Fibrinogen viscosity

Mature human albumin consists of one polypeptide chain of 585 amino acids and contains 17 disulfide bonds. By the use of proteases, albumin can be subdivided into three domains, which have different functions. Albumin has an ellipsoidal shape, which means that it does not increase the viscosity of the plasma as much as an elongated molecule such as fibrinogen does. Because of its relatively low molecular mass (about 69 kDa) and high concentration, albumin is thought to be responsible for 75-80% of the osmotic pressure of human plasma. Electrophoretic smdies have shown that the plasma of certain humans lacks albumin. These subjects are said to exhibit analbuminemia. One cause of this condition is a mutation that affects spUcing. Subjects with analbuminemia show only moderate edema, despite the fact that albumin is the major determinant of plasma osmotic pressure. It is thought that the amounts of the other plasma proteins increase and compensate for the lack of albumin. 

The first reason is theoretical. The demonstrated effects of the new substances and combinations on lipids and carbohydrates do not have any major relevance to the thromboembolic process. The latter is linked primarily to changes in the hemostatic system and blood coagulation, involving platelet aggregation, coagulation factors, fibrinogen concentrations, and blood viscosity. 

Mechanism of action that provides symptom relief with pentoxifylline is poorly understood but is thought to involve red blood cell deformability as well as a reduction in fibrinogen concentration, platelet adhesiveness and whole blood viscosity (75). The recommended dose of pentoxifylline is 400 mg three times daily with meals. Pentoxifylline causes a marginal but statistically significant improvement in pain-free and maximal walking distance (a net benefit of 44 m in the maximal distance walked on a treadmill (95% Cl, 0 14 to 0 74) based on meta-analyses of randomized, placebo-controlled, double-blind clinical trials (76). At the same time pentoxifylline does not increase the ABI at rest or after exercise (56). Pentoxifylline may be used to treat patients with intermittent claudication however, it is likely to be of marginal clinical importance (56,77). Medical therapies... 

A systematic review of 23 studies found that moderate and high levels of physical activity are associated with reduced risk of all stroke (Lee et al. 2003). This reduced risk is thought to be related to lower body weight, blood pressure, blood viscosity, fibrinogen concentration and better lipid profiles. 

F, is smaller than V, a low /3-value will also result. This illustration by no means implies that fibrinogen must require two equivalent ellipsoids for viscosity and sedimentation. It is not clear why the 3-function for fibrinogen behaves abnormally, if the other weight of evidence is accepted as a correct description of the molecule. It is even possible that the conclusion of Siegel et al. (1953) may eventually turn out to be the correct one. There is need for more extensive tests for the j8-function. 

As mentioned earlier, ideally the best answer should come from the determination of the 5-function. Unfortunately at present the rotary diffusion coefficient is usually the least reliable quantity in all hydrodynamic measurements because of errors inherent in the physical methods of flow birefringence and perhaps also non-Newtonian viscosity (see Section IV). (Electric birefringence also may not give the same rotary diffusion coefficient as the other two methods, since the equivalent ellipsoids can be different under shearing stress and under electrical field.) Edsall (1954) has also illustrated the impossibility of evaluating the axial ratio from the 5-function. The latter was about 0.80 for fibrinogen which corresponded to a prolate ellipsoid with an axial ratio of more than 300. If the rotary diffusion coefficient were only about 15% greater than that listed in Table V the calculated axial ratio would decrease to between ten and twenty. 

Naftidrofuryl is a complex acid ester of diethylaminoetha-nol, with direct vasodilatory properties and antagonistic effects on 5-HT (via 5-HT2 receptors) and bradykinin. It also causes an intracellular increase in ATP concentrations, improves cellular oxidative metabolism (by activating succinate dehydrogenase), and reduces blood and plasma viscosity and fibrinogen concentrations. 

Pentoxifylline (Trental) U2g Alters RBC flexibility decreases platelet adhesion reduces blood viscosity decreases fibrinogen concentration Dyspnea nausea vomiting headache dizziness Recent retinal or cerebral hemorrhage active bleeding Not recommended in patients with 1C (Grade IB)... 

This drug alters erythrocyte flexibility, allowing erythrocytes to pass more easily through vessels. In addition, it causes a decrease in fibrinogen, and increased fibrinolytic activity. These functions result in a decrease in blood viscosity and an increase in perfusion, particularly through the microcirculation, increasing tissue oxygenation. 

These have thus far included studies of the following systems proteins, microemulsions, colloids, copolymers, micelles, liposomes, fibrinogen, internal molecular motions, liquid interfaces, fatty acids, viruses, bacteria, vesicles, viscosity, lipids, motile cells, enzymes, lipoprotein, polyelectrolytes, spores, liquid crystals, glass transmissions, sols, microgels, soot, blood plasma, nanoparticles, swelling latex, gene delivery, and intravenous fat emulsions. 

Begg, T.B. and Hearns, J.B. (1966) Components in blood viscosity The relative contribution of hematocrit, plasma fibrinogen and other proteins. Clinical Science, 31, 87-93. 

Determination of molecular symmetry. Molecular symmetry of P. can be determined from measurements of viscosity, streaming birefringence, rates of sedimentation and diffusion, or directly by electron microscopy, For a known M, the frictional coefficient can be calcnlated from ultracentrifugal measurements, e.g. from the sedimentation /= [Mfl - vp)]/S, where v is the partial specific volume, p is the density and S is the sedimentation constant. The axial ratio a/b of a P. can be derived from the frictional ratiowhereis the/of a spherical molecule. The value of a/b for most globular P. is between 2 and 20, and greater than 20 for fibrous R, e, g. the axial ratio of fibrinogen is 30. 

Fia. 67. Effect of incubation of the fibrinogen-thrombin mixture at pH 4.85 on the viscosity of the mixture and on the clotting time of the reneutralized mixture. Oi viscomty. A, clotting time (Laki, 1951). 

Lowe GD, Fowkes FG, Dawes J, Donnan PT, Lennie SE, Housley E. Blood viscosity, fibrinogen and activation of coagulation and leucocyte in peripheral arterial disease and the normal population in the Edinburgh Artery Study. Circulation 1993 87 1915-1920. 

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