During three summers field studies were made of Merino wethers deprived of water while exposed to sun and to maximum air temperatures ranging from 84°F (29°C) to 10S°F (42°C) at Julia Creek, lat. 21° S. Evaporative cooling determined the rate and extent of water and electrolyte changes and produced a different pattern each year. Control of body temperature failed when 31% of body weight was lost by the end of 10 days without water. In hotter weather 5 days without water caused a 25% loss of body weight and in some sheep irreversible circulatory failure. In the course of dehydration, after an initial increase, the plasma and extracellular volume decreased up to 45% while concentrations of haemoglobin and plasma protein increased by 60%. In the plasma, potassium and sodium concentration increased less than that of haemoglobin. When 25% or more of weight was lost, plasma urea concentration rose to 136 mg/100 ml. Plasma osmolarity in some sheep reached 490 m-osmoles/l after 10 days. Urine volume fell after 2 days without water, and in a hot season less than 100 ml/24 hr was passed on the fourth or subsequent days. Concentrations increased over the first 4 or 5 days, reaching a maximum of 3.8 osmoles/l, then declined. Between half and two-thirds of the osmolarity was accountable to sodium and potassium salts. In rapid dehydration, more sodium was excreted than potassium. There was reduced sodium excretion when water was ingested after dehydration. Renal function studies in ewes indicated that filtration, renal plasma flow, and glucose reabsorption were reduced to half after 5 days without water in the heat. The chance of survival in dehydration appears to be increased by low rates of water loss in the first 3 days, together with high sodium and low potassium excretion. A full rumen, containing water up to 13% of body weight, could provide all the extracellular fluid loss. More than half of the weight loss appears, however, to come from intracellular sources. Extracellular fluid was drawn upon to a greater extent when the rate of dehydration was rapid, than in the cooler periods of slow weight loss. Survival in the sun without water depends upon insulation, water conservation, water reserves in rumen and extracellular fluid, the ability to adjust electrolyte concentrations, and the ability to maintain circulation with lowered plasma volume.

No abstract

One group of rats was reared under conditions of environmental complexity, while their littermates served as isolation controls. The occipital cortex was 4.9% (p < 0.01) and the hippocampus 5.7% (P < 0.05) thicker in the environmental complexity rats than in the isolation control animals. Differntial cell counts demonstrated significant differences in neuroglia in the hippocampus.

Urinary and faecal phosphorus excretion were measured in five sheep for 4 days after acute intravenous infusion of 3.38 g of phosphorus as potassium dihydrogen phosphate. Urinary phosphorus excretion was increased for 12 hr after the infusion, but urinary phosphorus output was small compared with the marked increase in faecal phosphorus output. The increase in faecal phosphorus excretion coincided with and followed the appearance in the faeces of Cr-EDTA, which had been introduced into the rumen as a marker at the time of the phosphate infusion. This suggests that secretion of phosphorus into gut regions below the reticulo-rumen is not quantitatively altered in response to intravenous phosphorus loading, and that phosphorus absorption is also unaffected (at least not on a short-term basis). The additional phosphorus entered the alimentary canal at the level of the reticulo-rumen, and it was deduced that this occurred predominantly via the salivary glands. Persistence of the increase in faecal phosphorus excretion for some time after the Cr-EDTA marker had been cleared emphasizes the importance of the phosphorus recirculation system to ruminants like the sheep.

Following an intravenous loading injection of 75 U.S.P. Units of Para-Thor-Mone (Eli Lilly and Co.), seven conscious, non-pregnant, non-lactating Merino ewes were infused with a maintenance dose of the hormone at a rate of 4'75 U.S.P. units/min for 2 hr. The classical hypercalcaemia and hypophosphataemia of the non-ruminant was observed, but the hypercalcaemia was only small. Plasma potassium concentration decreased, while there were no changes in plasma sodium, chloride or magnesium. The classical phosphaturic effect of the hormone was not observed, only trace amounts of phosphate being excreted throughout the experiment. Urinary excretion of calcium and magnesium decreased, urine flow and urinary excretion of sodium, potassium, chloride, bicarbonate and urine pH increased. Glomerular filtration rate was unaffected, but renal plasma flow increased. The concentration and secretion rate of salivary phosphate increased markedly. Changes in the other important salivary electrolytes (sodium, potassium, chloride, bicarbonate and hydrogen ion) also occurred, but it was difficult to separate primary from secondary effects of the hormnone. Saliva flow rate increased transiently following hormone injection, but the effect was not sustained by the maintenance infusion.Although the kidney is the major site of phosphorus regulation in nonruminants [Pitts and Alexander, 1944], the salivary glands appear to be of paramount importance in sheep [Compere, 1966; Clark, Budtz-Olsen, Cross, Bauert and Finnamore, 1973;Tomas and Somers, 1974] and probably all ruminants under normal dietary conditions. It therefore becomes desirable to establish the effects of parathyroid hormone in this species, and particularly to clarify any interaction of the hormone with the salivary glands.The information presently available on the effects of parathyroid hormone in sheep is incomplete and inconsistent. In the experiments of Lotz, Talmage and Comar [1954] and Alexander and Nixon [1969] on adult sheep, the classical pronounced phosphaturia of the non-ruminant was virtually absent. In contrast foetal sheep exhibit a pronounced phosphaturia when infused with the hormone [Alexander and Nixon, 1969;Smith, Tinglof, Meuli and Borden, 1969], and Barlet and Care [1972] observed it to cause a significant increase in urinary phosphate excretion in two months old lambs fed a diet of hay and concentrates. A possible effect of the hormone on the salivary glands of ruminants does not appear to have been examined.The object of the present work was to determine the acute effects of intravenous infusion of parathyroid hormone on various urinary, plasma and salivary parameters in normal adult sheep.