demonstration that technically demanding dissections could be accomplished successfully in space on rats suggests that comparable complex surgical procedures should be feasible on humans, if necessary, on future long-duration missions.

Aerospace Medicine↗

PubMed2005

Healthcare administration education in the 21st century: the case for entrepreneurship.

This paper recommends the broadening of the course content in several of the current required courses within the core curriculum of healthcare management education to include entrepreneurship topics and the inclusion of a separate entrepreneurship course. The current state of entrepreneurship within healthcare is described through the discussion of a healthcare entrepreneurship continuum. Because of the evolution of the healthcare industry in the past ten years, healthcare administration programs must also evolve to make our curriculum more relevant and increase student placement options. The current healthcare administration education shortcomings are discussed and recommendations for curriculum change are presented. Finally, a readings and resources list is provided as a basis for further curriculum development.

Curriculum↗

PubMed2005

Sociocultural methods in the Jackson Heart Study: conceptual and descriptive overview.

The Jackson Heart Study (JHS) is a prospective, population-based cohort study designed to investigate risk factors for cardiovascular disease (CVD) in African-American men and women. An aim of the JHS is the elucidation of the role that sociocultural factors play in the excess CVD risk and mortality in African Americans. Considerable evidence is available to document the influence of social, cultural, psychological, and other lifestyle risk factors on cardiovascular outcomes. Far less is known about how these factors affect health outcomes for African Americans. The JHS provides a unique opportunity to evaluate the presence and impact of these factors in this ethnoracial group. This paper describes the rationale and overall approach for sociocultural assessment in the JHS, both generally and for each content area.

Adult↗

PubMed2004

Asymmetric conjugate addition for the preparation of syn-1,3-dimethyl arrays: synthesis and structure elucidation of capensifuranone.

The synthesis of capensifuranone (1) has been achieved by the application of developments for asymmetric conjugate addition reactions of organocopper reagents with nonracemic N-enoyl-4-phenyl-1,3-oxazolidinones for the preparation of 1,3-syn-dimethyl arrays. The assignment of relative and absolute stereochemistry of 1 has been made following the high-field NMR characterizations of synthetic diol derivatives. The previously unassigned C4 stereochemistry of 1 was determined to be of the (S)-configuration. The thermodynamic equilibration of capensifuranone and its C4 diastereomer has been examined.

Animals↗

PubMed2004

Studies of stereocontrolled allylation reactions for the total synthesis of phorboxazole A.

A highly convergent total synthesis of the potent anticancer agent (+)-phorboxazole A (1) is accomplished. Four components (3-6) are assembled with considerations for control of absolute and relative stereochemistry. Iterative asymmetric allylation methodology addresses key stereochemical features in the preparation of the 2,6-cis- and 2,6-trans-tetrahydropyranyl rings of the C3-C19 component (3). The stereocontrolled asymmetric allylation process is also used for development of the C28-C41 fragment (4). Novel Barbier coupling reactions of alpha-iodomethyl oxazoles and related thiazoles are described with samarium iodide. The convergent assembly of components 4 and 5 features formation of the fully substituted C22-C26 pyran by intramolecular capture of an allyl cation intermediate with high facial selectivity, and further efforts lead to E-C19/C20 olefination. The synthesis culminates with use of a modified Julia olefination for attachment of the C42-C46 segment and subsequent late-stage macrocyclization by installation of the (Z)-C2/C3 alpha,beta-unsaturated lactone.

Animals↗

PubMed2004

Blood pressure reactivity to psychological stress predicts hypertension in the CARDIA study.

BACKGROUND: A longstanding but controversial hypothesis is that individuals who exhibit frequent, large increases in blood pressure (BP) during psychological stress are at risk for developing essential hypertension. We tested whether BP changes during psychological stress predict incident hypertension in young adults. METHODS AND RESULTS: We used survival analysis to predict hypertensive status during 13 years of follow-up in a sample of >4100 normotensive black and white men and women (age at entry, 18 to 30 years) enrolled in the CARDIA study. BP responses to 3 psychological challenges--cold pressor, star tracing, and video game tasks--were measured. Hypertensive status was defined as use of antihypertensive medication or measured BP > or =140/90 mm Hg. After adjustment for race, gender, covariates (education, body mass index, age, and resting pressure), and their significant interactions, the larger the BP responses were to each of the 3 tasks, the earlier hypertension occurred (P<0.0001 to <0.01). The systolic BP effect for the cold pressor task was apparent for women and for whites in race- and gender-specific models, whereas the diastolic BP effect for the video game was apparent for men. CONCLUSIONS: Young adults who show a large BP response to psychological stress may be at risk for hypertension as they approach midlife.

Adolescent↗

PubMed2004

The concept and measurement of race and their relationship to public health: a review focused on Brazil and the United States.

Race has been widely used in studies on health and healthcare inequalities, especially in the United States. Validity and reliability problems with race measurement are of concern in public health. This article reviews the literature on the concept and measurement of race and compares how the findings apply to the United States and Brazil. We discuss in detail the data quality issues related to the measurement of race and the problems raised by measuring race in multiracial societies like Brazil. We discuss how these issues and problems apply to public health and make recommendations about the measurement of race in medical records and public health research.

Brazil↗

PubMed2004

Functional photoreceptor loss revealed with adaptive optics: an alternate cause of color blindness.

There is enormous variation in the X-linked L/M (long/middle wavelength sensitive) gene array underlying "normal" color vision in humans. This variability has been shown to underlie individual variation in color matching behavior. Recently, red-green color blindness has also been shown to be associated with distinctly different genotypes. This has opened the possibility that there may be important phenotypic differences within classically defined groups of color blind individuals. Here, adaptive optics retinal imaging has revealed a mechanism for producing dichromatic color vision in which the expression of a mutant cone photopigment gene leads to the loss of the entire corresponding class of cone photoreceptor cells. Previously, the theory that common forms of inherited color blindness could be caused by the loss of photoreceptor cells had been discounted. We confirm that remarkably, this loss of one-third of the cones does not impair any aspect of vision other than color.

Adult↗

PubMed2004

Neural compensation for the eye's optical aberrations.

A fundamental problem facing sensory systems is to recover useful information about the external world from signals that are corrupted by the sensory process itself. Retinal images in the human eye are affected by optical aberrations that cannot be corrected with ordinary spectacles or contact lenses, and the specific pattern of these aberrations is different in every eye. Though these aberrations always blur the retinal image, our subjective impression is that the visual world is sharp and clear, suggesting that the brain might compensate for their subjective influence. The recent introduction of adaptive optics to control the eye's aberrations now makes it possible to directly test this idea. If the brain compensates for the eye's aberrations, vision should be clearest with the eye's own aberrations rather than with unfamiliar ones. We asked subjects to view a stimulus through an adaptive optics system that either recreated their own aberrations or a rotated version of them. For all five subjects tested, the stimulus seen with the subject's own aberrations was always sharper than when seen through the rotated version. This supports the hypothesis that the neural visual system is adapted to the eye's aberrations, thereby removing somehow the effects of blur generated by the sensory apparatus from visual experience. This result could have important implications for methods to correct higher order aberrations with customized refractive surgery because some benefits of optimizing the correction optically might be undone by the nervous system's compensation for the old aberrations.

Adaptation, Physiological↗

PubMed2004

Carbolithiation for the generation of cyclooctadienyl anions and tandem electrocyclization/alkylation to functionalized cis-bicyclo[3.3.0]octenes.

A powerful cascade reaction process for the construction of functionalized cis-bicyclo[3.3.0]octenes has been developed. Carbolithiation of 3-methylene-1,4-cyclooctadiene with 1 degrees , 2 degrees , or 3 degrees alkyllithium reagents leads to cyclooctadienyl anions, which undergo disrotatory electrocyclization and subsequent trapping with carbon, oxygen, sulfur, or silicon electrophiles to provide functionalized cis-bicyclo[3.3.0]octenes. Transmetalation of the allyllithium intermediates allowed access to the cuprate manifold of reactivity. The rapid construction of a linear triquinane using this methodology demonstrates the potential for synthetic applications.

Alkenes↗

PubMed2004

L and M cone contributions to the midget and parasol ganglion cell receptive fields of macaque monkey retina.

Analysis of cone inputs to primate parvocellular ganglion cells suggests that red-green spectral opponency results when connections segregate input from long wavelength (L) or middle wavelength (M) sensitive cones to receptive field centers and surrounds. However, selective circuitry is not an obvious retinal feature. Rather, cone receptive field surrounds and H1 horizontal cells get mixed L and M cone input, likely indiscriminately sampled from the randomly arranged cones of the photoreceptor mosaic. Red-green spectral opponency is consistent with random connections in central retina where the mixed cone ganglion cell surround is opposed by a single cone input to the receptive field center, but not in peripheral retina where centers get multiple cone inputs. The selective and random connection hypotheses might be reconciled if cone type selective circuitry existed in inner retina. If so, the segregation of L and M cone inputs to receptive field centers and surrounds would increase from horizontal to ganglion cell, and opponency would remain strong in peripheral retina. We measured the relative strengths of L and M cone inputs to H1 horizontal cells and parasol and midget ganglion cells by recording intracellular physiological responses from morphologically identified neurons in an in vitro preparation of the macaque monkey retina. The relative strength of L and M cone inputs to H1 and ganglion cells at the same locations matched closely. Peripheral midget cells were nonopponent. These results suggest that peripheral H1 and ganglion cells inherit their L and M cone inputs from the photoreceptor mosaic unmodified by selective circuitry.

Animals↗

PubMed2004

Psychogenic palatal tremor.

Recent criteria for the classification of palatal tremor use clinical, imaging, and electrophysiological features to differentiate essential and symptomatic forms. A case of probable psychogenic palatal tremor (PPT) is described within the context of these criteria, which lack clear guidelines for diagnosing PPT. The heterogenous nature of essential palatal tremor and its relationship with PPT, voluntary palatal movements, and tics is discussed.

Adult↗

PubMed2004

Gaze-evoked brainstem myoclonus.

The clinical and electrophysiological aspects of a case where brainstem reticular reflex myoclonus was related to an enlarging pontine lesion are described. It had the unusual characteristic of being evoked by sustained up gaze and left gaze.

Adult↗

PubMed2004

The National Survey of American Life: a study of racial, ethnic and cultural influences on mental disorders and mental health.

The objectives of the National Survey of American Life (NSAL) are to investigate the nature, severity, and impairment of mental disorders among national samples of the black and non-Hispanic white (n = 1,006) populations in the US. Special emphasis in the study is given to the nature of race and ethnicity within the black population by selecting and interviewing national samples of African-American (N = 3,570), and Afro-Caribbean (N = 1,623) immigrant and second and older generation populations. National multi-stage probability methods were used in generating the samples and race/ethnic matching of interviewers and respondents were used in the largely face-to-face interview, which lasted on average 2 hours and 20 minutes. The Diagnostic and Statistical Manual (DSM) IV World Mental Health Composite Interview (WHO-CIDI) was used to assess a wide range of serious mental disorders, potential risk and resilience factors, and help seeking and service use patterns. This paper provides an overview of the design of the NSAL, sample selection procedures, recruitment and training of the national interviewing team, and some of the special problems faced in interviewing ethnically and racially diverse national samples. Unique features of sample design, including special screening and listing procedures, interviewer training and supervision, and response rate outcomes are described.

Adaptation, Psychological↗

PubMed2004

The South Africa Stress and Health Study: rationale and design.

The South Africa Stress and Health Study (SASH) is a large psychiatric epidemiological survey that is currently underway in South Africa. It is a part of the World Health Organization's World Mental Health (WMH) 2000 initiative and seeks to complete interviews with a nationally representative sample of 5000 adults. The WMH initiative is obtaining population-based data on the prevalence and severity of specific psychiatric disorders, demographic and psychosocial correlates of these diagnoses, and the levels and adequacy of mental health service utilization. SASH is using the fully structured pencil and paper version of the WHO Composite International Diagnostic Interview (CIDI) to assess lifetime and 12-month rates of mental disorders using both the DSM-IV and the ICD-10 diagnostic systems. In addition, the SASH seeks to collect information on the prevalence of exposure to physical and psychological torture in South Africa and to assess the association between such traumas and specific psychiatric disorders. It will also assess a broad range of risk factors and resources that may modify the association between exposure to human rights violations and mental health.

Health Surveys↗