摘要:

The geometry of the coronary capillary bed in human hearts was studied using samples obtained during cardiac surgery of children operated for tetralogy of Fallot and samples from fresh normal hearts used for valve harvesting. The results revealed a similar coronary capillary density and heterogeneity of capillary spacing in samples from both groups. A double-staining method was used to distinguish between capillary segments close to the feeding arteriole (proximal capillaries) and segments distant from the arteriole (distal capillaries). In both groups of hearts, capillary segment length was consistently shorter on the venular than the arteriolar portion of the capillary. Similarly, capillary domain areas were also smaller and the resulting capillary supply unit was smaller along venular portions compared to arteriolar regions of the capillary bed. This distinctive geometry would provide advantageous geometric conditions for tissue oxygen supply.

ISSN:0167-6865    

DOI:10.1159/000179203

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The aim of this study was to investigate the relationships between laser Doppler perfusion monitoring (LDPM) measurements and different systemic hematocrits in microcirculation in terms of changes in oscillatory flow patterns. The hamster cheek pouch microvasculature was visualized by a fluorescent microscopy technique, and LDPM signals were derived from arterioles and venules under control conditions and after isovolemic hemodilution with saline and 6% dextran, MW 70,000, to 26.1 ± 2.1 %. Vasomotion, oscillations of microvascular blood flow (flow motion) and red blood cell (RBC) velocity were analyzed with Fourier transform and autoregressive modeling. LDPM recordings presented a significant increase in perfusion units (PU) during hemodilution – 184 ± 15 versus baseline 137 ± 11 PU in arterioles and 40.2 ± 3.5 versus 28.6 ± 4.3 PU in venules – that was correlated with a significant increment in arteriolar and venular RBC velocity. There was a rise in the frequency [2.9 ± 0.5 cycles per min (cpm) vs. 1.8 ± 0.5 cpm] and spectral power of flow motion in arterioles whereas the increase in spectral power was related to a decrease in frequency (12.6 ± 2.1 vs. 3.6 ± 0.7 cpm) in venules. Oscillations in arteriolar and venular RBC velocity revealed coincident frequency components with flow motion patterns. The present data suggest that the LDPM measurements are more sensitive to velocity than hematocrit. Furthermore, hemodilution appears to affect differently arteriolar and venular flow mot

ISSN:0167-6865    

DOI:10.1159/000179204

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:0167-6865    

DOI:10.1159/000179265

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

We have recently shown that the responsiveness of rat intestinal arterioles to increased sympathetic nerve activity is modulated by the actions of endothelial-derived nitric oxide. Because the microvascular endothelium can also produce vasodilator prostaglandins, the purpose of this study was to determine if endogenous cyclooxygenase products also limit sympathetic arteriolar constriction in this vascular bed. Intravital microscopy was used to study the responses of small feed arteries, first-order arterioles and second-order arterioles to perivascular sympathetic nerve stimulation in the superfused rat small intestine. Stimulation at 3, 8 and 16 Hz caused frequency-dependent constrictions of each vessel type that are abolished by the α-adrenoceptor antagonist phentolamine (10-6Msuperfusate concentration). The cyclooxygenase inhibitor meclofenamate (3 × 10-5M superfusate concentration) completely abolished the dilator responses to topically applied arachidonic acid, but had no effect on the magnitude or rate of sympathetic constriction in any vessel type. These results suggest that endogenous cyclooxygenase activity does not influence sympathetic tone in the intestinal microvasculatur

ISSN:0167-6865    

DOI:10.1159/000179205

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The effect of hepatic nerve stimulation and norepinephrine (NE) on the laser Doppler signal from the surface of the perfused rat liver was tested. The livers from male Wistar rats were perfused in situ via the portal vein with Krebs-Henseleit buffer containing 20% bovine erythrocytes (37 °C, pH 7.4) and total liver blood flow (TLBF) was by timed collection of effluent. Portal vascular resistance (PVR) was calculated from the pressure difference across the liver. Linearity of laser Doppler flowmetry (LDF) with TLBF was confirmed in all preparations. Stimulation of the hepatic nerves (2 ms, 20 V) was performed at frequencies between 0.5 and 20 Hz (n = 11). NE was added to the buffer at concentrations between 10-10 and 10-6M(n = 8). A stimulus-dependent rise in PVR occurred during hepatic nerve stimulation (basal, 3.11 ± 0.26 dyn s cm-5) and NE administration (basal, 2.62 ± 0.29 dyn s cm-5), with a maximum effect at 20 Hz (311 ± 45%) and 10-6M(591 ± 72%), respectively. Both LDF and TLBF fell during nerve stimulation and NE. A linear relationship (r = 0.99; p < 0.001) between change in TLBF (%) and LDF flux (%) was found for NE (10-10 to 10-6M). During nerve stimulation, the fall in TLBF and LDF flux was linear with the logarithm of stimulus frequency and reached a maximum at 10 and 20 Hz, respectively. At a stimulus frequency of 20 Hz, the change in LDF was significantly different from the change in TLBF (p < 0.001). We conclude from our findings that during high-frequency hepatic nerve stimulation, LDF underestimates

ISSN:0167-6865    

DOI:10.1159/000179206

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:0167-6865    

DOI:10.1159/000179260

出版商:S. Karger AG    

年代:1997

数据来源: Karger