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A new insight on direct actions of Granulocyte-Colony Stimulating Factor in the myocardium

von Dr. Ana Catarina Ribeiro Carrão

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[1.] Arc/Fragment 034 01 - Diskussion
Zuletzt bearbeitet: 2014-02-25 23:25:26 WiseWoman
Arc, BauernOpfer, Fragment, Gesichtet, Heil Schaper 2004, SMWFragment, Schutzlevel sysop

Typus
BauernOpfer
Bearbeiter
Hindemith
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 34, Zeilen: 1-11
Quelle: Heil Schaper 2004
Seite(n): 450, 451, Zeilen: 450: r.col: 1ff; 451: l.col: 1ff
34a diss.png

Fig. 9 – Diagram of blood flow changes after occlusion of the femoral artery in the rabbit hind limb. After occlusion of the femoral artery (X), blood flow (arrows) follows the gradient between pressures proximal to the occlusion site and very low distal pressures, recruting pre-existing collateral arterioles89.

According to Heil and Schaper91, the vessel wall is now exposed to pronounced mechanical forces: increased blood flow directly augments fluid shear stress (FSS), i.e., the viscous drag that flowing blood exerts on the endothelial lining. By assuming Newtonian fluid dynamics, FSS can be estimated using the following equation:

34b diss.png

The authors demonstrate that blood flow (Q) will directly result in increased FSS (&tao;). The wall of the collateral arteriole is influenced by pressure-related forces like longitudinal-, circumferential- and radial-wall stresses. The distension of the vessel wall, structurally weakened by intravascular pressure, increases the circumferential wall stress (CWS). FSS is a relatively weak force compared with CWS, which is 106 times higher, posing the hypothesis that FSS can only act in concert with pressure-dependent forces91.


89. Gho BC, Schoemaker RG, van den Doel MA, Duncker DJ, Verdouw PD. Myocardial protection by brief ischemia in noncardiac tissue. Circulation. 1996;94:2193-2200.

91. Helisch A, Wagner S, Khan N, Drinane M, Wolfram S, Heil M, Ziegelhoeffer T, Brandt U, Pearlman JD, Swartz HM, Schaper W. Impact of mouse strain differences in innate hindlimb collateral vasculature. Arterioscler Thromb Vasc Biol. 2006;26:520-526.

34a source.png

Figure 1. Diagram of blood flow changes after occlusion of the femoral artery in the rabbit hind limb. After occlusion of the femoral artery (X), blood flow (arrows) follows the gradient between high pressures proximal to the occlusion site and very low distal pressures. Preexisting collateral arterioles are recruited.

[...]

[...] Hence, the collateral vessel wall is now exposed to various pronounced mechanical forces: increased blood flow directly augments fluid shear stress (FSS), ie, the viscous drag that flowing blood exerts on the endothelial lining. Assuming Newtonian fluid dynamics, FSS can be estimated using the following equation:

34b source.png

The equation that already includes blood viscosity (η) and the internal radius of a vessel (R), demonstrates that increased blood flow (Q) will directly result in increased FSS (&tao;).8

Furthermore, the wall of the collateral arteriole is influenced by pressure-related forces like longitudinal-, circumferential-, and radial wall stresses. The distention of the vessel wall, structurally weakened by matrix digestion, by the intravascular pressure, increases the circumferential wall stress, a known activator of smooth muscle cells (SMCs) proliferation.9

In contrast, FSS is a relatively weak force, more than two orders of magnitude lower than the pressure-derived forces

[page 451]

acting on the arterial wall. The difference is so impressive that other authors questioned the morphogenic force of FSS or posed the hypothesis that FSS can act only in concert with the pressure-dependent forces.9


8. Cox R. Physiology and hemodynamics of the macrocirculation. In: Stehbens W, eds. Hemodynamics and the Blood Vessel Wall. Springfield, Ill: Charles C. Thomas; 1979:75–156.

9. Scheel KW, Fitzgerald EM, Martin RO, Larsen RA. The possible role of mechanical stresses on coronary collateral development during gradual coronary occlusion. In: Schaper W, eds. The Pathophysiology of Myocardial Perfusion. Amsterdam: Elsevier/North-Holland; 1979:489–518.

Anmerkungen

The source is mentioned in the text (also on the previous page: Arc/Fragment 033 25), but it is not clear that the text as well as the diagram is taken 1-to-1 from the source, which is not listed in the bibliography. Note also that in the given sources Gho et al. (1996) and Helisch et al. (2006) the copied material cannot be found.

Sichter
(Hindemith), WiseWoman


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