44 research outputs found
Comparison of electrocardiographic-gated multi-detector computed tomography and two-dimensional echocardiographic methods in the assessment of left atrial size
No full textCorrelations using long-axis left atrial dimension-to-descending aorta ratio calculated by computed tomography were either poor or absent when compared with long-axis echocardiographic-derived ratios for maximal and minimal left atrial dimensions.
Echocardiography underestimated short-axis left atrial dimension-to-ascending aorta compared to our gold-standard at end-ventricular systole and diastole with a bias of 0.21 (95% limits of agreement: 0.09 to 0.51) and 0.26 (95% limit of agreement: -0.15 – 0.66) respectively. Conversely, long-axis ratios showed almost perfect agreement with our gold-standard. Intra- and inter-observer variability for both modalities at end-ventricular systole and diastole were adequate (CVs<15%). In conclusion, our data demonstrate that the maximal long-axis left atrial dimension-to-ascending aorta ratio is the preferable unidirectional method to assess left atrial size. These findings provide support for continued investigation into the best way to assess the left atrial size using echocardiography-based linear measurements in veterinary medicine as well as the use of advanced imaging modalities as a gold standard
Role of endothelin-1 in the renal handling of salt in early Type 1 diabetes mellitus
No full textTight control of blood glucose and blood pressure (BP) reduces cardiovascular risk
in early Type 1 diabetes mellitus (T1DM). Increased BP normally increases renal
medullary perfusion and sodium excretion. This is called acute pressure natriuresis.
Inadequate acute pressure natriuresis disrupts circadian regulation of BP, which
predicts hypertension. The peptide, endothelin-1 (ET-1), regulates BP via ETA and
ETB receptors. ETA receptor antagonists reduce BP and restore its circadian rhythm.
Two hypotheses were investigated. First, that acute pressure natriuresis is impaired
in early T1DM, prior to established nephropathy, and this is associated with elevated
BP. Second, that the mechanism is an ETA receptor-mediated blunting of medullary
perfusion which can be reversed with insulin and ETA receptor antagonism.
Experimental acute pressure natriuresis was induced in young, early T1DM
(2-3 weeks post streptozotocin) Sprague Dawley rats and healthy controls. Despite
maintaining glomerular filtration rate, early T1DM suppressed urinary flow (UV,
22.9±2.9 v. 93.7±11.1μl/min/gkw) and sodium excretion (UNaV, 3.2±0.7 v.
22.7±3.3μmol/min/gkw) rates by >80%, and reduced gradients of pressure diuresis
(linear, 1.9 to 0.3) and natriuresis (non-linear k, 0.05 to 0.01) curves. Insulin
treatment lowered blood glucose (16.8±1.8 to 9.3±0.6mmol/l) and restored gradients
of the responses. Tissue and urine analyses did not suggest structural nephropathy.
In early T1DM rats, changes in BP on radiotelemetry were consistent with impaired
circadian regulation of BP and precursors of hypertension: 24–hour diastolic BP rose
(92.3±0.4 to 97.1±0.5mmHg), and the circadian dip in diastolic BP fell (6±1 to
2±1%). Atrasentan (ETA receptor antagonist, 5mg/kg/day orally) reduced diastolic
dipping in early T1DM (3±1 to 1±1%) while additional ETB receptor antagonism
(A-192621, 10mg/kg/day orally) reversed this, suggesting that ETA, and not ETB
receptors, mediate impairment of acute pressure natriuresis. To address this, renal
blood flow was measured during experimental acute pressure natriuresis and ET
receptor antagonism. Early T1DM suppressed the normal rise in medullary
perfusion (flux, 227.2±26.7 v. 115.4±10.3%) by ~90%. Suppressed medullary flux
was unaffected by insulin (112.2±6.8%), despite restoration of UV and UNaV. In
controls, atrasentan reduced UV (15.7±4.9 v. 38.6±6.2μl/min/gkw), UNaV (1.7±0.5
v. 16.7±1.4μmol/min/gkw), FENa (3.4±1.4 v. 15.0±2.4%) and medullary flux
(122.2±26.7%) by 60 to 90% of control values, while A-192621 increased UNaV
(26.6±6.9μmol/min/gkw) and FENa (21.6±3.4%), but not medullary flux, by ~50%.
ET receptor antagonism did not modify early T1DM+/-insulin effects. Diabetic
status had no effect on renal ET-1 and ET receptor expression.
These results support the first hypothesis but disprove the second. Early T1DM
blunts medullary perfusion and acute pressure natriuresis, and increases diastolic BP.
Insulin restores natriuresis but not medullary flow. Therefore, targeting medullary
perfusion may reduce cardiovascular risk in early T1DM, but this is not achievable
with selective ETA receptor antagonists. Novel natriuretic (ETA) and anti-natriuretic
(ETB) roles for ET receptors, which are not apparent in early T1DM during severe,
experimental rises in BP, appear to contribute to daily regulation of BP, and may
preclude the use of selective ETA receptor antagonists in T1DM prior to nephropathy
The development of the Russian piano concerto in the nineteenth century.
No full textThe Russian piano concerto could not have had more inauspicious beginnings. Unlike the symphonic poem (and, indirectly, the symphony)- genres for which Glinka, the so-called 'Father of Russian Music', provided an invaluable model: 'Well? It's all in "Kamarinskaya", just as the whole oak is in the acorn' to quote Tchaikovsky - the Russian
piano concerto had no such indigenous prototype. All that existed to inspire would-be concerto composers were a handful of inferior potpourris and variations for piano and orchestra and a negligible concerto by Villoing dating from the 1830s. Rubinstein's five concertos certainly offered something more substantial, as Tchaikovsky acknowledged in his First Concerto, but by this time the century was
approaching its final quarter.
This absence of a prototype is reflected in all aspects of Russian concerto composition. Most Russian concertos lean perceptibly on the stylistic features of Western European composers and several can be justly accused of plagiarism. Furthermore, Russian composers faced formidable problems concerning the structural organization of their concertos, a factor which contributed to the inability of several,
including Balakirev and Taneyev, to complete their works. Even Tchaikovsky encountered difficulties which he was not always able to overcome.
The most successful Russian piano concertos of the nineteenth century, Tchaikovsky's No.1 in B flat minor, Rimsky-Korsakov's Concerto in C sharp minor and Balakirev's Concerto in E flat, returned to indigenous sources of inspiration: Russian folk song and Russian orthodox chant. As characteristic of nationalist works in general, their contribution to the development of the piano concerto was not profound; nevertheless, they represent a valuable, if numerically•small, addition to the repertory, and laid the foundations of a twentieth-century school of concerto composition, headed by Rachmaninovand Prokofiev, of unparalleled brilliance and virtuosity
The unspoken power of collage? Using an innovative arts-based research method to explore the experience of struggling as a teacher
No full textThis article reports on the methodological approach taken in a doctoral study that explores what it means to be struggling as a teacher. Participants were
established and experienced teachers and leaders in the secondary school system in England. A particular form of collage – where materials are placed rather than
stuck – was used within the context of a research interview. Arts-based methods such as collage are gaining in popularity as they stimulate visual rather than
linguistic thinking and offer the opportunity to express experiences as holistic, non-linear metaphors. Collage also has revelatory potential as it helps uncover
that which participants cannot necessarily express in words alone. The author presents the analytical challenges of intermingling the verbal and visual data in
her study by discussing the collages created by two participants. An analysis of those collages shows that factors influencing struggling can be both internal and external. Struggling was found to be experienced as a temporary fractured state. Struggling was expressed by participants as heightened bodily tensions with a predominantly negative emotional tone; it can also involve a damaged self-view and a reduced sense of controllability, and may lead to impaired performance
Vascular function in dogs with myxomatous mitral valve disease
No full textMyxomatous mitral valve disease (MMVD) is the commonest heart disease in dogs. Vascular dysfunction contributes to human heart disease but has not been assessed in pet dogs by myography. We hypothesised that vascular dysfunction contributes to progression of MMVD and can be quantified with myography.
Isomeric myography was performed on femoral, mesenteric, renal, and pulmonary arteries from pet dogs euthanised for welfare reasons. Testicular arteries were collected from dogs undergoing routine castration as a control group. Histopathology analysis was made for confirmation of arterial tissue. MMVD was graded 1-4 (Whitney classification). Arteries were stretched to an internal circumference (IC1) that generated maximal tension (mmHg) to high potassium concentrations (normalisation). The ratio of IC1:IC100mmHg (normalisation factor) was calculated for every artery. Vasoconstriction to phenylephrine, and vasodilation to acetylcholine (endothelial dependent) and sodium nitroprusside (endothelial independent) were assessed by cumulative response curves. Concentrations of agents that gave 50% maximal response (EC50/IC50) were calculated. Response to high potassium physiological salt solution (KPSS) was calculated as variation in percentage between minimum and maximum response and results for tissue from the same dog but on different days were compared.
Histopathology confirmed all the samples processed were arteries. Normalisation factors were determined for renal, femoral and mesenteric artery. Impaired endothelial dependent vasorelaxation was identified in all dogs with MMVD graded 3 and 4 and in some arteries of dogs with MMVD graded 1 and 2. Pulmonary and testicular arteries failed to show response on myograph. No significant difference was identified in KPSS response in the same dog over seven days.
Isomeric myography is feasible in pet dogs and can be used to investigate vascular dysfunction. Impaired endothelial-dependent relaxation was identified more frequently in dogs with higher MMVD grade. Further investigation is required to establish the relationship between MMVD and vascular dysfunction
Efficacy of pimobendan in the prevention of congestive heart failure or sudden death in doberman pinschers with preclinical dilated cardiomyopathy (the PROTECT study)
No full text<p>Background: The benefit of pimobendan in delaying the progression of preclinical dilated cardiomyopathy (DCM) in Dobermans is not reported.</p>
<p>Hypothesis: That chronic oral administration of pimobendan to Dobermans with preclinical DCM will delay the onset of CHF or sudden death and improve survival.</p>
<p>Animals: Seventy-six client-owned Dobermans recruited at 10 centers in the UK and North America.</p>
<p>Methods: The trial was a randomized, blinded, placebo-controlled, parallel group multicenter study. Dogs were allocated in a 1:1 ratio to receive pimobendan (Vetmedin capsules) or visually identical placebo.</p>
<p>The composite primary endpoint was prospectively defined as either onset of CHF or sudden death. Time to death from all causes was a secondary endpoint.</p>
<p>Results: The proportion of dogs reaching the primary endpoint was not significantly different between groups (P = .1). The median time to the primary endpoint (onset of CHF or sudden death) was significantly longer in the pimobendan (718 days, IQR 441–1152 days) versus the placebo group (441 days, IQR 151–641 days) (log-rank P = 0.0088). The median survival time was significantly longer in the pimobendan (623 days, IQR 491–1531 days) versus the placebo group (466 days, IQR 236–710 days) (log-rank P = .034).</p>
<p>Conclusion and Clinical Importance: The administration of pimobendan to Dobermans with preclinical DCM prolongs the time to the onset of clinical signs and extends survival. Treatment of dogs in the preclinical phase of this common cardiovascular disorder with pimobendan can lead to improved outcome.</p>
Introducing photonics
No full textThe essential guide for anyone wanting a quick introduction to the fundamental ideas underlying photonics. The author uses his forty years of experience in photonics research and teaching to provide intuitive explanations of key concepts, and demonstrates how these relate to the operation of photonic devices and systems. Readers will gain insight into the nature of light and the ways in which it interacts with materials and structures, and learn how these basic ideas are applied in areas such as optical systems, 3D imaging and astronomy. Carefully designed worked examples and end-of-chapter problems enable students to check their understanding, with full solutions available online. Mathematical treatments are kept as simple as possible, allowing readers to grasp even the most complex of concepts. Clear, concise and accessible, this is the perfect guide for undergraduate students taking a first course in photonics, and anyone in academia or industry wanting to review the fundamental
Differential phase tracking applied to Bragg gratings in multi-core fibre for high accuracy curvature measurement
No full textHigh resolution quasi-static and dynamic curvature measurements are made by differential interferometric phase measurement of fibre Bragg gratings in separate cores of a multi-core fibre. A DC curvature stability of 1 X 10(-3) m(-1) and an AC curvature resolution of 1 X 10(-4) m(-1)/Hz(1/2) are reported
Time division multiplexing of fiber Bragg grating sensors using a mode-locked fiber laser source
No full textAn efficient multiplexing method for fiber Bragg grating sensors based on a broadband mode-locked laser source and interferometric interrogation is described. The system has the capability to interrogate several hundred fiber Bragg grating sensors on a single fiber, whilst achieving sub-microstrain resolution over bandwidths greater than 100 kHz. A demonstration system with 8 sensors is presented, which achieves strain resolutions less than 213 n epsilon/Hz(1/2) up to 100 Hz
