Developmental changes and eddect of soft diet on enzyme activites and on morphology of rat masseter and cortex mitochondria

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1) Development of masseter muscleDevelopment of mitochondria was mostly gradual in 0- to 15-day postnatal rats. However, a notable increase was found in the CSA of mitochondria between days 10 and 15 in the neonatal rat. The change in feeding behavior from suckling to mastication was well-correlated with an increase of mitochondrial enzyme activites, also supported by the early development of mitochndria, especially with the initiation of growth in the corss-sectional area of the mitochndria.2) Development of rat cortexThe increases of oxidase activites are approximately correlated with the enhancement of complexity of mitochondrial cristae observed by TEM, which is remarkable after 10 days postnatal of rat cortex. The number of mitochondrion per cell nearly doubles and area of the mitochondrion reduced to one-half between 5 days and 10 days. The CSAs of mitochondrion and cell increase about twice from 10 days to 15 days, stabilize at 21 days, indicating the mitochondria and cell grow synchronously between 10 days and 21 days.3) Effect of soft dietThe decreased of number mitochondria concern with the reduction of these enzyme activities. However, a notable increase was found in succinate-OィイD22ィエD2 oxidoreductase activity from 26 days to 60 days. An constant in the number of mitochondria per muscle fiber did not seem to occur during these periods. The change in feeding stress to mastication was correlated with an decrease of mitochondrial enzyme activites, especially with the decreased in the number of the mitochondria per area with long-term soft diet.