Chronic blood hyperviscosity in subjects with acute stroke, transient ischemic attack, and risk factors for stroke.

The origin and significance of blood hyperviscosity in subjects with acute stroke has been controversial. It has been argued that viscous abnormalities simply reflect either elevated hematocrit or an acute-phase response to the stroke itself. To address these issues, we measured the factors that determine blood viscosity in a cross-sectional study of 430 subjects, including 135 with acute stroke, 89 with acute transient ischemic attacks of the brain, 115 with recognized risk factors for stroke, and 91 healthy controls. The at-risk group was balanced with the acute stroke group for types of risk factors and medication usage, and all four groups were balanced for age. The viscosity of whole blood at low rates of shear and the plasma viscosity were significantly elevated in both groups with cerebrovascular symptoms and in the at-risk group compared with the healthy controls. The severity of hyperviscosity was stroke group greater than transient ischemic attack group greater than at-risk group greater than healthy controls. Increased viscosity of whole blood was associated with an elevated plasma fibrinogen concentration and with a decreased albumin/globulin ratio. This study provides evidence that blood hyperviscosity is present not only in subjects with acute brain infarction, but also in those with risk factors for stroke, and that these abnormalities are, to a considerable degree, chronic.

Elevated plasma homocyst(e)ine concentration as a possible independent risk factor for stroke.

Homocyst(e)ine refers to the sulfur-containing amino acids homocysteine, homocystine, and homocysteine-cysteine mixed disulfide, which normally exist in plasma in both the free and protein-bound forms. Marked hyperhomocyst(e)inemia is associated with well-recognized complications of occlusive thrombotic events and a characteristic syndrome. It is less clear whether mild to moderate elevations in plasma homocyst(e)ine concentrations (i.e., 1.5-5-fold increases) also represent a risk factor for stroke and, if so, whether it is independent of other recognized risk factors. To examine these questions we compared the plasma homocyst(e)ine levels in 41 patients with acute strokes, 27 patients with transient ischemic attacks, 31 patients with recognized risk factors for but no recent symptoms of cerebrovascular disease, and 31 normal volunteers (controls). Plasma homocyst(e)ine concentration was moderately but significantly higher in the patients than in the controls (p less than 0.0001). Approximately 30% of the patients had homocyst(e)ine levels higher than the controls. No relation was found between homocyst(e)ine concentration and other recognized stroke risk factors or stroke type; however, a positive correlation was found between serum uric acid and plasma homocyst(e)ine levels. These data suggest that a moderately elevated plasma homocyst(e)ine concentration may be an independent risk factor for cerebrovascular disease.

Influence of naftidrofuryl, a serotonergic antagonist, on erythrocyte aggregation.

Erythrocyte aggregation is an important determinant of the rheological behavior of blood and may play a critical role in nutritive tissue perfusion at the level of the microcirculation, particularly in situations of low flow. Thus, abnormal red blood cell aggregation may contribute to the pathophysiology of a variety of vascular diseases with associated microcirculatory disturbances. The action of serotonergic antagonists has a hemorheological component, although red blood cell aggregation specifically has not been addressed previously. Therefore, the effect of naftidrofuryl, a 5-hydroxytryptamine-2 receptor antagonist (5-HT2), on erythrocyte aggregation was studied in whole blood obtained from adult human volunteers. Red blood cell aggregation was measured using a Myrenne aggregometer the operation of which is based on nephelometric principles. The results demonstrate that red blood cell aggregation is significantly reduced in comparison to controls on incubation of whole blood in the presence of naftidrofuryl. This inhibitory effect is concentration dependent and reaches a maximum (approximately 30%) between 1 and 10 microM naftidrofuryl. Furthermore, naftidrofuryl (5 microM) also inhibits red blood cell aggregation in the presence of exogenously added serotonin (1 microM) on average by approximately 18%. Significant inhibition of red blood cell aggregation could not be observed in similar experiments using whole blood suspensions essentially devoid of platelets, suggesting that these blood cellular elements are involved in mediating the effects of naftidrofuryl.

The importance of formaldehyde purity in studies on the electrokinetic charge of human red cells.

Electrokinetic measurements and rheological studies conducted in parallel have previously shown red cell surface charge to play a role in governing aggregative behavior and bulk flow properties of red cell suspensions. For these and other types of model investigations, aldehyde stabilized cells have been widely used. In this communication, the influence of the purity of formaldehyde was investigated. It was found that (a) the direct dissolution of commercially available paraformaldehyde in water or suitably buffered saline results in impure solutions which, if utilized in the fixation of human erythrocytes, produces cells which have significantly different electrophoretic properties from native cells; (b) the basis for the differences is the presence of metallic impurities in some commercially available paraformaldehyde preparations; (c) the impurities and thus the anomalous electrokinetic properties of the fixed cells may be eliminated by generating formaldehyde gas from paraformaldehyde by heating the latter to 203-210 degrees C; (d) alternatively, the impurities may be eliminated by addition of disodium ethylenediamine tetraacetate dihydrate to fixative solutions prepared directly from paraformaldehyde.

Correlation between cell deformability and metastatic potential in B16-F1 melanoma cell variants.

Four B16 melanoma cell variants were investigated to determine if there exists a correlation between their deformability and their metastatic potential. Cell deformability was measured as the percentage of cells traversing 10-mum diameter Nuclepore filter membranes at constant pressure as a function of time. A method was devised to circumvent common problems encountered in cell filtration experiments, i.e., cell aggregation and adhesion to the filter and failure to recover the input. F1a cells with the lowest spontaneous metastatic rate required 44 s for 50% of the cell input to traverse the filter, whereas No. 4 cells, featuring the highest metastatic rate, needed 12 s despite the fact that the cells had identical dimensions. Other variants tested showed intermediate filterability which also correlated with their metastatic potential. Cells, when pretreated with cytochalasin B at a final concentration of 21 microM exhibited increased filterability (75% and 42% greater than control for F1a and No. 4 cells, respectively). Somewhat smaller increases were observed after colchicine treatment. The findings imply major involvement of the cytoskeleton in the filterability and thus deformability of these B16 variants. Such physiochemical factors may play an important role in the metastasis of this and possibly other tumor types.

Sialidase treatment of rat-erythrocytes: a model for cellular aging?

An in vitro assay system was developed to test the propensity of "old" and sialidase-treated rat erythrocytes to be bound and phagocytosed by rat peritoneal macrophages. Cells considered to be old were phagocytosed to a greater degree than those considered to be young. When erythrocytes were treated with immobilized Vibrio cholerae sialidase, higher amounts of sialic acids had to be removed (25--30%) to induce binding and phagocytosis of the cells, than if the cells had been treated with soluble enzyme (9--15%).

Red cell aging. II. Anomalous electrophoretic properties of neuraminidase treated human erythrocytes.

Desialylation of human red blood cells (RBC) by Vibrio cholerae neuraminidase (VCN) was found to produce cells with electrophoretic properties which were inconsistent with the view of simple loss of N-acetylneuraminic acid (NANA) as the sole effect of VCN treatment. Modification of human RBC with 50--350 U VCN/10(10) RBC for one hour at 37 degrees C releases 90-100% of the NANA and produces a progressive decrease towards zero in their electrophoretic mobilities when measured in 0.15 M NaCl (pH 7.2) at 25 degrees C. The appearance of positive groups on the desialylated cells was indicated by the VCN-treated cells displaying positive mobilities below approximately pH 5.5 and increased negative mobilities at approximately pH 9 as well as substantial increases in their mobility at neutral pH following treatment with formaldehyde. Adsorption of about 95% of the VCN activity at 0 degrees C to the RBC did not produce any significant change in their electrophoretic mobilities thus indicating that the observed changes in the electrophoretic properties of the RBC following VCN treatment could not be attributable to adsorption of VCN. These studies indicate that the cationic charge groups which appear at the electrophoretic surface of the RBC after VCN treatment are probably of endogenous origin. It is suggested that this alteration rather than simple NANA release may operate to shorten the in vivo survival time of desialylated red cells.