摘要:

The effects of bradykinin, histamine and serotonin on vascular resistance and microvascular permeability were investigated in isolated cell‐free perfused rabbit lungs. The capillary filtration coefficient was determined from the slope of lung weight changes over periods of venous pressure elevation before application of bradykinin (n=6), histamine (n=6) and serotonin (n=6), and 5, 20 and 50 min afterwards. To prevent rapid inactivation of bradykinin by the angiotensin‐converting enzyme in the pulmonary circulation, the bradykinin effects were additionally studied in the presence of the angiotensin‐converting enzyme inhibitor captopril (n=6). Bolus application of each substance resulted in a short‐lasting increase in the pulmonary vascular resistance (3.7–9.1 mmHg), which was most pronounced in the bradykinin+captopril group. The capillary filtration coefficient was significantly increased after histamine application, and to an even greater extent after serotonin application, whereas bradykinin on its own, as well as bradykinin given in the presence of captopril, had no measurable influence on capillary filtration in the lung. As a result of the first bradykinin challenge, there was an immediate massive generation of prostacyclin, which could not be further augmented by a second application. Histamine injection entailed a delayed onset of prostacyclin generation after the second stimulation, whereas no prostacyclin increase was measured in the serotonin‐treated lungs. Thromboxane A2generation was exclusively observed after the first serotonin application. The data exemplify different pathophysiological characteristics of bradykinin, histamine and serotonin on lung barrier function. Histamine and serotonin induce oedema formation by enhancing microvascular permeability, whereas bradykin

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.549324000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

Gravity has been regarded as the major determinant for local pulmonary perfusion and ventilation. Recent reports, describing major gravity‐independent heterogeneity in both variables, have questioned the importance of gravity. We asked to what extent ventilation and perfusion were related, and if they showed similar distributions along the vertical axis in the lung. We gave99mTc‐aerosols as tracers for ventilation and radioactive microspheres as blood flow tracers in five awake goats over 4 min. Ventilation and perfusion were determined in ∼1.5 cm3pieces of the lung. For both variables the vertical distribution could vary considerably from lung to lung, but within each lung the two distributions were similar. Both ventilation and perfusion were heterogeneously distributed (CV ∼40% for both), they were highly correlated (r=0.81) and the average 25–75‐interpercentile interval for ventilation to perfusion ratio (0.84–1.13) was significantly less wide than for both ventilation (0.76–1.38) and perfusion (0.76–1.40). Some pieces were considerably overventilated while few were correspondingly underventilated. This could indicate that perfusion is adjusted to ventilation in normoxic lungs with a low sensitivity t

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.92355000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

It is well known that theVPO2readjustment rate of the whole body is faster when carrying out a given constant work load starting from a baseline of moderate exercise than from rest. However, it has not been established whether the above change is the result of faster kinetics of the oxidative machinery or, alternatively, the consequence of a reduced involvement of confounding factors such as anaerobic glycolysis or tissue O2stores. The problem, earlier approached by chemical methods, was studied in man by31P‐NMRS assessment of the kinetics of phosphocreatine (PC) hydrolysis at the muscle level which is known to reflect the readjustment rate of the oxidative reactions. Twelve normal subjects carried out in a 90 cm bore modified Picker (1.5 T) magnet, a series of contractions by the plantar flexors reaching pre‐set submaximal loads either in single steps (constant load, CL) or progressively (incremental exercise, I). If preceding exercise (I), compared to rest, influenced the rate of oxidations, the PC concentration at the target loads would be different for the two exercise modes, reflecting different energy deficits. This was not the case. Thus the present results show that the rate of readjustment of oxidations at the muscle level is not affected by priming exercise confirming previous findings and showing that theoretical models ofVPO2control are experimentally applicable to

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.577354000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The ERG ON‐ (b‐wave) and OFF‐response (d‐wave) to differently coloured stimuli was studied using a wide range of stimulus intensities in dark adapted turtle retina. The intensity–response curve of the b‐wave showed saturation but that of the d‐wave, decline in the high‐intensity stimulus range. The curves of the relative spectral sensitivity of the ERG ON‐ and OFF‐response were similar and showed a maximum in the longwave part of the spectrum. GABAergic blockade by 50 μmol L−1picrotoxin caused an increase of the sensitivity, contrast sensitivity and the amplitude range of both ON‐ and OFF‐responses without narrowing of the response dynamic range. In the range of lower stimulus intensities the ON‐responses to blue stimuli and the OFF‐responses to red stimuli were affected to a greater extent. An increased ERG b‐ and d‐wave sensitivity was also observed during glycinergic blockade by 50 μmol L−1strychnine. In the low intensity stimulus range the effect was maximal on the ON‐responses to blue stimuli and on the OFF‐responses to 570 nm stimuli. It was concluded that the GABA‐ and glycinergic systems in the retina equalize rather than make different the relative spectral

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.97359000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The aim of the present work was to investigate the role of GABA and glycine, the two main inhibitory neurotransmitters in the retina, in the spectral sensitivity coding under conditions of light adaptation. To study this question, spectral sensitivity curves, based on the turtle ERG responses to stimuli of different wavelengths, were constructed. The spectral sensitivity curves, obtained before and during treatment with picrotoxin (PT), a GABAAantagonist, or with strychnine (ST), a glycine antagonist, were compared. Both PT and ST increased the b‐ and d‐wave absolute sensitivity in a wavelength‐dependent manner. PT significantly changed the shape of the b‐ and d‐wave spectral sensitivity curves and the latter lost their peaks.It is concluded that, under conditions of light adaptation, GABA and glycine took part in the formation of the b‐ and d‐wave spectral sensitivity curves, that both of them exerted an effect on the gain and that, furthermore, GABA had a well pronounced effect on the tuning of the spectral sensi

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.596346000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The effects of exercise on the generation of active oxygen species and radical‐scavenging capacity were studied in physically active and sedentary young and old rats. Exercise increased the hydroxyl radical content in all tissues of physically active young rats, except in the plasma. In old rats, the basal level of the radical increased significantly in plasma, heart, and skeletal muscles, but decreased in liver; and physical activity decreased it to that of young rats in most cases. With exercise, the content of reduced glutathione increased in plasma, heart, and skeletal muscles of young rats, whereas that of oxidized glutathione markedly decreased in liver and increased in brain and white gastrocnemius muscle. The total glutathione levels in these tissues changed in a similar way, indicating that glutathione was released from the pool in the liver. In rats allowed to run voluntarily for 5 weeks, the effects were more pronounced than in the sedentary rats. The ratio of reduced to total glutathione, which indicates the capacity to reduce glutathione, increased in plasma, heart, and soleus muscle of sedentary young rats after exercise, and increased further in those undergoing physical activity. In old rats, the reduced glutathione level increased in plasma, heart, liver, and brain, even though the total decreased. These results suggest that physical activity enhances the endogenous ability to defend against oxidative stress. In old rats, even though glutathione synthesis is decreased, the regenerating capacity seems to be increased in order to compensate for the increased oxidative stres

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.576351000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The aim of the present study was to investigate the concentration effect of adenosine on unstimulated platelet aggregation in humans. Adenosine infusion was given intravenously to 12 volunteers in the antecubital vein with infusion rates increasing from 20 to 100 μg kg−1min−1. Filtragometry measurements were obtained from the contralateral antecubital vein before and during 100 μg kg−1min−1or during maximal tolerable infusion rate. In another set of experiments with 10 volunteers, basal filtragometry measurements were obtained before and after infusion of various concentrations of adenosine into the filtragometer test unit. With intravenous infusion aggregation time tended to increase from 333±42 to 418±8 s (mean±SEM) and increased the venous plasma adenosine concentration from 0.42±0.09 μMto 1.52±0.38 μM. Adenosine infusion into the filtragometer tubing system dose‐dependently inhibited aggregation (P<0.05). Adenosine was rapidly eliminated with a half‐life of adenosine in the filtragometry tubing system calculated to be about 6 s. These data extend our knowledge from anin vitroto anex vivosituation that adenosine dose‐dependently has a platelet

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.108356000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

Ear lobe blood pHa,PaCO2,PaO2, and O2saturation (SaO2) were measured in healthy Caucasians and Sherpas at 3400 m (Namche Bazaar, Nepal,n=4/5), 5050 m (Pyramid Laboratory, Lobuche, Nepal,n=20/5) and 6450 m (Camp II of Mt Everest,n=11/7). In the investigated altitude range, pHaincreased progressively with altitude from 7.463±0.005 (mean±SE) to 7.496±0.006 in Caucasians whereas it remained essentially constant (7.45–7.46) in Sherpas. At all altitudes,PaCO2was higher in Sherpas than in Caucasians (P<0.02). By contrast,PaO2and SaO2were the same in Caucasians and Sherpas at all investigated altitudes. Moreover, in Caucasians sojourning for 3 weeks at 5050 m,PaCO2kept decreasing whereas pHa,PaO2and SaO2remained constant. These data suggest that: (1) respiratory alkalosis was a common finding both in Caucasians and Sherpas; (2) at 6450 m, Sherpas were less alkalotic due to higherPaCO2than Caucasians, possibly a consequence of a blunted ventilatory response; (3) at 6450 m, SaO2andPaO2were the same in Caucasians and Sherpas despite differentPaCO2values. The latter finding could be the consequence of one or more of the following adjustments in Sherpas: (1), an increased efficiency of alveolar O2transfer, i.e. smaller alveolar‐arterial O2gradient; (2) a decreased (arterial – mixed venous) O2difference, possibly due to increased cardiac output; (3) a reduced increase of the [2,3‐DPG]/[Hb]ratio; but not (4) an elevated gas exchange ratio (R). It is concluded that both physiological and biochemical variables contribute to optimize the O2transport at altitude. Apparently a more efficient adaptation to hypoxia allows Sherpas to limit alkalosis through a lower ventilatory drive and to maintain SaO2at the samePaO2by decreasing the [2,3‐DP

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.574342000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

Brain natriuretic peptide (BNP) messenger RNA was measured with a semiquantitative method from heart auricles and ventricles of vasopressin‐deficient Brattleboro rats (DI) and from desmopressin treated Brattleboro rats (DI+DDAVP). Desmopressin had been injected peripherally and Long‐Evans rats (LE) served as controls. The 3‐day substitution treatment had shifted the fluid balance of DI almost to that of LE. In the present study, the amount of BNP mRNA, normalized to the glyceraldehyde‐3‐phosphate‐dehydrogenase mRNA content, was constant in all three groups in the right auricle. No changes were seen when the right auricular and left auricular mRNA levels were compared within each group. In the left auricle, desmopressin treatment increased significantly (P<0.05) the amount of BNP mRNA compared with that of LE rats (from 1.09±0.21,n=7 to 1.72±0.17,n=8, arbitrary units). In all groups, the left ventricle had significantly (P<0.05) higher mRNA content than the right ventricle (LE: 2.24±0.23 vs. 0.67±0.13,n=6; DI: 2.30±0.60 vs. 0.33±0.05,n=8; DI+DDAVP: 2.36±0.29 vs. 0.37±0.07,n=10). In the right ventricle, both DI and DI+DDAVP rats had significantly (P<0.05) lower mRNA content than LE rats (0.33±0.5 vs. 0.67±0.13 and 0.37±0.07 vs. 0.67±0.13, respectively).To conclude, these findings suggest that brain natriuretic peptide gene expression dissociates from, or rapidly adapts to, the chronic effects of peripheral desmopressin treatment which have shifted the fluid balance to almost normal in Brattleboro rats. The left ventricular pressure appears to regulate the brain natriuretic

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.590349000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.123358000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY