Ultrastructural localization of amiloride-sensitive sodium channels and Na+,K(+)-ATPase in the rat's olfactory epithelial surface

Several studies have indicated that olfactory responses are impeded by amiloride. Therefore, it was of interest to see whether, and if so which, olfactory epithelial cellular compartments have amiloride- sensitive structures. Using ultrastructural methods that involved rapid freezing, freeze-substitution and low temperature embedding of olfactory epithelia, this study shows that, in the rat, this tissue is immunoreactive to antibodies against amiloride sensitive Na(+)- channels. However, microvilli of olfactory supporting cells, as opposed to receptor cilia, contained most of the immunoreactive sites. Apices from which the microvilli sprout and receptor cell dendritic knobs had much less if any of the amiloride-antibody binding sites. Using a direct ligand-binding cytochemical method, this study also confirms earlier ones that showed that olfactory receptor cell cilia have Na+, K(+)-ATPase. It is proposed that supporting cell microvilli and the receptor cilia themselves have mechanisms, different but likely complementary, that participate in regulating the salt concentration around the receptor cell cilia. In this way, both structures help to provide the ambient mucous environment for receptor cells to function properly. This regulation of the salt concentration of an ambient fluid environment is a function that the olfactory epithelium shares with cells of transporting epithelia, such as those of kidney.      

Micropuncture study of the kidney in sheep: effects of iodoacetate on renal urea handling.

1. The effects of intrarenal infusion of iodoacetate, an inhibitor of anaerobic glycolysis, on urea transport in kidney of sheep was studied by micropuncture free-flow technique. 2. Iodoacetate decreased the tubular fluid to plasma urea ratio in late distal tubules only; no changes were found in both the late proximal and early distal tubules. Fractional delivery of urea to the same superficial segments of nephron and the urea excretion by whole kidney were not significantly influenced. 3. Our results do not support the concept of active urea transport in the kidney of sheep which would be dependent on energy derived from anaerobic metabolism.     

Commentary on Gressel's review

Transgenic Research -     

Effect of dietary energy intake on tubular reabsorption of urea in sheep

The aim of the experiment was to determine the effect of dietary energy intake on renal urea excretion in sheep with different nitrogen intakes. The control sheep, with a high nitrogen and energy intake, were given a daily feed dose of 21.18 g N and 15.2 MJ digestible energy (DE). The two experimental groups, with an equal, low nitrogen intake, were given diets with a different energy content. The high energy diet contained 3.63 g N and 14.18 MJ DE, the low energy diet 3.4 g N and 6.44 MJ DE. After nine weeks' adaptation to the diets, renal functions were measured by a standard clearance technique. It was found that, under stable urine flow conditions, both groups given the low nitrogen diet had a significantly lower glomerular filtration rate, fractional urea excretion and total urea excretion. A reciprocal comparison of these two groups showed that fractional urea excretion by the sheep with a high energy intake was significantly lower than in the group with a low energy intake. There were no differences in the glomerular filtration rate. A raised dietary energy intake in the presence of a low nitrogen intake caused marked natriuresis and kaliuresis. The results indicate that a raised dietary energy intake can be a significant factor in potentiating the renal effect of urea retention in sheep with a low nitrogen intake.     

The anti-translocation and anti-inflammatory effect of cinnamon oil in mice with TNBS induced colitis

The bacterial translocation induced by colitis may cause the organ failure and sepsis. Therefore, it is necessary to find new possibilities for prevention and therapy of this problem. The purpose of this study was to examine Escherichia coli anti-translocation activity of cinnamon oil and its ability to reduce colonic damage in mice with TNBS (2,4,6-trinitrobenzenesulfonic acid) induced colitis. Mice received cinnamon essential oil in four various concentrations (0.5%, 0.25%, 0.125% and 0.063%) in the powdery commercial rodent diet, starting 21 days before induction of TNBS colitis. The colonic damage was assessed using the colon macroscopic scoring system (Wallace score). E. coli translocation to the mesenteric lymphatic nodules was evaluated by serial dilutions method for counting bacteria. Bacterial translocation was significantly reduced in first and third group (15.2% or 42.8% in cinnamon oil groups versus 100% in TNBS group). Cinnamon oil was effective also against the colonic damage in all cinnamon oil groups (macroscopically scores of grade 9 in TNBS group versus 5.25, 5.63, 5.13 and 3.25 in cinnamon oil groups). Our results confirmed that dietary administration of cinnamon oil could possess potential therapeutic effects on bacterial translocation and intestinal wall injury in colitis.