Effects of insulin-like growth factor-I, epidermal growth factor and cysteamine on the in vitro maturation and development of oocytes collected from 6- to 8-week-old Merino lambs.

To improve the viability of embryos produced in vitro from lamb oocytes, maturation medium was supplemented with insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF), cysteamine, and combinations thereof. Experiment 1 examined the effects of IGF-I supplementation and duration of oocyte maturation on nuclear maturation and embryo development while Experiments 2 and 3 examined the effects of cysteamine and EGF supplementation respectively on embryo development. In Experiment 4, embryo development was examined after maturation with various combinations of supplements. IGF-I supplementation increased cleavage rate (P < 0.05) but its effect on the rate of blastocyst production from original oocytes was variable. Supplementation with IGF-I increased (P < 0.01) the proportion of oocytes at Metaphase II (MII) after 18 h of maturation but not at later times. EGF either alone or combined with IGF-I significantly (P < 0.05) increased cleavage rates compared with other treatment groups but EGF consistently failed to improve blastocyst production rates. Cysteamine improved hatching rates but only when supplemented alone. Maturation of lamb oocytes for 22 h in medium supplemented with 100 ng mL(-1) IGF-I and 100 microm cysteamine resulted in the production of 16.0 lambs per donor lamb after embryos were transferred to recipient ewes. It is concluded that EGF and, to a lesser extent, IGF-I, whilst beneficial to initial cleavage, can adversely influence subsequent embryo development. Improvements in embryo viability may more likely be obtained by addressing issues that influence fetal oocyte quality than by modifying in vitro methodology.

Assessment of in vitro sperm characteristics in relation to fertility in dairy bulls.

The performance of frozen-thawed spermatozoa from 10 Holstein bulls in a range of in vitro diagnostic tests and the relationship with adjusted in vivo fertility data was determined. The tests included an assessment of motility (subjective and computer-assisted), morphology, concentration, viability, acrosomal and chromatin integrity conducted immediately post-thaw and after swim-up, in conjunction with membrane status (CTC staining) and migration in an artificial cervical mucus. Adjusted in vivo fertility correlated with subjectively assessed post-thaw motility (r=0.672, p=0.033), post-thaw straight-line velocity (r=0.636, p=0.048), post-thaw sperm morphology (r=-0.762, p=0.010), post-thaw sperm viability (r=0.635, p=0.048), the concentration of spermatozoa after swim-up (r=0.649, p=0.042), sperm morphology after swim-up (r=-0.687, p=0.028), the number of spermatozoa migrating 10mm into artificial cervical mucus (r=0.632, p=0.050) and the distance migrated by the vanguard spermatozoon in artificial mucus (r=0.701, p=0.024). A stepwise regression analysis identified tests which, when combined, produced models with a strong correlation (R(2)>0.9) to fertility.

Effect of seminal plasma fractions from entire and vasectomized rams on the motility characteristics, membrane status, and in vitro fertility of ram spermatozoa.

Whole seminal plasma from ram semen collected before and after vasectomy was separated into 2 fractions, supernatant and pellet of vesicles, and their protein profiles characterized by one-dimensional (1D) gel electrophoresis. The effects of autologous whole seminal plasma and these fractions on motility characteristics (assessed subjectively and by computer-assisted sperm analysis), membrane status (assessed by chlortetracycline staining patterns), and in vitro fertility (assessed by fertilization success and timing of fertilization events) of washed frozen-thawed ram spermatozoa were studied. Regardless of vasectomy, whole seminal plasma and supernatant displayed similar protein patterns. These fractions, when included in the postthaw buffer, improved the motility characteristics (59.6% +/- 6.21% and 39.6% +/- 6.21% vs 31.7% +/- 6.46% and 15.5% +/- 6.46% total motility) and membrane integrity (36.6% +/- 8.52% and 31.2% +/- 8.19% vs 30.3% +/- 11.49% and 21.6% +/- 10.28% B staining pattern [characteristic of capacitated acrosome-intact cells] for whole seminal plasma and supernatant vs control at 3 and 6 hours of postthaw incubation, respectively) of frozen-thawed spermatozoa and improved their ability to fertilize in vitro-matured oocytes compared with control buffer without seminal plasma fractions (25.3%, 47.4%, and 37.4% vs 12.3%, 20.2%, and 20.5% oocytes fertilized for spermatozoa incubated with supernatant vs control at 2, 6, and 18 hours after insemination, respectively). Vesicles were absent from semen collected after vasectomy. Pellets of vesicles collected before vasectomy had no effect on spermatozoa at their normal protein concentration but marginally improved both motility characteristics and in vitro fertility, possibly due to contamination from supernatant proteins, when their concentration in the postthaw medium was increased by threefold. It was concluded that the vesicle-free supernatant fraction of seminal plasma, but not the seminal plasma membrane vesicles, improved the function and fertility of frozen-thawed ram spermatozoa when added to the postthaw medium.

Cryopreservation of epididymal alpaca (Vicugna pacos) sperm: a comparison of citrate-, Tris- and lactose-based diluents and pellets and straws.

Epididymal spermatozoa were harvested from male alpacas and frozen after extension and cooling to 4 degrees C in citrate-, Tris- and lactose-based diluents (Experiment 1) and as pellets in 0.25- and 0.5-mL straws on either dry ice or over liquid nitrogen vapour (Experiment 2) to determine the effects diluents and packaging on their motility and acrosome integrity. In Experiment 1, sperm motility was higher after cooling to 4 degrees C and after freeze-thawing (0 but not 3 h post-thaw) for spermatozoa extended in the lactose- than the citrate- or Tris-based diluent (P < 0.05). Post-thaw acrosome integrity after cooling to 4 degrees C and post-thaw (0 h) was reduced for spermatozoa frozen in citrate- compared with lactose- or Tris-based diluents, but was similar for all groups 3 h after thawing. In Experiment 2, sperm motility immediately after thawing was higher for pellet freezing than for 0.25- or 0.5-mL straws on dry ice or liquid nitrogen vapour (P < 0.05), although by 3 h post-thaw motility was similar for pellets and straws (P > 0.05). Acrosome integrity was similar for all groups immediately after thawing and 3 h post-thaw. Cryopreservation of epididymal alpaca spermatozoa is feasible, with retained motility and acrosome integrity post-thaw. Freezing as pellets in a lactose-based diluent is recommended.

Effect of GnRH treatment on the maturation and in vitro development of oocytes collected from 4- to 6-week-old Merino lambs.

Two experiments were conducted in Merino lambs to examine the effects of gonadotrophin-releasing hormone (GnRH) treatment on the developmental competence of oocytes collected after pretreatment with follicle stimulating hormone (FSH). The first experiment examined the effects of six GnRH treatment times (control and GnRH administered 2, 4, 6, 8 and 10 h before oocyte collection) and four in vitro maturation (IVM) periods (18, 20, 22, 24 h) on the rate of oocyte nuclear maturation. The second experiment examined the effect of five GnRH treatment times (control and GnRH administered 2, 4, 6 and 8 h before oocyte collection) and three IVM periods (20, 22, 24 h) on the development of oocytes and embryos after in vitro maturation, fertilisation and culture. In Experiment 1, GnRH treatment did not influence the mean number of cumulus-oocyte-complexes (COCs) collected or COC morphology at the time of collection. However, treatment changed (P < 0.01) the distribution of follicle size and this was primarily due to a marked reduction in the number of follicles with diameters <2 mm. In addition, GnRH treatment at 6 and 8 h increased (P < 0.01) the proportion of oocytes that developed to Metaphase II (MII) (63.2 and 72.6%, respectively) compared with other treatment times (range 52.9-59.9%). Nuclear maturation was influenced by a significant (P < 0.05) interaction between GnRH treatment and IVM period due to a disproportionately greater number of oocytes at the germinal vesicle breakdown (GVBD) stage for the 2 and 4 h GnRH treatments compared with other treatments. In Experiment 2, cleavage rate (range 63.5-85.9%) was highest when GnRH was administered 8 h before collection but the percentage of cleaved oocytes that developed into blastocysts (range 10.0-35.0%) was significantly (P < 0.05) lower for the 6 and 8 h GnRH treatments compared with the control and the 2 h GnRH treatment. These results demonstrate that GnRH treatment before oocyte collection can improve nuclear maturation and cleavage rates in lamb oocytes but that these improvements are not reflected in improved rates of blastocyst development. It is speculated that this discrepancy may result from GnRH treatment either adversely affecting cytoplasmic maturation or inducing asynchrony between the maturation of the nuclear and cytoplasmic components of the oocyte.

Effects of lamb age, hormone stimulation and response to hormone stimulation on the yield and in vitro developmental competence of prepubertal lamb oocytes.

Experiments were conducted to determine the effects of lamb age, hormone stimulation (Experiment 1) and response to stimulation (Experiment 2) on the in vitro production of embryos from prepubertal lambs aged 3-4 and 6-7 weeks of age. For 3-4-week-old lambs, hormone stimulation increased the number of follicles (29.9 +/- 15.3 v. 70.6 +/- 8.2), oocytes per ovary (18.3 +/- 6.3 v. 39.3 +/- 5.8) and oocyte development to the blastocyst stage (0/192 (0.0%) v. 115/661 (17.4%); P < 0.05). Lamb age (3-4 v. 6-7 weeks old) increased oocyte development to the blastocyst stage (115/661 (17.4%) v. 120/562 (21.4%) respectively). In Experiment 2, hormone-stimulated lambs (3-4 and 6-7 weeks old) were divided into low, medium or high responders based on the number of ovarian follicles (<20, 20-50 and >100 follicles per ovary respectively). The response to hormone stimulation did not affect oocyte recovery rate, but the number of oocytes suitable for culture was increased for high-responding 3-4-week-old lambs only (P < 0.05). Oocyte development to the blastocyst stage was not affected by response to stimulation for 3-4-week-old lambs (15.2-25.6%; P > 0.05), but was reduced for high (6.7%) compared with low (19.5%) and medium (30.9%) responding 6-7-week-old lambs (P < 0.05). These results demonstrate that the production of embryos from prepubertal lambs is increased by hormone stimulation and lamb age and the response to stimulation does not affect embryo production from 3-4-week-old lambs, although by 6-7 weeks of age a high response to stimulation reduces blastocyst formation.

The effect of gamete co-incubation time during in vitro fertilization with frozen-thawed unsorted and sex-sorted ram spermatozoa on the development of in vitro matured adult and prepubertal ewe oocytes.

In vitro matured adult (Experiment 1) and prepubertal (Experiment 2) ewe oocytes were co-incubated with unsorted or sex-sorted frozen-thawed spermatozoa for 2 to 3 h (short) or 18 to 20 h (long) to determine the effects of reducing the gamete co-incubation time during IVF on subsequent embryonic development in vitro. For oocytes derived from adult ewes, there were no differences in oocyte fertilization and cleavage at 24 h post insemination (hpi) between types of spermatozoa or co-incubation times (P > 0.05). By 48 hpi, oocyte cleavage was higher after a short (390/602, 64.8%) compared with a long (381/617, 61.7%) co-incubation (P < 0.05), and was not significantly different for unsorted (266/372, 71.5%) and sex-sorted (505/849, 59.9%) spermatozoa. Blastocyst formation from cleaved oocytes was similar for unsorted (150/266, 56.4%) and sex-sorted (295/505, 58.4%) spermatozoa, but was higher after a short (240/390, 61.5%) than long (205/381, 53.8%) co-incubation (P < 0.05). Oocyte development to the blastocyst stage was not different for unsorted (150/372; 40.3%) and sex-sorted (295/847; 34.8%) spermatozoa but was significantly increased by a short (240/602, 39.9%) compared with a long (205/617, 33.2%) co-incubation. Fertilization of oocytes from prepubertal ewes was similar for types of spermatozoa and for duration of co-incubation. Oocyte cleavage (48 hpi) was similar for a short (241/377, 63.9%) and long (226/349, 64.8%) co-incubation with unsorted spermatozoa, but was increased (P < 0.05) by a long co-incubation (286/500, 57.2% versus 163/517, 31.5%) with sex-sorted spermatozoa. Blastocyst formation from cleaved oocytes was similar for unsorted (230/467, 49.3%) and sex-sorted (186/449, 41.4%) spermatozoa, and a short (200/404, 49.5%) or long (216/512, 42.1%) co-incubation. However, oocyte development to the blastocyst stage was higher (P < 0.05) after IVF with unsorted (230/726, 37.1%) than sex-sorted (186/1017, 18.3%) spermatozoa. Reducing the duration of gamete co-incubation did not deleteriously affect the in vitro development of adult and prepubertal ewe derived oocytes after IVF with unsorted and sex-sorted spermatozoa. In general, sex-sorting had no substantial influence on fertilization and embryo development rates.

In vitro and in vivo developmental capabilities and kinetics of in vitro development of in vitro matured oocytes from adult, unstimulated and hormone-stimulated prepubertal ewes.

The in vitro and in vivo developmental capabilities and kinetics of in vitro development of embryos derived from adult ewes and from unstimulated (16- to 24-week-old) and hormone-stimulated prepubertal (3- to 5-week-old) ewes were assessed. Cleavage was lower for hormone-stimulated (617/1025; 60.2%) than unstimulated prepubertal (117/169; 69.2%) and adult ewe oocytes (184/267; 68.9%; P < 0.05). Blastocyst formation by Day 7 (from zygotes) was similar for unstimulated (45/117; 38.5%), hormone-stimulated prepubertal (229/617; 37.1%) and adult ewes (101/184; 54.9%). Blastocysts derived from hormone-stimulated prepubertal ewes developed mainly on day 7, compared with Day 6 for adult and unstimulated prepubertal ewes. Pregnancy rates (day 60) and embryonic loss (between Days 20 and 60) did not differ after transfer to adult recipient ewes of adult, unstimulated and hormone-stimulated prepubertal-derived fresh or frozen-thawed embryos. The number of lambs born as a proportion of embryos transferred did not differ for fresh and frozen embryos derived from adult ewes (3/16; 18.8% and 1/12; 8.3%, respectively) and unstimulated prepubertal lambs (2/6; 33.3%, and 1/10; 10.0%, respectively), but was higher for fresh than frozen embryos from hormone-stimulated prepubertal ewes (7/16; 43.8%, and 2/14; 14.3%, respectively; P < 0.05). There were high rates of in vitro and in vivo development of oocytes from 3- to 5-week-old lambs, but in vitro development was lower than with oocytes from adult ewes. However, the speed of embryonic development in vitro and the in vivo development of fresh and frozen embryos were similar to those derived from adult and unstimulated prepubertal ewes. The present results were an improvement in the efficiency of producing embryos and offspring from hormone-stimulated 3- to 5-week-old lambs.

Flow cytometric sorting of non-human primate sperm nuclei.

Pre-determination of the sex of offspring has implications for management and conservation of captive wildlife species, particularly those with single sex-dominated social structures. Our goal is to adapt flow cytometry technology to sort spermatozoa of non-human primate species for use with assisted reproductive technologies. The objectives of this study were to: (i) determine the difference in DNA content between X- and Y-bearing spermatozoa (ii) sort sperm nuclei into X- and Y-enriched samples; and (iii) assess the accuracy of sorting. Spermatozoa were collected from two common marmosets (Callithrix jacchus), seven hamadryas baboons (Papio hamadryas) and two common chimpanzees (Pan troglodytes). Human spermatozoa from one male were used as a control. Sperm nuclei were stained (Hoechst 33342), incubated and analyzed using a high-speed cell sorter. Flow cytometric reanalysis of sorted samples (sort reanalysis, 10,000 events/sample) and fluorescence in situ hybridization (FISH; 500 sperm nuclei/sample) were used to evaluate accuracy of sorting. Based on fluorescence intensity of X- and Y-bearing sperm nuclei, the difference in DNA content between X and Y populations was 4.09 +/- 0.03, 4.20 +/- 0.03, 3.30 +/- 0.01, and 2.97 +/- 0.05%, for marmoset, baboon, chimpanzee and human, respectively. Sort reanalysis and FISH results were similar; combined data revealed high levels of purity for X- and Y-enriched samples (94 +/- 0.9 and 93 +/- 0.8%, 94 +/- 0.7 and 94 +/- 0.5%, 91 +/- 0.9 and 97 +/- 0.6%, 94 +/- 0.6 and 94 +/- 0.9%, for marmoset, baboon, chimpanzee and human, respectively). These data indicate the potential for high-purity sorting of spermatozoa from non-human primates.

Preservation and evaluation of semen for artificial insemination.

Many years of research have been devoted to improving the fertility of preserved semen of small ruminants. There have been few significant advances in preservation in recent times, but considerable knowledge has been gained on the effect of preservation on the structure and function of spermatozoa. It has become evident that preservation greatly affects many sperm attributes, such as motility, respiratory activity, membrane status and DNA quality. Consequently, viability is reduced, transport in the female reproductive tract is inhibited, the timing of fertilisation is altered and embryo development is affected following insemination of preserved, compared to fresh spermatozoa. A greater understanding of their functional condition may lead to the development of methods of preventing these alterations or to improved methods of using the preserved spermatozoa for artificial insemination in their altered state.

Repeat ovum pick-up and in vitro embryo production from adult ewes with and without FSH treatment.

Ovum pick-up (OPU) was performed three times on adult ewes after synchronization with (n = 4) or without (n = 4) FSH treatment to investigate the effects of FSH treatment on the number of ovarian follicles, oocytes recovered, oocyte quality and development in vitro. FSH treatment increased the number of ovarian follicles (85 vs 162) and oocytes recovered (33 vs 91), although recovery rate was similar for ewes with and without FSH (91/162, 56.2% and 33/85, 38.8% respectively). Of the oocytes recovered, those classified as grades I and II were similar between ewes with (78/91, 85.7%) and without FSH treatment (27/33, 81.8%). The number of ovarian follicles was similar after repeated OPU for ewes treated with FSH, but for ewes not treated with FSH the number of ovarian follicles decreased with repeated OPU. The number of oocytes recovered decreased for FSH-treated ewes only, while the oocyte recovery rate and proportion of oocytes classified as grades I and II were not affected by repeated OPU. Oocyte cleavage (46/78, 58.9% and 19/24, 79.2%) and blastocyst formation (35/46, 76.1% and 12/19, 63.2% respectively) were similar for ewes with and without FSH treatment. The number of ovarian follicles varied between ewes (p < 0.05) although the number of oocytes recovered and oocyte development in vitro were similar between ewes.

Effect of medium on the kinematics of frozen-thawed ram spermatozoa.

Cervically inseminated cryopreserved ram spermatozoa have reduced fertility due to poor mucus-penetrating ability. This effect is ameliorated by the addition of 20% (v/v) seminal plasma (SP) to the phosphate-buffered saline (PBS) thawing medium. The aims of this study were to determine whether the impaired mucus penetration was due to alterations in the sperm motility and, if so, whether these alterations were due to the SP or its viscosity, or to the medium components. To this end, artificial SP medium (ASP), a medium which supports motility but not capacitation, was compared with PBS and SP. Thawed, pooled semen from seven mature rams was layered under 1 ml each of PBS, SP and ASP and motile spermatozoa allowed to swim up (37 degrees C, 30 min). Upper regions of the overlays were harvested, and the capacitation status of the spermatozoa in each suspension determined by chlortetracycline (CTC) analysis. Sperm movement was videotaped in 300 microm chambers for both computer-aided sperm analysis assessment and manual flagellar curvature analysis. There was no effect of the culture medium on the concentration of spermatozoa recovered by swim up, nor on the proportion of motile spermatozoa. However, the spermatozoa resuspended in PBS did show changes associated with capacitation in both the CTC-binding patterns and in their movement patterns. These changes were significantly greater than those observed in spermatozoa resuspended in SP or ASP. These results indicated that the differences in sperm movement and function observed in SP medium were not due to changes in viscosity, but rather to components of the medium.