Thermal Fixation of Swine Liver Tissue after Magnetic Resonance-Guided High-Intensity Focused Ultrasound Ablation

The aim of this study was to investigate experimental conditions for efficient and controlled in vivo liver tissue ablation by magnetic resonance (MR)-guided high-intensity focused ultrasound (HIFU) in a swine model, with the ultimate goal of improving clinical treatment outcome. Histological changes were examined both acutely (four animals) and 1 wk after treatment (five animals). Effects of acoustic power and multiple sonication cycles were investigated. There was good correlation between target size and observed ablation size by thermal dose calculation, post-procedural MR imaging and histopathology, when temperature at the focal point was kept below 90°C. Structural histopathology investigations revealed tissue thermal fixation in ablated regions. In the presence of cavitation, mechanical tissue destruction occurred, resulting in an ablation larger than the target. Complete extra-corporeal MR-guided HIFU ablation in the liver is feasible using high acoustic power. Nearby large vessels were preserved, which makes MR-guided HIFU promising for the ablation of liver tumors adjacent to large veins.     

Gender Specific Sympathetic and Hemorrheological Responses to Mental Stress in Healthy Young Subjects

Objective - Activation of the sympathetic nervous system may increase hematocrit (Hct), whole blood viscosity (WBV), and possibly cardiovascular risk. The aim was to study gender specific differences of mental stress on sympathetic reactivity and blood rheology. Methods - Responses in blood pressure, heart rate (HR), Hct, WBV (Bohlin rotational viscosimeter), and plasma catecholamines to a mental arithmetic stress test (MST) were measured in male ( n = 10, 23 &#45 3 years, BMI 23 &#45 2 kg/m2) and female ( n = 10, 21 &#45 4 years, BMI 24 &#45 2 kg/m2) students. Results - Systolic blood pressure (SBP), diastolic blood pressure (DBP), and HR increased during MST in men and women, and declined to baseline levels after 15 min of recovery. In men, plasma adrenaline increased by 217% during MST ( p < 0.01, ANOVA), and plasma noradrenaline increased by 68% ( p < 0.05). Hct and WBV at low shear rates (0.5 and 1.1 l/s) increased as well ( p < 0.01, p < 0.05, and p < 0.05, respectively). In women, the increase in plasma adrenaline averaged 118% during MST ( p < 0.05) while plasma noradrenaline (-3%, p = 0.38), Hct, and WBV at all shear rates remained unchanged. Men and women differed in &#106 adrenaline ( p < 0.05), &#106 noradrenaline ( p = 0.01), &#106 Hct ( p < 0.05), and &#106 WBV ( p < 0.05). &#106 Hct tended to correlate with &#106 SBP ( r = 0.60, p = 0.07), &#106 DBP ( r = 0.57, p = 0.09), and &#106 HR ( r = 0.50, p = 0.14), and correlated significantly with &#106 noradrenaline ( r = 0.66, p < 0.05) in men only. Multiple regression analysis showed that gender independently explained 22% of the change in Hct during mental stress. Conclusion - Data suggest gender specific differences in sympathetic and hemorrheological responses to mental stress in healthy young subjects. In men, sympathetic responses were related to hemorrheological responses, but not in women. It may be speculated whether such differences in stress responses may contribute to lower cardiovascular risk in premenopausal women than in men.     

Clinical reasoning processes: unravelling complexity through graphical representation

Medical Education 2012: 46 : 454–463 Context Clinical reasoning is a core skill in medical practice, but remains notoriously difficult for students to grasp and teachers to nurture. To date, an accepted model that adequately captures the complexity of clinical reasoning processes does not exist. Knowledge‐modelling software such as mot Plus (Modelling using Typified Objects [MOT]) may be exploited to generate models capable of unravelling some of this complexity. Objectives This study was designed to create a comprehensive generic model of clinical reasoning processes that is intended for use by teachers and learners, and to provide data on the validity of the model. METHODS  Using a participatory action research method and the established modelling software (mot Plus), knowledge was extracted and entered into the model by a cognitician in a series of encounters with a group of experienced clinicians over more than 250 contact hours. The model was then refined through an iterative validation process involving the same group of doctors, after which other groups of clinicians were asked to solve a clinical problem involving simulated patients. Results A hierarchical model depicting the multifaceted processes of clinical reasoning was produced. Validation rounds suggested generalisability across disciplines and situations. Conclusions The MOT model of clinical reasoning processes has potentially important applications for use within undergraduate and graduate medical curricula to inform teaching, learning and assessment. Specifically, it could be used to support curricular development because it can help to identify opportune moments for learning specific elements of clinical reasoning. It could also be used to precisely identify and remediate reasoning errors in students, residents and practising doctors with persistent difficulties in clinical reasoning.     

Seed size influence on germination responses to light and temperature of seven pioneer tree species from the Central Amazon

In Amazon secondary forests are dominated by pioneer species that typically produce large amounts of small and dormant seeds that are able to form a persistent soil seed bank. Seed dormancy in this group of species is overcome by environmental conditions found in open areas, such as high irradiation or alternating temperatures. Nevertheless, a variety of germination responses to environmental factors is known among pioneers; some of them may germinate in diffuse light or in darkness condition at constant temperature. Seed mass can be considered as one of the factors that promotes this variety. Regarding species with very small seeds, it seems that the trigger for germination is light and for larger seeds temperature alternation may be a more important stimulus. In this study we established a relationship between seed mass and germination response to light and alternating temperature for a group of seven woody pioneer species from the Amazon forest. We found that an increase in seed mass was followed by a decrease in the need for light and an increase in the tolerance to alternating temperatures. Understanding germination strategies may contribute with the knowledge of species coexistence in high diverse environments and also may assist those involved in forest management and restoration.     

Protective effect of low-grade hypothermia in experimental skeletal muscle ischemia.

In the present study, a rat hindlimb tourniquet model was used to investigate the effect of moderate hypothermia on ischemic muscle necrosis. Complete circulatory arrest was maintained for 4.5 h. During the ischemic period the animals were kept in an infant incubator at different temperatures. After 72 h survival the percentage of necrosis in the anterior tibial muscle was measured morphometrically on histological slides. At an ambient temperature of 24 degrees C there was 80% necrosis in the anterior tibial muscle. At 22 degrees C the necrosis was reduced to 29%. This reduction corresponds to more than 30 min shortening of the ischemia time. Differences in tissue temperature may explain some of the discrepancies reported in tolerance limits for muscle ischemia. To achieve consistent results in experimental muscle ischemia, it is necessary to control the ambient temperature.     

Atherosclerotic carotid disease in asymptomatic individuals

The carotid bifurcation was studied histologically in 53 consecutive autopsies from persons over 65 years of age who were asymptomatic for carotid artery disease and showed no carotid related brain infarcts. The autopsy material is considered to be representative for the population in Oslo. The area stenosis was determined morphometrically in histological sections and the cases were examined for the occurrence of atherosclerotic plaques, calcifications, plaque hemorrhages, ulcerations, and mural thrombi. About one half of the cases had more than 50% stenosis. There was increasing frequency of plaque hemorrhages, ulcerations and mural thrombi with increasing stenosis. When the stenosis exceeded 60%, most cases had small recent and old plaque hemorrhages and one half had ulcerations and mural thrombi. In addition, numerous healed ulcerations and organized thrombi were seen. It is concluded that plaque complications are frequent in cases with stenosis and that most of them apparently heal without giving rise to symptoms. The presence of such lesions in asymptomatic cases must therefore be interpreted with caution.     

Evaluation of aging in place model with home care services and registered nurse care coordination in senior housing

A state-sponsored evaluation of aging in place (AIP) as an alternative to assisted living and nursing home has been underway in Missouri. Cost, physical, and mental health assessment data reveal the cost-effectiveness and positive health measures of AIP. Findings of the first four years of the AIP evaluation of two long-term care settings in Missouri with registered nurse care coordination are compared with national data for traditional long-term care. The combined care and housing cost for any resident who received care services beyond base services of AIP and who qualified for nursing home care has never approached or exceeded the cost of nursing home care at either location. Both mental health and physical health measures indicate the health restoration and independence effectiveness of the AIP model for long-term care.