Okamoto N

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.

Atrioventricular Septal Defect in Rat Fetuses Induced by Administration of Bisdiamine

ABSTRACT A high incidence of atrioventricular septal defect was induced in rat fetuses by administration of N, N ‐his (dichloroacetyl)‐1, 8‐octamethylenediamine, bisdiamine, to pregnant Donryu rats. Induction of atrioventricular septal defect was highly dependent on day of bisdiamine administration. When bisdiamine was administered singly on day 9.4 of gestation or consecutively on days 9 and 10 of gestation, the incidence of atrioventricular septal defect in fetuses increased. Survival rate decreased with increase in the amount of bisdiamine administered. Normalized incidence 5 for atrioventricular septal defect, which was calculated as a product of incidence and survival rate, was as high as 54.5% when 175 mg bisdiamine was administered on day 9.4 of gestation. Atrioventricular septal defect thus formed was of the complete type associated with either persistent truncus arteriosus or tetralogy of Fallot, indicating that the conotruncal portion was unexceptionally malformed. The present model is useful for analysis of development and pathogenesis of atrioventricular septal defect and also contributes to clarifying the normal development of atrioventricular valves and septa.

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.