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At least 127 records · Page 7Linked to original sources
PubMed2001

Magnetic field-like fluid circulation of a porous orifice tube and its relevance to the capillary-interstitial fluid circulation: preliminary report.

In 1886, Starling proposed a hypothesis for the capillary-interstitial fluid transfer in which capillary filtration is attributed to arterial pressure, based on Poiseuille's work in long uniform tubes. In 1967-8, the precapillary sphincter, pores and negative interstitial pressure were reported. In 1984, clinical observations inconsistent with Starling's hypothesis prompted a physical study to verify pressure dynamics in a porous orifice (G) tubes. Results demonstrate that, unlike in Poiseuille's tube, a fluid passing inside the lumen of the G tube exerts a negative energy pressure gradient on its wall; most negative over its proximal part causing inflow of fluid by suction and positive over its distal part causing fluid outflow. A net negative pressure gradient also occurs in a surrounding chamber C, causing fluid to flow in an opposite direction to lumen flow. An autonomous dynamic magnetic field-like G-C circulation occurred between lumen and surrounding fluid compartments. Reviewed literature support the contention that this sole phenomenon adequately explains the capillary-interstitial fluid transfer under both physiological and pathological haemodynamic conditions.

Animals↗
PubMed1997

Renal circulation and cellular metabolism during left ventricular assisted circulation: comparison study of pulsatile and nonpulsatile assists.

We examined left ventricular assist during 6 h for an acute myocardial infarction model in pigs. The outflow cannula was placed in the ascending aorta and an inflow cannula in the left atrium. A pump (Pulsatile group: Zeon Medical and Nonpulsatile group: Nikkiso HPM-15) was connected to each cannula. Items measured were the regional blood flow of the cortex and the medulla in the kidney, renal arterial flow, arterial blood ketone body ratio (AKBR), lactate/pyruvic acid, BUN, creatinine and beta 2-microglobulin. After experimental study, the kidneys were removed, and a pathological study was performed. In the pulsatile assisted group, renal cortical blood flow increased but medulla blood flow decreased. On the other hand, in the nonpulsatile assisted group, both regional blood flows decreased. That means that in the pulsatile assisted group intrarenal redistribution improved, rather than in the nonpulsatile assisted group. The results of our study indicated that pulsatile assist produced superior circulation in the kidney, and the microcirculation on the cell level was superior as well in early treatment of acute left heart failure.

Animals↗
PubMed1982

The fate of circulating amines within the pulmonary circulation.

Pulmonary biogenic amine clearance is a carrier-mediated drug sensitive process associated with uptake into endothelial cells and subsequent metabolism by monoamine oxidase and other enzymes. Its function seems to be maintenance of arterial circulatory homeostasis by biochemically regulating circulating vasoactive hormones. Numerous pulmonary pathologic conditions are associated with alterations in these functions. However, a more precise physiologic role remains to be defined. Areas for further research include: 1. Comparative studies on the ability of endothelium from extrapulmonary and pulmonary vasculatures to extract and metabolize vasoactive amines and other humoral substances. This work must be done both in intact animals and in isolated cultured endothelium derived from organ microvasculatures. 2. Study of factors (e.g. steroids, development, etc) that may regulate pulmonary metabolic functions. 3. Measurements in humans under various clinical conditions. To this end, indicator dilution estimates and transpulmonary gradients have provided intriguing promise of means to assess endothelial metabolic functions in both normal and injured lung.

Animals↗
PubMedDate not supplied

XIII. Cerebral circulation and metabolism in stroke. Cerebral circulation and metabolism in stroke study group.

An understanding of the cerebral circulation is so fundamental to comprehension of the pathogenesis of stroke that cerebral blood flow and metabolism merit review in this series of reports. The authors recognize that the research described here is very technical in nature and may appear to have little practical application to clinical medicine. Nevertheless, these matters are basic to the development of precise methods for the measurement of regional cerebral blood flow in man which could be used to monitor the therapy of stroke with greater success than is possible at present.

Brain↗
PubMed1975

Hepatic circulation in acute hemorrhage with reference to renal circulation.

Studies were made on the hemodynamics in the liver and kidney during hemorrhage and retransfusion, using 20 dogs with or without hepatic periarterial nerve plexus, anaesthetized with sodium pentobarbital. The results were as follows. In 14 dogs in which the hepatic periarterial nerve plexus was left intact (Group A), the averages of the hepatic arterial flow (HAF), portal venous pressure (PVP), portal venous flow (PVF), and flow in the right renal artery (RAF) decreased significantly to 38, 64, 35, and 25%, respectively of the control levels when the abdominal aortic pressure (ABP) fell to 40 mm Hg (36% of the control level) during hemorrhage. At the same time the portal venous resistance (PVR) and the right renal vascular resistance (RVR) increased greatly and the hepatic arterial resistance (HAR) either increased or decreased in different dogs. During retransfusion the ABP and vascular resistance returned to nearly the control levels, the PVF increased beyond the control level. In 6 dogs in which the nerve plexus was resected (Group B), the decreases in the HAF and RAF during hemorrhage were not significantly different from those in Group A. These results may suggest the following. The decrease in the HAF during hemorrhage seems to be mostly a passive change resulting from decrease in the systemic blood pressure. Neurogenic regulation may be a little. Further, the existence of the humoral regulation and autoregulation in the HAF were suggested in some cases. While, the responsibilities to hemorrhage and retransfusion appear to be different among the examined three vessels, i.e. the hepatic artery, portal vein, and renal artery. No definite interrelation was seen between the hepatic and renal circulations.

Acute Disease↗
PubMed1992

Circulating endothelin is not extracted by the pulmonary circulation in man.

To determine whether endothelin is extracted from plasma during passage through the pulmonary circulation, we measured its concentration at several points, including the pulmonary artery and the left superior pulmonary vein in seven patients undergoing cardiac surgery. Endothelin concentrations were very similar at all sites sampled. In patients undergoing coronary artery bypass grafting, there is no net pulmonary clearance of endothelin.

Adult↗
PubMed1975

[Effect of Bencyclane on regional cerebral circulation. Quantitative local measurement of cerebral circulation in healthy persons and patients with cerebrovascular insufficiency, awake or in light general anesthesia].

The effect of intravenous continuous drip infusion of Bencyclan (8mg/min) on regional cerebral blood flow was investigated in 30 adult patients, using the intraarterial 133-Xe-clearance-method and a 10-detector-equipment. The application of Bencyclan in 5 persons with normal cerebral circulation entailed no significant change of rCBF. In 5 from 15 patients with cerebrovascular disease in the awake state continuous drip infusion of Bencyclan caused a decrease of global and regional cerebral blood flow with reduction of the regional flow values about 15.3 to 28.4 p.c. In 10 patients there was seen no statistical significant change of regional cerebral blood flow as compared with the flow values in the resting state. In 10 patients rCBF-examinations were performed prior and after intravenous injection of Bencyclan in a state of a very light nitrous-oxide-halothan analgesia. In all patients Bencyclan caused an overall decrease of cerebral blood flow about 8.8 p.c. to 24.3 p.c. which in 5 cases achieved statistical significance.

Adult↗
PubMed1989

[The hemodynamics of the lung circulation of minipigs after experimentally-caused Sedlarik's pulmonary embolism. III. Sedlarik's embolization of the lung circulation by electrically-activated blood].

Pulmonary embolisms of different clinical degree of severity can be produced by means of the pulmonary embolism model according to Sedlarik by application of electrically activated blood as a thrombogenic substance. An unambiguous influence of the size and the consistency of the thrombus exists concerning the severity of the hemodynamic changes. However, the hemodynamics seems to adapt to the changed conditions of the circulation, because a tendency to normalization was observed in short-term experiments. The morphologic changes after embolisation are more typical for the severity of the clinical picture in this acute phase than the hemodynamics. A testing of the animal model in long-term experiments seem to be ingenious for that reason.

Animals↗
PubMed1987

[Comprehensive radionuclide evaluation of the general circulation and the uteroplacental circulation in multiple pregnancy].

The paper is concerned with the results of the clinical testing of a combined method of assessment of the greater and uteroplacental circulation in 15 women with plural pregnancy. The method permits the detection of hemodynamic changes without increasing radiation exposure to the mother's body and fetuses, the determination of a type of plural pregnancy (monochorionic or dichorial twins), and the prediction of pregnancy outcome that is very important for the choice of appropriate and timely therapy.

Adult↗
PubMed1983

Blood leukocyte responses to extracorporeal circulation. I. Short term extracorporeal circulation in dogs without and with extracorporeal irradiation.

Short term (1 h) extracorporeal circulation without or with irradiation of blood was performed in two normal dogs in a series of experiments. The granulocyte count was constantly diminished, while the lymphocytes did not show any particular change in their concentration. In the majority of the experiments a decrease of the CFU-C content occurred to less than 70% of the initial level. There was no difference in the results of experiments with or without irradiation. In the "bag to bag" procedures, no significant change in the blood leukocyte counts including CFU-C, was established.

Animals↗
PubMed1983

Blood leukocyte responses to extracorporal circulation. III. Long term extracorporeal circulation without and with irradiation in normal and splenectomized dogs.

Long term (12-48 h) extracorporeal circulation without and with irradiation of the blood was performed in normal and splenectomized dogs in order to observe the effect of these procedures on blood leukocyte counts including CFU-C. A transient granulocytopenia and a decrease of lymphocyte count were observed. The blood CFU-C level diminished to a very low level and remained low for the whole time of the experiments. There was no significant difference between the results of procedures with or without irradiation. The similar effect of a shortened tubing system on the blood leukocyte count is also reported. Heparin infusion alone did not decrease the peripheral CFU-C concentration. The possible explanations for the observed phenomena are discussed.

Animals↗
PubMed1984

The economy of the enterohepatic circulation of bile acids in the baboon. 1. Studies of controlled enterohepatic circulation of bile acids.

A primate model with controlled enterohepatic circulation has been developed which allowed short-term evaluation of bile salt pool size, cycling frequency, and fecal losses. We found that when bile salt secretion into the small bowel was increased above 700 mumol/hr bile acid pool cycling frequency was also increased. The latter allowed short-term regulation of bile salt pool size by affecting increased fecal losses. These compensatory mechanisms were associated with a return of bile acid secretion and cycling frequency to normal usually within 12-24 hours. Conversely, during decreased bile salt secretion, regulation of bile salt pool size was accomplished by decreased pool cycling, which decreased fecal losses. Bile acid secretion into the intestine was therefore a major determinant of bile salt cycling frequency. The latter affected bile salt fecal loss to provide short-term regulation of bile salt pool when feedback regulation of bile salt synthesis was nonoperative.

Animals↗
PubMed1984

The economy of the enterohepatic circulation of bile acids in the baboon. 2. Regulation of bile acid synthesis by enterohepatic circulation of bile acids.

Isotope dilution within bile acid pools and radiochemical assessment of cholesterol oxidation to bile acids were methods used to measure short-term feedback regulation of bile acid synthesis in baboons with controlled enterohepatic circulations. Intraduodenal infusion of labeled endogenous bile acid pools into bile acid-depleted animals with enhanced bile acid synthesis showed that the rate of bile acid returned to the liver affected the degree of inhibition of bile acid synthesis. Infusion of prepared bile acid pools of varying composition resulted in a specific pattern of feedback inhibition of bile salt synthesis related to pool composition and mass. Individual bile salts inhibited their own synthesis more than that of other bile salts, and chenodeoxycholic and deoxycholic acids were found to have greater inhibitory effects than cholic acid. Glycine-conjugated cholic and chenodeoxycholic acids had greater inhibitory effects than did the respective free bile salts. Infusion of mixed bile acid pools showed that dihydroxy bile acids (chenodeoxycholic or deoxycholic) enhanced feedback inhibition of cholic acid. In all studies, inhibition of bile acid synthesis occurred twice as fast as its derepression.

Animals↗
PubMed1993

[Ornipressin (POR 8)--effect on coronary blood circulation and the peripheral circulation. An animal experimental study].

Ornipressin (POR 8), referred to below as OR, is a synthetic derivative of natural vasopressin. It was introduced into clinical practice to replace epinephrine as a local vasoconstrictor because OR was presumed to produce fewer undesirable side-effects. However, mayor cardiovascular complications following local infiltration of OR have been reported in recent time. Beside increased blood pressure and changes in heart rate, there is evidence that the systemic effects of OR include a distinct vasopressor activity on coronary arteries. This study was planned to investigate the effects of OR in haemodynamics and the coronary vascular system. METHODS. The effects of OR on systemic haemodynamics and coronary circulation were studied in nine anaesthetized closed-chest mongrel dogs. Anaesthesia was administered using N2O/O2 (FiO2:0.33) and enflurane (1.0 vol% endtidal). Saline-filled catheters were used to measure intravascular pressures. Left ventricular pressure change (dP/dt) was monitored with a tip catheter manometer. Cardiac output (CO) was determined using thermodilution and coronary sinus blood flow, using a Pitot catheter. Recording of baseline values was followed by bolus injection of OR (0.03 U/kg) and changes in haemodynamics were measured for 90 min at fixed time intervals. Statistical analysis was performed by analysis of variance for repeated measures. A value of P < or = 0.05 was considered to indicate statistical significance. RESULTS. Significant maximum changes occurred within 3-5 min after administration of OR. Systolic and diastolic arterial pressures increased by 33% and 39%, respectively. With only minor changes in heart rate, cardiac output markedly decreased by 44% and total peripheral resistance increased by 159%. Impaired pump function of the left ventricle became obvious by a decrease in maximum dP/dt, a decrease in ejection fraction by 35%, and a concomitant sharp increase in left ventricular enddiastolic pressure by 68% and in endosystolic volume by 41%. At the same time, OR produced a marked impairment of coronary perfusion. Myocardial blood flow fell by 32%, while coronary vascular resistance rose by 112%. Increased myocardial oxygen demand and reduced oxygen supply resulted in very low values of coronary venous oxygen saturation (< 20%). CONCLUSIONS. Systemic effects of OR are characterized by a sharp rise in arterial blood pressure. Concomitantly a decrease of myocardial contractility leads to a compromised left ventricular function with marked increases in left ventricular enddiastolic pressure. These haemodynamic changes are associated with an imbalance of myocardial oxygen demand and delivery due to the distinct OR-induced coronary constriction. With regard to the deterioration of systemic and cardiac haemodynamics the indications and use of ornipressin in clinical practice need to be reevaluated.

Animals↗
PubMedDate not supplied

[Our initial experience of protecting the myocardium by irrigating the pericardial cavity with a circulating cold solution during operations with artificial circulation].

In 21 patients with coronary heart disease, a procedure of protecting the myocardium was used during cardiac surgeries via irrigation of the pericardial cavity with circulating cold solution in combination with cardioplegia into the aortic root. The application of the procedure maintained stable myocardial temperature from 10.26 +/- 1.55 to 11.99 +/- 1.95 degrees C, excluding excessive overcooling and premature warming. The procedure awaits further studies in terms of biochemical changes and morphology of the myocardium at various stages of surgery.

Adult↗