Male reproductive health in environmental research
There is increasing concern that chemicals in the environment are causing male reproductive disorders in animals and humans. This thesis investigated different aspects of histological evaluation of testes, as a tool to measure effects of environmental chemicals on male reproductive health in wild an...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | Swedish English |
| Published: |
2018
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| Online Access: | https://pub.epsilon.slu.se/15728/ https://pub.epsilon.slu.se/15728/7/sporndly_nees_e_181030.pdf |
| Summary: | There is increasing concern that chemicals in the environment are causing male reproductive disorders in animals and humans. This thesis investigated different aspects of histological evaluation of testes, as a tool to measure effects of environmental chemicals on male reproductive health in wild and laboratory animals. When collecting samples from wild animals, unpredictable conditions can result in poor fixation of tissues and robust endpoints are therefore important. In mink, testis length and weight, area and diameter of seminiferous tubules and acrosome marked with Gata-4 were found to be the most reliable measurements after delayed pre-fixation time. Knowledge of the normal morphology and seasonality of testes is crucial when evaluating male reproduction. Staging of the seminiferous tubules in mink and polar bear is described in this thesis. A computerised image analysis method, including semi-automatic delineation of seminiferous tubules, was developed to objectify and improve measurements of testicular tissue. The method was used to measure the area and diameter of tubules in polar bear, rat and mink. Gata-4 was used as the key component in developing a novel morphology-based approach for evaluating testicular development in pubertal laboratory rats. In controlled settings, effects of a single chemical, bisphenol A (BPA), was investigated in Fisher rats. No major effects on male reproduction in midpubertal or adult rats were seen, apart from higher prevalence of mild inflammatory cell infiltrate in cauda epididymis in adult rats exposed to 50 µg BPA/kg bw/day in utero and during lactation. In polar bears, testes histology and organ measurements enabled identification of reproductive status, independent of season and age. Reproductive organ measurements were found to differ with reproductive status, stressing the importance of considering this factor when evaluating effects of chemicals in polar bear. Inverse correlations between testes and baculum measurements and oxychlordane concentrations indicated that this chemical may cause reproductive disruption in East Greenland polar bears. Another sign of disturbed reproduction was disorganisation of germ cells in testis, seen in half of all polar bears with active sperm production, but no correlations to target chemicals were detected. In conclusion, the factors season, reproductive status and handling of tissues prior to fixation must be taken into consideration when evaluating testis histology and organ weight, in order to obtain accurate results and draw correct conclusions. Computerised image analysis proved to be a useful objective tool when evaluating testis histology in polar bear, mink and rat. |
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