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)

The mechanisms and potential mediator of hypercapneic pulmonary hypertension are incompletely understood. We studied 18 dogs, anaesthetised and spontaneously breathing both room air and after the inhalation of a gas mixture containing 10% CO2, 20.9% O2, and 69.1% N2, to determine the role of histamine, serotonin, and acidaemia in pulmonary hypertension produced by hypercapnia. Hypercapnia increased the mean pulmonary artery pressure by 0.33 kPa (2.5 mmHg) while wedge pressure and pulmonary arteriolar resistance did not change. Cardiac output significantly increased, indicating that the pulmonary hypertensive effect of hypercapnia is mainly flow related. Neither chlorpheniramine nor methysergide had significant effects on hypercapneic pulmonary hypertension. The infusion of sodium bicarbonate corrected the pH; pulmonary artery pressure and cardiac output increased while pulmonary arteriolar resistance dropped, suggesting that the increased cardiac output masked the effect of pH on pulmonary arteriolar resistance. The lack of effect of chlorpheniramine or methysergide on pulmonary resistances indicates that the vasoconstrictive effect of increased hydrogen ion concentration which accompanies hypercapnia is attributable neither to histamine nor to serotonin release.
 ...
PMID:Mechanisms of hypercapneic pulmonary hypertension. 2 1

Experiments were performed to determine the relative effects of a net extracellular-to-intracellular HCO3- flux and of elevated carbon dioxide tension (PCO2) on cellular acid-base regulation. Isolated rabbit hearts were perfused by recirculating a small volume of Ringer solution in which the PCO2 and the HCO3- concentration could be independently altered. Net HCO3- flux was assessed by the disappearance of HCO3- from perfusate. Between 40 and 100 Torr PCO2, a HCO3- flux into the cell occurs only when perfusate HCO3- concentration is increased. Therefore, by selective manipulation of perfusate HCO3- and PCO2 it is possible to induce hypercapnia with or without an accompanying HCO3- flux. When perfusate HCO3- concentration was increased from 20 to 36 mM, cellular HCO3- concentration increased from 22.5 +/- 0.8 to 26.1 +/- 1.0 mM at 40 Torr PCO2 and from 27.8 +/- 0.7 to 34.1 +/- 1.4 mM at 98 Torr PCO2. These increases can be accounted for by the amount of HCO3- that disappeared from the perfusate. The results suggest that most of the initial cell CO2 buffering is provided by the net HCO3- flux in addition to the passive physicochemical buffering.
 ...
PMID:Contribution of a net transmembrane HCO3- flux to intracellular acid-base regulation. 2 30

DBcAMP or crystalline glucagon was utilized to elevate the intracellular cyclic AMP concentration in isolated rat hearts. Butyric acid, a metabolite of DBcAMP, was also investigated. Their effect on the intracellular pH (pHi) as determined by the distribution of [14C]DMO was investigated. Rat hearts, perfused with a recirculated modified Krebs-Henseleit solution maintained at 30 degrees C, were exposed to respiratory acidosis by bubbling the perfusate with 20% CO2. alpha- and beta-receptor antagonists were used to block the effects of endogenous catecholamines. Hypercapnia decreased the pHi from 7.09 to 6.82. A similar degree of hypercapnia decreased the pHi to only 6.95 in the presence of DBcAMP and to only 6.96 in the presence of glucagon. The effective buffer values (delta[HCO-3]i/deltapHi) were: control, 19; butyric acid, 16; DBcAMP, 139; glucagon, 148. These data suggest that cAMP mediates the effect of norepinephrine, which has been shown to diminish the change in pHi accompanying respiratory acidosis.
 ...
PMID:The effect of dibutyryl cyclic AMP and glucagon on the myocardial cell pH1. 2 69

Thirteen adult rabbits were exposed to a breathing air mixture containing an increasing amount of CO2 for eight weeks. When the CO2 content reached 9 Vol% the animals became apathic and lost body weight. The EEG showed a reduction of the amplitudes of 1o Hz frequences. Blood gases revealed an increase of bicarbonate but no change of pH. The blood brain barrier which was tested when the animals were killed was not disturbed. Enzyme histochemistry, light and electron microscopy revealed that moderate brain edema had occurred. From these results it is concluded that chronic hypercapnia has a hypnotic effect which in combination with chronic edema may depress vital activities considerably. However, there seem to be no irreversible morphological alterations of the brain.
 ...
PMID:The effect of prolonged experimental hypercapnia on the brain. 2 57

The cerebral blood flow was measured in the acutely exteriorized fetal lamb by 133Xenon washout and microsphere distribution techniques. The measurements were performed at different blood gas levels. Regional cerebral blood flow was calculated from the microsphere distribution for five different parts of the brain. This gave estimates for blood flow in both the grey and white matter of the hemispheres, which were in close agreement with the cerebral blood flow estimated by the 133Xe washout technique. The microsphere distribution shows that the fetal cerebral hemisphere has a low blood flow compared to the basel parts of the brain and that this difference is increased during hypoxia and hypercarbia.
 ...
PMID:Measurement of cerebral blood flow in the fetal lamb with a note on the flow-distribution. 2 60

The effects of hypercapnia on plasma renin concentration and blood pressure were studied in anaesthetized dogs, untreated and after pretreatment with guanethidine, propranolol or prazosin. An increase in plasma renin concentration which accompanied hypercapnia in untreated dogs was completely suppressed by pretreatment with guanethidine or propranolol. Prazosin significantly reduced but did not abolish renin release during hypercapnia. The pressor response normally occurring during hypercapnia was abolished by propranolol and reversed by guanethidine and prazosin.
 ...
PMID:Participation of the sympathetic and the renin--angiotensin systems in blood pressure control during hypercapnia in the anaesthetized dog. 2 75

Using a 14C-labeled DMO, 36Cl and 3H method, we have determined the in vivo buffering capacity of lung, kidney, heart, skeletal muscle, and extracellular fluid (ECF) of guinea pigs during hypercapnia (FICO2 = 0.15). After 1 days' exposureto 15% CO2, both the relative CO2 buffer values (delta HCO3/deltapH) and the "%pH regulation" were lung greater than kidney greater than heart greater than ECF greater than skeletal muscle. For lung tissue the intracellular pH was significantly decreased only during acute (8 h) hypercapnia and had completely returned to control values after 7 days with arterial PCO2 congruent to 122 Torr. Kidney and cardiac muscle also showed ca. 100% regulation of pH at 7 days, whereas skeletal muscle and ECF showed only 80 and 70% pH regulation, respectively. The results are discussed with respect to the important (and pH-dependent) metabolic functions of the lung and kidney.
 ...
PMID:Regulation of intracellular pH in lungs and other tissues during hypercapnia. 2 85

A 51-year-old woman with chronic respiratory failure (status after tuberculosis) was given an infusion of doxapram hydrochloride (1 to 2 mg/kg of body weight per hour) for four episodes of acute exacerbation of her condition. Treatment with the drug prevented worsening of hypercapnia in the four episodes, when administration of 24 percent oxygen had occasioned rises in the arterial carbon dioxide tension of 23, 10, 9, and 7 mm Hg.
 ...
PMID:Doxapram hydrochloride in the treatment of acute exacerbation of chronic respiratory failure. A patient with four episodes treated without use of a respirator. 2 44

To test the hypothesis that birth asphyxia has a role in the etiology of intraventricular hemorrhage (IVH), blood was collected from the umbilical artery (UA) at birth in 28 premature infants of 26 to 29 weeks gestation and analyzed for hydrogen ion concentration [H+], PCO2, standard bicarbonate level, and lactic acid level. The infants were followed up throughout their nursery stay until a diagnosis of IVH could be made or excluded, either by autopsy or clinical findings. Infants with IVH had lower Apgar scores. There were no differences in UA [H+] or bicarbonate or lactic acid levels. However, infants with IVH had a significantly higher UA PCO2. Although the difference appeared relatively small, the increase in PCO2 during labor may have been relatively large. It is concluded that hypercarbia, possibly by increasing cerebral blood flow, may be one important factor in the genesis of IVH.
 ...
PMID:Hypercarbia at birth: a possible role in the pathogenesis of intraventricular hemorrhage. 3 Sep 36

Twelve rhesus monkeys were delivered prematurely at 129, 130, or 131 days. The first breath was inhibited while tracheotomy was performed and a catheter introduced into the umbilical artery. Into the tracheal tubes of six of the newborn monkeys was instilled 0.20 to 0.27 ml. of a natural surfactant (SA) suspension, obtained from lung wash of adult rabbits. Nothing was given to six control monkeys. Breathing was then supported with a ventilator. Although its settings were adjusted in attempts to maintain normal blood gases, the control monkeys developed severe hypercapnia and acidosis, and two died after 4 1/2 and 5 1/2 hours. The remaining four control monkeys and the six treated monkeys were killed after six hours. Pulmonary pressure-volume characteristics were conspicuously better following SA treatment. It was concluded that instillation of SA in the upper airways of premature primates prior to their first breath holds promise as an effective way of preventing respiratory distress.
 ...
PMID:Improved ventilation of prematurely delivered primates following tracheal deposition of surfactant. 3 Oct 91


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>