Plasma levels and renal handling of endogenous amino acids in snakes: a comparative study.

Plasma levels of 22 endogenous amino acids were measured by ion-exchange chromatography in four species of snakes: Thamnophis sirtalis, T. radix, Aipysurus laevis, and Python molurus. Despite considerable interspecific variation in the amino acid composition, all species showed relatively high plasma concentrations of histidine, a feature apparently unique to reptiles. The renal handling of these amino acids was studied by renal clearance methods. As in other vertebrates, net tubular absorption of filtered amino acids predominated. However, net tubular secretion of taurine, cysteic acid and/or phosphoserine and beta-alanine was observed, with taurine being the predominant amino acid secreted. The percentage reabsorption of the total amino acids filtered by the snake kidneys ranged from 79 to 95%. Evidence for the postrenal absorption of amino acids in these reptiles is presented. In species that normally undergo hibernation (Thamnophis spp.), the ability of the kidney to reabsorb amino acids was depressed by cold acclimation. Cold acclimation significantly decreased plasma levels of all amino acids except taurine, whose concentration increased. The increase in plasma taurine level may have resulted from cellular osmoregulation. Under these conditions, renal excretion of taurine increased concomitantly with the increase in plasma taurine concentration.

The cloaca of Myxine glutinosa (Cyclostomata): a scanning electron microscopical and histochemical investigation.

The cloaca of Myxine glutinosa was examined by histochemical and scanning electron microscopical methods. No copulation organ could be found in Myxine and no detectable differences in the anatomy of the cloaca between male and female Myxine glutinosa. The anal gland which is the only gland in the cloacal region is situated between rectum and ductus coelomaticus. Like the lateral mucous glands in the epidermis it consists of large mucous gland cells, thread cells and undifferentiated cells. The cloacal epithelium neither develops a spatial separation by folds nor a ciliation is present in the caudal and dorsal part of the cloacal chamber. Therefore female and male myxinoides do not show any structures which would allow transportation of sperm into the abdominal cavity or out of it.

[Light and electron microscopic and histochemical studies on the cloaca epithelium of the domestic hen]. / Lichtmikroskopische, elektronenmikroskopische und histochemische Untersuchungen am Kloakenepithel des Haushuhns

The mucous membrane of the Cloaca was investigated light and electronmicroscopically in 20 hens. Some histochemical investigations and a reabsorption test were carried out. The surface of the Coprodaeum is being formed by villi and deep crypts. The former disappears gradually within the Urodaeum. The latter crypts can be found down to the Proctodaeum. The epithelium of the Coprodaeum and Urodaeum consists of goblet cells and highprismatic cells containing secretory granules. The Proctodaeum can be subdivided into three parts. A cranial, containing the same epithelium as the Coprodaeum, a middle with a two layered highprismatic epithelium and a caudal part with a multilayered squamours epithelium. The columnar cells of all parts of the cloaca show a strong reaction to acid phosphatase and ATPase, whereas alkaline phosphatase is almost negative.

Galactose toxicity in the chick: hyperosmolality.

Galactose-fed chicks have been found to develop severe hyperosmolar dehydration. Although biochemical abnormalities have been observed in the brain of the galactose-toxic chick, the observed physiologic alteration of serum osmolality could be the major factor responsible for the galactose toxicity syndrome in the chick.