Biomedical subjects

Robert Walker

Publications and source records attributed to Robert Walker.

At least 19 recordsLinked to original sources

PubMed2006

Prevalence of opioid analgesic injection among rural nonmedical opioid analgesic users.

OBJECTIVE: The purpose of this study was to examine the prevalence and correlates of opioid analgesic injection (OAI) in a cohort of rural opioid analgesic users. METHODS: Cross-sectional study of 184 participants from rural Appalachian Kentucky. RESULTS: The majority of participants were male (54.9%), white (98.4%) and the median age was 30 years (interquartile range: 24-37). The self-reported lifetime prevalence of injection drug use (IDU) was 44.3%, with 35.3% of respondents reporting injection of oral opioid analgesic formulations. The prevalence of self-reported hepatitis C (HCV) was 14.8%, significantly greater than those not injecting opioid analgesics (1.7%) (p<0.001). Receptive needle sharing, distributive needle sharing and sharing of other injection paraphernalia was reported by 10.5%, 26.3%, and 42.1% of those currently injecting, respectively. CONCLUSIONS: Opioid analgesic injection was more prevalent in this rural population than has been found in previous reports. This study suggests a rising problem with injecting among rural opioid users, a problem more typically associated with urban drug users. Educating injectors of opioid analgesics on safe needle practices is necessary in order to curb the transmission of HIV, HCV, and other infectious diseases. Further study on the longitudinal course of opioid analgesic injection in this population appears warranted.

Adult↗

PubMed2006

Evolution of brain size and juvenile periods in primates.

This paper assesses selective pressures that shaped primate life histories, with particular attention to the evolution of longer juvenile periods and increased brain sizes. We evaluate the effects of social complexity (as indexed by group size) and foraging complexity (as indexed by percent fruit and seeds in the diet) on the length of the juvenile period, brain size, and brain ratios (neocortex and executive brain ratios) while controlling for positive covariance among body size, life span, and home range. Results support strong components of diet, life span, and population density acting on juvenile periods and of home range acting on relative brain sizes. Social-complexity arguments for the evolution of primate intelligence are compelling given strong positive correlations between brain ratios and group size while controlling for potential confounding variables. We conclude that both social and ecological components acting at variable intensities in different primate clades are important for understanding variation in primate life histories.

Age Factors↗

PubMed2006

Energetic demand of multiple dependents and the evolution of slow human growth.

This study investigates the consequences of the human foraging niche and multiple dependent offspring on the optimal growth trajectory of humans. We test the hypothesis that the human pattern of slow human growth between age at weaning and puberty helps defer the compound energetic demand on parents with multiple dependents, by using growth and demographic data from two foraging societies, the Ache of eastern Paraguay and the Dobe Ju/'hoansi of Botswana and Namibia. We run simulations of observed and potential growth trajectories among sub-adults and their consequent energetic demands on parents given profiles of fertility, mortality, consumption and production. We find that either sub-adult production or food subsidies from other people must substantially increase in order to compensate for the dramatic increase in energetic demand on parents if offspring were to grow faster at younger ages. Our conclusion is that slow human growth followed by a rapid adolescent growth spurt may have facilitated rising human fertility rates and greater investments in neural capital.

Adolescent↗

PubMed2006

Cardiovascular morbidity and mortality in the Atherosclerosis and Folic Acid Supplementation Trial (ASFAST) in chronic renal failure: a multicenter, randomized, controlled trial.

OBJECTIVES: The Atherosclerosis and Folic Acid Supplementation Trial (ASFAST) aimed to establish whether high-dose folic acid would slow the progression of atherosclerosis and reduce cardiovascular events in patients with chronic renal failure (CRF). BACKGROUND: Hyperhomocysteinemia is a potential contributor to the high rates of cardiovascular morbidity and mortality in patients with CRF. METHODS: A total of 315 subjects with CRF, mean age 57 years (range 24 to 79 years) were randomized to 15 mg folic acid daily or placebo and followed for a median of 3.6 years. The primary intima-media thickness (IMT) and clinical end points were: rate of progression of mean maximum carotid IMT and a composite of myocardial infarction (MI), stroke, and cardiovascular death. Secondary end points included all cardiovascular events and change in pulse wave velocity, systemic arterial compliance and augmentation index. Data were analyzed by intention-to-treat. RESULTS: Plasma total homocysteine was reduced by 19% in the folic acid group. There was no significant difference between the treatment groups in rate of change of IMT or any measure of artery function. Seventy-seven events occurred in the folic acid group (14.9 per 100 patient-years) as compared with 86 in the placebo group (16.3 per 100 patient-years). The rates of the primary and secondary clinical end points at five years were not significantly different after adjustment for baseline differences between the groups (adjusted hazard ratio for MI, stroke, and cardiovascular death: 0.98 [95% confidence interval: 0.66 to 1.47]; p = 0.94; for all cardiovascular events: 0.95 [95% confidence interval: 0.69 to 1.30]; p = 0.75). CONCLUSIONS: High-dose folic acid does not slow atheroma progression or improve cardiovascular morbidity or mortality in patients with CRF.

Adult↗

PubMed2006

CNS gene therapy applications of the Semliki Forest virus 1 vector are limited by neurotoxicity.

The Semliki Forest virus (SFV) 1 vector system is highly efficient at gene transduction in a broad range of host cells, including neurons. To determine the potential of SFV1-based vectors to mediate gene expression in substantia nigra neurons, we inoculated d1EGFP-expressing SFV virus-like particles stereotaxically into the mouse brain. This system selectively and extensively mediated gene expression in dopaminergic neurons of the substantia nigra. Continual reporter gene expression was evident in neuronal cell bodies for up to 3 weeks postinoculation and d1EGFP-positive neuronal processes were apparent for 12 weeks. There was no evidence of an apoptotic response to infection, but with time cell degeneration and an axonopathy, indicative of neuronal loss, were increasingly apparent. This system has potential for experimental studies requiring efficient transient gene transduction of mouse CNS neurons. The current SFV1 vector system is, however, limited in its potential for CNS gene therapy by neurotoxicity.

Animals↗

PubMed2006

Life in the slow lane revisited: ontogenetic separation between chimpanzees and humans.

This study investigates the evolution of human growth by analyzing differences in body mass growth trajectories among three populations: the Ache of eastern Paraguay, the US (NHANES, 1999-2000), and captive chimpanzees. The relative growth statistic "A" from the mammalian growth law is allowed to vary with age and proves useful for comparing growth across different ages, populations, and species. We demonstrate ontogenetic separation between chimpanzees and humans, and show that interspecific differences are robust to variable environmental conditions. The human pattern of slow growth during the lengthened period from weaning to the beginning of the adolescent growth spurt is found among the Ache (low energy availability and high disease load) and also in the US (high energy availability and low disease load). The human growth pattern contrasts with that of the chimpanzee, where absolute growth rates and relative "A" values are faster and less prolonged. We suggest that selection has acted to decrease human growth rates to allow more time for increased cognitive development with lower body-maintenance costs.

Animals↗

PubMed2006

Ethicians, ethicists and the goals of clinical ethics consultation.

We believe that clinical ethics consultation (CEC) has as its goal the delivery of healthcare in a manner consistent with the moral rules and the moral ideals. Towards this end, CEC pursues the instrumental ends of clarifying the limits of acceptable ethical disagreement and facilitating a choice among ethically acceptable alternatives. In pursuing these ends, healthcare ethics consultation (HEC) and CEC services confront three broad categories of questions: (1) questions of professional duty; (2) questions of law; and (3) questions of general morality. Professional duty questions concern what has been referred to as the "internal morality of medicine", and include questions such as the medical legitimacy of the goal(s) being pursued, or the acceptability of the means being employed. Questions of law concern themselves with what the law requires, permits or prohibits. Questions of general morality include all those not falling within the scope of the above categories. We submit that this has implications for the organization and structure of consultation services and HEC and for the methodology and processes employed in CEC. Thus: (1) questions of professional duty should be addressed only by physician members (whom we would distinguish by employing the term "ethicians") of the HEC or CEC service. The only role for non-ethicians under these circumstances would be in helping to resolve disagreements between/among professionals; (2) questions of law, in contrast, should be addressed only by the attorney member(s) of the HEC or CEC service; (3) questions of general morality may be addressed by the entire membership of the HEC or CEC service.

Consultants↗

PubMed2006

Beyond medical futility: a proposed taxonomy of ultra vires acts in medicine.

When is a physician's act non-medical, and how might such non-medical acts be classified? One approach, analogous to the substantive due process inquiry employed by American courts weighing the constitutionality of legislative acts, would involve consideration of the following questions: 1) Is a legitimate medical goal being pursued? 2) Are the means being employed legitimately medical? 3) Are the goals and means appropriately related? Accordingly, a physician acts medically when employing legitimate and appropriate medical means in pursuit of a legitimate medical goal. In contrast, when the goals pursued or means employed are not legitimately medical, or when the two are not appropriately related, the act is medically ultra vires ("beyond the powers")--that is, an act beyond the physician's power or authority--and consequently non-medical. Medically ultra vires acts may be further sub-classified depending upon which prong of the above trident is defective. Where the goal of the act, though achievable, is not legitimately medical, the act is medically ultra vires because of goal illegitimacy, or medically ultra fines ("beyond the ends"). Where the means employed are not legitimately medical, the act is medically ultra vires because of means illegitimacy, or medically ultra modos ("beyond the means"). Where the means and goals are not appropriately related, the act is medically ultra vires because of means-goals disjunction, or medically ultra nexus ("beyond the connection"). Medical futility (where the medical goal in question, albeit legitimate, cannot be achieved by the act under consideration) represents the paradigmatic example of the latter.

Classification↗

PubMed2006

Image, imagination, and reality: on effectiveness of introductory work with vocalists.

Fifty-four sung tokens, each consisting of eight images were generated with the help of magnetic resonance imaging (MRI) technique to demonstrate the work of intrapharyngeal muscles when singing and speaking, and to help the educational process. The MRI images can be used as a part of a visualization feed-back method in vocal education and contribute to creation of proper mental images. The use of visualization (pictures, drafts, graphs, spectra, MRI images, etc.), along with mental images, facilitates simplification and acceleration of the process of understanding and learning how to master the basics of vocal technique, especially in the initial period of study. It is shown that work on muscle development and use of imagination should progress with close interaction between the two. For higher effectiveness and tangible results, mental images used by a vocal pedagogue should correspond to the technical and emotional level of a student. Therefore, mental images have to undertake the same evolution as articulation technique-from simplified and comprehensible to complex and abstract. Our integrated approach suggests continuing the work on muscle development and use of imagination in singing classes, employing the experience of voice-speech teachers. Their exercises are modified using the empirical method and other techniques developed creatively by singing teachers. In this method, sensitivity towards the state of the tissues becomes increasingly refined; students acquire a conscious control over the muscle work, students gain full awareness of both sensation and muscle activity. As a result, a complex of professional conditioned reflexes is being developed. A case study of the New Zealand experience was conducted with groups of Maori and European students. Unique properties and trends in the voices of Maori people are discussed.

Humans↗

PubMed2006

Adverse impact of a history of violence for women with breast, cervical, endometrial, or ovarian cancer.

OBJECTIVE: The experience of physical and sexual violence (victimization) is common among U.S. women and is associated with adverse health consequences. The study objectives were to estimate the prevalence of victimization in women with cancer and to examine associations with demographics, cancer screening, and cancer stage. METHODS: From 2004 to 2005, 101 women with breast, cervical, endometrial, or ovarian cancer were interviewed to collect demographics, cancer screening history, health care access/use, and violence history. Chi-square and Fisher exact tests were used test risk-factor associations. A multinomial logistic regression model was used for multivariable analysis. RESULTS: The prevalence of a history of violence was 48.5% (49/101 women), and within that group, 46.9% (23/49) had a positive childhood violence screen, 75.5% (37/49) had a positive adult screen, and 55% (27/49) reported sexual violence at any age. Women with a positive violence screen differed significantly from women with a negative screen in that they were younger (P = .031), more often divorced (P = .012), more likely to smoke (P = .010), more often lacked commercial insurance (P = .036), and had more advanced stage of disease (P = .013), but they did not differ with regard to race, cancer type, education level, alcohol or drug use, or cancer screening compliance. Multivariable analysis revealed that only stage remained significant; women with a history of violence had a 2.6-fold increased chance of diagnosis in later stages (odds ratio 2.61, 95% confidence interval 1.03-6.59). CONCLUSION: A history of violence in breast, ovarian, endometrial, and ovarian cancer patients was extremely common and correlated with advanced stage at diagnosis. LEVEL OF EVIDENCE: II-2.

Breast Neoplasms↗

PubMed2006

Trends in controlled-release oxycodone (OxyContin) prescribing among Medicaid recipients in Kentucky, 1998-2002.

CONTEXT: Prescription opioid abuse has emerged as a public health problem, particularly in rural America. PURPOSE: To examine temporal and geographic trends in rates of controlled-release oxycodone (OxyContin) prescribing for Kentucky Medicaid recipients. METHODS: A cross-sectional analysis was completed in which the state was divided into 3 regions (distressed Appalachia, Appalachia, and other Kentucky), and data from Medicaid pharmacy claims from 1998 to 2002 were analyzed. Claims were further stratified by disability status. FINDINGS: Temporary Assistance for Needy Families Medicaid recipients in distressed Appalachia were more likely than those in other Kentucky regions to file controlled-release oxycodone claims in 1999, 2001, and 2002. Even after adjusting for the proportion of Temporary Assistance for Needy Families recipients in each region, the distressed region still had significantly higher rates (P< .05) than the non-Appalachian region of controlled-release oxycodone prescription claims among Temporary Assistance for Needy Families recipients. Similar findings were observed for disabled Medicaid recipients in 2002. CONCLUSIONS: Higher rates of claims for controlled-release oxycodone in the distressed Appalachian region of Kentucky suggest that economic and health factors unique to this area may be contributing to increased use of this product. The increased availability of controlled-release oxycodone in distressed Appalachian regions may facilitate abuse.

Analgesics, Opioid↗

PubMed2006

Police attitudes toward domestic violence offenders.

Police attitudes are important in facilitating a sense of safety and comfort in women seeking justice-system support for protection from partner violence. This study examined police attitudes toward sanctions and treatment for domestic violence offenders compared with other violent and nonviolent offenders. In addition, police attitudes toward domestic violence offenders who do and do not use substances were examined. Officers from one city police department (n = 315) participated in a survey. Results indicate there is a trend toward attitudes that treatment, rather than sanctions, was more appropriate for domestic violence offenders. In addition, officers rated the use of sanctions higher for domestic violence offenders who abuse alcohol or drugs compared with domestic violence offenders who did not abuse alcohol or drugs. Understanding police attitudes toward domestic violence offenders may have implications for police training and victim services in facilitating the use of the justice system in protecting women from partner violence.

Adult↗

PubMed2006

The impact of differential patterns of physical violence and stalking on mental health and help-seeking among women with protective orders.

This study examined the severity of partner violence on women's mental health and help-seeking as well as perceptions of safety and protective-order effectiveness. Three groups based on partner violence victimization in the past year were compared: (a) women who reported experiencing moderate physical violence but no history of severe violence or stalking (n = 102), (b) women who experienced severe violence but no history of stalking (n = 142), and (c) women who experienced severe violence and stalking (n = 145). Results suggest that stalking has a unique impact on victims' mental health and perceived safety, and that protections afforded by protective orders may not be adequate for women experiencing stalking.

Adult↗

PubMed2006

Protective orders: questions and conundrums.

Current media portrayal of protective orders is often negative, focusing on weaknesses in how protective orders are obtained and enforced. This review of research findings on protective orders examines issues and suggests areas in need of future research to clarify and improve public policy. More specifically, this review has five main objectives: (a) to provide background information about partner violence and the need for protective orders; (b) to describe what protective orders are, how many women obtain them, and the advantages and disadvantages of obtaining protective orders; (c) to examine characteristics of women who seek protective orders; (d) to explore research on whether protective orders actually increase women's safety; and (e) to highlight opportunities and gaps in the practice and research literature regarding the use of protective orders for women with violent partners or ex-partners.

Battered Women↗

PubMed2006

Victim service and justice system representative responses about partner stalking: what do professionals recommend?

Research suggests that partner stalking is associated with reassault and lethality as well as increased psychological distress for victims. However, there is a significant gap in information about stalking interventions and the responses of health, mental health, law enforcement, social services, and criminal justice professionals to women experiencing partner stalking. The purpose of this study is to examine the ideas about appropriate and effective responses to stalking victims from professionals in victim services and the justice system. The study also examined differences among rural and urban representatives because prior studies have shown significant differences between rural and urban areas on experiences and responses to partner violence. A total of 152 key informants (38 urban and 114 rural) were interviewed. Study results suggest a need for more training for victim services and justice system professionals on stalking and service needs of women who experience stalking in the context of partner violence.

Adult↗

PubMed2005

Narrow band fiber-optic phase-shifted Fabry-Perot Bragg grating filters for atmospheric water vapor lidar measurements.

A unique ultranarrowband fiber-optic phase-shifted Fabry-Perot Bragg grating filter for atmospheric water vapor lidar measurements was designed, fabricated, and successfully tested. Customized optical fiber Bragg gratings were fabricated so that two transmission filter peaks occurred: one (89% transmission, 8 pm FWHM) near the 946-nm water vapor absorption line and the other peak (80% transmission, 4 pm FWHM) at a region of no absorption. Both transmission peaks were within a 2.66-nm stop band. Demonstration of tension tuning to the 946.0003-nm water vapor line was achieved, and the performance characterization of custom-made optical fiber Bragg grating filters are presented. These measurements are successfully compared to theoretical calculations using a piecewise-matrix form of the coupled-mode equations.

Journal Article↗

PubMed2005

Pharmacology of the fluoroquinolones: a perspective for the use in domestic animals.

The fluoroquinolones are a class of compounds that comprise a large and expanding group of synthetic antimicrobial agents. Structurally, all fluoroquinolones contain a fluorine molecule at the 6-position of the basic quinolone nucleus. Despite the basic similarity in the core structure of these molecules, their physicochemical properties, pharmacokinetic characteristics and microbial activities can vary markedly across compounds. The first of the fluoroquinolones approved for use in animals, enrofloxacin, was approved in the late 1980s. Since then, five other fluoroquinolones have been marketed for use in animals in the United States, with others currently under investigation. This review focuses on the use of fluoroquinolones within veterinary medicine, providing an overview of the structure-activity relationship of the various members of the group, the clinical uses of fluoroquinolones in veterinary medicine, their pharmacokinetics and potential interspecies differences, an overview of the current understanding of the pharmacokinetic/pharmacodynamic relationships associated with fluoroquinolones, a summary of toxicities that have been associated with this class of compounds, their use in both in human and veterinary species, mechanisms associated with the development of microbial resistance to the fluoroquinolones, and a discussion of fluoroquinolone dose optimization. Although the review contains a large body of basic research information, it is intended that the contents of this review have relevance to both the research scientist and the veterinary medical practitioner.

Animal Diseases↗

PubMed2005

Id4 is required for the correct timing of neural differentiation.

Complex intrinsic and extrinsic mechanisms determine neural cell fate during development of the nervous system. Using Id4 deficient mice, we show that Id4 is required for normal development of the central nervous system (CNS), timing neural differentiation in the developing forebrain. In the absence of Id4, the ventricular zone of the neocortex, future hippocampus as well as lateral and medial ganglionic eminences exhibited a 20-30% reduction in mitotic neural precursor cells (NPCs). Although the number of apoptotic cells was significantly increased, the neocortex of Id4(-/-) embryos was consistently thicker due to premature neuronal differentiation, which resulted in an increase in early-born neurons in the adult Id4(-/-) cortex. Late-born cortical neurons and astrocytes in the cortex, septum, hippocampus and caudate putamen of Id4(-/-) adult brains were decreased, however, likely due to the depletion of the NPC pool. Consequently, adult Id4(-/-) brains were smaller and exhibited enlarged ventricles. In vitro analysis of neurosphere cultures revealed that proliferation of Id4-deficient NPCs was impaired and that BMP2-mediated astrocyte differentiation was accelerated in the absence of Id4. Together, these in vivo and in vitro data suggest a crucial role for Id4 in regulating NPC proliferation and differentiation.

Animals↗