No description available.

Nine male Physical Education students were selected to test the hypothesis that addition of CO₂ to the inspired air during recovery will cause significant increases in ventilation above control conditions and that recovery from submaximal exercise will be enhanced by the addition of 2.78% or 5.80% CO₂ to room air. The exercise was administered for six minutes at a workload predetermined to elicit 75% of his maximal oxygen uptake. The dependent variables (heart rate, ventilation, oxygen uptake, and carbon dioxide elimination) were subjected to a one way analysis of variance and significant F ratios evaluated using Dunnett's Test. Ventilation is increased significantly (p<.05) above control values with the addition of 5.80% CO₂ to room air during recovery however, there is no significant increase in oxygen uptake. The addition of 2.78% CO₂ to room air during recovery does not significantly (p>.05) increase ventilation; there is however a significant (p<.05) increase in oxygen uptake in the first 30 seconds of recovery. Neither treatment effect causes significant changes in heart rate. The addition of 5.80% CO₂ to the inspired air significantly (p<.05) reduces carbon dioxide elimination. In 4 subjects, the effect produced a carbon dioxide uptake at certain time intervals. The addition of 2.78% CO₂ to the inspired air caused a significant (p<.05) reduction of carbon dioxide elimination in the first minute of recovery. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

This research was concerned with some physiological effects of supra-normal CO₂ concentrations on cucumber, tomato and Japanese Morning Glory (Pharbitis nil), and with measurement of CO₂ levels in a commercial greenhouse. Measurements of CO₂ concentrations in a cucumber greenhouse showed that, in the early stages of crop development, early morning CO₂ levels reached 0.18% as a result of straw decomposition in the plant beds. Later in crop development, daytime levels were much lower and required gas combustion to restore high concentrations. Stomatal resistances in cucumber leaves were relatively insensitive to high greenhouse concentrations. Variation in stomatal resistance through the crop canopy was, however, detected. Generally, the two most recently developed leaves showed higher resistances than those of a slightly greater physiological age. Differences in leaf irradiance could not fully explain this effect, which may be related to the stage of leaf development. Subsequent experiments on greenhouse tomato crops showed that CO₂-enriched (0.09% CO₂) plants flowered earlier and produced 30% more fruit than those grown in normal air. Photosynthetic rates were inherently higher in apical and basal leaves developed under CO₂enrichment at irradiances above 50 m⁻²s⁻¹ .Behavioral indicies of photosynthetic efficiency indicated an enhanced capacity to utilize CO₂ in enriched plants. Measurements of CO₂ exchange in leaves of plants grown in chambers at 3 CO₂ concentrations (0.03, 0.1 and 0.5%) confirmed the enhancement of inherent photosynthetic rates in young leaves of 0.1% grown plants. Reduced rates of photorespiration, total O₂ inhibition of photosynthesis, glycolate oxidase (GaO) activity, and an increased rate of ribulose-biphosphate-carboxylase (RuBP-case) activity, contributed to this enhancement. Maximum photosynthetic rates in young leaves developed at 0.5% CO₂ were similar to those developed in 0.03% CO₂. Growth rates of the 0.1% CO₂-grown plants were higher than the similar rates of plants from the 0.03 and 0.5% regimes. Apparently maximum benefit from CO₂ enrichment is achieved by maintaining atmospheric CO₂ concentrations close to 0.1%. At a later stage of development, however, GaO and RuBP-case activities were similar in the 0.03 and 0.1% CO₂-grown plants and photosynthetic rates did not differ between growth regimes. Observations on the effects of 0.03, 0.1, 1.0 and 5.0% CO₂ on development in the Short-Day Plant Pharbitis nil revealed that 1.0 and 5.0% CO₂ modified normal flowering. These concentrations induced a weak flowering response in Long-Days and Short-Days and promoted stem elongation and leaf production under both photoperiods. These modifications were apparently unrelated to patterns of CO₂ exchange which showed a relatively small increase above 0.5% CO₂. These results are discussed in relation to possible mechanisms for the effects of supra-normal CO₂ concentrations on development. The diversity of physiological effects mediated by CO₂, and their relationship to one another are discussed. / Land and Food Systems, Faculty of / Graduate

by Edwine Wiley Odom / Typescript / M.S. Florida State College for Women 1921 / Includes bibliographical references

No description available.

No description available.

No description available.

This study was undertaken to determine and compare the rates of oxygen consumption and carbon dioxide elimination during normal and hyperventilated breathing at progressive work rates. Three subjects stepped at 18, 24, 30, 36 and 40 steps per minute on an eighteen inch bench for a duration of ten minutes or until exhaustion. All exercises were performed inside a 6,900 liter closed circuit respirometer. The volume of each subject obtained from hydrostatic weighings was subtracted from the chamber volume as was the volume of the bench. Net volume was corrected to STPD. The respirometer was equipped with Beckman oxygen and carbon dioxide analyzers, an internal cooling system as well as wet and dry thermocouples on three sides . Oxygen and carbon dioxide concentrations were continuously analyzed and automatically recorded against time. A resting metabolic rate was established prior to each work task. Completion of the exercise was followed by a fifteen minute recovery period. Curves of cumulative oxygen consumption (VO₂) and carbon dioxide elimination (VCO₂) were plotted against time. By determining the gradients of these curves at different points it was possible to plot the corresponding velocity curves [formula omitted]. The acceleration curves [formula omitted] were derived from the velocity curves. An IBM computer program was used to determine the velocity and acceleration values. When compared to normal breathing, hyperventilating at the higher work loads increases the VO₂ and VCO₂ during the early phase of exercise. This is generally followed by decreased VO₂ during the recovery period. There are well defined differences in the derivative curves between normal and hyperventilated breathing. Implications for athletic performance are indicated. Derivative curves of oxygen consumption and carbon dioxide elimination appear to be highly individual. Their use as a fitness criterion is indicated. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

This study examined the relationship between expired non-metabolic CO₂ (EX CO₂) and the accumulation of blood lactate, while emphasis was placed on the ventilatory (EX CO₂ and VE/VO₂) and lactate threshold relationship. Twenty-one elite cyclists (15 males, 6 females) performed a progressive intensity bicycle ergometer test (PIT) during which ventilatory parameters were monitored on-line at 15 second intervals, and blood lactate sampling occured on each minute. Threshold values were determined for each of the three indices; excess CO₂ (EXTT), VE/V0₂ (VVTT), and blood lactate (LATT). The three threshold values (EXTT, VVTT, LATT) all correlated significantly (P<0.001) when each was expressed as an absolute VO₂ (1/min). A significant RM ANOVA (F=8.41, P<0. 001) and post hoc correlated t-tests demonstrated significant differences between the EIXTT and LATT (P<0.001) and the EXTT and VVTT values (P<0.025). The LATT occured at an average blood lactate concentration of 3.35 mmol/1, while the mean expired excess CO₂ volume at the EXTT was 14.04 ml/kg/min. Over an 11 minute range across the threshold values (EXTT and LATT), which were used as relative points of reference, the expired EXC02 volume (ml/kg/min) and blood lactate concentration (mmol/1) correlated significantly (r=0. 69, P<0. 001). Higher individual correlations over the same period of time <r=0.82 - 0.96, P <0.001) stress the individual nature of this relationship. Expired EXCO₂ volume appeared to track blood lactate levels over this 11 minute period when the significant threshold difference (1.35 min.) was taken into consideration. These results indicate a strong relationship between the three threshold values, although changes and expired EXCO₂ precede changes in blood lactate concentration and the ventilatory equivelant (VE/VO₂). Although changes in expired EXCO₂ volume appear to track changes in blood lactate concentration, blood lactate concentration can not be accurately predicted from expired EXCO₂ volume as the nature of this relationship varies between individuals and. appears to be influenced by gender. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

Maintenance of normal health requires an intact stress system capable of mounting the metabolic, autonomic, behavioural and motor responses required for coping with or avoiding physiological and pathological challenges. The neuroendocrine component of this response principally involves the hypothalamic-pituitary-adrenal (HPA) and sympatho-adrenomedullary (SAM) axes. Impaired regulation of these axes has been implicated in the pathogenesis and expression of numerous disease states, however, it has proved very difficult to reproducibly activate the HPA and SAM axes and no single test exists that can reliably and safely be used to study these systems in man. Carbon dioxide (CO2) is the principal regulator of respiration, acid-base balance and behavioural-state arousal in humans. Paradigms of CO2 inhalation have been used in psychiatric research to investigate panic and anxiety disorders, but evaluation of other components of the stress response to CO2 has not previously been performed. I hypothesised that a single breath of 35% CO2 would be a simple and reliable tool for the evaluation of the stress response in humans. A single breath of four doses of CO2 (5%, 25%, 35% and 50%) was administered to 9 healthy volunteers in a randomised, single blind fashion. Subjective symptoms of anxiety increased in a dose-dependent manner. Inhalation of a single breath of 35% CO2 stimulated significant ACTH (p = 0.006), noradrenaline (p < 0.0001), cortisol (p = 0.02) and prolactin (p = 0.002) release. It also provoked an acute pressor response and an associated bradycardia (p < 0.0001 for both). No significant habituation of psychological, HPA or cardiovascular responses was seen when this dose was repeated after one week (n = 10) or 6 months (n = 5). It was apparent that a single breath of 35% CO2 reliably and safely produced SAM and HPA axis activation and further studies were then undertaken to assess the mechanism by which the observed responses occurred and its potential clinical implications. Administration of naltrexone (an opiate antagonist) to 10 normal volunteers disinhibited the HPA axis (p < 0.0004), whilst administration of metyrapone (a cortisol synthesis inhibitor) significantly reduced baseline cortisol (p < 0.03) levels. However, this alteration in HPA axis activity had no effect on either cardiovascular or psychological responses. Further, in a study of 8 breastfeeding mothers (a state associated with physiological suppression of the HPA axis) suckling significantly reduced plasma cortisol levels compared with control (p = 0.002) and bottle-feeders (p = 0.003). Despite this cortisol, systolic blood pressure (SBP), heart rate and psychological responses to 35% CO2 were not affected