Abstract:
The closure of the ductus arteriosus (DA) of 31 indigenous South African
goats, whose ages ranged from 30 days prenatal to 60 days postnatal, were
studied at an altitude of 1514 m above sea level by vascular injection
as well as histologically and ultrastructurally. The vascular injection
results showed that functional occlusion started from the pulmonary end
of the DA in kids 6 days old and progressed to the aortic end in kids 8
days old. Histologically, anatomical obliteration was observed in kids
from 35 days of age. The functional closure was preceded by enlargement
of the subendothelial region, progressive intimal thickening, presence
of subendothelial vacuolization and endothelial detachment. There was
radial orientation of the subintimal smooth muscle cells and subsequent
migration towards the intima. The inner tunica media contained mast
cells and areas of cytolysis. Following functional closure, the
subendothelial region showed migrating subintimal smooth muscle cells
with extensive cytoplasmic processes and, ultrastructurally a fragmented
internal elastic lamina. In 15-day-old kids there were prominent,
progressively enlarged cisternae of the rough endoplasmic reticulum and
numerous free, dispersed ribosomes. In kids 19 and 25 days old, there
was, additionally, rarefaction of the cell cytoplasm and appearance of
intracellular myofibrils and extra cellular collagen in the surrounding
amorphous matrix, which culminated in the complete anatomical closure of
the DA in 35-day-old kids.
