Twenty‐four hour observations on the metabolism of normal and starving subjects

Abstract

THE observations about to be described form a further part of a series of investigations into the metabolic activities over given periods. They differ from those already publishe%l in that the observation time is much longer-24 hours. Working with short periods, one of us (E. C. D. () demonstrated that there were more or less definite relations between the alveolar and blood C02 tension, gastro-intestinal secretion (2), and certain urinary constituents(3). These relations were altered by the effect of meals.The results of the previous investigations can be summarised briefly as follows:1. During a period of starvation, the alveolar C02 tension remains more or less constant, whilst the urinary pH and A + N value do not show any definite change.2. After a meal, the alveolar C02 tensions show the characteristic rise followed by a fall. The urinary changes were found to vary according to the meal. Thus the breakfast was followed by a definite alkaline tide, as shown by a rise in the pH and a fall in the A + N value. This alkaline tide was usually of short duration, and was followed by a prolonged acid tide, as shown by a fall in the urinary pH and a rise in the A + N values-both of which obscured any alkaline effect of the next meal.It was felt that these investigations were incomplete, since the observation times were never longer than 8 hours, and ouly the pH and A + N values were determined. The present investigation was undertaken, therefore, in order to clear up the difficulties of the previous observations.Variations in the composition of urine throughout 24 hours have been studied by many observers. Thus Bence Jones(4) was perhaps the first to notice the alkaline tide following a meal. Since this observer's 1 On behalf of the Medical Research Council.PH. LIX. 17

Changes in alveolar carbon dioxide tension by night and during sleep

“…The tensions plotted by Cohen & Dodds (1924) upon two fasting subjects awake for 24 hr do, however, show a regular variation, although this is not commented upon by the authors. Such a spontaneous rhythm might be responsible for some of the changes ascribed to sleep.…”

“…No claims for a spontaneous rhythm in alveolar C02 tension have been found in the literature, and the existence of such is specifically denied by Haldane & Fitzgerald (1905). The tensions plotted by Cohen & Dodds (1924) upon two fasting subjects awake for 24 hr do, however, show a regular variation, although this is not commented upon by the authors. Such a spontaneous rhythm might be responsible for some of the changes ascribed to sleep.…”

“…This had the desired effect: he sometimes even slept through the operation of the sampler, was described by the observer as being more nearly comatose than sleeping and was completely disorientated upon being awakened; next morning he had very little memory for the events of the night. Cohen & Dodds (1924) and a brief mention of Straub (1915) that tension is often high about 21.00-22.00 hr. Its most likely cause is a respiratory depression forming part of the habitual wakefulness and sleepiness rhythm (Kleitman, 1939) of which the subject is so well aware in any experiments in which he is awake for 24 hr.…”

The Influence of Cortisone Upon the Diurnal Rhythm of Renal Excretory Function

“…It has also been demonstrated repeatedly that renal excretion rates for chloride (4,(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32), sodium (4,23,24,(29)(30)(31)(32)(33), and potassium (4,23,24,(29)(30)(31)(32)(33) are consistently much lower by night than by day, even when no food or electrolyte is taken or when the dietary intake is equally distributed over each 24-hour period. The output of urea characteristically declines at night (10,12,14,17,18,28,(33)(34)(35), but Smits (29) and Borst and de Vries (30) relate this decrease in excretion, unlike that of other solutes, to nocturnal diminution of urine flow; they find that the nocturnal excretion rate, "corrected" according to the Van Slyke formula for standard urea clearance, approximates the rate by day. Uric acid excretion also falls during the night (8, 36, 37).…”

Postprandial Alkaline Tide: Does It Exist?

“…The variations may be due to the uncomfortable test conditions, with mouth piece, noseclip and laboratory environment or to minor changes in physiological arousal which affected respirato ry function. We believe that such changes may account for early observations of a respiratory alkaline tide, which were based on single observations in a very small number of subjects [20,21].…”