Showing papers in "Clinical Science in 1999"
TL;DR: Evidence from human studies that glucocorticoids make an important contribution to the pathophysiology of insulin resistance in the population is described.
Abstract: Insulin resistance has been proposed as a mediator of the association between risk factors for cardiovascular disease in the population. The clinical syndrome of glucocorticoid excess (Cushing's syndrome) is associated with glucose intolerance, obesity and hypertension. By opposing the actions of insulin, glucocorticoids could contribute to insulin resistance and its association with other cardiovascular risk factors. In this review, we describe briefly the known mechanisms of insulin resistance and highlight the potential mechanisms for the effect of glucocorticoids. We then discuss factors which modulate the influence of glucocorticoids on insulin sensitivity; this highlights a novel therapeutic strategy to manipulate glucocorticoid action which may prove to be a useful tool in treating subjects with insulin resistance. Finally, we describe evidence from human studies that glucocorticoids make an important contribution to the pathophysiology of insulin resistance in the population.
694 citations
TL;DR: Due to orthostasis, changes in the aortic transmural pressure may lead to an offset in MFSV from IAP, however, Modelflow correctly calculated aortsic flow from non-invasively determined finger pressure during orthostatic stress.
Abstract: The relationship between aortic flow and pressure is described by a three-element model of the arterial input impedance, including continuous correction for variations in the diameter and the compliance of the aorta (Modelflow). We computed the aortic flow from arterial pressure by this model, and evaluated whether, under orthostatic stress, flow may be derived from both an invasive and a non-invasive determination of arterial pressure. In 10 young adults, Modelflow stroke volume (MFSV) was computed from both intra-brachial arterial pressure (IAP) and non-invasive finger pressure (FINAP) measurements. For comparison, a computer-controlled series of four thermodilution estimates (thermodilution-determined stroke volume; TDSV) were averaged for the following positions: supine, standing, head-down tilt at 20°(HDT20) and head-up tilt at 30°and 70°(HUT30 and HUT70 respectively). Data from one subject were discarded due to malfunctioning thermodilution injections. A total of 155 recordings from 160 series were available for comparison. The supine TDSV of 113 ± 13 ml (mean ± S.D.) dropped by 40% to 68 ± 14 ml during standing, by 24% to 86 ± 12 ml during HUT30, and by 51% to 55 ± 15 ml during HUT70. During HDT20, TDSV was 114 ± 13 ml. MFSV for IAP underestimated TDSV during HDT20 (-6 ± 6 ml; P < 0.05), but that for FINAP did not (-4 ± 7 ml; not significant). For HUT70 and standing, MFSV for IAP overestimated TDSV by 11 ± 10 ml (HUT70; P < 0.01) and 12 ± 9 ml (standing; P < 0.01). However, the offset of MFSV for FINAP was not significant for either HUT70 (3 ± 8 ml) or standing (3 ± 9 ml). In conclusion, due to orthostasis, changes in the aortic transmural pressure may lead to an offset in MFSV from IAP. However, Modelflow correctly calculated aortic flow from non-invasively determined finger pressure during orthostasis.
346 citations
TL;DR: While the primary mechanisms of the myogenic response are well understood, the details of the signalling pathways are still undefined and it is suggested that the clinical significance of theMyogenic response remains to be determined.
Abstract: The myogenic response of small arteries and arterioles has been shown to contribute significantly to autoregulation in different vascular beds. It is characterized by a constriction of the vessel after an increase of transmural pressure and a dilation of the vessel after a decrease of transmural pressure. This review examines the evidence for the mechanisms of the myogenic response, with the aim of distinguishing between facts and hypotheses. It appears to be established that the myogenic response is stimulated by an alteration of vessel wall tension, that it does not require the presence of the endothelium and, for pressure increases, that it is accompanied by a membrane depolarization and an increase of the intracellular Ca2+ concentration, which depends largely on an influx of extracellular calcium via voltage-operated calcium channels. Under in vitro conditions, it may further be considered an established fact that the myogenic response can be modulated by transmitters, like noradrenaline, and factors released from the endothelium upon its activation. In contrast, many other aspects of the myogenic response remain hypothetical. Thus, the mechanism of the depolarization, its importance for the development of the myogenic response, the participation of other pathways for calcium influx, and the role of an intracellular calcium release in the myogenic response are still under debate. Furthermore, the participation of a variety of intracellular second messenger systems in the myogenic response, i.e. inositol trisphosphate, diacylglycerol, phospholipase A2, protein kinase C or 20-hydroxyeicosatetraenoic acid, is still unclear. Additionally, the roles of the pulsatility of the blood pressure and of remote signals from neighbouring vessel segments as well as of different metabolites are not clarified. This review suggests that while the primary mechanisms of the myogenic response are well understood, the details of the signalling pathways are still undefined. The clinical significance of the myogenic response remains to be determined.
284 citations
TL;DR: High levels of high-density lipoprotein in plasma may offer additional protection by inhibiting low-densitylipoprotein oxidation and thus liposoluble antioxidant consumption, and soccer players under regular training show an improved plasma antioxidant status in comparison to sedentary controls.
Abstract: Physical activity is known to induce oxidative stress in individuals subjected to intense exercise. In this study, we investigated the lipoprotein profile and the plasma antioxidant status in a group of soccer players engaged in a regular training programme. As was expected for aerobic exercise, high-density lipoprotein-cholesterol (HDL-C) and HDL3-C levels were significantly increased in the sportsmen (P<0.05). Total plasma antioxidant capacity was 25% higher in sportsmen than in controls (P<0.005). Accordingly, plasma hydrosoluble antioxidant levels (ascorbic acid and uric acid) were found to be significantly elevated in the soccer players (P<0.005). In addition, these subjects showed high concentrations of alpha-tocopherol in plasma compared with controls (P<0.005). Furthermore, an increase in plasma superoxide dismutase activity was also observed in relation to exercise (P<0.01). The elevation in plasma activities of antioxidant enzymes and the higher levels of free radical scavengers of low molecular mass may compensate the oxidative stress caused by physical activity. High levels of high-density lipoprotein in plasma may offer additional protection by inhibiting low-density lipoprotein oxidation and thus liposoluble antioxidant consumption. Therefore, soccer players under regular training show an improved plasma antioxidant status in comparison to sedentary controls.
170 citations
TL;DR: Those subjects who were weakest at enrolment showed the greatest increases in muscle strength after treatment, in agreement with previous studies, and there was no correlation between the individual increases in bone mineral density and those in MVF.
Abstract: A randomized open trial of hormone replacement therapy was used to assess changes in adductor pollicis muscle strength during 6-12 months of treatment with Prempak C 0.625(R) in comparison with an untreated control group. Muscle strength (maximal voluntary force; MVF), muscle cross-sectional area and bone mineral density were measured. Women entering the trial had oestrogen levels below 150 pmol.l-1, confirming their post-menopausal hormonal status. In the treated group, MVF increased by 12.4+/-1.0% (mean+/-S.E.M.) of initial MVF over the duration of treatment, while it declined slightly (2.9+/-0.9%) in the control group. This increase in strength could not be explained by an increase in muscle bulk, there being no significant increase in cross-sectional area during the study. Those subjects who were weakest at enrolment showed the greatest increases in muscle strength after treatment. Bone mineral density in total hip, Ward's triangle and total spine increased in the treated group, in agreement with previous studies. There was no correlation between the individual increases in bone mineral density and those in MVF.
165 citations
TL;DR: The results suggest that in humans a methionine-rich diet may acutely impair endothelial function, which can be prevented by folic acid supplementation.
Abstract: Recent evidence demonstrates that hyperhomocyst(e)inaemia is a novel risk factor for cardiovascular diseases. In patients with chronic hyperhomocyst(e)inaemia, endothelial function is impaired. However, whether hyperhomocyst(e)inaemia per se is a cause or an epiphenomenon of endothelial dysfunction remains unknown. In this study, we examined the effects of methionine-induced acute hyperhomocyst(e)inaemia on human endothelial function. In healthy volunteers we administered methionine (0.1 g/kg body weight, per os), a substrate of homocyst(e)ine, with or without folic acid (20 mg, per os) and examined flow-mediated vasodilatation of the brachial artery by high-resolution ultrasonography as a non-invasive measure of endothelial function. We also measured plasma levels of homocyst(e)ine before and 3, 8 and 24 h after methionine loading. Methionine administration increased plasma levels of homocyst(e)ine by four times the basal level at 8 h (P<0.0001, ANOVA). The plasma levels returned to baseline at 24 h. Flow-mediated vasodilatation was significantly decreased to half of the baseline value at 8 h and returned to baseline at 24 h (P<0.0001, ANOVA), whereas endothelium-independent vasodilatation by glyceryl trinitrate was not affected by the methionine loading. Co-administration of folic acid did not attenuate methionine-induced hyperhomocyst(e)inaemia but completely prevented endothelial dysfunction. Our results suggest that in humans a methionine-rich diet may acutely impair endothelial function, which can be prevented by folic acid supplementation.
158 citations
TL;DR: Evidence suggests that the gaseous molecule nitric oxide (NO) modulates cardiac vagal control, increasing the activity of central vagal motoneurons and, more contentiously, contributing to the bradycardic effects of vagal stimulation.
Abstract: Alteration in function of the cardiac autonomic nervous system has proved to be a powerful predictor of cardiac death or serious arrhythmia in patients with cardiac disease, yet little is known about the mechanisms by which this system is regulated. Recent evidence suggests that the gaseous molecule nitric oxide (NO) may act as an important mediator in this pathway. Histochemical staining techniques have identified neuronal populations that contain NO synthase within medullary cardio-regulatory sites and their peripheral autonomic pathways. Drugs that modulate the NO pathway (administered both systemically and into the central nervous system) cause changes in pre- and post-ganglionic sympathetic nerve activity that imply that NO serves to inhibit central sympathetic outflow. There is also evidence that NO may attenuate cardiovascular end-organ responses to sympathetic stimulation. Studies suggest that NO modulates cardiac vagal control, increasing the activity of central vagal motoneurons and, more contentiously, contributing to the bradycardic effects of vagal stimulation. NO also modulates so-called 'indirect' vagal inhibition of sympathetic cardiac responses. Additionally, central attenuation of baroreflex-mediated vagal control has been described. There is relatively little information available on the importance of NO in the regulation of human cardiovascular autonomic control. Further well-controlled studies are required.
151 citations
TL;DR: In human lung cancer, weight loss and the presence of a low BCM are associated with systemic inflammation, an increased acute-phase response and decreased levels of IGF-I, and a decreased BCM is associated with hypermetabolism.
Abstract: The aim of the present study was to investigate, in human lung cancer, the relationship between weight loss and the existence of a low body cell mass (BCM) on the one hand, and the putative presence of systemic inflammation, an increased acute-phase response, anorexia, hypermetabolism and changes in circulating levels of several anabolic and catabolic hormones on the other. In 20 male lung cancer patients, pre-stratified by weight loss of >/=10% (n=10) or of /=10% were characterized by higher levels of sTNF-R55 (trend towards significance; P=0.06), and lower levels of albumin (27.4 compared with 34.4 mmol/l; P=0.02), testosterone (13.2 compared with 21.5 nmol/l; P=0.01) and IGF-I (119 compared with 184 ng/ml; P=0.004). In the patient group as a whole, the percentage weight loss was significantly correlated with sTNF-R55 (r=0.59, P=0.02), albumin (r=-0.63, P=0.006) and IGF-I (r=-0.50, P=0.02) levels. Height-adjusted BCM was significantly correlated with sTNF-R55 (r=-0.57, P=0.03), sTNF-R75 (r=-0.50, P=0. 04), lipopolysaccharide-binding protein (r=-0.50, P=0.04), albumin (r=0.56, P=0.02) and resting energy expenditure/BCM (r=-0.54, P=0. 03), and there was a trend towards a correlation with IGF-I concentration (r=0.44, P=0.06). We conclude that, in human lung cancer, weight loss and the presence of a low BCM are associated with systemic inflammation, an increased acute-phase response and decreased levels of IGF-I. In addition, a decreased BCM is associated with hypermetabolism.
139 citations
TL;DR: An atherogenic lipid profile develops during normal gestation, and the significance of these changes remains unclear, but they may have important implications for mother and foetus.
Abstract: Serum cholesterol, triacylglycerols and low-density lipoprotein (LDL) subfractions were determined in 120 primagravid women during normal gestation (40 in each trimester) and in 20 non-pregnant age-matched controls LDL subfractions were determined by PAGE, and an LDL score was calculated The higher the score, the smaller the subfractions The objective of the study was to determine the effects of the hyperlipidaemia, high oestrogen concentrations and insulin resistance known to exist in normal pregnancy on LDL subfraction formation Pregnant women had an increased mean serum cholesterol concentration [578 (SD 109) mmol/l] in the first trimester compared with the non-pregnant controls [511 (077) mmol/l; P<001] The serum cholesterol concentration increased progressively throughout gestation to a mean of 814 (139) mmol/l in the third trimester (P<0001 compared with the second trimester) Triacylglycerol concentrations in the first trimester were similar to those of controls, and there was a non-significant increase by the second trimester to 132 (044) mmol/l However, by the third trimester the mean triacylglycerol concentration had doubled [258 (098) mmol/l; P<0001 compared with the first and second trimester] During gestation the LDL score increased dramatically, from 117 (039) during the first trimester to 201 (037) in the second trimester (P<0001) to 273 (048) in the third trimester (P<0001 compared with the second trimester) Thus an atherogenic lipid profile develops during normal gestation The significance of these changes remains unclear, but thay may have important implications for mother and foetus
135 citations
TL;DR: It is concluded that respiratory PR variability does not precisely reflect respiratory HR variability in standing healthy subjects and in patients with low HR variability, and HR modulation should be studied using the ECG signal rather than the distal pulse wave signal.
Abstract: To investigate the differences between heart rate (HR) variability and pulse rate (PR) variability, short-term variability of finger pulse wave and ECG signals were studied in 10 children with a fixed ventricular pacemaker rhythm (80 beats/min). Ten healthy children in sinus rhythm served as a reference population. Distal PR and HR were measured continuously using a Finapres device and an ECG respectively. Power spectra for HR and PR were calculated in both the supine and orthostatic positions. In paced subjects, PR spectra exhibited the characteristic respiratory peak, although the HR spectra were flat. Similarly, in healthy children the respiratory fluctuations were more pronounced when calculated from the finger pulse wave signal compared with the ECG signal. The overestimation of HR respiratory fluctuation resulting from distal PR measurement was more pronounced in the standing position; however, this postural effect was demonstrated only in healthy subjects. We observed mechanical respiratory modulation of distal PR independent of classical HR modulations. Our results suggest a mechanical respiratory influence via cardiac output and aortic transmural pressure changes on pulse wave velocity. We conclude that respiratory PR variability does not precisely reflect respiratory HR variability in standing healthy subjects and in patients with low HR variability. Consequently, HR modulation should be studied using the ECG signal rather than the distal pulse wave signal. However, when ECG recording is not available, the distal pulse wave is an acceptable alternative.
133 citations
TL;DR: While HRT preserved muscle strength, there was no evidence of a strengthening effect on skeletal muscle within this short period of treatment, suggesting HRT may offer protection against muscle weakness, although the hormone responsible for regulating strength is not evident using this model.
Abstract: The effects of hormone deficiency at the menopause on muscle strength was examined in 10 healthy middle-aged women (1-3 years post-menopause) in a longitudinal trial over 39 weeks. Performance was compared with that of age-matched females (n=11) taking a course of hormone replacement therapy (HRT). Muscle strength of the quadriceps was measured isometrically at 90 degrees of knee flexion and at angular velocities of 1.05, 2.09 and 3.13 rad/s using an isokinetic dynamometer. Hand grip strength was assessed by means of a portable dynamometer. Measurements were taken every 13 weeks for 39 weeks. Significant decreases in isometric strength (-10%) and dynamic leg strength at 1.05 rad/s (-9%) were found in the post-menopausal women over 39 weeks. There was no change in strength in the HRT group. There were also no changes in leg strength at higher angular velocities or in grip strength for either the post-menopausal group or those taking HRT. While HRT preserved muscle strength, there was no evidence of a strengthening effect on skeletal muscle within this short period of treatment. A rapid loss of leg strength occurs post-menopausally in hormone-depleted women. HRT may offer protection against muscle weakness, although the hormone responsible for regulating strength is not evident using this model.
TL;DR: The tight junctions between cerebral microvessel endothelial cells appeared morphologically intact in both septic and sham pigs, and may be sufficient to underlie the clinical features seen in septic encephalopathy.
Abstract: Encephalopathy is a common complication of sepsis. However, little is known about the morphological changes that occur in the brain during sepsis. Faecal peritonitis was induced in pigs that were killed 8 h later and frontal cortex samples were taken immediately after death. The tissue was investigated using light and electron microscopy and compared with frontal cortex samples taken from sham-operated controls. Septic pigs had 49.5% more perimicrovessel oedema than sham pigs. However, the tight junctions between cerebral microvessel endothelial cells appeared morphologically intact in both septic and sham pigs. Sepsis also resulted in neuronal injury, disruption of astrocytic end-feet and swollen, rounded erythrocytes. These morphological changes may be sufficient to underlie the clinical features seen in septic encephalopathy.
TL;DR: Of the four techniques assessed for measuring BRS, the controlled breathing time-domain method yielded the best reproducibility and lowest failure rate in controls and in patients with chronic heart failure.
Abstract: Baroreflex sensitivity (BRS) conveys useful prognostic information in patients with heart disease, yet methods for its quantification suffer from poor reproducibility and test failure in some patients with heart failure. We set out to compare the short-term reproducibility and success rate of four different methods of assessing BRS in normal subjects and patients with chronic heart failure (CHF). A total of 31 patients with CHF and 18 normal controls underwent BRS testing using four techniques: (1) bolus phenylephrine (BRS(Phe)), (2) alpha-index in both low- and high-frequency bands (BRS(alphaLF) and BRS(alphaHF) respectively), (3) the sequence method (BRS(Seq)), and (4) a new 0.1 Hz controlled-breathing, time-domain analysis method (BRS(Cbr)). Each subject underwent two test episodes with each method on the same day. The average values for BRS in patients and controls respectively were: BRS(Phe), 4.4 (+/-4.4) ms/mmHg and 19.8 (+/-11.5) ms/mmHg; BRS(alphaLF), 5.6 (+/-4.1) ms/mmHg and 15.4 (+/-5.0) ms/mmHg; BRS(alphaHF), 7.1 (+/-7.0) ms/mmHg and 25.1 (+/-8.3) ms/mmHg; BRS(Seq), 7.7 (+/-6.3) ms/mmHg and 22.5 (+/-8.4) ms/mmHg; BRS(Cbr), 6.6 (+/-5.9) ms/mmHg and 22.8 (+/-10.8) ms/mmHg. The coefficients of variation (S.D. of the difference in repeated values divided by mean) in patients and controls respectively were: BRS(Phe), 85.6% and 52.2%; BRS(alphaLF), 65.9% and 33.7%; BRS(alphaHF), 99.7% and 52. 1%; BRS(Seq), 30.7% and 40.4%; BRS(Cbr), 30.7% and 19.6%. The numbers of test failures in patients were: BRS(Phen), 15; BRS(alphaLF), 7; BRS(alphaHF), 5; BRS(Seq), 14; BRS(Cbr), 1. Of the four techniques assessed for measuring BRS, the controlled breathing time-domain method yielded the best reproducibility and lowest failure rate in controls and in patients with CHF.
TL;DR: Heavy exercise and high levels of adrenaline reversibly increased platelet aggregability and platelet sensitivity to thrombin, and enhancedThrombin formation; the effects were most pronounced during exercise.
Abstract: Stress-induced activation of haemostasis may be involved in the triggering of acute coronary syndromes. We compared the eects of mental stress, dynamic exercise and adrenaline infusion on platelet sensitivity to thrombin using flow-cytometric analysis of platelet fibrinogen binding in whole blood, and platelet aggregability using filtragometry ex vivo, in healthy volunteers. Furthermore, we assessed thrombin generation [prothrombin fragment 1›2 (F1›2) and thrombin‐antithrombin complexes in plasma] and thrombin activity (fibrinopeptide A in plasma). Exercise (bicycle ergometry) enhanced thrombin-induced platelet fibrinogen binding (P ! 0.05) and platelet aggregability (P ! 0.01), and elevated F1›2, thrombin‐antithrombin complexes and fibrinopeptide A (P ! 0.05 for all three). Adrenaline infusion enhanced thrombin-induced platelet fibrinogen binding and platelet aggregability (P ! 0.05), and elevated thrombin‐antithrombin complexes (P ! 0.05), whereas F1›2 and fibrinopeptide A levels were not significantly aected. Mental stress increased platelet sensitivity to high concentrations of thrombin only, and produced small increases in levels of thrombin‐antithrombin complexes. Time control experiments showed no important changes with repeated measurements during rest. Platelet responses to exercise and adrenaline were reversible, with recovery 60 min later. Thus, heavy exercise and high levels of adrenaline reversibly increased platelet aggregability and platelet sensitivity to thrombin, and enhanced thrombin formation; the eects were most pronounced during exercise. Mental stress only weakly aected these parameters.
TL;DR: It is concluded that contractile dysfunction is present in cirrhosis and is aggravated by a sodium load; an increased pre-load in the pre-ascitic patients compensates for the cardiac dysfunction; and in ascitic patients, a reduced afterload, manifested as systemic arterial vasodilatation, compensating for a reduced pre- load and contractiles dysfunction.
Abstract: The aim of this study was to assess the relationship between subtle cardiovascular abnormalities and abnormal sodium handling in cirrhosis. A total of 35 biopsy-proven patients with cirrhosis with or without ascites and 14 age-matched controls underwent two-dimensional echocardiography and radionuclide angiography for assessment of cardiac volumes, structural changes and systolic and diastolic functions under strict metabolic conditions of a sodium intake of 22 mmol/day. Cardiac output, systemic vascular resistance and pressure/volume relationship (an index of cardiac contractility) were calculated. Eight controls and 14 patients with non-ascitic cirrhosis underwent repeat volume measurements and the pressure/volume relationship was re-evaluated after consuming a diet containing 200 mmol of sodium/day for 7 days. Ascitic cirrhotic patients had significant reductions in (i) cardiac pre-load (end diastolic volume 106+/-9 ml; P<0.05 compared with controls), due to relatively thicker left ventricular wall and septum (P<0.05); (ii) afterload (systemic vascular resistance 992+/-84 dyn.s.cm(-5); P<0. 05 compared with controls) due to systemic arterial vasodilatation; and (iii) reversal of the pressure/volume relationship, indicating contractility dysfunction. Increased cardiac output (6.12+/-0.45 litres/min; P<0.05 compared with controls) was due to a significantly increased heart rate. Pre-ascitic cirrhotic patients had contractile dysfunction, which was accentuated when challenged with a dietary sodium load, associated with renal sodium retention (urinary sodium excretion 162+/-12 mmol/day, compared with 197+/-12 mmol/day in controls; P<0.05). Cardiac output was maintained, since the pre-load was normal or increased, despite a mild degree of ventricular thickening, indicating some diastolic dysfunction. We conclude that: (i) contractile dysfunction is present in cirrhosis and is aggravated by a sodium load; (ii) an increased pre-load in the pre-ascitic patients compensates for the cardiac dysfunction; and (iii) in ascitic patients, a reduced afterload, manifested as systemic arterial vasodilatation, compensates for a reduced pre-load and contractile dysfunction. Cirrhotic cardiomyopathy may well play a pathogenic role in the complications of cirrhosis.
TL;DR: Despite evidence of inflammation in this study, muscle antioxidant status was not compromised, and malondialdehyde was unaltered in muscle and plasma, and this study provides no evidence that chronic muscle inflammation compromises antioxidant status or increases lipid peroxidation.
Abstract: This study investigated the effects of chronic muscle inflammation on indices of antioxidant status and muscle injury after eccentric exercise. Eight subjects each performed 70 maximal voluntary eccentric muscle actions on an isokinetic dynamometer, using the knee extensors of a single leg. Venous blood samples were collected into serum and EDTA tubes 5 and 3 days before exercise, immediately before exercise, and then again on days 3, 4, 5, 6, 7, 10 and 12 after the bout. Needle biopsies were taken from the vastus lateralis of six subjects, a week before exercise (baseline), and again on days 4 and 7 post-exercise. The concentrations of malondialdehyde in plasma and muscle were used as markers of lipid peroxidation. Creatine kinase activity, beta-glucuronidase activity and total antioxidant capacity were determined in serum. In muscle, aqueous and bound total antioxidant capacity, the aqueous sulphydryl concentration, and beta-glucuronidase and glucose-6-phosphate dehydrogenase activity were determined. No changes were detected in serum total antioxidant capacity, serum creatine kinase and beta-glucuronidase after the baseline biopsy. After exercise serum creatine kinase and beta-glucuronidase were elevated although other serum measures were unchanged. In muscle, aqueous and bound total antioxidant capacity, sulphydryls, glucose-6-phosphate dehydrogenase and beta-glucuronidase were all elevated. Despite evidence of inflammation in this study, muscle antioxidant status was not compromised, and malondialdehyde was unaltered in muscle and plasma. Therefore, this study provides no evidence that chronic muscle inflammation compromises antioxidant status or increases lipid peroxidation.
TL;DR: Sheep fetuses exposed to dexamethasone for only 2 days at the end of the first month of gestation have high blood pressure (dependent upon the increase in cardiac output) and a reset of the baroreflex at 40 months of age.
Abstract: Numerous epidemiological studies, together with mounting evidence from studies in animals, point to a correlation between an adverse intrauterine environment and the early onset of cardiovascular and metabolic diseases later in life. We were the first to show that sheep exposed to dexamethasone (0.28 mg.kg-1.day-1 for only 2 days) at the end of the first month of pregnancy (PTG1), but not those exposed at the end of the second month of pregnancy (PTG2), had a higher basal mean arterial pressure (MAP) 19 months after birth. In the present study we report the MAP, cardiovascular haemodynamics and baroreflex sensitivity in these animals at 40 months of age. MAP in the PTG1 group was significantly higher than in the control group (91+/-1 mmHg and 81+/-1 mmHg respectively; P<0.001) and also when compared with the PTG2 group (82+/-1 mmHg; P<0.001). There was a significant increase in cardiac output in the PTG1 group compared with the control group (108+/-2 and 96+/-4 ml.min-1.kg-1 respectively; P<0.05). The increase in cardiac output in the PTG1 group was due to an increase in stroke volume (1.82+/-0.08 ml.kg-1. beat-1, compared with 1.46+/-0.06 ml.kg-1.beat-1 in the control group; P<0.05), but not in heart rate. In the hypertensive group of animals (PTG1), there was a rightward shift of the baroreflex curve. In group PTG2 (the normotensive group of animals), a lower gain was found before and during propranolol treatment. The decrease in gain of the baroreflex was not associated with changes in heart rate range, suggesting an impairment in the central processing of the baroreceptor signals. Thus sheep fetuses exposed to dexamethasone for only 2 days at the end of the first month of gestation have high blood pressure (dependent upon the increase in cardiac output) and a reset of the baroreflex at 40 months of age. Animals that have received prenatal dexamethasone closer to mid-gestation, although normotensive with normal cardiac output, showed an altered baroreceptor-heart rate response.
TL;DR: It is suggested that the fundamental BIA method has advantages over anthropometry for measuring lower limb tissue composition in healthy individuals.
Abstract: Magnetic resonance imaging (MRI) was used to evaluate and compare with anthropometry a fundamental bioelectrical impedance analysis (BIA) method for predicting muscle and adipose tissue composition in the lower limb. Healthy volunteers (eight men and eight women), aged 41 to 62 years, with mean (S.D.) body mass indices of 28.6 (5.4) kg/m2 and 25.1 (5.4) kg/m2 respectively, were subjected to MRI leg scans, from which 20-cm sections of thigh and 10-cm sections of lower leg (calf) were analysed for muscle and adipose tissue content, using specifically developed software. Muscle and adipose tissue were also predicted from anthropometric measurements of circumferences and skinfold thicknesses, and by use of fundamental BIA equations involving section impedance at 50 kHz and tissue-specific resistivities. Anthropometric assessments of circumferences, cross-sectional areas and volumes for total constituent tissues matched closely MRI estimates. Muscle volume was substantially overestimated (bias: thigh, -40%; calf, -18%) and adipose tissue underestimated (bias: thigh, 43%; calf, 8%) by anthropometry, in contrast to generally better predictions by the fundamental BIA approach for muscle (bias: thigh, -12%; calf, 5%) and adipose tissue (bias: thigh, 17%; calf, -28%). However, both methods demonstrated considerable individual variability (95% limits of agreement 20-77%). In general, there was similar reproducibility for anthropometric and fundamental BIA methods in the thigh (inter-observer residual coefficient of variation for muscle 3.5% versus 3.8%), but the latter was better in the calf (inter-observer residual coefficient of variation for muscle 8.2% versus 4.5%). This study suggests that the fundamental BIA method has advantages over anthropometry for measuring lower limb tissue composition in healthy individuals.
TL;DR: The expression of V EGF within normal glomeruli is complex and variable, with inter- and intra-individual variation, suggesting that, in healthy individuals, a degree of VEGF autoregulation is the norm.
Abstract: Vascular endothelial growth factor (VEGF) mediates increased vascular permeability and endothelial mitogenesis, and may orchestrate normal glomerular permselectivity and proteinuria. Distinct isoforms result from dierential gene splicing. VEGF binds to two cell surface tyrosine-kinase receptors, KDR (kinase domain region) and Flt-1 (fms-like tyrosine kinase-1). The latter also exists in a soluble form (sFlt), which is inhibitory. We have studied patterns of VEGF-isoform and VEGF-receptor expression in isolated single normal human glomeruli. mRNA from 190 glomeruli (from 20 individuals) was harvested on to magnetic beads, and nested reverse transcription‐PCR was performed using primers for the VEGF isoforms and VEGF receptors. Simultaneous nested reverse transcription‐PCR for CD45 was conducted in order to exclude leucocyte contamination. Unexpected products were isolated, cloned and sequenced. Multiple patterns of glomerular VEGF mRNA isoform expression were identified. Most frequently (58%), all three common forms were expressed. VEGF189 (i.e. 189-amino-acid form of VEGF) was expressed in 63%, VEGF165 in 85% and VEGF121 in 84% of glomeruli. Two unexpected PCR products were also identified: 18% of glomeruli expressed VEGF145, and 27% of glomeruli expressed a new truncated VEGF splice variant, VEGF148, lacking exon 6, the terminal part of exon 7 and exon 8. Multiple patterns of VEGF-receptor expression were also identified, the most common being expression of all three isoforms (28%). Overall, KDR was seen in 59% of glomeruli, Flt-1 in 45% and sFlt in 57%. Thus the expression of VEGF within normal glomeruli is complex and variable, with inter- and intra-individual variation. Furthermore, sFlt appears to be the co-dominant form of VEGF receptor expressed within glomeruli, suggesting that, in healthy individuals, a degree of VEGF autoregulation is the norm. The physiological importance of VEGF148 remains to be confirmed.
TL;DR: Plasma levels of adrenomedullin did not change significantly after nitric oxide inhalation, but significantly increased in association with the elevation of the total pulmonary resistance during the long-term follow-up period, suggesting that plasma levels of cortisol increase in proportion to the extent of pulmonary hypertension.
Abstract: Adrenomedullin, a potent hypotensive peptide, reduces blood pressure and pulmonary vascular resistance, and increases pulmonary blood flow. The mRNA for adrenomedullin and its receptor is highly expressed in the lung, suggesting a regulatory role for adrenomedullin in the pulmonary circulation. To investigate the clinical significance of adrenomedullin in patients with pulmonary hypertension, we studied the relationship between plasma levels of adrenomedullin and pulmonary haemodynamics. Venous, arterial and pulmonary arterial blood samples were obtained during cardiac catheterization and plasma levels of adrenomedullin were measured by specific radioimmunoassay in 33 consecutive patients with severe pulmonary hypertension (12 cases of primary pulmonary hypertension, 21 with chronic thromboembolic pulmonary hypertension; age 49+/-16 years, mean pulmonary arterial pressure 50+/-15mmHg). In addition, plasma levels of adrenomedullin were measured before and after acute nitric oxide inhalation. The changes in plasma adrenomedullin during the follow-up period of 10.3+/-4.3 months were also evaluated (n=5). Sixty-two healthy subjects served as the control group. Adrenomedullin was measured in an antecubital vein in the controls. Plasma levels of adrenomedullin were significantly higher in the patients with pulmonary hypertension than in the control subjects (10.1+/-8.7 versus 4.9+/-1.1pmol/l, P<0.01). Plasma levels of adrenomedullin, expressed as their natural logarithm, were significantly correlated with mean right atrial pressure (r=0.71, P<0.01), stroke volume (r=-0.63, P<0.01), total pulmonary resistance (r=0.60, P<0.01), mean pulmonary arterial pressure (r=0.37, P<0.05), and the natural logarithm of plasma atrial natriuretic peptide (r=0. 63, P<0.01). Plasma levels of adrenomedullin did not change significantly after nitric oxide inhalation, but significantly increased in association with the elevation of the total pulmonary resistance during the long-term follow-up period. These results suggest that plasma levels of adrenomedullin increase in proportion to the extent of pulmonary hypertension.
TL;DR: It is shown that aprotinin adds little benefit to the stability of cardiac peptides at room temperature, and blood samples for BNP and N-terminal ANP measurement used as a test of heart function in hospital clinics and by general practitioners in the community could be taken into blood tubes containing only EDTA as anticoagulant and without the additional step of adding the routinely used inhibitor aProtinin.
Abstract: Brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP) and N-terminal ANP are good research indices of the severity of heart failure. The stability of these peptides at room temperature has become an important factor in assessing their use as indicators of cardiac function in routine clinical practice. Inhibitors such as aprotinin are routinely added in the blood collection process, but may provide no benefit in sample collection and routine clinical practice. We assessed the stability of BNP, ANP and N-terminal ANP in blood samples collected in either the presence or the absence of the protease inhibitor aprotinin. Blood, either with or without aprotinin, was processed immediately (initial; 0 h) and after blood samples had been left for 3 h, 2 days or 3 days at room temperature. These times were chosen to reflect processing in a hospital outpatient clinic (2-3 h), or when posted from general practice (2-3 days). Initial plasma BNP, ANP and N-terminal ANP levels in the absence of aprotinin were 28.2+/-5.4, 44.2+/-7.9 and 1997+/-608 pg/ml respectively, and were not significantly different from initial values in the presence of aprotinin (29.0+/-5.9, 45.2+/-8.0 and 2009+/-579 pg/ml respectively). After 3 h at room temperature, there was a significant fall in ANP in the absence of aprotinin (36. 7+/-7.9 pg/ml; P<0.005), but not in the presence of aprotinin (41. 2+/-7.6 pg/ml). Both BNP and N-terminal ANP were unchanged in either the absence (BNP, 27.6+/-5.5 pg/ml; N-terminal ANP, 2099+/-613 pg/ml) or the presence (BNP, 29.4+/-5.6 pg/ml; N-terminal ANP, 1988+/-600 pg/ml) of aprotinin. After 2 days at room temperature, ANP had fallen significantly in both the absence (16.9+/-3.4 pg/ml) and the presence (24.0+/-5.0 pg/ml) of aprotinin compared with initial values, and there was a significant difference in ANP levels in the absence and presence of aprotinin (P<0.001). ANP levels had decreased further after 3 days at room temperature, to 11.9+/-3.4 pg/ml (no aprotinin) and 20.3+/-5.0 pg/ml (aprotinin added); these values were significantly different (P=0.002). In contrast, there was no change in the levels of BNP or N-terminal ANP after 2 or 3 days at room temperature, in either the absence or the presence of aprotinin. These studies indicate that aprotinin adds little benefit to the stability of cardiac peptides at room temperature. Blood samples for BNP and N-terminal ANP measurement used as a test of heart function in hospital clinics and by general practitioners in the community could be taken into blood tubes containing only EDTA as anticoagulant and without the additional step of adding the routinely used inhibitor aprotinin.
TL;DR: A significant positive association was found between the level of the acute-phase protein response and serum levels of interleukin-6, soluble tumour necrosis factor receptor 55 and soluble tumours necrosisfactor receptor 75 in cancer patients and in controls.
Abstract: The level of the acute-phase response is a major predictor of survival in patients with advanced pancreatic cancer. This study examines the association between the acute-phase protein response, as determined by serum C-reactive protein, and serum levels of interleukin-6, soluble interleukin-6 receptor and the soluble tumour necrosis factor receptors in patients with pancreatic cancer. Thirty-four blood samples were collected from 13 patients with advanced pancreatic cancer. Samples were also collected from six healthy subjects. Levels of C-reactive protein, interleukin-6, soluble interleukin-6 receptor and soluble tumour necrosis factor receptors 55 and 75 were measured by indirect ELISA. Serum levels of C-reactive protein, interleukin-6 and soluble tumour necrosis factor receptors 55 and 75 were significantly higher in cancer patients than in controls. Levels of serum soluble interleukin-6 receptor were not significantly different between the two groups. In cancer patients, a significant positive association was found between the level of the acute-phase protein response and serum levels of interleukin-6, soluble tumour necrosis factor receptor 55 and soluble tumour necrosis factor receptor 75. No association was found between levels of soluble interleukin-6 receptor and any other factor. There is no significant relationship between the level of soluble interleukin-6 receptor and the acute-phase protein response in vivo and the biological role of soluble interleukin-6 receptor in the chronic inflammatory component of cachexia remains unclear.
TL;DR: Individuals with blindness report a significant curtailment of total sleep time and hence resulting daytime somnolence, which impacts on daytime activities.
Abstract: Blind individuals are not only handicapped by their loss of vision, but are also affected because the loss of sight may have a secondary impact on functioning of their biological clock. The objective of the present study was to determine the impact of visual loss on sleep/wake disorders. A prospective 48-item questionnaire survey was distributed to blind individuals through the French Association Valentin Hauy, which serves blind persons. A control group matched by age, sex, geographical location and professional activity/non-activity was obtained from a panel of 20000 households representative of the French population, and this group also completed the questionnaire. From a potential blind population of 1500 subjects, 1073 questionnaires (71.5%) were completed and usable for analysis, and from a potential 1000 control subjects, 794 (79. 4%) of the questionnaires were returned and analysed. Criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, 4th revision, and the International Classification of Sleep/Wake Disorders (1990) were used to determine pathology. Individuals determined to be 'totally blind' and 'almost blind' (i.e. with less than 10% vision left in only one eye) presented a significantly higher occurrence of sleep/wake disorders than controls. Nocturnal sleep disruption, daytime somnolence, and (to a lesser degree) a 'free-running' condition are significantly more common in blind individuals. There is an increased use of sleeping pills, and a higher incidence of inappropriate involuntary daily naps. In conclusion, individuals with blindness report a significant curtailment of total sleep time and hence resulting daytime somnolence, which impacts on daytime activities. A 'free-running' condition is also a common sleep/wake impairment that may compound the handicap of blindness.
TL;DR: It is the absence of lowfrequency power that relates most closely to sympathetic activation in heart failure, and this component of HRV cannot be used for between-subject comparisons of central sympathetic nervous outflow.
Abstract: The concept that spectral analysis of heart rate variability (HRV) can estimate cardiac sympathetic nerve traffic in subjects with both normal and impaired left ventricular systolic function has not been validated against muscle sympathetic nerve activity (MSNA). We used coarse-graining spectral analysis to quantify the harmonic and non-harmonic, or fractal, components of HRV and to determine low-frequency (0.0-0.15 Hz; PL) and high-frequency (0.15-0.5Hz; PH) harmonic power. To test the hypothesis that MSNA and HRV representations of sympathetic nerve activity (PL and PL/PH) increase in parallel in heart failure, we recorded heart rate and MSNA during supine rest in 35 patients (age 52.4+/-2 years; mean+/-S. E.M.), with a mean left ventricular ejection fraction of 22+/-2%, and in 34 age-matched normal subjects. Power density was log10 transformed. Mean MSNA was 52.9+/-2.6 bursts/min in heart failure patients and 34.9+/-1.9 bursts/min in normal subjects (P<0.0001). In normal subjects, but not in heart failure patients, total power (PT) (r=-0.41; P=0.02) and fractal power (PF) (r=-0.36; P=0.04) were inversely related to age. In heart failure patients, total and fractal power were reduced (P<0.009 for both), and were inversely related to MSNA burst frequency (r=-0.55, P=0.001 and r=-0.60, P=0. 0003 respectively). In normal subjects, there was no relationship between MSNA and either PL or PH. In heart failure patients, as anticipated, PH was inversely related to MSNA (r=-0.41; P<0.02). However, PL was also inversely rather than directly related to MSNA (r=0.44 for 1/log10 PL; P<0.01). There was no relationship between other sympathetic (PL/PH) or parasympathetic (PH/PT) indices and MSNA in either heart failure patients or normal subjects. The lack of concordance between these direct and indirect estimates of sympathetic nervous system activity indicates that this component of HRV cannot be used for between-subject comparisons of central sympathetic nervous outflow. It is the absence of low-frequency power that relates most closely to sympathetic activation in heart failure.
TL;DR: It is concluded that standard haemodialysis activates a marked and reversible sympathetic response in both stable and unstable uraemic patients, however, in unstable patients, such activation is impaired in late dialysis, therefore contributing to the onset of the hypotensive crisis.
Abstract: The purpose of this study was to evaluate the autonomic response to standard haemodialysis and the changes associated with the onset of intradialytic hypotension in 12 normotensive patients with uraemia. Power spectra of R-R interval and of blood pressure fluctuations were obtained during a standard dialysis session and estimated in the low-frequency (LF, 30-150 mHz) and high-frequency (HF, 150-400 mHz) range. The absolute power of the LF component of blood pressure variations and the LF/HF ratio of R-R interval were assumed as indexes of sympathetic activity. Standard haemodialysis induced hypotension in six patients (unstable) while a minor pressure decline was present in the other six (stable). Normalized blood volume before dialysis and percentage volume reduction were similar in the two groups. Tachycardia in response to pressure and volume decrease was more pronounced in stable than in unstable patients, as evidenced by a higher slope of the relation between R-R interval and systolic blood pressure (7.9 versus 0.9 ms/mmHg, P<0.01). Sympathetic tone was enhanced during early dialysis in all patients (+2+/-1 for R-R LF/HF ratio, +2.4+/-0.6 mmHg2 and +7.2+/-2 mmHg2 for absolute LF power of diastolic and of systolic blood pressure respectively, P<0.05), compared with baseline predialysis values. During late dialysis, unstable patients showed an impairment of sympathetic activation which preceded hypotension and was maximal during the crisis (-2.9+/-1.4 for R-R LF/HF ratio, -2.7+/-1.4 mmHg2 and -8.6+/-4.0 mmHg2 for absolute LF power of diastolic and of systolic blood pressure respectively, P<0.05). On the contrary, stable patients showed constantly elevated indexes (+3.7+/-1.4 for R-R LF/HF ratio, +5.9+/-2.7 mmHg2 and +13.3+/-6.2 mmHg2 for LF of diastolic and of systolic blood pressure, P<0.05). Values returned to predialysis levels after the end of the dialysis session in all patients. We conclude that standard haemodialysis activates a marked and reversible sympathetic response in both stable and unstable uraemic patients. However, in unstable patients, such activation is impaired in late dialysis, therefore contributing to the onset of the hypotensive crisis.
TL;DR: It is suggested that extracellularly administered alpha-lipoic acid reduces AGE-albumin-induced endothelial expression of VCAM-1 and monocyte binding to endothelium in vitro and may contribute to the understanding of a potential antioxidative treatment of atherosclerosis.
Abstract: Advanced glycation end products (AGEs) have been identified as relevant mediators of late diabetic complications such as atherosclerotic disease. The endothelial migration of monocytes is one of the first steps in atherogenesis and monocyte-endothelial interaction itself is linked to the expression of adhesion molecules like vascular cell adhesion molecule-1 (VCAM-1). Recently, stimulation of VCAM-1 by AGEs has been demonstrated. Since endothelial stimulation by AGEs is followed by generation of oxygen free radicals with subsequent activation of nuclear transcription factor kappaB, we investigated the influence of alpha-lipoic acid on the expression of VCAM-1 and monocyte adherence to endothelial cells in vitro by means of cell-associated chemiluminescence assays and quantitative reverse transcriptase polymerase chain reaction using a constructed recombinant RNA standard. We found that alpha-lipoic acid was able to decrease the number of VCAM-1 transcripts from 41. 0+/-11.2 to 9.5+/-4.7 RNA copies per cell in AGE-stimulated cell cultures. Furthermore, expression of VCAM-1 was suppressed in a time- and dose-dependent manner by alpha-lipoic acid as shown by chemiluminescence endothelial cell assay. Pretreatment of endothelial cells with 0.5 mM or 5 mM alpha-lipoic acid reduced AGE-induced endothelial binding of monocytes from 22.5+/-2.9% to 18. 3+/-1.9% and 13.8+/-1.8% respectively. Thus, we suggest that extracellularly administered alpha-lipoic acid reduces AGE-albumin-induced endothelial expression of VCAM-1 and monocyte binding to endothelium in vitro. These in vitro results may contribute to the understanding of a potential antioxidative treatment of atherosclerosis.
TL;DR: High levels of CD11b expression, depressed platelet and monocyte counts, and high concentrations of IL-6, IL-8 and sIL-2R predict OF in patients with community-acquired septic shock, and the combination of these markers may provide the means to identify sepsis patients who will develop OF.
Abstract: To obtain predictors of organ failure (OF), we studied markers of systemic inflammation [circulating levels of interleukin-6 (IL-6), IL-8, soluble IL-2 receptor (sIL-2R), soluble E-selectin and C-reactive protein, and neutrophil and monocyte CD11b expression] and routine blood cell counts in 20 patients with systemic inflammatory response syndrome and positive blood culture. Eight patients with shock due to community-acquired infection developed OF, whereas 11 normotensive patients and one patient with shock did not (NOF group). The first blood sample was collected within 48 h after taking the blood culture (T1). OF patients, as compared with NOF patients, had at T1 a lower monocyte count, a lower platelet count, higher levels of CD11b expression on both neutrophils and monocytes, and higher concentrations of IL-6, IL-8 and sIL-2R. C-reactive protein and soluble E-selectin concentrations did not differ between groups. No parameter alone identified all patients that subsequently developed OF. However, a sepsis-related inflammation severity score (SISS), developed on the basis of the presence or absence of shock and on the levels of markers at T1, identified each patient that developed OF. The maximum SISS value was 7. The range of SISS values in OF patients was 2–5, and that in NOF patients was 0–1. In conclusion, high levels of CD11b expression, depressed platelet and monocyte counts, and high concentrations of IL-6, IL-8 and sIL-2R predict OF in patients with community-acquired septic shock, and the combination of these markers may provide the means to identify sepsis patients who will develop OF.
TL;DR: Oxygen delivery was reduced in CFS patients compared with that in sedentary controls, and a significant correlation was found between oxidative metabolism and recovery of oxygen delivery.
Abstract: The purpose of this study was to determine if chronic fatigue syndrome (CFS) is associated with reduced oxygen delivery to muscles. Patients with CFS according to CDC (Center for Disease Control) criteria (n=20) were compared with normal sedentary subjects (n=12). Muscle oxygen delivery was measured as the rate of post-exercise and post-ischaemia oxygen-haem resaturation. Oxygen-haem resaturation was measured in the medial gastrocnemius muscle using continuous-wavelength near-IR spectroscopy. Phosphocreatine resynthesis was measured simultaneously using (31)P magnetic resonance spectroscopy. The time constant of oxygen delivery was significantly reduced in CFS patients after exercise (46.5+/-16 s; mean+/-S.D.) compared with that in controls (29.4+/-6.9 s). The time constant of oxygen delivery was also reduced (20.0+/-12 s) compared with controls (12.0+/-2.8 s) after cuff ischaemia. Oxidative metabolism was also reduced by 20% in CFS patients, and a significant correlation was found between oxidative metabolism and recovery of oxygen delivery. In conclusion, oxygen delivery was reduced in CFS patients compared with that in sedentary controls. This result is consistent with previous studies showing abnormal autonomic control of blood flow. Reduced oxidative delivery in CFS patients could be specifically related to CFS, or could be a non-specific effect of reduced activity levels in these patients. While these results suggest that reduced oxygen delivery could result in reduced oxidative metabolism and muscle fatigue, further studies will be needed to address this issue.
TL;DR: The findings of the present study indicate a means by which adenosine challenge of the airways can induce bronchoconstriction and support a role forAdenosine in the pathophysiology of asthma.
Abstract: Previous studies have shown that in vitro adenosine enhances histamine release from activated human lung mast cells obtained by enzymic dispersion of lung parenchyma. However, adenosine alone has no eect on histamine release from these cells. Given the evidence for direct activation of mast cells after endobronchial challenge with adenosine and previous studies indicating that mast cells obtained at bronchoalveolar lavage are a better model for asthma studies than those obtained by enzymic dispersion of lung tissue, the histamine-releasing eect of adenosine was examined on lavage mast cells. Bronchoalveolar lavage fluid was obtained from patients attending hospital for routine bronchoscopy (n fl 54). Lavage cells were challenged with adenosine or adenosine receptor agonists (20 min, 37 ∞C) and histamine release determined using an automated fluorometric assay. Endogenous adenosine levels were also measured in lavage fluid (n fl 9) via an HPLC method. Adenosine alone caused histamine release from lavage mast cells in 37 of 54 patients with a maximal histamine release of 20.56‡2.52% (range 5.2‐61%). The adenosine receptor agonists (R)-N 6 -(2-phenylisopropyl)adenosine, 5«-N-ethylcarboxamidoadenosine and CGS21680 also induced histamine release from lavage mast cells. Preincubation of lavage mast cells with the adenosine receptor antagonist xanthine amine congener caused significant inhibition of the response to adenosine (P fl 0.007). There was an inverse correlation between endogenous adenosine levels in the lavage fluid and the maximal response to in vitro adenosine challenge of the lavage cells. The findings of the present study indicate a means by which adenosine challenge of the airways can induce bronchoconstriction and support a role for adenosine in the pathophysiology of asthma. The results also suggest that cells obtained from bronchoalveolar lavage fluid may provide the ideal model for the testing of novel, adenosine receptor, targeted therapies for asthma.
TL;DR: In this paper, the authors compared different techniques to try to establish the best method for maximizing the number of visible perfused capillaries during intravital capillary microscopy.
Abstract: Intravital capillary video-microscopy is a dynamic method for studying skin capillaries. The technique of direct intravital microscopy (without dyes) depends on the presence of red blood cells inside capillaries for their identification. The aim of the present study was to compare different techniques to try to establish the best method for maximizing the number of visible perfused capillaries during intravital capillary microscopy. We compared the effects of venous congestion with those of post-occlusive reactive hyperaemia (Study 1). We also investigated venous congestion followed first by post-occlusive reactive hyperaemia and then by a core heat load test (Study 2). Finally we investigated venous congestion followed by post-occlusive reactive hyperaemia combined with venous congestion (Study 3). In Study 1, capillary density increased with venous congestion from a baseline value of 74±2 (mean±S.E.M.) per field to 82±3 per field ( P P = 0.01). With both reactive hyperaemia and core heat load, the apparent density was 62±4 per field. In Study 3 the baseline density was 70±2 per field, and this increased significantly with venous congestion to 80±3 per field ( P P = 0.328 compared with venous congestion alone). The results show that venous congestion at 60 mmHg for 2 min is the most effective method for visualization of the maximal number of perfused skin capillaries during intravital video-microscopy.