Investigation of optimal sample preparation conditions with potassium triiodide and optimal imaging settings for microfocus computed tomography of excised cat hearts

OBJECTIVE: To determine optimal sample preparation conditions with potassium triiodide (I2KI) and optimal imaging settings for microfocus CT (micro-CT) of excised cat hearts. SAMPLE 7 excised hearts (weight range, 10 to 17.6 g) obtained from healthy adult cats after euthanasia by IV injection of pentobarbital sodium. PROCEDURES: Following excision, the hearts were preserved in 10% formaldehyde solution. Six hearts were immersed in 1.25% I2KI solution (n = 3) or 2.5% I2KI solution (3) for a 12-day period. Micro-CT images were acquired at time 0 (prior to iodination) then approximately every 24 and 48 hours thereafter to determine optimal sample preparation conditions (ie, immersion time and concentration of I2KI solution). Identified optimal conditions were then used to prepare the seventh heart for imaging; changes in voltage, current, exposure time, and gain on image quality were evaluated to determine optimal settings (ie, maximal signal-to-noise and contrast-to-noise ratios). Images were obtained at a voxel resolution of 30 mm. A detailed morphological assessment of the main cardiac structures of the seventh heart was then performed. RESULTS: Immersion in 2.5% I2KI solution for 48 hours was optimal for sample preparation. The optimal imaging conditions included a tube voltage of 100 kV, current of 150 mA, and exposure time of 354 milliseconds; scan duration was 12 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: Results provided an optimal micro-CT imaging protocol for excised cat hearts prepared with I2KI solution that could serve as a basis for future studies of micro-CT for high resolution 3-D imaging of cat hearts

Shape Analysis and Computational Fluid Simulations to Assess Feline Left Atrial Function and Thrombogenesis

In humans, there is a well-established relationship between atrial fibrillation (AF), blood flow abnormalities and thrombus formation, even if there is no clear consensus on the role of left atrial appendage (LAA) morphologies. Cats can also suffer heart diseases, often leading to an enlargement of the left atrium that promotes stagnant blood flow, activating the clotting process and promoting feline aortic thromboembolism. The majority of pathological feline hearts have echocardiographic evidence of abnormal left ventricular filling, usually assessed with 2D and Doppler echocardiography and standard imaging tools. Actually, veterinary professionals have limited access to advanced computational techniques that would enable a better understanding of feline heart pathologies with improved morphological and haemodynamic descriptors. In this work, we applied state-of-the-art image processing and computational fluid simulations based on micro-computed tomography images acquired in 24 cases, including normal cats and cats with varying severity of cardiomyopathy. The main goal of the study was to identify differences in the LA/LAA morphologies and blood flow patterns in the analysed cohorts with respect to thrombus formation and cardiac pathology. The obtained results show significant differences between normal and pathological feline hearts, as well as in thrombus vs non-thrombus cases and asymptomatic vs symptomatic cases, while it was not possible to discern in congestive heart failure with thrombus and from non-thrombus cases. Additionally, in-silico fluid simulations demonstrated lower LAA blood flow velocities and higher thrombotic risk in the thrombus cases

Conserved ancestral tropical niche but different continental histories explain the latitudinal diversity gradient in brush-footed butterflies.

The global increase in species richness toward the tropics across continents and taxonomic groups, referred to as the latitudinal diversity gradient, stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluate several of these hypotheses to explain spatial diversity patterns in a butterfly family, the Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal, and also the extent to which these processes differ among regions at the same latitude. We generate a time-calibrated phylogeny containing 2,866 nymphalid species (~45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the latitudinal diversity gradient among regions because temporal diversification dynamics differ greatly across longitude. The Neotropical diversity results from low extinction rates, not high speciation rates, and biotic interchanges with other regions are rare. Southeast Asia is also characterized by a low speciation rate but, unlike the Neotropics, is the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, combined with tropical niche conservatism, played a major role in generating the modern latitudinal diversity gradient of nymphalid butterflies

Redox regulation of mitochondrial fission, protein misfolding, synaptic damage, and neuronal cell death: potential implications for Alzheimer’s and Parkinson’s diseases

Normal mitochondrial dynamics consist of fission and fusion events giving rise to new mitochondria, a process termed mitochondrial biogenesis. However, several neurodegenerative disorders manifest aberrant mitochondrial dynamics, resulting in morphological abnormalities often associated with deficits in mitochondrial mobility and cell bioenergetics. Rarely, dysfunctional mitochondrial occur in a familial pattern due to genetic mutations, but much more commonly patients manifest sporadic forms of mitochondrial disability presumably related to a complex set of interactions of multiple genes (or their products) with environmental factors (G × E). Recent studies have shown that generation of excessive nitric oxide (NO), in part due to generation of oligomers of amyloid-β (Aβ) protein or overactivity of the NMDA-subtype of glutamate receptor, can augment mitochondrial fission, leading to frank fragmentation of the mitochondria. S-Nitrosylation, a covalent redox reaction of NO with specific protein thiol groups, represents one mechanism contributing to NO-induced mitochondrial fragmentation, bioenergetic failure, synaptic damage, and eventually neuronal apoptosis. Here, we summarize our evidence in Alzheimer’s disease (AD) patients and animal models showing that NO contributes to mitochondrial fragmentation via S-nitrosylation of dynamin-related protein 1 (Drp1), a protein involved in mitochondrial fission. These findings may provide a new target for drug development in AD. Additionally, we review emerging evidence that redox reactions triggered by excessive levels of NO can contribute to protein misfolding, the hallmark of a number of neurodegenerative disorders, including AD and Parkinson’s disease. For example, S-nitrosylation of parkin disrupts its E3 ubiquitin ligase activity, and thereby affects Lewy body formation and neuronal cell death

Transtornos mentais comuns entre estudantes de medicina da Universidade Federal de Sergipe: estudo transversal

Objetivo: Estimar a prevalência de transtorno mental comum e fatores associados entre estudantes de Medicina da Universidade Federal de Sergipe. Método: Estudo transversal com 473 dos 512 matriculados em 2006, aplicando o Self Reporting Questionnaire-20 e um questionário estruturado sobre características sociodemográficas, processo ensino-aprendizagem e vivências psicoemocionais. Os calouros foram excluídos após comparação inicial com os alunos do 2° ao 12° períodos. Análise estatística por regressão logística múltipla, após estatística descritiva e cálculo das ORs simples e ajustadas. Resultados: A prevalência de transtorno mental comum geral foi de 40% (n = 473), mas com a retirada dos calouros, aumentou para 42,5% (n = 433) entre os alunos do 2° ao 12° semestre, sendo maior entre aqueles que não acreditavam ter adquirido habilidades para se tornarem bons médicos (OR = 2,82), que se sentiam pouco confortáveis com as atividades do curso (OR = 3,75), que se consideravam emocionalmente tensos (OR = 2,14), nos que não se consideravam felizes (OR = 2,85), nos que achavam que o curso era menos do que esperavam (OR = 1,64) e nos que tiveram diagnóstico prévio de transtorno mental feito por psiquiatra (OR = 3,78). Conclusão: Os resultados sugerem a necessidade de mudanças no processo ensino-aprendizagem, bem como estruturação de programas para cuidar da saúde mental dos estudantes. _________________________________________________________________________________________ ABSTRACT: Objective: Estimate the prevalence of common mental disorder and its associated factors among medical students of the Universidade Federal de Sergipe. Method: A cross-sectional study was carried out, applying Self Reporting Questionnaire-20 to 473 students from the 512 medical students enrolled in 2006 and compared with compared with a structured questionnaire by the authors containing information on the socio-demographic characteristics, the teaching–learning process and the psycho-emotional experiences of the students. Freshmen were excluded after initial comparison with the students already exposed to the medical course. Statistical analysis by multiple logistic regression after calculating simple and adjusted odds ratio (OR). Results: The general prevalence of common mental disorder was 40% (n = 473); after exclusion of the freshmen it increased to 42.5% among students from the 2nd to the 12th semester.It was higher among those who did not have faith in their acquisition of the skills needed to become a good doctor (OR = 2.82), who felt less comfortable about course activities (OR = 3.75), who considered themselves emotionally stressed (OR = 2.14), among those who did not consider themselves happy (OR = 2.85), who believed that the course did not match their expectations (OR = 1.64) and those who had a prior diagnosis of mental disorder by a psychiatrist (OR = 3.78). Conclusion: The results suggest the necessity of changes to the teaching-learning process and the establishment of a preventive mental health program for medical students