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Results for “Microcirculation”

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At least 127 records · Page 7Linked to original sources

PubMed1991

In situ testing of CO2 laser on dental pulp function: effects on microcirculation.

The effect of CO2 laser irradiation on pulpal microcirculation was studied in cat canines. The enamel surfaces of 4 teeth were exposed with energy densities of 304-1440J/cm2, using either a handpiece or a microslad, with a focal spot of 0.21mm and 0.33mm respectively. Pulpal blood flow (PBF) before and following lasing was recorded through the intact tooth surface by a laser Doppler flowmeter. CO2 laser irradiation caused an increase in PBF, which was immediate and transient. The PBF increase was higher in a large pulp than in a small pulp, and it was inversely related to the focal spot size. These findings confirm that the dental pulp is thermally affected by CO2 lasing of the tooth surface, however, without extensive pulp coagulation. It is concluded that the effects of laser irradiation on the pulpal microcirculation may be studied in situ by means of the presented methodology.

Animals↗

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↗

PubMed1986

Hepatic microcirculation in Zucker fatty rats.

We have developed a microscopic analyzing system for studying in vivo hepatic microcirculation, and measured the sinusoidal erythrocyte flow velocity simultaneously in the various sinusoids. With this system and organ reflectance spectrophotometry, the pathophysiological role of microcirculation and of energy metabolism in Zucker fatty rats were studied. The results were as follows: The erythrocyte flow velocity in the predominant sinusoids in the fatty rats was similar to that of the control rats, but the intersinusoidal erythrocyte flow was undetected in the fatty liver. Index of regional hepatic blood volume, regional hepatic blood flow and oxygen saturation of Hb decreased significantly in the fatty rats. The estimated in vivo oxygen consumption was not changed in the fatty liver. From these data, it is concluded that in Zucker fatty rats a marked fatty infiltration causes a decreased hepatic tissue blood flow and volume, but relatively homogeneous erythrocyte flow with an increased extraction of oxygen compensated the decreased vascular beds and maintained normal energy metabolism.

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↗

PubMed1990

[Disorders of microcirculation in colon anastomoses and their significance for the pathogenesis of suture dehiscence].

In this morphologic experimental study in the rabbit disturbances in the microcirculation at the site of colonic anastomoses were found in all suture techniques employed. They are caused by resection, intraoperative traumatization, the suture technique, and, secondarily, by abscess formation on the anastomosis. The suture-induced disturbances of the microcirculation lead to necroses of the mucosa, partial and complete necroses of the inverted cuff, and transmural necroses with destruction of the sero-serous contact zone. For the pathogenesis of anastomotic dehiscence only transmural and extensive complete necroses of the anastomotic bulge, including the serosal contact, are important. They result in transmural abscess formations which correspond to microscopic small secondary anastomotic leakages.

Abscess↗

PubMed1989

Effects of Fusobacterium necrophorum on the mesenteric microcirculation of guinea pigs.

Thrombi formation was demonstrated in mesenteric microcirculation of guinea pigs inoculated with Fusobacterium necrophorum and the bacterial hemagglutinin (HA). The thrombi were initially observed in venules and later, in arterioles. Immunofluorescence study revealed that the HA bound to the thrombi in the microcirculation. These results indicate that thrombosis is an early step in the pathogenesis of necrosis.

Animals↗

PubMed1988

The effects of slip velocity at a membrane surface on blood flow in the microcirculation.

Closed-form solutions are presented for blood flow in the microcirculation by taking into account the influence of slip velocity at the membrane surface. In this study, the convective inertia force is neglected in comparison with that of blood viscosity on the basis of the smallness of the Reynolds number of the flow in microcirculation. The permeability property of the blood vessel is based on the well known Starling's hypothesis. The effects of slip coefficient on the velocity and pressure fields are clearly depicted.

Blood Flow Velocity↗

PubMed1987

An investigation of the microcirculation of the human tympanic membrane with laser-Doppler flowmetry.

The present investigation was performed to evaluate the use of laser-Doppler flowmetry as a means for measuring the blood flow of the microcirculation of the human tympanic membrane. The blood cell flux in the microvascular bed of the normal tympanic membrane was measured in healthy subjects. The laser-Doppler output signals continuously recorded showed a steady value ranging from 70 to about 120 V, as well as spontaneous oscillations (or rhythmical active vasomotion). Our findings show that the laser-Doppler instrument tested seems to be useful for evaluating blood flow changes in the microcirculation of the human tympanic membrane.

Adult↗

PubMed1985

Lead-induced permeability changes in immature vessels of the developing cerebellar microcirculation.

The ultrastructure and microcirculatory permeability changes of lead encephalopathy were studied in an animal model using horseradish peroxidase as an intravascular tracer. The fine structure of capillary sprouts in the developing cerebellar microcirculation of lead-poisoned rats were described. Immature vessels, characterized by the presence of endothelial sprouts, were found to have focal areas of endothelial injury with degenerating endothelial cells. These disruptions of the microcirculatory endothelium had tracer extending from the vessel lumen to the surrounding neuropil. The degenerating endothelial cells were found as early as 24-28 h after the first administration of lead acetate by gastric lavage (2-3-day-old rats). The early injury to endothelial cells of immature vessels in the developing microcirculation is suggested as an important component of the vascular permeability changes which characterize lead encephalopathy. Older animals (5-10 days old) had microaneurysmal vascular dilatations which had a complex internal structure formed by endothelial cells. These microaneurysmally dilated vessels may represent an endothelial response to preceding endothelial injury of immature vessels.

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↗

PubMed1985

[Hemorrhagic pancreatitis: effect of dextran 40 and plasma on microcirculation disorders of the pancreas].

A dog model was used to measure the hemodynamic changes occurring during acute pancreatitis induced by intraductal injection of fresh trypsin-bile-blood mixture. Continuous measurements of pancreatic blood flow, cardiac output, mean arterial blood pressure and pancreatic oxygen consumption were made under normal conditions and during acute pancreatitis. All animals received 100 ml of saline/h during the time of observation. Three methods of therapy then were instituted in the dogs starting 30 min after induction of pancreatitis. 10 dogs served as controls (saline 100 ml/h); in 6 dogs additionally 15 ml/kg plasma was infused over 45 min and 6 dogs received 1.5 ml/kg Dextran 40/h continuously. Hemorrhagic pancreatitis was characterized by a fall in cardiac output and mean arterial pressure and the development of severe impairment of the pancreatic microcirculation with early reduction of pancreatic blood flow followed by a fall in pancreatic oxygen consumption. Administration of plasma produced a significant increase in cardiac output; however, blood pressure and pancreatic blood flow remained low. Low-molecular weight Dextran has no influence on cardiac output, but significantly improved the blood pressure and leads to a normalization in pancreatic blood flow and oxygen consumption. These results suggest that low-molecular weight Dextran appears to reverse the impairment of microcirculation and hypoxia of the pancreas and limits the progression from edematous to hemorrhagic pancreatitis and irreversible pancreatic damage.

Animals↗

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↗

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↗

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↗