An Endogenous Circadian Rhythm in the Rate of Carbon Dioxide Output ofBryophyllum

1973 ◽  
Vol 24 (2) ◽  
pp. 488-496 ◽  
Author(s):  
MALCOLM B. WILKINS
Keyword(s):  
Carbon Dioxide ◽  
Circadian Rhythm ◽  
Carbon Dioxide Output ◽  
Endogenous Circadian Rhythm

Global carbon dioxide output of volcanic lakes in the Azores archipelago, Portugal

2021 ◽  
pp. 106835
Author(s):  
César Andrade ◽  
Fátima Viveiros ◽  
J. Virgílio Cruz ◽  
Rui Coutinho
Keyword(s):  
Carbon Dioxide ◽  
Azores Archipelago ◽  
Carbon Dioxide Output ◽  
Volcanic Lakes ◽  
Global Carbon

Breathing in brief exercise

1960 ◽  
Vol 15 (4) ◽  
pp. 583-588 ◽  
Author(s):  
F. N. Craig ◽  
E. G. Cummings
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Respiratory Exchange Ratio ◽  
Metabolic Cost ◽  
Carbon Dioxide Tension ◽  
Minute Volume ◽  
Carbon Dioxide Output ◽  
Respiratory Minute Volume ◽  
Before And After

Two men ran for 20 or 60 seconds while inhaling air, oxygen or 4% carbon dioxide. Inspired respiratory minute volume was determined for each breath. Ventilation increased suddenly in the first breath with minimal changes in end-expiratory carbon dioxide tension and respiratory exchange ratio to a rate that remained constant for 20 seconds before increasing further. The rate of carbon dioxide output was uniform during the first 20 seconds. A 12% grade did not increase ventilation or oxygen uptake during runs of 20 seconds, but in the first minute of recovery, ventilation was 64% greater than after level runs. Inhalation of oxygen inhibited ventilation by 24% in the 20-second periods before and after the end of a 60-second run. Inhalation of carbon dioxide begun at rest produced increments in ventilation and end-expiratory carbon dioxide tension that varied little during running and recovery. In the 20-second runs ventilation varied with speed but appeared independent of ultimate metabolic cost. Submitted on January 21, 1960

Use of respiratory quotients in assessment of aerobic work capacity

1962 ◽  
Vol 17 (1) ◽  
pp. 47-50 ◽  
Author(s):  
B. Issekutz ◽  
N. C. Birkhead ◽  
K. Rodahl
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Work Load ◽  
Work Capacity ◽  
Bicycle Ergometer ◽  
Carbon Dioxide Output ◽  
Ergometer Test ◽  
Aerobic Work Capacity ◽  
Bicycle Ergometer Test ◽  
Better Than

Oxygen uptake and carbon dioxide output were measured in 32 untrained subjects during exercise on the bicycle ergometer. It was shown that the work respiratory quotient (RQ) under standardized conditions can be used as a measure of physical fitness. ΔRQ (work RQ minus 0.75) increases logarithmically with the work load and maximal O2 uptake is reached at a ΔRQ value of 0.40. This observation offered the possibility of predicting the maximal O2 uptake of a person, based on the measurement of RQ during a single bicycle ergometer test at a submaximal load. For each work RQ between 0.95 and 1.15 a factor was presented, together with the aid of a simple equation, which gave a good approximation (generally better than ±10%) of the maximal O2 uptake.

Respiratory compensation point

2021 ◽  
pp. 93-96
Author(s):  
William J.M. Kinnear ◽  
James H. Hull
Keyword(s):  
Carbon Dioxide ◽  
Minute Ventilation ◽  
Cardiopulmonary Exercise Test ◽  
Compensation Point ◽  
Respiratory Compensation Point ◽  
Carbon Dioxide Output ◽  
Respiratory Compensation ◽  
Cardiopulmonary Exercise ◽  
The Subject ◽  
Maximal Effort

This chapter describes how acidaemia stimulates ventilation in the later stages of a cardiopulmonary exercise test (CPET). This happens after the anaerobic threshold, once the capacity of the blood to buffer lactic acid has been used up. The respiratory compensation point (RCP) can be identified from an increase in the slope when minute ventilation (VE) is plotted against carbon dioxide output (VCO2), or from a rise in the ventilatory equivalents for carbon dioxide (VeqCO2). The presence of a clear RCP indicates that the subject has made a fairly maximal effort during the CPET. An RCP also argues against significant lung disease, since it implies the ability to increase ventilation in response to acidaemia.

Circadian rhythm and response to light of extracellular glutamate and aspartate in rat suprachiasmatic nucleus

1996 ◽  
Vol 271 (3) ◽  
pp. R579-R585 ◽  
Author(s):  
S. Honma ◽  
Y. Katsuno ◽  
K. Shinohara ◽  
H. Abe ◽  
K. Honma
Keyword(s):  
Circadian Rhythm ◽  
Suprachiasmatic Nucleus ◽  
Light Pulse ◽  
Continuous Light ◽  
In Vivo Microdialysis ◽  
Dark Phase ◽  
Dark Cycle ◽  
Complete Darkness ◽  
Endogenous Circadian Rhythm

Extracellular concentrations of glutamate and aspartate were measured in the vicinity of rat suprachiasmatic nucleus (SCN) by means of in vivo microdialysis. The concentrations of both excitatory amino acids (EAAs) were higher during the dark phase than during the light under the light-dark cycle, showing pulsatile fluctuations throughout the day. When rats were released into the complete darkness, the 24-h pattern in the aspartate continued for at least one cycle, whereas that in the glutamate disappeared. The nocturnal increases in the EAA levels were not due to the increase of locomotor activity during the nighttime, because the 24-h rhythms were also detected in animals under urethan anesthesia. The patterns of extracellular EAA levels were changed when rats were released into the continuous light. Circadian rhythm was not detected in the glutamate, whereas the 24-h pattern was maintained in the aspartate with the levels increased to various extents. A 30-min light pulse given either at zeitgber time (ZT) 1 or ZT 13 elevated the EAA levels during the latter half of the light pulse, except glutamate by a pulse at ZT 1. The extracellular EAA levels in the vicinity of the rat SCN showed the circadian rhythm with a nocturnal peak and increased in response to the continuous light and a brief light pulse. The aspartate level is considered to be regulated by the endogenous circadian rhythm, but the glutamate levels seems to be modified by the light-dark cycle.

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