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At least 919 records · Page 51Linked to original sources

PubMed1999

[Role of microcirculation in hypertension].

A large share of the pressure gradient in the vascular system is situated in the microcirculation. Most of the mechanisms resulting in an increase of peripheral resistances during hypertension are also located in this network. Experimental studies have shown that the functional characteristics of arterioles are profoundly modified in most hypertension models. The sensitivity to vasoconstrictor agonists is increased. The activity of the angiotensin-converting enzyme, situated in the arteriolar wall, is considerably greater in genetically hypertensive animals than in control animals. Endothelium-dependent vasodilator mechanisms are also decreased in these animals, while endothelium-derived vasoconstrictor factors are responsible for an increased smooth muscle response. These functional disorders are associated with structural modifications of the microvascular network. Changes of wall thickness are observed only inconstantly, but an initially functional then anatomical rarefaction of arterioles and capillaries has been observed in most experimental models of hypertension and in several clinical studies. This phenomenon reduces the capacities of adaptation of perfusion condition to changes in metabolic requirements of the various organs, reflecting the fact that the microcirculation is a target of hypertensive disease. Antihypertensive drugs should therefore be assessed not only in terms of the reduction of blood pressure figures, but also in terms of their capacity to prevent or correct structural changes of the microvascular network.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2002

Effect of C-peptide on wound healing and microcirculation in diabetic mice.

AIM: Recent studies have demonstrated that C-peptide is biologically active and might have a beneficial effect on late complications in diabetes mellitus. The aim of this study was to investigate the effects of systemically given C-peptide on dermal wound healing in diabetic mice. METHODS: Experiments were carried out in male SKH-1 hr hairless mice. Dermal wounds were created (diameter 2.5mm) in streptozotozin-diabetic and normal control mice. Mice were randomized into three treatment groups (n = 10 each): Normal controls, diabetic mice with PBS or C-peptide injection twice daily. At various time points (prior wounding as well as days 4, 7, 10 and 15) microcirculation was quantitatively analyzed by intravital fluorescent microscopy to determine wound surface area, vessel diameter, red blood cell velocity, plasma leakage, functional capillary density. In addition, leukocyte/endothelium interaction was quantified by in vivo visualization of leukocytes. RESULTS: Systemic administration of C-peptide showed no influence on wound healing or standard microcirculatory parameters. The leukocyte/ endothelium interaction revealed a significant (p<0.05) increase in the number of adherent leukocytes 15 days after wound creation in C-peptide treated diabetic mice. CONCLUSION: Except for the significantly increased number of leukocytes adherent to venular endothelium in the C-peptide group no alteration was observed in wound healing and microcirculation. Neutrophil recruitment after C-peptide injection is of interest because it may reduce the risk of infection in diabetes mellitus.

Animals↗

PubMed2002

[Experimental study on forms of microcirculation of arterialized venous flap in rabbits].

OBJECTIVE: To study the forms of microcirculation of arterialized venous flap. METHODS: Twenty New Zealand rabbits were equally divided into two groups, arterialized venous flap group (group A) and control group (group B). The microcirculatory haemodynamic of arterialized venous flap was studied through observation of transparent chamber in rabbit's ears with aspecial TV set with manification of 1000. RESULTS: The blood of arterilized venous flap flowed through venule anastomosis and drained to another venule. CONCLUSION: It is the main form of microcirculation in early stage that blood flows from venule to draining venule by way of communicating networks between venules.

Animals↗

PubMed2001

[The effects of safflor yellow on microcirculation and hemorheology of acute blood stasis rats].

OBJECTIVE: To observe the effects of safflor yellow on microcirculation and hemorheology of acute blood stasis rats. METHODS: The acute blood stasis medel was made by i.p. adrenalin (0.07 ml/(kg.time) for 2 times and the stimulation of ice-water. RESULTS: Safflor could markedly improve the number of net dot in microcirculation, and eta b, eta p, eta f in hemorheology (P < 0.05). CONCLUSION: Safflor yellow played an important role on blood stasis of rats.

Animals↗

PubMed2003

[Structural and functional changes of the microcirculation in hypertension: influence of pharmacological therapy].

The increased peripheral resistance in hypertension results from arteriolar vasoconstriction, increased media-to-lumen (M/L) ratio of small resistance arteries, and rarefaction (reduction in density) of microvessels. Numerous neurohumoral and hormonal factors are involved in causing structural and functional changes in the microcirculation in hypertension, including the renin-angiotensin-aldosterone system, remodelling of the extracellular matrix, increased growth of the smooth muscle cells of the media, and elevated collagen and fibronectin deposition. Although a wide variety of pharmacological agents can decrease blood pressure (BP) in hypertension, they vary in their ability to reverse structural and functional changes in the microcirculation. ACE inhibitors have consistently been shown to regress microvascular changes but findings with calcium antagonists have been variable and beta-adrenoceptor blockers appear to have no effect. In studies with ACE inhibitors, improvements in the M/L ratio and endothelial function of small resistance arteries have been recorded in both animal models of hypertension and human subcutaneous arteries obtained by biopsy of gluteal tissue from patients with essential hypertension. Recent studies with the very low-dose combination of perindopril and indapamide have indicated that these agents act synergistically to restore normal microvascularisation and reverse capillary rarefaction in the coronary circulation of hypertensive rats, and normalise coronary blood flow reserve in humans with hypertension. The additional benefit accruing from regression of structural and functional abnormalities in critical vascular beds such as coronary or renal circulations of patients with chronic hypertension may well become an important factor in selection of antihypertensive therapy, as complications such as ischaemic episodes and other target organ damage may be prevented and the BP-lowering effect of treatment may be extended such that it continues even after withdrawal. However, whether improvements in microcirculatory structure and function will be associated with improved morbidity and mortality outcomes in patients with chronic hypertension has yet to be firmly established.

Adrenergic beta-Antagonists↗

PubMed2003

[Restricted microcirculation disorder induced by photochemical reaction in the guinea pig cochlea].

OBJECTIVE: To investigate the effect of restricted cochlear microcirculation disorder on the cochlear blood flow, auditory function, and morphology. METHOD: Photochemical reaction was utilized to induce localized microcirculation damage to the second cochlear turn. After systemic administration of rose bengal, the second cochlear turn was illuminated with green light (wave length 540 nm +/- 40 nm) to cause thrombosis in the stria vascularis, the area was about 1.2 x 1.0 mm2. RESULT: At the site of the illumination, cochlear blood flow gradually decreased, and the threshold of action potential gradually increased. Surface preparing showed thrombus was in the stria vascularis. Three hours after the photochemical reaction, some hair cells in the illuminated area necrotized. The length of the lesion was 1152.50 +/- 363.26 microns (n = 4). But hair cells in the non-illuminated area were normal. CONCLUSION: The photochemical method is a reliable tool to produce an animal model with the restricted microvessel lesion in the lateral wall of the cochlea. It could be used as an animal model for the treatment of the cochlear thrombosis.

Animals↗

PubMedDate not supplied

Study of the microcirculation of oral mucosa in healthy subjects.

The research has the following aims: 1: to verify the applicability of capillaroscopic investigation to oral mucosa; 2: to propose oral mucosa as an alternative to the fingernail fold for capillaroscopic investigation; 3: to describe the characteristics of the microcirculation of oral mucosa in healthy subjects. 100 healthy patients were examined. The characteristics of the micro-circulation in the areas of gum mucosa and the mucosa covering of the lower lip were examined using computerised videomicroscopic techniques. For each patient we evaluated the visibility, the course, the density, the tortuosity and any images characteristic of capillary loops, besides the possible presence of microhaemorrhages, the average calibre of capillary loops and the number of capillary loops visible per square millimetre. The investigation was simple, non invasive and repeatable for each patient. An investigation of gum mucosa has revealed a course of capillary loops both parallel and perpendicular to the surface: often the tops of the capillary loops appear as regularly distributed dots or commas. Microcirculatory architecture in the area of the mucosa covering is characterised by capillary loops with a variable diameter, course and length; next to typical capillary loops with the appearance of horse stirrups, there are other loops similar to hairpins, commas and cork screws; there are also rare microhaemorrhages with the aspect of reddish stains, that could be caused by microtraumas. Visibility was very good in the area of the mucosa covering of the lower lip: mediocre in the area of gum mucosa. Our research has highlighted, that today it is possible to carry out a capillaroscopic investigation of oral mucosa in a simple and reliable way. Future research could evaluate how "normal microcirculation", that we describe in this paper, is modified during pathology

Adult↗

PubMed2003

[Thoracic epidural anesthesia improves the gastric microcirculation during experimental gastric tube formation].

We studied the effects of gastric tube formation and thoracic epidural anaesthesia (TEA) on gastric microcirculation, hemodynamic and bowel motility changes. The experiments were performed on pentobarbital-anesthetized, mongrel dogs. Mean arterial pressure (MAP), gastric and mesenteric blood flow (Transonic Systems Inc.) and small bowel motility changes (strain gauge technique) were monitored. The stomach was prepared according to the method of Akiyama. TEA was induced by injecting Bupivacain 1 mg/kg. Orthogonal polarization spectral imaging (OPS) technique (Cytoscan A/R, Cytometrics, PA, USA) was used to observe in vivo microcirculatory changes. The gastric pull-up caused significant decrease in intramucosal pH and red cell velocity (RBCV) in terminal arterioles of the upper part of gastric tube both on the mucosal and serosal side. After TEA the RBCV returned to baseline level and the intestinal motility index significantly increased. Functional capillary density of the mucosa or subserosa did not change during the experiments. MAP was significantly reduced by 30%, while the arterial blood flow in gastric and mesenteric arteries was significantly increased. TEA significantly improves microcirculation of the distal portion of the gastric tube and increases intestinal motility. These results show that epidural anaesthesia is favourable and should be recommended during reconstructive oesophageal surgery.

Anesthesia, Epidural↗

PubMed2003

[Intra-arterial thrombolysis for the treatment of restricted cochlear microcirculation disorder in guinea pigs].

OBJECTIVE: To ascertain a new treatment method for restricted cochlear microcirculation disorder. METHODS: Photochemical reaction was utilized to induce localized microcirculation damage to the second cochlear turn of every guinea pig. The animals were divided into 5 groups. Group 1 was blank control. Group 2 and Group 3 were injected urokinase (UK) through left subclavian artery or left external jugular vein 30 minutes after photochemical reaction. Group 4 and Group 5 were two control groups. Instead of urokinase, saline injection was applied accordingly. RESULTS: Both intra-arterial thrombolysis and intravenous thrombolysis were effective to improve the hearing levels and the blood supply to the inner ear. 50 minutes after urokinase injection, animals with intra-arterial thrombolysis showed a lower action potential threshold than that with intravenous thrombolysis (P = 0.025). And this phenomenon lasted 30 minutes. Cochlear blood flow of the animals with intra-arterial thrombolysis began to decrease and action potential began to increase 80-90 minutes after UK injection. CONCLUSION: Both intra-arterial thrombolysis and intravenous thrombolysis were effective to the restricted thrombosis in the stria vascularis, and intra-arterial thrombolysis showed a better improvement in the early stage of thrombolysis.

Animals↗

PubMedDate not supplied

Effect of ulinastatin on microcirculation during excessive hemorrhage using fluid therapy.

Microcirculation kinetics during excessive hemorrhage and fluid therapy under anesthesia, with or without treatment with ulinastatin (urinary trypsin inhibitor), was studied by using the rabbit ear chamber. Sixteen rabbits were divided into 2 groups: 8 rabbits without ulinastatin treatment (group C) and 8 rabbits treated with ulinastatin (group U). The vascular diameter, blood-flow velocity, blood-flow rate and urinary output were maintained well in the ulinastatin group as compared to those in the control group. It is concluded that ulinastatin is effective in maintaining microcirculation during excessive hemorrhage and fluid therapy at the same volume.

Animals↗

PubMed2003

[Discrepancy between the blood flow in hyperperfused epicardial coronary vessels and myocardial microcirculation following reperfusion: a study in canines].

OBJECTIVE: To investigate the hemodynamic changes in the epicardial coronary blood flow (ECBF) and myocardial microcirculation (MMC) during reactive hyperemia (RH) in response to reperfusion following 2-min ischemia in the left anterior descending coronary artery of canines. METHODS: Twelve adult mongrel dogs were used, whose left anterior descending coronary artery was separated and ligated for 2 min twice below the first branch. The heart rate, systolic blood pressure, diastolic blood pressure, mean blood pressure, ECBF and MMC were measured respectively before and after the ligation and at 5, 10, 15, 30, 45, 60, 90 and 120 s after reperfusion. ECBF was determined with Doppler coronary flowmeter and MMC derived from the ultrasonic intensity measured by myocardial contrast echocardiography. RESULTS: During the course of RH, ECBF and MMC both evinced responses to hyperperfusion but in manners different in view of their hemodynamic changes, demonstrating the mismatch between them in this condition. ECBF exhibited a much higher peak flow increase than MMC. CONCLUSIONS: RH occurs in response to reperfusion after short-term (2 min) myocardial ischemia, when the discrepancy arises between ECBF and MMC. The primary mechanism might involve the recruitment of the capillaries and the opening of the shunt through the capillaries, and as a consequence, the myocardial perfusion is increased at the cost of decreased reserve of the coronary microcirculation.

Animals↗

PubMed2003

[Clinical implications of impaired microcirculation and hemodynamics in acute respiratory viral infections and their pharmacological correction].

Microcirculation, hemocoagulation and blood viscosity were studied in 377 of 1033 inpatients with influenza and other acute respiratory viral infections. The new data show that it is feasible to improve the course, outcomes and results of the treatment. Microcirculation disorders persist throughout the disease, but in convalescence, intravascular alterations are leading. The microcirculatory changes manifest themselves with advanced erythrocyte aggregation, activation of vascular-platelet and plasmic links of hemostasis, and high blood viscosity at low shift velocities. In the presence of concomitant pathology (ischemic heart disease, hypertensive disease, diabetes mellitus) and development of complications, especially acute pneumonia, these disturbances are still greater and tend to increase to the period of decline of clinical and toxic manifestations. These patients should take acetylsalicylic acid (aspirin) as an antiaggregant and other medicines improving blood rheology.

Acute Disease↗

PubMedDate not supplied

[Medullary microcirculation in human primary and secondary myeloscloroses].

There are histological and experimental evidence for bone marrow microcirculation to play a role in histogenesis of myelosclerosis. Human sternal bone marrow microcirculation was studied after death using ink injection in two cases of primary myelofibrosis, two cases of secondary meylofibrosis (Hodgkin's disease) an one case of osteomyelosclerosis. Control material consisted of 30 previously studied normal human sternums. In all cases interadipocytic sinusoidal network has completely disappeared. Medullary vascularization is anarchic with a vascular and hypervascular areas. The significance of these modifications is discussed.

Aged↗

PubMed1992

The microcirculation and hypertension.

AIM: To review published evidence on the effects of arteriolar changes in primary and secondary hypertension. BACKGROUND: Pressure profile analyses have shown that the microcirculation is a major site of vascular resistance. With the recent refinement of intravital microscopy techniques detailed information has become available on mechanisms of the microvascular resistance increase in hypertension. Three mechanisms play an important role: (1) a decrease in arteriolar diameter; (2) arteriolar vessel wall hypertrophy; and (3) small arteriolar and capillary rarefaction. METHOD: The evidence was synthesized into a hypothesis on the role of the microcirculation in primary forms of hypertension. HYPOTHESIS: The hypothesis formulated contains two important elements in that (1) diminished outgrowth of the microvascular bed in different tissues is seen as an important early pathogenic mechanism; and (2) the decreases in arteriolar diameter and vessel wall hypertrophy are seen as adaptive mechanisms that maintain a constant wall stress. The three factors together maintain the increase in vascular resistance that is common to all established forms of primary hypertension.

Animals↗

PubMed1975

[The effect of the argon laser on the vessels, the macro- and microcirculation of the mucosa of the hamster cheek-pouch. An intravitalmicroscopic study (author's transl)].

The mucosa of the cheek-pouch of five golden Syrian Hamsters was irradiated with the beam of an argonionlaser (diameter 0.5 mm and 200 mW). The effect on the micro- and macro-vessels and the bloodstream, especially of the microcirculation, is studied intravitalmicroscopically. In the microcirculation and also in the small and large venous and arterial vessels a restriction of bloodstream, praestasis, pendulumstream, stream reversal and some white microthrombi, -- emboli and agglutination of erythrocytes are visible. The bloodless welding of the vessels takes place even before the evaporation and coagulation necrosis of the surrounding epithelium of the mucosa as a result of the relatively selective effect of the Argon Laser on the reddish vessel-system by a continuous narrowing of the vessels-walls to the complete loss of their lumen rather than by a thrombosis. Firstly the capillaries, the venoles and the arterioles are obliterated, then those of middle size and at last the large venae and arteries in which case large vessels function for a moment as smaller ones. A continuously growing imbibition with increasing duration of the laser irradiation can be observed. Three clinically important phenomenon, depending on the laserdose can be observed: 1. a partial, 2. a subtotal and total obliteration of the network of the vessels, and 3. a total destruction of the blood-vessels and also of the tissue. Therefore clinically a subtotal or total network obliteration of the blood-vessels of strongly vascularised tissues, haemangiomas, teleangiectasias in case of morbus Rendu-Weber-Osler and livid enlarged nasal conchae might be obtained. Further a total tissue-destruction with a break in the continuity of the tissue for example with strongly vascularised carcinoma or its metastases might be effected.

Animals↗

PubMed1990

[Observation of microcirculation in the free muscular flap during critical ischemic conditions. In vivo experiment].

The influence of 6 hours ischemia on the microcirculation in the rat cremaster muscle isolated on neurovascular pedicle is presented. Microscopic observations of the microcirculation revealed gradual destruction of microvessels beginning in the 4th hour of ischemia. The changes in condensation, structure and colour of the vessels were progressive in time and after 6 hours of ischemia no return of the circulation was possible. Additional 2 hours of observation revealed no reperfusion, so destructive changes after 6 hours proved to be irreversible.

Animals↗

PubMed1992

Effects of nitroglycerin on the coronary microcirculation in normal and ischemic myocardium.

Nitroglycerin dilates conduit coronary vessels and only transiently increases flow, however the effects of nitroglycerin in the microcirculation of normal myocardium and during myocardial ischemia have not been assessed. The goal of this investigation was to determine the effects of steady-state levels of nitroglycerin on the microcirculation of normal and ischemic myocardium. Microvessels on the left ventricle were viewed using stroboscopic epi-illumination in anesthetized, open-chest dogs. Myocardial perfusion was measured with radioactive microspheres. Aortic pressure and heart rate were kept constant by an aortic snare and left atrial pacing. Microvessel diameters were measured under control conditions and during steady-state infusion of nitroglycerin (n = 11, 0.01-100 micrograms kg-1 min-1, i.v.). Nitroglycerin selectively dilated arteries from 201 to 386 microns, but had no effect on large arterioles less than 200 microns. Total coronary vascular resistance remained constant except at the highest dose. When mean coronary pressure was decreased to 35 mm Hg, small arterioles less than 100 microns dilated. Diameters of larger arterioles decreased. Nitroglycerin (10 micrograms kg-1 min-1, i.v., n = 8) selectively dilated microvessels greater than 200 microns in the region distal to the stenosis, although myocardial perfusion was not affected. Thus, nitroglycerin altered the distribution of microvascular resistance without altering overall resistance. We conclude that steady-state infusion of nitroglycerin selectively dilates coronary arterial microvessels greater than 200 microns. During decreased perfusion pressure, recruitable vasodilation in response to nitroglycerin is due to dilation of microvessels greater than 200 microns.

Animals↗

PubMed2003

[The influence of plasmapheresis om microcirculation in patients with different stages of ischemia of lower extremities].

Under investigation there were 152 patients aged 61 +/- 16 years who were conditionally divided into three groups according to the severity of ischemia. Plasmaphersis was carried out by a standard method. The monitoring of changes of microcirculation was done with the help of high-frequency ultrasonic doppler. Plasmapheresis is considered to be an effective method of treatment of the peripheral artery occlusive disease, it improves the microcirculation in ischemic tissues in critical ischemiae of the legs, normalizes the arterial perfusion due to the disappearance of arterio-venous dump at the microcirculatory level.

Arteriosclerosis Obliterans↗