The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and differential diagnosis for classifying microscopic lesions observed in the male reproductive system of laboratory rats and mice, with color microphotographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available for society members electronically on the Internet (http://goreni.org). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for lesions of the male reproductive system in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Background Bisphenol S (BPS) is increasingly used as a replacement for bisphenol A in the manufacture of products containing polycarbonates and epoxy resins. However, further studies of BPS exposure are needed for the assessment of health risks to humans. In this study we assessed the potential harmfulness of low-dose BPS on reproduction in male mice. Methods To simulate human exposure under experimental conditions, 8-week-old outbred ICR male mice received 8 weeks of drinking water containing a broad range of BPS doses 0.001, 1.0, or 100 µg/kg body weight (bw)/day, BPS1-3 or vehicle control. Mice were sacrificed and testicular tissue taken for histological analysis and protein identification by nano-liquid chromatography/mass spectrometry (MS) and sperm collected for immunodetection of acetylated lysine and phosphorylated tyrosine followed by protein characterisation using matrix-assisted laser desorption ionisation time-of-flight MS (MALDI-TOF MS). Results The results indicate that compared to vehicle, 100 µg/kg/day exposure (BPS3) leads to 1) significant histopathology in testicular tissue; and, 2) higher levels of the histone protein γH2AX, a reliable marker of DNA damage. There were fewer mature spermatozoa in the germ layer in the experimental group treated with 1 µg/kg bw (BPS2). Finally, Western blot and MALDI-TOF MS studies showed significant alterations in the sperm acetylome and phosphorylome in mice treated with the lowest (BPS1) exposure (0.001 µg/kg/day). Conclusions In summary, this range of qualitative and quantitative findings in young male mice raise the possibility that relatively low doses of BPS may impair mammalian reproduction through epigenetic modifications of sperm proteins.

Toxicologic disturbance of male reproductive function can occur at many sites and produce a range of effects, some primary and some secondary to the initial insult. The challenge to the toxicological pathologist is to identify the primary site of damage and provide an insight into the pathogenesis of the morphologic lesion or functional deficit. Target sites include the testis, the epididymis, the mature sperm, and the hormonal regulatory system. Detection of effects at these varied sites requires the measurement of multiple endpoints only 1 of which is histopathology, but once identified, careful microscopic examination of the early changes in lesion development can provide essential information on the probable target cell and possible mechanisms of toxicity. Chemicals that affect different cell types or specific cellular functions generally elicit predictable patterns of pathological changes that can be readily recognized. Understanding the pathogenesis, the likely reversibility and the significance of reproductive tract lesions is aided by a sound knowledge of the physiology of the testis and epididymis and, in particular, an understanding of the timing of sperm production and transport.

Stress often occurs during toxicity studies. The perception of sensory stimuli as stressful primarily results in catecholamine release and activation of the hypothalamic-pituitary-adrenal (HPA) axis to increase serum glucocorticoid concentrations. Downstream effects of these neuroendocrine signals may include decreased total body weights or body weight gain; food consumption and activity; altered organ weights (e.g., thymus, spleen, adrenal); lymphocyte depletion in thymus and spleen; altered circulating leukocyte counts (e.g., increased neutrophils with decreased lymphocytes and eosinophils); and altered reproductive functions. Typically, only some of these findings occur in a given study. Stress responses should be interpreted as secondary (indirect) rather than primary (direct) test article-related findings. Determining whether effects are the result of stress requires a weight-of-evidence approach. The evaluation and interpretation of routinely collected data (standard in-life, clinical pathology, and anatomic pathology endpoints) are appropriate and generally sufficient to assess whether or not changes are secondary to stress. The impact of possible stress-induced effects on data interpretation can partially be mitigated by toxicity study designs that use appropriate control groups (e.g., cohorts treated with vehicle and subjected to the same procedures as those dosed with test article), housing that minimizes isolation and offers environmental enrichment, and experimental procedures that minimize stress and sampling and analytical bias.This article is a comprehensive overview of the biological aspects of the stress response, beginning with a Summary (Section 1) and an Introduction (Section 2) that describes the historical and conventional methods used to characterize acute and chronic stress responses. These sections are followed by reviews of the primary systems and parameters that regulate and/or are influenced by stress, with an emphasis on parameters evaluated in toxicity studies:

Most recent revisions of regulatory guidelines for testing effects of chemicals on reproduction recommend Bouin's fluid (BF) or a "comparable fixative" instead of formalin to preserve the morphologic detail of testes for histopathological evaluation. However, picric acid in BF is a health and safety hazard, as well as a laboratory waste disposal problem. Furthermore, use of BF is labor intensive, requiring multiple alcohol rinses to remove picric acid for optimum preservation and immunohistochemical (IHC) detection of testicular antigens that may potentially be used to identify and quantify cells and functional proteins with critical roles in spermatogenesis. Recently a modified Davidson's fluid (mDF) has been reported as an alternative to BF to fix testes for routine histopathological examination. This study compared the overall histomorphologic clarity and the immunoand histochemical staining of testicular specimens fixed in BF and mDF. Additionally, because conventional Davidson's fixative (DF) is used routinely for optimum fixation of eyes, preservation of ocular histomorphology by DF and mDF was compared. mDF resulted in noticeably less shrinkage of the seminiferous tubules and superior overall morphologic detail compared to BF. Unlike DF, the mDF also supported excellent staining of acrosomes with periodic acid-Schiff (PAS) reagent when staging of spermatogenesis was required. IHC detection of androgen receptor and PCNA (to directly and indirectly identify Sertoli cells) as well as protein gene product 9.5 (to label spermatogonia) was superior in mDF compared to BF-fixed specimens. For histopathological examination of the eye, apposition and preservation of rods and cones, and nuclear layers of the retina were slightly inferior with mDF compared to DF. This paper has demonstrated that mDF provides comparable, and in many respects superior preservation of the testes to that of BF, both for IHC staining and for detailed histopathological examination. It also provides an acceptable fixative for eyes, although the quality of cellular preservation is inferior to that of DF.