Postnatal growth of fibres on M. gracilis (pars caudalis) in both sexes of rat.
Measurements of cross sectional area on individual fibres of M. gracilis (pars caudalis) of Wistar rats of both sexes in different ages were done. Growth equations pattern and growth rates equations pattern of each muscle fibre type were also determined. In rats 12 d old, muscle fibres present a somewhat uniform SDH activity. By 23 d and thereafter, SDH technique revealed a mixed population of red, intermediate and white fibres. There was a close relationship between cross sectional area and age, where each fibre type presents a distinct exponential growth curve pattern. The highest growth rates were observed at 23 and 45 d. After this age, a markedly fall in growth rates occurs, except for white fibres, where this decrease was less intense. Red and intermediate muscle fibres tend to estabilize their growth earlier than white fibres.
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D008297:Male; D024510:Muscle Development; D051381:Rats; D011919:Rats, Inbred Strains; D013623:Tail