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)

Experiments were conducted on cats under nembutal anesthesia; a study was made of pulse activity of bulbar respiratory neurons, electrical activity of the diaphragm and of the intercostal muscles; pO2, pCO2, pH, arterial blood oxygen saturation were determined in combined action of hypoxia and hypercapnia. When hypoxic gaseous mixture was given for respiration the developing hypocapnia disturbed the discharge rhythmic activity of the respiratory neurons, the respiration acquiring a pathological character of the Cheyne--Stokes type. After addition to the hypoxic gaseous mixture of 2% CO2 the gaseous composition of the arterial blood approached the initial values; this addition prevented the development of hypercapnia and disturbances of rhythmic discharge activity of the respiratory neurons. Addition of 5% CO2 to the hypoxic gaseous mixture produced a negative effect: at first it intensified and then depressed the pulse activity of the respiratory neurons, caused metabolic and respiratory acidosis, and promoted asphyxia.
 ...
PMID:[Combined effects of hypoxia and hypercapnia on the functional state of the respiratory center]. 0 Jan 3

The responsiveness of the medullary chemoreceptors, measured by the ventilatory response to hypercapnia given in an hyperoxic gas mixture in intact anesthetized dogs has been evaluated during normothermia and at two levels of hypothermia. The response was studied in: 1) 20 dogs during normothermia, 2) 10 of these dogs at a blood temperature of 32-33 degrees C, and 3) in the other 10 dogs during deeper hypothermia (28-29 degrees C). The ventilatory response to CO2 decreased while blood temperature was lowered until the response became absent during deep hypothermia. For normothermia and both levels of hypothermia a similar oxygen drive of ventilation was found which was equivalent to approximately one fourth of the spontaneous ventilation. It is suggested, that in the deeply hypothermic animal the normal respiratory drive is apparently of peripheral (arterial) chemoreceptor origin and when this drive is nullified or significantly decreased, gentle shivering could be responsible for stimulating the respiratory center.
 ...
PMID:Carbon dioxide response curves during hypothermia. 0 Jun 52

The effect of sustained hypercapnia on the acid-base balance and gill ventilation in rainbow trout, Salmo gairdneri, was studied. The response to an increase in PICO2 from 0.3 to 5.2 mm Hg was a five-fold increase in gill ventilation volume and a slight increase in breathing frequency. There was a concomitant rise in PACO2 and an immediate fall in pHa. If PICO2 was maintained at 5.2 mm Hg for several days, ventilation volume gradually returned to the initial, prehypercapnic level within three days. Arterial pH also returned to the initial level within 2-3 days. These results are consistent with the hypothesis that under these conditions fish regulate pH via HCO3/C1 exchange across the gills rather than by changes in ventilation and subsequent adjustment of PACO2. A reduction in environmental pH causes a reduction in pHa but only a slow gradual increase in VG. Injections of HC1 or NaHCO3 into the blood have opposite effects on pHa but both cause a marked increase in VG. It is concluded that a rise in PACO2 results in a rise in VG and that changes in pH in blood or water have little direct effect on VG in rainbow trout. Possible location for receptors involved in this reflex response are discussed.
 ...
PMID:The effects of changes in pH and PCO2 in blood and water on breathing in rainbow trout, Salmo gairdneri. 0 Jul 53

The effect of oxygen saturation and PCO2 on brain uptake of glucose analogues was studied in rabbits. Using a modified Oldendorf technique, 14C-labeled glucose analogues with a 3H2O reference standard were introduced into the cerebral circulation via the common carotid artery, and the radioactivity of the ipsilateral cerebral cortex was counted and expressed in terms of a brain uptake index (BUI). Severe hypoxia (oxygen saturation less than or equal to 18%) resulted in approximately a 40% decrease in the BUI of 2-deoxy-D-glucose and a 45% decrease in the BUI of 3-0-methyl-D-glucose. Severe hypercapnia (PCO2 = 100 mm Hg) caused a 45% decrease in the BUI of both of these glucose analogues. Hypercapnia superimposed on severe hypoxia had no additional effect. Hypocapnia (PCO2 = 15 mm Hg) increased the BUI of 3-0-methyl-D-glucose by 35% of the control value, and this increase was extremely sensitive to competitive inhibition. When BUI values were plotted against pH rather than PCO2 for the same experiments, there was a good correlation with the calculated linear regression. These results are compared with previous findings on pathologically induced changes in brain uptake of glucose analogues, and the possible role of blood flow is considered in detail.
 ...
PMID:Effects of oxygen saturation and pCO2 on brain uptake of glucose analogues in rabbits. 0 Aug 21

In vitro, the affinity of Hb for O2 depends on pH and capnia by the intermediate of the 2-3 DPG level, the concentration of which lowers in the case of acidosis and hypercapnia. Thus, an increase in the affinity results, but while Bohr's effect is immediate, on the contrary the 2-3 DPG effect is slow. Authors have verified the importance of this modification by studying the affinity of Hb for O2 thanks to the P50 technique in 15 normal non-smokers subjects and in 10 subjects with compensated or not respiratory acidosis but normally saturated thanks to continuous O2 administration.
 ...
PMID:[Study of P50 in patients under continuous O2 inhalation and during chronic respiratory acidosis]. 0 19

The cerebral haemodynamic effects of CT 1341 also called Alfatesin, an anaesthetic steroid, were studied in the cat by means of the Xenon 133 isotopic clearance method to measure the cerebral blood flow. The injection or intravenous drip of Alfatesin in animals whose arterio PCO2 was kept unchanged induced a cerebral blood flow diminution, the importance of which was proportional to the injected dose. The cerebral blood flow fall was partly due to a cerebral arterio vasoconstriction evidenced by direct observation of the cortex vessels and by a diminution of the intracranial presure. During a deep anaesthesia induced by Alfatesin with recurrent burst suppression, there was a loss of cerebral blood flow autoregulation while the CO2 cerebral vascular reactivity was maintained. This last result accounts for the increase in cerebral blood flow parallel to the hypercapnia that could be observed among animals breathing freely.
 ...
PMID:[Study of the effects of Alfatesin on cerebral blood flow in cats]. 0 57

1. The ventilatory responses to transient and steady-state hypoxia were measured in ten patients with hepatic cirrhosis and in ten healthy control subjects. Successive measurements of these responses were also obtained in six goats before and after the experimental production of liver failure. Changes in the effect of steady-state hypoxia on the ventilatory response to hypercapnia were evaluated by successive studies in another goat. 2. In spite of a respiratory alkalosis during liver failure, the response to transient hypoxia was greater in the patients than in the control subjects. This response was increased after the onset of liver failure in all the goats. 3. In healthy humans and goats the responses to transient and steady-state hypoxia were similar in magnitude. During liver failure there was a disparity between the size of these responses, since the ventilatory increment evoked by steady-state hypoxia was unchanged in spite of the increase in response to transient hypoxia. Steady-state hypoxia consistently enhanced the ventilatory response to hypercapnia in a healthy goat, but frequently depressed the response to hypercapnia during liver failure. 4. The findings suggest that liver failure heightens the sensitivity of the peripheral chemoreceptors to the hypoxic stimulus, but may increase the tendency of the medullary centres to become depressed in hypoxia.
 ...
PMID:Effect of liver failure on the ventilatory response to hypoxia in man and the goat. 0 6

The combined effect upon cerebral blood flow (CBF) of an elevation of cerebrospinal fluid pressure (CSFP) and changes in respiratory CO2 was studied in nine baboons under chloralose anesthesia. The animals were mildly hyperventilated and provided with increasing amounts of CO2 in O2-air. Arterial CO2 tensions (PaCO2) increased from 17 to 58 mm Hg. Internal carotid blood flow (ICBF) was measured at normal CSFP and at hydrostatically maintained 50 mm Hg CSFP. It was found that: 1) end-tidal CO2 may be used as a substitute for arterial PaCO2 determinations; 2) this elevation of CSFP has little effect on ICBF during hypercapnia and normocapnia; however, 3) during hypocapnia the ICBF is reduced an additional 20% when CSFP is elevated; that is, ICBF is reduced 50% from normal when end-tidal CO2 is reduced to 2% at this elevated level of CSFP. Caution should be exercised during hyperventilation therapy particularly if the elevated CSFP or intracranial pressure (ICP) is not reduced to approach normal levels; in these conditions, the combination of decreasing PaCO2 and elevated ICP may reduce CBF below critical levels and thus lead to cerebral hypoxia.
 ...
PMID:Effects of hyperventilation, CO2, and CSF pressure on internal carotid blood flow in the baboon. 0 53

In 85 patinets withstatus asthmaticus, the authors have studied the acid-base balance, the blood gas tensions and various humoral parameters. The values were classified into two groups according to the PaCO2 level: below or equal to 44 torr (Group I), higher than 44 torr (Group II). In the 58 cases of Group II, there was a very close positive correlation between PaCO2 and H + ions, practically the same as that established by BRACKETT et al. [3] in experimental acute hypercapnia in man. On the contrary, the correlation derived from cases of status asthmaticus in the literature showed, in some cases, a metabolic component in acidosis. In the present work, the mean value of lactates was close to normal; there was a slow increase in protein content and hematocrit, in the two groups. The prognosis of the status asthmaticus depends on the degrees of hypercapnia: when it reaches 70 torr, mechanical ventilation is urgently needed and is the main part of the treatment; the use of additional drugs remains a matter of specific case.
 ...
PMID:[Acid-base disorders in status asthmaticus (author's transl)]. 0 43

Dogfish were exposed to sudden changes of Pco2 in inspired seawater. During hypercapnia breathing frequency remained constant, but gill ventilation was transiently increased to about 140% of control levels in the 1st h. O2 uptake was significantly increased also, but returned to the initial level before nomalization of gill ventilation. In contrast to the transient rise in gill ventilation and O2 uptake, arterial Po2 was increased for the whole period of hypercapnia. Hypercapnia results in a marked fall in pHa which returned to the initial value in 4-5 h even though hypercapnia is maintained. This rise in pHa with little change in PaCO2 was associated with an increase in plasma bicarbonate concentration. The increase of plasma bicarbonate was in part due to compensatory bicarbonate uptake from the seawater across the gills and in part was effected by transfer between intracellular tissue compartments and extracellular spaces. The compensatory bicarbonate exchange mechanism in the gills seems to have a delay both after onset and termination of hypercapnia.
 ...
PMID:Ventilatory response to hypercapnia in the larger spotted dogfish Scyliorhinus stellaris. 0 74


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