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Biology of Reproduction, Vol 14, 118-142, Copyright © 1976 by Society for the Study of Reproduction
1 Departments of Obstetrics and Gynecology and Anatomy,
Cornell University Medical College,
New York, N. Y. 10021 In order to elucidate the way in which the epididymis and vas deferens first react to and dispose
of the continuous influx of spermatozoa from the testis after vasectomy, the effects of vas
obstruction have been studied in the rabbit, rhesus monkey, hamster, and rat. Initially,
spermatozoa accumulated in and began to distend the vas deferens and the distal portion of the
epididymis, but the response thereafter varied from species to species and sometimes among
individuals within a species. The distensibility of the distal segment of the rabbit tract seemed to
ensure its integrity for 24 weeks or more, but focal ruptures of the duct wall (granulomata)
appeared in one or more regions of the epididymis by 32 weeks in most rabbits. In the monkey,
discrete granulomata developed along the vas deferens and/or in the cauda epididymidis only 5-6
weeks after vasectomy in some individuals, and this coincided with the subsidence of a small but
palpable enlargement of the cauda epididymidis. Macroscopic granulomata erupted in one or more
regions of the hamster epididymis within 8 weeks and some 30 percent of these animals displayed a
terminal cyst at the point of vasal obstruction. In the rat, the consistent early development of a
similar eruption at this site seems to alleviate sperm build-up proximal to the obstruction and, as a
probable consequence, epididymal granulomata appeared less frequently in this species. The -S-S crosslinked keratinoid character of the nucleus, and, in the tail, connecting piece,
dense fibers, sheath and outer membrane of the mitochondria, renders the normal mammalian
spermatozoon highly resistant to digestion and breakdown. This was reflected after vasectomy in
the persistence of the spermatozoa which did not undergo dissolution in the duct lumen or in the
granulomata. Neither were spermatozoa observed to be ingested by the intact epithelium of the vas
deferens and epididymis. Their disposal depends on their ingestion by leucocytes, which invade the
duct first via the granulomata and then migrate within the tract, and, particularly within the
terminal vasal cysts, by epithelioid cells which bound the periphery of such sites. Obstruction of the vas deferens per se did not elicit early histological changes in the testis.
However, some ipsi-lateral disruption of the seminiferous epithelium occurred consistently in
concert with granulomata and/or distension of the caput or corpus epididymidis. Patchy
degeneration of the seminiferous epithelium was evident also in 5 of 10 rats and all five rabbits
vasectomized unilaterally>1 year earlier. The persistent fertility of rats and rabbits>1 year after unilateral vasectomy shows that
vasectomy has no general immunologically-mediated suppressive effect on the potential fertility of
these species. The results are discussed in terms of the events which may occur initially after vasectomy in
man, and the relevance of different animals as models for vasectomy research.
Note:
ACKNOWLEDGMENTS
Two of the long-term rabbit tracts were donated
by Dr. R. P. Millar, U. of Capetown.
I thank Helen Hirschbein, Emelda Sanidad, Mary
Jane Bent and Miu Ying Kiu and Erica Krull for their
technical assistance in various phases of the study, and
Jill Spiller for editing the manuscript. This work was
supported initially by N.I.H. contract no. 70-2143 and
later by N.I.H. grant HD-07527, and by a grant from
the Ford Foundation.
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