Male Reproductive Toxicology

The objective of this paper is to discuss recent developments in the application of biological markers to animal models of male reproductive toxicology. We have divided this paper into three major sections: First, a discussion of the testing protocols currently under investigation by the National Toxicology Program (NTP) and the EPA's Health Effects Research Laboratory; second, an examination of what we consider to be important and practical biological markers available to investigators to assess the effects of toxicants on the male reproductive system; and third, a discussion of promising new technologies, such as molecular and immunological probes, and in vitro techniques using isolated and cultured cells, which in the future may be exploited for the development of additional biological markers of male reproductive toxicity. Where appropriate we have made specific recommendations for the use of these biological markers in animal protocols and have pointed out those noninvasive markers which have application to screening human males.

The peptide fraction of Bothrops jararaca snake venom induces toxicological effects on the male reproductive system after local envenomation in mice

Bothrops envenomation is complex and provokes prominent local tissue damage and systemic disturbances,but little is known about their effects on the male reproductive system.After intratesticular injection,the bioactive peptide fraction(Bj-PF)obtained from Bothrops jararaca snake venom changes the structure of different stages of the seminiferous epithelium cycle in adult mice.For the first time,we investigated whether local envenomation of Bj-PF induces toxicological effects on the male reproductive system,particularly on the seminiferous epithelium and Sertoli cells.Male adult mice were treated with 0.24 mg.kg^(-1) by intramuscular(i.m.)injection for 24 h.The testes samples were collected for morphological and morphometric evaluation.The toxicological effects of Bj-PF were also analyzed on mitochondrial metabolism and nitrite(NO2)production in 15P-1 Sertoli cell culture.Bj-PF changed the structure and function of the seminiferous epithelium,particularly the disruption of the epithelium and the presence of degenerated germ cells in the adluminal compartment,but there were no alterations in the basal compartment.Bj-PF increased the thickness of the seminiferous epithelium and decreased the lumen diameter of the tubule.Semiquantitative histological assessment of the degree of tubule degeneration revealed that Bj-PF also increased the number of hypospermatogenic tubules compared to control.Bj-PF reduced NO2 levels in 15P-1 Sertoli cells without changing the mitochondrial metabolism.Overall,the fact that Bj-PF alters the structure and function of the seminiferous epithelium suggests that bioactive peptides found in B.jararaca snake venom can have toxicological effects on the reproductive systems of affected male mice,providing new insight into the biological characteristics of snake venom and therapeutic strategies for envenomation inflammation.

An Overview on Biological Markers in Reproductive and Developmental Toxicology: Concepts, Definitions and Use in Risk Assessment

Reproduction and development are complex couple-dependent processes. Risk assessment for these health outcomes requires the use of biomarkers to link exposures to disease. Biological markers of susceptability, external dose, internal dose, biologically effective dose, early or late biological responses, altered reproductive or developmental function, and reproductive or developmental disease are introduced. Using these biomarkers it is possible to define a biologically based risk assessment methodology for reproductive and developmental toxicity. Risk assessment for reproductive toxicity requires definition of male and female fecundity, couple-specific factors, spontaneous abortion, rate, and other factors. Using using sperm count as a biomarker for male fecundity, an example of a reproductive risk assessment using biomarkers is performed.

Assessing human sperm morphology： top models, underdogs or biometrics？

The assessment of the percentage of spermatozoa having an ＇ideal＇ morphology using so-called strict method is the method recommended in the latest edition of the World Health Organization （WHO） laboratory manual for semen analysis. This recommendation is a result of the statistical association between ＇ideal＇ sperm morphology and fertility, and of the current general belief that sperm morphology assessment should be used primarily as a fertility tool. The notion of an ＇ideal＇ sperm morphology has persisted despite the very low percentage of such spermatozoa in the semen of fertile men, a subject of intense controversy. The detailed categorization of each abnormal spermatozoon has thus, for a long time, been considered optional and partially redundant, an idea which is reflected in the earlier editions of the WHO manual. However, several recent studies have shown the importance of carefully assessing abnormal sperm morphology for use in the diagnosis ＆infertility, to determine fertility prognosis, and for basic or public health studies. One approach, which combines videomicroscopy and computer vision, and is the only approach able to assess the continuum of sperm biometrics, has been used successfully in several recent clinical, basic and toxicology studies. In summary, the visual assessment of detailed sperm morphology--including the categorization of anomalies allowing arithmetically derived indices of teratozoospermia--and the more modern computer-based approaches, although often considered to be redundant, are in fact complementary. The choice of the most appropriate method depends on the field of investigation （clinical, research, toxicology） and the problem being addressed. Each approach has advantages as well as certain limitations, which will be discussed briefly herein.