[Relationship between neuronal size and axonal length in chick propriospinal neurons].
In order to investigate the relationship between neuronal size and axonal length, we compared the size of chick propriospinal neurons in several segmental levels. As the index of neuron size, the cross sectional areas of somata were measured. After unilateral implantation of solidified HRP into the lumbar enlargement (2 cases) or the cervical enlargement (1 case) in the 2-4 day post-hatch chick under Nembutal anesthesia, propriospinal neurons projecting to the enlargement were visualized by TMB method. Labeled cells found in complete serial transverse sections were all traced onto tracing papers put on photomicrographs under examination with the microscope (Fig. 2). In several successive sections in the cervical cord, the cervical enlargement, the lumbar and the sacral cord, the cross sectional areas of their 3601 somata were measured on traced drawings of final magnification X243 by means of a computer system graphic analyzer (Cosmo Zone, Nikon) (Fig. 1). As a control case, cross sectional areas of somata were also measured in Nissl preparations in laminae V-VIII, where vast majority of propriospinal neurons are located, and also lamina IX. In Nissl preparations, the cross sectional areas of neurons in laminae V-VIII had a wide range distribution from 50 to 1600 micron 2. Over 90% of them were distributed from 50 to 600 micron 2. Among them, the neurons with somata of 150-250 micron 2 were most numerous. The distribution pattern was almost the same in all segments examined. The cross sectional areas of neurons in lamina IX were also distributed in a wide range from 150 to 1600 micron 2 (Fig. 3).(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001369:Axons; D002645:Chickens; D006735:Horseradish Peroxidase; D009562:Nissl Bodies; D013116:Spinal Cord / Q000166:cytology*; D013194:Staining and Labeling / Q000379:methods
D006735:Horseradish Peroxidase