Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Standard clearance studies were performed in mechanically ventilated intact and acutely thyroparathyroidectomized (TPTX) rats to document and characterize the effect of hypercapnia (HC) on urinary phosphorus excretion (U(P)V). HC as compared to normocapnia (NC) was associated with an increase in U(P)V in intact (62.5 vs. 7.93 mug/min) and TPTX (30.5 vs. 0.59 mug/min) rats, an increase in filtered load of phosphorus in intact (218 vs. 191 mug/min) and TPTX (243 vs. 146 mug/min) rats, an increase in blood bicarbonate concentration in intact (27.8 vs. 26.0 meq/liter) and TPTX (24.5 vs. 22.3 meq/liter) animals, and a decrease in blood pH in intact (7.15 vs. 7.42) and TPTX (7.07 vs. 7.39) rats. Additional TPTX rats with NC and HC were studied during phosphorus infusion at a comparable filtered load of phosphorus (NC = 307 mug/min and HC = 328 mug/min). U(P)V was 18.5 mug/min in NC and 85.2 mug/min in HC animals. Intact NC animals infused with NaHCO(3) achieved a blood bicarbonate of 45.9 meq/liter compared to 26.0 meq/liter in intact NC NaCl-infused rats. U(P)V was 10.0 mug/min in the NaHCO(3) and 7.93 mug/min in NaCl-infused animals. In intact HC animals infused with NaHCO(3), blood pH was 7.36 compared to 7.42 in NC intact NaCl-infused animals. U(P)V was 83.2 mug/min in the HC bicarbonate-infused and 7.93 mug/min in the NC NaCl-infused rats. These experiments demonstrate that elevated blood carbon dioxide tension per se increases U(P)V. Increases in filtered load of phosphorus and blood bicarbonate which are associated with HC contribute to the phosphaturia as does parathyroid hormone. The phosphaturia is not dependent upon reduction of extracellular pH.
 ...
PMID:Relationship between phosphaluria and acute hypercapnia in the rat. 1 98

Fourteen young men (on the average 25 years), well trained (maximal oxygen consumption, VO2 max., between 2.7 to 3.5 1) have been studied at two different levels of exercise: 90 and 140 watts (about 40 and 70% of VO2 max.) in chamber, where the atmosphere was regulated. The subjects performed the exercise after a sojourn of six hours in the chamber, at the same level, either in air or in hypercapnic conditions (FICO2: 0.04; FIO2: 0.21); the order of the exercise tests was determined at random. The rise of total ventilation (VE) during exercise in CO2 atmosphere was particularly related to the increased tidal volume (VT). In spite of the larger increase of VE in hypercapnia, CO2 output (VCO2) and respiratory quotient (R) were lower while PaCO2 was elevated (48 at rest and 54 mmHg during exercise). Oxygen consumption during exercise was the same in both conditions. Values of arterial lactic acid concentration were not different at 90 watts level. On the contrary, at the level of 140 watts, the lactic acid concentration was significantly lower in CO2 atmosphere. The well known changes during exercise of other electrolytes (rise of Na+, K+ and total Ca) was similar in air and in CO2. Only the inorganic phosphorus was higher in CO2 atmosphere at 140 watts.
 ...
PMID:[Metabolism during exercise in young men breathing 4% CO2 (author's transl)]. 101 74

Endurance muscle performance is highly dependent on ATP production from mitochondrial oxidative phosphorylation. To study the role of the mitochondrial oxidative enzymes in muscle fatigue, we analyzed the relationship between the concentrations of substrates associated with ATP synthesis and the muscle performance of electrically stimulated rabbit muscle under CO2-induced acidosis. Two different conditions of pacing-induced muscle performance were produced in the gastrocnemius and soleus muscle groups in anesthetized rabbits by stimulating the sciatic nerve submaximally at two frequencies. Phosphorus nuclear magnetic resonance was used to measure ATP, phosphocreatine, and Pi and to provide data for a calculation of intracellular pH and free ADP. To induce acidosis, the animal was ventilated with 20% CO2. The administration of CO2 effectively reduced the intracellular pH from 6.9 to 6.7 and reduced the isometric tension-time integral (TTI) to below half the value measured in normocapnia at the low pacing frequency. A twofold increase in the pacing frequency resulted in a doubling of the TTI in normocapnia and a tripling of TTI in hypercapnia. The increases in TTI corresponded with increases in free ADP and Pi concentrations. Under the various conditions, all free ADP values were near the in vitro Michaelis-Menten constant (Km) of ADP. The Michaelis-Menten relationship of the oxidative phosphorylative enzymes was applied to the change in substrate concentrations with respect to TTI. From this relationship we observed that the in vivo Km of free ADP was 26 microM, which is close to the in nitro Km, and that Km and maximal reaction velocity did not change under hypercapnia and increased pacing frequency.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Substrate regulation of mitochondrial oxidative phosphorylation in hypercapnic rabbit muscle. 155 27

This report demonstrates the feasibility of using deuterium (2H) and phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy to make multiple simultaneous determinations of changes in cerebral blood flow, brain intracellular pH, and phosphorylated metabolites for individual animals. In vivo spectra were obtained from the brains of newborn piglets immediately following an intracarotid bolus injection of deuterium oxide. Experiments were performed at magnetic field strengths of 1.9 T (2H NMR only) or 4.7 T (interleaved 2H and 31P NMR). The rate of clearance of deuterium signal was used to calculate cerebral perfusion rates (CBFdeuterium) during a stable control physiologic state and conditions known to alter blood flow. CBFdeuterium values measured at 1.9 T under conditions of control (normocarbia, normotension), hypercarbia, hypocarbia, and varying degrees of ischemia induced by hypotension showed a significant positive correlation with values measured simultaneously using radiolabeled microspheres (CBFdeuterium = 0.4 x CBFmicrospheres + 8; r = 0.8). Simultaneous interleaved 2H and 31P NMR measurements under control conditions indicate that brain energy metabolites and intracellular pH remained at constant levels during the time course of the administration and clearance of deuterium oxide. Also, brain phosphorylated metabolites and intracellular pH did not differ significantly from their preinjection levels. Under control physiologic conditions, CBFdeuterium varied by +/- 6% and phosphorylated metabolite levels did not show a significant change with time, as measured from 15 blood flow determinations collected over 4 h. The results indicate that CBFdeuterium determinations have excellent reproducibility and do not affect brain energy metabolite levels. The procedures described here have the potential to bring a novel methodology to bear on investigating the relationship between cerebral perfusion and energy status during conditions such as ischemia or asphyxia.
 ...
PMID:Simultaneous measurement of cerebral blood flow and energy metabolites in piglets using deuterium and phosphorus nuclear magnetic resonance. 198 5

In order to study the effect of the decrease in P-Pi caused by low pH on hemoglobin-oxygen affinity, we measured P-Pi,2,3-diphosphoglycerate (2,3-DPG), and oxygen tension at 50% saturation (P50) in 36 cases with acute exacerbation of chronic respiratory failure with hypercapnia. The cases were classified into two groups by arterial blood pH values obtained on the day of admission. Group A: pH less than or equal to 7.35 and Group B: pH greater than or equal to 7.36. P50 was calculated by a modification of Severinghaus' equation developed by Yusa and Kohsaka, and it was corrected by applying the carboxy-hemoglobin (COHb) coefficient. On the day of admission (stage I), 2,3-DPG and P50 in both groups were slightly higher than in the control group. In Group A, a week after admission (stage II), these values decreased and became significantly lower than they had been at stage I. Especially 2,3-DPG in stage II was even lower than those of the control group. Approximately 14 days after admission, in stage III, it was found that these values had risen to the initial level at stage I. In Group A, similar changes were also observed for P-Pi. The value of P-Pi was low in stage II and recovered to the initial value in stage III. On the other hand, we found that the urinary excretion of phosphorus (U-Pi) increased at stage I in Group A. It was supposed that the increase in U-Pi at stage I caused a decrease in P-Pi, which caused the decrease in 2,3-DPG, in stage II.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:[Hemoglobin-oxygen affinity in acute exacerbation of chronic respiratory failure]. 207

During acute respiratory acidosis, cardiac contractile pressure first drops but then recovers substantially. We investigated the mechanism of this response in isovolumic perfused ferret hearts. Developed pressure (DP) and its first derivative (dP/dt) were measured before, during, and after hypercapnia induced by equilibrating the perfusate with 15% CO2, rather than the 5% CO2 used in control. Intramyocardial pH (pHi) was measured by phosphorus nuclear magnetic resonance (NMR) spectroscopy. After the onset of hypercapnia (1-2 min), DP and +dP/dt reached minimal mean values of 37 +/- 2 and 39 +/- 3% of control, respectively. This early decline in myocardial contactility was followed by a partial recovery such that DP and +dP/dt had returned to 66 +/- 6 and 62 +/- 4% of control, respectively, by 14 min of hypercapnia. pHi fell from 7.17 +/- 0.01 in control to 6.88 +/- 0.11 after approximately 2 min of hypercapnia. Thereafter, pHi recovered linearly with a mean slope of 0.011 +/- 0.003 pH U/min. Ethylisopropylamiloride (10(-6) M), a blocker of Na(+)-H+ exchange, prevented the recovery of pHi during hypercapnia and attenuated the recovery of contractility by 40%. We conclude that the recovery of contractility during respiratory acidosis at least partially reflects an underlying recovery of pHi mediated by Na(+)-H+ exchange.
 ...
PMID:Recovery of contractility and pHi during respiratory acidosis in ferret hearts: role of Na(+)-H+ exchange. 216 81

The energy metabolism and the brain intracellular pH regulation under arterial CO2 tensions of 25-90 mm Hg were investigated in unanesthetized spontaneously breathing rats by in vivo phosphorus nuclear magnetic resonance spectroscopy (31P NMR). The 31P brain spectra, recorded with a high resolution spectrometer (AM 400 Brucker), allowed repeated non-invasive measurements of cerebral pH (pHi), phosphocreatine (PCr), inorganic phosphate (Pi) and adenosine triphosphate (ATP) levels in 15 rats breathing a gas mixture containing 21% O2, N2, and a varied percentage of CO2. The pHi decreased significantly when the paCO2 was increased by hypercapnia. The percentage of pH regulation, estimated from the linear regression analysis of pHi versus the logarithm of the paCO2 was 78%. This result indicates that spontaneously breathing unanesthetized animals have better pHi regulation under hypercapnia investigated than that estimated for higher levels of hypercapnia in previous studies on unanesthetized animals, suggesting that there is a threshold for this highly efficient regulation. Furthermore, there were no significant correlations between the PCr, ATP and Pi levels and the paCO2 levels during hypercapnia. This indicates that physiological variations of the CO2 tension in the blood, and consequently in the brain parenchyma, have little effect on cerebral energy metabolism in unanesthetized spontaneously breathing animals.
 ...
PMID:Cerebral intracellular pH regulation during hypercapnia in unanesthetized rats: a 31P nuclear magnetic resonance spectroscopy study. 236 88

A commercial neuroleptanalgesic acepromazine-etorphine combination administered intramuscularly to four horses produced a severe tachycardia and an increase in muscular tone, together with hypoxaemia, hypercapnia, metabolic acidosis associated with an increase in the packed cell volume and hyperglycaemia. No electrolyte changes were found. After reversal of the action of etorphine with diprenorphine, there was a prolonged decrease in the calcium and phosphorus serum concentrations and decreases in the packed cell volume and the total protein serum concentration. In a second experiment on the same four horses, glyceryl guaiacolate (10 g/100 kg body weight intravenously) was given as soon as the horses were anaesthetized with acepromazine-etorphine. The muscular rigidity disappeared and the tachycardia was less evident. There was a more pronounced hypoxaemia but the changes in the other parameters were similar to those in the first experiment. It was concluded that the neuroleptanalgesic-glyceryl guaiacolate combination is not a safe anaesthetic procedure in horses.
 ...
PMID:Haemodynamic, metabolic and physical responses to a neuroleptanalgesic-glyceryl guaiacolate combination in the horse. 250 40

Paralyzed rabbits ventilated with an oxygen, nitrous oxide, and carbon dioxide mixture were subjected to hyper- and hypocarbic stress. An Oxford Instrument TMR 32-200 spectrometer was used to record phosphorus-31 and nonwater proton nuclear magnetic resonance spectra of the in vivo brain. These spectra provide measurements of cerebral pHi, phosphocreatine, orthophosphate, ATP, and lactate. The brain exhibited twice as much acute pH-regulating ability as the arterial blood. During hypercarbia, orthophosphate rose while phosphocreatine declined in a reciprocal manner, and ATP remained constant. During hypocarbia, lactate rose gradually over a period of 1 hour, while orthophosphate, phosphocreatine, and ATP remained constant and calculated values of adenosine mono- and diphosphate rose.
 ...
PMID:Cerebral metabolism in hyper- and hypocarbia: 31P and 1H nuclear magnetic resonance studies. 293 95

1. The effects of hypercapnia and hypocapnia on brain intracellular pH (pHi) and metabolism were investigated in new-born lambs under barbiturate anaesthesia. 2. 31P nuclear magnetic resonance (n.m.r.) spectroscopy was used to determine brain pHi and the relative concentrations of compounds containing mobile phosphorus nuclei including phosphocreatine (PCr), nucleoside triphosphates (NTP) and inorganic phosphate (Pi). Simultaneous measurements were made of the molar ratio of glucose to oxygen uptake by the brain. 3. During normocapnia (arterial partial pressure of CO2 Pa, CO2, 39 +/- 1 mmHg mean +/- S.E. of mean, n = 9) brain pHi was 7.13 +/- 0.02. Hypercapnia (Pa, CO2, 98 +/- 3 mmHg) was associated with a fall in brain pHi to 6.94 +/- 0.03 (n = 19, P less than 0.001), whereas no significant change in brain pHi occurred during hypocapnia (Pa, CO2, 16 +/- 1 mmHg; brain pHi 7.15 +/- 0.01). 4. During hypercapnia there was an increase in the ratio of Pi to NTP from 1.09 +/- 0.08 to 1.47 +/- 0.06 (P less than 0.001) and a decrease in the ratio PCr/Pi from 1.60 +/- 0.08 to 0.93 +/- 0.04 (P less than 0.001). There was a linear correlation between Pi/NTP and brain pHi. 5. Alterations in arterial PCO2 had no significant effect on the molar ratio of glucose to oxygen uptake by the brain, which remained close to unity. 6. The change in brain pHi observed during hypercapnia can be accounted for by the known physico-chemical buffering capacity of brain tissue. Homoeostasis of brain pHi during hypocapnia provides further evidence that additional regulatory mechanisms operate in these circumstances. 7. The observed changes in PCr and Pi can be accounted for in part by the [H+] dependence of the creatine kinase reaction.
 ...
PMID:Brain intracellular pH and metabolism during hypercapnia and hypocapnia in the new-born lamb. 311 75


1 2 Next >>