Factors influencing in vitro production of colony-stimulating factor by mononuclear leukocytes from humans.

The purpose of this study was to identify factors that influence the production of colony-stimulating factor by leukocytes of humans. The use of nonadherent light-density bone marrow cells is semisolid agar cultures to assay the concentrations of colony-stimulating factor in the supernatant of monocyte and mononuclear leukocyte cultures made it possible to distinguish between colony-stimulating factor, which stimulates colony-forming cells directly, and monocyte-dependent stimulating activity, which acts indirectly, by increasing the monocyte production of colony-stimulating factor. Colony-stimulating factor was not detectable in the cytosol of monocytes; that detected in culture must, therefore, have been newly synthesized. Synthesis was enhanced independently by heat-inactivated human serum and by semipurified serum fractions enriched with monocyte-dependent stimulating activity. The kinetics of the production of colony-stimulating factor in the presence and absence of monocyte-dependent stimulating activity indicated that the latter facilitated monocyte production of the former. Factors released from neutrophils were shown to reduce the production of colony-stimulating factor and thr proliferation of colony-forming cells and thus may provide a feedback control mechanism limiting the proliferation of neutrophils.

The stability of porphyrin and metalloporphyrin molecular complexes in solution.

Stability constants for the molecular complexes formed by protoporphyrin IX dimethyl ester and its metal chelates with Co2+, Ni2+, Cu2+, Zn2+, Mg2+ and Fe3+ with nitroarene acceptors are determined in non-aqueous solvents. The stability of the complexes is found to be largely insensitive to variations in the central metal ions provided they are in the same oxidation state. Solvent-solute interactions are seen as being important in the formation of such complexes giving rise to large variations in their apparent stability. Some of the other factors that affect the stability of the molecular complexes are also evaluated. No evidence has been found for the appearance of any intermolecular charge-transfer absorption bands. Infrared studies, however, have provided some evidence for a substantial loss of electron density from the porphyrin ring upon interactions with the acceptors.