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At least 613 records · Page 34Linked to original sources

PubMed2002

New method: the intravital videomicroscopic characteristics of the microcirculation of the urinary bladder in rats.

Intravital fluorescence microscopy (IVM) is a widely used method to study the microcirculation in several organs. Our aim was to develop a standard rat model to evaluate the microcirculatory characteristics of the urinary bladder under physiological pressure conditions using the most advanced fluorescence videomicroscopic techniques. Spraque-Dawley rats were used after filling their bladders with a constant volume of saline solution. The intravesical pressure was continuously monitored. The bladder was positioned on a specially designed stage and IVM measurements were made at the beginning, the 90th, 120th and 180th min. Arteriolar and venular diameters, functional capillary density, venular red blood cell velocity, arteriolar and venular macromolecular leakage and leukocyte-endothelial cell interactions (observation of rolling and firmly adherent leukocytes) were quantitatively assessed by a computer assisted analysis system. Neither microcirculatory parameters nor the intravesical pressure changed significantly during the observation period of 180 min using constant filling volume. We successfully established a new, well functioning and reproducible model to study the microcirculation of the rat bladder using intravital fluorescent microscopy.

Animals↗

PubMed1996

[Effect of different single agent antihypertensive therapies on peri-foveal microcirculation in patients with arterial hypertension].

PURPOSE: Arterial hypertension is known to be an important risk factor for cerebral and cardiovascular disease. Previous studies have demonstrated alterations in the perifoveal microcirculation in patients with essential hypertension. During follow-up a progression of these alterations has been reported. In the present study we quantified the retinal microcirculation of patients with hypertension under different systemic antihypertensive medication. METHODS: The patients were divided into three groups according to their medication. Group 1 was treated with beta-blocker (n = 17), group 2 with ACE inhibitors (n = 10), and group 3 with calcium channel blockers (n = 11). All patients underwent fluorescein angiographic studies with a scanning laser ophthalmoscope. Perifoveal intercapillary areas (PIA) and the mean perifoveal capillary velocity were quantified from the angiograms. RESULTS: Compared with reference values, all three groups of patients with essential hypertension showed significantly increased PIA and significantly decreased capillary velocity. No difference could be detected between the three groups of patients treated with beta-blocker, ACE inhibitor or calcium channel blocker. CONCLUSION: Alterations of the perifoveal network are found in patients with arterial hypertension. These alterations are similar under antihypertensive monotherapy using beta-blocker, ACE inhibitor or calcium channel blocker.

Adult↗

PubMed2000

Comparison of anastomotic microcirculation in coloanal J-pouches versus straight and side-to-end coloanal reconstruction: an experimental study in the pig.

Several studies have shown a lower rate of anastomotic leakages in patients with coloanal J-pouch reconstruction than in those with straight coloanal anastomosis following anterior resection of the rectum. This study investigated whether this difference is due to a better anastomotic microcirculation. Thirty-two healthy, adult Göttinger mini-pigs underwent anterior rectal resection. They were subsequently randomized to following four groups (eight pigs per group): straight end-to-end, side-to-end, small pouch (4 cm), and large pouch (8 cm) coloanal anastomosis. Bowel perfusion was measured before and after vessel ligature at predefined locations using laser Doppler flowmetry. After completion of the anastomosis microcirculation was investigated 1 cm above, below, and directly at the anastomotic site. Following vessel ligature there was a 25% drop in blood flow. After completion of the anastomosis there was a further decrease of 25% in the distal segment, while no changes were observed above the anastomosis. There were no statistical differences either before or after completion of the anastomosis between the various groups. It is concluded that anastomotic blood flow does not depend on the type of coloanal reconstruction in healthy pigs.

Anastomosis, Surgical↗

PubMed1998

[Disorders of microcirculation in coronary heart disease].

Disturbances of microcirculation in coronary artery disease can be seen in the presence of critical stenosis of epicardial coronary arteries, as a result of endothelial dysfunction in the absence of significant stenosis or during recovery of ischaemic myocardium after successful angioplasty of stenosed or occluded coronary arteries. Diagnostic methods are morphologic/morphometric analyses, measurement of the global coronary reserve, measurement of the regional coronary microcirculation (scintigraphy, positron emission tomography) and laboratory analysis of haemorheological alterations (plasma, erythrocytes, leucocytes). After successful angioplasty, normalisation of glutamate extraction rate takes three to six months. In patients with unstable angina, changes in plasma viscosity, erythrocyte aggregation and neutrophil activation occur. Neutrophils are activated after successful angioplasty in acute myocardial infarction and even after elective angioplasty (when measured in the coronary sinus). Therapeutic improvements of disturbed microvascular flow can be obtained by increasing perfusion pressure (by revascularisation, nitrates, calcium antagonists, physical training), by improving the fluidity of the blood and by reducing the extravascular component of coronary vascular resistance (by antihypertensive treatment).

Angina Pectoris↗

PubMed2006

Microcirculation in rat soleus muscle after eccentric exercise: the effect of nifedipine.

This paper explores the role of the calcium entry blocker nifedipine in the explanation of eccentric exercise-induced fibre damage by changes in skeletal muscle microcirculation. Eccentric exercise (EE) was induced by indirect stimulation of rat soleus muscle in its lengthening phase during cycling. Muscle damage was assessed by histology, electron microscopy and muscle tension 48 h later. Diameters of arterioles and venules, their response to dilator and constrictor stimuli and pattern of capillary flow were measured in epiiluminated muscles using intravital microscopy. Tetanic tension developed by EE muscles was lower (8.60 +/- 1.02, means +/- SEM, n = 8 N g(-1) wet weight compared to 12.25 +/- 0.56 in controls, P < 0.01). Electron microscopy showed changes similar to those in muscles exposed to EE by downhill running (Z line streaming, disruption of sarcolemma, swollen tubules). A total of 16% of muscle fibres were damaged, and fibre areas and interstitial space were enlarged. Capillary red blood cell flow showed tendency to a greater intermittency. Large venules were narrower, but arterioles and smaller venules had diameters similar to control muscles. Vessel dilatation to topically applied 10(-4) M adenosine was attenuated. Daily administration of calcium entry blocker nifedipine by gavage (2 mg/kg/day in two equal doses) removed the narrowing of venules, restored the dilator response of all vessels to adenosine and increased capillary:fibre ratio. The percentage of damaged fibres decreased to 4.7 and the size of the interstitial space and fibre areas was normalized. Thus muscle damage caused by eccentric exercise was attenuated by nifedipine due to its beneficial effect on muscle microcirculation, which was impaired by eccentric exercise.

Adenosine↗

PubMed2004

Postoperative recovery of microcirculation after gastric tube formation.

BACKGROUND AND AIMS: The formation of a gastric tube is associated with partial devascularisation of the stomach and impaired tissue perfusion in the anastomotic region. The aim of the study was to gain data on the time interval of microcirculatory recovery of the normal gastric conduit. PATIENTS AND METHODS: Twenty-nine out of 49 consecutive patients who had undergone oesophagectomy and reconstruction with a gastric tube and intrathoracic oesophagogastrostomy were selected. Inclusion criterion was an uncomplicated postoperative course. After the patients' admission to ICU, continuous measurement of mucosal pCO(2) (pCO(2)I) was commenced, with the use of recirculating gas analysis with a TONOCAP device. pCO(2)I values (in mmHg and kPa) were recorded hourly and related to the arterial pCO(2) (DeltapCO(2) = pCO(2)I - pCO(2)a). In addition, mean arterial pressure (MAP), cardiac output (CO) and systemic vascular resistance (SVR) were measured by pulse contour analysis. RESULTS: pCO(2)I was monitored over an average period of 79 h (total 2,288 measurements). The mean DeltapCO(2) before extubation was 12.4 mmHg (1.7 kPa) +/- 8.7 SD (1.2 kPa). After extubation, there was an increase in DeltapCO(2) values in all 29 patients. The peak DeltapCO(2) of 27.4 mmHg (3.7 kPa) +/- 12.6 SD (1.7 kPa) was observed 18 h after extubation. This was followed by a steady decline in DeltapCO(2) values that almost reached baseline DeltapCO(2) values after 4 days of monitoring. Changes in DeltapCO(2) did not correlate with changes in MAP, CO and SVR. CONCLUSIONS: High levels of pCO(2)I indicate an impaired postoperative microcirculation in normal gastric tubes. After initial deterioration, gastric microcirculation takes approximately 4 days to recovery. These data are important for the implementation of ischaemic conditioning prior to gastric tube formation and gastric pull-up.

Adult↗

PubMed2004

Microcirculation and excretory function of the liver under conditions of carbon dioxide pneumoperitoneum.

BACKGROUND: To date, the effects of increased abdominal pressure, as given during carbon dioxide (CO(2)) pneumoperitoneum, on hepatic microcirculation and biliary excretion are unknown. METHODS: Using a custom-made peritoneal cavity chamber, we performed intravital microscopy of the left liver lobe under conditions of CO(2) pneumoperitoneum in a rat model. In addition, biliary excretion was assessed. RESULTS: The establishment of a CO(2) pneumoperitoneum of 4 or 8 mmHg resulted in sinusoidal perfusion failure that was more pronounced in the periportal regions than in the midzonal and pericentral regions of the liver acinus. Biliary excretion was considerably reduced at an intraabdominal pressure of 8 mmHg. Leukocyte-endothelial cell interactions increased significantly in both hepatic sinusoids and postsinusoidal venules. CONCLUSION: Alterations in hepatic microcirculation and liver function must be taken into consideration in any kind of laparoscopic surgery and may be of particular clinical relevance in patients with liver pathology.

Animals↗

PubMed2006

Geomagnetic field modulates artificial static magnetic field effect on arterial baroreflex and on microcirculation.

Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K ( p ) indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (DeltaBRS with DeltaMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow (K-index with DeltaMPPG; r (s)=-0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect.

Animals↗

PubMed2003

Transanal laser Doppler flowmetry to assess microcirculation in the upper rectum during abdominal aortic aneurysmectomy.

PURPOSE: Fatal ischemic colitis can develop after abdominal aortic aneurysmectomy. We investigated the effectiveness of transanal laser Doppler flowmetry (LDF) for assessing microcirculation in the rectal mucosa during aneurysm repair. METHODS: The subjects were 17 patients who underwent abdominal aortic aneurysmectomy. A Doppler laser and Doppler probe were mounted on a rectoscope, which was inserted into the anus, and rectal flux values were obtained by a flowmeter. RESULTS: The mean flux value during aortic clamping was 146 +/- 35.6 perfusion units (PU) in patients with sufficient collateral circulation to the upper rectum and 58.3 +/- 19.4 PU in patients with insufficient collateral circulation ( P << 0.01). The LDF values and inferior mesenteric artery stump pressure measurements were well correlated ( r = 0.86). CONCLUSION: Transanal rectal LDF is useful for continuously assessing microcirculation in the rectal mucosa during abdominal aneurysmectomy, and the data obtained with this method may reflect whether a collateral pathway to the upper rectum exists.

Adult↗

PubMed2000

Responses of the skin microcirculation to acetylcholine and to sodium nitroprusside in chronic uremic patients.

The aim of the present study was to assess the endothelial function of the microcirculation in chronic renal failure. We investigated the responses of the cutaneous blood flow to locally delivered acetylcholine and sodium nitroprusside in uremic patients. The study included 60 chronic uremic patients: 40 patients with a creatinine clearance of 4-25 ml/min were on conservative treatment and 20 patients were on maintenance hemodialysis. The changes in skin blood flow following iontophoretic delivery of acetylcholine (an endothelium-dependent vasodilator) and sodium nitroprusside (an endothelium-independent vasodilator) were measured by laser Doppler flowmetry. Acetylcholine induced a progressive increase in blood flow in both groups, reaching approximately 100% of the maximal hyperemic response obtained by sodium nitroprusside delivery. The percent increase in blood flow from baseline was lower in hemodialysis patients than in patients on conservative treatment, after both acetylcholine (550 +/- 44 vs. 718 +/- 61%, P < 0.05) and sodium nitroprusside (553 +/- 46 vs. 735 +/- 69%, P < 0.05) delivery. In the hemodialysis group, the hyperemic responses to acetylcholine and sodium nitroprusside did not improve after the hemodialysis session. Hence, the hyperemic responses of the skin microcirculation are lower in hemodialysis patients than in patients on conservative treatment, and did not ameliorate after hemodialysis. It seems to be independent of endothelial dysfunction, and associated with the severity of uremia and with the maintenance hemodialysis treatment. This microcirculatory abnormality is in keeping with the arterial stiffness and vascular wall damages described in dialysis patients, which contribute to the cardiovascular morbidity of chronic uremia.

Acetylcholine↗

PubMed2002

Endoscopic transthoracic sympathicotomy and peripheral microcirculation: effects of electric sympathetic chain stimulation, thermocoagulation and anaesthetic agents.

BACKGROUND: During endoscopic transthoracic sympathicotomy (ETS) in patients with hyperhidrosis it is useful to assess the effect of surgery peroperatively. However, the autonomic system is affected in various ways by different anesthetic agents. In the present study, the effect of ETS during either isoflurane or propofol anesthesia was evaluated by measuring changes in the finger pulp microcirculation using laser Doppler flowmetry (LDF). Electric stimulation of the sympathetic chain was used for identifying the sympathetic chain and to explore whether the anesthetic agents differentially influenced the LDF response to stimulation. METHODS: From a group of 12 patients with incapacitating palmar hyperhidrosis, six were randomly assigned to isoflurane and six to propofol anesthesia. LDF probes were attached to the ipsilateral finger pulp for continuous recording of peripheral blood flow during the ETS procedure. Electric stimulation (1 Hz, 10 Hz, and 100 Hz) was applied to the sympathetic paravertebral chain at the levels of the 2nd and 3rd sympathetic ganglia via a custom designed bipolar electrode. In eight of the patients LDF recordings were also performed in the awake state and compared with records obtained from eight healthy subjects. FINDINGS: In patients anesthetized with isoflurane, the base line finger pulp blood flow did not significantly differ from that of awake normal subjects, while those anesthetized with propofol had a lower base line flow, similar to that of awake subjects with hyperhidrosis. Stimulation of the sympathetic chain induced marked reduction of finger pulp microcirculation in both anesthetic groups, and this effect was frequency dependent during isoflurane anesthesia. After ETS a significant increase in flow was recorded only in the propofol group. Interpretation. The study demonstrates that the completeness of the sympathicotomy can only be peroperatively evaluated if an anesthetic agent with relatively low vasodilatory capacity, as e.g. propofol, is utilized.

Adult↗

PubMed2005

Computer modeling of red blood cell rheology in the microcirculation: a brief overview.

One of the major functions of the cardiovascular system is to deliver blood to the microcirculation where exchange of mass and energy can take place. In the present article, we will provide an overview of the state-of-the-art computational methods for modeling of red blood cell (RBC) rheology and dynamics in the microcirculation. While significant progress has been made in simulation of single-file motion of deformable RBCs in capillaries and of diluted sheared suspensions of RBCs in infinite domains, detailed understanding of the mechanics of blood flow in intermediate diameter microvessels (8-1,000 microm) has presented formidable challenges. The difficulties are largely due to modeling the motion of multiple, interacting, highly deformable particles. The current computational tools consist mainly of three-dimensional (3D) boundary-integral methods for single RBC dynamics and deformation; and for rheology of large systems of droplets at large volume fractions using periodic boundary conditions and novel adaptive computational meshes. Further advances will result from combination of these tools to produce new algorithms capable of describing the motion and deformation of large systems of RBCs in microvessels at physiologically relevant volume fractions.

Animals↗

PubMed1992

Effects of endothelin on microcirculation of the pancreas.

Endothelin, a newly described endothelial-derived peptide, has potent vasoconstrictive properties and has been speculated to play a physiological role in the regulation of blood flow in some organs. The present study was designed to evaluate the effects of endothelin-1, endothelin-2 and endothelin-3 on the pancreatic microcirculation. Pancreatic tissue blood flow was measured by a laser Doppler flow meter in anesthetized dogs and endothelin-1, endothelin-2 or endothelin-3 was injected intravenously in graduated doses. Endothelins induced dose-dependent decreases in pancreatic tissue blood flow. Endothelin-1, endothelin-2 and endothelin-3 at a dose of 100 pmol/kg reduced pancreatic blood flow by 45.4%, 19.6% and 51.9%, respectively, whereas systemic arterial blood pressure was not significantly affected. When endothelin-3 was administered at a dose of 1000 pmol/kg, pancreatic blood flow was decreased by 73.5% with a concomitant increase of systemic arterial blood pressure by 17.6%. Endothelins potently decreased pancreatic tissue blood flow, suggesting a possible role of these agents in regulating the pancreatic microcirculation.

Analysis of Variance↗

PubMed1984

A new microscopic system for the continuous observation of the coronary microcirculation in the beating canine left ventricle.

A microscope system was designed using a new type of objective lens which makes possible the direct and continuous observation of the coronary microcirculation throughout the entire cardiac cycle in the beating canine heart. The microscope system consists of a standard microscope and a floating objective system which is composed of a pair of convex lenses and transmits a real image of the coronary microcirculatory bed to a standard microscope without any change in magnification. The convex lens facing the heart is supported by a weight-adjusting coil spring and low-resistance ball bearings which allow the lens to move perpendicularly in unison with cardiac motion. To reduce excessive cardiac movement, two 24-gauge needles connected to the animal table by a needle holder are horizontally inserted through the midmyocardium of the left ventricle beneath the area of interest. The epimyocardium of the left ventricle is transilluminated by means of a light pipe and a xenon-arc lamp. The distance between the floating lens and the cardiac surface is kept constant using a spacing device connected to the light pipe holder to prevent the compression of the tissue in the microscopic field of view. This improvement in the microscope system combined with high-speed cinematography greatly facilitates the continuous analysis of the coronary microcirculation in the beating left ventricle throughout the entire cardiac cycle, and may provide a useful approach to the understanding of the regulation mechanism of the coronary circulation.

Animals↗

PubMed1986

The effects of transmural transport in the microcirculation: a two gas species model.

Diffusion of oxygen and carbon dioxide across the walls of noncapillary vessels in the microcirculation has been suggested by several studies. The formulation and steady-state solutions to a nine-compartment mathematical model of the microcirculation of skeletal muscle with transmural gas diffusion in all vessels are presented. The simultaneous transport of oxygen and carbon dioxide between arterioles, capillaries, and venules, and connective and muscle tissue at rest and exercise are described. Special attention is paid to the interactions of these gases in blood. This model predicts a longitudinal intravascular gradient in oxygen tension from large to small vessel with the tension at the precapillary vessels relatively insensitive to changes in the input tension. At rest, there is significant small arteriolar oxygen flux. However, during exercise, the precapillary transmural flux of oxygen is only a small fraction of the total metabolic demand. The model predicts large noncapillary fluxes of carbon dioxide, and also that tissue PCO2 is dependent on input tensions. The model also predicts that Bohr shifts due to either changes in input PCO2 or increased precapillary PCO2 due to increased metabolism may cause physiologically significant changes in precapillary PO2. Countercurrent shunting was predicted by the model to be significant only for carbon dioxide.

Animals↗

PubMed1989

Influence of diltiazem on postischemic microcirculation and function in the rat kidney.

Renal microcirculation and function were studied in the unilateral clamp-induced ischemia/reperfusion model in anesthetized rats. After 60-min reperfusion fluorochromelabeled globulin was injected i.v. allowing histological determination of capillary plasma flow patterns (CPFP). In the 60-min ischemia protocol the untreated group revealed poor capillary labeling in the outer medulla (OM), whereas cortical perfusion patterns were only slightly altered. Pre- and postischemic treatment with diltiazem led to significant improvement of CPFP in the OM: 4.9% of tissue areas were lying more than 60 microns from the next perfused capillary vs 70.2% after untreated ischemia. Postischemic treatment with diltiazem proved much less effective. Inulin clearance (CIn) amounted to less than 2% of baseline values irrespective of the treatment regimen. However, in the 30-min ischemia protocol, displaying normal CPFP, preservation of CIn was evident and most effective after pre- and postischemic diltiazem treatment (53% vs 8% after untreated ischemia). Measurements of tubular function, however, did not reveal any significant improvement after diltiazem treatment. This observation and the fact that the drugs has a vasodilating effect lend support to the view that the preservation of glomerular filtration rate (GFR) is most likely mediated by vascular mechanisms. In conclusion, in this experimental model diltiazem significantly reduced postischemic disturbances of renal microcirculation occurring after prolonged periods of ischemia and was clearly efficient in maintaining GFR after shorter ischemic episodes; however, tubular function was not preserved. Our results, as well as those of other authors, strongly suggest that diltiazem causes the aforementioned effects mainly by actions at the vascular site.

Animals↗

PubMed1991

Reactive hyperemia in term neonates and adults--a laser Doppler fluxmetry study of skin microcirculation.

The reactivities of neonatal and adult microcirculation have been studied and compared. The cutaneous reactive hyperemia after 1 and 4 min of arterial occlusion (AO) was measured with a laser-Doppler fluxmeter in 21 healthy neonates and 10 adults. Local skin temperature, mean arterial blood pressure (MAP), and skin prick hematocrit were also determined at the same time. The magnitude of neonatal reactive hyperemia was approximately one-third that of the adult response regardless of the duration of AO. In both groups, with age-specific regressions, the hyperemic blood flow response after 4 min of AO developed more slowly in subjects with low MAP and was of low magnitude in subjects with high hematocrit values. In response to a prolongation of AO, from 1 to 4 min, the magnitude and duration of hyperemia increased significantly and similarly in both neonates and adults. We conclude that compared to adults neonates have a less pronounced ability to increase skin microcirculation in response to local ischemia. The normally low blood pressure and high hematocrit in newborn infants contribute further to this conclusion.

Adult↗

PubMed1995

Blood coagulation equilibrium in rat liver microcirculation as evaluated by endothelial cell thrombomodulin and macrophage tissue factor.

The regulatory mechanisms of microcirculation might differ in the liver from other organs, because macrophages are resident in the hepatic sinusoids and sinusoidal endothelial cells are unique in shape and function. Thrombomodulin expression in endothelial cells and tissue factor activity in isolated macrophages were studied in the liver and lung of rats. In normal rats, the thrombomodulin expression was minimal in hepatic sinusoids, but prominent in pulmonary capillaries, while the tissue factor activity in the presence of endotoxin was higher in pulmonary macrophages than in Kupffer cells, although the levels in the absence of endotoxin were comparable in both cells. The tissue factor activity in hepatic macrophages was increased after priming of the cells with Corynebacterium parvum or after induction of liver necrosis or cirrhosis with carbon tetrachloride. In the necrotic or cirrhotic liver, increased thrombomodulin expression was seen along capillaries extending in necrotic areas and regenerating nodules, but this increase was minimal in the Corynebacterium parvum-treated rat liver. Blood coagulation equilibrium in microcirculation regulated by endothelial cells and macrophages may differ between the liver and lung. Such equilibrium in the liver may vary depending on pathological status.

Animals↗