摘要:

The present study analyses the peripheral circulatory effects of pump perfusion on a sympathectomized cat skeletal muscle in terms of effects on segmental vascular resistances (large‐bore arterial vessels, arterioles and veins), hydrostatic capillary pressure, capillary filtration coefficient, transcapillary filtration and autoregulation of blood flow. The effect of prostacyclin during pump perfusion was analysed to evaluate whether it interferes with the pump‐induced vascular alterations, especially if it reduces transcapillary filtration through its capillary permeability decreasing effect. Pump perfusion initiates a marked vasodilation (from 17.3 to 10.1 PRU), an increase in hydrostatic capillary pressure, and a marked inhibition of myogenic reactivity and of autoregulation of blood flow. There was a slow restoration of vascular tone reaching a steady‐state level somewhat below the autoperfusion value within 2 h. Pump perfusion did not change the capillary filtration coefficient, indicating that the capillary permeability was not increased. This implies that short‐term pump‐induced capillary leakage is more an effect of increase in hydrostatic capillary pressure, perhaps in combination with increased number of open capillaries, than of an increase in capillary permeability. Prostacyclin decreased capillary permeability by at least 22% but simultaneously increased hydrostatic capillary pressure, resulting in an unchanged filtration compared with the situation just after the starting of the pump. The results obtained show that experiments using pump perfusion should be interpreted with care due to the interference with normal peripheral vascular control. The results give reasonable explanations of the lowered blood pressure and transcapillary fluid loss during the clinical use of a heart‐l

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.548320000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The exact nature of the decrease in foot skin blood flow seen after a change in posture remains unsettled. This mechanism has previously been examined by non‐invasive techniques such as the laser Doppler perfusion monitor (laser Doppler flowmetry). Taking into account the shortcomings of laser Doppler perfusion monitoring when applied to the determination of skin blood flow, which normally shows substantial heterogeneity, we have applied an emerging technology, the laser Doppler perfusion imager (LDPI). This technique provides a more comprehensive picture of the blood flow distribution in the skin, as it maps skin blood flow over a surface area (120×120 mm, 4096 measurement sites). It was used to examine if the reduction in tissue perfusion or the alterations in flow distributions seen after a change in posture (supine to dependency) could be fully explained by an increase in venous pressure (venous stasis of 50 mmHg) or if the data suggest a complementary mechanism.Skin blood flow of the forefoot decreased from 0.60 V (volt) (median) during rest to 0.40 and 0.38 V during venous stasis and dependency, respectively. Although almost identical median values were obtained during stasis and dependency, the flow distributions were different, with a loss of high flow values during venous stasis. Biological zero was 0.24 V.As the LDPI technique readily records skin perfusion during variations in venous stasis and posture, as well as information on flow distribution changes, it appears promising for future application in stimuli‐response studies of skin blood flow. The difference in flow distribution seen between increased venous pressure and dependency suggests an additive regulatory mechanism to the veni‐vasomotor reflex during a change in p

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.587345000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

Complex interactions appear to exist between the renin–angiotensin system and sympathetic neurotransmission, and sympathetic activity may influence local angiotensin II formation. Arterial and forearm venous plasma levels of angiotensin I and II were therefore studied in 11 healthy males at rest, during sympathetic activation elicited by mental stress, and during adrenaline induced vasodilation. Specific assays for angiotensin‐(1–8) octapeptide and for angiotensin‐(1–10) decapeptide (i.e. angiotensin II and I, respectively), were used. Special precautions to minimizeex vivoformation and/or degradation of angiotensins were employed. Mental stress increased regional noradrenaline overflow three‐fold, with a concomitant three‐fold increase in forearm blood flow, whereas intravenous adrenaline infusion increased forearm blood flow two‐fold and noradrenaline overflow four‐fold. There was a constant positive veno‐arterial concentration difference for angiotensin I under all conditions tested, compatible with local angiotensin I formation. We found no veno‐arterial concentration difference for angiotensin II or regional net angiotensin II overflow under the conditions tested. These results in the forearm circulation support previous animal experimental evidence in skeletal muscle and provide no evidence in favour of ade novoformation of angiotensin II in skeletal musclein vivoduring basal conditions. Furthermore, sympathetic nerve stimulation does not seem to enhance angiotensin II generation importantly

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.580330000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The effects of a 6‐week programme of endurance training on soleus muscle capillarity were examined, in terms particularly of the proportions of arteriolar and venular capillaries and their capillary domain area, in young (3‐week‐old) and middle‐aged (54‐week‐old) Wistar rats. Exercise protocols for the young training group were: 10–22.5 m min−1, 60 min day−1for 6 days a week, with a gradient of 7 degrees during the final 2 weeks; for the middle‐aged training group, the protocols were: 10–20 m min−1, 50 min day−1for 6 days a week. In both young and middle‐aged training groups, the density of arteriolar capillaries was significantly increased (P<0.05), but that of venular and intermediate capillaries was decreased slightly. The proportion of arteriolar capillaries therefore was significantly (P<0.05) increased, from 63.9 to 73.1%, in young rats and from 33.0 to 48.4%, in middle‐aged rats after training. The increase in the proportion of arteriolar capillaries is an advantageous adaptation to exercise‐induced increases in oxygen demand. In both young and middle‐aged rats, capillary domain area and Krogh's tissue cylinder radii in all capillary portions decreased after training. These results suggest that adaptive changes in oxygen transport system, identified as an increase in the arteriolar capillary and a reduction in diffusion distance for oxygen, were observed in middle‐aged as well as in young rats. However, capillary angiogenesis induced by exercise appeared to be greate

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.582353000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

Rhythmic contractions are produced by small arteries, arterioles and veins in several vascular beds, but they are often absent in large arteries. However, under certain conditions, and in certain disease states, large arteries may produce rhythmic contractions. For this reason, the present study was undertaken to test the hypothesis that rhythmic contractions may be a ‘normal’ response in large arteries at some stage in development. We investigated this hypothesis by examining contractions of carotid arteries in male and female rats aged 15, 25 and 30 days, and in adult rats. Rhythmic contractions were produced by exposure to, or during washout of, α‐adrenoceptor agonists in young, but not adult, rats. In particular, rhythmic activity was identified in 40, 95 and 50% of the arteries from, respectively, 15, 25 and 30‐day‐old rats. No differences were found in rhythmic activity between female and male rats. Furthermore, the rhythmic activity was not inhibited by the K+channel blocker TEA (20 mm), or the Na+/K+‐ATPase inhibitor, ouabain (32 μm). Nor was it inhibited by endothelial denudation. However, the Ca2+channel blocker, nifedipine (0.1 μm), completely eliminated rhythmic contractions. These results suggest that receptor‐induced rhythmic contractile activity is a ‘normal’ characteristic at ∼25 days of development in carotid arteries of rats, but that this activity declines with age until it is completely absent by adulthood. We proposed that this difference was due to unfused and fused Ca2+channel activities in, respectively, young and adult rat arteries, to differential expression of Ca2+channel isotypes, or to differences in receptor‐mediated signal transduction mechanisms ‘u

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.579338000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The cutaneous circulation is thought to participate in the neurocirculatory adjustments during orthostatic stress, but the underlying mechanisms mediating such reflex cutaneous vasoconstriction are poorly understood. The aim of this study was to assess the relative importance of baroreceptor (cardiopulmonary and arterial) and positional (vestibular, exercise, veno‐arteriolar and myogenic) reflexes in triggering cutaneous vasoconstriction during upright posture.First, hypotensive lower body negative pressure (LBNP) was compared with actual postural changes to assess the relative contributions of baroreceptor reflexes and positional reflexes. Then changes in body position were compared with changes in limb position in the absence or presence of proximal (axillary) or distal (local cutaneous) nerve blocks, to assess the relative contributions of vestibular, exercise, veno‐arteriolar and myogenic reflexes. Skin sympathetic nerve activity was determined by microneurography, and skin blood flow was determined by laser Doppler velocimetry.LBNP of –50 mmHg (cardiopulmonary + arterial baroreceptors) had no effect on skin sympathetic nerve activity or skin vascular resistance. In contrast, an upright posture with the arms dependent (baroreceptor+vestibular+exercise+veno‐arteriolar reflexes) caused a two‐ to threefold increase in skin vascular resistance. In the supine position, passive movement of the arm into a dependent position to activate veno‐arteriolar reflexes alone evoked an increase in skin vascular resistance which approximated the response to normal upright posture.Blocking central sympathetic nerve impulses by application of an axillary blockade did not influence the cutaneous vasoconstrictor response to an upright posture or changes in limb position. In contrast, application of a distal nerve block by local cutaneous surface anaesthesia completely blocked vasoconstrictor responses evoked by these manoeuvres.In conclusion, these experiments in human subjects identify a primary role for veno‐arteriolar reflexes in triggering vasoconstriction in the cutaneous circulation during up

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.573344000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The mechanical properties of the aorta play a major role in the regulation of blood pressure and cardiac performance. The effect of sympathetic stimulation on the mechanical properties of the human abdominal aorta was studied in 19 healthy volunteers, divided into young (25±2 years) and elderly individuals (69±2 years) of both sexes. A non‐invasive ultrasonic echo‐tracking system for measurement of systolic/diastolic variation of aortic diameter in combination with intra‐aortic pressure measurements was used to determine wall mechanics. The pressure–diameter (P–D) relationship and the distensibility indices, stiffness (β) and pressure strain elastic modulus (Ep) of the abdominal aorta were obtained. Measurements were made at rest and during sympathetic stimulation induced by lower body negative pressure (LBNP).As a sign of sympathetic activation, the peripheral resistance increased by 74–96% (P<0.001) during LBNP. However, the mechanical properties of the abdominal aorta remained unaltered, as estimated either from theP–Drelationship or from the indicesEpand β, both in the young (rest:Ep=0.53±0.18, β=4.5±1.5; LBNP:Ep=0.51±0.15, β=4.5 ±1.2, NS) and in the elderly (rest:Ep=2.17±0.70, β=17.6 ±5.8; LBNP:Ep=2.11±0.60, β=16.9±3.9, NS).In conclusion, this investigation shows that LBNP‐induced sympathetic activation does not change aortic wall mechanics. Thus, sympathetic modulation of the aortic smooth muscle contractile activity seems to be unimportant i

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.581343000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The effect of intravenous administration of the endothelium‐derived vasoconstrictor peptide endothelin‐1 (ET‐1 0.2, 1 and 8 pmol kg−1min−1) on coronary blood flow in relation to plasma ET‐1 as well as blood lactate and glucose levels were investigated in six healthy volunteers. Coronary sinus blood flow was measured by thermodilution. Administration of ET‐1 elevated arterial plasma ET 35‐fold, dose‐dependently increased mean arterial blood pressure from 95±5 mmHg to 110±6 mmHg (P<0.01) and reduced heart rate from 64±4 beats min−1to 58±4 beats min−1(P<0.05) at 8 pmol kg−1min−1. Coronary sinus blood flow was reduced maximally by 23±4% (P<0.01) and coronary vascular resistance increased by 48±11% (P<0.01). Coronary sinus oxygen saturation decreased from 35±1% to 22±2% at 2 min after the infusion (P<0.01). A coronary constrictor response was observed at a 4‐fold elevation in plasma ET. The reduction in coronary sinus blood flow lasted 20 min and coronary sinus oxygen saturation was still reduced 60 min after the infusion. Myocardial oxygen uptake or arterial oxygen saturation were not affected by ET‐1. Myocardial lactate net uptake decreased by 40% whereas glucose uptake was unaffected. At the highest infusion rate there was a net removal of plasma ET by 24±3% over the myocardium (P<0.05). The results show that ET‐1 induces long‐lasting reduction in coronary sinus blood flow via a direct coronary vasoconstrictor effect in healthy humans observable at a 4‐fold elevation in plasma ET‐1. Furthermore, there is a net

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.578350000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The current understanding of the mechanisms controlling the proliferation and differentiation of the stem cells of the gastric oxyntic glands is limited. The aim of the present study was to develop a method for investigating proliferation and differentiation of undifferentiated cells from fetal rat stomach. Outgrowth of cells was initiated from explants of 16‐day‐old fetal rat stomachs. At this stage of the fetal development the gastric epithelial cells are undifferentiated. The explants were cultured in DMEM/F‐12 medium supplemented with fetal calf serum only, or fetal calf serum combined with either hydrocortisone or pentagastrin. Morphological characterization by means of light microscopy, dye staining and immunostaining was used to identify the growing cells. Both hydrocortisone and pentagastrin accelerated the differentiation towards H,K‐ATPase‐positive cells, mucus‐producing cells and other epithelial cells. H,K‐ATPase‐positive cells, which were identified by immunostaining with a monoclonal antibody reacting with the α‐subunit of the H,K‐ATPase, grew on top of the confluent layer of epithelioid and fibroblastoid cells. With this methodin vitroinvestigations of the mechanisms of proliferation and differentiation of gastric mucosal cells are possible. Although by different mechanisms, both hydrocortisone and pentagastrin appear to play a regulatory rol

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.589348000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

The morphological and phenotypical features of the class II molecule (HLA‐DR) expressing cells in human dental pulps were compared with those of previously characterized perivascular dendritic cells in the dermis. We have further investigated how these pulpal cells are structurally related to the vascular system. Double‐immunofluorescence staining revealed that a substantial portion of the pulpal HLA‐DR expressing cells also expressed factor XIIIa, a marker for dendritic cells. The cells usually had a highly dendritic appearance and formed a reticular network in the pulpal connective tissue. The majority of cells also expressed macrophage‐related antigens (CD14 and CD68). A small but distinct population of pulpal cells, representing approximately 13% of the class II molecule expressing cells, was devoid of a typical macrophage phenotype. This subpopulation of pulpal cells may be similar to dendritic cells present in the dermis. Confocal laser scanning microscopy showed that highly dendritic cells, found in close relation to the endothelium, had dendritic processes which were found to be in contact with the peripheral cell membrane of the endothelial cells. These cells formed a three‐dimensional structure around the microvessel resembling a cellular conduit. We conclude that the human dental pulp is equipped with class II molecule‐expressing perivascular dendritic cells composed of a heterogeneous cell

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.584337000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY