Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

No description available.

Faculty of Health Sciences, Degree of Master of Science in Medicine. 9208366a / The initiation of new bone formation within the porous spaces of hydroxyapatite (HA) implants involves the expression of osteogenic markers belonging to the TGF-β superfamily. To study the genetic expression of these osteogenic markers in relation to the type of HA implant used and implantation period, five different types of porous HA biomaterials were implanted in the rectus abdominis muscles of adult baboons Papio ursinus, and were harvested at two, three and 12 months. The total RNA of all harvested samples was extracted and analysed using the Northern blot technique. The results showed that Collagen type IV, GDF-10 and BMP-7 were expressed at the early time points at relatively high levels, and their expression levels were significantly reduced at 12 months. The expression of these makers was not affected by the type of porous HA implant used. The histological sections of these specimens at two and three months showed vascularised connective tissue within the porous spaces of the implants with no bone formation. However, at 12 months there were substantial amounts of bone formed in all the studied implants. The down-regulation of the expressed osteogenic markers at 12 months correlates to the amount of bone formed, suggesting some negative feedback mechanism which may be acting via inhibitory Smads proteins in relation to the amount of bone formed. Neither TGF-β1 nor BMP-3 messages were detected in any of the studied samples, It is possible that these bone markers are not expressed locally within the vicinity of the porous HA implants but are adsorbed to the HA implants from the circulatory system.

Heart failure (HF) is a common cause of hospitalisation and mortality across industrialised countries. The number of hospitalisations and deaths attributed to heart failure is increasing, and this trend is predicted to continue. Numerical and in-vitro simulations of the human cardiovascular system constitute the basic tools for enhancing diagnostic and therapeutic technologies for HF and this would in turn, have significant effects on morbidity,mortality, and healthcare expenditure. Mechanical Circulatory Support (MCS) as a destination therapy for HF is rising significantly as it provides a cost-effective alternative to long-term treatment and cardiac transplantation. However, long-term versatility is far from ideal and incidence of transient and permanent neurological events is still high. To this end, evolution of MCS devices calls for more sophisticated design and evaluation methods. The purpose of this work is to develop a numerical model and to implemented a novel in-vitro model of the cardiovascular system with the intention of evaluating the performance characteristics of a purposely selected centrifugal pump impeller for the treatment of both Class III and IV HF conditions when placed in series with the heart at two different anatomic locations: Ascending Aorta and Descending Aorta. An existing lumped-parameter model of the CV system, that included models for the heart, the pulmonary and the systemic circulatory loops by adapting a modified version of the fourth-element Windkessel model was enhanced by dividing the systemic circulation into six parallel vascular beds, and by including an autoregulatory system to control both pressures and volumes throughout the system. As part of the novelty of the present work, a volume reflex loop was included with the purpose of simulating volume overload conditions, as commonly found in HF conditions, and obtaining a more realistic analysis of volume displacement, while using a MCS device. The in-vitro model implemented in this work adopted most of the features included in the mathematical counterpart with the purpose of validating the numerical results. As a result of the combination of models and proper optimisation of the system parameters, predictions of pathophysiological trends and MCS usage are satisfactorily obtained. The models implemented in this work offer a valuable tool for the selection and performance evaluation of MCS devices for the treatment of HF conditions.

No description available.

No description available.

No description available.

Abstract Retrograde cerebral perfusion (RCP) techniques have been adopted in aortic arch surgery for clinical use. The clear benefits of RCP are that it reduces embolic injury and prolongs the permissible period of hypothermic circulatory arrest (HCA). At the same time, however, there is a great deal of evidence according to which RCP may be associated with an increased risk of fluid sequestration and cerebral edema. In the current study intermittent RCP was compared with continuous RCP and HCA alone to clarify if periodical RCP decreases fluid sequestration (I). HCA is an effective method of cerebral protection, but is associated with long cardiopulmonary bypass times, and coagulation disturbances. We tested the hypothesis that deep hypothermic RCP could improve cerebral outcome during moderate HCA (II and III). Glutamate excitotoxicity plays an important role in the development of ischemic brain injury. The purpose of the present study was to determine the efficacy of lamotrigine, a Na+ channel blocker, to mitigate cerebral injury after HCA (IV). A chronic porcine model was used in the present series of studies. Hemodynamic, electrophysiologic, and metabolic monitoring were performed until four hours after the instigation of rewarming. S-100β was measured up to 20 hours. Daily behavioral assessment performed until death or elective sacrifice on the seventh postoperative day. After continuous RCP the median fluid sequestration volume was 145 (0–250) ml compared with -50 (-100 - 0) ml after intermittent RCP (p = 0.04). In comparison of 15°C RCP to HCA alone during moderate 25°C hypothermia, 5/6 animals in the RCP group survived seven days compared with 2/6 in the HCA group (p = 0.04). The total histopathologic scores in the RCP(15°C) group were lower than those for the RCP(25°C) group during moderate 25°C hypothermia (p = 0.04). EEG bursts were recovered better in the RCP(15°C) group at 3 hours after the start of rewarming compared to HCA group (p = 0.05). The rate of EEG burst recovery was higher in lamotrigine treated animals compared to placebo treated animals after 4 hours during the rewarming (p = 0.02). Among the animals that survived for 7 days, the median behavioral score was higher in the lamotrigine group (8) compared with controls (7) (p = 0.02). The results indicate that intermittent RCP decreases the rate of fluid sequestration after continuous RCP. The cold RCP at moderate systemic hypothermia seems to provide a better neurological outcome than that with moderate temperature RCP, a finding suggesting that enhanced cranial hypothermia is the major beneficial factor of RCP. The Na+ channel blocker lamotrigine improves neurological outcome after a prolonged period of HCA. In conclusion, two refinements in the RCP concept are to administer it at low temperatures and if longer periods of perfusion are necessary, RCP should be applied intermittently.

The purpose of this thesis investigation was to evaluate the effects of combined aerobic and weightlifting training on the circulatory responses of patients with coronary artery disease (CAD) during formal lifting, and during strength related activities of daily living. Seven subjects (x age: 54 years) successfully completed 20 sessions of training within 12 weeks. The aerobic training regimen consisted of a 5-10 minute warm up, walking, arm buoys, and arm-and leg-cycling at an intensity equivalent to approximately 70% of functional capacity. The weightlifting regimen consisted of single-arm curl (SAC), and single-leg press (SLP) exercises performed by both limbs, in addition to modified trunk curls. Before and after training, intra-brachial artery pressure was measured continuously during: 10 repetitions of the seated SAC exercise at 70% of the subject's one repetition maximum (1 RM), 12 repetitions of the SLP and double-leg press (DLP) exercises at 80% of 1 RM, isometric handgrip at 50% of maximal voluntary contraction strength, 10 flights of stair climbing at a cadence of 60 steps/minute, and 10 minutes of horizontal treadmill walking at 3.5 mph. Training increased the SAC, SLP, and DLP 1 RM strength by 98% (15 vs 30 kg; p < 0.016), 23% (99 vs 122 kg; p < 0.002), and 27% (165 vs 210 kg; p < 0.001) respectively. The mean peak systolic, diastolic, and mean arterial pressures, heart rate and rate pressure product were attenuated in all 3 weightlifting exercises when subjects lifted the same absolute load (70% of the pre-training 1 RM for the SAC exercise, and 80% of the pre-training 1 RM for the SLP and DLP exercises) after training. When subjects lifted the same relative load after training, all circulatory responses increased. The average peak heart rate and arterial pressure responses were reduced during 10 minutes of horizontal treadmill walking after training. In contrast, there was little or no reduction in any of the measured parameters during stair climbing. It is concluded that weightlifting training in CAD patients results in an attenuation of the heart rate and arterial blood pressure responses during repeated lifting with identical absolute loads, and there may be a modest transfer of this effect to certain activities of daily living involving the trained muscles. / Thesis / Master of Science (MS)