Lewis W. Mayron

Definition of myocardial perfusion by continuous infusion of krypton-81m

Krypton-81m, a radionuclide emitting a 190 kev gamma ray, has a half-life of 13 seconds. It is a radioisotope of an inert water-soluble noble gas and is produced at a constant rate by spontaneous decay of rubidium-81 in an 81Rb-81mKr generator-delivery system. Delivery is through a minibore Teflon catheter that can be threaded through a standard no. 7 or 8F angiographic catheter. The generator is eluted by 5 percent dextrose-in-water, delivered by infusion pump at 1.5 ml/min, and the eluate is infused intraarterially directly into any organ. Delivery and decay reach equilibrium within 2 minutes, producing a heterogeneous distribution that is proportional to the perfusibility of the tissue concerned and the time required to reach it. The ultrashort halflife of the radionuclide rapidly eliminates activity when delivery ceases; thus, experiments can be sequentially repeated at brief intervals. The radiation hazard for easily imaged doses is negligible. Preliminary studies in open chest dogs were visualized by scintillation camera, stored on digital data disk, processed, and displayed in dual channel, dual color mode on a video system. Images of myocardial perfusion defined relative levels of perfusion, collateral circulation between coronary arterial branches, equilibrium time of diffusible perfusion of the myocardium, focal defects in induced occlusion, collateral circulation to occlusion, and reactive hyperemia after release of induced coronary occlusion. The system and technique appear applicable to human subjects.

Evaluation of perfusion with the 81Rb-81mKr generator

The development of the 81Rb-81mKr generator-delivery system has made available an ultrashort (13-sec) half-life radionuclide for continuous, constant-rate delivery as a gas, or as an isotonic, nonionic solution in 5% dextrose and water. This system has been evaluated and applied to the scintigraphic imaging of various organs and anatomic regions by intravenous and intraarterial infusion and by inhalation and deglutition. This diffusible, noble gas is inert chemically and biologically. When the gas is administered intraarterially, the volume of tissue being perfused may be defined with the scintillation camera. The 13-sec half-life is of a similar magnitude to the rate of capillary exchange, producing a heterogeneous image with steady-state administration in which the intensity of detectable radioactivity is proprotional to the time of diffusion into the tissue. This system appears capable of defining the rate of capillary exchange and the moment-to-moment changes brought about by vasoactive stimuli in specific organs.

Opsonic Characteristics of Chylomicron-Bound Protein

Summary A blood protein in complex with native chylomicrons was labeled with radiogold colloid, thus indirectly identifying the protein material in the complex as op-sonin and suggesting the possibility that native chylomicrons may utilize the opsonin system for its clearance from the circulation. The protein in question has been shown to be at least divalent, in that the protein in com-binaton with one type of particle could still react with another. It is felt that these studies provide further insight into the complex surface events that result during the process of opsonization.

Protoplasmic Extrusion of Pollen Grains—an Electron Microscope Study

Summary Protoplasmic extrusion has been described previously and has been shown to be at least partly influenced by the salivary contents. An electron microscope study is hereby presented. These results demonstrate an active participation of pollen components in this process.

‘Halo formation’ as a characteristic of the interaction between ragweed pollen and saliva

Wenn Pollen vonAmbrosia rifida mit dem Speichel von mit Allergie belasteten Personen zusammen kultiviert wird, so entsteht um die Pollenkörner ein Hof («halo»), was in Kulturen von nicht allergischen Personen nicht der Fall ist.