Engineering Commons^™

A Device For Noninvasive Assessment Of Vascular Impairment Risk In The Lower Extremity, Michael J. Hoffmann, Paul E. Knudson, M. Barbara Silver-Thorn

Biomedical Engineering Faculty Research and Publications

The repeatability and resolution of the clinical gold standard of vascular assessment, the ankle-brachial index (ABI), was compared to that of a new device that dynamically assesses tissue perfusion during external loading utilizing laser Doppler flowmetry. Eight subjects of varying levels of vascular impairment were tested in successive weeks using two different sites on the subject's posterior calf. These new measures included the perfusion decrease as well as the unloading delay during cyclic loading. Some new dynamic tissue perfusion measures demonstrated comparable levels of reproducibility with the ABI (e.g., 10%-20%). Only the unloading delay showed potentially enhanced resolution over ABI …

Enhanced Na+/H+ Exchange During Ischemia And Reperfusion Impairs Mitochondrial Bioenergetics And Myocardial Function, Mohammed Aldakkak, David F. Stowe, James S. Heisner, Marisha Spence, Amadou K.S. Camara

Biomedical Engineering Faculty Research and Publications

Inhibition of Na+/H+ exchange (NHE) during ischemia reduces cardiac injury due to reduced reverse mode Na+/Ca2+ exchange. We hypothesized that activating NHE-1 at buffer pH 8 during ischemia increases mitochondrial oxidation, Ca2+ overload, and reactive O2 species (ROS) levels and worsens functional recovery in isolated hearts and that NHE inhibition reverses these effects. Guinea pig hearts were perfused with buffer at pH 7.4 (control) or pH 8 +/- NHE inhibitor eniporide for 10 minutes before and for 10 minutes after 35- minute ischemia and then for 110 minutes with pH 7.4 buffer alone. Mitochondrial NADH and FAD, [Ca2+], and superoxide …

Low-Flow Perfusion Of Guinea Pig Isolated Hearts With 26°C Air-Saturated Lifor Solution For 20 Hours Preserves Function And Metabolism, David F. Stowe, Amadou K.S. Camara, James S. Heisner, Mohammed Aldakkak, David R. Harder

Biomedical Engineering Faculty Research and Publications

Background

Donor human hearts cannot be preserved for >5 hours between explantation and recipient implantation. A better approach is needed to preserve transplantable hearts for longer periods, ideally at ambient conditions for transport. We tested whether Lifor solution could satisfactorily preserve guinea pig isolated hearts perfused at low flow with no added oxygen at room temperature for 20 hours.

Methods

Hearts were isolated from 18 guinea pigs and perfused initially with oxygenated Krebs–Ringer (KR) solution at 37°C. Hearts were then perfused with recirculated Lifor or cardioplegia (CP) solution (K⁺ 15 mmol/liter) equilibrated with room air at 20% of control …

Irradiation Of Varying Volumes Of Rat Lung To Same Mean Lung Dose: A Little To A Lot Or A Lot To A Little?, Vladimir A. Semenenko, Robert C. Molthen, Chunrong Li, Natalya V. Morrow, Rongshan Li, Swarajit N. Ghosh, Meetha Medhora, X. Allen Li

Biomedical Engineering Faculty Research and Publications

Purpose: To investigate whether irradiating small lung volumes with a large dose or irradiating large lung volumes with a small dose, given the same mean lung dose (MLD), has a different effect on pulmonary function in laboratory animals.

Methods and Materials: WAG/Rij/MCW male rats were exposed to single fractions of 300 kVp X-rays. Four treatments, in decreasing order of irradiated lung volume, were administered: (1) whole lung irradiation, (2) right lung irradiation, (3) left lung irradiation, and (4) irradiation of a small lung volume with four narrow beams. The irradiation times were chosen to accumulate the same MLD of 10, …

Biomechanical And Radiographic Evaluation Of An Ovine Model For The Human Lumbar Spine, Nina E. Easley, M. Wang, Linda M. Mcgrady, Jeffrey M. Toth

Biomedical Engineering Faculty Research and Publications

While various species of animal models have been used in preclinical investigations of spinal implant devices to assess their biological adaptation and biomechanical performance, few studies have made comprehensive comparisons to validate their suitability of modelling the human spine. The purpose of this study was to assess essential biomechanical behaviours and disc morphology of the ovine lumbar model. Flexibility testing was conducted on the spines (L3—L4 and L4—L5) of nine skeletally matured sheep. Segmental rotation and intradiscal pressure were measured and load sharing between the intervertebral disc and posterior elements were calculated on the basis of a simplified parallel spring …

Bronchial Circulation Angiogenesis In The Rat Quantified With Spect And Micro-Ct, Christian Wieholt, David L. Roerig, John B. Gordon, Steven Thomas Haworth, Robert C. Molthen, Anne V. Clough

Biomedical Engineering Faculty Research and Publications

Introduction

As pulmonary artery obstruction results in proliferation of the bronchial circulation in a variety of species, we investigated this angiogenic response using single photon emission computed tomography (SPECT) and micro-CT.

Materials and methods

After surgical ligation of the left pulmonary artery of rats, they were imaged at 10, 20, or 40 days post-ligation. Before imaging, technetium-labeled macroaggregated albumin (^99mTc MAA) was injected into the aortic arch (IA) labeling the systemic circulation. SPECT/micro-CT imaging was performed, the image volumes were registered, and activity in the left lung via the bronchial circulation was used as a marker of bronchial …

Contributions Of Online Visual Feedback To The Learning And Generalization Of Novel Finger Coordination Patterns, Xiaolin Liu, Robert A. Scheidt

Biomedical Engineering Faculty Research and Publications

We explored how people learn new ways to move objects through space using neuromuscular control signals having more degrees of freedom than needed to unambiguously specify object location. Subjects wore an instrumented glove that recorded finger motions. A linear transformation matrix projected joint angle signals (a high-dimensional control vector) onto a two-dimensional cursor position on a video monitor. We assessed how visual information influences learning and generalization of novel finger coordination patterns as subjects practiced using hand gestures to manipulate cursor location. Three groups of test subjects practiced moving a visible cursor between different sets of screen targets. The hand-to-screen …

Katp Channel Openers Have Opposite Effects On Mitochondrial Respiration Under Different Energetic Conditions, Matthias L. Riess, Amadou K.S. Camara, André Heinen, Janis T. Eells, Michele M. Henry, David F. Stowe

Biomedical Engineering Faculty Research and Publications

Mitochondrial (m) K_ATP channel opening has been implicated in triggering cardiac preconditioning. Its consequence on mitochondrial respiration, however, remains unclear. We investigated the effects of two different K_ATP channel openers and antagonists on mitochondrial respiration under two different energetic conditions. Oxygen consumption was measured for complex I (pyruvate/malate) or complex II (succinate with rotenone) substrates in mitochondria from fresh guinea pig hearts. One of two mK_ATP channel openers, pinacidil or diazoxide, was given before adenosine diphosphate in the absence or presence of an mK_ATP channel antagonist, glibenclamide or 5-hydroxydecanoate. Without ATP synthase inhibition, both mK_{ATP …}

Bioresorbable Polylactide Interbody Implants In An Ovine Anterior Cervical Discectomy And Fusion Model: Three-Year Results, Kevin A. Thomas, Jeffrey M. Toth, Neil R. Crawford, Howard Seim, Lewis L. Shi, Mitchel B. Harris, Anthony S. Turner

Biomedical Engineering Faculty Research and Publications

Study Design.

In vivo study of anterior discectomy and fusion using a bioresorbable 70:30 poly(l-lactide-co-d,l-lactide) interbody implant in an ovine model.

Objective.

To evaluate the efficacy of the polylactide implant to function as an interbody fusion device, and to assess the tissue reaction to the material during the resorption process.

Summary of Background Data.

The use of polylactide as a cervical interbody implant has several potential advantages when compared with traditional materials. Having an elastic modulus very similar to bone minimizes the potential for stress shielding, and as the material resorbs additional loading is transferred to the developing fusion mass. …

An Effect Of Relative Motion On Trajectory Discrimination, Scott A. Beardsley, Lucia M. Vaina

Biomedical Engineering Faculty Research and Publications

Psychophysical studies point to the existence of specialized mechanisms sensitive to the relative motion between an object and its background. Such mechanisms would seem ideal for the motion-based segmentation of objects; however, their properties and role in processing the visual scene remain unclear. Here we examine the contribution of relative motion mechanisms to the processing of object trajectory. In a series of four psychophysical experiments we examine systematically the effects of relative direction and speed differences on the perceived trajectory of an object against a moving background. We show that background motion systematically influences the discrimination of object direction. …

Leg Sympathetic Response To Noxious Skin Stimuli Is Similar In High And Low Level Human Spinal Cord Injury, M. Kevin Garrison, Alexander V. Ng, Brian D. Schmit

Biomedical Engineering Faculty Research and Publications

Objective

To determine if sympathetically mediated vasoconstriction in the lower extremities is injury level dependent. Although sympathetic responses have been measured in the limbs of people with high and low level SCI using blood flow measurements, including Doppler ultrasound and venous plethysmography, a direct comparison between injury levels has not been made.

Methods

Volunteers with chronic SCI were grouped according to injury level. Above T6: high level (HL, n = 7), and T6 and below: low level (LL, n = 6). All subjects had complete motor and sensory loss. Leg arterial flows were recorded by venous occlusion plethysmography, and continuous …

Mineral Trioxide Aggregate Material Use In Endodontic Treatment: A Review Of The Literature, Howard W. Roberts, Jeffrey M. Toth, David W. Berzins, David G. Charlton

Biomedical Engineering Faculty Research and Publications

Objective

The purpose of this paper was to review the composition, properties, biocompatibility, and the clinical results involving the use of mineral trioxide aggregate (MTA) materials in endodontic treatment.

Methods

Electronic search of scientific papers from January 1990 to August 2006 was accomplished using PubMed and Scopus search engines (search terms: MTA, GMTA, WMTA, mineral AND trioxide AND aggregate).

Results

Selected exclusion criteria resulted in 156 citations from the scientific, peer-reviewed dental literature. MTA materials are derived from a Portland cement parent compound and have been demonstrated to be biocompatible endodontic repair materials, with its biocompatible nature strongly suggested by …

Mechanical Behavior And Failure Analysis Of Prosthetic Retaining Screws After Long‐Term Use In Vivo. Part 3: Preload And Tensile Fracture Load Testing, Youssef S. Al Jabbari, Raymond Fournelle, Gerald J. Ziebert, Jeffrey M. Toth, Anthony Iacopino

Biomedical Engineering Faculty Research and Publications

Purpose: The aim of this study was to determine the preload and tensile fracture load values of prosthetic retaining screws after long‐term use in vivo compared to unused screws (controls). Additionally, the investigation addressed whether the preload and fracture load values of prosthetic retaining screws reported by the manufacturer become altered after long‐term use in vivo.

Materials and Methods: For preload testing, 10 new screws (controls) from Nobel Biocare (NB) and 73 used retaining screws [58 from NB and 15 from Sterngold (SG)] were subjected to preload testing. For tensile testing, eight controls from NB and 58 used retaining screws …

Mechanical Behavior And Failure Analysis Of Prosthetic Retaining Screws After Long‐Term Use In Vivo. Part 4: Failure Analysis Of 10 Fractured Retaining Screws Retrieved From Three Patients, Youssef S. Al Jabbari, Raymond Fournelle, Gerald J. Ziebert, Jeffrey M. Toth, Anthony Iacopino

Biomedical Engineering Faculty Research and Publications

Purpose: The aim of this study was to perform a failure analysis on fractured prosthetic retaining screws after long‐term use in vivo. Additionally, the study addresses the commonly asked question regarding whether complex repeated functional occlusal forces initiate fatigue‐type cracks in prosthetic retaining screws.

Materials and Methods: Ten fractured prosthetic retaining screws retrieved from three patients treated with fixed detachable hybrid prostheses were subjected to a failure analysis. In patients 1 and 2, the middle three retaining screws of the prostheses were found fractured at retrieval time after they had been in service for 20 and 19 months, respectively. In …

Site-Specific Effects Of Pecam-1 On Atherosclerosis In Ldl Receptor-Deficient Mice, Shikha Arora, Brian Boylan, Reema Goel, Benjamin R. Schrank, Barbara Fleming, Rose Ann Fleming, Hiroto Mirura, Peter J. Newman, Robert C. Molthen, Debra K. Newman

Biomedical Engineering Faculty Research and Publications

Objective—Atherosclerosis is a vascular disease that involves lesion formation at sites of disturbed flow under the influence of genetic and environmental factors. Endothelial expression of adhesion molecules that enable infiltration of immune cells is important for lesion development. Platelet/endothelial cell adhesion molecule-1 (PECAM-1; CD31) is an adhesion and signaling receptor expressed by many cells involved in atherosclerotic lesion development. PECAM-1 transduces signals required for proinflammatory adhesion molecule expression at atherosusceptible sites; thus, it is predicted to be proatherosclerotic. PECAM-1 also inhibits inflammatory responses, on which basis it is predicted to be atheroprotective.

Methods and Results—We evaluated herein the effect of …