Duration of epididymal sperm transit in hamster: an autoradiographic study

Canine spermatozoa-What do we know about their morphology and physiology? An overview

Spermatozoa are unique cells because of their morphological and physiological characteristics. They are produced during the process called spermatogenesis. Spermatogenesis consists of three phases: spermatocytogenesis, spermiogenesis and spermiation, during which spermatozoa undergo several changes. Spermatogenesis takes place within the seminiferous tubules containing two types of cells-the germ cells and the Sertoli cells-that alongside the Leydig cells, which play an important role when it comes to normal fertility. Everything is regulated by the hypothalamic-pituitary-gonadal axis and specific hormones due to multi-hormonal feedback systems. Spermatozoa possess morphological and physiological features, which are sometimes completely different from what is observed in various somatic cells. What is more, canine spermatozoa have specific characteristics making them special compared to the spermatozoa of other mammalian species. The metabolic energy production, which is crucial for the appropriate functioning of spermatozoa, can be fuelled by different metabolic pathways utilizing different chemical substrates. Inseparable from the oxidative phosphorylation process is the production of reactive oxygen species, which are both essential and toxic to spermatozoa. Furthermore, epididymis is a very important structure, responsible for the transport and maturation of spermatozoa, which are then stored in the last segment of epididymis-the epididymal cauda. Moreover, the retrieval of spermatozoa from the epididymides is crucial for the development of assisted reproduction techniques and sperm cryopreservation methods. The information gained from the research on domestic dogs might be transferred to their wild relatives, especially those species categorized as endangered.

Impact of neonatal hypothyroidism on reproduction in the male hamster, Mesocricetus auratus

Thyroid hormones play an important role in brain development. In the present study, we examined the influence of transient postnatal hypothyroidism on reproductive neuroendocrine and behavioral outcomes in the male Syrian (golden) hamster. Hamster pups were rendered hypothyroid following exposure to the goitrogen, 6-n-propyl-2-thiouracil (PTU), between postnatal (PN) day 0 (birth) and PN25 (weaning). By 15 days after cessation of PTU, exposure (PN40) serum thyroxine levels had returned to control levels. The testes of treated males were approximately 30% heavier than controls and daily sperm production was increased by 73%. Immunocytochemistry for GnRH revealed that the total number of GnRH neurons did not vary between groups; however, a shift in the distribution of GnRH neurons was observed in treated males such that more GnRH immunoreactive neurons were found in the caudal portion of their normal distribution. The shift in GnRH distribution was associated with a significant reduction (40-50%) in pituitary gonadotropin secretion. Behaviorally, treated males took significantly longer to investigate the anogenital region and then mount a receptive female. A corresponding reduction in the total number of anogenital investigations and mounts was observed. This difference between treated males and controls was reduced, but not eliminated, over successive trials and by the third trial the number of intromission was similar between treated and control males. We conclude that the full complement of adult reproductive functions observed in the male golden hamster requires thyroid hormones during the early postnatal period. The severity of the effects induced by early hypothyroidism in this species varies from transient to permanent, depending on the endpoint.

Estimate of epididymal transit time in the chimpanzee

During their passage through the epididymis, sperm undergo functional changes which result in their maturation and in their ability to fertilize ova. Maturational changes effected during epididymal transport are attributable to sequential changes in various regions of the plasmalemma of the sperm head and flagella. These functional changes in the plasmalemma result, at least in part, from the sequential binding of proteins secreted by the epididymal epithelium into the epididymal lumen. An estimate of epididymal transit time is essential to such investigations. Time elapsed from a testicular arterial infusion of a single pulse of tritiated-thymidine to the release of 3H-labeled sperm into the lumen of the seminiferous tubule was about 39 days. Seminal fluid-free 3H-labeled sperm first appear in the ejaculate about 41 +/- 1 days post-infusion. Total transit time for 3H-labeled Sd2 sperm released into the tubular lumen to appear in the ejaculate is estimated as the difference between these values. Since total transit time is equal to the seminiferous tubule transit time plus the epididymal transit time, epididymal transit time constitutes some lesser portion of the total transit time of 2 +/- 1 days.