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Cervical, brachial, and thoracic somites and brachial somatopleure were transplanted from quail into 2-day chick embryos to determine their contribution to the formation of the pectoralis major muscle. The results show that the musculature of the pectoralis major and pectoralis minor is derived entirely from brachial somites (16-20) while the brachial somatopleure provides much of the connective tissue of these muscles. Migration of somitic cells into the somatopleure appears to begin before the somites are fully formed. The primordium of the pectoralis muscle forms at the base of the wing bud and extends ventro-caudally into the thoracic area to attach to the sternum.

We have developed a rapid sensitive test for factors that mimic the trophic effects of nerves by maintaining normal rates of protein synthesis in denervated forelimb blastemata of adult newts (Notophthalmus viridescens). Rates of protein synthesis in secondary blastemata are similar. However, after they are denervated and explanted into organ culture the rates of protein synthesis first increase and later fall below control values. Similar changes occur after denervation in vivo. The alterations in the rates of protein synthesis are prevented by adding to the culture medium aqueous extracts from brains of adult newts or chicken embryos. The active material is either a peptide or a protein.

Normal and dystrophic mouse muscles were separated into a predominantly white muscle fraction (gastrocnemius, extensor digitorum longus) and a predominantly red muscle fraction (diaphragm). Acetylcholinesterase (AChE) was extracted from each muscle fraction using a Triton X-100/NaCl buffer. Six forms of AChE were separated from each muscle homogenate by velocity sedimentation on linear sucrose gradients. Their apparent sedimentation coefficients in each case were 19.7S, 16.0S, 13.3S, 10.4S, 7.6S, and 3.9S. Gel electrophoresis of crude muscle homogenates under nondenaturing conditions (native gels) and of ech separate isozyme fraction gave one band of AChE activity with a consistent Rf (relative mobility) value. Reelectrophoresis of native gel bands on SDS/acrylamide slab gels revealed a similar monomeric subunit protein from either crude muscle homogenates or isozyme fractions with an apparent molecular weight of approximately 69,000 daltons. Our results indicate that the AChE distribution and activity are severely affected in dystrophic "white" muscles (anaerobic) but much less so in "red" muscles (aerobic). Dystrophic predominantly white muscles weigh less, contain less protein, and have a decreased total AChE activity in comparison with their normal counterparts. Furthermore, the relative proportions of AChE activity in each isozyme fraction is altered between normal white and dystrophic white muscle fractions: i.e., dystrophic white muscle contains a decreased proportion of a low molecular weight form (7.6S) and increased proportions of higher molecular weight forms (16.0S, 19.7S). In contrast, no significant differences occur in AChE activity or distribution between normal and dystrophic predominantly red muscle. The changes in white muscle AChE are toward a pattern common to red muscle. This suggests that the effect of muscular dystrophy and its related stress on mouse white muscle is at least in part a shift from a predominantly anaerobic, fatigable metabolism to an aerobic, fatigue-resistant metabolism.

The effect of short-term denervation (0, 12, 24, and 72 hours) on the levels of cyclic 3'5'-guanosine monophosphate (cGMP) and cyclic 3'5'-adenosine monophosphate (cAMP) in adult newt (Notophthalmus viridescens) forelimbs at 15, 22, and 35 days of regeneration was investigated. Regenerate blastema and stump cyclic nucleotide levels were compared with those of the contralateral intact forelimb and hindlimb, with levels in the normally regenerating blastema, and with levels measured in the forelimbs of intact, nonoperated animals. Variations in cyclic nucleotide levels occurred according to regeneration stage and tissue type. Changes in level were noted immediately upon denervation and subsequently at other sample times in all regenerate and control series. Parallel fluctuations occurred in regenerate stump and contralateral intact forelimbs. Our results from nonamputated denervated and sham-denervated animals indicate that short-term, denervation-associated cyclic nucleotide fluctuations cannot be attributed solely to the loss of innervation.

Cyclic 3', 5'-guanosine monophosphate (cGMP) was measured at eight stages of forelimb regeneration in adult newts and compared with the cGMP levels of non-regenerating control limbs. There was a significant increase in cGMP content during dedifferentiation followed by a sharp decrease to minimal levels at the cone stage. A second smaller increase in cGMP occurred between the cone stage and mid-differentiation, followed by a decrease to relatively constant levels approaching control values as differentiation progressed. The changes in cGMP during dedifferentiation and during the period of highest cell proliferation indicate that cGMP may play a role in these processes. The smaller increases in cGMP levels during differentiation may reflect a reduced rate of cell division in the differentiating tissues.