ABSTRACT
The ultrastructure and contractile behavior of a new preparation of thrombin-activated human platelets is described. The preparation is referred to as the "platelet strip" because of its similarities to classical vascular smooth muscle strips. The platelet strip consists of a giant platelet aggregate 10 mm long, 4 mm wide, and 200 micron thick. To facilitate handling, the aggregate has a special high-compliance nylon mesh embedded in its mass. Each strip contains 7.3 X 10(8) platelets. Fibrin contamination is 150-fold lower than in platelet-rich plasma clots. Active isometric forces of up to 100 g/cm2 and 6-10 h viability are easily and reproducibly obtained. Platelet strips remain contracted after thrombin activation. The contraction is tonic and partial. Further small increases in force can be produced by depolarizing solutions or pharmacological agents, e.g., ADP, epinephrine, and endoperoxide analogues. These small increases are reversible on washout of the agents. Full relaxation is induced by agents such as prostaglandin E1 or papaverine, which increase adenosine 3',5'-cyclic monophosphate. However, after washout of these agents, recovery of tension is variable depending on the concentration of the drug and the degree of prestretching of the preparation.
Subject(s)
Blood Platelets/physiology , Clot Retraction , Fibrin/physiology , Platelet Aggregation , Thrombin/physiology , Alprostadil , Blood Platelets/drug effects , Blood Platelets/ultrastructure , Epinephrine/pharmacology , Epoprostenol/pharmacology , Humans , In Vitro Techniques , Kinetics , Microscopy, Electron , Models, Biological , Nylons , Papaverine/pharmacology , Prostaglandins E/pharmacologyABSTRACT
Pupillometry in clinical investigation and in basic research often requires dynamic measurement of pupil size. Static methods, i.e. direct observation and still photography, are often used because of the high cost of commercial infrared pupillometers and problems with pupil-iris contrast in small animals. This report describes an improved infrared video pupillometer (IVP) which accurately measures the pupil area of small animals in real time (30 samples/sec). Two components of the pupillometer were designed and built by the authors: a "bright-pupil" infrared illumination system and a digital video signal processor (VSP). The use of a standard closed-circuit television camera to produce the pupil image signal results in a device that is relatively economical to construct. The IVP is sensitive enough to accurately track pupil are in the study of the pupil light reflex or pupillary oscillations. Several applications for the IVP are illustrated, including analysis of the transient response to light flashes and intravenous injections of drug, and analysis of the spontaneous and drug-induced pupillary fluctuation. Pupillography has been applied in the bioassay of various psychopharmacologic compounds and in the assessment of narcotic dependency. This IVP is being used in this laboratory to study the pupillary action of opiates in the rabbit and rat.
