The heritability of gingival crevice depths in sheep.

The gingival crevices of the four central incisor teeth of 396 sheep with known sires were measured at the mid-labial, mid-mesial and distal (interproximal), and mid-lingual aspects to test the hypothesis that gingival crevice depths were heritable. In total, 6336 gingival crevices were examined. Mean crevicular depths were 1.50 mm (labial), 3.16 mm (interproximal) and 6.52 mm (lingual). Within breedstrain genetic variation was examined and paternal half-sib heritability estimates were found to be high for the interproximal crevice depth (0.66 +/- 0.20) and the lingual crevice depth (0.69 +/- 0.21), but lower, and non-significant, for the labial crevice depth (0.24 +/- 0.17).

Neuroendocrine regulation of growth hormone secretion in sheep. V. Growth hormone releasing factor and thyrotrophin releasing hormone.

The effects of intravenous (IV) and intracerebroventricular (ICV) administration of either bovine growth hormone releasing hormone (GRF) or thyrotrophin releasing hormone (TRH) on plasma growth hormone (GH) and glucose levels have been examined in sheep. Intravenous GRF 1-29NH2 at 3 and 30 micrograms stimulated an increase in GH levels in a dose-dependent fashion; administration of GRF into a lateral cerebral ventricle, however, produced a smaller GH response which was similar at these two doses. Evaluation of somatostatin levels in petrosal sinus blood (which collects pituitary effluent blood) showed that ICV administration of GRF stimulated a release of somatostatin into the blood. Furthermore, concurrent administration of GRF and a potent anti-somatostatin serum ICV resulted in a much enhanced release of GH which was similar to that obtained with a comparable dose of GRF given IV. TRH (as another putative GH-secretagogue) was also administered both IV and ICV. When given IV, 200 micrograms (but not 100 micrograms) TRH produced an elevation in GH levels. By contrast, when 5 micrograms TRH was given ICV there was a decrease in circulating GH levels, but no change in plasma somatostatin concentrations. These results indicate that the smaller GH response to ICV- compared with IV-administered GRF is due to the release of somatostatin within the brain. In addition, it would seem that TRH is not a physiological GH-secretagogue in sheep.

Petrosal sinus catheterization in sheep. Development of a method for sampling hormonal output from the pituitary.

A relatively nontraumatic method has been developed to catheterize the petrosal sinus (PS) of sheep, via the internal jugular vein (IJV), using a percutaneous approach monitored by fluoroscopy. Preselection of suitable animals was facilitated by injecting radiopaque material through a cannula inserted into the deep facial vein to display the venous drainage from the pituitary. Further injections, via the same cannula, were later used to assist in the maneuvering of the catheter/wire guide combination as it passed up the IJV. To confirm catheter placement, plasma samples, collected simultaneously from PS and external jugular vein (EJV), were analyzed for growth hormone (GH). GH concentrations were consistently higher in the PS samples than in those found in the EJV, and more GH pulses were seen in PS samples than in the general circulation.

Dental configuration among different breeds of sheep.

Three breeds of sheep, Southdown, Suffolk and Romney, and two mixed breeds, Border Leicester over Romney and Coopworth over Romney, managed identically on a research station, where they were free from culling and allowed to live their natural life, had their dental configuration examined. The sheep were divided into age groups with 10 sheep in each. The least variation was found in the relation of the upper dental pad to the lower jaw. The most statistically significant differences were found in the first age group: one year six months. The Suffolk breed was noticeably different from the others. Deepened gingival sulci, as well as the inconsistency of bleeding after probing associated with labial gingivitis highlighted the problems of using these latter criteria as indicators of health or disease among sheep on the basis of a single examination.

Fetal and maternal plasma electrolytes, blood gases, and pH in dairy cows during late gestation.

Sodium, potassium, and chloride were determined in fetal and maternal plasma of six cows between 208 and 269 days of gestation. Blood pH and partial pressures of oxygen and carbon dioxide also were measured in samples collected from the jugular vein of the cow and the caudal aorta and vena cava of the fetus. Concentration of chloride in fetal plasma was generally lower than the corresponding maternal value, and fetal potassium was greater than maternal. Potassium of fetal plasma increased towards term. Sodium concentrations were not significantly different between fetal and maternal plasms. Once fetal and maternal pH and blood gas tensions had stabilized after surgery, there was little change until shortly before delivery. In the last 24 h before calving maternal partial pressure of oxygen was high and fetal blood pH was low.

Fetal and maternal mineral concentrations in dairy cattle during late pregnancy.

Concentrations of ionic and total calcium, magnesium, and inorganic phosphorus in plasma were determined in bovine fetuses and their mothers within the last month before delivery. Mean fetal concentrations were higher than corresponding maternal contents during the 22 days before delivery. Ionic and total calcium in plasma fell towards term in mother and fetus. Fetal phosphorus was elevated before parturition while maternal phosphorus fell. Maternal magnesium was elevated slightly at parturition.