Schematic drawings of lumbosacral enlargement sections in cat, monkey and human aligned via internal landmarks.

<p>Each schematic drawing represents the right side of every third section in a 1:5 series of 80μm sections (M5) or in a 1:6 80μm series in all 3 human cases. Cat data, with motoneuronal cell groups serving functionally distinct muscles marked by distinct colors, was adapted with permission from Vanderhorst and Holstege [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177243#pone.0177243.ref013" target="_blank">13</a>]. In all 3 species, series were aligned according to rostral (level 0) and caudal (level 100) anatomical landmarks as defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177243#pone.0177243.g001" target="_blank">Fig 1</a>. Lengths signify distances calculated in centimeters from level 0 to 100, based upon the thickness of each section and the number of sections, and after corrections for tissue shrinkage. Note that consistent changes in ventral horn shape are congruent across all 3 species, and among the 3 human subjects, despite obvious differences in size.</p

Comparison of three approaches to align the distribution of non-human primate lumbosacral motoneurons.

<p>Rostrocaudal distribution of iliopsoas, semimembranosus, and external sphincter motoneurons in 5 monkeys. Spinal cords were aligned among cases based upon (A) absolute length (millimeter distance calculated from the thickness of each section and the number of sections); (B) segmental level, starting at L4, and (C) internal landmarks representing level 0 (defined by the ventrolateral edge of the ventral horn extending laterally and representing the presence the most rostral leg motoneurons) and level 100 (defined by the ventral gray border changing from a curved protrusion to a straight edge or Onuf’s nucleus touching the ventral white matter. Note the size differences in (A) and the segmental differences in (B), which contrast the similarity in distribution of motoneurons across cases in (C).</p

Identification of rostral and caudal landmarks in the lumbosacral enlargement in rhesus monkey and humans.

<p>(A-C) Retrogradely labeled motoneurons in the rhesus monkey lumbosacral cord following CTb injections into the (A) iliopsoas, (B) semimembranosus, and (C) external sphincter muscle. Note that the iliopsoas motoneuron pool demarcates the rostral end of the enlargement, where the ventral horn extends laterally. The caudal landmark is demarcated by pelvic floor motoneurons of the external sphincter (Onuf’s nucleus) touching the edge of the ventral gray matter. (D-F) ChAT-IR neurons in the human lumbosacral cord (87 year old woman with Dementia with Lewy Bodies). Panels (D-F) are homologous to panels (A-C) in the monkey. Note that the changes in shape of the ventral horn, demarcating the rostral and caudal landmarks, can be identified in the human spinal cord. Similar to monkey, these changes in shape are determined by (ChAT-IR) motoneurons, similar to the rhesus monkey. Bars in (A-C), and (D-F) = 500μm.</p