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At least 595 records · Page 33Linked to original sources
PubMed1982

Influence of blood viscosity on cochlear action potentials and oxygenation.

Impairment of the cochlear blood supply of guinea pigs was induced in order to study the effects of hypoxia on the cochlear action potentials. The oxygenation of the cochlear structures was decreased by perfusing the ears with polycythemic hyperviscous blood. The validity of using this model of cochlear blood flow was based on the propensity of the blood to flow in a laminar way. Because of the streamlined flow pattern, the blood supplied by the two vertebral arteries does not mix within the common trunk of the basilar artery. The retrograde injection of polycythemic hyperviscous blood into one vertebral artery will affect the ear on the injected side only. The high viscosity of the polycythemic blood decreases the rate of flow of blood through the cochlear vessels; the high oxygen content of this blood, however, avoids hypoxia of the cochlea. Therefore, in order to make the slowdown in the blood flow evident, its oxygen content was reduced to a 'precritical level' before it was infused. Injecting normoviscous blood with a 'precritical level' of oxygen caused a mild reduction in the scala media pO2 of 15.2% for the whole group of twenty animals. The hyperviscous blood with the same level of oxygenation, however, reduced the pO2 in the scala media to 53.3% of normal. These findings explain the difference in the altered click-evoked action potentials in the two groups of animals.

Action Potentials↗
PubMed1994

OXYGEN TRANSPORT IN MARINE GREEN TURTLE (CHELONIA MYDAS) HATCHLINGS: BLOOD VISCOSITY AND CONTROL OF HEMOGLOBIN OXYGEN-AFFINITY

Erythrocytes from green turtle hatchlings contain a single embryonic component, unlike those from other cleidoic eggs, in which adult hemoglobin (Hb) constitutes a significant fraction of total Hb at hatching. The functional properties of the isolated and purified green turtle hatchling Hb that distinguish it from adult Hb are a high affinity for oxygen and marked sensitivity to organic phosphate modulators. Hatchling erythrocytes also contain higher concentrations of ATP and 2,3-diphosphoglyceric acid, but their oxygen affinity is indistinguishable from that of adult erythrocytes. Hatchling erythrocyte mean cell volume is approximately half of the adult value, but hematocrit, blood hemoglobin concentration and blood viscosity of hatchlings and adults are similar. Oxygen-carrying capacity in green turtles, unlike that of other diving vertebrates, corresponds with a theoretically derived optimum. The possibility of allosteric control of Hb oxygen-binding in hatchlings may relate not to the challenge of exercise during the dispersal phase but to conditions in the late embryo in the nest.

Journal Article↗
PubMed1997

Covalent binding of poly(ethylene glycol) (PEG) to the surface of red blood cells inhibits aggregation and reduces low shear blood viscosity.

A simple method to coat human red blood cells (RBC) with PEG is described. Using a reactive derivative, monomethoxy-PEG (mPEG) was covalently attached to the surface of RBC in aqueous media under mild conditions. The PEG coating dramatically reduced aggregation and low shear viscosity of RBC resuspended in autologous plasma, and inhibited RBC agglutination by blood group-specific antibodies. Morphology and deformability of the PEG-treated cells were unaltered. The PEG coating of the RBC surface may be of significant benefit in the treatment of a variety of diseases characterized by vasoocclusion or impaired blood flow, e.g., myocardial infarction, sickle cell disease.

Blood Viscosity↗
PubMed1985

[Various plasma components and whole blood viscosity in patients with the vascular form of vibration disease].

In 82 men suffering from vascular form of the vibration disease, divided by the degree of its advancement into two groups: I--consisting of 42 persons (average age 40 +/- 7,5 years) at an early stage of the disease and II--consisting of 40 persons (average age 49.7 +/- 5.6 years) with an advanced stage of the disease--the whole blood and plasma viscosity, the plasma fibrinogen level, the total protein level and its fractions and the total cholesterol level were determined. The control group (III) consisted of 100 men in good health (average age 41.3 +/- 8.4 years). The studies showed in both groups with the disease a significant growth of alpha 1, gamma globulins and fibrinogen. It was demonstrated that the increased blood viscosity is--among other things--a consequence of increased plasma viscosity and proteins disturbances.

Blood Proteins↗
PubMed1977

Blood viscosity and local response to cold in primary Raynaud's phenomenon.

Some workers regard whole-blood and plasma viscosity as provoking factors in Raynaud's disease. There was no significant difference, however, in whole-blood and plasma viscosity between ten young women with primary Raynaud's phenomenon and ten age and sex matched controls. Venesection, which reduces plasma viscosity, did not change the ease with which Raynaud's phenomenon was provoked in five patients. Increased viscosity might be a causal factor in secondary forms of Raynaud's disease, but it does not seem to be an important factor in primary Raynaud's disease.

Adult↗
PubMed1975

Multiple myeloma in a patient with sickel cell anemia. Interacting effects on blood viscosity.

Described here is a case of multiple myeloma in a patient with sickle cell anemia. Viscometric studies were made by comparing the patient's whole blood, plasma and washed red blood cells with those of a normal control subject and a patient with sickle cell anemia. Results showed that the increased viscosity of the patient's whole blood as compared with that of the control patient with sickle cell anemia was mainly due to erythrocytic interaction with the circulating abnormal immunoglobulin. It is postulated that the increased frequency of vaso-occlusive crisis that occurred in our patient in the months before the diagnosis and treatment of multiple myeloma, was due to this cell-protein interaction with the resulting enhancement of whole blood viscosity and the sickling phenomena.

Adult↗
PubMed2003

Quantification of the effect of altering hematocrit and temperature on blood viscosity.

Rheological changes occurring with the conduct of cardiopulmonary bypass affect the distribution of blood throughout the cardiovascular system. The purpose of this study was to evaluate the effects of changing physical characteristics of fluid on the dynamics of blood flow in an in vitro model. An extracorporeal model simulating coronary vessel constriction was designed that consisted of tubing with varying internal diameters. Tubing sizes were selected as percentage reductions (11, 33, 56, and 78%) of a normal sized (3.6 mm) coronary artery. Flow rates were randomly varied between 150 and 300 mL min(-1) temperatures of 6 and 37 degrees C, and hematocrits of 0, 20, and 38%. Endpoints included viscosity, pressure drop, and volume distribution. As temperature fell from 37 to 6 degrees C, viscosity increased with hematocrit as follows: 192% at 0%, 225% at 20%, and 249% at 38%, p < .001. Pressure drop increased significantly across each tubing size ranging from 173-351%, p < .01, as fluid was cooled from 37 to 6 degrees C. However, intraconduit statistical differences in volumetric distribution of flow were not achieved. Although the induced hypothermia resulted in increases in resistance, statistical significance was only seen in the smallest lumen conduit. In conclusion, the effects of changing temperature has profound influence on fluid distribution secondary to changing blood viscosity in an in vitro model for fluid distribution. Knowledge of such flow alterations may aid in determining optimal perfusion strategies where vessel constrictions are encountered.

Blood Viscosity↗
PubMed1975

Submaximal blood flow and blood viscosity in newborn infants.

In newborn infants with varying hematocrit values the submaximal blood flow has been studied by the use of strain gauge plethysmography under standardized conditions. Submaximal flow was defined as the flow obtained after 4 minutes of suprasystolic occlusion. With increasing hematocrit there was a decreasing maximal flow. Capillary filtration coefficient seemed to decrease with increasing hematocrit. The relation between circulatory failure in newborns due to abnormally high hematocrit and low capacity to increase blood flow upon demand has been discussed.

Birth Weight↗