Quantification of Pulmonary Arterial Wall Distensibility Using Parameters Extracted from Volumetric Micro-CT Images

Stiffening, or loss of distensibility, of arterial vessel walls is among the manifestations of a number of vascular diseases including pulmonary arterial hypertension. We are attempting to quantify the mechanical properties of vessel walls of the pulmonary arterial tree using parameters derived from high-resolution volumetric x-ray CT images of rat lungs. The pulmonary arterial trees of the excised lungs are filled with a contrast agent. The lungs are imaged with arterial pressures spanning the physiological range. Vessel segment diameters are measured from the inlet to the periphery, and distensibilities calculated from diameters as a function of pressure. The method shows promise as an adjunct to other morphometric techniques such as histology and corrosion casting. It possesses the advantages of being nondestructive, characterizing the vascular structures while the lungs are imaged rapidly and in a near-physiological state, and providing the ability to associate mechanical properties with vessel location in the intact tree hierarchy

Micro-CT Image-Derived Metrics Quantify Arterial Wall Distensibility Reduction in a Rat Model of Pulmonary Hypertension

We developed methods to quantify arterial structural and mechanical properties in excised rat lungs and applied them to investigate the distensibility decrease accompanying chronic hypoxia-induced pulmonary hypertension. Lungs of control and hypertensive (three weeks 11% O2) animals were excised and a contrast agent introduced before micro-CT imaging with a special purpose scanner. For each lung, four 3D image data sets were obtained, each at a different intra-arterial contrast agent pressure. Vessel segment diameters and lengths were measured at all levels in the arterial tree hierarchy, and these data used to generate features sensitive to distensibility changes. Results indicate that measurements obtained from 3D micro-CT images can be used to quantify vessel biomechanical properties in this rat model of pulmonary hypertension and that distensibility is reduced by exposure to chronic hypoxia. Mechanical properties can be assessed in a localized fashion and quantified in a spatially-resolved way or as a single parameter describing the tree as a whole. Micro-CT is a nondestructive way to rapidly assess structural and mechanical properties of arteries in small animal organs maintained in a physiological state. Quantitative features measured by this method may provide valuable insights into the mechanisms causing the elevated pressures in pulmonary hypertension of differing etiologies and should become increasingly valuable tools in the study of complex phenotypes in small-animal models of important diseases such as hypertension

Pulmonary arterial remodeling revealed by microfocal x-ray tomography

Animal models and micro-CT imaging are useful for understanding the functional consequences of, and identifying the genes involved in, the remodeling of vascular structures that accompanies pulmonary vascular disease. Using a micro-CT scanner to image contrast-enhanced arteries in excised lungs from fawn hooded rats (a strain genetically susceptible to hypoxia induced pulmonary hypertension), we found that portions of the pulmonary arterial tree downstream from a given diameter were morphometrically indistinguishable. This \u27self-consistency\u27 property provided a means for summarizing the pulmonary arterial tree architecture and mechanical properties using a parameter vector obtained from measurements of the contiguous set of vessel segments comprising the longest (principal) pathway and its branches over a range of vascular pressures. This parameter vector was used to characterize the pulmonary vascular remodeling that occurred in rats exposed to a hypoxic (11.5% oxygen) environment and provided the input to a hemodynamic model relating structure to function. The major effect of the remodeling was a longitudinally (pulmonary artery to arterioles) uniform decrease in vessel distensibility that resulted in a 90% increase in arterial resistance. Despite the almost uniform change in vessel distensibility, over 50% of the resistance increase was attributable to vessels with unstressed diameters less than 125 microns

Attitude and practice of health care providers towards autopsies in children under five years at Kenyatta National Hospital

Background: Attitude and practice of health care professionals toward autopsy are important as they will give information regarding factors that contribute to the low rate of autopsies in children under five years.Objective: To evaluate the attitude and practice of health care providers towards autopsies in children under five years.Design: Cross-sectional hospital based descriptive survey.Setting: General paediatrics wards and newborn unit at Kenyatta National Hospital, Nairobi, Kenya.Subjects: Health care providers working at the Kenyatta National Hospital paediatric wards and newborn unit.Results: The study enrolled 95 health care providers. Majority (69.5%) of health care providers showed a positive attitude towards autopsy. Consultants and paeadiatric residents had a more positive attitude compared to interns (p< 0.001) and nurses (p=O.Oll). Clinical experience of> 15 years was associated with a more positive attitude. The main barriers to obtaining consent were lack of formal training in obtaining consent and failure of autopsy results to be availed in a timely manner.Conclusions: Health care providers had a positive attitude to autopsy which was significantly associated with their cadre and years of experience. The main reasons given for not obtaining consent for autopsy were lack of formal training in obtaining consent and failure to obtain autopsy results in timely manner

Quantitative Models of the Rat Pulmonary Arterial Tree Morphometry Applied to Hypoxia-Induced Arterial Remodeling

Little is known about the constituent hemodynamic consequences of structural changes that occur in the pulmonary arteries during the onset and progression of pulmonary arterial remodeling. Many disease processes are known to be responsible for vascular remodeling that leads to pulmonary arterial hypertension, cor pulmonale, and death. Histology has been the primary tool for evaluating pulmonary remodeling, but it does not provide information on intact vascular structure or the vessel mechanical properties. This study is an extension of our previous work in which we developed an alternative imaging technique to evaluate pulmonary arterial structure. The lungs from Sprague-Dawley rats were removed, perfusion analysis was performed on the isolated lungs, and then an X-ray contrast agent was used to fill the arterial network for imaging. The lungs were scanned over a range of intravascular pressures by volumetric micro-computed tomography, and the arterial morphometry was mapped and measured in the reconstructed isotropic volumes. A quantitative assessment of hemodynamic, structural, and biomechanical differences between rats exposed for 21 days to hypoxia (10% O2) or normoxia (21.0% O2) was performed. One metric, the normalized distensibility of the arteries, is significantly (P \u3c 0.001) larger [0.025 ± 0.0011 (SE) mmHg−1] (n = 9) in normoxic rats compared with hypoxic [0.015 ± 0.00077 (SE) mmHg−1] (n = 9). The results of the study show that these models can be applied to the Sprague-Dawley rat data and, specifically, can be used to differentiate between the hypoxic and the control groups

Perception to Cadaver Dissection and Views on Anatomy as a Subject between Two Pioneer Cohorts in a Kenyan Medical School

Cadaver dissection has been used as the main method of teaching human anatomy for the last five centuries. There are emerging concerns on the negative consequences of cadaver dissection on medical students, leading to suggestions on use of alternative technological advancements to cadaver dissection. However, literature on medical students’ perceptions on cadaver dissection and their opinions on anatomy as a subject is scanty particularly for newly established medical schools. We provided a structured questionnaire with 17 items requiring ‘yes, no or undecided’ responses and 6 items with Likert-type questions ranging from strongly agree to strongly disagree to all preclinical students pursuing Bachelor of Medicine and Bachelor of Surgery at the new school of Medicine, Kenya Methodist University. Out of a total of 78 students, 75 correctly filled the questionnaires and were analyzed. An overwhelming majority (85.3%) found their first visit to the dissection room exciting. Most consider dissection the best method of learning anatomy, and do not support the view that it should be replaced by computer aided programs or plastic models. Despite most students indicating that they like anatomy, and find it exciting, very few are willing to take up careers as anatomists. More emphasis needs to be placed on pre-dissection training and counseling to make the experience better for students. There is need to mentor students on taking up anatomy as a career, in view of the great need for anatomists in the region.Key words: Dissection, Perceptions, Cadaver, Anatom

Abundance and Habitat Preference of the Genus Euplectes in Protected and Non protected Habitats of Jos East Plateau State, Nigeria

The knowledge on the factors influencing habitat selection is of uttermost importance because it guides the development of conservation action plan for species. Till date, there is no baseline study on the genus Euplectes in Northern Nigeria thus, an attempt to investigate the habitat preference of the genus was carried out in Amurum Forest Reserve and the nonprotected habitats of Fobur. Line transects of 200m were randomly laid across the study sites. The abundance of Bishop species was highest in farmland compared to grassland and rocky outcrop. Therefore, the number of the species was significantly different between habitats (F2, 573 = 5.454, P = 0.0015). There was a significant relationship between flock size and number of seeds across habitat types. Number of individual birds increased with increase in seed number (F1, 57 = 21687.786, P < 0.001). With the exception of grass height, there was a highly significant difference in relation to vegetation variables taken between plots where Bishop species were sighted and the random points where they were not seen (P < 0.001). The finding suggests that farmlands should be integrated into conservation plan in the nonprotected area based on the high population of the genus recorded

A Fire Severity Mapping System for Real-Time Fire Management Applications and Long-Term Planning: The FIRESEV project

Accurate, consistent, and timely fire severity maps are needed in all phases of fire management including planning, managing, and rehabilitating wildfires. The problem is that fire severity maps are commonly developed from satellite imagery that is difficult to use for planning wildfire responses before a fire has actually happened and can’t be used for real-time wildfire management because of the timing of the imagery delivery. Moreover, imagery is difficult to use for controlled fires such as prescribed burning. This study, called FIRESEV (FIRE SEVerity Mapping Tools) created a comprehensive set of tools and protocols to deliver, create, and evaluate fire severity maps for all phases of fire management. The first tool is a Severe Fire Potential Map (SFPM) that quantifies the potential for fires to burn with high severity, should they occur, for any 30m x 30m piece of ground across the western United States. This map was developed using empirical models that related topographic, vegetation, and fire weather variables to burn severity as mapped using the Monitoring Trends in Burn Severity (MTBS) digital products. This SFPM map is currently available on the Fire Research and Management Exchange System (FRAMES, http://www.frames.gov/firesev) web site and can be used to plan for future wildfires or for managing wildfires in real time, e.g. by including it as a layer in Wildland Fire Decision Support System or other GIS analysis. The next tool was the inclusion of a fire severity mapping algorithm in the Wildland Fire Assessment Tool (WFAT) developed by the National Interagency Fuels Technology Transfer (NIFTT) team. WFAT is used for fuel treatment planning to predict potential fire effects under prescribed fire weather conditions (http://www.frames.gov/partner-sites/niftt/tools/niftt-current-resources/). Now, fire severity can be mapped explicitly from fire effects simulation models (FOFEM, Consume) for real-time and planning wildfire applications. Next, the FIRESEV project showed how results from the WFAT simulated fire severity can be integrated with satellite imagery to improve fire severity mapping. And last, the FIRESEV project produced a suite of research studies, synthesis papers, and popular articles designed to improve the description, interpretation, and mapping of fire severity for wildland fire management: (1) a research study created a completely objective method of quantifying fire severity from fire effects to obtain nine unique classes of fire severity, (2) a research study comprehensively contrasted all current classifications of fire severity using Composite Burn Index (CBI) as measured on over 300 plots across the western United States to determine commonalities and differences, and (3) a synthesis paper was written discussing the problems involved in measuring, describing, and quantifying fire severity. This FIRESEV project yielded over 15 deliverables that we feel provides a comprehensive suite of products to create useful fire severity maps, along with current satellite imagery products, and also FIRESEV provides a thorough background on how to measure, interpret, and apply fire severity in fire management

Large Mammals and Wetland utilization: a case study in Yankari Game Reserve Nigeria

The African plain harbours high abundance and diversity of mammals, most of which are confined to protected areas (PAs) due to anthro‐ pogenic threats (Craigie et al., 2010; Dirzo et al., 2014; Estes, 1999; Kingdon, 1997). Also, PAs face problems of hunting, logging and live‐ stock grazing, conflict of interest and poor management (Caro, 2001; Dharmaratne, Sang, &Walling, 2000; Gardner et al., 2009; Geldmann et al., 2015; Geldmann et al., 2015; Hall, Harris, Medjibe, & Ashton, 2003; Pressey, 1994; Salum, Eustace, Malata, & Mbangwa, 2017; Thuiller, 2007), consequently disrupting conservation goals, effective monitor‐ ing and understanding of habitat utilisation dynamics of mammals. Although wetlands are important habitats for sustaining animal populations, there is a widespread trend of increasing degradation of these habitats (Fynn, Chase, & Rӧder, 2014) and dearth of infor‐ mation pertaining to wetland utilisation in most PAs. While this is integral for effective conservation practice, few studies focus on this area in Africa (Arzamendia, Cassini, & Vila, 2006; Kumar, Mudappa, & Raman, 2010; Rahman et al., 2017). Here, we investigated the wet‐ land utilisation dynamics of large mammals in Yankari Game Reserve (YGR). The objective was to determine abundance, density and di‐ versity of large mammals and whether these variables were associ‐ ated with wetland size and time of da