| Abstract: | The present work is concerned with the study of myosin fractions prepared from the hatching muscle (m. complexus) and a control muscle (m. pectoralis) of the developing goose embryo. The m. complexus attained its maximum mass at hatching and in the 4-day-old bird the mass of this muscle was only one fourth of that recorded at hatching. The m. complexus was hypertrophied already on the 21st day. At days 21, 27 and 28 of incubation and at posthatching days myosin preparations were made from both muscles. Partial purification of myosins from both sources yielded a high molecular weight fraction characteristic of the adult bird and one other protein fraction with molecular mass half of myosin. Both preparations exhibited the characteristic properties of myosin. The lower molecular weight fraction was also shown to develop filamentous aggregates as did the higher molecular-weight, gel filtrated myosin. The phosphate content of the half molecular mass myosin fraction prepared from the embryonic m. complexus at days prior to hatching was considerably higher than that of the high molecular weight fraction and the predominant component was P-Arg. Since the embryonic myosin was still not available in the m. complexus of the 4-day-old birds and the hypertrophied muscle underwent regression after hatching it appears that this myosin fraction is actively involved in breaking through the shell during the hatching period in geese. |
