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1 Harvard Program in Urology
(Longwood Area) and the Laboratory of
Human Reproduction and Reproductive
Biology, Harvard Medical School, Boston,
Massachusetts
2 Division of
Laboratory Animal Medicine, Massachusetts
Institute of Technology,
Cambridge, Massachusetts
3 Department of Physics, Massachusetts
Institute of Technology,
Cambridge, Massachusetts
Ultrastructural characteristics of the acrosome,
postacrosomal region, plasma membrane, and
cytoplasmic droplet in spermatozoa taken from
the caput, corpus, and cauda epididymidis of the
pigtailed macaque are described. The subdivision of the postacrosomal region into an anterior and a posterior segment is demonstrated. Maturational changes manifest in the
caudal shift of the cytoplasmic droplet and
swelling of the plasma membrane are observed
during epididymal transit in this species and
are similar to those reported for other monkeys.
However, the changes in the rostral segment of
the acrosome are more striking than any in
other Old World monkeys studied to date. In the
caput epididymidis, the acrosome is asymmetric
because its apical segment extends well beyond the rostral edge of the nucleus and folds
under it, giving the acrosome a small but distinct hook shape in sagittal section. In the corpus and cauda, the acrosome contracts down
over the nucleus, resulting in the loss of the
asymmetry of the contours of the sperm head,
and the distinctive hook-shaped apical segment
of the acrosome is no longer seen in sagittal
section. On the basis of these findings, the pigtailed macaque appears to be a suitable primate
model for morphologic analysis of structural
variables during epididymal sperm maturation.
Key words: ultrastructure, sperm maturation, spermatozoa, epididymis, monkey, epididymal sperm
Submitted on July 14, 1980
Revised on September 19, 1980
Accepted on October 16, 1980
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