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At least 595 records · Page 33Linked to original sources

PubMed1986

A novel method for follow-up studies of the microcirculation in non-malignant tissue implants.

Specimens of syngeneic spleen, myocardium, and spongious bone as well as lyophilized dura were implanted into a dorsal skinfold chamber of hamsters. Using intravital microscopy and quantitative video-image analysis, the formation of the implants microcirculation was observed for 2 weeks. The steps of revascularization were similar for spleen, myocardium, and spongiosa: After initial bleeding into the implants (12-54 h), the specimens cleared up and revealed small channels devoid of blood cells (diameter 2-5 microns) 3-4 days after implantation. After 3-5 days blood flow could be observed throughout the specimens. Despite these similarities, the evolving angioarchitecture was specific for each tissue. In contrast, dura specimens were not vascularized. Histology of the implants revealed characteristic structures of the original organs 10-15 days after implantation. It is concluded that the hamster dorsal skinfold chamber provides a suitable host tissue for syngeneic implants. By this procedure, the study of the microcirculation of remote or unpredictably moving organs becomes possible over prolonged periods of time.

Animals↗

PubMed1976

Thrombus formation, hemostasis, adhesiveness of leukocytes and morphological abnormalities in the microcirculation of adjuvant arthritic rats.

Microcirculatory alterations which may be responsible for the chronicity of adjuvant-induced arthritis in the rat were investigated. Thrombus formation in the mesenteric microcirculation was investigated by laser-technique. In arthritic rats thrombus formation for a given stimulus was increased significantly and a correlation was found between the intensity of the arthritic changes and this thrombotic reaction. Adherence of leukocytes to the venous endothelium was studied by an in vivo technique. The number of "rolling" and "sticking" leukocytes was greatly increased in the mesenteric venules of arthritic rats. Acute treatment of severely arthritic rats with aspirin greatly reduced the increased adhesiveness of granulocytes. By the use of an atraumatic technique for vital microscopy of the microcirculation of skin of arthritic rats, striking morphologic changes with stasis of erythrocytes were observed. Morphological aberrations were also found in the mesenteric microvessels of diseased animals.

Adhesiveness↗

PubMed1996

Adrenergic receptors in the forehead microcirculation.

The presence of alpha- and beta-adrenoceptors in the forehead microcirculation was investigated in 49 healthy subjects. Local vascular responses to noradrenaline, isoprenaline and adrenergic antagonists, administered transcutaneously by iontophoresis, were monitored via laser Doppler flowmetry. Iontophoresis of the alpha-adrenergic antagonist phentolamine induced a persistent increase in skin blood flow, whereas iontophoresis of saline induced a minor increase in skin blood flow which subsided rapidly. Skin blood flow increased moderately after the iontophoresis of the beta-adrenergic antagonist propranolol. Pretreatment of the experimental site with phentolamine blocked the normal vasoconstrictor response to noradrenaline, and unmasked a minor vasodilator component of response in some subjects. Iontophoresis of the beta-adrenergic agonist isoprenaline induced dose-dependent vasodilatation which was antagonised by propranolol. These findings indicate that alpha-adrenoceptors in the forehead microcirculation normally mediate a vasoconstrictor response to iontophoretically-applied noradrenaline. In addition, beta-adrenoceptors appear to mediate a minor vasodilator component of response.

Adolescent↗

PubMed1999

Dual-beam laser illuminator of fluorescence microscope for in vivo microcirculation studies.

A new fluorescence intravital microscope of long working distance (39 mm) has been developed for the observation of microcirculation in a wide visual field by designing a simple epi-illumination technique with dual laser beams. Cross-illumination, in which a pair of laser beams is symmetrically placed on either side of the objective such that they intersect at the focal plane of the objective, was employed to produce uniform distribution of the incident light in the object plane. In vitro experiments using a fluorescein isothiocyanate dextran (FITC-dextran; molecular weight = 70,000) solution of known concentration confirmed uniform tracer excitation in a wide visual field (approximately 30 mm2), and a linear correlation between fluorescence intensity and tracer concentration (r = 0.999), ranging between 5 mumol l-1 and 25 mumol l-1. In vivo observations in the microcirculation of a hamster cheek pouch indicated that the present technique had the advantage of high contrast compared with the image obtained by bright-field transillumination. This microscope illuminator may prove useful for the evaluation of vascular permeability under physiological and inflammatory conditions, with sufficient quantitative reliability to determine tracer concentrations in all parts of the microvascular network. Furthermore, a long working distance in this technique could have considerable advantages for the application to nail-fold capillaroscopy in humans.

Animals↗

PubMed1983

A simple model for simulation of oxygen transport in the microcirculation.

A mathematical model of deoxygenation of blood in the microcirculation is used to estimate the mass transfer resistance in the blood and to examine certain assumptions used in prior work on simulation of the microcirculation: the treatment of blood as a continuum and the use of a single-step reaction kinetics model. The erythrocytes are treated as cylindrical slugs which alternate with plasma gaps such that oxygen transport is by radial diffusion in the cell. The system of equations including reaction kinetics and oxyhemoglobin diffusion is solved numerically. The results are of direct applicability in estimation of oxygen concentration profiles in tissue. The results also indicate that the resistance to oxygen transport in the capillary (relative to that in the surrounding tissue) is much higher than predicted by the continuum approach used by most prior workers. The resistance in the capillary is a significant fraction of the overall resistance. Other results give quantitative estimates of the error incurred from use of a single-step kinetic model.

Biological Transport↗

PubMed1979

Are epinephrine and gastrin accelerative factors of acute cinchophen ulcer?: Studies on gastric mucosal microcirculation and gastric secretion.

Measurements of serum epinephrine and gastrin, simultaneously, gastric mucosal blood flow and gastric secretion were carried out in cinchophen treated dogs. No significant changes in either serum concentrations of epinephrine and gastrin or fundic mucosal microcirculation after a single 100 mg/kg cinchophen administration were found while gastric secretion increased markedly after the medication. On the other hand, a significant increase in serum epinephrine and gastrin levels was observed while gastric secretion decreased significantly after large doses of cinchophen (300 mg/kg) were injected intravenously. Here gastric mucosal microcirculation is decreased. Repeated administration of 100 mg/kg cinchophen for 3 to 7 days brought about an increase in epinephrine and gastrin levels and caused an occurrence of fundic mucosal hemorrhage. Sympathetic discharge and gastrin release were not seen after a 3-week period of cinchophen administration. Cinchophen ulcers were produced, even when contact between the bile and the stomach mucosa was avoided. Vagotomy had no connection with ulceration and gastric secretion.

Animals↗

PubMed1995

Differential microcirculation dynamics during deliberate hypotension induced by nicardipine, PGE1 and trimethaphan in rat mesentery.

The purpose of this study was to determine the arteriolar changes that occur in the microcirculation during deliberate hypotension and general anaesthesia and whether the changes depended on the drugs used to induce vasodilatation or on the degree of systemic blood pressure decrease. Changes in the vessel diameter and the velocity of red blood cells in the mesenteric arterioles of pentobarbitone-anaesthetized rats were observed using continuous biomicroscopy. Observations were made during deliberate moderate (BP 70 mmHg) or deep (BP 50 mmHg) hypotension by titration with nicardipine, prostaglandin E1 (PGE1) or trimethaphan. Then, the responses of arterioles to locally applied noradrenaline (1 microgram) were assessed. During moderate hypotension PGE1 decreased the arteriole diameter slightly (16.7 +/- 1.6 to 14.7 +/- 1.3 microns, P < 0.05), reduced the velocity of red blood cells considerably (1.98 +/- 0.2 to 1.03 +/- 0.4 mm.sec-1, P < 0.05) and increased the contractile response of arterioles to locally-applied noradrenaline. Nicardipine and trimethaphan had no effect on the microcirculation. During deep hypotension, all drugs decreased the diameter of the arterioles slightly but reduced the velocity of red blood cells considerably (P < 0.05). We conclude that the major change in the mesenteric arterioles during deliberate hypotension during general anaesthesia is a decrease in red blood cell velocity that is dependent on the drug used and the degree of blood pressure decrease.

Alprostadil↗

PubMed1999

Functional characteristics of the coronary microcirculation.

For over 50 years, it has been recognized that coronary blood flow is precisely matched to cardiac metabolism. The interactions which govern this matching remain unknown. In the current review, 3 specific aspects of coronary flow regulation will be discussed: Specialization of function in different microvascular domains, influence of cardiac region on microvascular function and the interactions of vasoactive agents in control of coronary blood flow. Each level of the coronary microcirculation is affected by different physical and chemical forces within the heart. These forces place special demands on these vessels and are in turn met by specialized vasodilator responses, including metabolic and flow-mediated vasodilation. Perfusion of the heart is also profoundly affected by the region perfused. The endocardium is affected by forces, notably cardiac contraction, in a different manner than the epicardium. Thus, the microcirculation has specialized to meet these demands. Finally, the factors determining microvascular tone appear to be coordinated such that the loss of any individual dilator, such as nitric oxide, can be compensated for by the increased contribution of another, such as adenosine. This interplay may serve to protect the heart from ischemia during the early phases of coronary vascular disease when individual dilators may be impaired.

Animals↗

PubMed2002

Protective effect of ketoprofen lysine salt on interleukin-1beta and bradykinin induced inflammatory changes in hamster cheek pouch microcirculation.

OBJECTIVE: The purpose of this study was to assess the efficacy of topically applied ketoprofen lysine salt (KLS), a cyclooxygenase inhibitor, against the inflammatory changes induced by interleukin-1beta (IL-1beta) and bradykinin (BK) in hamster cheek pouch microcirculation. In addition, we characterised the pharmacological regulation of IL-1beta activity in this model. MATERIALS AND METHODS: Male Syrian hamsters were used. Microcirculation was visualised by fluorescent microscopy. Leukocyte adhesion, permeability, perfused capillary length (PCL) and capillary red blood cell (RBC) velocity were evaluated. TREATMENTS: KLS (25 microg/ml/min to 1.6 mg/ml/min) was topically applied for 3 min before topically administered IL-1beta (1microg/ml) and BK (10(-4) M). Monoclonal anti-mouse IL-1beta receptor antagonist (200 ng/ml), BK-B2 receptor antagonist (10(-6) M), PAF inhibitor (10(-5) M) and cycloheximide (10 microg/ml) were added topically 15, 10, 15 and 60 min, respectively, before IL-1beta (1 microg/ml). RESULTS: IL-1beta caused a significant increase in microvascular permeability, a decrease in capillary RBC velocity followed by increased leukocyte adhesion in postcapillary venules. BK caused a marked increase in leukocyte adhesion and no decrease in PCL and RBC velocity. Treatment with KLS significantly inhibited both the leukocyte adhesion and microvascular leakage induced by the two mediators. The inflammatory effects induced by IL-1beta were reduced by blockade of IL-1beta receptors and by a BK-B2 receptor antagonist but were not affected by a PAF antagonist and protein synthesis inhibition. CONCLUSIONS: These results demonstrate that KLS is effective in preventing early inflammatory changes induced by both IL-1beta and BK in the capillary network. Prostaglandin release and BK are essential components for IL-beta mediated responses, whereas neither PAF nor new protein synthesis appear to be linked to the early inflammatory changes induced by IL-1beta.

Animals↗

PubMed2002

[Orthogonal polarization spectral imaging--a new clinical method for monitoring of microcirculation].

The orthogonal polarization spectral (OPS) imaging technology is a new non-invasive method to directly visualize multiple conditions of the microcirculation which has several clinical applications in humans. Quantitative measurement of the diameter of vessels, the velocity of red blood cells and functional capillary density (FCD) can be made. Activation of leukocytes can be monitored and also quantified. A transdermal approach can be used in premature babies and neonates to view the microcirculation and has also been used experimentally to determine haemoglobin levels. The application to various surfaces and solid organs allows a variety of pathophysiologies and phases to be examined.

Blood Flow Velocity↗

PubMed2004

[Main determinants of liver microcirculation during systemic inflammation].

More than 50% of all patients on intensive care units acquire a systemic inflammation such as systemic inflammatory response syndrome (SIRS) or sepsis. The development of hepatic microcirculatory failure with consecutive organ damage might occur during the course of the systemic inflammation. The liver microcirculation is regulated by a complex network of cellular components and specific mediators. The perfusion in liver sinusoids is regulated by the tonus of the contractile Ito cells. Nitric oxide (NO) and carbon monoxide (CO) influence each other and cause the Ito cells to dilate while endothelin results in a contraction of the Ito cells. On-going studies are investigating the role of angiotensin II, catecholamines and prostaglandins for the regulation of the hepatic microcirculatory system during systemic inflammation. Some investigations aim to determine the impact of sedatives and analgesics on the hepatic microcirculation in sepsis and SIRS. Therefore, a decisive recommendation about the choice and dosage of sedatives and analgesics for these patients is not possible. Nevertheless, ketamine, midazolam and fentanyl with their potential anti-inflammatory properties seem to be suitable for patients with systemic inflammation.

Humans↗

PubMed1998

[Microcirculation research in experimental surgery].

The microcirculation is the organ that provides the direct link between blood and tissue, and thereby between the whole organism and the single cell. Modern microcirculation research in experimental surgery is characterized by the use of high-resolution video fluorescence microscopy and quantitative computer-assisted image analysis coupled with the techniques of molecular biology and transgenic or knockout gene technology. These advances should improve knowledge about surgically relevant physiologic and pathophysiologic phenomena at the interface between blood and tissues and help us to understand the initial molecular mechanisms leading to organ dysfunction following inflammation, ischemia-reperfusion, and transplantation.

Animals↗

PubMed1997

[The effect of compression therapy on the microcirculation of the skin in patients with chronic venous insufficiency (CVI)].

Compression therapy was employed for 4 weeks 20 patients with chronic venous insufficiency stage CVI I and CVI II according to Widmer's classification. Compression bandaging for 2 weeks was followed by compression stockings for 2 more weeks. The cutaneous microcirculation was evaluated before therapy, after 2 weeks and after finishing compression therapy after 4 weeks. Marked improvement in symptoms such as pain and itching was observed after 4 weeks, along with a significant reduction in lower limb volume. Video capillary microscopy revealed an increase in capillary density associated with a decrease in capillary diameter and pericapillary halo diameter. Compression treatment achieves at least part of its effect by improving the function of the skin microcirculation. The efficacy of bandaging and stockings was similar.

Bandages↗

PubMed1997

[Treatment of venous ulcers with low frequency pulsed current (Dermapulse): effects on cutaneous microcirculation].

Chronic venous insufficiency (CVI) is characterised by stage-dependent microangiopathy. With increasing severity there is a decrease in the number of skin capillaries and the oxygen partial pressure. The cutaneous vascular reserve, which is measured by laser-doppler fluxmetry, is reduced. Cutaneous microangiopathy is one of the main causes of the trophic disturbances associated with CVI. Low frequency pulsed current improves cutaneous microcirculation and thus nutrition as well as accelerating the formation of granulation tissue. In a open prospective pilot study, 15 patients suffering from CVI with persistent leg ulcers were treated with low frequency pulsed current (Dermapulse), which is thought to improve particularly the tissue microcirculation. The average age of the patients was 70.3 years and the average duration of ulceration was 79.1 months. The patients were treated over a period of 38 days. With this treatment, 2 ulcers healed completely and 13 showed a reduction of size of on average 63%. Capillary density increased by 43.5%, while transcutaneous oxygen partial pressure increased by 82.4%. Electrostimulation is a treatment with few or no side effects.

Aged↗

PubMed2002

[Dynamic contrast-enhanced MRI for evaluating bone marrow microcirculation in malignant hematological diseases before and after thalidomide therapy].

PURPOSE: The aim of the study was to measure microcirculation parameters by dynamic contrast-enhanced MRI (d-MRI) and to evaluate the anti-angiogentic effects during treatment with thalidomide in different hematologic malignancies. METHODS: In 20 healthy normal persons, 20 patients with myelodysplastic syndromes (MDS), 10 patients with multiple myeloma (MM) and 10 with myelofibrosis (MF) a fast gradient echo sequence (Turbo fast low angle shot 2D) with a pump controlled bolus infusion of gadolinium-DTPA was performed before and in 18 of these after beginning (average of 4.3 months) of a thalidomide therapy. Two pharmacokinetic parameters--the amplitude and exchange-rate-constant--were calculated and a statistical comparison of these values between healthy persons and patients as well as a correlation with the clinical course was executed. RESULTS: Compared with the normal controls the patients showed a higher amplitude (normal persons 14.4 +/- 5.2, MDS 24.8 +/- 8.1, MF 35.9 +/- 4.3, MM 23.4 +/- 3.6) and exchange-rate-constant (normal persons 0.124 +/- 0.042, MDS 0.136 +/- 0.036, MF 0.144 +/- 0.068, MM 0.131 +/- 0.034). In the d-MRI-follow-up examinations a significant (p < 0.005) reduction of the amplitude and exchange rate constant values was evident in 14 of 18 patients undergoing a thalidomide therapy. Clinically all of these patients showed a therapy responding with complete or partial diseases remission. CONCLUSIONS: In patients with hematologic malignancies significantly higher d-MRI-microcirculation parameters of the lumbar spine can be demonstrated than in normal persons. During anti-angiogenetic treatment with thalidomide a decrease of these values was observed in case of a responding to therapy.

Adult↗

PubMed2002

The effect of polyneuropathy on foot microcirculation in Type II diabetes.

AIMS/HYPOTHESIS: The aim of this study was to investigate the influence of peripheral polyneuropathy (PNP) on skin microcirculation and foot swelling rate in the feet of patients with Type II (non-insulin-dependent) diabetes mellitus. METHODS: 38 Type II diabetic patients, 24 with PNP (PNP+), 14 without PNP (PNP-), and 16 healthy control subjects were studied, first supine and subsequently sitting with the foot dependent for 50 mn. RESULTS: In patients with PNP, foot skin temperature was higher, (p<0.04) and capillary blood cell velocity (CBV, nailfold capillary microscopy), was lower compared to patients without PNP (222 vs 313 micro m/s respectively, p<0.03). Compared to the control subjects, the percentage reduction in skin blood flux, (LDF, laser-Doppler fluxmetry), after 10 min was higher in the PNP- and PNP+ patients (3% vs 18% and 26% respectively, p<0.02). These disturbances were most pronounced in PNP+ patients with a history of a foot ulcer. Foot swelling rate (mercury strain gauge plethysmography) in the first 10 min of dependency, was lower in patients with PNP+ compared to the control subjects (0.00165 vs 0.00286 ml.100 ml(-1)s respectively, p<0.01). In addition, we found a negative correlation (r=-0.41; p<0.01) between Valk-score (severity of PNP) and FSR. CONCLUSION/INTERPRETATION: Type II diabetes PNP is associated with multiple abnormalities in the (skin) microcirculation of the foot, characterised by reduced capillary blood flow, an enhanced reduction in skin blood flux and impaired fluid filtration after sitting up. The most severe abnormalities were observed in patients with a history of foot ulceration.

Adult↗

PubMed2004

Ischemic preconditioning fails to improve microcirculation but increases apoptotic cell death in experimental pancreas transplantation.

Brief periods of warm ischemia and subsequent short reperfusion before either long-term cold or warm ischemic insult (ischemic preconditioning, IPC) have proven to ameliorate ischemia/reperfusion (I/R) injury in various organs, such as the liver and lung. The aim of this study was to examine the effect of IPC on pancreatic cell apoptosis and microcirculatory impairments in experimental pancreas transplantation. Male Lewis rats served as donors and recipients of heterotopic syngeneic pancreaticoduodenal transplantation. Recipient animals were divided into two experimental groups: group Tx (n=7) received grafts without IPC, group Tx&IPC received grafts with IPC. Animals that had not undergone transplantation but whose pancreata had been exteriorized served as controls (n=5). All pancreatic grafts were preserved in University of Wisconsin solution for 6 h at 4 degrees C. IPC was induced by interruption of the arterial blood flow for 10 min followed by 10 min of reperfusion. One and two hours after reperfusion, graft microcirculation was assessed by means of intravital microscopy (IVM). Rats were immediately killed after the second measurement and DNA breaks of acinar cells were detected by in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate digoxigenin nick end-labelling (TUNEL) assay and gel electrophoresis (laddering). The apoptotic index (AI) was defined as the number of apoptotic cells per high-power field. Analysis of both groups of transplanted grafts showed a significant decrease in functional capillary density (FCD) and a significant increase in leukocyte sticking to postcapillary venules (LAV) at 1 h and 2 h of reperfusion, compared with animals that had not undergone transplantation ( P<0.01). In parallel, AI was significantly increased in transplanted grafts compared to the controls ( P<0.01). Grafts subjected to IPC showed no significant differences, neither for FCD nor LAV, at both time points if compared with grafts of group Tx. However, IPC resulted in a significant increase in AI ( P<0.05). We can conclude that IPC has no effect on pancreatic microcirculation but enhances acinar cell apoptosis in experimental pancreas transplantation. These results indicate that IPC might increase I/R injury after pancreatic cold ischemia.

Animals↗

PubMed2000

Role of hypotension in brain-death associated impairment of liver microcirculation and viability.

Hypotension in brain-dead organ donors is considered a determinant factor of graft viability. The aim of this study was to elucidate the role of hypotension in brain-death associated impairment of hepatic microcirculation and function. Male Sprague-Dawley rats with an intracranial balloon were used. Group I (n = 7) served as sham controls. In group II (n = 7) brain death was induced through inflation of an intracranial balloon. In group III (n = 7) hypotension without brain death was induced by means of pentobarbital. In group II, a steep rise of arterial pressure was followed by a fall to a lower level (P < 0.01, vs. group I). Also in group III arterial pressure was lower (P < 0.01, vs. group I). In group II, bile production was diminished (P < 0.05). Impaired sinusoidal perfusion (P < 0.01) and enhanced leukocyte endothelium interaction (P < 0.05) were documented in hepatic microvasculature. Electron microscopic analysis revealed vacuolization of hepatocytes; these changes were not observed in group III. Brain death induces specific changes of liver microcirculation, function and histomorphology. Independent of associated hypotension, brain death per se impairs donor liver graft quality.

Alanine Transaminase↗