Effect of aggregating agents on the electrophoretic mobility of human platelets

Potential high virulence for infective endocarditis in Streptococcus mutans strains with collagen-binding proteins but lacking PA expression

OBJECTIVE

Streptococcus mutans, an aetiologic agent of dental caries, is a pathogen for infective endocarditis (IE). We investigated strains that express collagen-binding proteins (CBPs) with further classification based on expression of the 190-kDa protein antigen (PA).

METHOD

Zeta-potential values of strains TW871 (CBP+/PA+) and MT8148 (CBP-/PA+), and their respective PA-defective mutant strains TW871PD (CBP+/PA-) and MT8148PD (CBP-/PA-), were analysed, as were their adhesion to and invasion of human umbilical vein endothelial cells (HUVECs). The distribution of strains from the oral cavities of 200 healthy individuals was analysed for CBP and/or PA expression and the strains were characterised for their adhesion and invasion properties.

RESULTS

TW871PD and MT8148PD showed significantly lower zeta-potential values than TW871 and MT8148, respectively. Collagen-binding rates were significantly higher for TW871PD than for TW871 but nearly negligible for MT8148 and MT8148PD. The adhesion and invasion rates of HUVECs were significantly higher for TW871PD than for TW871 and significantly higher for TW871 than for MT8148 and MT8148PD. The prevalence of CBP+ strains was ~10% and ~3% in the case of CBP+/PA- strains. Analyses of 200 clinical strains showed the CBP+/PA- group to have higher adhesion and invasion rates than other groups.

CONCLUSIONS

CBP+/PA- S. mutans strains, despite their low distribution frequency, may be highly virulent for infective endocarditis.

The collagen-binding protein of Streptococcus mutans is involved in haemorrhagic stroke

Although several risk factors for stroke have been identified, one-third remain unexplained. Here we show that infection with Streptococcus mutans expressing collagen-binding protein (CBP) is a potential risk factor for haemorrhagic stroke. Infection with serotype k S. mutans, but not a standard strain, aggravates cerebral haemorrhage in mice. Serotype k S. mutans accumulates in the damaged, but not the contralateral hemisphere, indicating an interaction of bacteria with injured blood vessels. The most important factor for high-virulence is expression of CBP, which is a common property of most serotype k strains. The detection frequency of CBP-expressing S. mutans in haemorrhagic stroke patients is significantly higher than in control subjects. Strains isolated from haemorrhagic stroke patients aggravate haemorrhage in a mouse model, indicating that they are haemorrhagic stroke-associated. Administration of recombinant CBP causes aggravation of haemorrhage. Our data suggest that CBP of S. mutans is directly involved in haemorrhagic stroke.

The risk factors associated with both ischemic and haemorrhagic stroke are not fully understood. Here a certain strain of the bacteria, Streptococcus mutans, which expresses a collagen-binding protein, is shown to be associated with haemorrhagic stroke in both animal models and human patients.

Measurement of the zeta potential of human platelets by the use of laser-light scattering

An instrument was developed to detect the shift in scattering of laser light that occurs when particles in suspension move in a chamber with an electrical load. The instrument measures the zeta potential of particles. We applied the instrument to study human blood cells. Platelet-rich plasma was used because of the stability of the suspension, without the sedimentation or autoaggregation that is often seen with red or white blood cells. The reproducibility of the measurements was satisfactory when there were enough platelets in the suspension. Platelets from healthy controls (n = 136) had a potential of -14.20 +/- 1.64 mV at the detection angle of 17.1 degrees. Platelets from patients with essential thrombocytosis (n = 16) or polycythemia vera (n = 8) had higher potentials than the healthy controls.

Standardization of platelet function tests

Methods for the standardization of several currently used platelet function tests (bleeding time, capillary fragility, platelet retention, platelet aggregation, platelet factor 3, and platelet volume profiles) are presented, Different variables than may interfere with the reproducibility of the results of each assay were identified and standardized. Using the standardized techniques, the range of normal values for each test was determined in a large population of normal volunteers and used to identify disease states by comparing patient results with those of the normal population. A format for presenting the entire profile of platelet function parameters is proposed.

Influences of prostaglandins on electrophoretic mobility and aggregation of rabbit platelets

Influences of prostaglandin (PG)s on electrophoretic mobilities and aggregation of rabbit platelets were studied. The PGs studied (PGI2, PGE1, PGD2, PGF2 alpha, PGA2 and PGA1) had no effect on platelet electrophoretic mobility. However, both PGE1 and PGI2 in 0.3 and 3.0 muM inhibited ADP-induced aggregation and ADP-induced decrease in the mobility. PGD2 in 0.3 and 3.0, and PGE2 in 30 microM inhibited the aggregation but did not depress the ADP-induced decrease in the mobility. PGF2 alpha, PGA2 and PGA1 had no effect on the decrease in electrophoretic mobility and on the aggregation caused by ADP.

Effect of a new antiaggregating chemical on the structure and function of the human platelet

A new antiaggregating chemical, alpha-(p-(fluoren-9-ylidenemethyl)phenyl)-2-piperidineethanol (RMI 10,393), designated FYPE, was found to be an effective inhibitor of platelet aggregation induced by adenosine diphosphate (ADP), thrombin, collagen, or epinephrine. Effects of the antiaggregant on platelets were concentration dependent. Aggregation was prevented by low concentrations of FYPE that produced in the platelet only minor ultrastructural changes consisting of loss of microtubules and of discoid shape. Low levels of FYPE that prevented platelet aggregation had no effect on platelet ATPase activities but did alter clot retraction, the thrombin-induced shift in electrophoretic mobility and platelet cholinesterase activity. Market decrease in ADP release and increase in adenyl cyclase activity were produced by low levels of FYPE. This study provides a model for evaluation of platelet antiaggregating compounds in vitro.

Acanthocytosis with normolipoproteinaemia: biophysical aspects

The electrokinetic properties of normal and pathological red cells and platelets are compared.

The electrophoretic mobilities and isoelectric points of normal and pathological erythrocytes do not differ significantly, adsorption of calcium and uranyl ions occur to the same extent and treatment with neuraminidase induces almost identical mobility decreases.

The pathological platelet-plasma system is more sensitive to adenosine diphosphate (ADP) than normal systems; platelet aggregation and electrophoretic mobility increases are induced by much lower concentrations of ADP than those normally required. The pathological platelet system shows a greater tendency to aggregate spontaneously. The abnormal sensitivity to ADP of the pathological platelet-plasma system is considered in terms of plasma components.

Platelet aggregation and the platelet release reaction in thromboembolism

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Coumarin therapy and platelet aggregation

Platelet aggregation has been related to blood coagulation studies in patients on nicoumalone, a coumarin anticoagulant. Aggregation studies were performed by means of Chandler's tube and the adenosine diphosphate (A.D.P.)-induced optical density method. Platelet aggregation in Chandler's tube has been shown to be quite different from A.D.P. aggregation and to be dependent on the "intrinsic" (blood) clotting system. When the intrinsic system was depressed by coumarin anticoagulant, aggregation was delayed in Chandler's tube, but patients with a predominantly "extrinsic" (tissue) system defect gave normal results even when their prothrombin time was excessively prolonged. In contrast there was an increased response to A.D.P. in the anticoagulated patients.The study emphasizes the different mechanisms of platelet aggregation, which we have referred to as coagulation-induced and A.D.P.-induced aggregation. It also shows the limitations of routine control of oral anticoagulants by prothrombin time alone, as the coagulation-induced platelet aggregation appears to be quantitatively related to the overall level of clotting factors in the intrinsic system and independent of the extrinsic system.

Thrombosis in coronary heart disease

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