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

The present study examined the effects of severe hypothermia in the absence of anesthesia on breathing pattern, ventilatory control and chemosensitivity in a cold tolerant species capable of seasonal hibernation. Hypothermia was induced in ground squirrels and ventilation and heart rate were recorded in animals breathing air at a body temperature (Tb) of 5 and 10 degrees C. The animals were then exposed to hypercapnic (2, 4 and 6% CO(2)) and hypoxic (12, 10, 8 and 4% O(2)) gas mixtures. We found that severe hypothermia in ground squirrels caused the breathing pattern to change from a continuous pattern to patterns that are commonly observed during hibernation. This suggests that temperature and metabolism alone are important factors in producing these patterns. The relative ventilatory sensitivity to hypercapnia was retained in the ground squirrel during hypothermia while ventilatory sensitivity to hypoxia was totally abolished. This is in contrast to hibernation where a small but significant hypoxic ventilatory response is present along with an enhanced relative response to hypercapnia. This suggests that changes in Tb alone can not account for the changes seen in ventilatory sensitivity during hibernation.
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PMID:Ventilatory pattern and chemosensitivity in unanesthetized, hypothermic ground squirrels (Spermophilus lateralis). 1238 31

We asked to what extent differences in caloric intake during the first postnatal weeks may modify thermal and respiratory control of 1-month old rats. Large-size (Large) and small-size (Small) rats were obtained by raising rats in, respectively, small (6 pups) and large (16 pups) litters. In Small, the rate of oxygen consumption (V(O(2))/kg) was less than in Large during the first 2-3 weeks, and higher thereafter, when the thermogenic needs to maintain body temperature (Tb) increased. At day 31, when body weight in Small was approximately 80% of Large, Small maintained Tb in the cold with higher V(O(2))/kg than Large. The total uncoupling protein of the brown adipose tissue was unchanged. Also pulmonary ventilation (VE/kg) was higher in Small, maintaining the proportionality with V(O(2)). Lung weight in Small was reduced in proportion to body weight, with higher protein-DNA ratio. The compliances of the respiratory system and lungs, normalized by body weight, and the hyperventilatory responses to hypoxia or hypercapnia, expressed as % increase in VE/V(O(2)), were similar in Small and Large. Differences between Small and Large were reduced or no longer present in a group of Small rats raised until their body weight was as in Large. We conclude that rather important developmental differences in caloric intake and metabolic level, in otherwise healthy rats, had no long-term carry over effects in the developmental processes of respiratory and thermal control, other than the effects strictly attributable to the alterations in body size.
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PMID:Thermal and respiratory control in young rats with altered caloric intake during postnatal development. 1242 69

We questioned to what extent sustained increases in metabolic rate during the neonatal period may influence the development of thermal and respiratory control. Male rats were exposed to cold (14 degrees C) for the first 3 weeks, which increased metabolic rate with small effects on body growth. Measurements were performed at 1 month of age, when the body weight of the Cold group averaged approximately 88% of Controls. In Cold rats, the concentration of the uncoupling protein of the brown adipose tissue was increased. Acute exposures to different ambient temperatures (5, 15, 25 and 35 degrees C) provoked changes in body temperature similar in Cold and in Control rats. At these temperatures, small differences in the absolute values of oxygen consumption (Vdot;(O(2))) between the two groups could be explained by the differences in body weight. Hematocrit and lung weight of Cold rats were as in Controls, but the lung protein-DNA ratio was increased because of a drop in lung cellularity. The resting ventilation-oxygen consumption ratio (Vdot;(E)/Vdot;(O(2))) was similar between Cold and Controls. Also the changes in Vdot;(O(2)) and Vdot;(E) during acute hypoxia (10% O(2)) or hypercapnia (5% CO(2)), and the corresponding hyperventilatory responses (increases in Vdot;(E)/Vdot;(O(2))) did not significantly differ between the two groups. In conclusion, in the rat, the increased metabolic requirements caused by cold exposure during the early postnatal phases improved the thermogenic capacity, while having negligible impact on the development of respiratory control.
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PMID:Thermal and respiratory control in young rats exposed to cold during postnatal development. 1254 75

We evaluated the effects of 2 h of warm (24 degrees C) and cold (6 degrees C) exposure on metabolism and ventilation (V(E)) in conscious male and female Harlan ICR Swiss Webster mice exposed to air, and 8% O(2) in N(2) (hypoxia) and to 5% CO(2) in O(2) (hypercapnia) for 2 min each at both temperatures. All cold-exposed mice increased O(2) consumption (V(O2)), and maintained body temperature. Cold-exposed females doubled their tidal volume, increased their V(E) fivefold, and doubled their ventilatory equivalent to V(O2) (V(E)/V(O2)). In contrast, cold-exposed males decreased tidal volume and doubled V(E) relative to warm exposure. The ventilatory equivalent of males was similar during warm and cold exposure. During warm exposure, mice of both genders increased their ventilatory responses to both hypoxia and to hypercapnia by different mechanisms. In contrast, during cold exposure, these responses were blunted relative to air measurements in females and decreased below air values in males. Thus, cold exposure was able to elicit gender-specific ventilatory and metabolic responses.
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PMID:Gender comparisons of control of breathing and metabolism in conscious mice exposed to cold. 1256 46

A disabled submarine (DISSUB) lacking power and/or environmental control will become cold, and the ambient air may become hypercapnic and hypoxic. This study examined if the combination of hypoxia, hypercapnia, and cold exposure would adversely affect thermoregulatory responses to acute cold exposure in survivors awaiting rescue. Seven male submariners (33 +/- 6 yrs) completed a series of cold-air tests (CAT) that consisted of 20-min at T(air) = 22 degrees C, followed by a linear decline (1 degrees C x min(-1)) in T(air) to 12 degrees C, which was then held constant for an additional 150-min. CAT were performed under normoxic, normocapnic conditions (D0), acute hypoxia (D1, 16.75% O2), after 4 days of chronic hypoxia, hypercapnia and cold (D5, 16.75% O2, 2.5% CO2, 4 degrees C), and hypoxia-only again (D8, 16.75% O2). The deltaTsk during CAT was larger (P < 0.05) on D0 (-5.2 degrees C), vs. D1 (-4.8 degrees C), D5 (-4.5 degrees C), and D8 (-4.4 degrees C). The change (relative to 0-min) in metabolic heat production (deltaM) at 20-min of CAT was lower (P < 0.05) on D1, D5, and D8, vs. D0, with no differences between D1, D5 and D8. DeltaM was not different among trials at any time point after 20-min. The mean body temperature threshold for the onset of shivering was lower on D1 (35.08 degrees C), D5 (34.85 degrees C), and D8 (34.69 degrees C), compared to D0 (36.01 degrees C). Changes in heat storage did not differ among trials and rectal temperature was not different in D0 vs. D1, D5, and D8. Thus, mild hypoxia (16.75% F1O2) impairs vasoconstrictor and initial shivering responses, but the addition of elevated F1CO2 and cold had no further effect. These thermoregulatory effector changes do not increase the risk for hypothermia in DISSUB survivors who are adequately clothed.
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PMID:Physiological responses to cold exposure in men: a disabled submarine study. 1267 Jan 21

beta-Adrenergic agonists may increase chemosensitivity in humans. We tested the hypothesis that the beta1-agonist dobutamine increases peripheral chemosensitivity in a double-blind placebo-controlled randomized and crossover study. In 15 healthy subjects, we examined the effects of dobutamine on breathing, hemodynamics, and sympathetic nerve activity (measured using microneurography) during normoxia, isocapnic hypoxia (10% O2), posthypoxic maximal voluntary end-expiratory apnea, hyperoxic hypercapnia, and cold pressor test (CPT). Dobutamine increased ventilation (7.5 +/- 0.3 vs. 6.7 +/- 0.2 l/min, P = 0.0004) during normoxia, markedly enhanced the ventilatory (16.1 +/- 1.6 vs. 11.4 +/- 0.7 l/min, P < 0.0001) and sympathetic (+403 +/- 94 vs. +222 +/- 5%, P < 0.03) responses at the fifth minute of isocapnic hypoxia, and enhanced the sympathetic response to the apnea performed after hypoxia (+501 +/- 107% vs. +291 +/- 38%, P < 0.05). No differences were observed between dobutamine and placebo on the responses to hyperoxic hypercapnia and CPT. Dobutamine increases ventilation during normoxia and potentiates the ventilatory and sympathetic responses to hypoxia in healthy subjects. Dobutamine does not affect the responses to hyperoxic hypercapnia and CPT. We conclude that dobutamine enhances peripheral chemosensitivity.
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PMID:Dobutamine potentiates arterial chemoreflex sensitivity in healthy normal humans. 1275 69

Scenarios of rising CO2 concentration in surface waters due to atmospheric accumulation of anthropogenic CO2, or in the deep sea due to anticipated industrial dumping of CO2, suggest that hypercapnia (elevated partial pressure of CO2) will become a general stress factor in aquatic environments, with largely unknown effects on species survival and well being, especially in cold and deep waters. For an analysis of CO2 effects at the cellular level, isolated hepatocytes were prepared from two representatives of the Antarctic fish fauna, Pachycara brachycephalum and Lepidonotothen kempi. Correlated changes in energy and protein metabolism were investigated by determining the rates of oxygen consumption at various levels of PCO2, of intra- and extracellular pH, and after inhibition of protein synthesis by cycloheximide. A decrease in extracellular pH (pHe) from control levels (pHe 7.90) to pHe 6.50 caused a reduction in aerobic metabolic rate of 34-37% under both normocapnic and hypercapnic conditions. Concomitantly, protein biosynthesis was inhibited by about 80% under conditions of severe acidosis in hepatocytes from both species. A parallel drop in intracellular pH probably mediates this effect. In conclusion, the present data indicate that elevated PCO2 may limit the functional integrity of the liver due to a pronounced depression in protein anabolism. This process may contribute to the limits of whole-animal tolerance to raised CO2 levels.
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PMID:Energy budget of hepatocytes from Antarctic fish (Pachycara brachycephalum and Lepidonotothen kempi) as a function of ambient CO2: pH-dependent limitations of cellular protein biosynthesis? 1455 31

Headache occasionally occurs during or after scuba diving. Although its significance often is benign, headache may signal a serious neurological disorder in some circumstances. In addition to the usual causes of headache, the diagnostic evaluation should consider otic and paranasal sinus barotrauma, arterial gas embolism, decompression sickness, carbon dioxide retention, carbon monoxide toxicity, hyperbaric-triggered migraine, cervical and temporomandibular joint strain, supraorbital neuralgia, carotid artery dissection, and exertional and cold stimulus headache syndromes. Focal neurologic symptoms, even in the migraineur, should not be ignored, but rather treated with 100% oxygen acutely and referred without delay to a facility with a hyperbaric chamber.
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PMID:Headache and facial pain in scuba divers. 1522 93

We have reviewed the role of afferent inputs and blood chemical changes to the central nervous system, and the way in which they modify the cough and expiration reflexes (CR and ER). Slowly adapting pulmonary stretch receptors (SARs) augment the CR, insofar as when their activity is abolished the CRs from the tracheobronchial (TB) tree and larynx are abolished or weakened. However, stimulation of SARs by lung inflation has an inconsistent effect on the CR. Activation of SARs strongly potentiates the ER from the vocal folds, by a reflex mechanism, and inhibition of SARs weakens the ER. Bronchopulmonary C-fibre receptors inhibit the CR, as do capsaicin-sensitive afferents from the heart and splanchnic bed, cutaneous cold receptors and those that respond to chest wall vibration. Nasal receptors responsive to the irritant agent capsaicin potentiate the reflex. Acute hypoxia also augments the CR, and the reflex is down-regulated by carotid body resection. On the other hand, the CR is inhibited by prolonged hypoxia and hyperoxia, and by hypercapnia. Thus different inputs to the cough-controlling mechanism in the brainstem have very varied effects on the CR. We conclude that the sensitivities of the CR and ER can be modified in a large variety of physiological and clinical conditions, and that there is no clear relationship between the reflexes and changes in breathing caused by the interventions.
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PMID:Regulation of cough by secondary sensory inputs. 1658 27

We have previously shown that mice with near-complete absence of 5-HT neurons (Lmx1bf/f/p) display a blunted hypercapnic ventilatory response (HCVR) and impaired cold-induced thermogenesis, but have normal baseline ventilation (), core body temperature (TCore) and hypoxic ventilatory responses (HVR) at warm ambient temperatures (TAmb; 30 degrees C). These results suggest that 5-HT neurons are an important site for integration of ventilatory, metabolic and temperature control. To better define this integrative role, we now determine how a moderate cold stress (TAmb of 25 degrees C) influences ventilatory control in adult Lmx1bf/f/p mice. During whole animal plethysmographic recordings at 25 degreesC, baseline , metabolic rate , and TCore of Lmx1bf/f/p mice were reduced (P < 0.001) compared to wild type (WT) mice. Additionally, the HCVR was reduced in Lmx1bf/f/p mice during normoxic (-33.1%) and hyperoxic (-40.9%) hypercapnia. However, in Lmx1bf/f/p mice was equal to that in WT mice while breathing 10% CO2, indicating that non-5-HT neurons may play a dominant role during extreme hypercapnia. Additionally, ventilation was decreased during hypoxia in Lmx1bf/f/p mice compared to WT mice at 25 degrees C due to decreased TCore. These data suggest that a moderate cold stress in Lmx1bf/f/p mice leads to further dysfunction in ventilatory control resulting from failure to adequately maintain TCore. We conclude that 5-HT neurons contribute to the hypercapnic ventilatory response under physiologic, more than during extreme levels of CO2, and that mild cold stress further compromises ventilatory control in Lmx1bf/f/p mice as a result of defective thermogenesis.
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PMID:Interaction between defects in ventilatory and thermoregulatory control in mice lacking 5-HT neurons. 1877 20


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