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

Onset of puberty and regularity of oestral cycles in ewe lambs of four breeds under high-altitude conditions in a non-seasonal country

Twenty-four Colombian Creole, Romney Marsh, Hampshire and Corriedale ewes raised under high-altitude conditions in a non-seasonal country were used to determine and to characterize the onset of puberty and of regularity ovarian function since the age of 3months. They underwent blood collection for determination of progesterone and monthly weight assessment. Oestrus was assessed daily by a teaser ram. In all breeds, age at onset of puberty ranged from 5.4 to 6.9 months and age at onset of regular ovarian function ranged from 7.4 to 8.6 months. Colombian Creole showed a higher body development at onset of puberty: 73.5 ± 8.3% versus 56.2 ± 7.4 in Romney Marsh, 58.8 ± 10.4 in Hampshire, and 57.3 ± 8.0 in Corriedale (p < 0.05), as well as a higher relative daily weight gain (+17%, p < 0.05). A negative correlation between daily weight gain and age at onset of puberty was established. Progesterone at onset of puberty and of regularity did not differ between breeds, but characterization of the luteal phase by the progesterone area under the curve (P4-AUC) revealed at both time points significantly lower values for Creole lambs (p < 0.05). Decreased P4-AUC paralleled a higher proportion of short oestral cycles observed prior to onset of regularity in Creoles, whereas an increased proportion of extra-long cycles were recorded in Romney Marsh (p < 0.05). These results establish first reference data for economically important breeds raised under tropical conditions. In comparison with other breeds, Colombian Creole requires a higher body development to achieve puberty and that an important proportion of short characterizes its prepubertal period cycles.

Hypertrophy and neuron loss: structural changes in sheep SCG induced by unilateral sympathectomy

Recently, superior cervical ganglionectomy has been performed to investigate a variety of scientific topics from regulation of intraocular pressure to suppression of lingual tumour growth. Despite these recent advances in our understanding of the functional mechanisms underlying superior cervical ganglion (SCG) growth and development after surgical ablation, there still exists a need for information concerning the quantitative nature of the relationships between the removed SCG and its remaining contralateral ganglion and between the remaining SCG and its modified innervation territory. To this end, using design-based stereological methods, we have investigated the structural changes induced by unilateral ganglionectomy in sheep at three distinct timepoints (2, 7 and 12 weeks) after surgery. The effects of time, and lateral (left-right) differences, were examined by two-way analyses of variance and paired t-tests. Following removal of the left SCG, the main findings were: (i) the remaining right SCG was bigger at shorter survival times, i.e. 74% at 2 weeks, 55% at 7 weeks and no increase by 12 weeks, (ii) by 7 weeks after surgery, the right SCG contained fewer neurons (no decrease at 2 weeks, 6% fewer by 7 weeks and 17% fewer by 12 weeks) and (iii) by 7 weeks, right SCG neurons were also larger and the magnitude of this increase grew substantially with time (no rise at 2 weeks, 77% by 7 weeks and 215% by 12 weeks). Interaction effects between time and ganglionectomy-induced changes were significant for SCG volume and mean perikaryal volume. These findings show that unilateral superior cervical ganglionectomy has profound effects on the contralateral ganglion. For future investigations, it would be interesting to examine the interaction between SCGs and their innervation targets after ganglionectomy. Is the ganglionectomy-induced imbalance between the sizes of innervation territories the milieu in which morphoquantitative changes, particularly changes in perikaryal volume and neuron number, occur? Mechanistically, how would those changes arise? Are there any grounds for believing in a ganglionectomy-triggered SCG cross-innervation and neuroplasticity?