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Results for “Microcirculation”

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At least 55 records · Page 3Linked to original sources

PubMed1976

Effect of ionizing radiation on liver microcirculation and oxygenation.

Platelet aggregation and adhesiveness, as well as TPO2 responses to hypoxia were measured as microcirculation parameters in beagle dogs subject to Co60 ionizing radiation to a dose of 4600 rads in 5 weeks. Simultaneously, changes in blood chemistry and coagulation were also determined. Marked changes in all studied parameters in the post radiation period lead to the conclusion that radiation liver damage is at least in part mediated through microcirculation disturbances.

Animals↗

PubMedDate not supplied

Prevention of ionizing radiation-induced liver microcirculation changes by the use of flow improvers.

Platelet aggregation and adhesiveness, as well as TpO2 responses to hypoxia were measured as microcirculation parameters in beagle dogs subject to Co60 ionizing radiation to a dose of 4600 rads in 5 weeks. Simultaneously, changes in blood chemistry and coagulation were also determined. Marked changes in all studied parameters in the post radiation period lead to the conclusion that the radiation liver damage, which is at least in part mediated through microcirculation disturbances, can be prevented with the flow improver, Rheomacrodex.

Animals↗

PubMed1992

A new model of equilibrium dysfunction in the rat induced by photochemical damage to the inner ear's microcirculation.

A new photochemical method was employed to damage the inner ear microcirculation in the rat. Under pentobarbital anesthesia, the middle ear was exposed by a ventral approach and the tympanic membrane and the malleus and incus were removed. The vestibule was then illuminated by a filtered xenon light (wave length: 540 nm) while rose bengal was infused intravenously. Microscopic examination revealed disintegration of the hair cells in the vestibule. Changes could be prevented by pretreatment with intravenous acetylsalicylic acid (ASA) or heparin. Twenty-four hours after the completion of photo-illumination the rats exhibited nystagmus toward the intact ear and showed rolling during the swimming test, both signs of equilibrium dysfunction. These findings were inhibited by ASA or heparin pretreatment. Our present results indicate that our method causes a photochemically induced occlusion in the rat's inner ear microcirculation and may be useful for evaluating the various effects of drugs on the inner ear.

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↗

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↗

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↗

PubMed1992

The acute effect of cigarette smoking on the microcirculation of a replanted digit.

Thirty-one patients who had undergone digital replantation or revascularization volunteered to participate in a study of the acute effect of smoking on the microcirculation of the skin of replanted fingers. Fourteen were smokers and 17 were nonsmokers at the time of the study. Blood flow was assessed by means of the laser Doppler flowmeter under standard conditions. Each smoker inhaled 2 cigarettes. During smoking of the first and second cigarettes a mean decrease in laser Doppler flow of 8% and 19%, respectively, was found, whereas the nonsmokers showed a slight increase of 4% and 4%, respectively. Ten minutes after the last cigarette almost no recovery could be detected. The negative effect of smoking on the microcirculation in replanted digits proved to be more pronounced in the patients operated on more recently. This experiment confirms that smoking after replantation surgery should be prohibited to guarantee optimal circulation.

Adult↗

PubMed1991

Changes in cutaneous microcirculation, hemorrheology and platelet aggregation function in dermatomyositis.

Marked disturbance of microcirculation was observed in 85 cases of dermatomyositis: decrease in number and irregular pattern of the capillaries, many being tortuous and dilated and having a slow and granular blood stream, as well as an increase of vascular permeability. The changes were more marked in cases with visceral disorders, or in active disease; however, there was no correlation between these changes and the duration of illness. Blood hyperviscosity was found in an hemorrheological study. The cause is considered to be due to high plasma viscosity, high fibrinogen levels, and increase of aggregation of erythrocytes and platelets. Modulation of microcirculation is advisable in the treatment of dermatomyositis.

Adolescent↗

PubMed1992

Real-time measurement of microcirculation of skin by reflectance spectrophotometry.

A reflectance spectrophotometric measurement was developed to analyze the microcirculation of the skin in real time. The relative absorption (RA) spectra were obtained from skin tissue 10 times per second using a spectro-multi-channel-photodetector system. In this system, white light was projected onto the skin of the back of the anesthetized rat and the spectrum of the reflected light between 450 and 643 nm was analyzed. Two absorption peaks at wavelengths of about 540 and 577 nm were observed, corresponding to the absorption peaks in the oxyhemoglobin (HbO2) spectrum. Either phlebotomy or the i.v. injection of norepinephrine (NE) reduced the RA spectrum. Peaks of the reduction in spectrum [(RA spectrum before the treatment) - (RA spectrum after the treatment)] were observed at about 540 and 577 nm. Injection of NE (0.75-48 ng/100 g B.W., i.v.) reduced the RA value at 577 nm dose-dependently, suggesting a decrease in the skin blood flow due to vasoconstriction. In addition, the content of HbO2 and capillary permeation were measured at the same time after the i.v. injection of Evans blue (EB) dye. As indices of HbO2 content and capillary permeation, RA changes at 540 and 610 nm (the latter is an absorption peak in the EB spectrum) were measured in real time, respectively. Both RA values increased dose-dependently after the intradermal injection of histamine (0.3-100 micrograms/site), suggesting the presence of vasodilation and an increase in permeability. The time at which the RA value for HbO2 reached a maximum was shorter than that for EB. These observations suggest that the method described here can detect changes in the HbO2 content and permeation of skin microcirculation at the same time, and in real time.

Animals↗

PubMed1992

Acetylcholine induces vasoconstriction in the microcirculation of cardiomyopathic hamsters: reversal by L-arginine.

The goal of this study was to determine whether endothelium-dependent responses of the microcirculation are altered during cardiomyopathy. We examined in vivo responses of cheek pouch arterioles to an endothelium-dependent agonist (acetylcholine) and an endothelium-independent agonist (nitroglycerin) in normal and in cardiomyopathic hamsters. In normal hamsters, acetylcholine produced dose-related dilatation of arterioles. In contrast, acetylcholine produced constriction of arterioles in cardiomyopathic hamsters. Nitroglycerin produced similar dose-related dilatation in normal and cardiomyopathic hamsters. We also examined whether impaired responses to acetylcholine in cardiomyopathic hamsters were related to an alteration in the L-arginine/nitric oxide pathway. We found that L-arginine (100 microM) restored endothelium-dependent vasodilatation to acetylcholine in cardiomyopathic hamsters. Thus, cardiomyopathy impairs endothelium-dependent responses of the microcirculation which is reversed by L-arginine.

Acetylcholine↗

PubMed1992

Nailfold microcirculation in normotensive and essential hypertensive subjects, as assessed by video-microscopy.

OBJECTIVE: To compare morphological and hemodynamic parameters of skin microcirculation in the fingertip in patients with essential hypertension and normotensive control subjects. DESIGN: Consecutive sample of patients. METHODS: Digital capillary blood flow measurements under normal and cooled conditions were assessed by nailfold video capillaroscopy using the technique of flying spot. RESULTS: There was a significant reduction in capillary density in hypertensive patients, compared with normotensive subjects. There was a correlation between capillary density and mean diastolic blood pressure. After local cooling the frequency of the blood flow stop was significantly higher in hypertensive patients. CONCLUSION: The finding of abnormal vasoconstriction in finger microcirculation in essential hypertension suggests a vasospastic tendency in the disease.

Blood Flow Velocity↗

PubMed1990

Persistent arteriolar constriction in microcirculation of the terminal ileum following moderate hemorrhagic hypovolemia and volume restoration.

A stable in vivo preparation of moderate hypovolemia with prompt volume restoration was produced in anesthetized rats. The microcirculation of the terminal ileum was observed in vivo videomicroscopy, and changes in mean arterial pressure (MAP) as well as arteriolar diameters were recorded after a 30-min period in which the MAP was reduced by 50% by bleeding. Volume was restored with shed blood alone (control); dextran 70 alone (dextran); or dextran + hypertonic (7.5%) saline (dextran + HS). A final group of rats was pretreated with allopurinol 5 mg/kg and then treated identically to the control group to assess the role of the xanthine oxidase system in microcirculation changes following hemorrhage. MAP was restored to normal by return of shed blood in control animals, but inflow arterioles (A1) remained significantly constricted. MAP was significantly higher and A1 arteriolar dilation was observed in the dextran + HS group. Responses in allopurinol-pretreated animals were not different from the responses seen in control animals. We conclude that persistent arteriolar constriction is produced by moderate hypovolemia and this effect is ameliorated by volume restoration with dextran + HS.

Allopurinol↗

PubMed1992

The impact of arterialization on hepatic microcirculation and leukocyte accumulation after liver transplantation in the rat.

This study investigated the influence of hepatic arterialization on early graft function, microcirculation, and leukocyte-endothelial interaction after syngeneic orthotopic liver transplantation in Lewis rats. Livers were preserved for 17 hr in UW solution and transplanted without rearterialization (group 1: n = 10) or with immediate arterial reconstruction (group 2: n = 10). Graft function was analyzed by bile flow; microcirculation was assessed by laser Doppler flowmetry (LDF) and intravital microscopy (IVM). In addition, flow behavior of leukocytes was quantified by IVM after i.v. injection of the WBC marker acridine orange. Improved graft function in group 2 was indicated by increased bile production during the observation period of 90 min after reperfusion (7.18 +/- 0.62 vs. 3.63 +/- 0.63 ml/100 g liver [mean +/- SEM] P < 0.001). In arterialized grafts LDF values increased by 22.9 +/- 3.8% upon reperfusion of the hepatic artery (P = 0.004). Arterialization increased WBC velocities in sinusoids (group 1: 0.29 +/- 0.02 mm/sec, group 2: 0.34 +/- 0.01 mm/sec, P < 0.001) and postsinusoidal venules (0.43 +/- 0.05 vs. 0.64 +/- 0.05 mm/sec, P = 0.029). In addition, the number of nonperfused midzonal sinusoids decreased significantly (8.5 +/- 2.2% of all sinusoids analyzed vs. 4.2 +/- 1.3%, P = 0.048). However, the marked sinusoidal and venular WBC adherence observed 1 hr after reperfusion was not altered by arterialization. It is concluded that arterial reconstruction in rat liver transplantation improves microvascular perfusion and graft function but this improvement does not relate to WBC accumulation within the graft. We propose that studies on hepatic preservation and postischemic reperfusion in the rat should be based on the physiological model of dual vascularization.

Animals↗

PubMed1976

Ultrastructure of the human dermal microcirculation: the horizontal plexus of the papillary dermis.

Electron microscopy was used to define the ultrastructure of the various segments of the human cutaneous microcirculation in normal forearem skin. The organization of the vessels in the horizontal plexus of the papillary dermis was reconstructed from 1-mum plasticembedded sections. Ultrathin sections were taken at 10- to 20-mum intervals over a distance of 450 mum. Arterioles were followed through the capillary bed to their venous connections. Terminal arterioles, arterial and venous capillaries, and postcapillary venules were identified on the basis of size, cellular composition of their walls, and their relationship to the other segments of the microvascular bed. The arterial segments were characterized by a homogeneous basement membrane and the venous segments by a multilaminated basement membrane. The elastic lamina in the arterioles was a discontinuous layer which gradually disappeared from the arteriolar wall to form an external sheath just before the arteriole connected with the arterial capillary segment. The vascular walls varied from 1 to 5 mum in all of the segments of the microvascular bed. Criteria are proposed for identifying the various segments of the microcirculation so that their roles in dermatoses and vascular malformations can be evaluated.

Basement Membrane↗

PubMed1975

Histamine receptors in the synovial microcirculation.

This study was designed to investigate the respective roles of H(1) and H(2) receptors in the control of the microcirculation by examining the effectiveness of the H(2) receptor antagonist metiamide (Met.) and H(1) receptor antagonist mepyramine is blocking the action of histamine on synovial perfusion. Synovial perfusion was monitored indirectly by calculating the half-life (T1/2 min.) of the clearance rate of 133-Xe from canine diarthrodial joints. The 133-Xe clearance rate, unaffected by metiamide alone, was consistently increased by histamine alone. Metiamide produced a dose related effect on the histamine response with consistent abolition of response at high dose ratios of metiamide to histamine variable response at intermediate and a pronounced histamine response at low dose ratios. Mepyramine produced no such antagonism of the histamine response and in certain doses, by itself caused an increase in 133-Xe clearance rate. This effect of mepyramine was thought to be related to its histamine releasing properties a view supported by the reduction in this vasodilator response following certain doses of metiamide. The response of the 133-Xe clearance rate to histamine returned approximately one hour after treatment with metiamide (500 mug) and metiamide did not antagonise the effects of alpha and beta adrenergic agents on the 133-Xe clearance rate. Thus, this study has provided evidence for the presence of H(2) but not H(1) receptors in the synovial microcirculation.

Animals↗

PubMed1991

Does unilateral orchidectomy influence blood flow, microcirculation and vascular morphology in the remaining testis?

Adult rats were hemi-orchidectomized and various aspects of testicular blood flow, microcirculation and vascular morphology were studied in the remaining testis after 30 days and compared to that in intact sham-operated animals. Testis weight, total testicular blood flow (measured with microspheres), capillary blood flow pattern (studied with laser Doppler flowmetry) and the volume of interstitial fluid in the testis (index of vascular permeability) were all unaffected by hemi-orchidectomy. Morphometric measurements on perfusion-fixed testicular tissue showed that the volume densities of Leydig cells, blood vessels and small exchange blood vessels were increased by hemi-orchidectomy (by approximately 45, 33 and 42%, respectively). The volume density of Leydig cells in individual testes was correlated to the volume and surface density of capillaries + small postcapillary velules (r = 0.72 and 0.86, respectively). Hemi-orchidectomy is known to result in a doubling in testosterone secretion per Leydig cell. This increased endocrine activity results in moderate increase in the vascular exchange area but other aspects of testicular microcirculation and blood flow are apparently unaffected.

Animals↗

PubMed1992

Aetiology of diabetic foot ulceration: a role for the microcirculation?

Neuropathy, mechanical stress, and macrovascular disease are involved in the pathogenesis of diabetic foot ulceration. Implicit in the development of gangrene and ulceration is the recognition that these factors interact with the microcirculation, resulting in the failure of skin capillary flow to meet nutritive requirements. There is little evidence to associate structural microangiopathy with foot microcirculatory failure. Significant functional abnormalities of the microcirculation have been defined. In accord with the haemodynamic hypothesis early hyperaemia and capillary hypertension promote more sinister late functional abnormalities with increasing duration of diabetes. These late functional abnormalities include loss of autoregulation and reduced hyperaemic responses which interact with loss of neurogenic flow regulation, disturbed endothelial function, and abnormal rheology to produce the familiar clinical picture of the diabetic foot. Ischaemia secondary to multi-segment arterial disease induces additional abnormalities of microcirculatory function which are superimposed on the pre-existing diabetic microvascular structural and functional microangiopathy.

Diabetic Angiopathies↗

PubMedDate not supplied

A contribution to the physiology of the perilymph. Part IV: Effect of histamine on the cochlear microcirculation.

Summary--Because of the topography of the perilymphatic vascular network, the cochlear microcirculation is especially sensitive to the effect of vasoactive substances reaching the perilymphatic space. The cochlear microcirculation is mainly controlled humorally, via the activity of the metarterioles and changes in the flow properties of the blood. Intracochlear histamine reduces the cochlear circulation even more markedly than after intracarotid administration. No systematic effects of parenteral administration of vasoactive substances can be expected on the cochlear circulation. Reversible auditory disorders after stapedectomy may be explicable by the intracochlear release of histamine. The internal release of histamine after sunstroke and cold stress may play a part in sudden dusturbances of hearing.

Animals↗