The Journal of comparative neurology
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The spatial distribution and temporal disappearance of Rohon-Beard cells in the spinal cords of larval and newly metamorphosed Rana pipiens were studied histologically to provide a basis for further research dealing with this particular cell type. It was found that a maximum number of approximately 250 Rohon-Beard neurons have differentiated within the spinal cord of Rana pipiens by larval stage I. The majority of these cells are located in the cephalic end of the spinal cord, with a large number found near the boundary of the anterior quarter and the second quarter of the spinal cord. ⋯ Degeneration of the Rohon-Beard cells does not progress cephalocaudally with development, but rather there appears to be a nearly equal proportional loss of Rohon-Beard cells in each quarter of the spinal cord at each of the stages studied. All Rohon-Beard cells present during larval development of Rana pipiens are located in a dorsal position close to the midline. At all ages and in each quarter of the spinal cord there are no significant bilateral differences in number of these cells.
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Transganglionic degeneration in primary sensory neurons (TGD) has been studied with the Fink-Heimer and cupric silver methods in the adult rat after transection of thoracic spinal nerve branches. Degeneration was found in the ipsilateral dorsal horn after 13 to 53 days postoperative survival. It was observed in laminae III and IV, inconsistently in lamina I, but not in lamina II (substantia gelatinosa). ⋯ Transection of the intercostal nerve (ventral ramus) at about the costal angle gave rise to degeneration in the medial two-thirds and transection more distally, at about the mid-clavicular line, in the most medial part of the dorsal horn. The results are in accordance with previous anatomical and physiological studies of the somatotopical organization of the dorsal horn. They clearly show the usefulness of TGD as a tool for analysis of central projections of primary sensory neurons.