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At least 1,279 records · Page 71Linked to original sources
PubMed2004

Osmoregulatory response to acute diet change in an avian nectarivore: rapid rehydration following water shortage.

Nectarivores may be required to switch between water conservation and water excretion as rapidly as they change food plants in nature. We examined the rehydration response in Whitebellied Sunbirds (Nectarinia talatala) that had been fed a concentrated sucrose diet (2.5 mol/l) for 2 days and then were switched to a diet 10 x less concentrated (0.25 mol/l) on the morning of the third day. We measured water gain as well as cloacal fluid (CF) volume hourly over 12 h, and analysed CF osmolality and calculated osmotic excretion. CF was also assayed for the osmoregulatory hormone aldosterone (ALDO). As in most water-deprived birds, whitebellied sunbirds cope with water shortage when fed a concentrated sugar diet by almost completely ceasing to void CF. Although osmolality of CF is high, volumes are not sufficient to maintain a steady rate of excretion and the birds retain osmolytes. Immediately upon switching to dilute diet, sunbirds produce copious volumes of CF and osmotic excretion is elevated and maintained at high levels over the first 6 h of rehydration. This stabilises by the afternoon at levels expected for hydrated birds. Some 2-3 h after peak osmotic excretion, there is a peak in the discrepancy between water intake and output, mirrored in an increase in ALDO output. These data suggest that excretion of retained osmolytes is undertaken as soon as water is available, with changes in the body fluid composition occurring subsequently. This study vindicates the use of CF to obtain repeated measurements of changes in the osmoregulatory steroid ALDO in small birds.

Aldosterone↗
PubMed1999

Measurement of peripheral tissue thickness by ultrasound during the perioperative period.

We have studied changes in peripheral tissue thickness with a novel hand-held ultrasound device during the perioperative course of 60 healthy surgical patients in three different intraoperative body positions. The nil-by-mouth period led to a significant decrease in forehead tissue thickness. Standardized infusion therapy with Ringer's solution at a rate of 8 ml kg-1 h-1 resulted in a gradual increase in tissue thickness, which was significantly different from preoperative baseline values after 90 min. Packed cell volume decreased significantly after the start of infusion and remained low over the rest of the observation time. Different body positions did not influence changes in tissue thickness. We conclude that changes in perioperative tissue thickness in healthy patients can be detected easily by ultrasound, independent of body position. This method may prove useful for the non-invasive assessment of fluid balance state.

Adult↗
PubMed1975

Effect of potassium depletion in normal males: an Apollo 15 simulation.

In the course of Apollo 15, physiologic abnormalities, manifested by ectopic activity on the ECG and unusual alterations in excerise tolerance, occurred in the crew of the Lunar Excursion Module. These were associated with decreases in total body potassium, measured by 42K, of 10% and 15%. The possibility of inadequate potassium (K plus) intake existed. A simulation study was performed prior to Apollo 16, corresponding in duration to Apollo 15. Subjects endured the same sleep aberrations and caloric expenditure as the Apollo 15 astronauts. Subjects consumed a diet containing only 15 mEq/d of K plus during the entire 12 d of absolute bedrest. ECG was continuously monitored, body fluid compartments and total body K plus were measured at intervals by radionuclide methods, electrolyte balance was determined daily, and excercise and orthostatic tolerances were determined prior to and after bedrest. In spite of decreases in total body K plus measured by 42K of 14.5% and 10.5%, and by potassium balances of 3.3% and 6.5%, respectively, neither of the two subjects developed symptomatic hypokalemia. Minor ECG abnormalities were noted in one subject. Orthostatic and exercise tolerance showed only those changes expected as a result of bedrest. Muscle strength was unaffected. Study implications and reasons for discrepancies between K plus loss measured by balance techniques and 42K are reviewed.

Adult↗