Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An investigation of acid and neutral triacylglycerol lipases in rat lung tissue has been carried out. The effect of high oxygen concentration in the inspired gas mixture on the activities of the two triacylglycerol lipases has been studied. Hyperoxia had a strong inhibitory effect on both enzymes, the degree of inhibition being dependent on the duration of exposure. Dibutyryl-3',5' AMP and NaF restored completely the activities of the inhibited triacylglycerol lipases, while adrenaline and caffeine had no effect. The possible mechanisms of the effects of oxygen on lung triacylglycerol lipases are discussed.
 ...
PMID:[Effect of hyperoxia on triacylglycerol lipase activity of the rat lung (author's transl)]. 19 50

Theoretical and experimental investigations have shown that the oxygen pressure field of an organ reflects the state of the oxygen supply of a tissue. Unfortunately it is practically impossible to measure the total oxygen pressure field. Meaurements of arterial and venous PO2 or of the mean tissue PO2 do not reveal the local tissue situation. Measurements together with K. Kunze and M. Kessler lead us to the conclusion, that the oxygen pressure field can be characterized sufficiently well by a PO2-histogram. Under normal conditions the PO2-histogram is bell shaped with a steeper left side. The form and position is rather consistent. In hypoxia low PO2 values increase causing a leftward shift of the histogram; in hyperoxia the bell shaped form is destroyed and the form becomes broader and irregular. The form of the histogram gives also information about the state of the regulation of the microflow. It can be measured by PO2 microelectrodes as well as by multiwire surface electrodes. Both techniques have been applied successfully with patients.
 ...
PMID:[The significance of the local oxygen pressure and of the PO2 histogram for the evaluation of the state of oxygen supply to various organs (author's transl)]. 19 96

We studied the effects on breathing rhythm of suppressing the major respiratory stimuli (wakefulness, vagal, peripheral and central chemoreceptors) in healthy, unanesthetized dogs. Respiratory frequency (f) was obtained with a pneumotachograph; the state of wakefulness (W) or sleep was determined by EEG and behavioral criteria. During quiet W, f averaged 17 breaths/min and minute volume of ventilation (VI), 8.4 l/min. In slow-wave sleep (SWS), f slowed to 14 breaths/min, and VI decreased to 6.8 l/min. Afferent vagal blockade during SWS slowed f to 4 breaths/min, due primarily to prolongation of expiratory duration (Te) to 13.3 s, and decreased VI to 4.8 l/min. One breath of 100% O2 prolonged Te further to 27.4 s. Central chemoreceptor sensitivity was then reduced by inducting a metabolic alkalosis that combined with SWS, vagal blockade, and hyperoxia prolonged Te to as long as 57 s and reduced f to as low as 1 breath/min. The results demonstrate that afferent respiratory stimuli are essential for sustaining adequate ventilation.
 ...
PMID:Primary role of respiratory afferents in sustaining breathing rhythm. 20 6

In order to investigate the effects of high concentrations of oxygen on the lung, experiments were performed on 18 baboons exposed to a humidified environment of 95% oxygen for five days. Open lung biopsies for biochemical assay, histologic and electron microscopic analysis and measurement of tissue respiration were performed before and after oxygen exposure. Pulmonary function was evaluated by measurement of arterial blood gases, compliance, closing capacity (CC), functional residual capacity (FRC), total lung capacity (TLC), residual volume (RV) and vital capacity (VC) before and after exposure and then at seven and 14 days in the animals which recovered. Six baboons removed from the oxygen environment after 96--110 hours and exposed to room air died within three to 20 hours of profound hypoxemia (PaO2 40 +/- 6). The remaining 12 baboons were successfully weaned to room air over a three day period with a return of ABGs to control values (PaO2 89+/- 2). Electron microscopic analysis of alveolar membranes exposed to 120 hours of hyperoxia demonstrated endothelial cell swelling, interstitial alveolar membrane edema, and an increased predominance of Type II pneumocytes. Lung volume measurements showed significant decreases in TLC (25%), VC (34%), CC/TLC (28%) and dynamic compliance (47%). Biochemical studies indicated a shift toward anaerobic metabolism with a decrese in tissue oxygen consumption, reduced cytochrome oxidase activity, and increased lung lactic acid production. These changes were all found to be reversible in the 12 baboons slowly weaned back to room air.
 ...
PMID:Reversible pulmonary oxygen toxicity in the primate. 21 38

O2-mediated alterations in cell energy metabolism may play a role in structural and functional abnormalities described in type II pneumocytes (T-II-P) following in vivo hyperoxia. Bioenergetic alterations produced by hyperoxia (95% O2) were therefore examined in a culture-maintained cell line derived from T-II-P. Exposure of cell monolayers to 95% O2 for 96 h results in a significant decrease in O2 consumption (from 0.52 +/- 0.07 to 0.30 +/- 0.08, P less than 0.01), suggesting impaired mitochondrial energy provision. In addition, there are increased rates of aerobic lactate production (from 2.89 +/- 0.52 to 3.84 +/-0.80, P less than 0.05) with loss of Pasteur effect, indicating a shift to glycolytic metabolism at relatively high PO2's. These metabolic changes are not accompanied by altered activities of critical mitochondrial (cytochrome oxidase) or glycolytic (pyruvate kinase, phosphofructokinase) enzymes. Altered cell bioenergetics following hyperoxia may this represent an important secondary mechanism leading to functional abnormalities in T-II-P.
 ...
PMID:Effects of high oxygen exposure on bioenergetics in isolated type II pneumocytes. 22 21

To study the ultrastructural effects of hyperoxia on the kidney, young adult Sprague Dawley rats were exposed to 3 atmospheres absolute (ATAs) of pure oxygen for 5 hours and were killed in a time sequence varying from immediately to 30 days after exposure. Their renal cortices were processed for electron microscopy. Selective mitochondrial changes were observed within sublethally and transiently altered proximal tubular epithelial cells. The most consistent finding was the accumulation of 0.08 mu to 0.5 mu round to ovoid homogeneous matrical inclusions which frequently formed larger confluent amorphous masses. The inclusions stained intensely with lead and uranium but appeared homogeneously electron-lucent in unstained sections. Energy-dispersive x-ray analysis revealed that they did not contain calcium or phosphorus. The inclusions were different from the innately electron-opaque flocculent densities commonly found in pathologically altered mitochondria. Since the mitochondria containing them were removed by autophagocytosis, it is suggested that the inclusions were associated with selective mitochondrial degeneration induced by hyperoxia. No glomerular lesions were found.
 ...
PMID:Selective mitochondrial degeneration in renal tubules following hyperbaric oxygen exposure. 22 8

By measuring ventilation during isocapnic progressive hypoxia, peripheral chemoreceptor sensitivity to acute hypoxia (deltaV40) was measured in five normal young men under four sets of conditions: 1) at sea level at the subject's resting PCO2, 2) at sea level with PCO2 5 Torr above resting PCO2, 3) after 24 h at a simulated altitude of 4,267 m (PB = 447 Torr) at the subject's resting PCO2 measured during acute hyperoxia, and 4) after 24 h at high altitude, with PCO2 elevated to the subject's sea-level resting PCO2. With this experimental design, we were able to systematically vary the PCO2 and [H+] at the peripheral and central chemoreceptors of man. When mean pHa was decreased from 7.424 to 7.377 without significant change in PACO2, the mean deltaV40 increased from 18.0 to 55.9 1/min. Conversely, when mean PACO2 was altered between 33.8 and 41.6 Torr with pHa held relatively constant, the mean deltaV40 did not change. This suggests that it is the H+ and not CO2 which interacts with hypoxia in stimulating the ventilation of man. An additional finding was that the intrinsic sensitivity of the peripheral chemoreceptors to acute hypoxia did not change during 24 h of acclimatization to high altitude.
 ...
PMID:Ventilatory interaction between hypoxia and [H+] at chemoreceptors of man. 24 Jul 97

Secretion of alpha-amylase by the human parotid gland increased significantly during eight days of hyperbaric exposure. This hyperactivity of the parotid gland presumably resulted from increased autonomic nervous system (ANS) activity attributable to (1)psychological stress in the form of anticipation; (2) dive-related factors, i.e., hyperoxia, PN2, physical stress; or (3) a combination of both. The etiology of the effect must await additional studies, but a consistent and significant elevation in alpha-amylas secretion was found. This previously undescribed effect of hyperbaric exposure indicates that parotid alpha-amylase sampling holds promise as a noninvasive means of monitoring physical and psychological stress, and as an indirect measure of ANS tone.
 ...
PMID:Human parotid alpha-amylase secretion as a function of chronic hyperbaric exposure. 31 98

The present study is the first investigation to demonstrate, by employing the combined approach of immunologically and electron microscope methods, the presence of actin-like contractile proteins in the mammalian retina, the corneal epithelium and endothelium, the iris, and the ciliary body, and to confirm their presence in lens epithelium. This is also the first report to demonstrate by these methods the presence of microfilaments and intermediate filaments in retinal vascular endothelium. Since we have shown that actin filaments are especially abundant in immature retinal endothelial cells, the question of their function arises, and we have discussed their possible relevance to the closure of immature retinal vessels when exposed to hyperoxia.
 ...
PMID:Contractile proteins in retinal endothelium and other non-muscle tissues of the eye. 36 Oct 70

Cells cultivated in 80% O2 were shown, by cytophotometric and histoautoradiographic methods, to undergo alterations concerning DNA, RNA and total proteins synthesis. These changes appear almost at the same time for all the above-named biological metabolites. Proliferative cell cycle undergoes changes before the blocking of the cells first in post-synthetic (G2) and then in pre-synthetic period (G1). It was also seen that protein synthetic rate of the cells is proportional to their DNA content, in other words tetraploid cells synthesize a double protein amount in comparison to diploid cells. Nucleolus labelling after Uridine-3H incorporation disappear the last under the effect of hyperoxia. Finally it was observed that DNA values (measured with scanning microscope) of prometaphase are higher than the mean values of other mitotic phases.
 ...
PMID:[Histochemical study of nucleic acids and proteins by cytophotometry and histoautoradiography in fibroblasts cultivated in hyperoxia (author's transl)]. 40 24


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