Abstract
Evidence that cells are released from normal (4, 11) or virus-induced leukemic (3) hematopoietic tissues in organ culture has been repeatedly reported.
Over the past few years, a technique which allows a more accurate cytological study of these “free” cells has been developed (6). This method involves the recovery of cells egressing from hematopoietic explants on a protecting silicone membrane since hemic cells in contact with these membranes retain their morphological differentiation for prolonged periods of time (8).
Studies presented here have shown that in the cell populations collected from newborn mouse spleen explants under these conditions, large numbers of granulocytic cells are present, in particular, during the early period of incubation. In addition, these experiments indicate that the removal of these free cells by collecting them on silicone membranes stimulates long-term granulopoiesis in these cultures.
Materials and Methods. Explants. Spleens are removed from BALC/c newborn mice less than 24 hr of age after the animals have been sacrificed by ether anesthesia and ex-planted in toto after cleaning them from surrounding attached tissues.
Culture technique. The organ culture method in perfusable chambers has been described in detail earlier (7). Briefly explants are cultivated on a millipore filter (HA 450 nm) inserted between two nontoxic synthetic rubber (Pluribar 5 ) gaskets forming the walls of the chamber which is completed by a glass bottom and lid. The whole is held together by a special metallic device. Two ml of medium are injected through the wall of the lower compartment, filling it up and moistening the millipore filter. Most explants are covered with a “blanket” of silicone membrane prepared as mentioned below. Cultures are incubated in an ordinary atmosphere at 37°.
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