The intrapituitary endocrine events during maturation and timing of puberty in the female sheep

Gonadotrophin-releasing hormone and GnRH-associated peptide neurobiology from the rearing period until puberty in the female sheep

“…Lambs were left to graze with dams in a pasture for 12 weeks after parturition. Twelve-week-old ovary-intact lambs (average weight 18.3 AE 1.2 kg) were divided randomly into seven developmental groups according to different phases of postnatal ontogeny: infantile, prepubertal, peripubertal and pubertal periods, determined previously on the basis of intrahypophyseal regulation of both the luteinizing hormone (LH) and follicle-stimulating hormone (FSH) posttranscriptional processing (Wań kowska and Wań kowska et al, 2008a). The infantile period was represented by 12-week-old (the last week of September) weanlings which grazed with their flock in a pasture and suckled their mothers approximately twice per 24 h. The prepubertal period was represented by both 15-week-old weaned lambs (2 weeks after weaning, n = 4) and 22-week-old lambs (the last week of November, n = 4).…”

“…There are clear species differences in the distribution of these neurons (King and Anthony, 1984). In sheep, the pre-and postnatal development of the GnRH system has been described until 16 weeks of age (Polkowska, 1986;Polkowska et al, 1987;Caldani et al, 1995) to the inauguration of prepuberty, determined on the basis of intrahypophyseal regulation of both gonadotrophins' posttranscriptional processing (Wań kowska and Wań kowska et al, 2008a). Starting from the middle of fetal life, 1500-2000 perikarya of GnRH neurons are found ventrally as a loose continuum from the septum to the mammillary bodies (Polkowska, 1986;Polkowska et al, 1987;Wood et al, 1992;Caldani et al, 1995).…”

The impact of the mother on the hypothalamic-pituit aryadrenal, hypothalamic-pituit ary-gonadal and somatotropic axes activity of offspring during postnatal ontogeny

“…Pivotal elements influencing the HPG axis activity are gonadal hormones as an internal environmental factor (Jansen 1982;Veldhuis et al 2006;Wańkowska et al 2008a;Wańkowska et al 2010a;Wańkowska et al 2010b) and keeping and later mother-infant ties interruption as an external environmental factor .…”

“…Neonatal and infantile stages are parts of the rearing period. This schema pertain to species with relatively long ontogeny (Ebling 2005;Wańkowska et al 2008a;Wańkowska et al 2008b;Wańkowska et al 2010a;Wańkowska et al 2010b).…”

“…In the early stages of mammalian ontogeny the dominating processes are the growth connected with increasing number of cells and differentiation involving the qualitative changes of individual types of cells. Close coordination of these processes determines the normal postnatal development of offspring and leads to puberty (Ojeda, Jameson 1977;Jansen 1982;Wańkowska et al 2008a;Wańkows-ka et al 2008b;Wańkowska et al 2010a;Wańkowska et al 2010b;Wańkowska 2012;Wańkowska et al 2012). Birth, weaning and puberty are pivotal events in the mammalian postnatal ontogeny.…”