Muscle fibers of the masseter muscle of mice which had been fed a fine-grained diet for various periods were studied histochemically and morphometrically. The diameters of both extrafusal and intrafusal muscle fibers decreased with time in mice fed a fine-grained diet, compared with those of control mice. In animals maintained on the special diet for 160 days after weaning at the 20th postnatal day, the effects of the diet on the diameter of muscle spindles were severe, and the diameter of each type of red and white fibers was significantly smaller than those of control animals. But a significant difference was not recognized in the diameter of intermediate fibers between control and treated mice. Unexpectedly, white fibers having a smaller diameter than red fibers were observed in diet-fed mice after the 180th postnatal day, although white fibers having such small diameter were not detectable in control animals. Succinic dehydrogenase activities were decreased in both extrafusal and intrafusal fibers of experimental animals. Moreover, muscle spindles with no annulospiral endings were increased in number in mice fed the diet for 130 and 160 days after weaning, although those spindles also increased in control animals. The diameters of outer capsules and primary endings were also significantly decreased in the animals kept on the diet for a long time. These effects of the fine-grained diet on the mouse masseter muscle became severer with time.

Adaptation, Physiological↗

PubMed1987

Desmin distribution in the cardiac outflow tract of the chick embryo during aortico-pulmonary septation.

The appearance and distribution of desmin, a muscle type intermediate filament, was examined in the truncus arteriosus of the chick embryonic heart during AP septation by an indirect immunofluorescence method. Prior to septation, on the 4th day of incubation, staining with antidesmin antibody was observed in the AP septum anlagen in the distal truncus. No staining with the antibody was detected in the developing tunica media of the great arteries in the distal truncus at this stage. During septation, on the 5th day of incubation, intense staining with the antidesmin antibody was observed in the cell condensation of the AP septum. In the 6-day-old embryo, the staining in the AP septum was reduced, but fluorescence by staining with the antibody was observed in the developing tunica media. No fluorescence was detected in other mesenchymal cells in the truncal swellings. Because of the time of appearance and the localization of antidesmin reactivity in the developing AP septum, it is suggested that muscle-type cells exist in the AP septum, and that these cells may perform an important function in septation.

Animals↗

PubMed1987