共查询到20条相似文献,搜索用时 15 毫秒
1.
Vollmer C Schwartges I Obermiller K Beck C Picker O 《General physiology and biophysics》2012,31(1):27-37
This study was designed to compare the effects of different ways of administering carbon monoxide (intravenous and inhalative) on gastric mucosal oxygenation in a canine model of hemorrhage. Six chronically instrumented dogs were repeatedly anesthetized and randomized to each of the following protocols: In a first series the animals were ventilated either with 100 ppm carbon monoxide (CO) or without followed by hemorrhage and re-transfusion. In a second series a saturated CO solution was infused, compared to normal saline, again followed by hemorrhage and re-transfusion. In a control series, animals received either CO-saline or saline without any further intervention. Microvascular oxygenation of the gastric mucosa (μHbO2) was assessed continuously by tissue reflectance spectrophotometry. Cardiac output was measured intermittently and oxygen delivery (DO2) was calculated. The application of CO, inhalative and intravenous, increased carboxyhemoglobin levels without effect on μHbO2. Hemorrhage reduced μHbO2 in all groups, paralleled by a reduction in DO2 without any differences between groups related to the application of CO. Neither intravenous nor inhalative application of CO alters μHbO2 during physiological conditions or during hemorrhage. Thus, independent of the application way, low dose CO does not seem to modulate regional mucosal oxygenation in cytoprotective concentrations. 相似文献
2.
K K Za?tseva V I Skorik K E Maksimovich 《Biulleten' eksperimental'no? biologii i meditsiny》1986,101(5):624-628
Electron microscopic studies of lung aerohematic barrier were performed in 10 dogs under condition of severe hypoventilation hypoxia, using membrane oxygenator "Sever-OMR". Acute hypoxia treated with extrapulmonary membrane oxygenation was characterized by less deep and disseminated ultrastructural changes in aerohematic barrier than that treated without membrane oxygenation. The data obtained show positive effect of extracorporeal membrane oxygenation on lung tissues. 相似文献
3.
Karen I. Miller Charlotte P. Mangum 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(5):547-552
1. The pH dependence of Octopus dofleini hemocyanin oxygenation is so great that below pH 7.0 the molecule does not become fully oxygenated, even in pure O2 at 1 atm pressure. However, the curves describing percent oxygenation as a function of PO2 appear to be gradually increasing in oxygen saturation, rather than leveling out at less than full saturation. Hill plots indicate that at pH 6.6 and below the molecule is stabilized in its low affinity conformation. Thus, the low saturation of this hemocyanin in air is due to the very large Bohr shift, and not to the disabling of one or more functionally distinct O2 binding sites on the native molecule. 2. Experiments in which pH was monitored continuously while oxygenation was manipulated in the presence of CO2 provide no evidence of O2 linked binding of CO2. While CO2 does influence O2 affinity independently of pH, its effect may be due to high levels of HCO3- and CO3-, rather than molecular CO2, and it may entail a lowering of the activities of the allosteric effectors Mg2+ and Ca2+. 相似文献
4.
Russo A Tellone E Ficarra S Giardina B Bellocco E Lagana' G Leuzzi U Kotyk A Galtieri A 《Physiological research / Academia Scientiarum Bohemoslovaca》2008,57(1):49-54
During vertebrate evolution, structural changes in red blood cells (RBC) and hemoglobin (Hb), have probably resulted in the importance of blood carbon dioxide transport. The chloride/bicarbonate exchange across the RBC membrane, which is an integral part of the blood CO(2) transport process in vertebrates, has been examined on two different species of teleost fish, Euthynnus alletteratus and Thunnus thynnus, at several oxygenation states of erythrocyte HOS (high-oxygenation state, about 90 % of saturation) and LOS (low-oxygenation state, about 15 % of saturation). The results were compared with those observed in human RBC under the same experimental conditions and with the chicken (Gallus gallus) erythrocytes, which have particular modifications at the N-terminus of the band 3 protein (B3). In fish the kinetic measurements have shown a different anion transport in several oxygenation states of erythrocytes, indicating that also at lower levels of vertebrate evolution there exists a modulation of the anionic flow affected by oxygen. The functional correlation of anion transport to changes of parts of the hemoglobin sequence responsible for alterations in the interactions with the cytoplasmic domain of band 3 protein (cdb3) allowed us to suggest a hypothesis about fish physiology. The highest values of kinetic measurements observed in fish have been attributed to the metabolic need of the RBC in response to the removal of CO(2) that in teleosts is also of endogenous origin. 相似文献
5.
Electricity generation in a microbial fuel cell (MFC) using carbon monoxide (CO) or synthesis gas (syngas) as a carbon source has been demonstrated recently. A major challenge associated with CO or syngas utilization is the mass transfer limitation of these sparingly soluble gases in the aqueous phase. This study evaluated the applicability of a dense polymer silicone membrane and thin wall silicone tubing for CO mass transfer in MFCs. Replacing the sparger used in our previous study with the membrane systems for CO delivery resulted in improved MFC performance and CO transformation efficiency. A power output and CO transformation efficiency of up to 18 mW (normalized to anode compartment volume) and 98%, respectively, was obtained. The use of membrane systems offers the advantage of improved mass transfer and reduced reactor volume, thus increasing the volumetric power output of MFCs operating on a gaseous substrate such as CO. 相似文献
6.
Removal of CO dehydrogenase from Pseudomonas carboxydovorans cytoplasmic membranes, rebinding of CO dehydrogenase to depleted membranes, and restoration of respiratory activities.
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In Pseudomonas carboxydovorans, CO dehydrogenase and hydrogenase were found in association with the cytoplasmic membrane in a weakly bound and a tightly bound pool. The pools could be experimentally distinguished on the basis of resistance to removal by washes in low-ionic-strength buffer. The tightly bound pool of the enzymes could be differentially solubilized under conditions leaving the electron transport system intact and with the nondenaturing zwitterionic detergent 3-(3-cholamidopropyl) dimethylammonio 1-propane-sulfonic acid (CHAPS) and the nonionic detergent dodecyl beta-D-maltoside. In vitro reconstitution of depleted membranes with the corresponding supernatants containing CO dehydrogenase led to binding of the enzyme and to reactivation of respiratory activities with CO. The reconstitution reaction required cations with effectiveness which increased with increasing ionic charge: monovalent (Li+), divalent (Mg2+, Mn2+), or trivalent (Cr3+, La3+). Reconstitution of depleted membranes with CO dehydrogenase was specific for CO-grown bacteria. Cytoplasmic membranes from H2- or heterotrophically grown Pseudomonas carboxydovorans had no affinity for CO dehydrogenase at all, indicating the absence of the physiological electron acceptor of the enzyme, which presumably is cytochrome b561, or another membrane anchor. 相似文献
7.
Katsumi Yufu Takehiko Itoh Rei Edamatsu Akitane Mori Masahisa Hirakawa 《Neurochemical research》1993,18(9):1033-1039
It is reported that CNS hemorrage causes membrane dysfunction and may exacerbate this damage as a result of secondary ischemia or hypoxia. Since hyperbaric oxygenation improves oxygen metabolism, it may reduce this membrane damage. The present study was conducted to reveal whether hyperbaric oxygenation influences membrane alteration after hemorrhage. Thirty minutes after subarachnoid hemorrhage induction, rats were treated with hyperbaric oxygenation 2 ATA for 1 hour. Rats were decapitated 2 hours after subarachnoid hemorrhage induction. Na+, K+-ATPase activity measurement, and spin-label studies were performed on crude synpatosomal membranes. Subarachnoid hemorrhage decreased Na+, K+-ATPase activity. Spin label studies showed that hydrophobic portions of near the membrane surface became more rigid and the mobility of the membrane protein labeled sulfhydryl groups decreased after subarachnoid hemorrhage. Hyperbaric oxygenation significantly ameliorated most of the subarachnoid hemorrhage induced alterations. We conclude that hyperbaric oxygenation may be a beneficial treatment for acute subarachnoid hemorrhage. 相似文献
8.
The course of intracellular pH (pHi) was followed in superfused (36 degrees C) single glomus (type I) cells of the freshly dissociated adult rat carotid body. The cells had been loaded with the pH-sensitive fluorescent dye 2',7'-(2-carboxyethyl)-5 (and -6)-carboxyfluorescein. The high K(+)-nigericin method was used for calibration. The pHi of the glomus cell at pHo 7.40, without CO2, was 7.23 +/- 0.02 (n = 70); in 5% CO2/25 mM HCO3-, pHi was 7.18 +/- 0.08 (n = 9). The pHi was very sensitive to changes in pHo. Without CO2, delta pHi/delta pHo was 0.85 (pHo 6.20-8.00; 32 cells), while in CO2/HCO3- this ratio was 0.82 irrespective of whether pHo (6.80-7.40; 14 cells) was changed at constant PCO2 or at constant [HCO3-]o. The great pHi sensitivity of the glomus cell to pHo is matched only by that of the human red cell. An active Na+/H+ exchanger (apparent Km = 58 +/- 6 mM) is present in glomus cells: Na+ removal or addition of the amiloride derivative 5-(N,N-hexamethylene)-amiloride induced pHi to fall by as much as 0.9. The membrane of these cells also contains a K+/H+ exchanger. Raising [K+]o from 4.7 to 25, 50, or 140 mM reversibly raised pHi by 0.2, 0.3, and 0.6, respectively. Rb+ had no effect, but in corresponding concentrations of Tl+ alkalinization was much faster than in K+. Reducing [K+]o to 1.5 mM lowered pHi by 0.1. These pHi changes were shown not to be due to changes in membrane voltage, and were even more striking in the absence of Na+. Intrinsic buffering power (amount of strong base required to produce, in the nominal absence of CO2, a small pHi rise) increased from 3 to approximately 21 mM as pHi was lowered, but remained nearly unchanged below pHi 6.60. The fitted expression assumed the presence of one "equivalent" intracellular buffer (pK 6.41, 41 mM). The exceptional pHi sensitivity to pHo suggests that the pHi of the glomus cell is a link in the chemoreceptor's response to external acidity. 相似文献
9.
Monitoring the specific respiration rate (Q(O2)) is a valuable tool to evaluate cell growth and physiology. However, for low Q(O2) values the accuracy may depend on the measurement methodology, as it is the case in animal cell culture. The widely used "Dynamic Method" imposes serious difficulties concerning oxygen transfer cancellation, especially through membrane oxygenation. This paper presents an improved procedure to this method, through an automated control of the gas inlet composition that can minimize the residual oxygen transfer driving force during the Q(O2) measurement phase. The improved technique was applied to animal cell cultivation, particularly three recombinant S2 (Drosophila melanogaster) insect cell lines grown in a membrane aeration bioreactor. The average measurements of the proposed method reached 98% of stationary liquid phase balance method, taken as a reference, compared to 21% when the traditional method was used. Furthermore, this methodology does not require knowledge of the volumetric transfer coefficient k(L)a, which may vary during growth. 相似文献
10.
We have shown previously that OK cells recover from an acid load in a medium nominally CO2-free by extruding H via a Na/H exchanger and a passive H-conductive pathway. In this work, the regulation of cell pH (pHi) was studied after addition or withdrawal of CO2/HCO3 (5% CO2, 95 mM HCO3, pH = 8) using the fluoroprobe BCECF. In the presence of Na and amiloride to inhibit Na/H exchange, the recovery of pHi after CO2 entry and CO2 exit were found to depend in part on HCO3 entry and exit, respectively. Efflux of H per se also contributed to restoring pHi after CO2 addition, whereas H influx may have played a smaller role to normalize pHi after CO2 removal. DIDS, 0.5 mM, significantly inhibited both recovery phases of pHi. Removal of Na failed to inhibit the recovery of pHi after CO2 addition and removal. Cl removal also failed to inhibit pHi recovery after CO2 removal. Cell depolarization in the presence of Na moderately stimulated the pHi recovery rate after CO2 addition whereas it markedly inhibited the normalization of pHi after CO2 removal. Cell depolarization in the absence of sodium had only a slight effect to increase pHi recovery after CO2 addition but markedly prevented the pHi recovery after CO2 removal. These results indicate that OK cells lack Na or Cl-dependent HCO3 transport systems. The OK cell possesses a novel stilbene-sensitive electrogenic HCO3 transport system that is involved in the regulation of cell pH. 相似文献
11.
D S Patil M H Czechowski B H Huynh J LeGall H D Peck D V DerVartanian 《Biochemical and biophysical research communications》1986,137(3):1086-1093
The effect of low concentrations of CO (0.93 - 5.58 microM) on the EPR spectrum of the periplasmic non-heme iron hydrogenase from D. vulgaris has been investigated. The "g = 2.06" EPR signal is maximally induced (0.94 spin/molecule) at 46.5 microM CO and partial induction of the EPR signal could be observed at 0.93 microM CO. This effect is reversed by removal of the CO or irradiation of the hydrogenase with white light. 相似文献
12.
Background
Sedation agents affect brain hemodynamic and metabolism leading to specific modifications of the cerebral blood oxygenation level. We previously demonstrated that ultra-high field (UHF) MRI detects changes in cortical blood oxygenation following the administration of sedation drugs commonly used in animal research. Here we applied the UHF-MRI method to study clinically relevant sedation drugs for their effects on cortical and subcortical (thalamus, striatum) oxygenation levels.Methods
We acquired T2*-weighted images of Sprague-Dawley rat brains at 17.2T in vivo. During each MRI session, rats were first anesthetized with isoflurane, then with a second sedative agent (sevoflurane, propofol, midazolam, medetomidine or ketamine-xylazine) after stopping isoflurane. We computed a T2*-oxygenation-ratio that aimed at estimating cerebral blood oxygenation level for each sedative agent in each region of interest: cortex, hippocampus, thalamus and striatum.Results
The T2*-oxygenation-ratio was consistent across scan sessions. This ratio was higher with inhalational agents than with intravenous agents. Under sevoflurane and medetomidine, T2*-oxygenation-ratio was homogenous across the brain regions. Intravenous agents (except medetomidine) induced a T2*-oxygenation-ratio imbalance between cortex and subcortical regions: T2*-oxygenation-ratio was higher in the cortex than the subcortical areas under ketamine-xylazine; T2*-oxygenation-ratio was higher in subcortical regions than in the cortex under propofol or midazolam.Conclusion
Preclinical UHF MRI is a powerful method to monitor the changes in cerebral blood oxygenation level induced by sedative agents across brain structures. This approach also allows for a classification of sedative agents based on their differential effects on cerebral blood oxygenation level. 相似文献13.
Jagger JE Bateman RM Ellsworth ML Ellis CG 《American journal of physiology. Heart and circulatory physiology》2001,280(6):H2833-H2839
The release of ATP from red blood cells (RBC) in response to low O2 levels is linked to ATP production and the oxygenation state of hemoglobin. Because O2 is unloaded from the RBC, the concentration of deoxygenated hemoglobin increases, displacing phosphofructokinase from the cytoplasmic domain of band 3. We hypothesize that the ATP molecules produced through this glycolytic stimulation at the membrane surface result in the release of ATP from the RBC. Rat whole blood exposed to 5 min of low PO2 in vitro increased plasma [ATP] by 1.0 miccroM (+45%). This increase was reduced to 0.1 microM (+12%, P < 0.05) after citrate incubation and reversed after fluoride treatment (both glycolytic inhibitors) by -0.2 microM (-23%, P < 0.05). Plasma [ATP] of control RBC decreased -0.3 microM (-12%) when 8% CO (P < 0.05) was added to the chamber. Because CO and O2 bind competitively to heme, these results support our hypothesis that the release of ATP from RBC is linked to ATP production through the oxygenation state of the hemoglobin molecule. 相似文献
14.
Goddard PJ Takahashi S Milbank AJ Silen W Soybel DI 《Canadian journal of physiology and pharmacology》1998,76(9):882-890
HCO3(-) secretion across in vitro duodenal mucosa of Rana catesbeiana was investigated under baseline conditions and during secretory stimulation. Baseline secretion was abolished by removal of CO2-HCO3(-)and reduced approximately 60% by removal of nutrient Na+, but was not sensitive to changes in Cl- or K+. Baseline secretion was not directly altered by exposure to 10(-3) M amiloride or 10(-3) M H2DIDS (dihydro-4,4'-diisothiocyanostilbene-2,2'-disulfonic acid) in the nutrient solution and only mildly reduced by acetazolamide. Following removal and restoration of Na+, recovery of secretion was impaired by exposure to acetazolamide (5 x 10(-4) M) or H2DIDS (5 x 10(-4) M) in the nutrient solution. Secretion stimulated by glucagon (10(-6) M) or 16,16-dimethyl prostaglandin E2 (10 microg.mL(-1)) was markedly attenuated by removal of Na+ or by exposure to H2DIDS, but secretion was not altered by acetazolamide (5 x 10(-4) M) or nutrient amiloride (1 mM). Thus, the HCO3(-) that is secreted under nonstimulated conditions derives partly from basolateral Na(+)-dependent uptake and partly from cellular CO2 hydration. Secretagogue-stimulated secretion by duodenal surface epithelium depends on stilbene-sensitive Na+(HCO3(-))n uptake across the basolateral membrane. 相似文献
15.
Kaldenhoff R 《Current opinion in plant biology》2012,15(3):276-281
Plants provide an excellent system to study CO(2) diffusion because, under light saturated conditions, photosynthesis is limited by CO(2) availability. Recent findings indicate that CO(2) diffusion in leaves can be variable in a short time range. Mesophyll CO(2) conductance could change independently from stomata movement or CO(2) fixing reactions and it was suggested that, beside others, the membranes are mesophyll CO(2) conductance limiting components. Specific aquaporins as membrane intrinsic pore proteins are considered to have a function in the modification of membrane CO(2) conductivity. Because of conflicting data, the mechanism of membrane CO(2) diffusion in plants and animals is a matter of a controversy vivid debate in the scientific community. On one hand, data from biophysics are in favor of CO(2) diffusion limiting mechanisms completely independent from membrane structure and membrane components. On the other, there is increasing evidence from physiology that a change in membrane composition has an effect on CO(2) diffusion. 相似文献
16.
The Breuer-Hering inflation reflex [BHIR] was elicited in conscious and anaesthetized rats by inflating the lungs with constant pressures of 5--20 cm H2O. The reflex was elicited well in conscious animals, but even with the maximum stimulus [inflation of 20 cm H2O, corresponding to about 4.5-fold the tidal volume] the duration of apnoea did not exceed 4 control respiration cycles. In anaesthetized animals, the same stimulus let to apnoea lasting 180--400 control respiration cycles on the average, according to the type and depth of general anaesthesia. The duration of apnoea in occlusion of the air passages in the expiratory position increased with the depth of anaesthesia, while in occlusion of the air passages at the peak of inspiration it was shortened. Stimulation of chemoreceptors [inhalation of a mixture 4% CO2 in O2 or of 8% O2 in N2] did not influence the elicitability or duration of the BHIR, nor did cooling the rats to 28 degrees C or heating them to 38 degrees C. The mean respiration frequency was 98 c/min in unanaesthetized rats, 96 c/min in urethane anaesthesis and 79--48 c/min in halothane anaesthesia, according to the depth of anaesthesia. Bilateral cervical vagotomy reduced mean respiration frequency to 35.6 c/min in conscious rats and to 31 c/min in urethane-anaesthetized animals. The results indicate the existence of species-related differences between basic regulatory mechanisms in the rat and certain other mammals. 相似文献
17.
Vgontzas AN 《Archives of physiology and biochemistry》2008,114(4):211-223
Despite the early recognition of the strong association between obstructive sleep apnoea (OSA) and obesity, and OSA and cardiovascular problems, sleep apnoea has been treated as a "local abnormality" of the respiratory track rather than as a "systemic illness". In 1997, we first reported that the pro-inflammatory cytokines interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNFalpha) were elevated in patients with disorders of excessive daytime sleepiness (EDS) and proposed that these cytokines were mediators of daytime sleepiness. In subsequent studies, it was shown that IL-6, TNFalpha, and insulin levels were elevated in sleep apnoea independently of obesity and that visceral fat was the primary parameter linked with sleep apnoea. Further studies showed that women with the polycystic ovary syndrome (PCOS) were much more likely than controls to have sleep-disordered breathing (SDB) and daytime sleepiness, suggesting a pathogenetic role of insulin resistance in OSA. Additional accumulated evidence that supports the role of obesity and the associated metabolic aberrations in the pathogenesis of sleep apnoea and related symptoms include: obesity without sleep apnoea is associated with daytime sleepiness; the protective role of gonadal hormones as suggested by the increased prevalence of sleep apnoea in post-menopausal women and the significantly reduced risk for OSA in women on hormonal therapy; partial effects of continuous positive airway pressure (CPAP) in obese patients with apnoea on hypercytokinemia, insulin resistance indices, and visceral fat; and that the prevalence of the metabolic syndrome in the U.S. population from the Third National Health and Nutrition Examination Survey (1988-1994) parallels the prevalence of symptomatic sleep apnoea in general random samples. Furthermore, the beneficial effect of a cytokine antagonist on EDS and apnoea in obese, male apnoeics and that of exercise and weight loss on SDB and EDS in general random or clinical samples, supports the hypothesis that cytokines and insulin resistance are mediators of EDS and sleep apnoea in humans. Finally, our recent finding that in obese, hypothalamic CRH neuron is hypoactive, provides additional evidence on the potential central neural mechanisms for depressed ventilation and consequent development of sleep apnoea in obese individuals. In conclusion, accumulating evidence provides support to our thesis that obesity via inflammation, insulin resistance, visceral adiposity, and central neural mechanisms, e.g. hypofunctioning hypothalamic CRH, play a major role in the pathogenesis of sleep apnoea, sleepiness, and the associated cardiovascular co-morbidities. 相似文献
18.
Hausler R; Kleines M; Uhrig H; Hirsch H; Smets H 《Journal of experimental botany》1999,50(336):1231-1242
The effect of decreased or increased
phosphoenolpyruvate carboxylase (PEPC) activity on the
CO2 compensation point, respiration in the light or dark as well as the
partitioning of carbon into starch, soluble sugars, organic acids, and
amino acids was investigated using transgenic potato plants. Engineered
PEPC activity ranged form 0.5-fold wild-type level in antisense plants to
5-fold wild-type levels in lines overexpressing the
ccpc gene of Corynebacterium
glutamicum encoding for a PEPC not modulated by protein
phosphorylation. The CO2 compensation point determined according to Brooks
and Farquhar (1985) was lower in PEPC overexpressors (32 l l-1 CO2) compared to control
potato lines (38 l l-1
CO2), but was increased in antisense PEPC plants (42
l-1 CO2). 3-fold overexpression of PEPC gave a
minimum CO2 compensation point of 32 l l-1
CO2. Increased PEPC activity resulted in enhanced respiration in the light
and dark. Altered PEPC activity had no effect on the pattern of
14CO2 incorporation into leaf discs in the light.
14C pulse-chase experiments in the dark,
demonstrated that substantially more total label was lost in the leaf discs
from PEPC overexpressors. Metabolite levels were determined in 21 PEPC
overexpressing lines after 8 h in the light. A 5-fold increase in PEPC over
the wild-type increased malate (61%), starch (75%) and significantly
increased sucrose contents 9150%). Total amino acid contents were only
marginally increased. From gas exchange characteristics and labeling
experiments it was concluded that PEP carboxylation, followed by an
increased rate of respiratory CO2 release, might work as a
HCO3-/CO2 pump. This might result in elevated CO2/O2
ratios in the mesophyll, concomitant with a more favoured
carboxylation/oxygenation ratio of ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco). 相似文献
19.
《Journal of Biomedical Engineering》1985,7(2):89-99
Gas transfer performance is presented for one form of the Oxford membrane lung in which vortex mixing is induced in blood flow across a dimpled polypropylene membrane. Dimensional analysis has been used to define the parameters characterizing mass transfer in the device, and of three fluid mechanical parameters: Reynolds number based on peak pulsation velocity, Strouhal number, and ratio of mean to oscillatory flows, only the first has been found to affect mass transfer significantly in the ranges studied. For oxygenation, rated flows in excess of 5 l min−1 m−2 are measured. A new definition is presented for a rated flow for extracorporeal CO2 removal and values in excess of 1.2 l min−1 m−2 are obtained. 相似文献
20.