Safety assessment of poly(N-vinylcaprolactam) as a potential drug carrier in extenders for boar sperm cryopreservation.

Polymers may be used to deliver compounds in freezing extenders to minimize injuries in spermatozoa during cryopreservation, although their activity and toxicity for boar sperm are unknown. This study investigated the effects of the polymer (N-vinylcaprolactam) (PNVCL), when included in extenders for boar sperm cryopreservation. In Experiment 1, sperm was exposed to PNVCL at: 0 (control); 39.1; 78.1; 156.3; and 312.5 µg/mL. Spermatozoa structure, kinetics and biochemical functions were unaltered in contact with PNVCL at 38 °C (P > .05) but declined with prolonged exposure (10, 60 and 120 min) in all treatments (P > .05). In Experiment 2, after inclusion of PNVCL in the freezing extender at the same concentrations, post-thawing sperm quality did not differ compared to the control (P > .05). Lipid peroxidation and the production of reactive oxygen species were the only parameters of sperm quality that were unaffected in both experiments, even after contact with PNVCL for 120 min (P > .05). As no negative effects were observed in post-thawing boar sperm quality, PNVCL did not incur in cytotoxicity and may be a potential carrier for antioxidants in freezing extenders.

Bioassay of mannitol and caprolactam and assessment of response to diethylnitrosamine in heterozygous p53-deficient (+/-) and wild type (+/+) mice.

Alternative bioassays of mannitol (MAN) and caprolactam (CAP) were conducted in transgenic p53-deficient mice. Also, to assess the sensitivity of the transgenic mice to a model DNA-reactive carcinogen, the hepatic effects of diethylnitrosamine (DEN) were compared in the wild type background strain of mouse and in the transgenic derivative. Fifty-one male wild type strain C57BL/6 mice p53 (+/+), 8 weeks old, and 51 heterozygous p53 (+/-) C57BL/6 Tac-[KO] Trp53 N5 mice, 8 weeks old, were allocated to six experimental groups as follows: groups 1 (wild type +/+) and 2 (p53 +/-) served as room controls, groups 3 (+/+) and 4 (+/-) were exposed orally (gavage) to 50 mumol/kg body weight DEN weekly for a total of ten doses during the first 10 weeks of the study, group 5 (+/-) was exposed to 15,000 ppm CAP in the diet for up to 26 weeks, and group 6 (+/-) was exposed to 50,000 ppm MAN in the diet for up to 26 weeks. After 10 weeks, liver from control and DEN-exposed mice was used for O4-ethylthymidine (O4-EtT) DNA adduct analysis by the immunoslot blot method. The cell replicating fraction (RF) in the liver was determined by quantification of the percentage of immunohistochemically stained hepatocytes positive for proliferating cell nuclear antigen. No significant or consistent body or liver weight changes were present in any of the treatment groups. No consistent and pertinent changes in RF values were present in any of the treatment groups. None of the tested substances produced neoplasms of any type in p53 (+/-) mice. DEN induced comparable levels of O4-EtT adducts in the liver in both wild type and p53 +/- genotypes, but no morphologic changes were evident in the livers of either genotype. The lack of response to DEN, in spite of formation of DNA adducts, may reflect the resistance to hepatocarcinogenesis of the background C57BL/6 strain of the transgenic, and calls into question the general sensitivity of this transgenic for detection of carcinogenic effects.