The growth of nerves in relation to the formation of premuscle cell masses in the developing chick forelimb

Abstract

A description is given of the growth of segmental nerves 13 to 16 (SN13 to SN16) from the brachial myotomes into the ventral and dorsal premuscle cell masses of the chick forelimb. At stage 25 (Hamburger and Hamilton, '51), segmental nerves have converged to form two nerve trunks which enter the ventral and dorsal premuscle cell masses. These nerves grow into the limb, parallel to its proximodistal axis. The nerve trunk in the ventral compartment, the brachialis longus inferior (bli n), grows on the brachial artery as far as the metacarpals. The nerve trunk in the dorsal compartment, the brachialis longus superior (bls n), grows on the precartilage adjacent to a dorsal premuscle density as far as the metacarpals. The brachialis longus inferior and superior nerve trunks give rise to a number of nerves during their growth to the metacarpals. Each of these nerves appears at the time of formation of a new premuscle cell density. At late stage 25, a posterior and ventral premuscle density forms in the middle of the stylopodium; posterior fascicles of the bli n diverge at this level and grow toward this new density to form the ulnar nerve. By stage 26 a posterior and ventral premuscle density is prominent over the bli n, at the junction of the stylopodium and the zeugopodium; ventral fascicles of the bli n grow into this density to form the flexor digitorum profundus nerve. At this stage a posterior and dorsal premuscle density forms just beyond the junction of the stylopodium and zeugopodium. Posterior fascicles of the bls n diverge at this level and grow toward this density to form a nerve from which the extensor metacarpi ulnaris, extensor digitorum communis, and radialis laterialis nerves are destined to form. At stage 29 the premuscle cell masses of the autopodium have formed. The remaining nerve fascicles comprising the bls n (the radialis profundus nerve) grow into the autopodium and branch to innervate each of the dorsal premuscles. The remaining nerve fascicles comprising the bli n (the middle nerve) grow into the autopodium and branch to innervate each of the ventral premuscles.

Muscle force regulates bone shaping for optimal load-bearing capacity during embryogenesis

“…Chick embryos start to move as early as 4-5 days incubation, whereas in murine embryos movement is observed by E12.5 (Bennett et al, 1983;Carry et al, 1983;Hamburger and Balaban, 1963;Suzue, 1996). Although it is clear that the skeleton experiences mechanical loads exerted by muscle contraction through most of its development, the magnitude of these loads has not been appreciated.…”

Spatial distribution and size of acetylcholine receptor clusters determined by motor nerves in developing chick muscles

“…Myotubes and AChR-C then appear at 41/2-5 days (Hilfer et al, 1973;Smith & Slater, 1983). In the forearm, muscle nerve branches appear iff a defined sequence between 51/2 days and 7 clays incubation (Swanson & Lewis, 1982;Bennett et al, 1983). Hence we have examined aneural muscles from within 1 day of when innervation would normally occur, at a stage when large AChR-C were always present in normal wings (7.0 days).…”

“…AChR-C were even more closely spaced on myotubes of the UMD muscle (54 • 7 ~m at 9 days). Nerves first enter the muscle mass from which the ALD forms at about 4 days incubation (Bennett eta!., 1983), but only reach the level of the UMD at about 6.5 days (Swanson & Lewis, 1982;Bennett et al, 1983). If, as a result, synapse formation in the UMD lags 2 days behind the ALD, the 9-day UMD would be expected to contain a high proportion of non-contacted AChR-C (perhaps 75%; see Smith & Slater, 1983).…”

Skeletal Muscle

“…It may bind to cytoplasmic actin and thus establish transmembrane connections (SINGER 1979;KESKI-OJA et al 1980). Bar, 5 Jlm op (LEWIS et al 1981;BENNETT et al 1983a). Chicken myoblasts and myotubes in culture attach to solid surfaces, but only in the presence of fibronectin derived from serum or from fibroblasts contaminating the culture.…”