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PubMed1996

Disparity tuning of the stereoscopic (cyclopean) motion aftereffect.

Across five experiments this study investigated the disparity tuning of the stereoscopic motion aftereffect (adaptation from moving retinal disparity). Adapting and test stimuli were moving and stationary stereoscopic grating patterns, respectively, created from dynamic random-dot stereograms. Observers adapted to moving stereoscopic grating patterns presented with a given disparity and viewed stationary test patterns presented with the same or differing disparity to examine whether the motion aftereffect is disparity contingent. Across experiments aftereffect duration was greatest when adapting motion and test pattern both were presented with zero disparity and in the plane of fixation. Aftereffect declined as disparity of adapting motion and/or test pattern increased away from fixation, even under conditions in which depth position of adapt and test was equal. This argues against a relative depth separation explanation of the decline, and instead suggests that the amount of adaptable substrate decreases away from fixation.

Adaptation, Physiological↗

PubMed1983

Immune response of calves following the inoculation of Mycoplasma dispar and Mycoplasma bovis.

A small but significant reduction in the number of Mycoplasma dispar colonising the respiratory tract after intratracheal challenge was observed in gnotobiotic-calves previously inoculated subcutaneously three times with formalin-killed organisms and oil adjuvant. Injection of M. dispar by the intramuscular route, with oil adjuvant, and 2 weeks later by the intratracheal route, without adjuvant, failed to induce immunity to subsequent intratracheal challenge. Following the subcutaneous injection of killed M. dispar, the amount of antibody detected by single radial haemolysis (SRH) increased markedly with increasing age in groups of calves with average ages of 16 to 155 days when first injected. Most calves aged less than 40 days failed to produce an antibody response to a single injection of M. dispar. With M. bovis a smaller difference was observed between antibody levels generated in calves of different ages; also, calves less than 40 days old produced a detectable SRH antibody response following a single injection of killed M. bovis. IgG1 and IgG2 antibody to M. dispar and M. bovis were measured by ELISA. IgG1 appeared before IgG2 antibody and this was particularly pronounced in younger calves. Also, for both mycoplasmas IgG2 antibody levels were lower in younger than older calves. The IgG1 response to M. dispar was compared in three groups of calves with average ages of 16, 55 and 155 days and was greatest in the oldest and least in the youngest animals. In contrast, the IgG1 response to M. bovis varied little in calves of different ages. It therefore appears that the immune response of young calves to M. dispar is impaired or defective.

Animals↗

PubMed2004

Workshop on Alcohol Use and Health Disparities 2002: a call to arms.

The National Institute on Alcohol Abuse and Alcoholism (NIAAA) of the National Institutes of Health (NIH) sponsored a "Workshop on Alcohol Use and Health Disparities 2002: A Call to Arms," on December 5, 2002, in Bethesda, Maryland, USA. This workshop was part of the NIAAA/NIH comprehensive strategic plan to reduce, and ultimately eliminate, health disparities. Eleven topics were addressed: (1). biomedical risk factors that may contribute to disparities in the toxic effects of alcohol; (2). alcohol and gene-environment interactions that affect the health of diverse groups; (3). alcohol pharmacogenetics in Mexican-Americans; (4). determinants of risk for alcoholism in minority populations; (5). consideration of population groups in linkage-disequilibrium studies to identify genes associated with alcohol dependence; (6). interaction between alcohol dependence and African-American ethnicity in disordered sleep, nocturnal cytokines, and immunity; (7). disparities of brain functional reserve capacity affecting brain morbidity related to substance abuse; (8). alcohol and pregnancy disparities; (9). role of alcohol in cancer risk disparities; (10). ethnic diversity in alcoholic cardiomyopathy; and (11). postmenopausal health disparities. On the basis of these presentations, seven conclusions emerged: (1). Genetic variations in alcohol-metabolizing enzymes exist in various populations. (2). These enzymes play a role in the variation in health effect outcomes seen in different populations, owing to alcohol consumption. (3). Differences between and among population groups can be critically important for the design and interpretation of studies in genetics. These include differences in expression of phenotype, in locus heterogeneity, in risk alleles, and in population structure. (4). Incidence rates for fetal alcohol syndrome and fetal alcohol spectrum disorders are greater in African-Americans and Native-Americans than in Caucasians. Genetic polymorphisms, nutrition, and other factors may account for these differences. (5). The highest mortality rate for cirrhosis has been found in white Hispanic men. (6). Mexican-Americans have a low frequency of the protective alleles ADH1B(*)2 and ALDH2(*)2 and a relatively high frequency of CYP2E1 c2, which is associated with early onset alcoholism. (7). The incidence rate for cancer is greater for African-Americans than for Caucasians, and part of the higher risk may be attributed to heavier drinking.

Alcohol Drinking↗

PubMed2006

Exploring racial and ethnic disparities in prescription drug spending and use among Medicare beneficiaries.

BACKGROUND: Little is known about why minority Medicare beneficiaries spend less on and use fewer prescription drugs than white Medicare beneficiaries. OBJECTIVE: We explored whether population differences in demographic characteristics, socioeconomic status, and health status were associated with observed disparities by race and ethnicity in the prescription drug spending and use of noninstitutionalized elderly Medicare beneficiaries. METHODS: We used a nationally representative sample of 8101 white, 816 black, and 642 Hispanic Medicare beneficiaries from the 1999 Medicare Current Beneficiary Survey Cost and Use files. For each of these groups, we calculated total prescription drug spending, out-of-pocket spending, and number of prescriptions. We then used the Oaxaca-Blinder decomposition method to separate the impact of race and ethnicity on disparities in spending and use from the impact of differences in population characteristics across racial and ethnic groups. RESULTS: Much of the disparity in spending between whites and blacks and some of the disparity between whites and Hispanics can be attributed to race/ethnicity. Because of race/ethnicity, total spending for whites was 8.9% more than for blacks and 5.4% more than for Hispanics. Similarly, total out-of pocket spending for whites was 28.8% more than for blacks and 10.7% more than for Hispanics. Race/ethnicity also influenced the amount of prescription drug use. Whites used 2.3 more prescriptions than blacks and 1.6 more than Hispanics. However, these differences in use were offset by the impact of differences in population characteristics. CONCLUSIONS: Differences in factors identified in the Andersen model of access to care do not fully explain observed disparities in prescription drug use and spending. The portion of the disparities due to race and ethnicity may reflect patients' skepticism about medicine and medical care in general, patients' adherence to medical advice, patient-physician communication, physicians' prescribing habits, and usual source of care. Future research should explore whether these and other unobserved factors associated with race and ethnicity are responsible for disparities in drug spending and use.

Black or African American↗

PubMed2006

Overdiagnosis of Entamoeba histolytica and Entamoeba dispar in Nicaragua: a microscopic, triage parasite panel and PCR study.

BACKGROUND: Based on stool microscopy, an E. histolytica/E. dispar prevalence of 18.6% was found in León, Nicaragua about 10 years ago. Since then, new non-microscopic methods have been developed to discriminate between pathogenic E. histolytica and nonpathogenic E. dispar. The main objectives of the present study were to evaluate the true prevalence of E. histolytica among individuals with diarrhea and to assess the diagnostic procedures carried out at the health center level. METHODS: A descriptive study was carried out on patients with diarrhea. Parasite detection was performed by conventional microscopy on native preparations or concentrated and stained specimens, Triage Parasite Panel and by PCR for both E. histolytica and E. dispar. RESULTS: In 134 individuals with diarrhea, the prevalence of intestinal parasites was 69% as detected by direct stool examination. E. histolytica/E. dispar was found in eight (6%) of the samples, but the health centers reported 24%. In the Triage Parasite Panel only one case of E. histolytica/E. dispar was found. Analysis by PCR showed E. dispar in ten (7.5%) and E. histolytica in two cases (1.5%). The detection of intestinal coccidia and Dientamoeba fragilis required additional staining methods. CONCLUSIONS: PCR results showed that E. histolytica is a rare finding in patients with diarrhea. At the health centers, E. histolytica, E. histolytica/E. dispar were clearly overdiagnosed, with the consequence of overtreatment.

Animals↗

PubMed2006

Health disparities in Canada today: some evidence and a theoretical framework.

This paper documents contemporary evidence on patterns of health disparities in Canada and suggests theoretical mechanisms that give rise to these patterns. The overall health of Canadians, as measured by life expectancy or mortality, has improved dramatically over the past 30 years and some disparities have diminished slightly (e.g., life expectancy by income group for men), while others have increased (e.g., diabetes for Aboriginal peoples). Arguably the most egregious health disparities in Canada are those existing between Aboriginals and the rest of the Canadian population. This paper focuses specifically on three social determinants and their effects on disparities in health; Aboriginal status, income, and place. Overall we take the approach that disparities in health could be alleviated by reducing inequities in the distribution of these determinants. We further argue that these social determinants are proxies for opportunities, resources and constraints; all of which influence health outcomes. We suggest that policies focus on reducing the social inequities that lead to health disparities in Canada, rather than focusing on the disparities in health alone. Since the social determinants described here have been found to influence an array of disease outcomes, tackling them, rather than their outcomes, may have a greater overall influence on the health of the population.

Aged↗

PubMed2005

Trends in implantable cardioverter-defibrillator racial disparity: the importance of geography.

OBJECTIVES: The study was designed to determine whether racial disparity in utilization of the implantable cardioverter-defibrillator (ICD) has improved over time, and whether small-area geographic variation in ICD utilization contributed to national levels of racial disparity. BACKGROUND: Although racial disparities in cardiac procedures have been well-documented, it is unknown whether there has been improvement over time. Low ICD utilization rates in predominantly black geographic areas may have exacerbated national levels of disparity. METHODS: Discharge abstracts from elderly black and white Medicare beneficiaries hospitalized with ventricular arrhythmias from 1990 to 2000 were analyzed to determine if ICD implantation occurred within 90 days of initial hospitalization. Multivariate logistic regression models were constructed to assess the relationship between ICD implantation, year of admission, and the percentage of black inhabitants in each patient's county of hospitalization while controlling for clinical, hospital, and demographic characteristics. RESULTS: There was improvement in ICD implantation racial disparity: In the period 1990 to 1992, black patients had an odds ratio of 0.52 (95% confidence interval [CI] 0.42 to 0.64) for receiving an ICD compared with whites. However, by 1999 to 2000, the odds ratio for blacks had risen to 0.69 (95% CI 0.61 to 0.78) (test-for-trend p=0.01). Approximately 20% of this trend could be explained by reduction in geographic variation in ICD use between areas with larger black and predominantly white populations. CONCLUSIONS: Rates of ICD implants became more equal among whites and blacks during the 1990s, although persistent disparity remained at the decade's end. Geographic equalization in cardiovascular procedure rates may be an essential mechanism in rectifying disparities in health care.

Black or African American↗

PubMed2006

Asthma disparities in the prevalence, morbidity, and treatment of Latino children.

The paper reviews the existing research related to asthma disparities and frames the results of this research within a conceptual model modified from the Institute of Medicine model in order to explain asthma health disparities in Latino children in the USA. The model of pediatric asthma disparity presented is based on the conceptualization of health disparities as the result of a complex interaction of factors related to four main domains: the individual and family, the environment or context in which the child lives, the health-care system, and provider characteristics. Asthma disparities are discussed as they are reflected in the process of care (access and quality of treatment) and outcome (prevalence, morbidity, severity) experienced by Latino children. The potential mechanisms that may account for the asthma disparities documented as reflected by the conceptual model proposed are discussed. Finally, several suggestions for future research examining determinants that account for asthma disparities are examined.

Asthma↗

PubMed2004

Estimating racial/ethnic disparity in mammography rates: it all depends on how you ask the question.

BACKGROUND: Estimates of racial disparity in mammography appear to differ depending on the data source. This study examined the impact of different survey methodology on estimates of racial disparity in mammography. METHODS: Responses from 3,090 women > or =40 years to two different questions from the 1996 Medical Expenditure Panel Survey (MEPS) were compared when a mammogram was last obtained versus what medical services, including mammography, were obtained over a 4-month interval, aggregated across 1 year. RESULTS: There was no significant racial disparity in 1-year mammography prevalence based on the first question (white-black difference, 3.3%; 95% confidence interval [CI], -2.5, 9.2). In contrast, a significant disparity in 1-year mammography prevalence was found based on the medical services question (difference, 13.1%; 95% CI 8.6, 17.6). Disparity estimates by Hispanic ethnicity were similar for the two questions: white-Hispanic difference, 1.6%; 95% CI -4.3, 7.5, and white-Hispanic difference 5% (-0.2, 10.1). Adjustment for age, income, and insurance did not alter these findings. CONCLUSIONS: Estimates of racial, but not ethnic, disparities in mammography seem to depend on how the question is asked. These results caution against exclusive reliance on annual self-reports for monitoring disparities in preventive care.

Adult↗

PubMed1978

The relationship between fixation disparity and heterophoria.

Twenty-five asymptomatic subjects with normal binocular vision underwent determination of the magnitude and direction of their heterophoria and their fixation disparity. Fixation disparity was measured at a 2-m fixation distance with the phase-difference haploscope under conditions simulating those of casual seeing. When combined with careful attention to symmetrical control of accommodation, this method eliminates several known technical artifacts. Examples of the normal fluctuation of the magnitude and direction of fixation disparity for individual subjects were demonstrated. Whereas only a slight preponderance of subjects were esophoric, many subjects had convergent fixation disparity (esodisparity). Linear regression analysis of the data revealed a coefficient of correlation between fixation disparity and heterophoria at 6 m of 0.61, and at 33 cm of 0.50. The results suggest that normal, small magnitude heterophoria does not necessarily produce fixation disparity and that fixation disparity does not necessarily sustain heterophoria.

Adult↗

PubMed2001

Eliminating disparities in perinatal outcomes--lessons learned.

The disparity between blacks and whites in perinatal health ranges from a 2.3-fold excess risk among black women for preterm delivery and infant mortality to a 4-fold excess risk among black women for maternal mortality. To stimulate concerted public health action to address such racial and ethnic disparities in health, the national Healthy People objectives call for elimination of all health disparities by the year 2010. Eliminating health disparities requires a greater understanding of the factors that contribute to their development. This commentary summarizes the state of the science of reducing such disparities and proposes a framework for using the results of qualitative studies on the social context of pregnancy to understand, study, and address disparities in infant mortality and preterm delivery. Understanding the social context of African American women's lives can lead to an improved understanding of the etiology of preterm birth, and can help identify promising new interventions to reduce racial and ethnic disparities in preterm delivery.

Black or African American↗

PubMed2003

Racial and ethnic disparities in birth outcomes: a life-course perspective.

BACKGROUND: In the United States, Black infants have significantly worse birth outcomes than do White infants. The cause of these persisting racial disparities remains unexplained. Most extant studies focus on differential exposures to protective and risk factors during pregnancy, such as current socioeconomic status, maternal risky behaviors, prenatal care, psychosocial stress, or perinatal infections. These risk factors during pregnancy, however, do not adequately account for the disparities. METHODS: We conducted a literature review for longitudinal models of health disparities, and presented a synthesis of two leading models, using a life-course perspective. Traditional risk factors during pregnancy are then reexamined within their life-course context. We conclude with a discussion of the limitations and implications of the life-course perspective for future research, practice, and policy development. RESULTS: Two leading longitudinal models of health disparities were identified and discussed. The early programming model posits that exposures in early life could influence future reproductive potential. The cumulative pathways model conceptualizes decline in reproductive health resulting from cumulative wear and tear to the body's allostatic systems. We propose a synthesis of these two models, using the life-course perspective. Disparities in birth outcomes are the consequences of differential developmental trajectories set forth by early life experiences and cumulative allostatic load over the life course. CONCLUSIONS: Future research on racial disparities in birth outcomes needs to examine differential exposures to risk and protective factors not only during pregnancy, but over the life course of women. Eliminating disparities requires interventions and policy development that are more longitudinally and contextually integrated than currently prevail.

Black or African American↗

PubMed2001

Detection of simulated periodontal bone gain by digital subtraction radiography with tuned-aperture computed tomography. The effect of angular disparity.

OBJECTIVES: To investigate the influence of angular disparity on observer detection of simulated bone gain in digital subtraction radiography using tuned-aperture computed tomography (TACT). MATERIALS AND METHODS: Simulated periodontal defects were created in interproximal and buccal or lingual (tooth-obscured) areas of the premolar and molar regions of a dry human skull. Radiographs were obtained before and after known weights of amorphous bone were added to the defects to simulate bone gain. The skull was positioned in a multidirectional tomographic unit to achieve reproducibility. A series of nine basis images were acquired with a CMOS intra-oral receptor and repeated using angular disparities of 10 degrees, 20 degrees, and 30 degrees. Stacks of TACT slices generated from the basis images were paired for image-registration, histogram-equalization and subtraction using TACT Workbench. Eight calibrated observers randomly assessed the presence or absence of bone gain using a 5-point confidence scale. ROC curves were generated and A(z) values were analysed using ANOVA. RESULTS: There were significant differences in the performance of the observers (P=0.034), defect location (P=0.005), amount of bone gain (P<0.001), angular disparity (P=0.003) and angular disparity x defect location interaction (P=0.019). Mean A(z) values in detecting bone gain were 0.90, 0.85, 0.79 for angular disparities of 10 degrees, 20 degrees, and 30 degrees respectively. CONCLUSIONS: Smaller angular disparity provided better detection of bone gain with TACT-subtraction using nine basis-projections. This effect of angular disparity was especially evident with tooth-obscured defects.

Alveolar Bone Loss↗

PubMed1997

Sensitivity of Entamoeba histolytica and Entamoeba dispar patient isolates to human complement.

Twenty-one Entamoeba histolytica and 56 Entamoeba dispar patient isolates were investigated for their sensitivity to the classical and alternative pathway of human complement, E. histolytica and E. dispar patient isolates were differentiated by polymerase chain reaction and hexokinase isoenzyme typing. It was found that 90.3% (+/- 12.0%) of the trophozoites of E. histolytica were lysed after 30 min by the alternative pathway of complement in the presence of 50% human serum (19 isolates showed lysis rates higher than 80%), whereas E. dispar cells were less susceptible to the alternative pathway as 68.8% (+/- 28.2%) of lysis occurred. However, 23 of the E. dispar isolates were lysed between 100 and 80% (90.9% +/- 9.1%), demonstrating that about half of the tested E. dispar isolates were highly sensitive to complement lysis. Only 11 of the E. dispar isolates were proven to be ¿resistant' to the alternative pathway of complement and were lysed less than 40%. These results are in conflict to earlier publications, describing resistance of E. dispar to complement lysis (Hamelmann et al. 1992, 1993).

Animals↗

PubMed2006

Relaxation scenarios in a mixture of large and small spheres: dependence on the size disparity.

We present a computational investigation on the slow dynamics of a mixture of large and small soft spheres. By varying the size disparity at a moderate fixed composition different relaxation scenarios are observed for the small particles. For small disparity density-density correlators exhibit moderate stretching. Only small quantitative differences are observed between dynamic features for large and small particles. On the contrary, large disparity induces a clear time scale separation between the large and small particles. Density-density correlators for the small particles become extremely stretched and display logarithmic relaxation by properly tuning the temperature or the wave vector. Self-correlators decay much faster than density-density correlators. For very large size disparity, a complete separation between self- and collective dynamics is observed for the small particles. Self-correlators decay to zero at temperatures where density-density correlations are frozen. The dynamic picture obtained by varying the size disparity resembles features associated with mode coupling transition lines of the types B and A at, respectively, small and very large size disparities. Both lines might merge, at some intermediate disparity, at a higher-order point, to which logarithmic relaxation would be associated. This picture resembles predictions of a recent mode coupling theory for fluids confined in matrices with interconnected voids [V. Krakoviack, Phys. Rev. Lett. 94, 065703 (2005)].

Journal Article↗

PubMed1976

Binocular-disparity-dependent upper-lower hemifield anisotropy and left-right hemifield isotropy as revealed by dynamic random-dot stereograms.

Dynamic random-dot stereograms devoid of all monocular depth cues were used to measure the limits of temporal and spatial resolution in the center of the visual field. The temporal durations for detecting a small, briefly presented test square of different binocular disparity than the surround varied as a function of its location and binocular disparity. The test squares presented in the upper hemifield were detectable at consistently shorter durations than those presented in the lower hemifield for a surround disparity which was uncrossed relative to the fixation marker. For crossed surround disparity this preference reversed, resulting in a superiority of the lower hemifield. The anisotropy diminished for zero surround disparity. No such anisotropy was found when left and right visual hemifields were compared. It was also shown that this upper-lower temporal anisotropy (and left-right isotropy) is paralleled by a similar disparity-dependent upper-lower anistropy (and left-right isotropy) in spatial resolution. Introduction of monocular clues into the stereograms tended to eliminate the anisotropies. This implies that the anisotropies reflect the spatiotemporal properties and distribution of binocular disparity detectors in the human cortex and result in a tilted surface that pivots around the horizontal midline in the space of binocular depth perception.

Depth Perception↗

PubMed1982

The interpretation of stereo-disparity information: the computation of surface orientation and depth.

Two methods for interpreting disparity information are described. Neither requires extraretinal information to scale for distance: one method uses horizontal disparities to solve for the viewing distance, the other uses the vertical disparities. Method 1 requires the assumption that the disparities derive from a locally planar surface. Then from the horizontal disparities measured at four retinal locations the viewing distance and the equation of local surface 'patch' can be obtained. Method 2 does not need this assumption. The vertical disparities are first used to obtain the values of the gaze and viewing distance. These are then used to interpret the horizontal disparity information. An algorithm implementing the methods has been tested and is found to be subject to a perceptual phenomenon known as the 'induced effect'.

Depth Perception↗

PubMed1990

T cell requirements for the rejection of renal allografts bearing an isolated class I MHC disparity.

This study has examined the cellular and humoral responses underlying the rejection of rat renal allografts bearing an isolated RT1Aa class I MHC disparity. RT1Aa disparate kidneys were rejected promptly by high responder RT1u but not by low responder RT1c recipients (median survival time 10 d and greater than 100 d, respectively). The magnitude and phenotype of the cellular infiltrate were similar in rejecting and nonrejecting RT1Aa disparate kidneys. Paradoxically, graft infiltrating cells and spleen cells from RT1u recipients showed minimal ability to lyse donor strain lymphoblasts in vitro, whereas effector cells from RT1c recipients showed modest levels of cytotoxicity. Injection of RT1u rats with MRC OX8 mAb was highly effective at selectively depleting CD8+ cells from graft recipients but had no effect in prolonging the survival of RT1Aa disparate grafts despite the complete absence of CD8+ cells from the graft infiltrate, which included numerous CD4+ T cells and macrophages. RT1u, but not RT1c, recipients mounted a strong alloantibody response against RT1Aa disparate kidneys. Immune serum obtained from RT1u recipients that had rejected a RT1Aa disparate graft was able, when injected into cyclosporin-treated RT1u recipients, to restore their ability to reject a RT1Aa, but not a third-party RT1c, kidney. These results suggest that CD8+ cells in general and CD8+ cytotoxic effector cells in particular are unnecessary for the rapid rejection of RT1Aa class I disparate kidney grafts by high responder RT1u recipients. By implication, CD4+ T cells alone are sufficient to cause prompt rejection of such grafts and they may do so by providing T cell help for the generation of alloantibody.

Animals↗