Otomicroscopic and histologic findings of induced myringosclerosis in rats: a critical study of an experimental model.

UNLABELLED: Myringosclerosis is characterized by hyaline changes of the lamina propria of the tympanic membrane. Experimental studies have used otomicroscopy or histology to evaluate myringosclerosis in animals, but they do not correlate precisely these two methods. AIM: The present study evaluates the accuracy of otomicroscopy in the diagnosis of myringosclerosis in rats. STUDY DESIGN: Experimental. MATERIAL AND METHOD: Myringosclerosis was induced by transtympanic inoculation of Streptococcus pneumoniae in 25 Wistar rats, which were examined weekly through otomicroscopy and sacrificed after eight weeks for histologic study of their tympanic membranes. RESULTS: From the comparison of the otomicroscopic data in relation to the histologic findings, we could observe sensibility of 80% and specificity of 75% for the otomicroscopy. CONCLUSION: Considering the results in this study, otomicroscopy did not represent a good method to evaluate myringosclerosis in this experimental model.

Effects of controlled and pressure support mechanical ventilation on rat diaphragm muscle.

PURPOSE: The objective of this study was to analyze the effects of Pressure Controlled Ventilation mode (PCV-C) and PSV mode in diaphragm muscle of rats. METHODS: Wistar rats (n=18) were randomly assigned to the control group or to receive 6 hours of PCV and PSV. After this period, animals were euthanized and their diaphragms were excised, frozen in liquid nitrogen and stored in at -80º C for further histomorphometric analysis. RESULTS: Results showed a 15% decrease in cross-sectional area of muscle fibers on the PCV-C group when compared to the control group (p<0.001) and by 10% when compared to the PSV group (p<0.05). Minor diameter was decreased in PCV-C group by 9% when compared with the control group (p<0.001) and by 6% when compared to the PSV group (p<0.05). When myonuclear area was analyzed, a 16% decrease was observed in the PCV-C group when compared to the PSV group (p<0.05). No significant difference between the groups was observed in myonuclear perimeter (p>0.05). CONCLUSION: Short-term controlled mechanical ventilation seems to lead to muscular atrophy in diaphragm fibers. The PSV mode may attenuate the effects of VIDD.

Effects of controlled and pressure support mechanical ventilation on rat diaphragm muscle / Efeitos da ventilação mecânica controlada e por pressão de suporte no músculo diafragma de ratos

PURPOSE: The objective of this study was to analyze the effects of Pressure Controlled Ventilation mode (PCV-C) and PSV mode in diaphragm muscle of rats. METHODS: Wistar rats (n=18) were randomly assigned to the control group or to receive 6 hours of PCV and PSV. After this period, animals were euthanized and their diaphragms were excised, frozen in liquid nitrogen and stored in at -80º C for further histomorphometric analysis. RESULTS: Results showed a 15 percent decrease in cross-sectional area of muscle fibers on the PCV-C group when compared to the control group (p<0.001) and by 10 percent when compared to the PSV group (p<0.05). Minor diameter was decreased in PCV-C group by 9 percent when compared with the control group (p<0.001) and by 6 percent when compared to the PSV group (p<0.05). When myonuclear area was analyzed, a 16 percent decrease was observed in the PCV-C group when compared to the PSV group (p<0.05). No significant difference between the groups was observed in myonuclear perimeter (p>0.05). CONCLUSION: Short-term controlled mechanical ventilation seems to lead to muscular atrophy in diaphragm fibers. The PSV mode may attenuate the effects of VIDD.

OBJETIVO: Avaliar os efeitos do modo ventilatório controlado por pressão controlada (PCV-C) e do modo PSV sobre o músculo diafragma de ratos. MÉTODOS: Ratos (n = 18) da linhagem Wistar foram distribuídos no grupo controle (RE) ou para receber AVM por 6 horas no modo PCV-C e no modo PSV. Após esse período, os animais foram eutanasiados, o diafragma retirado e encaminhado para a análise histológica e morfométrica. RESULTADOS: Os resultados revelaram uma redução da área das fibras musculares de 15 por cento no grupo PCV-C em comparação ao controle (p<0,001) e de 10 por cento quando comparado ao grupo PSV (p<0,05). Já com relação ao diâmetro menor observou-se uma redução de 9 por cento do grupo PCV-C em comparação ao controle (p<0,001) e de 6 por cento em relação ao grupo PSV (p<0,05). Quando avaliada a área dos mionúcleos, notou-se uma redução de 16 por cento desse parâmetro no grupo PCV-C, comparado ao PSV (p<0,05). Não houve diferença significativa no perímetro dos mionúcleos entre os grupos estudados (p>0,05). CONCLUSÃO: O grupo PCV-C apresentou atrofia muscular em um período curto de ventilação mecânica. O modo PSV parece atenuar os efeitos da DDIV.

Achados otomicroscópicos e histológicos da miringoesclerose induzida em ratos: estudo crítico de um modelo experimental / Otomicroscopic and histologic findings of induced myringosclerosis in rats: a critical study of an experimental model

A miringoesclerose é caracterizada por hialinização da lâmina própria da membrana timpânica. Trabalhos experimentais têm utilizado a otomicroscopia ou a histologia para estudar a miringoesclerose em animais, porém sem correlacionar precisamente estes dois métodos de avaliação. OBJETIVO: Este estudo procura avaliar a acurácia da otomicroscopia no diagnóstico de miringoesclerose em modelo experimental com ratos. FORMA DE ESTUDO: experimental. MATERIAL E MÉTODO: Foi induzida miringoesclerose por inoculação transtimpânica de Streptococcus pneumoniae em 25 ratos Wistar, que foram examinados quinzenalmente por otomicroscopia e sacrificados após oito semanas, tendo suas membranas timpânicas examinadas por histologia. RESULTADOS: Da confrontação das alterações otomicroscópicas com os achados histológicos, houve uma sensibilidade de 80 por cento e especificidade de 75 por cento. CONCLUSÃO: Pelos resultados obtidos neste estudo, a otomicroscopia não representou um bom método para avaliar a miringoesclerose neste modelo experimental.