Naotaka Akimoto

Distribution of the neural crest cells in the heart of birds: a three dimensional analysis.

SummaryThe distribution of neural crest derived cells (NC) in the heart of quail-chick chimeric embryos was analyzed three-dimensionally after computer reconstruction. During the division of the truncus arteriosus into the aorta and the pulmonary trunk, ventral and dorsal columns of NC-derived cells were found in the truncal swellings. These columns were elongations from the aorticopulmonary (AP) septum. The dorsal column extended more proximally than did the ventral column. Around hatching, NC-derived cells located between the proximal aorta and the pulmonary trunk, differentiated into cartilage and connective tissue. They formed a part of the cardiac skeleton. A small number of NC-derived cells were scattered in the cusps of the arterial valves. Cells derived from the right NC were located around the aorta and the right arch arteries but not around the distal pulmonary trunk and the left arch arteries. At the proximal level, cells derived from the rigth NC were located in both the dorsal and ventral columns. These results suggest that the AP septum is mainly formed by NC-derived cells, right and left NC cells migrating into assigned areas in the heart. Location of two columns of NC-derived cells may support a translocation hypothesis for the AP septum during truncal division.

Formal genesis of the outflow tracts of the heart revisited: previous works in the light of recent observations.

The formal genesis of the great arteries continues to be controversial due to the lack of consensus of septation of the developing outflow tract. In order to make it clear how the great arteries are generated, we have re‐examined our previous papers which emphasized the formation of the aorta and pulmonary trunk, concept of the aorticopulmonary septum, formation of the leaflets of semilunar valves, morphogenesis of the crista supraventricularis, programmed cell death and rotation of the outflow tract. In the present paper, we compare outcomes gained from the re‐examination of our previous papers with prevalent interpretations of the arterial trunk. We obtained conclusions as follows: (i) The elongation of the fourth and sixth aortic arch arteries, which sprout from the wall of the aortic sac at the expense of the distal truncus, contributes to the formation of the aorta and pulmonary trunk; (ii) Smooth muscle cells of the tunica media of the arterial trunks do not arise from the transformation of the myocardial cells of the truncus wall (not ‘arterialization’); (iii) Truncus swellings are divided into two parts: distal and proximal. The former contributes to the separation of the orifices of arterial trunks (‘aorticopulmonary septum’). The latter contributes to the formation of the leaflets of the semilunar valves of the aorta and pulmonary trunk; (iv) The origin of the myocardial cells of the crista supraventricularis is a wall of the conus originated from secondary/anterior heart fields; and (v) There has been no acceptable proof that rotation and counterclockwise rotation are involved.

Prune Belly Syndrome: Report of Twelve Autopsy Cases and Possible Pathogenesis

Abstract Twelve autopsy cases (9 males, 3 females) of the prune belly syndrome are presented. Principal anomalies of this syndrome are a prune‐like abdominal feature and a giant bladder. Urethral atresia was observed in most but two cases. Imperforate anus and rectovesical fistula were observed in 8 and 7 cases respectively. Associated anomalies were those which may or may not be embryologically related to the principal anomalies.

Ultrastructure of the Adenohypophysis in a Case of Cyclopia

The adenohypophysis of a newborn with cyclopia was examined by electron microscopy. The hypophysis was normal in size and shape in the present case. Electron microscopy, however, showed degenerating cells in the adenohypophysis. These cells had small number of granules and cytoplasmic organelles, and the concentric membranous structure, but were not considered as necrotic cells. These findings may indicate overproduction of hormones by the damage of the negative feedback system. No remarkable change, however, was observed in the endocrine organs by light microscopy. Thus, the possible disorder of the hormone production might not be severe enough to cause abnormal formation of the endocrine system in the present case.