130 research outputs found
Rapid dilation of the abdominal aorta during infusion of angiotensin II detected by noninvasive high-frequency ultrasonography
No full textBackgroundInfusion of angiotensin II (AngII) via subcutaneous osmotic pumps into mice promotes the development of abdominal aortic aneurysms (AAAs). These AngII-induced AAAs develop via a complex process in which there is a transmedial break, lumen dilation, thrombus formation, inflammation involving cells of both the innate and acquired immune systems, and remodeling. The recent development of a high-frequency ultrasound machine has permitted the noninvasive detection of murine abdominal aortas. We assessed the ability of a Visualsonics Vevo 660 high-resolution imaging system to detect AAAs and sequentially quantify the aortic luminal diameter. This system had 100% accuracy in detecting AngII-induced AAAs in vivo, with intrauser and interuser variation coefficients of less than 10% for quantification of the aortic lumen diameter.MethodsMale apolipoprotein E (apoE)−/− mice were infused subcutaneously with either saline or AngII and were monitored with this ultrasonic system to define the temporal changes in aortic lumen diameter. Aortic luminal diameters were measured in the aneurysm-susceptible region of the suprarenal aorta. For internal controls, abdominal aortic diameters were measured at the level of the left renal branch, because this landmark region did not dilate during AngII infusion.ResultsLuminal diameters of the suprarenal aorta did not change significantly in saline-infused mice over 28 days of measurement (P = .71). In contrast, AngII infusion led to rapid dilation of suprarenal aortas during the initial 7 days of infusion (0.071 mm/d; P = .0037 for the change in the initial expansion rate). Further luminal diameter expansions occurred for the remaining 21 days of observation at a more modest rate (0.023 mm/d; P = .0001 for continued expansion after day 7). Within the initial 14 days of AngII infusion, some apoE−/− mice died as a result of rupture of the aorta in the suprarenal region. We had previously assumed that aortic dilation and rupture occurred simultaneously. However, in the AngII-infused mice that succumbed to aortic rupture, luminal diameters increased several days before death.ConclusionsHigh-frequency ultrasonography demonstrated that suprarenal aortic expansion occurs rapidly after the initiation of AngII infusion into apoE−/− mice.Clinical RelevanceAngiotensin II has been inferred to have an important role in the development of human aortic diseases. Infusion of angiotensin II into mice leads to the development of abdominal aortic aneurysms. Definition of the natural history of abdominal aortic aneurysm development in animal models of the disease may provide insight into the factors associated with initiation and propagation in the human disease. The recent development of high-frequency ultrasonography has permitted the sequential noninvasive detection of mouse aortic luminal dimensions during angiotensin II infusion. The convergence of studies on aortic dimensions, in association with pathologic characterization of the tissue, should provide a means to define mechanisms of abdominal aortic aneurysm formation
The effects of superimposed tilt and lower body negative pressure on anterior and posterior cerebral circulations
No full textSteady-state tilt has no effect on cerebrovascular reactivity to increases in the partial pressure of end-tidal carbon dioxide (PETCO2). However, the anterior and posterior cerebral circulations may respond differently to a variety of stimuli that alter central blood volume, including lower body negative pressure (LBNP). Little is known about the superimposed effects of head-up tilt (HUT; decreased central blood volume and intracranial pressure) and headdown tilt (HDT; increased central blood volume and intracranial pressure), and LBNP on cerebral blood flow (CBF) responses. We hypothesized that (a) cerebral blood velocity (CBV; an index of CBF) responses during LBNP would not change with HUT and HDT, and (b) CBV in the anterior cerebral circulation would decrease to a greater extent compared to posterior CBV during LBNP when controlling PETCO2. In 13 male participants, we measured CBV in the anterior (middle cerebral artery, MCAv) and posterior (posterior cerebral artery, PCAv) cerebral circulations using transcranial Doppler ultrasound during LBNP stress (−50 mmHg) in three body positions (45°HUT, supine, 45°HDT). PETCO2 was measured continuously and maintained at constant levels during LBNP through coached breathing. Our main findings were that (a) steady-state tilt had no effect on CBV responses during LBNP in both the MCA (P = 0.077) and PCA (P = 0.583), and (b) despite controlling for PETCO2, both the MCAv and PCAv decreased by the same magnitude during LBNP in HUT (P = 0.348), supine (P = 0.694), and HDT (P = 0.407). Here, we demonstrate that there are no differences in anterior and posterior circulations in response to LBNP in different body positions.Library OA FundFinancial support for the initial building of the apparatus (supplies) was provided by Mount Royal University, Faculty of Science and Technology, Laboratory Support Centre, and most of the funding for data collection (student salaries) by a Government of Alberta STEP Grant (MMT and RJS), an NSERC USRA (MMT), and the MRU Petro-Canada Young Investigator award (TAD). Funds for covering the costs to publish in open access were provided by Mount Royal University Library
A History of Engiish Language Teaching. A. P. R. Howatt. Oxford University Press, 1984, 394 pages
No full textThe history of English Language Teaching (ELT) is such a vast subject that it would require several tomes to describe its historical development worldwide. It is for this reason, obviously, that the author, Senior Lecturer in the Department of Linguistics at the University of Edinburgh, has limited his scope to the European scene mainly, or in his own words in the Preface, "hence the indefinite article."
Starting, then, with the Renaissance, he subsequently deals with theories and developments of English teaching materials, the expansion of ELT in Europe, the emergence of ELT as an autonomous profession, and the impact of applied linguistics in the US and Britain. Following the four parts of the book, which will be reviewed in similar order in this paper, the interested reader finds: a chronology of English language teaching, biographical notes, an appendix containing the translation of Wilhelm Vietor's memorable Der Sprachunterricht muss umkehren!, and a bibliography.
The wealth of information, presented chronologically in clear language together with the writer's insights as an educator, makes the book an indispensible source for the teacher of Ehglish, native and non-native alike. To do justice to the author in his impressive undertaking and present the reader with something more than a mere evaluation, I have called this paper a "descriptive review," implying a synoptic description of the subject matter interspersed with my comments
A History of Engiish Language Teaching. A. P. R. Howatt. Oxford University Press, 1984, 394 pages
No full textThe history of English Language Teaching (ELT) is such a vast subject that it would require several tomes to describe its historical development worldwide. It is for this reason, obviously, that the author, Senior Lecturer in the Department of Linguistics at the University of Edinburgh, has limited his scope to the European scene mainly, or in his own words in the Preface, "hence the indefinite article."
Starting, then, with the Renaissance, he subsequently deals with theories and developments of English teaching materials, the expansion of ELT in Europe, the emergence of ELT as an autonomous profession, and the impact of applied linguistics in the US and Britain. Following the four parts of the book, which will be reviewed in similar order in this paper, the interested reader finds: a chronology of English language teaching, biographical notes, an appendix containing the translation of Wilhelm Vietor's memorable Der Sprachunterricht muss umkehren!, and a bibliography.
The wealth of information, presented chronologically in clear language together with the writer's insights as an educator, makes the book an indispensible source for the teacher of Ehglish, native and non-native alike. To do justice to the author in his impressive undertaking and present the reader with something more than a mere evaluation, I have called this paper a "descriptive review," implying a synoptic description of the subject matter interspersed with my comments
Education for assimilation: language, literature, and acculturation in senior English
No full textThis thesis examines the application and role of education in general in the efforts to induce acculturation into and acceptance of settler society hegemony. Specifically, it illustrates how two disciplines currently work to incite passive indoctrination into the status quo, namely English Language Arts and Literature. During the imperial enterprise, language and literature acted as a means for the communication of settler conceptions of 'truth' and 'reality, ' perceptions that subverted Native meanings of both. Supported by the law, institutionalized religion, and violence, this subversion of First Nations understanding contributed significantly to their colonization. Importantly, the application of language and literature and their influence in this context persists today in the neocolonial educational environment. Public schools continue to stress the importance of the 'mother tongue' in providing success for students and recognize its role in advancing assimilation. At the same time, a pronounced lack of 'meaningful' Native representation and a number of fundamental impediments to its incorporation in the English classroom inhibit an understanding of Native cultures and concerns as they are communicated in literature. A qualitative content analysis of these resources, as well as theoretical application, is used to illustrate how all of these mechanisms work in conjunction to perpetuate the settler society objective of acculturation. In so doing, this thesis also recognizes the valuable contributions to pedagogy made by a number of groups and institutions in an effort to combat education for assimilation.The original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b118587
Modes of Defining Atherosclerosis in Mouse Models: Relative Merits and Evolving Standards
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