In vitro capacitation of fresh, chilled and frozen-thawed dog spermatozoa assessed by the chloretetracycline assay and changes in motility patterns

The effect of preservation on capacitation status of dog spermatozoa was investigated. Split ejaculates from six dogs were assessed as fresh, chilled for 24 h and rewarmed, and frozen-thawed samples. Capacitation-like status was assessed using the chlortetracycline (CTC)-assay and the measurement of sperm motility patterns using a computer-assisted sperm analyzer. Evaluations were performed on washed spermatozoa immediately after dilution in a Tris-fructose-citrate buffer (TFC) or in canine capacitation medium (CCM), and at 2-h intervals during 8 h of incubation in 5% CO2 in air, at 37 degrees C. Preservation decreased significantly the proportion of uncapacitated spermatozoa. In TFC, at hour 0, chilled-rewarmed and frozen-thawed samples had a significantly lower proportion of uncapacitated, viable spermatozoa than the fresh samples (P<0.05) according to the CTC-assay. The time course of capacitation was accelerated in the preserved samples, compared to the fresh ones. During incubation in CCM, the mean time from hour 0 to when, according to the CTC-assay, the highest proportion of capacitated spermatozoawas present in the samples (time-to-peak), was 4 h for fresh and 2 h for chilled-rewarmed and frozen-thawed samples (P<0.1). The highest values for curvilinear line velocity (VCL) and lateral head displacement (LHD), thought to be descriptive of sperm hyperactivation, were also observed 4 and 2 h after incubation began, in the fresh and the preserved samples, respectively. The difference in time-to-peak for VCL and LHD between fresh, chilled-rewarmed and frozen-thawed semen samples was statistically significant (P<0.02). It can be concluded that based on the CTC-assay and the analysis of motility patterns, capacitation-like changes in dog semen seem to be both initiated and accelerated by the preservation procedures.

Fertility after vaginal or uterine deposition of dog semen frozen in a tris extender with or without Equex STM paste

Twenty-five bitches were artificially inseminated with semen that was frozen-thawed using an egg yolk-Tris-glucose-citrate extender containing 5% glycerol with, or without the addition of 0.5% Equex STM Paste. Semen was collected on 2 occasions from 11 dogs, pooled, and evaluated for sperm motility, morphology and plasma membrane integrity. Each pool was then divided in 2 parts, diluted with 1 of the 2 extenders, and frozen in 0.5-mL straws. In the bitches, plasma progesterone was assayed daily during late proestrus and estrus. Artificial insemination (AI) was performed twice on Days 3 and 5 after the estimated LH peak. For each insemination, 200x10(6) spermatozoa were used. Ten bitches were inseminated with semen frozen without Equex: In 5 females, semen was deposited transcervically into the uterus with the aid of a fiberoptic endoscope and a urethral catheter, while the remaining 5 bitches were inseminated in the cranial vagina using a Norwegian catheter. Fifteen bitches were inseminated with semen frozen-thawed with Equex: Two groups of 5 bitches were inseminated according to the techniques described above, while 5 bitches were inseminated vaginally using the Osiris catheter. Pregnancy was diagnosed and the number of fetuses counted by ultrasound examination. Post-thaw, spermatozoa frozen with Equex tended to have higher total and progressive motility and to survive longer in vitro than when the extender without Equex was used. Spermatozoal concentration, age of the bitches, duration of heat and estrus, and progesterone concentration at LH peak and at the first and second AI did not differ among the 5 groups. The overall pregnancy rate of 84% (21/25) was close to what can be expected from well controlled natural matings. For both freezing extenders tested, 5/5 bitches were pregnant after uterine deposition of semen and 4/5 were pregnant when semen was deposited in the anterior vagina using the Norwegian catheter. With the Osiris catheter, 3/5 inseminations resulted in a pregnancy. No significant differences in pregnancy rate or number of fetuses were found between groups, site of deposition or freezing extender.

In vitro characteristics of canine spermatozoa subjected to two methods of cryopreservation

The in vitro viability of canine spermatozoa was evaluated after freezing-thawing using the Andersen method, and the commercial CLONE method. These methods differ in the extenders used, number of dilution steps, and equilibration times as well as in both freezing and thawing techniques and rates. Insemination with semen frozen-thawed by either method gives high whelping rates in practice, implying that dog spermatozoa can retain their fertilizing ability after being subjected to widely different preservation methods. The in vitro viability of spermatozoa processed by these methods has not been previously evaluated in detail. Three ejaculates were collected from each of 5 fertile dogs. Each ejaculate was divided into 2 parts and frozen in medium straws according to the 2 methods. Two straws were thawed and examined from each freezing batch. Sperm motility was assessed in the undiluted semen, and in frozen-thawed semen immediately after thawing, and after storage for 3, 6 and 24 h at room temperature (Straw 1) or 1, 2 and 3 h at 37 degrees C (Straw 2, thermoresistance test). The integrity of the sperm plasma membrane was evaluated in undiluted, in equilibrated (diluted and chilled), and in frozen-thawed spermatozoa using fluorophore probes. The acrosome morphology of frozen-thawed spermatozoa was assessed using a commercial stain (Spermac). Motility immediately after thawing was significantly higher with the CLONE method (75.3% [SD = 4.0] for Straw 1 and 73.7% [SD = 3.2] for Straw 2) than with the Andersen method (70.0% [SD = 5.1] and 69.7% [SD = 3.2]). Motility decreased during storage after thawing. Spermatozoa frozen-thawed using the CLONE method showed a significantly lower thermoresistance. The proportion of spermatozoa with intact plasma membrane was not affected by the equilibration procedure used with either method but was significantly decreased (P < 0.001) after thawing with both methods. The percentage of spermatozoa exhibiting changes thought to represent different stages of acrosomal degradation, was 45.7% (SD = 5.3) using the Andersen method and 44.1% (SD = 9,4) using the CLONE method. Both cryopreservation methods thus resulted in high initial post-thaw sperm motility and membrane integrity but low thermoresistance, and under both methods a large proportion of sperm cells were undergoing acrosomal degradation. The methods differed significantly in terms of their effect on sperm motility but not on plasma membrane integrity or acrosomal morphology.

Effects of equex STM paste on viability of frozen-thawed dog spermatozoa during in vitro incubation at 38 °C

In the canine, artificial insemination with cryopreserved semen generally yields lower pregnancy rates with vaginal deposition than with uterine deposition, one of the reasons being the shortened life span of frozen-thawed spermatozoa. The incubation of spermatozoa at body temperature partially mimics the situation in vivo, and evaluation of the kinetics of viability loss under these conditions can be used to measure the damage caused by freezing and thawing procedures. In this study, 2 aliquots were separated from split ejaculates collected from 7 dogs and were frozen by lowering the straws, in 3 steps, into an LN(2) tank after dilution with egg yolk Tris-citrate-glucose extender with or without the addition of 0.5% Equex STM paste. Motility and plasma membrane integrity (evaluated with the combined fluorescent probes 6-carboxyfluorescein diacetate and propidium iodide) were assessed immediately after thawing and over the next 3 h at 38 degrees C. The addition of Equex STM paste significantly increased the proportion of spermatozoa having an intact plasmalemma immediately after thawing compared with the control. It also increased the longevity of the thawed spermatozoa, prolonging the maintenance of both motility and plasma membrane integrity.

Effects of seminal plasma and three extenders on canine semen stored at 4 °C

Semen preservation and artificial insemination (AI) in the canine has become a common practice in veterinary medicine. Chilled dog semen is easy to handle, and several extenders can be used. The aim of this study was to compare the effects on canine spermatozoa of seminal plasma and 3 extenders commonly used for chilled semen preservation in clinical practice. The characteristics evaluated were sperm motility; velocity; plasma membrane status (assessed with a fluorescence staining technique and hypo-osmotic swelling test); acrosome morphology; semen pH; and semen osmolarity. These criteria were monitored daily in the ejaculates of 11 dogs. The ejaculates were divided into 4 aliquots. Each aliquot was extended in autologous seminal plasma, egg-yolk Tris, egg-yolk milk or egg-yolk cream and preserved at 4 degrees C for 4 d. In 10 of 11 semen samples extended in autologous seminal plasma, motility had already decreased to 0% by Day 2, and the percentage of spermatozoa with intact membranes was lower than in the 3 extenders (P < 0.05). Motility up to Day 4 was higher in egg-yolk Tris-stored spermatozoa (53.6%) than in those preserved in egg-yolk milk (30.4%) and egg-yolk cream (14.1%). Spermatozoa stored in egg-yolk Tris also had the highest sperm velocity, whereas no difference was found in plasma membrane or acrosome status (P>0.05). Egg-yolk Tris extender seems to be superior to the other extenders tested, to preserve dog semen at 4 degrees C, although differences were not significant for all the parameters.

The effects of hexavalent and trivalent chromium on fertilization and development in sea urchins

The action of Cr6+ (as chromate) and Cr3+ (as sulfate and nitrate) on fertilization and development has been investigated in sea urchins. By rearing the embryos in the presence of chromate (5 X 10(-5) to 5 X 10(-4) M), the differentiation of the gut and skeleton was severely affected. The treatment of sperm before fertilization with CrO2- 4 (10 to 30 min, 10(-4) to 10(-2) M) resulted in a number of abnormal larvae, depending on the length of exposure and the CrO2- 4 concentration. Morphological and quantitative changes of mitotic activity during cleavage were observed as a result of CrO2- 4 exposure of zygotes, as well as of sperm and egg pretreatment. The exposure of embryos to Cr3+ after fertilization permitted larval differentiation, but affected the motility and hatchability of the embryos. The pretreatment of gametes with Cr3+ never induced larval malformations. Cr3+ exerted a strong depressive action on fertilization by decreasing the fertilizing capacity of sperm and leaving the fertilizability of the eggs almost unaffected.