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  • 1
    Electronic Resource
    Electronic Resource
    Changes in vasomotion pattern and local arteriolar resistance during stepwise pressure reduction (1989)
    Springer
    Pflügers Archiv 414 (1989), S. 571-578 
    Details
    ISSN: 1432-2013
    Keywords: Intravital microscopy ; Resistance regulation ; Tenuissimus muscle ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Changes in vasomotion parameters and their consequences for local arteriolar resistance were studied in transverse arterioles and their first order side branches in the tenuissimus muscle of 10 young urethane anesthetized rabbits during stepwise reduction of arterial pressure, using intravital microscopy. To assess the influence of vasomotion on mean local arteriolar resistance, the effective vascular diameter, as a measure of mean flow carrying capacity, was calculated. The contribution of vasomotion to the mean local resistance is limited in transverse arterioles, but important in first order side branches, dominating the flow fluctuations in the downstream capillaries. During pressure reduction, an over-all increase in vasomotion cycle length and amplitude was found in both transverse arterioles and first order side branches, concomitant with an increase in effective arteriolar diameter and a decrease in local blood flow and reduced velocity, as a measure of wall shear rate. Flow autoregulation was observed in 70% of the arterioles. The changes in cycle length and amplitude showed only limited correlations with local blood flow, reduced velocity, arterial pressure and effective arteriolar diameter. This indicates that it is unlikely that only one of these variables is responsible for the changes in the vasomotion parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580993
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Red blood cell flow cessation and diameter reductions in skeletal muscle capillaries in vivo — the role of oxygen (1995)
    Springer
    Pflügers Archiv 430 (1995), S. 852-861 
    Details
    ISSN: 1432-2013
    Keywords: Capillary diameter ; Oxygen tension ; Reduction of perfusion pressure ; Intravital microscopy ; Recoil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract When perfusion pressure is reduced, red blood cell flow in the capillaries of skeletal muscle ceases at a positive pressure difference across the vascular bed, while arterioles dilate and venules are not constricted. This flow cessation (i.e., cessation of red blood cell flow) and luminal diameter changes in capillaries following femoral arterial pressure reduction were investigated in the rabbit tenuissimus muscle in situ (n=42) using intravital video microscopy. Arterial pressure was reduced by occlusion of the aorta distal to the renal arteries. During the experiments, leg and muscle were placed in a sealed box. The muscle was exposed to low PO2 by leading a gas mixture deprived of O2 through the box. Locally at the muscle surface, i.e., under the microscope objective, PO2 was varied by varying the PO2 in the superfusion solution. In all experiments, the remainder of the muscle was kept at low (〈 20 mm Hg) PO2. The incidence of flow cessation was virtually zero at low local (〈 20 mm Hg) PO2 and became almost 100% at local values above 70 mm Hg. Initial equivalent capillary diameters were 3.1–5.8 μm (median 4.0 μm) and did not correlate with local O2 tension. During aorta occlusion, capillary diameters significantly (P 〈 0.0001) decreased by a median value of 8% at all local PO2 values; in 14 out of 54 capillaries local diameter became less than 2.8 μm. The extent of diameter reduction did not correlate with PO2. In the 14 capillaries in which the diameter became less than 2.8 μm flow cessation occurred in only four cases. The minimal diameter reached was always at the site of an endothelial nucleus. The capillary diameter reductions are probably due to passive recoil. In the 48 capillaries in which flow ceased, only in four cases did a red blood cell stop at the site of the nucleus. We conclude that capillary diameter reductions (local and generalized) lead to a considerable increase in capillary resistance which contributes to the occurrence of flow cessation but cannot solely explain it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386186
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of dextrans on platelet distribution in arterioles and venules (1993)
    Springer
    Pflügers Archiv 425 (1993), S. 191-198 
    Details
    ISSN: 1432-2013
    Keywords: Acridine red ; Dextrans ; Fluorescence ; Intravital microscopy ; Microcirculation ; Platelets ; Rheology ; Rabbit mesentery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Dextrans bind to the surface of platelets, red blood cells and endothelium. We investigated whether a low doses (30 mg/kg IV) of 40-kDa (Dx40), neutral, 500-kDa (Dx500) or sulphated, 500-kDa (Dx500S) dextrans influence platelet distribution in rabbit mesenteric arterioles and venules (diameter 17–33 μm). Intravital fluorescence videomicroscopy was used to visualize platelets labelled in vivo with acridine red. Their concentration distribution determined within a thin optical section about the median vessel plane was expressed relative to the mean concentration in that vessel. In arterioles, Dx500 and Dx500S increased the relative platelet concentration in the centre [radial position (R): 0.0–0.47 R] from 0.60 to 1.07 (P〈0.001) and 1.20 (P〈0.003), and reduced it near the wall (0.8–0.9 R) from 1.59 to 0.93 (P〈0.02) and 0.95 (P〈0.03) respectively. In venules a similar, but non-significant, effect was observed. Dx40 did not change platelet distribution in arterioles, but decreased their concentration in venules in the centre from 1.08 to 0.71 (P〈0.03) and increased it at the wall from 0.89 to 1.27 (P〈0.04). The deformability of red blood cells was unchanged, but their aggregation tendency increased approximately twofold after Dx500 and Dx500S injection, while Dx40 had no influence. Leucocyte margination in venules did not affect platelet distribution. Dextran injection did not change microvascular flow velocity or plasma viscosity, suggesting that the observed changes in arteriolar platelet distribution were caused by binding of dextran to the surface of platelets and/or red blood cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374166
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    Paper (German National Licenses)
    Fulltext
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