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Liebschner M.A.K.,Baylor College of Medicine | Liebschner M.A.K.,Research Service Line | Wettergreen M.,Caroline Collective
Methods in Molecular Biology | Year: 2012

The goal of this area of research is to manipulate the pore space of scaffolds through the application of an intelligent design concept on dissolvable microparticles. To accomplish this goal, we developed an efficient and repeatable process for fabrication of microparticles from multiple materials using a combination of rapid prototyping (RP) and soft lithography. Phase changed 3D printing was used to create masters for PDMS molds. A photocrosslinkable polymer was then delivered into these molds to make geometrically complex 3D microparticles. This repeatable process has demonstrated to generate the objects with greater than 95% repeatability with complete pattern transfer. This process was illustrated for three different shapes of various complexities. The shapes were based on the extrusion of 2D shapes. This may allow simplification of the fabrication process in the future combined with a direct transfer of the findings. Altering the shapes of particles used for porous scaffold fabrication will allow for tailoring of the pore shapes, and therefore their biological function within a porous tissue engineering scaffold. Through permeation experiments, we have shown that the pore geometry may alter the permeability coefficient of scaffolds while influencing mechanical properties to a lesser extent. By selecting different porogen shapes, the nutrition transport and scaffold degradation can be significantly influenced with minimal effect on the mechanical integrity of the construct. In addition, the different shapes may allow a control of drug release by modifying their surface-to-volume ratio, which could modulate drug delivery over time. While soft lithography is currently used with photolithography, its high precision is offset by high cost of production. The employment of RP to a specific resolution offers a much less expensive alternative with increased throughput due to the speed of current RP systems. © 2012 Springer Science+Business Media, LLC. Source

Ahmed O.,University of Arizona | Parthasarathy S.,Research Service Line | Parthasarathy S.,University of Arizona
Sleep Medicine Clinics | Year: 2010

Positive airway pressure therapy (PAP) is a commonly prescribed treatment for obstructive sleep apnea (OSA). Traditionally, a sleep technician determined the optimal pressure for treatment of sleep-disordered breathing (SDB) through manual titration of the device during polysomnography. However, alternative methods for determination of optimal PAP, such as autotitrating PAP (APAP), have seen tremendous growth over the past decade. The purpose of this article is to improve understanding of the currently available alternative methods for titration of PAP in patients with SDB with special emphasis on OSA. Recent prospective randomized studies of alternative methods of titration suggest that pressure determinations made by these devices are comparable to traditional manual titrations made in the sleep laboratory. Obstacles to the adoption of these alternative modes of titration into daily practice may be attributable to issues surrounding appropriate patient selection, differences between devices, reimbursement policies of third-party payors, consensus among sleep experts, and individual physicians' practice patterns and volumes. Although newer generations and types of APAP devices are entering the sleep field constantly, providers' knowledge and time availability remain limiting factors. Tremendous growth is occurring in technology and scientific evidence supporting alternative modes of PAP titration for SDB, but barriers to implementation remain. © 2010 Elsevier Inc. All rights reserved. Source

Park J.,Emory University | Park J.,Research Service Line | Middlekauff H.R.,University of California at Los Angeles
Autonomic Neuroscience: Basic and Clinical | Year: 2015

Abnormal neurocirculatory control during exercise is one important mechanism leading to exercise intolerance in patients with both end-stage renal disease (ESRD) and earlier stages of chronic kidney disease (CKD). This review will provide an overview of mechanisms underlying abnormal neurocirculatory and hemodynamic responses to exercise in patients with kidney disease. Recent studies have shown that ESRD and CKD patients have an exaggerated increase in blood pressure (BP) during both isometric and rhythmic exercise. Subsequent studies examining the role of the exercise pressor reflex in the augmented pressor response revealed that muscle sympathetic nerve activity (MSNA) was not augmented during exercise in these patients, and metaboreflex-mediated increases in MSNA were blunted, while mechanoreflex-mediated increases were preserved under basal conditions. However, normalizing the augmented BP response during exercise via infusion of nitroprusside (NTP), and thereby equalizing baroreflex-mediated suppression of MSNA, an important modulator of the final hemodynamic response to exercise, revealed that CKD patients had an exaggerated increase in MSNA during isometric and rhythmic exercise. In addition, mechanoreflex-mediated control was augmented, and metaboreceptor blunting was no longer apparent in CKD patients with baroreflex normalization. Factors leading to mechanoreceptor sensitization, and other mechanisms underlying the exaggerated exercise pressor response, such as impaired functional sympatholysis, should be investigated in future studies. © 2014. Source

Budhiraja R.,Southern Arizona Veterans Affairs Health Care System SAVAHCS | Budhiraja R.,University of Arizona | Parthasarathy S.,Southern Arizona Veterans Affairs Health Care System SAVAHCS | Parthasarathy S.,University of Arizona | And 8 more authors.
Sleep | Year: 2012

Study Objectives: Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality and may frequently be associated with sleep disturbances. However, the correlates of insomnia in COPD patients have not been well characterized. The aim of the current study was to describe the prevalence of insomnia disorder in COPD and to elucidate the demographic and clinical characteristics of COPD patients that are associated with insomnia. Design: Cross-sectional study. Setting: Clinic-based sample from an academic hospital. Participants: Patients with stable COPD. Measurements: An interviewer-conducted survey was administered to 183 participants with COPD. Seventy-two of these participants (30 with and 42 without insomnia) maintained a sleep diary and underwent actigraphy for 7 days. Results: Insomnia (chronic sleep disturbance associated with impaired daytime functioning) was present in 27.3% of participants. Current tobacco users (odds ratio (OR), 2.13) and those with frequent sadness/anxiety (OR, 3.57) had higher odds, but oxygen use was associated with lower odds (OR, 0.35) of insomnia. Patients with insomnia had worse quality of life and a higher prevalence of daytime sleepiness. Actigraphy revealed shorter sleep duration and lower sleep efficiency, and a sleep diary revealed worse self-reported sleep quality in participants with insomnia. Conclusion: Insomnia disorder is highly prevalent in patients with COPD; current tobacco use and sadness/anxiety are associated with a higher prevalence, and oxygen use with a lower prevalence of insomnia; patients with insomnia have poorer quality of life and increased daytime sleepiness; and insomnia is associated with worse objective sleep quality. Source

Park J.,Emory University | Park J.,Research Service Line | Lyles R.H.,Emory University | Bauer-Wu S.,University of Virginia
American Journal of Physiology - Regulatory Integrative and Comparative Physiology | Year: 2014

Mindfulness meditation (MM) is a stress-reduction technique that may have real biological effects on hemodynamics but has never previously been tested in chronic kidney disease (CKD) patients. In addition, the mechanisms underlying the potential blood pressure (BP)-lowering effects of MM are unknown. We sought to determine whether MM acutely lowers BP in CKD patients, and whether these hemodynamic changes are mediated by a reduction in sympathetic nerve activity. In 15 hypertensive African-American (AA) males with CKD, we conducted a randomized, crossover study in which participants underwent 14 min of MM or 14 min of BP education (control intervention) during two separate random-order study visits. Muscle sympathetic nerve activity (MSNA), beat-to-beat arterial BP, heart rate (HR), and respiratory rate (RR) were continuously measured at baseline and during each intervention. A subset had a third study visit to undergo controlled breathing (CB) to determine whether a reduction in RR alone was sufficient in exacting hemodynamic changes. We observed a significantly greater reduction in systolic BP, diastolic BP, mean arterial pressure, and HR, as well as a significantly greater reduction in MSNA, during MM compared with the control intervention. Participants had a significantly lower RR during MM; however, in contrast to MM, CB alone did not reduce BP, HR, or MSNA. MM acutely lowers BP and HR in AA males with hypertensive CKD, and these hemodynamic effects may be mediated by a reduction in sympathetic nerve activity. RR is significantly lower during MM, but CB alone without concomitant meditation does not acutely alter hemodynamics or sympathetic activity in CKD. © 2014 the American Physiological Society. Source

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