The origin of the immunoglobulins in intestinal lymph of sheep.

Various immunoglobulins were labelled with radioactive iodine and their distribution between intestinal lymph and plasma followed in order to determine the origin of the immunoglobulins found in intestinal lymph. By comparing specific activities in plasma and lymph, it was computed that 25 percent of the IgG1 and IgG2 and 90 percent of the IgA in intestinal lymph were locally synthesised. The results suggest that virtually all of the IgA and a proportion of the IgG1 computed to be synthesised locally were derived from plasma cells of corresponding specificity in the lamina propria of the intestine.     

Influence of ruminal and plasma osmotic pressure on salivary secretion in sheep

The osmotic pressure of the rumen contents and also of the blood was altered by intraruminal administration of water or hypertonic solutions. It was found that alterations in osmotic pressure were accompanied by inverse changes in the flow rate of mixed saliva. Intravenous infusion of hypertonic solutions, causing elevation of the osmotic pressure of the blood without affecting that of the rumen, also caused a reduction of salivary secretion rate. The flow rates of both parotid and residual saliva were affected. When strongly hypertonic solutions of sodium or potassium salts were infused into the rumen, or sodium salts or urea were infused into the blood, the concentration of those substances increased in the saliva. Other treatments had little effect on salivary composition.     

The effects of intravenous phosphate loading on salivary phosphate secretion and plasma parathyroid hormone levels in the sheep.

Adult sheep were given intravenous infusions of a solution of Na2HPO4 and the effects on parotid salivary composition and on plasma parathyroid hormone levels were studied. Infusion of the phosphate solution resulted in increases in the concentration of inorganic phosphate in the plasma and to proportional increases in the concentration and amount of phosphate secreted in the saliva. There was, however, no evidence that the salivary response was dependent upon a change in endogenous parathyroid hormone release. In other studies infusion of bovine parathyroid hormone or stimulation of endogenous hormone release through infusion of EDTA both led to a fall in the concentration of inorganic phosphate in the plasma and to a fall in the concentration and amount of phosphate secreted in the saliva. Taken together these results suggest that the major factor affecting salivary phosphate secretion in these studies was the concentration of inorganic phosphate in the plasma. Parathyroid hormone does not appear to have any direct effect on salivary phosphate secretion in the sheep though it may indirectly influence phosphate secretion through its effects on plasma inorganic phosphate level.     

The role of the autonomic nervous system in the depression of parotid salivary secretion during hyperkalaemia in conscious sheep.

The rate of flow and electrolyte concentration of parotid saliva were measured before, during and after intravenous and contralateral intracarotid infusion of KCl (0.5 mol.1(-1)) and NaCl (0.5 mol.1(-1)) at 385-625 mumol. min(-1) for 40 min into 5 sheep. In intact conscious sheep contralateral intracarotid infusion of KCl caused marked depression of salivary secretion in all experiments whereas infusion of NaCl had no consistent effect on flow. Intravenous infusion of KCl into the intact conscious sheep caused a slight depression of salivary secretion but minimum flow was significantly higher than that during intracarotid infusion. When the sheep were anaesthetized salivary flow rates were low and contralateral intracarotid infusion of KCl either had no effect on flow or caused an increase in flow. After ipsilateral cervical sympathectomy contralateral intracarotid infusion of KCl into the conscious sheep caused a marked depression of salivary flow similar to that occurring when the sheep were intact. After section of the secretomotor nerve of the gland salivary flow rates were low and contralateral intracarotid infusion of KC1 had no effect on flow. The salivary flow responses of the sheep were consistent, regardless of whether the KCl infusions were given within 24 h or 1-2 weeks after cervical sympathectomy or secretomotor nerve section. Salivary sodium concentration was negatively correlated with salivary flow in all experiments. It was concluded that potassium acted at a site located in the head but by direct action on the salivary gland. The depression of salivary secretion by hyperkalaemia resulted from a decline in neural activity in the parasympathetic secretomotor innervation of the parotid gland.     

The salivary secretion of spinning larvae ofRhynchosciara americana

Summary The secretion present at the lumen of the salivary glands of spinning larvae ofRhynchosciara americana was studied cytochemically and with microspectrophotometry and fluorescence and quantitative polarization microscopy. It was found that structural proteins, including glycoproteins and lipoproteins, occur in this secretion. Findings involving spectral absorption profiles after xylidine ponceau staining, patterns of birefringence and dispersion of birefringence, and lack of dichroism after xylidine ponceau staining and of blue fluorescence after ANS staining are highly suggestive that the secretion ofR. americana differs from classical silks not only in terms of composition but also of macromolecular array. The silk secretion ofR. americana also appears to differ from that of another sciarid,Bradysia spatitergum. Part of the glycoproteins present at the glandular lumen is assumed to be extruded from cells of the posterior zone of the glands, whereas other glycoproteins (or their glycidic radicals) are probably removed from fat body cells via cells of the anterior zone of the glands. The salivary secretion of the spinning larvae ofR. americana contains calcium and is devoid of acid glycosaminoglycans.