Theriogenology xxx (2015) 1–7

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Insulinlike growth factor I improves yak (Bos grunniens) spermatozoa motility and the oocyte cleavage rate by modulating the expression of Bax and Bcl-2 Yangyang Pan a, Yan Cui a, Abdul Rasheed Baloch b, Jiangfeng Fan a, Junfeng He a, Guyue Li a, Hongfei Zheng a, Yifu Zhang a, Peng Lv a, Sijiu Yu a, *,1 a

Gansu Province Livestock Embryo Engineering Research Center, College of Veterinary Medicine, Gansu Agricultural University, Lanzhou, China b Faculty of Veterinary Sciences, Sindh Agriculture University, Tando Jam, Pakistan

a r t i c l e i n f o

a b s t r a c t

Article history: Received 9 December 2014 Received in revised form 28 March 2015 Accepted 7 May 2015

The aim of our present study was to examine the effects of insulinlike growth factor 1 (IGF-1) on yak sperm motility during in vitro capacitation and the relationship between the effects of IGF-1 on yak sperm motility and apoptosis was evaluated. Frozen–thawed yak spermatozoa were incubated at 38  C for 1 hour in Tyrode’s bicarbonate-buffered medium for sperm culture (Sp-TALP) with different concentrations (0, 50, 100, and 200 ng/mL) of IGF-1. In every treatment, the sperm motility was measured by a computer-assisted sperm analyzer system. The fertilizing ability of spermatozoa was evaluated on the basis of oocyte cleavage rate after insemination. The expression of Bax and Bcl-2 was examined by real-time polymerase chain reaction and Western blot for the messenger RNA and protein levels. It is interesting to note that IGF-1 improved yak spermatozoa motility and the cleavage rate of oocytes; these improvements were highest in the 100 ng/mL IGF-1 group, followed by the 200 ng/mL and 50 ng/ mL groups, with the lowest improvements in motility and cleavage rates in groups without IGF-1. The expression level of Bax was downregulated by IGF-1, whereas Bcl-2 was upregulated. Both messenger RNA and Bax proteins were lowest in groups with 100 ng/mL IGF-1, where the Bcl-2 was the highest. Bax expression in the groups with IGF-1 was lower than that in the group without IGF-1, and Bcl-2 expression was higher in groups with IGF-1 than that in the group without IGF-1. In conclusion, this research reports that improvements in yak spermatozoa motility and the oocyte cleavage rate after the addition of IGF-I may be a result of the reduction of spermatozoa apoptosis rates by modulating the expression of Bax and Bcl-2. Ó 2015 Elsevier Inc. All rights reserved.

Keywords: Insulinlike growth factor 1 Yak Motility Spermatozoon Bax Bcl-2

1. Introduction The yak (Bos grunniens) is a seasonally polyestrous animal. The breeding season occurs from July to October, and the calving season occurs from April to July; the reproductive rate in yaks is lower (40%–60%) than that in other mammals [1–3]. Therefore, it is important to improve the * Corresponding author. Tel./fax: þ86 0931 7632858. E-mail address: [email protected] (S. Yu). 1 Present address: No. 1 Yingmen Village, Anning District, Lanzhou, 730070, Gansu Province, P.R.China. 0093-691X/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.theriogenology.2015.05.007

reproductive efficiency of yaks by in vitro embryo production, and the spermatozoa are the key for in vitro embryo production [4]. In recent years, the role of nutrient-related metabolic hormones, such as insulin, growth hormone, and insulinlike growth factors (IGF), in the gamete function has been a research focus to improve the reproductive efficiency in farm animals [5,6]. However, such reports are relatively low for yak in vitro embryo production with frozen–thawed semen. Growth factors play an important role in the paracrine and autocrine control of testicular functions [7,8], and furthermore, they maintain sperm function as an energy

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source for spermatozoa. In particular, insulinlike growth factor 1 (IGF-1) improves the quality of mammalian spermatozoa [9–11]. Insulinlike growth factor 1 is a singlechain mitogenic protein that is mostly found in highly proliferative cells and has been reported to be an important factor for germ cell development, maturation, capacitation, and spermatozoa motility [10]. Insulinlike growth factor 1 is an important regulator of spermatogenesis [12] and is a potent mitogenic, metabolic, and differentiating polypeptide. The association of the seminal plasma IGF-1 concentration with spermatozoa motility and morphology has been reported in equines [13]. The in vitro addition of IGF-1 at physiological concentrations stimulates spermatozoa motility in washed bovine semen samples [10]; it has been suggested that IGF-1 might maintain spermatozoa motility through energy uptake or the antioxidant effect. The in vitro effects of IGF-1 on bovine sperms have been observed to significantly improve the total and progressive motility of bovine sperm [10]. In addition, IGF-I also plays a role in human sperm maturation and capacitation [14]; it prevents the deterioration of sperm functional parameters and fertility in buffaloes [15] and increases sperm motility and viability in rabbits [16] and bulls [10]. Apoptosis is a well-known cell death mechanism, as is necrosis, and apoptosis is regulated by several genes and molecules that play a significant role in the initiation of this process [17]. The IGF system can affect the members of two families of apoptosis regulatory proteins, i.e., the Bcl-2 (the B-cell lymphoma/leukemia 2) family and the caspases [18]. The Bcl-2 family consists of many members, both proapoptotic and antiapoptotic, such as Bax and Bcl-2 [18]. To date, little information is available on the effects of IGF-1 on apoptosis in mammalian spermatozoa during in vitro capacitation. The importance of IGF-1 on some semen quality traits has been reported in a number of species; however, its effect as a supplement has not been reported in yaks. Thus, the goal of our study was to examine the effects of IGF-1 on yak sperm motility during in vitro capacitation and to determine whether the influence of IGF-1 on yak sperm motility was related to apoptosis, for example, by modulating Bax and Bcl-2 expression. 2. Materials and methods All the chemicals used in this study were purchased from Sigma–Aldrich (St. Louis, MO, USA) unless otherwise specified. 2.1. Frozen sperm separation procedures Yak semen that was frozen in 0.25-mL straws was provided by the Centre of Livestock Reproductive and Developmental in Qinghai province of China. Either semen from a single straw was used or semen pooled from several straws from the same yak was used. In all experiments, the sperm concentration was determined with a hemocytometer before freezing. As previously described, the swim-up procedure was used for sperm separation, with some modifications [19]. Briefly, semen in straws was thawed for 60 seconds at 35  C. Depending on the experimental needs,

four groups were designed. In each experiment group, four straws with 0.25 mL of thawed semen were layered under 1-mL aliquots of Tyrode’s bicarbonate-buffered medium for sperm culture (Sp-TALP) [20] with 0, 50, 100, and 200 ng/ mL concentrations of IGF-1 in 1.5-mL plastic tubes. After capacitation for 1 hour at 37.5  C, the top 0.8 mL of medium from tube was transferred to a 5-mL conical centrifuge tube. The swim-up–separated spermatozoa were then diluted with Sp-TALP medium with different concentrations of IGF-1 to a final volume of 5 mL. After centrifugation at 120  g for 10 minutes, the supernatant was discarded and the sperm pellet was diluted to 5 mL with Sp-TALP medium with different concentrations of IGF-1. Then, the separated spermatozoa were centrifuged again at 120  g for 10 minutes, and the supernatant was discarded. In this step, the IGF-1 concentrations were consistent with the concentrations used in the capacitation for every group. The concentration of the sperm pellet was then determined again and diluted to 5 to 8  106 spermatozoa/mL with SpTALP for IVF, and spermatozoa motility was detected. 2.2. Effect of IGF-1 on spermatozoa motility Sperm motility was observed under a microscope, and the percentages of total spermatozoa motility and progressive forward motility in all of the sperm were evaluated. Sperm suspensions of 10 mL (1  105 cells/mL) prepared after capacitation were placed onto a prewarmed (37  C) microscopic slide that was covered with an 18  18-mm coverslip (Blue Star, Mumbai, India), and sperm motility analysis was performed using a computer-assisted semen analyzer (Microptic, Barcelona, Spain). Analysis was based on the examination of 25 consecutive digitized images per second using a  10 negative phase-contrast objective. The set parameters were cell size (range: 5–70 mm2), spermatozoa concentration (5–8  106/mL), motile cells (>10 mm/s at 37  C), progressive forward motility (>60% straightness index), circular ( 0.05), and the rates were 61.78  1.6% and 64.12  2.1%, respectively. 3.3. Gene expression of Bax and Bcl-2 in yak spermatozoa In this study, we analyzed the expression of Bax and Bcl2 genes in yak spermatozoa treated with different concentrations of IGF-1. The genes were selected on the basis of the results of our previous study. Transcript relative abundance of Bax and Bcl-2 genes determined by real-time PCR is shown (Fig. 1). The expression level of Bax was found to be significantly lower in spermatozoa with 100 ng/mL of IGF-1 (P < 0.01; Fig. 1); the level of Bcl-2 genes was highest in the same groups. In groups with IGF-1, Bax was lower than in the group without IGF-1, and Bcl-2 was higher in groups with IGF-1 than in the group without IGF-1. Furthermore, the gene levels of Bax and Bcl-2 were not significantly different between the two experimental groups with 50 ng/mL and 200 ng/mL of IGF-1 (P > 0.05, Fig. 1). 3.4. Proteins expression of Bax and Bcl-2 in yak spermatozoa Western blot analysis was performed to investigate the protein expressions of Bax and Bcl-2 in yak spermatozoa that were treated with different concentrations of IGF-1 (Fig. 2), and both of the proteins could be detected with specific antibodies. The expression of the Bax protein was lowest in spermatozoa with 100 ng/mL of IGF-1 (P < 0.01; Fig. 2 and Fig. 3), whereas the level of the Bcl-2 protein was highest in the same groups (Figs. 2 and 4). The Bax protein in groups with IGF-1 was lower than that in the group without IGF-1 (Fig. 3), and the Bcl-2 protein was higher in groups with IGF-1 than that in the group without IGF-1 (Fig. 4). In addition,

Table 2 Effect of insulinlike growth factor 1 (IGF-I) on the spermatological traits. Groups

Total spermatozoa motility (%)

IGF-1, IGF-1, IGF-1, IGF-1,

67.63 67.83 76.45 70.08

0 ng/mL 50 ng/mL 100 ng/mL 200 ng/mL

   

4.13a 6.31a 2.08c 4.76b

Progressive forward motility (%) 13.18 20.06 31.83 23.14

   

1.20a 2.03b 3.93c 1.86b

Straight line velocity (mm/s) 16.73 21.43 34.89 22.39

Data were presented as the mean  standard error of the mean (n ¼ 5). a,b,c The superscript letters within a row for a particular parameter differ significantly.

   

3.12a 2.09b 4.69c 1.87b

Linearity (%) 23.19 38.07 56.31 34.12

   

2.61a 1.06b 3.60c 2.18b

Lateral head displacement (mm/s) 2.07 2.13 2.09 2.10

   

0.13 0.32 0.29 0.11

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Table 3 Cleavage rate of the oocytes after IVF by sperm from four groups at 48 hours. Group IGF-1, IGF-1, IGF-1, IGF-1,

Cleavage rate (%) 0 ng/mL 50 ng/mL 100 ng/mL 200 ng/mL

52.36 61.78 73.09 64.12

   

3.3a 1.6b 4.3c 2.1b

Data were presented as the mean  standard error of the mean (n ¼ 5). a,b,c The superscript letters within a row for a particular parameter differ significantly (P < 0.05).

the protein levels of Bax and Bcl-2 were also significantly different between two experimental groups with 50 ng/mL and 200 ng/mL of IGF-1 (P > 0.05, Figs. 3 and 4). 4. Discussion The yak is a seasonally polyestrous animal that is known for its lower reproductive rate compared to other mammalian species [3,25]. Therefore, it is very important to improve the reproductive efficiency of yaks by studying the physiological mechanisms of embryonic development. Fertility is equally related to the quality of the spermatozoa and oocytes apart from appropriate conditions for fertilization and embryo development. Recently, a few studies have been focused on improving the quality of bovine spermatozoa by in vitro addition of IGF-1 [8,10,16]. Our present study was conducted to assess the effect of IGF-1 on improving yak spermatozoa motility and the oocyte cleavage rate and also to determine IGF-I influences yak sperm motility in relation with apoptosis. The swim-up method based on the separation of sperm with respect to the motility of spermatozoa has been

Fig. 1. Relative gene expressions (mean  standard error of the mean) of Bax and Bcl-2 in yak spermatozoa capacitation for 1 hour in Tyrode’s bicarbonate-buffered medium for sperm culture (Sp-TALP) with different concentrations of insulinlike growth factor 1 (IGF-1). The expression levels shown as relative quantitation were analyzed using real-time polymerase chain reaction. GAPDH was used to normalize each gene, and spermatozoa treated with 0 ng/mL of IGF-1 were used as calibrators. a,b,cDifferent letters on the bars in the same gene indicate values that differ significantly (P < 0.05). mRNA, messenger RNA.

Fig. 2. Detected the expression levels of BAX and Bcl-2 proteins with the Western blot method in different groups. 1: The negative control oocytes (0 ng/mL of insulinlike growth factor 1 [IGF-1]); 2: 50 ng/mL of IGF-1; 3: 100 ng/mL of IGF-1; 4: 200 ng/mL of IGF-1.

confirmed in buffalo [26], rabbits [16], and bovine [27]; the Percoll gradient method is used to select the sperms with respect to their density [28]. In our study, yak spermatozoa were separated by the swim-up method and capacitation in Sp-TALP medium with different concentrations of IGF-1 for 1 hour. The overall motility of yak spermatozoa was significantly higher in the group with 100 ng/mL of IGF-1 (Table 2). The best IGF-1 concentration used in this study was 100 ng/mL because it approximates the mean physiological concentration of IGF-1 found in buffalo seminal plasma [8] and buffalo [15]. The physiological concentration of IGF-1 was capable of increasing the total and progressive forward motilities compared to the control group during the incubation period. The role of IGF-1 in increasing the total and progressive forward motilities of yak spermatozoa in the present study was in agreement with the earlier reports in bovine [10], buffalo [8], and humans [29]. Insulinlike growth factor 1 might act as a chemokinetic factor involved in the regulation of a cell’s movement [7,10]. Because the IGF-1 receptors have been reported on spermatozoa [10], we presume that the ability of IGF-1 to stimulate motility might be because of the direct effect through the IGF-1 receptor on spermatozoa, which requires further study. The cleavage rate after IVF is the best available end point for expressing fertility when obtaining data to validate a potential diagnosis assay for sperm viability [27,30]. Thus in vitro fertility of spermatozoa capacitated in SpTALP medium with different concentrations of IGF-1 was

Fig. 3. Relative abundance of Bax protein in yak spermatozoa capacitation for 1 hour in Tyrode’s bicarbonate-buffered medium for sperm culture (Sp-TALP) with different concentrations of insulinlike growth factor 1 (IGF-1). The expression levels are shown as relative quantitation; GAPDH was used to normalize each gene, and spermatozoa treated with 0 ng/mL of IGF-1 were used as calibrators. a,b,c,dDifferent letters on the bars indicate values that differ significantly (P < 0.05).

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Fig. 4. Relative abundance of Bcl-2 protein in yak spermatozoa capacitation for 1 hour in Tyrode’s bicarbonate-buffered medium for sperm culture (Sp-TALP) with different concentrations of insulinlike growth factor 1 (IGF-1). The expression levels are shown as relative quantitation; GAPDH was used to normalize each gene, and spermatozoa treated with 0 ng/mL of IGF-1 were used as calibrators. a,b,c,dDifferent letters on the bars indicate values that differ significantly (P < 0.05).

evaluated on the basis of cleavage rate in the present study. Significantly higher cleavage rates were observed when oocytes were inseminated with spermatozoa capacitated with 100 ng/mL of IGF-1 (Table 3) than in other groups. This might be a result of a significantly higher motility of spermatozoa in groups with 100 ng/mL of IGF-1. Motility is an important parameter in fertility and explains why sperm motility enhancers, such as penicillamine–hypotaurine–epinephrine syrup [31] and caffeine [20,32], have been used in IVF procedures to improve the IVF rate [9]. Recently, it has been reported that apoptosis plays a major role in male infertility-related diseases [24,33], and an altered apoptosis process has been found to be closely associated with male infertility and with sperm quality such as motility, viability, and sperm defects [34]. In the course of apoptosis, Bcl-2 antiapoptotic and Bax proapoptotic proteins provide a signaling pathway that helps maintain balance in a cell [17,18]. The relative levels of these two groups of proteins determine whether cells survive or undergo apoptosis. During spermatogenesis, Bax-mediated apoptosis serves as a checkpoint for maintaining the number and quality of spermatozoa [35]. Insulinlike growth factor 1 is a major anabolic agent that is responsible for growth and differentiation as well as for mediating the biological effects of growth hormones in many cell types [36,37]. The IGF system affects the members of two families of apoptosis regulatory proteins: the Bcl-2 family and the caspases. In human neuroblastomas, IGF-1R activation enhances neuroblastoma cell proliferation and survival, and increased IGF-1R expression enhances the protection of neuroblastoma cells from apoptosis that is induced by chemotherapeutic agents and mannitol treatment [37]. To date, little information is available regarding the effects of IGF-1 on apoptosis in spermatozoa, especially in yaks. Therefore, in the present study, we detected the levels of Bax and Bcl-2 proteins and mRNA to evaluate sperm apoptosis. The result showed that the levels of Bax mRNA and proteins were highest in groups with 100 ng/mL of IGF-1, whereas Bcl-2 was lowest in these

groups (Figs. 1, 2 and 4). Hence, IGF-1 the inhibited the sperm apoptosis by modulating the expressions of Bax and Bcl-2, and the sperm quality was improved because apoptosis was reduced. There are more COCs that are fertilized successfully, and the cleavage rate was also enhanced. However, the relationship among spermatozoa motility, the cleavage rate, and apoptosis still needs further study. This is the first study to report the role of IGF-1 on yak spermatozoa motility and the oocyte cleavage rate and its effect on Bax and Bcl-2 expression. It is concluded that the improvement in spermatozoa motility and the oocyte cleavage rate after the addition of IGF-1 may be a result of the reduction of spermatozoa apoptosis by modulating the Bax and Bcl-2 expression. Acknowledgments The present study was supported by the National Natural Science Foundation of China (Grant no. 31272616, 31472244) and Biotechnology Programmes in Gansu province of China (GNSW-2013-23). References [1] Yu SJ, Li FD. Profiles of plasma progesterone before and at the onset of puberty in yak heifers. Anim Reprod Sci 2001;65:67–73. [2] Zi XD. Reproduction in female yaks (Bos grunniens) and opportunities for improvement. Theriogenology 2003;59:1303–12. [3] Sarkar M, Prakash BS. Circadian variations in plasma concentrations of melatonin and prolactin during breeding and non-breeding seasons in yak (Poephagus grunniens L.). Anim Reprod Sci 2005;90: 149–62. [4] Karatzas G, Karagiannidis A, Varsakeli S, Brikas P. Fertility of fresh and frozen-thawed goat semen during the nonbreeding season. Theriogenology 1997;48:1049–59. [5] Brito LF, Barth AD, Rawlings NC, Wilde RE, Crews Jr DH, Mir PS, et al. Effect of nutrition during calfhood and peripubertal period on serum metabolic hormones, gonadotropins and testosterone concentrations, and on sexual development in bulls. Domest Anim Endocrinol 2007;33:1–18. [6] Ginther OJ, Bergfelt DR, Beg MA, Meira C, Kot K. In vivo effects of an intrafollicular injection of insulin-like growth factor 1 on the mechanism of follicle deviation in heifers and mares. Biol Reprod 2004;70:99–105. [7] Lin T. Regulation of Leydig cell function by insulin-like growth factor-I and binding proteins. J Androl 1995;16:193–6. [8] Selvaraju S, Reddy IJ, Nandi S, Rao SB, Ravindra JP. Influence of IGF-I on buffalo (Bubalus bubalis) spermatozoa motility, membrane integrity, lipid peroxidation and fructose uptake in vitro. Anim Reprod Sci 2009;113:60–70. [9] Silva DM, Zangeronimo MG, Murgas LD, Rocha LG, Chaves BR, Pereira BA, et al. Addition of IGF-I to storage-cooled boar semen and its effect on sperm quality. Growth Horm IGF Res 2011;21:325–30. [10] Henricks DM, Kouba AJ, Lackey BR, Boone WR, Gray SL. Identification of insulin-like growth factor I in bovine seminal plasma and its receptor on spermatozoa: influence on sperm motility. Biol Reprod 1998;59:330–7. [11] Shin SM, Kim S, Hong JG, Kim YJ. IGF-I improves mitochondrial membrane potential during hypothermic storage of canine spermatozoa. J Vet Med Sci 2014;76:1065–7. [12] Spiteri-Grech J, Nieschlag E. Paracrine factors relevant to the regulation of spermatogenesisda review. J Reprod Fertil 1993;98:1–14. [13] Macpherson ML, Simmen RC, Simmen FA, Hernandez J, Sheerin BR, Varner DD, et al. Insulin-like growth factor-I and insulin-like growth factor binding protein-2 and -5 in equine seminal plasma: association with sperm characteristics and fertility. Biol Reprod 2002;67: 648–54. [14] Sanchez-Luengo S, Fernandez PJ, Romeu A. Insulin growth factors may be implicated in human sperm capacitation. Fertil Steril 2005; 83:1064–6.

Y. Pan et al. / Theriogenology xxx (2015) 1–7 [15] Selvaraju S, Nandi S, Subramani TS, Raghavendra BS, Rao SB, Ravindra JP. Improvement in buffalo (Bubalus bubalis) spermatozoa functional parameters and fertility in vitro: effect of insulin-like growth factor-I. Theriogenology 2010;73:1–10. [16] Minelli A, Moroni M, Castellini C. Isolation and purification of the IGF-I protein complex from rabbit seminal plasma: effects on sperm motility and viability. J Exp Zool 2001;290:279–90. [17] Reed JC. Proapoptotic multidomain Bcl-2/Bax-family proteins: mechanisms, physiological roles, and therapeutic opportunities. Cell Death Differ 2006;13:1378–86. [18] Korsmeyer SJ. BCL-2 gene family and the regulation of programmed cell death. Cancer Res 1999;59:1693s–700s. [19] Parrish JJ, Susko-Parrish JL, Leibfried-Rutledge ML, Critser ES, Eyestone WH, First NL. Bovine in vitro fertilization with frozenthawed semen. Theriogenology 1986;25:591–600. [20] Parrish JJ, Susko-Parrish J, Winer MA, First NL. Capacitation of bovine sperm by heparin. Biol Reprod 1988;38:1171–80. [21] Wang LJ, Xiong XR, Zhang H, Li YY, Li Q, Wang YS, et al. Defined media optimization for in vitro culture of bovine somatic cell nuclear transfer (SCNT) embryos. Theriogenology 2012;78:2110–9. [22] Pfaffl MW, Horgan GW, Dempfle L. Relative expression software tool (REST) for group-wise comparison and statistical analysis of relative expression results in real-time PCR. Nucleic Acids Res 2002;30:e36. [23] Aparicio IM, Garcia-Marin LJ, Andreolotti AG, Bodega G, Jensen RT, Bragado MJ. Hepatocyte growth factor activates several transduction pathways in rat pancreatic acini. Biochim Biophys Acta 2003;1643:37–46. [24] Hurtado de Llera A, Martin-Hidalgo D, Gil MC, Garcia-Marin LJ, Bragado MJ. AMP-activated kinase AMPK is expressed in boar spermatozoa and regulates motility. PLoS One 2012;7:e38840. [25] Pope CE. Embryo technology in conservation efforts for endangered felids. Theriogenology 2000;53:163–74. [26] Mehmood A, Anwar M, Naqvi SM. Motility, acrosome integrity, membrane integrity and oocyte cleavage rate of sperm separated by swim-up or Percoll gradient method from frozen-thawed buffalo semen. Anim Reprod Sci 2009;111:141–8.

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[27] Parrish JJ, Krogenaes A, Susko-Parrish JL. Effect of bovine sperm separation by either swim-up or Percoll method on success of in vitro fertilization and early embryonic development. Theriogenology 1995;44:859–69. [28] Le Lannou D, Blanchard Y. Nuclear maturity and morphology of human spermatozoa selected by Percoll density gradient centrifugation or swim-up procedure. J Reprod Fertil 1988;84:551–6. [29] Miao ZR, Lin TK, Bongso TA, Zhou X, Cohen P, Lee KO. Effect of insulin-like growth factors (IGFs) and IGF-binding proteins on in vitro sperm motility. Clin Endocrinol 1998;49:235–9. [30] Ward F, Rizos D, Boland MP, Lonergan P. Effect of reducing sperm concentration during IVF on the ability to distinguish between bulls of high and low field fertility: work in progress. Theriogenology 2003;59:1575–84. [31] Lu KH, Gordon I, Gallagher M, McGovern H. Pregnancy established in cattle by transfer of embryos derived from in vitro fertilisation of oocytes matured in vitro. Vet Rec 1987;121:259–60. [32] Pomeroy KO, Dodds JF, Seidel Jr GE. Caffeine promotes in vitro fertilization of mouse ova within 15 minutes. J Exp Zool 1988;248: 207–12. [33] Bejarano I, Espino J, Paredes SD, Ortiz A, Lozano G, Pariente JA, et al. Apoptosis, ROS and calcium signaling in human spermatozoa: relationship to infertility. Male infertility. USA: InTech-Open Access Publisher; 2012. p. 51–76. [34] Shen H-M, Dai J, Chia S-E, Lim A, Ong C-N. Detection of apoptotic alterations in sperm in subfertile patients and their correlations with sperm quality. Hum Reprod 2002;17:1266–73. [35] Oltvai ZN, Korsmeyer SJ. Checkpoints of dueling dimers foil death wishes. Cell 1994;79:189–92. [36] Van der Ven L, Roholl P, Gloudemans T, Van Buul-Offers S, Welters M, Bladergroen B, et al. Expression of insulin-like growth factors (IGFs), their receptors and IGF binding protein-3 in normal, benign and malignant smooth muscle tissues. Br J Cancer 1997;75:1631. [37] Singleton JR, Randolph AE, Feldman EL. Insulin-like growth factor I receptor prevents apoptosis and enhances neuroblastoma tumorigenesis. Cancer Res 1996;56:4522–9.

Insulinlike growth factor I improves yak (Bos grunniens) spermatozoa motility and the oocyte cleavage rate by modulating the expression of Bax and Bcl-2.

The aim of our present study was to examine the effects of insulinlike growth factor 1 (IGF-1) on yak sperm motility during in vitro capacitation and ...
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