Akiyoshi Matsumura

Cross-Sectional Morphology of the Femoral Neck of Wild Chimpanzees

To understand the mechanical effects of different modes of locomotion on the femoral neck of chimpanzees, we investigated the cross-sectional morphology of the femoral neck of 4 chimpanzees (Pan troglodytes schweinfurthii) collected from the Mahale Mountains, Tanzania. We performed serial computed tomography (CT) scans of the neck from the femoral head to the base of the neck perpendicular to the long axis of the neck. We measured the cortical thickness of the serial 5 cross sections of the neck region every 45° around the circumference, i.e., 8 points per section, and examined the cross-sectional properties of the mid-section. When we compared the superior and inferior parts of the cortical thickness of the femoral neck, the inferior part exhibited the greatest cortical thickness whereas the superior part had the smallest values in every specimen. Researchers have also observed such regional differences between superior and inferior cortical thicknesses in bipedal humans and other primates, although these differences are not as large in the chimpanzee as in bipedal hominini. The present study differed from the past study on hominini and chimpanzees in that the superior anterior (SA) part exhibited greater cortical thickness in chimpanzees. We believe these observations reflect the structural strengthening of parts of the chimpanzee femoral neck that is needed to accommodate the mechanical loads imposed by arboreal vertical climbing and terrestrial quadrupedal and bipedal locomotion.

Microtubule bundles in fish cerebellar Purkinje cells

SummaryThe initial axon segments and the cell bodies of Purkinje cells were examined in electron microscopic serial sections and toluidine blue semithin sections of goldfish cerebellum. We observed two characteristic cytoplasmic features different from those of other vertebrate neurons. 1. The areas of Nissl substance and Golgi apparatus are sharply divided in the periphery and center of the cytoplasm. 2. Microtubules fasciculated by cross-bridges in the axon hillock and initial axon segment remain bundled in the perikaryon, pass near the eccentric nucleus, and enter into the Golgi area of the central cytoplasm, where they are surrounded by mitochondria. We suggest that the intracellular fasciculated microtubules may establish a prepared pathway for fast anterograde and retrograde transport to and from the Golgi area of the cell body.

Muscle Fibre Composition and Innervation Ratios of the Extensor Digitorum and Extensor Hallucis Brevis Muscles in the Crab-Eating Macaque (Macaca fascicularis)

The morphological and functional characteristics of the extensor digitorum and hallucis brevis muscles, the sole intrinsic muscles of the dorsum of the foot in the macaque, were investigated through dissection, the examination of muscle fibre composition, and counts of axon numbers. The total number of muscle fibers contained within the extensor digitorum (EHB) and extensor hallucis brevis (EDB) was almost 21,100. The population ratios of the three muscle fibre types of white, intermediate and red were 39.23 and 38%, respectively, for EDB and 40, 23 and 37%, respectively, for EHB. The mean cross-sectional area of each fibre type (white, intermediate, red) tended to be larger in the EHB (2,098, 1,480 and 911 microns2) than in the EDB (1,695, 1,310 and 822 microns2) and the value were significantly different for white fibres of males. The percentage area of the three muscle fibre types and the ratio of the white, intermediate and red areas, were similar between the EHB (55, 23 and 22%, respectively) and the EDB (52, 23 and 25%, respectively). The white area was dominant with the value showing a somewhat larger figure in the EHB compared to that of the EDB. The number of motor units was estimated to be 197-234 on average and the innervation ratio was calculated as between 91 and 109. These results suggest that the muscle fibre composition and innervation ratio of the EHB and EDB, especially the EHB, might relate to the arboreal locomotion of the crab-eating macaque.