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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 361 (1976), S. 183-189 
    ISSN: 1432-2013
    Keywords: Skeletal muscle blood flow ; Microcirculation ; Capillary exchange ; Microembolization ; Shunt flow ; AV-Anastomoses ; Non-nutritive flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Partial microembolization of the previously dilated gastrocnemius muscle of the dog was performed by intra-arterial injection of latex microspheres (max. diameter 50 μm). No particles larger than 10 μm were recovered from the venous blood. Blood to tissue clearance of 4-amino-antipyrine was found to decrease after microembolization, and capillary transport coefficients were disproportionately lowered in comparison with the observed decrease of total blood flow. Venous oxygen saturation increased despite decreasing total blood flow in the working muscle after microembolization. The data indicate a shift of blood flow from nutritive to functionally non-nutritive channels.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Microcirculation ; Capillary blood flow ; Red cell flow velocity ; Plasma flow velocity ; Dual slit photometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A method is described which can be used to simultaneously determine the flow velocity of plasma and of red blood cells in small glass tubesin vitro or in living microvessels of the microcirculation. The principle of dual slit photometry is applied to the measurement of plasma flow by determining the passage time of a dye bolus across two photodetectors separated by a variable distance. Measurements performed bothin vitro andin vivo indicate a significant difference (up to 85%) between cellular and plasmatic flow velocity.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 380 (1979), S. 115-120 
    ISSN: 1432-2013
    Keywords: Capillary blood flow ; Dynamic hematocrit ; O2-delivery ; Microcirculation ; Red blood cell rheology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract O2-delivery by a single capillary is a function of the flow rate and thefraction of flow made up of red blood cells. Capillary flow rate in turn depends upon flow resistance which is determined by thefraction of capillary volume occupied by red blood cells. Experiments were carried out to study the relationship between these parameters in an in vitro model consisting of glass capillaries (I.D. 3.3–11.0 μm) branching from a large bore feeding channel which was perfused at variable flow rates with suspensions of human red cells with different hematocrits. Capillary flow rates ranged from 0–10−4 mm3 s−1. The results indicate that the red cell flow fraction increases with increasing capillary flow rate and with decreasing feeding vessel flow rate. Capillary volume fraction occupied by red cells similarly depends on these two parameters, but is consistently lower than the red cell flow fraction. Capillary flow resistance increases with flow rate due to increasing volume fraction of cells. If the results obtained with the model system are applicable to in vivo capillaries it must be concluded that O2-delivery by a single capillary is not linearly related to flow rate but increases more than proportionately with flow rate. Due to alteration of resistance with flow rate another type of “autoregulation” of capillary flow is proposed which tends to keep flow rate constant despite changes of driving pressure.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 297 (1967), S. 107-114 
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Durch den Nachbau von Platte und Kegel eines Viscosimeters aus Plexiglas wird eine Beobachtung des Blutes unter definierten Strömungsbedingungen ermöglicht. Die Kombination von Viscositätsmessung und Beobachtung erlaubt eine Untersuchung der Bildung von Erythrocytenaggregaten in Abhängigkeit vom Schergrad sowie ihrer rheologischen Eigenschaften.
    Notes: Summary By making transparent cone and plate of a viscometer, the blood streaming under definite flow conditions could be observed. By simultaneous observation and viscometry the manifestation and rheological properties of red cell aggregates can be examined.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 281 (1964), S. 191-200 
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Nach Ischämie von Gehirn, Extremität und Niere fanden sich im venösen Blut dieser Organe Thrombocytenaggregate, die quantitativ mit der Methode von Swank als Siebungsdruck (screen filtration pressure) gemessen wurden. In der 1. min nach einer 20 min langen Ischämie des Gehirns, einer Extremität und einer Niere waren die Siebungsdrucke im venösen Blut dieser Gewebe signifikant erhöht. Die mittleren venösen Siebungsdrucke betrugen beim Gehirn 70 mm Hg, bei der Extremität 88 mm Hg und bei der Niere 55 mm Hg gegenüber mittleren Ausgangswerten zwischen 29 und 36 mm Hg.
    Notes: Abstract Aggregates of thrombocytes were found in the venous blood of the brain, of a hind leg, and of the kidney after an isolated ischemia of these organs. The aggregates were quantitatively measured as screen filtration pressure of blood by the method of Swank. After 20 min ischemia of the brain, of the hind leg, and of the kidney the screen filtration pressure was significantly increased in the venous blood draining from these tissues during the first minute. The screen filtration pressure averaged in the venous blood of the brain 70 mm Hg, of the hind leg 88 mm Hg, and of the kidney 55 mm Hg in contrast to the mean control values between 29 and 36 mm Hg.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2013
    Keywords: Cerebral Cortex ; Carbon Dioxide ; Oxygen ; Electrophysiology ; Großhirnrinde ; Kohlensäure ; Sauerstoff ; Elektrophysiologie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An isolierten Hundeköpfen wurde die Gleichspannung zwischen der Konvexität des Gehirns (Gyrus lateralis) und der Nase (Knochenoberfläche des os frontale) bei Änderung des arteriellen pO2 oder pCO2 gemessen. Erniedrigung des pO2 oder pCO2 führt zu einer Negativierung, Erhöhung des pCO2 zu einer Positivierung. Erhöhung des pO2 ändert die Gleichspannung nicht.
    Notes: Summary In isolated dog head preparations the d.c. potential of the convexity of the brain (gyrus lateralis) with respect to the surface of os frontale was measured while the arterial pO2 or pCO2 were changed. Lowering of arterial pO2 or pCO2 resulted in a negative, increasing of pCO2 in a positive shift. No change of the cortical d.c. potential was found on increasing pO2.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 352 (1974), S. 303-313 
    ISSN: 1432-2013
    Keywords: Collateral Flow ; Collateral Channels in Skeletal Muscle ; Skeletal Muscle Blood Flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the isolated canine semitendinosus muscle supplied by two separate arteries and veins entering and leaving the muscle at a distance of about 12 cm from each other blood flow, O2-content, andpO2 in all four vessels were measured. Using the dye dilution technique the distribution of arterial inflow on both veins was determined. It was found that the muscle portion supplied by one artery is not necessarily identical with the muscle portion drained by the corresponding vein. In 9 semitendinosi no dye could be found in the contralateral vein after indicator injection into one artery. Therefore, collateral flow (CF) in this type of muscle could be determinted after acute clamping of one artery by measuring venous outflow through the corresponding vein. CF was 4.9 ml · min−1 · 100 g−1 and could be increased by vasodilatation to 14.2 ml · min−1 · 100 g−1. Since after acute occlusion of one artery the VO2 did not decrease significantly CF can supply the tissue of the resting skeletal muscle sufficiently with O2. By measuring back flow (BF) in skeletal muscle CF is overestimated in a non-dilated vasculature and is underestimated in a dilated muscle vasculature. After embolization of the vasculature with microspheres (maximal diameter=40 μ) BF was less than 50% of CF measured during vasodilation. Therefore, in skeletal muscle more than 50% of CF passes through collateral vessels less than 40 μ in diameter.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 390 (1981), S. 283-287 
    ISSN: 1432-2013
    Keywords: Nucleated erythrocytes ; Blood rheology ; Viscosity ; Hematocrit ; Capillary circulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The flow properties of nucleated avian (duck) red cell suspensions were determined in narrow glass capillaries (internal diameter 5–11 μm) perfused at constant pressure. Measurements were carried out of cellular and suspending fluid flow velocity and dynamic (tube) hematocrit. Comparison with previous measurements on human erythrocyte suspensions showed that the dynamic hematocrit reduction (Fahraeus effect) of avian cell suspensions was significantly more sensitive to changes of hematocrit than observed on the human cells. It was in addition found that the Fahraeus effect is the dominating phenomenon determining the viscosity of the nucleated cell suspensions, in contrast to suspensions of non-nucleated human red cells. Furthermore, the apparent viscosity of the nucleated cell suspensions is significantly higher than that of human blood at equal capillary diameter and tube hematocrit. In the living capillary bed of birds, the unfavourable rheological properties of the nucleated red cells could be compensated for by a low capillary hematocrit and/or a higher capillary density compared to mammalian species.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 330 (1971), S. 206-216 
    ISSN: 1432-2013
    Keywords: Mesenteric Circulation ; Capacitance System ; Venous Microvascular Distensibility ; Modulus of Volume Elasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In 20 experiments the distensibility characteristics of venous microvessels of 22–148 μm internal diameter in response to arterial and venous pressure changes were examined microphotographically in the isolated and perfused mesentery of the dog. Over a range of arterial pressure between 0 and 170 mm Hg venular diameter changed by 31,8±8,8% and venular length by 6.3±4.4%. Venular length changes were significantly correlated to corresponding changes in the accompanying arterioles, whereas no correlation could be found between changes of length and diameter and the control diameters. With venous pressure elevation from 0 to 30 mm Hg an increase of the volume of venous microvessels of about 360% was measured; beyond a venous pressure of 30 mm Hg a limitation of distensibility was observed in these vessels. The moduli of volume elasticity calculated from these data were lower than the moduli reported for the total venous vasculature of the intestinal bed in the range of physiological pressures. It is concluded that the venous microvessels represent the most distensible elements of the venous vascular system.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 430 (1995), S. 978-983 
    ISSN: 1432-2013
    Keywords: Endothelium ; Skeletal muscle ; Acetylcholine ; Arterioles ; Microcirculation ; Nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The contribution of luminally released endothelium-derived relaxing factor (EDRF) transported with the flowing blood to the control of smooth muscle tone of downstream arterioles was studied. The dilatory response of arterioles in the spinotrapezius muscle of the rat to superfusion of acetylcholine (ACH) was investigated by intravital microscopy before and after blockade of blood flow by micropipette occlusion upstream of the site of observation. Vessels were studied without treatment, after topical application of indomethacin (INDO, 3 · 10−5 M) to inhibit prostanoid production and after local treatment withN G-nitro-larginine (L-NNA, 2.9 · 10−3 M) to suppress local production of EDRF. In untreated vessels and after INDO, responses to ACH were not significantly different in the presence or absence of blood flow. After L-NNA, the responses to ACH were reduced to about 50%, but were again similar with or without flow. These results indicate that luminally transported EDRF does not play a significant role in controlling arteriolar tone in small skeletal muscle arterioles.
    Type of Medium: Electronic Resource
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