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101.
We develop tidal-ventilation pulmonary gas-exchange equations that allow pulmonary shunt to have different values during expiration and inspiration, in accordance with lung collapse and recruitment during lung dysfunction (Am. J. Respir. Crit. Care Med. 158 (1998) 1636). Their solutions are tested against published animal data from intravascular oxygen tension and saturation sensors. These equations provide one explanation for (i) observed physiological phenomena, such as within-breath fluctuations in arterial oxygen saturation and blood-gas tension; and (ii) conventional (time averaged) blood-gas sample oxygen tensions. We suggest that tidal-ventilation models are needed to describe within-breath fluctuations in arterial oxygen saturation and blood-gas tension in acute respiratory distress syndrome (ARDS) subjects. Both the amplitude of these oxygen saturation and tension fluctuations, and the mean oxygen blood-gas values, are affected by physiological variables such as inspired oxygen concentration, lung volume, and the inspiratory:expiratory (I:E) ratio, as well as by changes in pulmonary shunt during the respiratory cycle. 相似文献
102.
Richard A. Sternbach Artstotle A. Alexander David G. Rice Norman S. Greenfield 《Psychophysiology》1969,6(1):1-5
The treatment of artifactual responses in psychophysiology is rarely discussed or made explicit in research reports. The rationales and procedures of five approaches are presented: excluding the data; averaging other epochs; subjective estimation; straight-line connecting; and following the pen. Each approach is based on a somewhat different theoretical orientation, and the choice of each will depend on the researcher's theoretical preference and also the relative “costs” of losing data vs programming special instructions. Other considerations such as objectivity, consistency, and replicability are discussed. 相似文献
103.
K. J. Ullrich G. Rumrich S. Klöss 《Pflügers Archiv : European journal of physiology》1984,402(3):264-271
In order to study contraluminal sulfate transport the influx rate of35SO
4
2–
from the interstitium into cortical tubular cells has been determined. Preloading of the rat with sulfate augmented contraluminal35SO
4
2–
influx; preperfusion with sulfate-free solutions diminished it. The contraluminal35SO
4
2–
influx in sulfate-loaded animals followed two parameter kinetics (K
m 1.4 mmol/l,J
max 1.2 pmol·s–1·cm–1). The contraluminal35SO
4
2–
influx (starting concentration 10 mol/l) did not change when the K+ concentration was varied between 4 and 40 mmol/l and the Ca2+ concentration from zero to 3 mmol/l. Omission of Na+ from the perfusates augmented contraluminal35SO
4
2–
influx markedly. The increase is larger at pH 6 than at pH 7.4. Changes of pH affect contraluminal35SO
4
2–
influx only when the solutions are Na+- and K+-free. Under these conditions the35SO
4
2–
influx decreased when the ambient pH was raised from pH 6.0 to pH 8.0. Thiosulfate, selenate, molybdate, oxalate, phosphate, arsenate, and bicarbonate exerted competitive inhibition, while formate, 2-oxoglutarate and paraaminohippurate showed a biphasic response: inhibition at 50 mmol/l, no inhibition at 150 mmol/l. Chloride and bicarbonate inhibited35SO
4
2–
influx at 10 mol/l35SO
4
2–
, but augmented sulfate influx at 5 mmol/l35SO
4
2–
concentration in rats not preloaded with sulfate. The data indicate the presence of a contraluminal sulfate transport system which is shared by a variety of inorganic and organic anions. The biphasic behaviour of some anions suggests parallel pathways leading to a cis-inhibition at small and trans-stimulation at high anion concentrations. Na+ and H+ may be cotransported or interact with the transport system at a modifier site. 相似文献
104.
C. Lamont T. V. Burdyga S. Wray 《Pflügers Archiv : European journal of physiology》1998,435(4):523-527
Our understanding of the control and effects of intracellular [Na+] ([Na+]i) in intact smooth muscle is limited by the lack of data concerning [Na+]i. The initial aim of this work was therefore to investigate the suitability of using the Na+-sensitive fluorophore SBFI in intact smooth muscle. We find this to be a good method for measuring [Na+]i in ureteric smooth muscle. Resting [Na+]i was found to be around 10 mM and rose to 25 mM when the Na+-K+-ATPase was inhibited by ouabain. This relatively low [Na+]i in the absence of Na+-K+-ATPase suggests that other cellular processes, such as Na+-Ca2+ exchange, play a role in maintaining [Na+]i under these conditions. Simultaneous measurements of [Na+]i or [Ca2+] i and force showed that Na+-Ca2+ exchange can play a functional role in ureteric smooth muscle. We found that the greater the driving force for Na+ exit and hence Ca2+ entry, the larger the contraction. In addition the Na+-Ca2+ exchanger activity under these conditions was found to be pH sensitive: acidification reduced the contraction and concomitant
changes in [Ca2+] and [Na+]i. We conclude that SBFI is a useful method for monitoring [Na] in smooth muscle and that Na+-Ca2+ exchange may play a functional role in the ureter.
Received: 26 August 1997 / Received after revision: 27 October 1997 / Accepted: 28 October 1997 相似文献
105.
Retroviral vectors derived from murine leukemia virus (MLV) have been pseudotyped with a variant of the envelope glycoprotein (Env) of nonpathogenic simian immunodeficiency virus from African green monkeys (SIVagm) to result in [MLV(SIVagm-wt)] vector particles. The variant env gene encodes a full-length surface envelope glycoprotein (SU) and a C-terminally truncated transmembrane protein (TM). To change the coreceptor usage of this vector from CCR5 to CXCR4, which is predominant on human CD4-positive lymphocytes, the putative V3-loop of SIVagm SU was replaced by that of the T cell tropic HIV-1 variant BH10. The resulting [MLV(SIVagm-X4)] vectors were shown to specifically transduce CD4/CXCR4-positive cell lines, demonstrating the equivalent function in cell entry and choice of coreceptor usage of the V3-loops of SIVagm and HIV-1. These modified vectors were able to transduce primary human lymphocytes and were resistant to neutralization by sera from HIV-1-infected individuals. The [MLV(SIVagm-X4)] pseudotype vector generated is thus a promising candidate vector, e.g., for in vivo gene therapy of HIV-1 infection. 相似文献
106.
Armin Kurtz Roberto Della Bruna Holger Scholz Wolfgang Baier 《Pflügers Archiv : European journal of physiology》1991,419(1):32-37
In this study we have examined a potential role of the sodium/proton exchange system in the regulation of renin secretion. We found that the inhibitors of the Na+/H+ antiport, amiloride (1 mM) and ethylisopro-pylamiloride (EIPA, 50 M), led to a 125% increase of renin secretion from cultured mouse juxtaglomerular cells. The stimulatory effect of EIPA on renin secretion was dependent on the extracellular concentrations of sodium and hydrogen ions. While lowering the extracellular pH from 7.3 to 7.0, and lowering [Na+]e from 130 mM to 5 mM had no effect on basal renin release, it markedly attenuated or even blunted the effect of EIPA on renin secretion. The stimulatory effect of forskolin on renin secretion, however, was not altered by decreases of extracellular pH and of sodium. Inhibition of basal renin release was achieved with angiotensin II (1 M). In the presence of EIPA the inhibitory effect angiotensin II was markedly attenuated. Although effective on renin secretion, neither amiloride nor EIPA exerted a significant effect on the de novo synthesis of renin in cultured mouse JG cells. These findings are compatible with the idea that an amiloride-sensitive transport process, presumably the Na+/H+ exchanger, acts indirectly as an inhibitory signal transduction system for renin secretion from renal juxtaglomerular cells. 相似文献
107.
108.
目的探讨奥美拉唑对家兔肾脏IMCD细胞H+/K+交换的影响,以及经洗涤处理是否解除这种影响.方法原代培养家兔肾脏IMCD细胞单层,在100
μmol/L奥美拉唑缓冲液中孵育25 min, 洗涤组则在奥美拉唑缓冲液孵育后,用不含奥美拉唑的缓冲液洗涤IMCD细胞;对照组在不含奥美拉唑的缓冲液孵育25
min;CECF/AM荧光探针法测定各组IMCD细胞H+/K+交换.结果奥美拉唑组的H+/K+交换为(0.016±0.006)
dpHi/min(n=8);与对照组的(0.053±0.008) dpHi/min(n=8)相比,相差非常显著(P<0.001);洗涤组的H+/K+交换为(0.016±0.006)
dpHi/min(n=6),与对照组(n=6)的(0.052±0.009)dpHi/min相比,相差非常显著(P<0.001).结论
100 mol/L的奥美拉唑对家兔IMCD细胞的H+/K+交换有显著影响,而且洗涤处理不能解除这种抑制.因而,肺心病合并上消化道出血患者使用奥美拉唑时,应综合考虑其利弊. 相似文献
109.
Aida Salihagić Marija Mačković Hrvoje Banfić Ivan Sabolić 《Pflügers Archiv : European journal of physiology》1988,413(2):190-196
The effect of unilateral nephrectomy on Na+–H+ exchange in rat renal cortical brush-border membrane vesicles (BBMV) was studied by the method of acridine orange fluorescence quenching. The exchanger activity in BBMV from remnant kidney increased rapidly by 70–75% within first 30 min following uninephrectomy. Only a slight further increase was found in later stages of renal growth, i.e. 30 min to 7 days following uninephrectomy. The changes in antiporter activity were restricted toV
max, whereas theK
m for Na+ was similar in control and compensatory growing kidney. The increase of Na+–H+ exchange at 15 min was not affected by actinomycin D in vivo, whereas the increase at 48 h was completely abolished indicating that protein synthesis could be involved in the late, but not in the initial stimulation of renal Na+–H+ exchange. The late, but not the initial stimulations of Na+–H+ exchange were associated with elevated activities of cortical (Na++K+)-ATPase indicating that changes in antiporter activity precede those in the (Na++K+)-pump. The early stimulation of Na+–H+ exchange in BBMV in one kidney was induced also by the occlusion of blood flow through the contralateral kidney for 15 min, without removing it. Thirty min after the occlusion was removed and the reflow established, the Na+–H+ exchange in BBMV from the intact kidney decreased to the control values. The observed modulations in renal Na+–H+ exchanger may be regulated by phosphorylation-dephosphorylation events. In support, the concentration of a well known protein kinase C activator, 1,2-diacylglycerol, in the cortical tissue of the remnant kidney increased up to 100% within 5 min following unilateral nephrectomy and preceded the increase in Na+–H+ exchange. The early stimulation of Na+–H+ exchange may be a trigger in initiating the kidney growth. 相似文献
110.
The resolving powers of the enforced smoothing and log-normal parametric estimation techniques in recovering ventilation/perfusion
ratio
distributions were evaluated using noisy inert gas elimination data simulated from hypothetical distribution functions representing
various degrees of heterogeneity. The resolving powers were assessed in terms of the statistical recoverabilities of the shunt,
dead space, modality, and modal moments characterizing the perfusion distribution. For all distributions tested, both modal
mean and shunt were estimated by either technique with sufficient accuracies. Modal dispersions (σ) were consistently overestimated
by up to 0.15 decade for narrow distributions, but the mean errors became negligible for σ greater than 0.2 decade. As compared
with the shunt, the dead space estimates were more variable and biased, probably due to their indirect estimation from the
perfusion distribution, which was imperfectly recovered. Both broad unimodal and widely separated bimodal or trimodal distributions
(σ>0.6 decade) were recovered as bimodal distributions of similar forms, so that detection of modality was difficult. The
recoveries by both techniques were comparable in most cases studied, except that parametric estimation generally tended to
be more sensitive to measurement errors and was computationally less efficient. These results provide a useful basis for the
interpretation of
distributions obtained from empirical inert gas data. 相似文献