
%0 Journal Article
%A Petersen, M. M. 
%A Boe-Hansen, G. B. 
%A Birck, A. 
%A Avery, B. 
%A Jensen, M. 
%A Bøgh, I. B. 
%T 309 DIFFERENCES IN PRONUCLEUS FORMATION RATES BETWEEN BULLS IN RESPONSE TO GAMMA IRRADIATION OF FROZEN&#8211;THAWED SEMEN
%J Reproduction, Fertility and Development
%D 2006/12/12
%V 19
%N 1
%P 270-270
%K 
%R https://doi.org/10.1071/RDV19N1AB309
%U https://www.publish.csiro.au/paper/RDV19N1AB309 
%X Gamma irradiation induces DNA damage to mature bovine spermatozoa but does not affect motility, membrane integrity, or function (Fatehi et al. 2006 J. Androl. 27, 176&#8211;188), making it a useful model to evaluate the effect of fertilization with DNA-damaged spermatozoa. The objective of the present study was to analyze the fertilizing capacity of frozen&#8211;thawed gamma-irradiated sperm from 2 bulls: a bull with a high sperm quality and fertilization rate (bull A), and a bull with a low sperm quality and fertilization rate (bull B). To ensure that DNA damage was induced, frozen&#8211;thawed semen was exposed to a high dose of irradiation (90 Gy). Cumulus&#8211;oocyte complexes were obtained from abattoir ovaries and were in vitro-matured (IVM) using standard procedures (23 h in DMEM with 5% serum and eCG/hCG). For each treatment group, 3 to 5 straws of semen from the same ejaculate were used. After thawing, semen from the 2 bulls was either irradiated or held at room temperature before 1:1 dilution in sperm-TALP. During irradiation, semen was kept in the straws. The irradiated and nonirradiated sperm were used for IVF (23 h in IVF-TALP) within 1 h of thawing. IVM and IVF were carried out at 38.5°C in 5% CO2 in air. After IVF, presumptive zygotes were whole mount-fixed and 24 h later were stained with 1% aceto-orcein followed by determination of fertilization status. Fertilization was considered normal if 2 pronuclei (PN) were present. A total of 4 replicates were performed and 286 zygotes analyzed. No difference was detected between replicates, and the results were pooled. Fisher&apos;s exact test was used to determine effect of treatment. More zygotes had 2 PN after fertilization with semen from bull A (47/67 &equals; 70&percnt;), compared with that from bull B (16/71 &equals; 23&percnt;; P < 0.0001) using nonirradiated sperm. Irradiation of sperm significantly increased the fraction of zygotes with 2 PN from bull A (61/70 &equals; 87&percnt;; P &equals; 0.03), but decreased the 2 PN fractions in zygotes fertilized with sperm from bull B (2/75 &equals; 3&percnt;; P &equals; 0.0002). Ideally, to avoid straw variation, semen should have been pooled and divided into groups before irradiation. The variation between straws might explain the higher fertilization rates in bull A using irradiated sperm compared with nonirradiated sperm. In conclusion, there appear to be differences in fertilizing ability between bulls after irradiation of frozen&ndash;thawed sperm. This could be due to suboptimal DNA packaging, which made sperm from bull B more susceptible to radiation-induced damage. The potential irradiation-induced increase in DNA fragmentation in sperm from bull B compared with that from bull A might delay or prevent the formation of the 2 PN. Further studies are needed to investigate differences in fertilization and early embryonic development using sperm with intact or damaged DNA. 
