Rouleau formation and fertility of spermatozoa in guinea pigs treated with cyproterone acetate

Postcopulatory sexual selection is associated with sperm aggregate quality in Peromyscus mice

In some species, sperm form coordinated groups that are hypothesized to improve their swimming performance in competitive contexts or to navigate through the viscous fluids of the female reproductive tract. Here we investigate sperm aggregation across closely related species of Peromyscus mice that naturally vary by mating system to test the predictions that sperm aggregates 1) are faster than solitary sperm in species that females mate multiply to aid cells in sperm competition, and 2) outperform solitary sperm cells in viscous environments. We find significant variation in the size of sperm aggregates, which negatively associates with relative testis mass, a proxy for sperm competition risk, suggesting that postcopulatory sexual selection has a stabilizing effect on sperm group size. Moreover, our results show that sperm aggregates are faster than solitary sperm in some, but not all, species, and this can vary by fluid viscosity. Of the two species that produce the largest and most frequent groups, we find that sperm aggregates from the promiscuous P. maniculatus are faster than solitary sperm in every experimentally viscous environment but aggregation provides no such kinematic advantage under these same conditions for the monogamous P. polionotus. The reduced performance of P. polionotus aggregates is associated with less efficient aggregate geometry and the inclusion of immotile or morphological abnormal sperm. Our cross-species comparison yields insight into the evolution of sperm social behaviors, provides evidence of extensive variation in the Peromyscus lineage, and reveals that differences in sperm aggregate quality associate with postcopulatory sexual selection.

Binding of secreted glycoproteins to spermatozoa in the mammalian epididymis: a fine-structure autoradiographic study

Mouse and guinea pig epididymal tissues have been investigated by light and electron microscopic autoradiography after long intervals ranging from 24 h to 5 days postinjection (p.i.) of the glycoprotein precursors, L-fucose-6-3H or D-glucosamine-1-3H. Using modified fixations to enhance glycoprotein preservation in situ, we found intense labelling of luminal contents in at least some of the epididymal segments after all the intervals investigated. At 24 h p.i., the label in guinea pig was associated with spermatozoa during remodelling of the acrosome in segment II, and at 3 days p.i., radioactivity was trapped within sperm head associations ("rouleaux") in segment IV of the epididymis. At this time, similar rouleau labelling extended from segment IV to segment VIII. In mouse, the luminal contents of the cauda epididymis were still intensely labelled at 5 days p.i.; analysis of the electron microscopic autoradiograms showed that relative grain concentration over the spermatozoa was twice that of the epididymal plasma. This concentration was especially elevated in the region of the sperm head. These findings taken together were interpreted as the binding of secreted epididymal glycoproteins to spermatozoa during sperm transit through the epididymis. In contrast to luminal contents, the labelling of the epididymal epithelium was generally lower, except on the clear cells which showed more pronounced labelling than the neighboring principal cells in mouse cauda epididymis at 5 days p.i. This label probably originated from the resorption of luminal glycoproteins.

Initial experiments with cyproterone acetate and 1-amino-3-chloro-2-propanol hydrochloride in the male Virginia opossum (Didelphis virginiana)

Cyproterone acetate (CA) was toxic for Didelphis virginiana at a dose range of 22-28 mg/kg IM. A loss of spermatozoal pairing int the cauda epididymidis did not occur until 2 wk after testicular degeneration caused by CA. The isomers of 1-amino-3-chloro-2-propanol hydrochloride (CL 88,236 and CL 88,237) were well tolerated by the opossum at doses up to 30 mg/kg IM. After 8 days of CL 88,236 and CL 88,237 treatment there was no effect on spermatozoal pairing in the cauda epididymidis or on the seminiferous epithelium.

Studies on zonation in the epididymis of the guinea pig. I. Ultrastructural and biochemical analysis of the zone rich in large lipid droplets (zone II)

In the epididymis of the guinea pig, zone II exhibits striking histological features that distinguish it readily from the other six regions of the epididymis. At the light microscope level, the pseudostratified epithelium of zone II is characterized by tall principal cells that are densely packed with large, intensely staining granules or droplets ranging up to 8 mu in diameter. At the electron microscope level, the principal cells exhibit numerous large lipid droplets and abundant agranular endoplasmic reticulum, which is frequently arranged in concentric whorls around one or more of the droplets. Quantitative biochemical studies comparing zone II with zones I and III show that zone II contains 2.5 - 3-fold more cholesterol and a significantly greater amount of cholesterol ester than the other two zones. These data indicate that the epididymal duct of the guinea pig includes a clearly defined region of epithelial cells possessing ultrastructural and biochemical characteristics consistent with steroidogenic activity. The potential significance of these observations to the epididymal physiology of the guinea pig and epididymal physiology in general is discussed.