RESUMO
We have developed a rapid and convenient method for determining the rate constant of association of single platelets. Using the concentration of single platelets prior to activation and that 0.25 min (15 s) after activation, this rate constant can be determined accurately without concern for reversibility of the aggregation process or need for statistical analysis. A linear relationship between initial platelet concentration and the rate constant of association is defined. The clinical utility of this association parameter is discussed.
Assuntos
Plaquetas/fisiologia , Agregação Plaquetária/fisiologia , Difosfato de Adenosina/farmacologia , Plaquetas/efeitos dos fármacos , Epinefrina/farmacologia , Humanos , Técnicas In Vitro , Cinética , Agregação Plaquetária/efeitos dos fármacosRESUMO
This study shows that microscopic image analyses of nuclear DNA have common characteristics among fixation methods and tissue types. We find that microscopic imaging measurements require both nuclear area and DNA concentration to properly convey diagnostic information. Algorithms are developed which enable infiltrating lymphocytes to act as internal DNA controls for each sample. The DNA content and patterns measured by microscopic imaging were found to be related to patient survival and to cytologic diagnosis.
Assuntos
Núcleo Celular/análise , DNA de Neoplasias/ultraestrutura , Processamento de Imagem Assistida por Computador , Microscopia/métodos , Neoplasias Nasofaríngeas/genética , Algoritmos , Humanos , Linfócitos/análise , Neoplasias Nasofaríngeas/mortalidade , Ploidias , Análise de SobrevidaRESUMO
A compartmental model of platelet aggregation which accurately describes both reversible and irreversible aggregation in vitro is presented. This model is substantiated by correlative analyses of agonist-induced aggregation as monitored by both routine aggregometry and resistive counting of single platelets. Previously unresolved differences in the reported reaction order of the aggregation process are explained. The model suggests that aggregation includes, in addition to the association and dissociation of platelets, the stabilization of aggregates. We find reversible aggregation requires that single platelets associate more rapidly than aggregates stabilize. For irreversible aggregation, our results suggest the presence of subpopulations of single platelets which associate at different rates. As an unexpected consequence of this study, quantitative relationships between photometric and resistive methods of monitoring platelet aggregation are elucidated.
