Transient kinetics of the rapid shape change of unstirred human blood platelets stimulated with ADP.

Abstract

Transient kinetics of the rapid shape change of unstirred human blood platelets stimulated with ADP (stopped-flow laser turbidimetry/rate constants/contraction/Poisson process)

Dose response of dietary fish oil supplementations on platelet adhesion.

“…17 The mechanism by which n-3 polyunsaturated fatty acids are able to produce the altered pseudopodia forma-tion has not yet been elucidated. We know, however, that fish oil-induced changes in eicosanoid products cannot be responsible for the reduced adhesiveness, as the platelet shape change occurs within fractions of a second after agonist stimulation, 27 -28 long before any thromboxanes are formed. 29 Fish oil-induced effects on platelet function are known to have a delayed appearance and a prolonged washout period.…”

Optimal Efficiency of Human Platelet Shape Changes

“…Light scattering results such as those dis cussed elsewhere in greater detail [1,6,7] suggest the following interpretation of the data. All other things being equal, the magni tude of the extinction coefficient a primarily reflects the discoidity of unstimulated plate lets, and larger values imply an increase in axial ratio [6].…”

“…At least at 37 °C, the body is approximately 'spherical' as the result of the initial reaction step so that pseudopod extension involves an apparent volume change at constant axial ratio [1,6]. The extinction coefficient data (c) seem to indi cate that the body size (effective scattering volume) is smaller at 41 °C, and therefore that more or longer pseudopods are formed at this temperature.…”

“…Platelets exhibit optimum efficiency at 37 °C, as judged by not only the rates of the shape changes but also by alterations in the overall sizes and shapes of the three platelet forms. Unstimulated (discoid) platelets appear to be flatter at 37 °C, the disc to sphere reaction appears to be impaired at other than 37 °C, and the pseudopodia which characterize the final spiny sphere may be more prominent at 41 °C.The shape changes induced in discoid hu man blood platelets by saturating amounts of ADP at 37 °C can be described analytically in terms of three characteristic particle ex tinction coefficients a, b, and c and a single kinetic rate constant k according to the reac tion scheme [1]:The intermediate sphere has a half-life of 4-5 s and is believed to have an axial ratio near 1 and to be devoid of the long pseudo podia that are the outstanding gross morpho logical feature of the final product. The ex periments that led to this description of the platelet shape changes were performed under conditions which permit direct comparison of the particle extinction coefficients and the kinetic constant(s) with values derived from light scattering and reaction rate theories.…”

“…As before [1], freshly isolated platelets from a single normal donor were used, and not less than 450 digitized points were used for curve-fit ting each of the extinction vs. time progress curves. A minimum of 4 repeat experiments were made at each of the temperatures stud- ied, in the sequence 37, 31 or 41, 37 °C in order to ascertain whether the effects of tem perature variation were reversible.…”