Characterization of an L-amino acid oxidase in equine spermatozoa.

This study demonstrates for the first time the presence of an L-amino acid oxidase (LAAO) enzyme in equine spermatozoa that is able to generate significant amounts of reactive oxygen species (ROS) and create a state of oxidative stress. RT-PCR analysis revealed that the mRNA for this enzyme was present in the equine testis and spermatozoa, while immunocytochemical studies demonstrated that the mature LAAO protein was located in the sperm head, particularly in the acrosomal and postacrosomal domains. Experimental studies demonstrated that the aromatic amino acids (L-phenylalanine > L-tryptophan > L-tyrosine) were substrates for this enzyme, eliciting the dose- and time-dependent generation of ROS via mechanisms that were enhanced by cell death. This unexpected result was confirmed by analyses of ROS generation in subcellular sperm fractions, which again located a majority of LAAO activity to the sperm head. Equine cryopreservation medium was shown to contain sufficient quantities of aromatic amino acids to activate the LAAO system and generate ROS. The biological significance of this activity was established in an experiment in which physiological concentrations of aromatic amino acids were found to suppress sperm motility but only if dead spermatozoa were present in the same suspension. The combination of aromatic amino acids and nonviable cells was also found to enhance the levels of lipid peroxidation in live spermatozoa. These results suggest the potential significance of LAAO activity in generating the oxidative stress associated with the cryopreservation of equine spermatozoa. It is possible that inhibitors of this enzyme system may facilitate the development of modified cryostorage regimes for clinical validation in vivo.

Student perspectives of preparedness characteristics for clinical learning within a fully distributed veterinary teaching model.

The transition into the clinical environment is challenging and associated with significant stress and anxiety. This study aimed to examine the perspectives of students on the characteristics important for preparedness for clinical learning and the influence of gender, age, and graduate status on those perspectives. This descriptive, questionnaire-based study of 62 characteristics categorised into six themes was conducted within the Surrey School of Veterinary Medicine completed by 139 students commencing their final clinical year. The Friedman test and post-hoc Wilcoxon signed rank sum test explored for differences in ranking across the themes. Ordinal logistic regression and Mann-Whitney U pairwise comparisons were utilised to investigate for effects of gender, age, and graduate status on theme ranking. There was a significant difference (P <0.05) between medians for themes of preparedness characteristics with comparisons revealing willingness and communication and interaction as the most highly rated characteristics. Knowledge and understanding were viewed as the least important characteristic. Regression and pairwise Mann-Whitney U comparisons confirmed no significant effects (P >0.05) of gender, age or graduate status on student rating of preparedness characteristics. Integrating learning opportunities of those preparedness characteristics in the pre-clinical curriculum may improve students' preparedness for the clinical environment.