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PubMedDate not supplied

Acute and chronic changes in the microcirculation of the liver in inbred strains of mice following infection with mouse hepatitis virus type 3.

The acute and chronic effects of mouse hepatitis virus type 3 on the microcirculation of the liver in both semisusceptible C3HeB/FeJ and fully resistant A/J mice were studied. In the C3HeB/FeJ mice, abnormalities of microcirculatory flow were noted as early as 12 hr after infection and by 24 hr, localized avascular foci appeared. Disturbances were characterized by granular blood flow, sinusoidal microthrombi, distortion of sinusoids by edematous hepatocytes and necrotic lesions. Following the acute infection, Day 10, two patterns of chronic disease were observed. Eighty percent of the mice developed chronic granulomatous hepatitis whereas in the remaining 20% a more severe chronic aggressive hepatitis was observed which was characterized by ongoing hepatocellular necrosis and a marked mononuclear cell infiltrate. In both cases, in vivo microcirculatory abnormalities were found predominantly around visible lesions. Onset of the microcirculatory abnormalities was found to be concomitant with a rise in monocyte related procoagulant activity. Procoagulant activity rose acutely and remained elevated throughout the chronic phase but was higher in animals with severe disease. In contrast to the above, normal blood flow and histology were seen in the resistant A/J mice at all times following infection, and procoagulant activity remained at basal levels despite active viral replication as demonstrated by immunofluorescence studies and recovery of infectious virus. These observations suggest a role for monocyte procoagulant activity in the development of microcirculatory abnormalities following mouse hepatitis virus type 3 infection which may be important in the pathogenesis of the disease.

Animals↗

PubMed1989

The rat liver microcirculation in alcohol-induced hepatomegaly.

It has been suggested that hepatocyte enlargement can lead to compression of the extracellular space (sinusoidal and interstitial) and induce portal hypertension. However, this hypothesis has never been tested by measuring the vascular and extravascular spaces in the intact liver. The aim of the present study was to investigate the effects of chronic alcohol intake on the hepatic microcirculation using Goresky's multiple-indicator dilution technique in the isolated perfused rat liver. Female rat littermates were pair-fed either ethanol (n = 7) or an isocaloric carbohydrate diet (n = 7) for 21 days. As expected, chronic alcohol intake produced a significant increase in liver/body weight ratio (+32%, p less than 0.01) and hepatocyte size (+45%, p less than 0.001), which was accompanied by a marked increase in the cellular water space (control: 3.3 +/- 0.6 ml; ethanol-fed: 4.9 +/- 0.9 ml; p less than 0.001). When expressing data per total liver, the sinusoidal space was similar in the two groups (control: 1.87 +/- 0.2; ethanol-fed: 1.95 +/- 0.2 ml; not significant), whereas the interstitial space was increased in alcohol rats compared to controls (albumin space +58%, p less than 0.01; sucrose space +51%, p less than 0.01). In alcoholic rats, the sinusoidal space was probably stretched, with an overall reduced transversal diameter, as suggested by the reduced values found when data were expressed per gm of liver weight. However, despite this finding and the enlargement of the liver and hepatocytes observed in alcoholic rats, similar values were obtained between the two groups for the portal perfusion pressure and thus the intrahepatic vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗

PubMed1996

The hepatic microcirculation in the isolated perfused human liver.

In cirrhosis, capillarization of sinusoids could result in impaired exchanges between the hepatocytes and the blood perfusing the liver and contribute to liver failure irrespective of the metabolic capacity of the liver. To characterize anomalies of the hepatic microcirculation, we used the multiple-indicator dilution approach in isolated perfused livers obtained from patients with cirrhosis at the time of transplantation, and from organ donors with normal or near-normal livers or hepatic steatosis. In organ donors, the sinusoidal volume and the permeability of sinusoids to albumin, sucrose, and water were found to be comparable to that of normal dog and rat livers. The sinusoidal volume and the extravascular volume (EVV) accessible to diffusible tracers were larger after hepatic artery than after portal vein injection, probably because of an unshared arterial sinusoidal bed. In cirrhotic livers, two kinds of alterations were found: the appearance of a barrier between the sinusoids and the hepatocytes (capillarization) and intrahepatic shunts. The extravascular space accessible to albumin decreased with increasing severity of cirrhosis, and the diffusion of sucrose in the space of Disse showed a barrier-limited pattern, instead of the normal flow-limited behavior. In cirrhotic livers, a correlation was found between the hepatic extraction of indocyanine green (ICG) and the extravascular space accessible to albumin (r = .84, P < .05), suggesting that the impaired access of this protein-bound dye to the hepatocyte surface contributed to its impaired elimination. Intrahepatic shunts were found between portal and hepatic vein (21% +/- 16% of portal flow), but not between hepatic artery and hepatic veins. We conclude that (1) the behavior of diffusible tracers in human livers with normal liver architecture is comparable to that reported in normal animals; (2) the permeability of sinusoids in cirrhotic livers is abnormal, (3) permeability changes are related to changes in liver function in cirrhosis.

Adolescent↗

PubMed1999

The effect of mechanically enhancing portal venous inflow on hepatic oxygenation, microcirculation, and function in a rabbit model with extensive hepatic fibrosis.

Enhancing the portal venous blood flow (PVBF) has been shown to reduce portal pressure and intrahepatic vascular resistance and to improve liver function in isolated cirrhotic rodent livers in vitro. The aim of this study was to assess the short-term effect of mechanically pumping the portal inflow on hepatic microcirculation (HM), oxygenation, and function in an animal model of extensive hepatic fibrosis. New Zealand white rabbits underwent laparotomy and exposure of the liver: group 1 (n = 7) were normal controls; group 2 (n = 7) had hepatic fibrosis. Total hepatic blood flow (THBF) and HM was measured along with continuous monitoring of intrahepatic tissue oxygenation using near infrared spectroscopy (NIRS). Baseline hepatic hemodynamics and liver function were measured in both groups. PVBF was then increased by 50% over a 3-hour period in the hepatic fibrosis group using a miniature portal pump designed for human implantation, and the hemodynamics were monitored continuously. Liver function tests were repeated after portal pumping. In comparison with normal controls, animals with hepatic fibrosis had a higher portal pressure (13.0 +/- 3.6 vs. 3.7 +/- 1.4 mm Hg, P <.001, mean +/- SD vs. controls), reduced PVBF (52.4 +/- 24.6 vs. 96.9 +/- 21.1 mL/min, P =.003), and increased portal vascular resistance (P =. 001). THBF and flow in the HM was lower than in controls, and liver function tests were abnormal. After a 3-hour period of enhanced portal flow in animals with hepatic fibrosis, the portal pressure greatly reduced (13.0 +/- 3.6 to 2.5 +/- 1.1 mm Hg, P <.001) as did the intrahepatic portal resistance (0.32 +/- 0.18 to 0.04 +/- 0.03 mm Hg/mL/min, P =.006). Flow in the HM improved (143 +/- 16 to 173 +/- 14 flux units, P =.006) and was associated with improved hepatic tissue oxygenation, tissue oxy-hemoglobin (HbO2) and cytochrome oxidase being increased by 24.4 +/- 7.5 and 5.65 +/- 2.30 micromol/L above the baseline value (P <.001), respectively. A 3-hour period of mechanical portal pumping produced a dramatic improvement in liver function, bilirubin (41.1 +/- 25.9 to 10.0 +/- 5.9 micromol/L, P =. 040), aspartate transaminase (AST) (135.5 +/- 52.3 to 56.3 +/- 19.8 U/L, P =.006) and lactate dehydrogenase (LDH) (2,030.1 +/- 796.3 to 1,309.8 +/- 431.6 IU/L, P =.006; prepumping vs. postpumping, all P <. 050). In conclusion, portal pumping in this rabbit model with extensive hepatic fibrosis improved liver parenchymal perfusion, oxygenation, and function.

Animals↗

PubMed1992

Inhibition site of dexamethasone on extravasation of polymorphonuclear leukocytes in the hamster cheek pouch microcirculation.

A video system was used to investigate the inhibitory effect(s) of the glucocorticoid dexamethasone (DEX) on polymorphonuclear leukocyte (PMN) extravasation in the microcirculation of hamster cheek pouch. DEX was given intraperitoneally at 0.1 or 0.3 mg/kg body weight 2 h before induction of extravasation by topical application of leukotriene B4 (LTB4) or formyl-methionyl-leucyl-phenylalanine (fMLP) on the microvasculature. The number, time course, and behavior of PMNs were examined in the following five steps of extravasation: (1) rolling on the venular endothelium, (2) adhesion on the endothelium, (3) passage between the endothelial cells, (4) staying in the venular wall, and (5) migration from the venular wall into the interstitial space. In either the presence or absence of DEX, topical application of LTB4 (15 pmol/50 microliters) or fMLP (10 nmol/50 microliters) caused an increase in the number of PMNs that adhered to the venules. Thus, DEX did not inhibit the adhesion of PMNs on the endothelial cells. The adhered PMNs induced by these chemoattractants became gradually smaller, finally disappearing in the vascular lumen, as observed on the monitor screen. The whole process took about 10 min. This passage of PMNs between the endothelial cells was also not inhibited by DEX, as over 90% of the adhered PMNs passed through the endothelial cells and advanced to the next step of extravasation in the presence or absence of DEX. When these chemoattractants were applied to DEX-untreated animals, the PMNs that passed through the endothelial cells stayed for about 30 min in the venular wall. Thereafter, PMNs migrated into the interstitial space. The numbers of PMNs in the interstitial space were counted at 30, 60, and 90 min after the application of chemoattractants. In the DEX-untreated animals, PMNs in the interstitial space started to appear by 30 min, and thereafter the number further increased. However, in the DEX-treated animals, the number of PMNs at 60 and 90 min was significantly suppressed. Since DEX may inhibit the synthesis and/or release of a proteinase(s) in the PMN granules, which would normally degrade the basement membrane, this inhibition may be due to the inability of PMNs to penetrate the basement membrane.

Animals↗

PubMedDate not supplied

Imaging of diffusion and microcirculation with gradient sensitization: design, strategy, and significance.

Recent developments in the use of magnetic resonance (MR) to measure and image diffusion and blood microcirculation ("perfusion") are summarized. After a brief description of the effects of diffusion and perfusion on the MR signal, the different methods (conventional spin-echo, stimulated-echo, gradient-echo, and echo-planar imaging) that have been proposed and used to image and measure diffusion and perfusion by gradient sensitization are presented, along with their advantages and limitations. The difficulties of diffusion/perfusion imaging related to both hardware and software are then discussed. Special attention is given to specific problems encountered with in vivo studies and data analysis. Finally, the potential biologic and clinical applications are outlined, and some examples are presented.

Brain↗

PubMedDate not supplied

MR imaging of microcirculation in rat brain: correlation with carbon dioxide-induced changes in blood flow.

Considerable interest has been shown in developing a magnetic resonance (MR) imaging technique with quantitative capability in the evaluation of tissue microcirculation ("perfusion"). In the present study, the flow-dephased/flow-compensated (FD/FC) technique is evaluated for measuring rat cerebral blood flow (CBF) under nearly optimal laboratory conditions. Imaging was performed on a 2.0-T system equipped with shielded gradient coils. Rat CBF was varied by manipulating arterial carbon dioxide pressure (PaCO2). In parallel experiments, optimized MR imaging studies (seven rats) were compared with laser Doppler flowmetry (LDF) studies (nine rats). LDF values showed a high degree of correlation between CBF and PaCO2, agreeing with results in the literature. MR imaging values, while correlating with PaCO2, showed considerable scatter. The most likely explanation is unavoidable rat motion during the requisite long imaging times. Because of this motion sensitivity, the FD/FC technique cannot provide a quantitative measure of CBF. It can, however, provide a qualitative picture.

Animals↗

PubMedDate not supplied

Assessment of tumor microcirculation: a new role of dynamic contrast MR imaging.

With the advances in MR techniques, information related to tumor microcirculation now can be obtained in the clinical setting. This information can be valuable in the assessment of tumor blood supply/oxygenation status and tumor response to therapy. In this article, we review the tracer-kinetic modeling for tumor microcirculatory parameters derived from dynamic contrast MR imaging and report several preliminary results from both an animal model and early experience with human tumors. Despite the application of different MR protocols and tracer-kinetic models, the initial results of these pioneer studies consistently support the role of MR-derived microcirculatory tumor parameters, in providing prognostic information to assess and predict the response of cancers to cytotoxic therapy.

Animals↗

PubMed1997

Acute effects of periarterial sympathectomy on the cutaneous microcirculation.

The clinical effects of peripheral sympathectomy on patients with vaso-occlusive disease are often dramatic and include relief of pain, improved quality of life, and healing of ulcers. Peripheral periarterial sympathectomy is known to increase skin temperature and to maximize the nutritional component of peripheral blood flow, but the pathophysiology of vaso-occlusive disease and the physiologic mechanisms of this treatment are unknown. In this study, the acute effects of periarterial sympathectomy were directly observed in a rabbit ear model of digital microcirculation (arterioles, arteriovenous anastomoses, and venules). The effects of periarterial sympathectomy on cutaneous perfusion and total flow were also examined using laser Doppler perfusion imaging and digital temperature measurements. The central auricular artery became dilated (50-100%) immediately after sympathectomy; the arterioles, arteriovenous anastomoses, and venules dilated to 165, 156, and 223%, respectively, at 30 minutes and to 187, 174, and 204%, respectively, at 60 minutes, relative to their baseline diameters prior to sympathectomy. Laser Doppler perfusion imaging values and ear temperatures were noted to increase after sympathectomy (8.9%, 3 degrees C), although the core temperature of the rabbit did not change. Thus, acute periarterial sympathectomy can (a) effectively reduce the vascular tone of the distal microvasculature and (b) increase total microcirculatory perfusion-cutaneous and thermoregulatory-by both venular and arteriolar dilation. Periarterial sympathectomy has the clinical potential to increase nutritional blood flow, thereby ameliorating the signs and symptoms of ischemia associated with thermoregulatory abnormalities. Dilation of the arteriovenous anastomoses, with a subsequent reduction in vascular resistance, may contribute to the increased cutaneous temperature noted after sympathectomy.

Anastomosis, Surgical↗

PubMed1999

Late-preconditioning protection is evident in the microcirculation of denervated skeletal muscle.

We investigated whether ischemic preconditioning induces microvascular protection in skeletal muscle at the late phase (after 24 hours) when the same muscles are subjected to prolonged warm global ischemia. The cremaster muscle of the male Sprague-Dawley rat underwent vascular isolation and was subjected to 4 hours of ischemia and 60 minutes of reperfusion. Early preconditioning consisted of 45 minutes of ischemia followed by 15 minutes of reperfusion before prolonged ischemia/reperfusion; late preconditioning also consisted of 45 minutes of ischemia but was done 24 hours (24-hour period of reperfusion) before the prolonged ischemia/reperfusion. Arteriole diameters and capillary perfusion were measured with use of intravital microscopy. Four groups were compared: rats that underwent early preconditioning, their controls, rats that underwent late preconditioning, and their controls. Early and late preconditioning significantly attenuated vasospasm and capillary no-reflow compared with the controls for each. Average arteriole diameter was significantly larger in the rats that underwent late preconditioning than in any other rats; it was also significantly larger in the controls for late preconditioning than in those for early preconditioning. We introduce a model of the rat cremaster muscle that has been isolated from its vascular supply as a useful preparation to study the effects of late preconditioning on microcirculation in skeletal muscle. Late preconditioning provided better microvascular protection than did early preconditioning. The mechanism for this preconditioning protection is being investigated because it should provide a means for therapeutic intervention.

Animals↗

PubMed1983

Noninvasive assessment of microcirculation of living organs and tissues using laser.

For studying microcirculation of intact tissues or organs, a new noninvasive, heat-transient method using laser photoexcitation is described. As a heating source an argon ion laser or R6G dye laser was used via a quartz fiber optic guide. Infrared radiation from heated tissue was detected by a thermography apparatus. After switching the laser irradiation on and off, a thermal transient curve of a model tissue, the skin, was biphasic: a component with a fast time constant and the other with a slow time constant. The temperature increases of both phases following laser irradiation were linear to the applied power from the laser onto the tissue. The temperature rises as a function of the wavelength of irradiated light have shown that the absorption of the light by tissue hemoglobin is a main heat-generation source. Furthermore, the temperature rises as a function of tissue blood volume and flow have shown that the component with a slow time constant is more related to the tissue hemoglobin concentration and tissue blood flow and heat conductivity. Thus, the analysis of heat-transient curves following laser irradiation gives information as to regional tissue blood volume, blood flow, and tissue heat conductivity.

Animals↗

PubMed2003

Changes in microcirculation after ischemic process in rat skeletal muscle.

Laser Doppler flowmetry (LDF) is a good method to investigate tissue microcirculation, but it has many standardization and measuring problems. To exclude these effects, we performed a test using LDF on rat skeletal muscle. In 12 CD outbred anesthetized rats, bilateral femoral vessels and the quadriceps femoris muscle were exposed. The left femoral artery and vein were clamped for 1 h by microvascular clips (ischemic side). On the right side, no other intervention was made (control side). An LDF probe was applied on the medial vastus muscle. Short-term occlusions (2-3 s) were performed before and after the 1-h clamping and on the control side while LDF curves were registered. The halftimes of ascending curves on the ischemic side were significantly elongated vs. the condition before clamping (P = 0.0007) or the control side (P = 0.0017). Microcirculatory changes caused by 1-h ischemia were shown by this simple, quick, and well-reproducible test on rat skeletal muscle.

Animals↗

PubMed1990

Vasodilator action of prostaglandin E1 on microcirculation of rat cremaster muscle.

Vascular spasm is often present after microsurgical procedures, and its presence or absence can greatly influence the success rate of such operations. Prostaglandin E1 (PGE1) is known to be a potent vasodilator and antiaggregator of small blood vessels. Using intravital videomicroscopy in the rat cremaster model, this study visually and quantitatively monitored changes in vessel diameter to observe the effect of PGE1 on the microcirculation and compared its action with that of 1% lidocaine. The results suggest that PGE1 (10 micrograms/ml) can significantly relieve epinephrine-induced vasoconstriction at the terminal arteriole, arteriole, and small artery level (vessel diameters 10-50 microns). The vasodilatory action of PGE1 is reflected by an increase in vessel diameter, and PGE1 may have a role in reversing vascular spasm after microsurgery, enhancing the survival rate of replanted extremities.

Administration, Topical↗

PubMed1993

New skeletal muscle model for the longitudinal study of alterations in microcirculation following contusion and cryotherapy.

This preliminary report describes the use of a rat model developed to study in vivo the effect of anesthesia, contusion, and cryotherapy on skeletal muscle microcirculation by use of an implanted chamber. The diameters of arterioles and venules within the chamber were determined by photomicroscopy in the contusion study and by compound videomicroscopy in the anesthesia study; microvascular perfusion was determined by laser Doppler fluxmetry (LDF). Combined ketamine and xylazine anesthesia significantly reduced (P < 0.05) arteriolar and venular diameters by 32.4% and 37.8%, respectively, and average LDF measurements by 36.1%. Contusion significantly increased arteriolar diameters over baseline values (P < 0.05); cryotherapy did not alter arteriolar diameters but increased venular diameters (P < 0.05). It is hypothesized that this increase in venular diameter may, by increasing the surface area available for reabsorption, explain one mechanism by which cryotherapy decreases the edema of contusion. Use of this model should help to advance the understanding of microcirculatory dynamics following contusion and cryotherapy.

Anesthesia↗

PubMed1995

Effect of postischemic reperfusion on microcirculation and lipid metabolism of skeletal muscle.

To study the effect of ischemia reperfusion injury on microvascular reactivity and tissue metabolism in skeletal muscle, a Sprague-Dawley rat cremaster muscle was prepared as a tourniquet ischemia model and subjected to 2 hr ischemia followed by 1 hr reperfusion to simulate the timing of ischemia during microvascular surgery. The dose-response curve of arteriolar reactivity to norepinephrine, lipid peroxidation, and ultrastructure of capillaries was determined in both the control and postischemic reperfusion stages. Judging from the results, we summarize our observations as follows: (1) Postischemic reperfusion significantly increased arteriolar reactivity to norepinephrine, in which the EC50 for vasoconstriction decreased in all three orders of arterioles. These results suggest that reperfusion could have impaired the vasodilation control mechanism, possibly being endothelium dependent. (2) Lipid peroxidation increased sixfold in the reperfusion group, suggesting that oxygen free radicals have produced significant tissue damage under the created conditions. (3) Significant endothelial damage in the capillaries shown by electron microscope observation supports these studies, indicating that ischemia/reperfusion in clinically transplanted skeletal muscles could cause significant damage to the tissue microcirculation both physiologically and metabolically.

Animals↗

PubMed2003

In vivo study of microcirculation in canine myocardium using the IVIM method.

The intravoxel incoherent motion (IVIM) method was implemented in closed-chest dogs to obtain measurements on microcirculation in the left ventricular wall in vivo. Specifically, it enabled us to measure the mean microflow velocity (400 +/- 40 microm/s) and the vascular volume fraction (VVF) (11.1% +/- 2.2%), and observe the directional preference of capillary orientation. The apparent diffusion coefficients (ADCs) of water along and perpendicular to myofibers were also measured. With vasodilatation by adenosine infusion, a 25% increase in the VVF and a 7% increase in the mean microflow velocity were observed, while no change in the ADC was detected. A 28.5% decrease of the ADC was observed postmortem.

Animals↗

PubMed2004

Microcirculation and microvasculature in breast tumors: pharmacokinetic analysis of dynamic MR image series.

The purpose of this study was to quantify microcirculation and microvasculature in breast lesions by pharmacokinetic analysis of Gd-DTPA-enhanced MRI series. Strongly T1-weighted MR images were acquired in 18 patients with breast lesions using a saturation-recovery-TurboFLASH sequence. Concentration-time courses were determined for blood, pectoral muscle, and breast masses and subsequently analyzed by a two-compartment model to estimate plasma flow and the capillary transfer coefficient per unit of plasma volume (F/VP, KPS/VP) as well as fractional volumes of the plasma and interstitial space (fP, fI). Tissue parameters determined for pectoral muscle (fP = 0.04 +/- 0.01, fI = 0.09 +/- 0.01, F/VP = 2.4 +/- 1.3 min(-1), and KPS/VP = 1.2 +/- 0.5 min(-1)) and 10 histologically proven carcinomas (fP = 0.20 +/- 0.07, fI = 0.34 +/- 0.16, F/VP = 2.4 +/- 0.7 min(-1), and KPS/VP = 0.86 +/- 0.62 min(-1)) agreed reasonable well with literature data. Best separation between malignant and benign lesions was obtained by the ratio KPS/F (0.35 +/- 0.17 vs. 1.23 +/- 0.65). The functional imaging technique presented appears promising to quantitatively characterize tumor pathophysiology. Its impact on diagnosis and therapy management of breast tumors, however, has to be evaluated in larger patient studies.

Breast Neoplasms↗

PubMed1975

Structural and functional characteristics of the microcirculation in neoplasms.

The microcirculation in a transplantable rat fibrosarcoma was investigated. The vasculature of the neoplasm consisted of irregular channels lined by plump endothelium which displayed mainly pentalaminar although a few heptalaminar junctions were also found. Few pericytes surround the endothelial layer while the basement-membrane varied in thickness and was often duplicated and triplicated. Challenge with histamine resulted in increased permeability in comparison with normal connective tissues similarly treated. The increased permeability was accompanied by the formation of interendothelial gaps in these irregular vascular channels. Carrageenan induced a leucocytic exudate in the neoplasm which, apart from an increase in the mononuclear concentration 2 wk after injection, varied little from normal connective tissues. It is concluded that the majority of vascular channels in this neoplasm bear some structural and functional relationship to small venules.

Angiography↗