Trapping of calibrated microspheres in rat lymph nodes
The diagnostic and therJpeutic usefulness of intralymphatic microspheres depends on the site and duration of lodgement of the injected particles within the lymph nodes. The size of the spheres is probably the most important factor that determines where and for how long the particles will remain trapped. This study was carried out to test, under controlled conditions, the filter capacity of lymph nodes for spheres of various calibers. Materials and methods Microspheres. -Sterile, I
... le, I nonradioactive, complete spheric, homogeneous ceramic microspheres (3 M Co., St. Paul) were used. The size of the microspheres had been designated as 5 to 10 µ, 15 ± 5 µ, 25 ± 5 µ, 35 ± 5 µ, and 50 ± 10 µ. The spheres were kept in a 100/o dextran solution. Animals. -A total of 229 male, albino Sprague-Dawley rats, weighing 250 to 350 gm were used. They were housed under standard conditions at a temperature of 72 F, with free access to a standard laboratory pellet diet ( Rockland) and water. For injections of microspheres, the rats were anesthetized with a solution of pentobarbital (Pentobrocanal) administered intraperitoneally in a dose of 4 mg/100 gm of body weight. They were killed with ether in groups of 6 to 12 animals at time intervals of 4 hours and 1, 2, or 7 days. A complete autopsy was done on each animal, and all regional nodes were removed for histologic study (Fig.