Review of Sexual Maturity in the Minipig

Abstract

It is important to know whether the animals used in toxicology studies are sexually mature. As minipigs are being used increasingly in toxicity studies, we reviewed published data on the age of sexual maturity in the minipig. Maturity in females was assessed on the basis either of normal cycles of progesterone secretion or of the histological presence of corpora lutea and, in males, was assessed on the histological appearance of the seminiferous tubules and epididymides. In female Gö ttingen minipigs, the first progesterone peak was at 3.7 to 4.2 or 6.1 to 6.5 months of age. These animals were in the presence of a boar. In female Gö ttingen minipigs in toxicology studies, which were not in the presence of a boar, at least 1 corpus luteum in the ovaries was present in only 50% of the females by 6.5 months of age, while all were mature by 7.7 months of age. Histological maturity in the male Yucatan minipig is reported to be attained at about 4.4 months old, but in male Göttingen minipigs at about 2 months old, although the definition of maturity may have been different in the 2 studies.

Miniature pig model of human adolescent brain white matter development

“…A longitudinal imaging protocol was used to assess changes in WM integrity during normal adolescent maturation in miniature pigs. The trends of WM DWI measurements were similar to these observed during the period of adolescence and young adulthood in humans (Kochunov et al, 2012; Grinberg et al, 2017; Howroyd et al, 2016; Peter et al, 2016). In addition to the rise in DTI-FA values, we observed significant changes in two DWI parameters that describe the non-Gaussian diffusion properties KA and PDI.…”

Comparative Aspects of Pre‐ and Postnatal Development of the Male Reproductive System

“…For example, some authors report the day of mating as gestation day (GD) 0 or 1 or consider the day of birth to be postnatal day (PND) 0 or 1, depending on the time of day that parturition is either initiated or completed. While referring to developmental milestones, “sexual maturity” has been used by some authors to indicate onset of puberty, puberty, or early adult stages (Evans et al, ; Howroyd et al, ; Taberner et al, ).…”

Proceedings of the 2018 National Toxicology Program Satellite Symposium

“…However, as there is considerable histological variation in Leydig cell numbers, size, and appearance in normal mature control boars, toxic effects on Leydig cells must be carefully evaluated, as true hypertrophy/hyperplasia is difficult to determine. Hypertrophy/hyperplasia would need to be quite pronounced, including extensive crowding of nuclei and slight compression of tubules to warrant a diagnosis (van Straaten and Wensing 1977; Allrich et al 1983; Howroyd, Peter, and de Rijk 2016; Kangawa et al 2016). There was some discussion around whether the variability in Leydig cell prominence should be recorded in toxicology studies, with more prominent accumulations being recorded as hypertrophy/hyperplasia.…”