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This study performed by intraneuronal tracing directly demonstrates the presence of sympathetic postganglionic fibers in the cranial vault of the rat. Superior cervical sympathetic ganglia were injected with horseradish peroxidase (HRP), and after a 48-hour period, to permit anterograde axonal transport, the animals were sacrificed after in situ perfusion. An area of the calvaria that included portions of the frontal and parietal bones was fixed, decalcified and sectioned. HRP-containing axons were localized in the developing frontal and parietal bones of the calvaria. Adrenergic innervation was not demonstrated in sutural tissue (superior sagittal, coronal or metopic) by this technique. To our knowledge, this study is the first to trace sympathetic nerve fibers in the rat calvaria by intra-axonal transport of HRP.

In vivo effects of fibroblast growth factor (FGF) on osteogenesis were evaluated in the chick embryo. Autoradiographic studies of 3H-proline labeling over bone matrix indicated that 24 h after treatment on day 11, FGF stimulated osteogenic cell proliferation, while inhibiting the production of bone matrix collagen. However, 4 days after multiple doses of FGF, the large pool of newly formed osteogenic and chondrogenic cells expressed their function with the increased formation of matrix. The data provide in vivo evidence of the effects of exogenous FGF on osteogenesis and also point to a possible role for FGF both in embryonic osteogenesis and in fracture repair.

Earlier studies have shown that one week after sympathectomy in the rat, both bone apposition and resorption are significantly altered. Resorption in the incisor socket was now examined 1, 3 and 5 days after surgical sympathectomy. Morphometric analyses indicated that the total resorbing surface, active resorbing surface and number of osteoclasts per socket were increased one day after sympathectomy; the area and length of the bone surface of the socket were not significantly altered. Sympathetic denervation thus affects bone resorption within the first few hours after surgery.

Guanethidine sulfate was administered to rats from birth to 14 days of age. Cell counts were carried out in the superior cervical sympathetic ganglion at 30, 45, and 90 days of age. Massive permanent destruction of sympathetic ganglionic cells was demonstrated during the experimental period. Evidence for a natural loss of neurons during the morphogenesis of the superior cervical sympathetic ganglion is presented.

Newt forelimbs were unilaterally amputated and Beta-amino propionitrile (BAPN) was added to the water in which the newts were maintained. Sixty-three days after amputation, animals were injected with either 3H-proline or 3H-lysine. Forelimbs distal to the elbow of both amputated and non-amputated sides were removed 72 hours later. Uptake of 3H-proline and 3H-lysine in whole limbs was assessed by liquid scintillation and in cartilage cells and matrix by autoradiography. Amputation was a potent stimulus to both collagen formation and maturation during regeneration. BAPN reduced the stimulatory effect of amputation on collagen formation but not on its maturation. Collagen synthesis and maturation are independent events and, in intact non-regenerating limbs, BAPN adversely affected collagen maturation while collagen synthesis was unaltered.

Osteoblastic activity in the rat femur was assessed following sympathectomy by injections of guanethidine sulfate from birth to 14 days of age. At ages 30, 45 and 90 days, osteogenesis was monitored by quantitative autoradiography using 3H-proline. Grain counts over periosteal osteoblasts of the femoral diaphysis showed a significant reduction in the uptake of 3H-proline in sympathectomized rats. The results indicate that the sympathetic innervation of bone influences osteoblastic activity and provide support for a role of the autonomic nervous system in the regulation of bone formation.

The uptake of [3H]-proline was monitored by quantitative autoradiography at 30, 45 and 90 days of age. Grain counts in sympathectomized rats did not vary significantly from control values at any time. Thus the sympathetic nervous system does not influence the metabolic activity of these cells, which agrees with morphologic evidence that the innervation of the rat incisor may not be autonomic.

Sympathectomy was carried out in 4-week-old Sprague-Dawley rats by unilateral surgical removal of the superior cervical ganglion. Sham-treated rats served as controls. All rats were injected with tetracycline hydrochloride at surgery as well as 36 hr prior to sacrifice. Rats were killed at 7, 14, or 21 days following sympathectomy. Mandibular periosteal and endosteal surfaces were analyzed by fluorochrome morphometry. Osteoclasts were identified by acid phosphatase staining, and incisor and molar root sockets were analyzed morphometrically. Following sympathectomy, periosteal and endosteal apposition as well as the rate of mineralization were significantly lower. At the same time, a significant increase in the number of osteoclasts per socket as well as in active and inactive bone resorption surfaces was also seen. All parameters, however, returned to normal values 2-3 weeks after sympathectomy. The data provide the first direct quantitative evidence that sympathetic neurons modulate bone resorption and bone remodeling in vivo.