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Biomedical subjects

David Hartley

Publications and source records attributed to David Hartley.

13 recordsLinked to original sources
PubMed2005

A multi-species epidemic model with spatial dynamics.

A model is formulated that describes the spatial propagation of a disease that can be transmitted between multiple species. The spatial component consists, for each species, of a certain number of patches that make up the vertices of a digraph, the arcs of which represent the movement of the various species between the patches. In each of the patches and for each species, a susceptible-exposed-infectious-recovered (SEIR) epidemic model describes the evolution of the disease status of individuals. Also in each patch, there is transmission of the disease from species to species. An analysis of the system is given, beginning with results on the mobility component. A formula is derived for the computation of the basic reproduction number R(0) for sspecies and npatches, which then determines the global stability properties of the disease free equilibrium. Simulations for the spread of a disease in one species and two patches are presented.

Animals↗
PubMed2005

The post-auricular muscle response: an objective electrophysiological method for evaluating hearing sensitivity.

Post-auricular muscle responses (PAMRs) were recorded in sixteen adults with normal hearing and twenty adults with sensorineural hearing loss. Click stimuli were presented at 20 to 80 dB nHL via insert earphones. Only one ear was tested in hearing-impaired subjects, but normal-hearing subjects were tested monaurally and binaurally. PAMR amplitudes declined and latencies increased with decreasing click intensity. Both binaural stimulation and eye turn enhanced the PAMR. In hearing-impaired subjects, PAMR thresholds were correlated with audiometric thresholds for the eyes-turned condition. All normal-hearing subjects had PAMR when recording conditions were optimized and half had responses for the least optimal condition (20 dB nHL, monaural, eyes front). With eyes turned and monaural clicks at 35 dB nHL, the level widely used for infant hearing screening, most normal-hearing adults had a PAMR. Thus the PAMR is a robust response that may be a useful adjunct to ABR for objective hearing assessment.

Adolescent↗
PubMed2004

Identification of 1,5-naphthyridine derivatives as a novel series of potent and selective TGF-beta type I receptor inhibitors.

Optimization of the screening hit 1 led to the identification of novel 1,5-naphthyridine aminothiazole and pyrazole derivatives, which are potent and selective inhibitors of the transforming growth factor-beta type I receptor, ALK5. Compounds 15 and 19, which inhibited ALK5 autophosphorylation with IC50 = 6 and 4 nM, respectively, showed potent activities in both binding and cellular assays and exhibited selectivity over p38 mitogen-activated protein kinase. The X-ray crystal structure of 19 in complex with human ALK5 is described, confirming the binding mode proposed from docking studies.

Activin Receptors, Type I↗
PubMed2004

Mood changes after cognitive testing in late middle-age: impacts of sex and habitual alcohol consumption.

Men and women (50-67 years) completed drinking diaries and, on the basis of this, were divided into low (<2 units/day, 1 UK unit=8 g alcohol) and moderate (2-5 units/day) alcohol groups. They completed analogue rating scales of mood and bodily symptoms before and after two extended computerised cognitive tests. After the tests, the women showed significantly greater increases in self-ratings on the factors of anxiety and discontentment and felt significantly less alert than did the men. They also showed significantly greater increases in bodily symptoms of somatic anxiety and ratings of aggressive mood than did the men. There were no significant effects of alcohol or Sex x Alcohol interactions on the self-ratings, but the men showed significant positive correlations of alcohol and negative mood. On both the cognitive tests, there were significant Sex x Alcohol interactions because the moderate-drinking men performed worse than the low-drinking men, whereas the moderate-drinking women performed better than the low-drinking women. Thus, the middle-aged women responded much more than did the men with negative mood changes to the psychological stress of cognitive testing, although their cognitive performance was not worse.

Affect↗
PubMed2004

In situ stent-graft fenestration to preserve the left subclavian artery.

PURPOSE: To report our first clinical application of a new technique for in situ fenestration of a thoracic stent-graft. CASE REPORT: After completing a series of in vitro and in vivo experiments, in situ stent-graft fenestration was employed during endograft repair of a saccular thoracic aortic aneurysm in a 77-year-old woman. Because the stent-graft would have covered the left subclavian artery ostium, a modified Zenith TX1 thoracic stent-graft was deployed then fenestrated transluminally using a guidewire followed by serial cutting balloons, which created a fenestration over the LSA sufficiently large to accommodate a Jomed covered stent on an 8-mm balloon. Completion angiography showed exclusion of the aneurysm and brisk flow into the LSA. Following the procedure, the arm pressures were nearly equal. The 6-month CT scan showed no endoleak and a patent subclavian artery stent. CONCLUSIONS: In situ graft fenestration to preserve the left subclavian artery after deliberate coverage during endovascular repair of a thoracic aortic aneurysm appears feasible in this initial clinical application. There are uncertainties regarding the long-term stability of the fabric tears that are an inherent part of this technique.

Aged↗
PubMed2004

Rural health disparities, population health, and rural culture.

In this commentary, I place the maturing field of rural health research and policy in the context of the rural health disparities documented in Health United States, 2001, Urban and Rural Health Chartbook. Because of recent advances in our understanding of the determinants of health, the field must branch out from its traditional focus on access to health care services toward initiatives that are based on models of population health. In addition to presenting distinct regional differences, the chartbook shows a pattern of risky health behaviors among rural populations that suggest a "rural culture" health determinant. This pattern suggests that there may be environmental and cultural factors unique to towns, regions, or United States Department of Agriculture (USDA) economic types that affect health behavior and health.

Cultural Characteristics↗
PubMed2003

Medicaid managed behavioral health in rural areas.

As of 2000, 21 states had implemented Medicaid managed behavioral health (MMBH) programs for a significant portion of their rural population. It is not clear how MMBH programs may work in rural areas since they are primarily designed to control mental health utilization. In rural areas the challenge is often to enhance service delivery, not to reduce it. MMBH programs may also affect important features of rural delivery systems, including access to care and coordination of primary care and specialty mental health providers. This article describes the implementation of MMBH programs in rural areas based on an inventory of states implementing MMBH programs in rural counties conducted between June 1999 and June 2000. The experience of MMBH programs in rural areas is also described based on case studies conducted in six states. All 21 states included the general Medicaid population (Temporary Assistance for Needy Families); 17 states included special Medicaid populations (adults with serious and persistent mental illness and children with serious emotional disturbances). Slightly less than half the states integrated (carved-in) behavioral health with physical health services in serving the general Medicaid population; only one state integrated these services for the special Medicaid population. Access to mental health care in rural areas had generally not been restricted. MMBH had little impact on the linkage between primary care and mental health. Local Managed Behavioral Health Organizations, formed by public sector entities and providers, played an increasingly important role in the evolution of MMBH.

Adult↗
PubMed2003

Small town health care safety nets: report on a pilot study.

CONTEXT: Very little is known about the health care safety net in small towns, especially in towns where there is no publicly subsidized safety-net health care. PURPOSE: This pilot study of the primary care safety net in 7 such communities was conducted to start building knowledge about the rural safety net. METHODS: Interviews were conducted and secondary data collected to assess the community need for safety-net care, the health care safety-net role of public officials, and the availability of safety-net care at private primary care practices and its financial impact on these practices. FINDINGS: An estimated 20% to 40% of the people in these communities were inadequately insured and needed access to affordable health care, and private primary care practices in most towns played an important role in making primary care available to them. Most of the physician practices were owned or subsidized by a hospital or regional network, though not explicitly to provide charity care. It is likely this ownership or support enabled the practices to sustain a higher level of charity care than would have been possible otherwise. In the majority of communities studied, the leading public officials played no role in ensuring access to safety-net care. CONCLUSIONS: State and national government policy makers should consider subsidy programs for private primary care practices that attempt to meet the needs of the inadequately insured in the many rural communities where no publicly subsidized primary safety-net care is available. Subsidies should be directed to physicians in primary care shortage areas who provide safety-net care; this will improve safety-net access and, at the same time, improve physician retention by bolstering physician incomes. Options include enhanced Medicare physician bonuses and grants or tax credits to support income-related sliding fee scales.

Health Policy↗
PubMed2003

Follow-up after endovascular aortic aneurysm repair: the plain radiograph has an essential role in surveillance.

Periodic follow-up is mandatory for patients with aortic stent-grafts. Central to surveillance is the establishment of a baseline against which changes can be detected. Computed tomography (CT) has been the benchmark of follow-up imaging for endografts, but comparison of serial AP and lateral plain radiographs will detect structural alterations that can be missed on CT scans. In this review, we illustrate these common endograft complications and the value of plain radiographs in their detection. We believe that the plain radiograph should be the cornerstone of aortic endograft surveillance. However, a standardized protocol should be used to avoid parallax and positioning errors that affect interpretation.

Aortic Aneurysm, Abdominal↗
PubMed2003

Retrograde fenestration of endoluminal grafts from target vessels: feasibility, technique, and potential usage.

PURPOSE: To report initial experiments involving a new method for percutaneous intraprocedural stent-graft fenestration from the target vessel. TECHNIQUE: In bench and canine models, the fabric of an implanted Zenith endograft was punctured easily using the stiff end of a coronary 0.014-inch guidewire delivered through the target vessel (e.g., renal or iliac artery). A 20-G cutting needle was passed over the coronary wire to enlarge the puncture site, followed by a cutting balloon to create a fenestration that was of sufficient size to allow deployment of a stent. CONCLUSIONS: In vivo endograft fenestration of a Zenith endograft is feasible. In addition to providing a percutaneous means of intentionally fenestrating a stent-graft from the artery to be perfused, the technique has potential application as a bailout maneuver after inadvertent side branch occlusion. Although the time to achieve successful fenestration in the experimental model was long, refinement may achieve performance times adequate to maintain viability of the end organ.

Animals↗
PubMed2002

Role of mTOR in the degradation of IRS-1: regulation of PP2A activity.

We have investigated the role of PI 3-kinase and mTOR in the degradation of IRS-1 induced by insulin. Inhibition of mTOR with rapamycin resulted in approximately 50% inhibition of the insulin-induced degradation of IRS-1. In contrast, inhibition of PI-3 kinase, an upstream activator of mTOR, leads to a complete block of the insulin-induced degradation. Inhibition of either PI-3 kinase or mTOR prevented the mobility shift in IRS-1 in response to insulin, a shift that is caused by Ser/Thr phosphorylation. These results indicate that insulin stimulates PI 3-kinase-mediated degradation of IRS-1 via both mTOR-dependent and -independent pathways. Platelet-derived growth factor (PDGF) stimulation leads to a lower level of degradation, but significant phosphorylation of IRS-1. Both the degradation and phosphorylation of IRS-1 in response to PDGF are completely inhibited by rapamycin, suggesting that PDGF stimulates IRS-1 degradation principally via the mTOR-dependent pathway. Inhibition of the serine/threonine phosphatase PP2A with okadaic acid also induced the phosphorylation and degradation of IRS-1. IRS-1 phosphorylation and degradation in response to okadaic acid were not inhibited by rapamycin, suggesting that the action of mTOR in the degradation of IRS-1 results from inhibition of PP2A. Consistent with this, treatment of cells with rapamycin stimulated PP2A activity. While the role of mTOR in the phosphorylation of IRS-1 appears to proceed primarily through the regulation of PP2A, we also provide evidence that the regulation of p70S6 kinase phosphorylation requires the direct activity of mTOR.

3T3 Cells↗
PubMed2002

Behavioral health: setting the rural health research agenda.

This article seeks to identify current research priorities in the area of rural behavioral health. The method for accomplishing this task begins by identifying several domains where policy has a potential to effect improvements in access or quality but has been hampered by lack of empirical knowledge. In each domain a synthesis of current research summarizes what is known and draws attention to knowledge gaps. Research questions in each domain are proposed. The policy domains are theoretically based, using a conceptual model of access to health care, with a focus on illness level (prevalence), enabling factors (the delivery system, organization and financing, the promise of telemedicine), and predisposing factors (special populations, beliefs, values, stigma).

Behavioral Medicine↗