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PubMed2005

Ferromagnetism in Ga(1-x)Mn(x)P: evidence for inter-Mn exchange mediated by localized holes within a detached impurity band.

We report an energy gap for hole photoexcitation in ferromagnetic Ga(1-x)Mn(x)P that is tunable by Mn concentration (x < or = 0.06) and by compensation with Te donors. For x approximately 0.06, electrical transport is dominated by excitation across this gap above the Curie temperature (TC) of 60 K and by thermally activated hopping below TC. Magnetization measurements reveal a moment of 3.9 +/- 0.4 muB per substitutional Mn while the large anomalous Hall signal demonstrates that the ferromagnetism is carrier mediated. In aggregate these data indicate that ferromagnetic exchange is mediated by holes localized in a Mn-derived band that is detached from the valence band.

Journal Article↗

PubMed2005

Mutagenic analysis of the nucleation propensity of oxidized Alzheimer's beta-amyloid peptide.

The formation of polypeptide aggregates represents a nucleated polymerization reaction in which an initial nucleation event (lag phase) is followed by the extension of newly formed nuclei into larger aggregates, including fibrils (growth phase). The efficiencies of these reactions relate to the lag time (lag phase) and to the rate of aggregation (growth phase), which can be determined from experimental aggregation curves. Here we present a mutagenic analysis in which we replace valine 18 of the Alzheimer's Abeta (1-40) peptide with 17 different amino acids and determine its effect on the lag time, and therefore, on the propensity of nucleation. Comparison with various physico-chemical properties shows that nucleation is affected in a predictable manner depending on the beta-sheet propensity and hydrophobicity of residue 18. In addition, we observe a direct proportionality between the lag time and the rate of aggregation. These data imply that the two reactions, nucleation and polymerization, are governed by very similar physicochemical principles and that they involve the formation of the same types of noncovalent interactions.

Amyloid beta-Peptides↗

PubMed2003

The effect of capitation on switching primary care physicians.

OBJECTIVE: To examine the relationship between patient case-mix, utilization, primary care physician (PCP) payment method, and the probability that patients switch their PCPs. DATA SOURCES/STUDY SETTING: Administrative enrollment and claims/encounter data for 1994-1995 from four physician organizations. STUDY DESIGN: We developed a conceptual model of patient switching behavior, which we used to guide the specification of multivariate logistic analyses focusing on interactions between patient case-mix, utilization, and PCP reimbursement methods. DATA COLLECTION/EXTRACTION METHODS: Claims data were aggregated to the encounter level; a switch was defined as a change in PCP since the previous encounter. The PCPs were reimbursed on either a capitated or fee-for-service (FFS) basis. PRINCIPAL FINDINGS: Patients with stable chronic conditions (Ambulatory Diagnostic Groups [ADG] 10) and capitated PCPs were 36 percent more likely to switch PCPs than similar patients with FFS PCPs, controlling for patient age and sex and physician fixed effects. When the number of previous encounters was included in the model this relationship was no longer significant. Instead high utilizers with capitated PCPs were significantly more likely to switch PCPs than were similar patients with FFS PCPs. CONCLUSIONS: A patient's demographics and utilization are associated with the probability that the patient will switch PCPs. Capitated PCP payment was associated with higher rates of switching among high utilizers of health care resources. These findings raise concerns about the continuity and quality of care experienced by vulnerable patients in an era of changing financial incentives.

Adult↗

PubMed1995

Contact sensitivity as a model for T-cell activation in skin.

Contact sensitivity has served as a useful model for the primary activation of T cells in skin and skin-associated lymphoid tissue. We have been interested in the early signals necessary for the induction of an allergen-specific T-cell response, as well as the factors controlling the intensity and extent of such an immune reaction. Because cytokines qualified as possible candidate molecules involved in directing primary immune responses in skin, we studied the early changes in the cytokine pattern of the epidermis. Apart from defining a cytokine pattern specifically induced only after application of allergen, we also identified Langerhans-cell-derived interleukin (IL)-1 beta as the first cytokine to be induced by allergen, within 15 min of hapten application. Further experiments demonstrated that IL-1 beta also subserved an essential function for the induction of contact sensitivity reactions, as injection of IL-1 beta into the ears of mice mimicked the application of contact allergen on the morphologic, phenotypic, and functional level. In addition, injection of anti-IL-1 beta monoclonal antibody before application of allergen completely prevented sensitization. We also identified the production of IL-10 by murine keratinocytes. IL-10 may serve as a counterregulatory molecule in contact hypersensitivity, as it functionally suppressed Langerhans cell accessory cell function by preventing the expression of certain costimulatory molecules on the surface of these antigen-presenting cells. Indeed, IL-10 converts those cells from potent inducers of primary immune responses to tolerizing antigen-presenting cells. The tolerizing function of IL-10 has also been described in vivo. Intradermal injection of IL-10 before application of the allergen induces hapten-specific tolerance in vivo. In aggregate, our data indicate that epidermally derived cytokines are intimately involved in the modulation of immune reactions in skin, in some cases enhancing sensitization and in others inducing specific immunologic tolerance and anergy.

Animals↗

PubMed2002

Exposure misclassification and threshold concentrations in time series analyses of air pollution health effects.

Linear, no-threshold relationships are typically reported for time series studies of air pollution and mortality. Since regulatory standards and economic valuations typically assume some threshold level, we evaluated the fundamental question of the impact of exposure misclassification on the persistence of underlying personal-level thresholds when personal data are aggregated to the population level in the assessment of exposure-response relationships. As an example, we measured personal exposures to two particle metrics, PM2.5 and sulfate (SO4(2-)), for a sample of lung disease patients and compared these with exposures estimated from ambient measurements Previous work has shown that ambient:personal correlations for PM2.5 are much lower than for SO4(2-), suggesting that ambient PM2.5 measurements misclassify exposures to PM2.5. We then developed a method by which the measured:estimated exposure relationships for these patients were used to simulate personal exposures for a larger population and then to estimate individual-level mortality risks under different threshold assumptions. These individual risks were combined to obtain the population risk of death, thereby exhibiting the prominence (and the value) of the threshold in the relationship between risk and estimated exposure. Our results indicated that for poorly classified exposures (PM2.5 in this example) population-level thresholds were apparent at lower ambient concentrations than specified common personal thresholds, while for well-classified exposures (e.g., SO4(2-)), the apparent thresholds were similar to these underlying personal thresholds. These results demonstrate that surrogate metrics that are not highly correlated with personal exposures obscure the presence of thresholds in epidemiological studies of larger populations, while exposure indicators that are highly correlated with personal exposures can accurately reflect underlying personal thresholds.

Air Pollution↗

PubMed1994

Educational audit of postgraduate medical education.

This project examined the academic audit of postgraduate medical education, and went on to research, design and implement an educational audit system for use in Mersey Region, UK. Issues found to be significant included ownership of both standards and results, norming, and the levels of aggregation of data. The project has demonstrated that designing and implementing a system of feedback which is effective and sustainable is feasible, but requires the agreement and support of tutors as to its objectives and use. The resulting system has now been tested across a range of courses and programmes of meetings in Mersey Region, and has been accepted by the Postgraduate Office as the basis for future development.

Education, Medical, Graduate↗

PubMed1996

Visits to medical practitioners in the first 6 months of life.

OBJECTIVE: To assess the use of medical practitioners' services by mothers and their babies in the 6 months following childbirth. METHODOLOGY: Aggregated Medicare data detailing medical practitioner services provided to a random sample of 650 Victorian babies born between 1 March and 31 May 1993 and their mothers were obtained from the Health Insurance Commission. This provided data on services provided between March and December of 1993 to the selected cohort. Services provided by the public hospital system to mothers and babies are not included. RESULTS: Mothers and babies in the sample used 6404 medical practitioner services in the 6 months following birth; 57% of services were to babies, 43% to mothers. Of the 6404 medical practitioner services 5042(79%) were provided by general practitioners (GP), 804(12%) by paediatricians, 319(5%) by obstetricians and 239(4%) by 'other' specialists. The mean number of visits to a GP by mothers was 3.5 and by babies was 4.2 in the 6 months following birth. General practitioners were more likely to be vocationally registered and there were differences in the item numbers charged between those who were vocationally registered and those who were not. The length of GP consultation differed significantly between mothers' and babies' visits. CONCLUSIONS: A previously undocumented level of postnatal use of medical practitioner services is presented. It suggests a significant level of postnatal maternal and infant morbidity that requires further study.

Family Practice↗

PubMed1998

Alcohol consumption and injury in Western Australia: a spatial correlation analysis using geographic information systems.

Geographic information systems technology was used to describe, in geographical terms, the nature and strength of the relationship in Western Australia between alcohol consumption and the rates of related injury: night-time assaults (10 p.m. to 6 a.m.); minor night-time road crashes (10 p.m. to 6 a.m.), weighted by traffic density; and hospital E-code (external-cause) morbidity, weighted by alcohol aetiologic fractions. The data were aggregated by five conventional state regions: northern, central, western, southern and Perth metropolitan. There was a general association, of equal significance for males and females, between estimated per capita alcohol consumption and the selected rates of injury in the five regions. However, the nature and strength of association between alcohol consumption and individual injury measures varied. Night-time assaults and hospital E-code morbidity were strongly, associated with consumption. Minor night-time crashes had only a weak association. The variation in the relationship between alcohol consumption and injury suggests that prevention strategies need to take into account the particular drinking patterns and associated harm that occur in different regions of the state, and to develop a range of targeted responses. High rates of consumption and injury in most country areas support the need for greater regional prevention efforts.

Adolescent↗

PubMed1994

Developmental change in infant cortisol and behavioral response to inoculation.

Infant cortisol and behavioral responses to receiving 1 versus 2 inoculations on 1 pediatric office visit were observed at 2 and 6 months of age. Cortisol level (pre- plus postinoculation level) decreased with age, whereas cortisol response (post- minus preinoculation level) did not vary with age when the data were aggregated over infants showing a pre- to postinoculation cortisol increase and those showing a decrease. Nonetheless, for those infants who showed a cortisol increase, cortisol level and response decreased with age. Infants quieted faster at the older age. There was a moderate relation between quieting behavior and cortisol response, at least for infants who showed a pre- to postinoculation cortisol increase. These findings indicate a developmental trend for a decline over age in adrenocortical reactivity to inoculation for infants showing a cortisol release following the perturbation. Results were comparable whether infants received 1 or 2 inoculations.

Diphtheria-Tetanus-Pertussis Vaccine↗

PubMed1992

Season of birth: issues, approaches and findings for autism.

Rates of birth in the general population show seasonal fluctuations for reasons that are ill understood. Variations from these general population patterns have been reported for several psychiatric conditions and used as the basis for aetiological hypotheses. In this paper, the evidence for alterations in the expected seasonal fluctuation in birth dates of autistic people is evaluated. A national sample of 1435 autistic individuals and a clinic sample of 196 subjects are compared to general population figures and to 121 sibling controls. Compared with the general population, the national sample showed significant deviations from the expected rate of birth by month. In the clinic sample, differences from the anticipated monthly pattern were only evident when this sample was compared to the sibling controls. A variety of models for seasonal trends, including year quarters, temperature and sine wave forms, were fitted to these variations but no consistent picture emerged.

Adolescent↗

PubMed1996

The effects of the saddle seat on seated postural control and upper-extremity movement in children with cerebral palsy.

A repeated-measures experimental cross-over study was conducted with school-aged children with spastic cerebral palsy (spastic CP) to compare the effects of flat-bench versus saddle-bench seating on postural control and reaching motions. The saddle bench allowed significantly better postural control as measured by the clinical rating scale Sitting Assessment for Children with Neuromotor Dysfunction and by a study-defined variable, Spinal Extension. No statistically significant differences were found for any other variables using aggregate data-analysis techniques. However, the group results and those of single-subject data analysis suggest that the saddle seat may help such children to develop and maintain seated postural control and upper-extremity movement patterns.

Arm↗

PubMed1993

Reliable responses to a cardiovascular reactivity protocol: a replication study in a biracial female sample.

This replication study was designed to examine the reliability of individual differences in cardiovascular responsivity to a standardized PC-based cognitive task protocol (Kamarck et al., 1992) in a female community sample. Thirty women, both black and white (ages 25-44 years), were administered the protocol twice with a 1-month retest interval using a mobile laboratory at a community-based testing site. Measures of heart rate and blood pressure reactivity were obtained comparing assessments taken at rest and during three protocol tasks. Preejection period, stroke volume, and total peripheral resistance changes were estimated using impedance cardiography assessments. As in previous studies with males, individual differences in heart rate and systolic and diastolic blood pressure responses to the protocol were highly reliable (.80 or greater) when data were aggregated across three tasks and two testing sessions. Reliability of cardiac contractility (preejection period) and stroke volume changes to these tasks exceeded .70. This reactivity assessment procedure has now produced reliable results in three studies and appears to be exportable across diverse samples and settings.

Adult↗

PubMed2006

Evaluation of the KA24 (Knowledge Access 24) service for health- and social-care staff in London and the south-east of England. Part 1: quantitative.

AIMS AND OBJECTIVES: This two-part paper aims to identify the main transferable lessons learned from both the quantitative and qualitative evaluations of the Knowledge Access 24 (KA24) service of online databases and selected full-text journals for health and social care staff in London and the south-east of England. The quantitative evaluation analysed usage rates and user registration with the objective of measuring uptake by previously disadvantaged staff, and to inform the subsequent qualitative survey. METHODS: User and usage data were analysed by type of NHS Trust, by type of user, and by what was being used. The evaluation assessed development in user registration and usage of both databases and journals over a 2-year period. Data were aggregated and analysed both monthly and quarterly. RESULTS: Usage levels increased, but uptake in both the mental health and primary care sectors was comparatively slow. Nurses and allied professionals used the service more than doctors. The increase in usage of full-text journals over the usage of databases was marked. CONCLUSIONS: Previously disadvantaged staff used electronic resources. A qualitative survey was needed to identify the main enablers and barriers to uptake.

Community Health Services↗

PubMed1991

Nursing students' attitudes towards abortion and family planning in Italy and Sweden.

In the last two decades family life and family planning have developed in a similar way in different European countries although legal and social background factors were very different in the past. Countries like Italy and Sweden are bipolar when compared. In this study nursing students' attitudes towards abortion and family planning in Italy and Sweden are described, to identify general characteristics of students that could be of interest to compare and to identify reasons for approval and/or disapproval of abortion. Some social characteristics of the students are similar, like fathers' profession/activity. Italian nursing students are more religious. Some factual knowledge is low in both samples. The nursing student's feelings, attitudes towards abortion are expressed differently in the countries. Many Italian students believe abortion is justified only on medical grounds, Swedish students indicate psychological effects as the most likely consequence both for woman and for man.

Abortion, Induced↗

PubMed2004

The impact of S-CHIP enrollment on physician participation in Medicaid in Alabama and Georgia.

OBJECTIVE: To assess whether increasing enrollment in State Children's Health Insurance Programs (S-CHIPs) has an impact on the number of office physicians participating in Medicaid and the extent of their participation. Effects are measured for a freestanding S-CHIP program with an open provider panel and an S-CHIP program that uses the state's Medicaid provider panel. DATA SOURCES: Children's Medicaid claims data for primary care services were used to measure physician participation in the program; census and enrollment data were used to describe market area characteristics. Study Design. This is a time series study of communities in two states, measuring physician Medicaid participation quarterly between 1998 and 2001, controlling for changes in community characteristics and children's program enrollment as well as other factors by quarter. DATA COLLECTION/EXTRACTION: Office physician participation is measured by practice site. Claims data are aggregated to the level of the community and reflect the number of limited practice sites, the ratio of Medicaid office sites to the number of primary care physicians in the community as reported by the American Medical Association (AMA), and the mean number of Medicaid office visits made to physician sites in the community in the quarter. FINDINGS: In Alabama, the state with a freestanding S-CHIP program, there is little association between increased S-CHIP enrollment and physician participation in Medicaid. In Georgia, where the same provider network serves both programs, increases in S-CHIP enrollment are associated with a decline in office-based physician participation in Medicaid in urban areas. CONCLUSION: Linkage of S-CHIP and Medicaid programs through the use of the same provider network, in the absence of market conditions that encourage the expansion of the network, can lead to a negative impact on access for Medicaid enrollees.

Adolescent↗

PubMed1995

Gender differences in risk perception: effects differ in stressed vs. non-stressed environments.

Contrary to previous reports that women are more concerned about environmental risks than men, we hypothesized that men and women residing in neighborhoods stressed by multiple hazards would demonstrate similar concerns about local environmental conditions. Analysis of a national data base and an aggregate of ten local data bases found greater female than male concern about local technological, behavioral, and land use hazards in good neighborhoods, but, as expected, not in stressed ones. We urge analysts to conduct more studies in stressed neighborhoods in order to better understand the perspective of those who live with environmental risks.

Adult↗

PubMed2002

Patients, nurses, and physicians have differing views of quality of critical care.

PURPOSE: To compare patient, nurse, and physician assessments of quality of care and patient satisfaction in selected critical care units. DESIGN: As part of a study of patient outcomes from critical care, data were collected between December 1991 and March 1993 from 489 patients, 518 nurses, and 515 physicians in 25 critical care units located in 14 hospitals in the U.S. Pacific Northwest. METHODS: Views of patient satisfaction and quality of care were measured using standardized instruments. All data were aggregated to the unit level (N = 25) and were normalized to a common scale for analysis. FINDINGS: Physicians rated quality of care higher than did either patients or nurses within the same critical care unit, and nurses had the lowest perceptions of quality. Nurses and patients had similar views of patient satisfaction, but physicians tended to overestimate patients' satisfaction. However, physicians', nurses', and patients' scores varied considerably within and between units. Physicians' and nurses' views of quality and patient satisfaction were strongly related to processes such as MD-RN collaboration and outcomes such as nurses' job satisfaction. CONCLUSIONS: Patients, nurses, and physicians viewed quality of care and patient satisfaction differently. Nurses' and physicians' perspectives were more related to their views of the work environment than to organizational factors, patient characteristics, or commonly used outcome measures.

Attitude↗

PubMed2006

Cholesterol, statins and tau.

Many of the known risk factors for Alzheimer's disease (AD) are associated with cholesterol metabolism. Interestingly, it seems as if higher doses of statins, i.e. inhibitors of the cholesterol biosynthesis by blocking formation of mevalonate, might lower the progression of AD. The mechanisms, however, by which statins or cholesterol levels exert their influence are unknown. A hereditary cholesterol-storage disorder, Niemann Pick C, shows Alzheimer-like tau-pathology in youth or adolescence but with no amyloid plaques. This gives rise to the possibility that disturbances in cholesterol metabolism induce changes in tau without interposition of Abeta-protein aggregates. Experimental data suggest that manipulation of cholesterol levels may lead to changes in tau phosphorylation. These changes vary depending on how cholesterol metabolism is manipulated. Effects seem to be either mild and transient, or drastic and related to neurodegeneration, or independent of the mevalonate pathway.

Alzheimer Disease↗