title: Muscle growth in Nile tilapia (Oreochromis niloticus): histochemical, ultrastructural and morphometric study.
abstract: Muscle growth in Nile tilapia (Oreochromis niloticus) was studied focusing on histochemical, ultrastructural, and morphometric characteristics of muscle fibers. Based on body length (cm), we studied four groups: G1=1.36+/-0.09, G2=3.38+/-0.44, G3=8.90+/-1.47, and G4=28.30+/-3.29 (mean+/-S.D.). All groups showed intense reaction to NADH-TR in subdermal fibers and weak or no reaction in deep layer fibers. In G3 and G4, an intermediate layer was also observed with fibers presenting weak reaction; in G4, groups of fibers with intense reaction were observed in the subdermal region. The myosin ATPase (m-ATPase) activities were acid-stable and alkali-labile in subdermal fibers; most deep layer fibers were alkali-stable and acid-labile. Intermediate fibers were acid-labile and alkali-stable. Two fiber populations were observed near deep muscle layer: one large presenting weak acid- and alkali-stable and the other small alkali-stable. During growth, muscle fiber hypertrophy was more evident in intermediate and white fibers for G3 and G4. However, in these groups, the presence of fiber diameters < or =21 microm suggested that there is still substantial fiber recruitment, confirmed by ultrastructural study, but hypertrophy is the main mechanism contributing to increase in muscular mass.
authors.affiliation: Departamento de Morfologia, Instituto de Biociências, UNESP, Botucatu, São Paulo, 18618-000 CEP, Brazil. dpsilva@ibb.unesp.br
authors.forename: M
authors.initials: M
authors.lastname: Dal Pai-Silva
authors.forename: R F
authors.initials: RF
authors.lastname: Carvalho
authors.forename: C H
authors.initials: CH
authors.lastname: Pellizzon
authors.forename: V
authors.initials: V
authors.lastname: Dal Pai
mesh_terms: D000818:Animals; D006128:Growth / Q000502:physiology*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D009132:Muscles / Q000502:physiology* / Q000648:ultrastructure*; D017210:Tilapia / Q000033:anatomy & histology*