In the golden hamster, Chinese hamster, guinea-pig and Libyan jird, a morphological change is evident in the acrosomes of spermatozoa that have reached the ampulla of the Fallopian tube, and spermatozoa that have passed into or through the zona pellucida of the egg appear to lack acrosomes altogether (Austin & Bishop, 1958a, b). Consistently, both Moricard (1960) and Hadek (1963), working with the electron microscope, reported lack of acrosome in rabbit spermatozoa that have attained the perivitelline space, though Hadek described a spermatozoon in the thickness of the zona pellucida that still showed remnants of acrosomal membranes. On the other hand, Adams & Chang (1962) were unable to discern any change in the acrosomes of living rabbit spermatozoa obtained from the Fallopian tube, and Bedford (1963) concluded that the morphological changes he detected in the acrosomes of tubal and uterine rabbit
C. R. AUSTIN
Spermatozoa were found to persist for 6 days in the uterine lumen of rabbits. They were also seen in the uterine glands in the greater horseshoe bat, the common pipistrelle bat, the guinea-pig, the stoat, the hedgehog and the mole.
Sperm heads were identified in the uterine-gland mucosa in two guinea-pigs, and additional observations are reported on their presence in the Fallopian-tube mucosa in the greater horseshoe bat and the rat. In both regions, the spermatozoa were considered to lie within cells. There was evidence of dissolution of spermatozoa in the uterine glands of the horseshoe bat, and in the Fallopian-tube mucosa of the pipistrelle bat and the rat.
The uterus of one guinea-pig had localized regions of leucocytosis, probably owing to infection; in this specimen, many leucocytes containing spermatozoa were found within some uterine glands and in the interstitial tissues at distances from the glands.
C. R. AUSTIN
Physiological Laboratory, University of Cambridge
Fertilization entails the union of egg and spermatozoon, which, as first clearly shown by Szollosi & Ris (1961) in a mammal and Colwin & Colwin (1961) in an invertebrate organism, requires the fusion of the limiting membranes of the two cells so that they come to form a single cell. The new entity is bounded by a membrane which at least initially is a composite or mosaic of the two gamete membranes. Before gamete union can occur the spermatozoon must penetrate the investments enclosing the egg, and this requires the release of lytic enzymes carried in the acrosome. Release is effected by the acrosome reaction, which takes place by fusion between acrosomal and plasma membranes. The acrosome reaction must itself be preceded by changes in the surface properties of the spermatozoon, known collectively as capacitation, and this is likely to involve also changes
C. R. AUSTIN and C. L. BAKER
The spermatozoon of the dwarf siren Pseudobranchus striatus axanthus, Netting & Goin, 1942, an aquatic salamander abundant in central Florida, does not seem to have been described before despite its unusual and interesting form. It is comparatively large, with a length of 280 to 300 μ, and consists of a greatly elongated nucleus and two axial filaments, each of the filaments carrying an undulating membrane bordered by a flagellum. Several toads and salamanders are known to have spermatozoa equipped with a single undulating membrane; the spermatozoa of Pseudobranchus (like those of its close relatives Siren lacertina and S. intermedia: C. L. B., unpublished data) is remarkable for having two of these structures.
The two axial filaments, which are about 1 μ thick, extend over almost the whole length
J. D. ROUSSEL and C. R. AUSTIN
As early as 1897, Davenport found that human spermatozoa would survive freezing to − 17° C, but little progress in the freeze-preservation of spermatozoa was made until 1949 when Polge, Smith & Parkes reported that the use of glycerol made possible the revival of motility in fowl spermatozoa kept at − 79° C for long periods of time. Later, freeze-preservation of the semen of several animals became a routine procedure (see Sherman, 1964). Success, however, appeared to depend upon closely controlled rates of freezing and thawing, which de-manded the use of specialized equipment. It was first shown by Sherman (1963) with human semen, and by Roussel, Kellgren & Patrick (1964) with bovine semen, that successful freezing and storage of spermatozoa in liquid nitrogen vapour for indefinite periods of time could be achieved without instrumentation. The present report describes the employment of this procedure for primate semen.
W. E. GREER, J. D. ROUSSEL and C. R. AUSTIN
Monkey semen characteristically coagulates during ejaculation, and samples obtained by electrical stimulation consist wholly or largely of a rubbery mass. Some spontaneous dissolution occurs when the ejaculate is held in vitro at room or body temperature, but more than half the mass, usually about 75%, remains unchanged. Use of monkey semen for laboratory studies or for artificial insemination is hampered by this feature. To some extent, the trouble can be remedied by the use of proteolytic enzymes, of which trypsin seems to be the least deleterious to sperm viability (Roussel & Austin, 1967), but the presence of trypsin raises problems for many biochemical studies. Accordingly, the possibility was investigated that surgical removal of the coagulum-producing gland from the male tract might result in the ejaculation of coagulum-free semen, without seriously interfering with the volume and other semen charac