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J. F. HARTMANN and C. F. HUTCHISON

Summary.

The studies reported here demonstrate that isolated hamster zonae pellucidae affect the binding between capacitated hamster spermatozoa and eggs included in the same drop. Mouse zonae pellucidae fail to affect binding between hamster gametes. These results suggest that binding, which occurs only between homologous spermatozoa and isolated zonae pellucidae causes a factor (S1 factor) to be released. The SI factor is diffusible and influences the two successive binding steps (B1 and B2) previously shown to occur between capacitated spermatozoa and eggs. The B2 step is delayed by the action of the SI factor during the early part of the interval between B1 and B2 suggesting that the effect may be mediated through Bl. It is proposed that the SI factor is also released during the first binding interaction (B1) between the spermatozoa and the egg which appears to be an analogous but terminated form of the binding to the isolated zona pellucida. The data are consistent with the possibility that the B1 step is terminated by the product of the interaction between the S1 factor and a factor from the vitellus or perivitelline space.

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J. F. HARTMANN and C. F. HUTCHISON

In recent reports from this laboratory, it has been shown that a series of complex events occur at the gamete surfaces after spermatozoa contact the egg (Hartmann, Gwatkin & Hutchison, 1972; Hartmann & Hutchison, 1973, 1974a, b). The relatively long period between the B1 and B2 bindings between the gamete surfaces suggests that changes occur which are a prelude to the penetration of the zona pellucida. Our earlier studies suggested that after pre-exposure to a population of eggs the spermatozoa were altered by the action of a vitelline factor in a manner which enabled them to bind sooner to a second population of eggs (Hartmann et al., 1972; Hartmann & Hutchison, 1974a). In this report, it will be shown that following B1 the zona pellucida is also altered in a manner which apparently prepares it for the final binding step (B2).

Spermatozoa were collected from the caudal portion of the

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J. F. HARTMANN and C. F. HUTCHISON

Summary.

The pre-penetration contact interactions between eggs and spermatozoa of the golden hamster were studied in vitro. The spermatozoa arrive at the surface of the egg and become loosely associated with the egg (`attachment'). `Binding', the species-specific tight association between gametes, occurs in two steps. The first (B1) occurs within 2 to 3 min after the spermatozoa and eggs are mixed and is rapidly terminated. By contrast, binding to the isolated zona pellucida is not terminated. Termination must therefore involve a factor originating from the vitellus or perivitelline space. Experiments with the synthetic trypsin inhibitor, p-aminobenzamidine (pABA), suggest that termination involves a protease, since B1 was enhanced when eggs were exposed to the inhibitor during the B1 phase. Following the termination of B1, in the normal interaction, the spermatozoa remain attached and apparently are conditioned through the action of the vitelline factor to bind a second time. This binding (B2) occurs about 30 min after B1 termination. The B2 process may involve the acrosomal proteinase of the sperm head, since B2 was inhibited by treating spermatozoa with pABA. In contrast to the B2 site, B1 and binding to isolated zonae pellucidae were not blocked by pABA treatment of spermatozoa. This suggests that the binding phases, B1 and B2, occur at different sperm sites.

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R. B. L. GWATKIN, D. T. WILLIAMS, J. F. HARTMANN and M. KNIAZUK

Summary.

The cortical granules of hamster ova were ruptured in vitro by electrical stimulation (standard treatment was 150 V, 1·0 msec). Approximately 8 min were required for the cortical granule material so released to induce a complete zona reaction. The active material from the cortical granules was released into the medium from vitelli and was shown to act directly on the zona pellucida and on mouse, as well as on hamster, ova, i.e. its action is not species specific. The action of the cortical granule material was reversed by trypsin inhibitors. Such a tryspin-like protease, causing the zona reaction, was also released from vitelli by spermatozoa.