Lysophosphatidylcholine disrupts the acrosome of tammar wallaby (Macropus eugenii) spermatozoa

Acrosome stability in the spermatozoa of dasyurid marsupials

The spermatozoa of most marsupials lack nuclear stabilising disulfide-bonded protamines found in eutherian mammals. However, disulfide stabilisation has been observed in the acrosome of macropodid (Macropus eugenii) and phalangerid (Trichosurus vulpecula) marsupials. As a result this organelle, which is normally fragile in eutherian mammals, is robust and able to withstand physical and chemical challenge in these marsupials. The present study examined acrosomal characteristics of the spermatozoa of three dasyurid marsupials; the fat-tailed dunnart (Sminthopsis crassicaudata), eastern quoll (Dasyurus viverrinus) and northern quoll (Dasyurus hallucatus). In all species examined Bryan’s staining demonstrated that significant acrosomal loss occurred following physical challenge with osmotic stress, cryopreservation without cryoprotectant and exposure to detergent (Triton-X). Bromobimane staining indicated that the acrosomes of dasyurids lacked stabilising disulfide bonds. As reported for the wallaby and possum, calcium ionophore (A23187) did not induce the acrosome reaction-like exocytosis in dasyurid spermatozoa but treatment with diacylglycerol (DiC8) caused significant acrosome loss at concentrations similar to those effective for other marsupials. The present study found that the spermatozoa of dasyurids are more sensitive to physical challenge than the previously-studied marsupials and we suggest that this is due to the absence of acrosomal stabilising disulfide bonds.

Antibiotics for the preservation of koala (Phascolarctos cinereus) semen

AIM

To determine the normal microbial flora of the koala ejaculate and prepuce in order to select appropriate antibiotics for addition into diluents designed for the preservation of semen.

PROCEDURE

Bacteriological samples of the koala prepuce (n = 12) and ejaculate (n = 20) were submitted for microbial culture and sensitivity testing. Microbial flora of ejaculates collected by electroejaculation and artificial vagina were compared. The effects of varying concentrations of penicillin G and gentamicin on sperm motility and on the growth of bacteria in diluted semen stored at room temperature and 16 degrees C over a 24 h period were investigated.

RESULTS

A range of bacteria was isolated from the koala prepuce and ejaculate. The predominant organisms in semen collected by electroejaculation and artificial vagina were Corynebacterium spp, none of which could be assigned to any recognised species. The addition of penicillin G and gentamicin to a PBS-based diluent at dose rates of 1000 to 2000 IU/mL and 100 to 200 micrograms/mL respectively, resulted in no adverse effect on sperm motility over a 24 h incubation period. Penicillin G (1000 IU/mL) and gentamicin (100 micrograms/mL) prevented growth of bacterial contaminants in diluted koala semen.

CONCLUSION

By controlling the growth of bacteria in extended koala semen, penicillin G and gentamicin are likely to lengthen the period by which spermatozoa can be stored at 16 degrees C and reduce the possibility of disease transmission during artificial insemination procedures.

Collection and short-term preservation of semen from free-ranging eastern grey kangaroos (Macropus giganteus: Macropodidae)

OBJECTIVES

To evaluate electro-ejaculation of free-range eastern grey kangaroos in the field and assess the efficacy of four diluents to preserve sperm motility over a 48-h period at 5 degrees C. PROCEDURE AND DESIGN: Under gaseous anaesthesia, 25 free-range kangaroos were electro-ejaculated and characteristics of the ejaculate noted. Spermatozoa obtained from eight ejaculates were diluted in phosphate buffered saline containing various combinations of egg yolk and glucose and refrigerated at 5 degrees C for 48 h.

RESULTS

Spermatozoa were recovered from 24 of 28 ejaculates. Mean (+/- SEM) semen volume (mL) and pH were 25.0 +/- 1.9 and 7.1 +/- 0.1 respectively. The forward motility (%), rate of movement of sperm (0 to 5) and sperm concentration (x 10(6)/mL) were 77.4 +/- 1.5, 3.8 +/- 0.9 and 31.2 +/- 7.3 respectively. There was no significant difference between the four diluents in their ability to maintain forward motility of spermatozoa over 48 h. However, rate of movement over the same period was significantly (P < 0.01) improved when sperm were diluted in phosphate buffered saline containing 10% egg yolk.

CONCLUSIONS

Electro-ejaculation is a safe and reliable method for collecting semen from free-ranging eastern grey kangaroos. Preliminary attempts at short-term preservation showed that the motility of kangaroo spermatozoa could be adequately stored for 24 h and that the addition of egg yolk to the semen diluent was beneficial for improving the rate of sperm movement.

Study of the acrosome reaction and the fertilizing ability of hamster epididymal cauda spermatozoa treated with antibodies against phospholipase A2 and/or lysophosphatidylcholine

The present report describes experiments in vitro that were designed to evaluate the involvement of phospholipase A2 (PLA2) in the acrosome reaction of mammalian sperm and the interaction of gametes. Hamster spermatozoa were incubated in a defined medium (TALP) to induce capacitation and the acrosome reaction. This medium was supplemented with antibodies against porcine pancreatic PLA2 and/or lysophosphatidylcholine (LPC). For in vitro fertilization, spermatozoa and/or oocytes were incubated in TALP medium that contained PLA2-specific antibodies, LPC, or antibodies plus LPC. The antibodies inhibited the acrosome reaction in a dose-dependent manner, without any effect on sperm motility or hyperactivation. These antibodies also inhibited fertilization in vitro. LPC, a product of the reaction catalysed by PLA2, speeds up and synchronizes the acrosome reaction and facilitates penetration of the zona pellucida by spermatozoa, the fusion process and polyspermy. The results of addition of the antibodies plus LPC showed that LPC is able to reverse the inhibitory effects of the antibodies on the acrosome reaction and fertilization. It is possible that endogenous PLA2 plays a role in the final stages of the acrosome reaction and the interaction of gametes, perhaps through one of its reaction products, LPC. The role of LPC might be to stimulate the fertilizing ability of spermatozoa, as well as to induce changes in the zona pellucida and the oolemma that allow sperm-egg fusion. Thus, it seems possible that PLA2 and one of its reaction products might contribute to membrane-fusion events during mammalian fertilization.

Lysophosphatidylcholine treatment allows interspecies fertilization of hamster oocytes with zona pellucida by human spermatozoa

The study of interspecific gamete interactions has been improved by the use of in vitro fertilization techniques. Zona pellucida is at the cellular level the main barrier to cross-fertilization. Moreover, there are several cases in which the heterologous spermatozoa fail to enter the cytoplasm of zona-free oocytes, emphasizing the notion that another important barrier exists to cross-fertilization at the egg plasma membrane level. We report here a simple method to fertilize hamster oocytes with zona pellucida by human spermatozoa. We used lysophosphatidylcholine (LPC), a fusogenic agent, to treat spermatozoa, spermatozoa and zona-intact oocytes, or zona-intact oocytes alone. This molecule allows the penetration of hamster oocytes zona by human spermatozoa. Our results suggest that LPC modifies the zona pellucida of oocytes and the plasma membrane of both gametes in vitro, favouring sperm penetration through the zona pellucida and gamete fusion.