Hostname: page-component-546b4f848f-lx7sf Total loading time: 0 Render date: 2023-05-30T16:44:45.828Z Has data issue: false Feature Flags: { "useRatesEcommerce": true } hasContentIssue false

Sperm DNA fragmentation: causes and identification

Published online by Cambridge University Press:  11 October 2019

Thais Rose dos Santos Hamilton
Animal Reproduction Department, School of Veterinary Medicine and Animal Science, University of São Paulo, SP, Brazil. Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP. CEP 05508-270, Brazil
Mayra Elena Ortiz D’Ávila Assumpção*
Animal Reproduction Department, School of Veterinary Medicine and Animal Science, University of São Paulo, SP, Brazil. Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP. CEP 05508-270, Brazil
Author for correspondence: Mayra Elena Ortiz D’Ávila Assumpção. Animal Reproduction Department, School of Veterinary Medicine and Animal Science, University of São Paulo, SP, Brazil. Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP. CEP 05508-270, Brazil. Tel: +55 11 30917916. E-mail:


Sperm DNA fragmentation is referred to as one of the main causes of male infertility. Failures in the protamination process, apoptosis and action of reactive oxygen species (ROS) are considered the most important causes of DNA fragmentation. Action of ROS or changes in sperm protamination would increase the susceptibility of sperm DNA to fragmentation. Routine semen analysis is unable to estimate sperm chromatin damage. Sperm DNA integrity influences sperm functional capability, therefore tests that measure sperm DNA fragmentation are important to assess fertility disorders. Actually, there is a considerable number of methods for assessing sperm DNA fragmentation and chromatin integrity, sperm chromatin stability assay (SCSA modified), sperm chromatin dispersion (SCD), comet assay, transferase dUTP nick end labelling (TUNEL); and protamine evaluation in sperm chromatin assay, such as toluidine blue, CMA3, protamine expression and evaluation of cysteine radicals. This review aims to describe the main causes of sperm DNA fragmentation and the tests commonly used to evaluate sperm DNA fragmentation.

Review Article
© Cambridge University Press 2019 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Afanasieva, K and Sivolob, A (2018) Physical principles and new applications of comet assay. Biophys Chem 238, 17.CrossRefGoogle ScholarPubMed
Agarwal, A, Saleh, RA and Bendaiwym, A (2003) Role of reactive oxygen species in the pathophysiology of human reproduction. Fertil Steril 79, 829–43.CrossRefGoogle ScholarPubMed
Agarwal, A, Shyam, SR and Allamaneni, MD (2005) Sperm DNA damage assessment: a test whose time has come. Fertil Steril 84, 850–3.CrossRefGoogle ScholarPubMed
Ahmadi, A and Ng, SC (1999) Fertilizing ability of DNA-damaged spermatozoa. J Exp Zool 284, 696704.3.0.CO;2-E>CrossRefGoogle ScholarPubMed
Aitken, RJ, Gordon, E, Harkiss, D, Twigg, JP, Milne, P, Jennings, Z and Irvine, DS (1998) Relative effect of oxidative stress on the functional competence and genomic integrity of human spermatozoa. Biol Reprod 59, 1037–46CrossRefGoogle Scholar
Alvarez, JG and Storey, B (1992) Evidence for increased lipid peroxidative damage and loss of superoxide dismutase activity as a mode of sublethal cryodamage to human sperm during cryopreservation. J Androl 13, 232–41.Google ScholarPubMed
Andrabi, SMH (2007) Mammalian sperm chromatin structure and assessment of DNA fragmentation. J Assist Reprod Genet 24, 561–9.CrossRefGoogle ScholarPubMed
Aoki, VW, Emery, BR, Liu, L and Carrell, DT (2006) Protamine levels vary between individual sperm cells of infertile human males and correlate with viability and DNA integrity. J Androl 27, 890–8.CrossRefGoogle ScholarPubMed
Balhorn, R (1982) A model for the structure chromatin in mammalian sperm. J Cell Biol 93, 298305.CrossRefGoogle Scholar
Balhorn, R (2007) Protein family review: the protamine family of sperm nuclear proteins. Genome Biol 8, 227–35.CrossRefGoogle ScholarPubMed
Balhorn, R, Corzett, M, Mazrimas, J and Watkins, J (1991) Identification of bull protamine disulfides. Biochemistry 30, 175–81.CrossRefGoogle ScholarPubMed
Beletti, ME and Mello, ML (2004) Comparison between the toluidine blue stain and the Feulgen reaction for evaluation of rabbit sperm chromatin condensation and their relationship with sperm morphology. Theriogenology 62, 398402.CrossRefGoogle ScholarPubMed
Berenguer, JG, Peregrin, PC, López-Fernández, C, Fernández, C, Fernández, JL and Calonge, RN (2008) Fragmentación Del ADN espermático. Rev Int Androl 6, 193209.Google Scholar
Bianchi, PG, Manicardi, GC, Urner, F, Campana, A and Sakkas, D (1996) Chromatin packaging and morphology in ejaculated human spermatozoa: evidence of hidden anomalies in normal spermatozoa. Mol Hum Reprod 2, 139–44.CrossRefGoogle ScholarPubMed
Broekhuijse, MLWJ, Sostaric, E, Feitsma, H and Gadella, BM (2012) Relationship of flow cytometric sperm integrity assessments with boar fertility performance under optimized field conditions. J Anim Sci 90, 4327–36.CrossRefGoogle ScholarPubMed
Carrell, DT, Emery, BR and Hammoud, S (2007) Altered protamine expression and diminished spermatogenesis: what is the link? Hum Reprod Update 13, 115.CrossRefGoogle ScholarPubMed
Castro, LS, Siqueira, AFP, Hamilton, TRS, Mendes, CM, Visintin, JA and Assumpção, MEOA (2018) Effect of bovine sperm chromatin integrity evaluated using three different methods on in vitro fertility. Theriogenology 107, 142–8.CrossRefGoogle ScholarPubMed
Cho, CL and Agarwal, A (2018) Role of sperm DNA fragmentation in male factor infertility: a systematic review. Arab J Urol 16, 2134.CrossRefGoogle ScholarPubMed
De Ambrogi, M, Ballester, J, Saravia, F, Caballero, I, Johanniston, A, Wallgren, M, Anderson, M and Rodriguez-Martinez, H (2006) Effect of storage in short and long-term commercial semen extenders on the motility, plasma membrane and chromatin integrity of boar spermatozoa. Int J Androl 29, 543–52.CrossRefGoogle Scholar
Dias, GM, Retamal, CA, Tobella, L, Arnholdt, ACV and Lopez, ML (2006) Nuclear status of immature and mature stallion spermatozoa. Theriogenology 66, 354–65.CrossRefGoogle ScholarPubMed
Dogan, S, Vargovic, P, Oliveira, R, Belser, LE, Kaya, A, Moura, A, Sutovsky, P, Parrish, J and Topper, E (2015) Sperm protamine-status correlates to the fertility of breeding bulls. Bio Reprod 92, 19.CrossRefGoogle ScholarPubMed
Erenpreisa, J, Erenpreiss, J, Freivalds, T, Slaidina, M, Krampe, R, Butikova, J, Ivanov, A and Pjanova, D (2003) Toluidine blue test for sperm DNA integrity and elaboration of image cytometry algorithm. Cytometry A 52, 1927.CrossRefGoogle ScholarPubMed
Evenson, DP (2016) The sperm chromatin structure assay (SCSA) and other sperm DNA fragmentation tests for evaluation of sperm nuclear DNA integrity as related to fertility. Anim Reprod Sci 169, 5675.CrossRefGoogle ScholarPubMed
Evenson, DP, Larson, K and Jost, LK (2002a) Sperm chromatin structure assay: its clinical use for detecting sperm DNA fragmentation in male infertility and comparisons with other techniques. J Androl 23, 2543.CrossRefGoogle ScholarPubMed
Evenson, DP, Larson, K and Jost, LK (2002b) The sperm chromatin structure assay (SCSA™): clinical use for detecting sperm DNA fragmentation related to male infertility and comparisons with other techniques. Andrology Lab Corner. J Androl 23, 2543.CrossRefGoogle Scholar
Fatehi, AN, Bevers, MM, Schoever, E, Roelen, BA, Colenbrander, B and Gadella, BM (2006) DNA damage in bovine sperm does not block fertilization and early embryonic development but induces apoptosis after the first cleavages. J Androl 27, 176–88.CrossRefGoogle Scholar
Fernández, JL, Muriel, L, Rivero, MT, Goyanes, V, Vazquez, R and Alvarez, JG (2003) The sperm chromatin dispersion test: a simple method for the determination of sperm DNA fragmentation. J Androl 24, 5966.Google ScholarPubMed
Ferreira, HN, Ferreira-Silva, JC, Rocha, JM, Farras, MC, Calixto, M, Moura, MT, Alvarenga, MA and Oliveira, AL (2018) Variable inter-assay estimation of sperm DNA fragmentation in stallions classified as good and bad semen freezers. Cryo Letters 39, 6771.Google ScholarPubMed
Flores, RB, Angrimani, DRS, Rui, BR, Brito, MM, Abreu, RA and Vannucchi, CI (2016) The influence of benign prostatic hyperplasia on sperm morphological features and sperm DNA integrity in dogs. Reprod Domest Anim 52, 310–5.CrossRefGoogle ScholarPubMed
Ganguly, I, Gaur, GK, Kumar, S, Mandal, DK, Kumar, M, Singh, U, Kumar, S and Sharma, A (2013) Differential expression of protamine 1 and 2 genes in mature spermatozoa of normal and motility impaired semen producing crossbred Frieswal (HF × Sahiwal) bulls. Res Vet Sci 94, 256–62.CrossRefGoogle Scholar
Garcia-Macias, V, Martinez-Pastor, F, Alvarez, M, Borragan, S, Chamorro, CA, Soler, AJ, Anel, L and Paz, P (2006) Seasonal changes in sperm chromatin condensation in ram (Ovis aries), Iberian red deer (Cervus elaphus hispanicus), and brown bear (Ursus arctos ) J Androl 27, 837–46.CrossRefGoogle Scholar
Gawecka, JE, Ribas-Maynou, J, Benet, J and Ward, WS (2015) A model for the control of DNA integrity by the sperm nuclear matrix. Asian J Androl 17, 610–5.Google Scholar
Gosálvez, J, López-Fernández, C, Fernández, JL, Gouraud, A and Holt, WV (2011) Relationships between the dynamics of iatrogenic DNA damage and genomic design in mammalian spermatozoa from eleven species. Mol Reprod Dev 78, 951–61.CrossRefGoogle ScholarPubMed
Hamilton, TRS, Castro, LS, Delgado, JD, Assis, PM, Siqueira, AFP, Mendes, CM, Goissis, MD, Muiño-Blanco, T, Cebrián-Pérez, JA, Nichi, M, Visintin, JA and Ortiz D’Ávila Assumpção, ME (2016) Induced lipid peroxidation in ram sperm: semen profile, DNA fragmentation and antioxidant status. Reproduction 151, 379–90.CrossRefGoogle ScholarPubMed
Hamilton, TRS, Simões, R, Mendes, CM, Goissis, MD, Nakajima, E, Martins, EA, Visintin, JA and Assumpção, ME (2019) Detection of protamine 2 in bovine spermatozoa and testicles. Andrology 7, 373–81.CrossRefGoogle ScholarPubMed
Hamilton, TRS, Siqueira, AFP, Castro, LS, Mendes, CM, Delgado, JD, Assis, PM, Mesquita, LP, Maiorka, PC, Nichi, M, Goissis, MD, Visintin, JA and Assumpção, MEOD (2018) Effect of heat stress on sperm DNA: protamine assessment in ram spermatozoa and testicle. Oxid Med Cell Longev 2018, 114.CrossRefGoogle ScholarPubMed
Hernandez, M, Roca, J, Ballester, J, Vazquez, JM, Martinez, EA, Johannisson, A, Saravia, F and Rodriguez-Martinez, H (2006) Differences in SCSA outcome among boars with different sperm freezability. Int J Androl 29, 583–91.CrossRefGoogle ScholarPubMed
Kamimura, C D, Jacomini, JO and Beletti, ME (2010) Chromatin alterations in ram and goat spermatozoa evaluated by toluidine blue and acridine orange. Cienc Agrotec 34, 212–9.CrossRefGoogle Scholar
Kasimanickam, R, Nebel, RL, Peeler, ID, Silvia, WL, Wolf, KT, McAllister, AJ and Cassell, BG (2006) Breed differences in competitive indices of Holstein and Jersey bulls and their association with sperm DNA fragmentation index and plasma membrane integrity. Theriogenology 66, 1307–15.CrossRefGoogle ScholarPubMed
Kipper, BH, Trevizan, JT, Carreira, JT, Carvalho, IR, Mingoti, GZ, Beletti, ME, Perri, SHV, Franciscato, DA, Pierucci, JC and Koivisto, MB (2016) Sperm morphometry and chromatin condensation in Nelore bulls of different ages and their effects on in vitro fertilization. Theriogenology 87, 154–60.CrossRefGoogle Scholar
Krzanowska, H (1982) Toluidine blue staining reveals changes in chromatin stabilization of mouse spermatozoa during epididymal maturation and penetration of ova. J Reprod Fertil 64, 97101.CrossRefGoogle ScholarPubMed
Larson-Cook, KL, Brannian, J, Hansem, KA, Kasperson, KM, Aamold, ET and Evenson, DP (2003) Relationship between the outcomes of assisted reproductive techniques and sperm DNA fragmentation as measured by the sperm chromatin structure assay. Fertil Steril 80, 895902.CrossRefGoogle ScholarPubMed
Lewis, SE and Agbaje, IM (2008) Using the alkaline comet assay in prognostic test for male infertility and assisted reproductive technology outcome. Mutagenesis 23, 163–70.CrossRefGoogle Scholar
Lewis, SE and Aitken, RJ (2005) DNA damage to spermatozoa has impacts on fertilization and pregnancy. Cell Tissue Res 322, 3341.CrossRefGoogle Scholar
Lewis, SEM (2015) Should sperm DNA fragmentation testing be included in the male infertility work-up? Reprod Biomed Online 31, 134–7.CrossRefGoogle ScholarPubMed
Lewis, SEM and Simon, L (2010) Clinical implications of sperm DNA damage. Hum Fertil 13, 201–7.CrossRefGoogle ScholarPubMed
Maier, WM, Nussbaum, G, Domenjoud, L, Klemm, U and Engel, W (1990) The lack of protamine 2 (PT2) in boar and bull spermatozoa is due to mutations within P2 gene. Nucleic Acids Res 18, 1249–54.CrossRefGoogle Scholar
McLay, DW and Clarke, HJ (2003) Remodeling the paternal chromatin at fertilization in mammals. Reproduction 125, 625–33.CrossRefGoogle Scholar
McPherson, S and Longo, FJ (1993) Chromatin structure function during mammalian spermatogenesis: DNA nicking repair in elongating spermatids. Eur J Histochem 37, 109–28.Google ScholarPubMed
Menezo, Y, Dale, B and Cohen, M (2010) DNA damage and repair in human oocytes and embryos: a review. Zygote 18, 357–65.CrossRefGoogle ScholarPubMed
Oliva, R (2006) Protamines and male fertility. Hum Reprod Update 12, 417–35.CrossRefGoogle Scholar
Perez, MA, Rocha, AM, Vannuchi, CI, Mendes, CM, Cavalcanti, PV, Nichi, M, Ambrosio, CE, Miglino, MA, Visintin, JA and Assumpção, MEOA (2014) Semen analysis of Golden Retriever healthy dogs and those affected by muscular dystrophy. Andrologia 46, 277–82.CrossRefGoogle Scholar
Queralt, R, Adroer, R, Oliva, R, Winkfein, RJ, Retief, JD and Dixon, GH (1995) Evolution of protamine P1 genes in mammals. J Mol Evol 40, 601–7.CrossRefGoogle ScholarPubMed
Quintero-Moreno, A, Ramirez, ML, Nava-Trujillo, H, Osorio, C, Rodríguez-Gil, JE and Hidalgo, M (2010) Toluidine blue as stain for optimal morphometric evaluation of frozen–thawed bull spermatozoa. Reprod Dom Anim 45, 104–5.Google Scholar
Ribas-Maynou, J and Benet, J (2019) Single and double strand sperm DNA damage: different reproductive effects on male fertility. Genes 10, 105–18.CrossRefGoogle ScholarPubMed
Ribas-Maynou, J, Garcia-Peiro, A, Fernanez-Encinas, A, Abad, C, Amenguai, MJ, Prada, E, Navarro, J and Benet, J (2013) Comprehensive analysis of sperm DNA fragmentation by five different assays: TUNEL assay, SCSA, SCD test and alkaline and neutral comet assay. Andrology 1, 715–22.CrossRefGoogle ScholarPubMed
Ribas-Maynou, J, Garcia-Peiro, A, Fernanez-Encinas, A, Amenguai, MJ, Prada, E, Cortes, P, Navarro, J and Benet, J (2012) Double stranded sperm DNA breaks, measured by comet assay are associated with unexplained recurrent miscarriage in couples without a female factor. PLoS One 7, e44679.CrossRefGoogle ScholarPubMed
Ribas-Maynou, J Gawecka, JE, Benet, J and Ward, WS (2014) Double-stranded DNA breaks hidden in the neutral comet assay suggest a role of the sperm nuclear matrix in DNA integrity maintenance. Mol Hum Reprod 20, 330–40.CrossRefGoogle ScholarPubMed
Ribeiro, S, Sharma, R, Gupta, S, Cakar, Z, De Geyter, C and Agarwal, A (2017) Inter-m and intra-laboratory standardization of TUNEL assay for assessment of sperm DNA fragmentation. Andrology 5, 477–85.CrossRefGoogle Scholar
Rocha, HLOG, Beletti, ME, Marcolini, TT and Amorin, DAZ (2002) The use of acridine orange and toluidine blue in the evaluation of male fertility. Biosci J 18, 6577.Google Scholar
Rodrigues, H, Ohanian, C and Bustos Obregon, E (1985) Nuclear chromatin decondensation of spermatozoa in vitro: a method for evaluating the fertilizing ability of ovine semen. Int J Androl 8, 147–58.CrossRefGoogle Scholar
Rui, BR, Angrimani, DSR, Bicudo, LC, Losano, JDA, Nichi, M and Pereira, RJG (2018) A fast, low-cost and efficient method for the diagnosis of sperm DNA fragmentation in several species. Reprod Dom Anim 53,171–5.CrossRefGoogle Scholar
Rui, BR, Shibuya, FY, Kawaoku, AJT, Losano, JDA, Angrimani, DSR, Dalmazzo, A, Nichi, M and Pereira, RJ (2017) Impact of induced levels of specific free radicals and malondialdehyde on chicken semen quality and fertility. Theriogenology 90, 11–9.CrossRefGoogle ScholarPubMed
Sakkas, D and Alvarez, JG (2010) Sperm DNA fragmentation: mechanisms of origin, effect on reproductive outcome, and analysis. Fertil Steril 93, 1027–46.CrossRefGoogle Scholar
Sakkas, D, Moffatt, O, Manicardi, GC, Mariethoz, E, Tarozzi, N and Bizarro, D (2002) Nature of DNA damage in ejaculated human spermatozoa and the possible involvement of apoptosis. Biol Reprod 66, 1061–7.CrossRefGoogle Scholar
Saleh, R, Agarwal, A, Nada, E, El-Tonsy, M, Sharma, R, Meyer, A, Nelson, DR and Thomas, AJ (2003) Negative effects of increased sperm DNA damage in relation to seminal oxidative stress in men with idiopathic an male factor infertility. Fertil Steril 79, 1597–605.CrossRefGoogle ScholarPubMed
Sardoy, MC, Carretero, MI and Neild, DM (2008) Evaluation of stallion sperm DNA alterations during cryopreservation using toluidine blue. Anim Reprod Sci 107, 349–50.CrossRefGoogle Scholar
Schluter, G and Engel, W (1995) The rat PRM3 gene is an intronless member of the protamine gene cluster and is expressed in haploid male germ cells. Cytogenet Cell Genet 71, 352–5.Google ScholarPubMed
Seligman, J, Kosower, NS, Weissenberg, R and Shalgi, R (1994) Thiol-disulfide status of human sperm proteins. J Reprod Fertil 101, 435–43.CrossRefGoogle ScholarPubMed
Serafini, R, Romano, JE, Varner, DD, Di Palo, R and Love, CC (2015) Sperm DNA assays and their relationship to sperm motility and morphology in bull (Bos taurus ) Anim Reprod Sci 159, 7786.CrossRefGoogle ScholarPubMed
Serafini, R, Varner, DD, Bisset, WJ, Blachard, TL, Teague, SR and Love, CC (2017) The effect of flash-freezing temperature on stallion sperm DNA structure. Theriogenology 95, 113–7.CrossRefGoogle ScholarPubMed
Serafini, R, Varner, DD, Blanchard, TL, Teague, SR, LaCaze, K and Love, CC (2018) Effects of seminal plasma and flash-freezing on DNA structure of stallion epididymal sperm exposed to different potentiators of DNA damage. Theriogenology 117, 34–9.CrossRefGoogle ScholarPubMed
Shamsi, MB, Imam, SN and Dada, R (2011) Sperm DNA integrity assays: Diagnostic and prognostic challenges and implications in management of infertility. J Assist Reprod Genet 28, 1073–85.CrossRefGoogle ScholarPubMed
Sharif, K (2013) Sperm DNA fragmentation testing: to do or not to do? Middle East Fertil Soc J 18, 7883.CrossRefGoogle Scholar
Sharma, R, Ahmad, G, Esteves, SC and Agarwal, A (2016) Terminal deoxynucleotidyl transferase dUTP nick end labling (TUNEL) assay using bench top flow cytometer for evaluation of sperm DNA fragmentation in fertility laboratories: protocol, reference values, and quality control. J Assist Reprod Genet 33, 291300.CrossRefGoogle Scholar
Sharma, RK, Sabanegh, E, Mahfouz, R, Gupta, S, Thiyagarajan, A and Agarwal, A (2010) TUNEL as a test for sperm DNA damage in the evaluation of male infertility. Urology 76, 1380–6.CrossRefGoogle ScholarPubMed
Shukla, KK, Mahdi, AA and Rajender, S (2012) Apoptosis, spermatogenesis and male infertility. Front Biosci 1, 746–54.CrossRefGoogle Scholar
Simões, R, Feitosa, WB, Mendes, CM, Marques, MG, Nicacio, AC, Barros, FRO, Visintin, JA and Assumpção, MEOD (2009) Use of chromomycin A3 staining in bovine sperm cells for detection of protamine deficiency. Biotech Histochem 84, 7983.CrossRefGoogle ScholarPubMed
Simon, L and Carrell, DT (2013) Sperm DNA damage measured by comet assay. Methods Mol. Biol. 927: 137–46.CrossRefGoogle ScholarPubMed
Simon, L, Lui, L, Murphy, K, Ge, S, Hotaling, J, Aston, KI, Emery, B and Carrell, DT (2014a) Comparative analysis of three sperm DNA damage assays and sperm nuclear protein content in couples undergoing assisted reproduction treatment. Hum Reprod 29, 904–17.CrossRefGoogle ScholarPubMed
Simon, L, Murphy, K, Shamsi, MB, Liu, L, Emery, B, Aston, KI, Hotaling, J and Carrell, DT (2014b) Paternal influence of sperm DNA integrity on early embryonic development. Hum Reprod 29, 2402–12.CrossRefGoogle ScholarPubMed
Sotolongo, B, Huang, TTF, Isenberger, E and Ward, S (2005) An endogenous nuclease in hamster, mouse and human spermatozoa cleaves DNA into loop-sized fragments. J Androl 26, 272–80.CrossRefGoogle ScholarPubMed
Steger, K and Balhorn, R (2018) The nuclear protamines: a checkpoint to control sperm chromatin quality. Anat Histol Embryol 47, 273–9.CrossRefGoogle ScholarPubMed
Suganuma, R, Yanagimachi, R and Meistrich, ML (2005) Decline in fertility of mouse sperm with abnormal chromatin during epididymal passage as revealed by ICSI. Hum Reprod 20, 3101–8.CrossRefGoogle ScholarPubMed
Tamburrino, L, Marchiani, S, Montoya, M, Marino, FE, Natali, I, Cambi, M, Forti, G, Baldi, E and Muratori, M (2012) Mechanisms and clinical correlates of sperm DNA damage. Asian J Androl 14, 24–31.CrossRefGoogle ScholarPubMed
Tesarik, J, Mendoza, C and Greco, E (2002) Paternal effects acting during the first cell cycle of human preimplantation development after ICSI. Hum Reprod 17, 184–9.CrossRefGoogle ScholarPubMed
Vilfan, IDF, Conwell, CC and Hud, N (2004) Formation of native like mammalian sperm cell chromatin with folded bull protamine. J Biol Chem 279, 2088–95.CrossRefGoogle ScholarPubMed
Ward, WS and Coffey, DS (1991) DNA packaging and organization in mammalian spermatozoa: comparison with somatic cells. Biol Reprod 37, 569–74.CrossRefGoogle Scholar
Wdowiak, A, Bakalczuk, S and Bakalczuk, G (2015) The effect of sperm DNA fragmentation on the dynamics of the embryonic development in intracytoplasmatic sperm injection. Reprod Biol 5, 94100.CrossRefGoogle Scholar
Wouters-Tyrou, D, Martinage, A, Chevaillier, P and Sautiére, P (1998) Nuclear basic proteins in spermiogenesis. Biochimie 80, 117–28.CrossRefGoogle ScholarPubMed
Yebra, L and Oliva, R (1993) Rapid analysis of mammalian sperm nuclear proteins. Anal Biochem 209, 201–3.Google ScholarPubMed
Yeste, M, Estrada, E, Casas, I, Bonet, S and Rodríguez-Gil, JE (2013) Good and bad freezability boar ejaculates differ in the integrity of nucleoprotein structure after freeze-thawing but not in ROS levels. Theriogenology 79, 929–39.CrossRefGoogle ScholarPubMed
Zini, A and Agarwal, A (2011a) Spermatogenesis: an overview. In: Sharma, R and Agarwal, A. Sperm chromatin. Biological and clinical applications in male infertility and assisted reproduction. 1st edn. New York, USA: Springer, pp. 277–94.Google Scholar
Zini, A and Agarwal, A (2011b) TUNEL assay. In: Sharma, R and Agarwal, A. Sperm chromatin. Biological and clinical applications in male infertility and assisted reproduction. 1st edn. New York, USA: Springer, pp. 201–16.Google Scholar
Zubkova, EV, Wade, M and Robaire, B (2005) Changes in spermatozoal chromatin packaging and susceptibility to oxidative challenge during aging. Fertil Steril 84, 1191–8.CrossRefGoogle ScholarPubMed