Morphological characterisation of the coronary arteries in African sheep (Ovis orientalis). Differential analysis with those of humans and other animal species.

BACKGROUND: Despite the importance of the coronary system in the African sheep as a possible experimental model, there is little information about this particular vascular system. The objective of this investigation was to characterise morpho- logically the coronary arteries and their branches in African sheep. MATERIALS AND METHODS: This descriptive cross-sectional study evaluated the coronary arteries and their branches of 62 hearts of short hair sheep. The right and left coronary ostia were perfused with a semi-synthetic resin (Palatal GP40L 85%; styrene 15%) dyed with mineral red. The morphological characteristics were evaluated using a digital calibrator and the biometrics of the coronary arteries and their branches were registered. RESULTS: The right coronary artery had a proximal calibre of 2.11 ± 0.46 mm. The subsinusal interventricular branch ended at the middle third of the homonym sulcus in 19 (30.6%) specimens. The left coronary artery had a diameter of 5.38 ± ± 1.59 mm and a length of 4.67 ± 3.32 mm. This artery bifurcated itself in the paraconal interventricular branch and the left circumflex branch in 57 (91.9%) hearts and trifurcated with an additional left diagonal branch in 5 (8.1%) spec- imens. Left coronary artery dominance was observed in 51 (82.3%) specimens, whereas in 11 (17.7%) cases the coronary circulation dominance was balanced. CONCLUSIONS: Due to the similitude in the features of the coronary arteries between African sheep and humans, this animal model can be proposed for procedural and haemodynamic activities.

X-Y translocations and sex differentiation.

Translocations involving the X and Y chromosomes are often associated with anomalies of gonadal development. Transfer of Yp sequences, including the testis-determining SRY gene, to the terminal portion of the short arm of the X chromosome is associated with 46,XX maleness and in rare cases 46,XX true hermaphroditism. Three classes of XX males have been defined on the basis of the extent of Y material transferred to the X chromosome. In one class, the transfer of material involves aberrant recombination between two highly homologous genes, PKRX and PKRY, and there is evidence to suggest that this interchange is influenced by the Y chromosome background. Other types of X-Y translocations associated with anomalies of sex differentiation include Xp-Yq translocations, which result in a functional disomy of Xp sequences including the DSS locus and are associated with 46,XY complete or partial gonadal dysgenesis. In rare cases Yp-Xq translocations have been described in association with 46,XX maleness.