Effects of kinetin and gamma radiation on the growth and chlorophyll synthesis of isolated radish cotyledons

Seeds of Raphanus sativus L. were irradiated with 120 and 240Kr of gamma rays from a ¹³⁷Cs source. Chlorophyll synthesisand fresh weight increases (an estimate of cell expansion) ofisolated cotyledons proved to be radioresistant processes. Alag phase in chlorophyll synthesis, removable by kinetin (10mg/liter), was observed. Gamma radiation decreased the reactivityto kinetin in the removal of the lag phase, but did not affectthe kinetin-stimulated fresh weight increase both in light anddark. Addition of 8-azaguanine to the incubation media reducedthe kinetin-stimulated fresh weight increase. This inhibitionwas significantly enhanced by gamma radiation when the cotyledonswere incubated in light. (Received February 22, 1978; )     

Lectin specificity and binding characteristics of human C-reactive protein.

C-reactive protein (CRP) is thought to play an important role in immunomodulation. The exact biologic function of this pentraxin protein is, however, still unclear. Here we report experiments designed to further characterize the binding properties of CRP. Using purified human CRP it could be shown that CRP immobilized onto polystyrene surfaces or onto latex beads binds distinct plasma glycoproteins including IgG, asialofetuin, asialo-beta 2-glycoprotein I and, likewise, synthetic glycoproteins as a lectin, exhibiting binding specificity for terminal galactosyl residues of the glycoprotein glycans. Binding of CRP to IgA, IgM, IgG, asialofetuin, asialo-beta 2-glycoprotein I and to synthetic glycoproteins requires immobilization onto surfaces of both CRP and the ligand. Fibronectin and fibrinogen are bound by surface-immobilized CRP also in soluble phase. Comparing various mono-, di-, and trisaccharides as competitive inhibitors of the lectin binding activity of CRP, only beta-D-Gal-(1-3)-D-GalNAc, beta-D-Gal-(1-4)-D-GalNAc, and beta-D-Gal-(1-4)-beta-D-Gal-(1-4)-D-GlcNAc had significant inhibitory power at a concentration of 8 mmol/liter. Binding activity of CRP was pH-dependent with an optimum at pH 5 to 6 and was reduced by 90% when pH was shifted from 6 to the physiologic pH value of 7.4. CRP exhibited lectin-like properties with binding specificity for galactosyl residues also when bound to K-562 erythroleukemia cells. It is therefore suggested that CRP immobilized onto surfaces exhibits lectin activity toward galactosyl groups preferentially in a mildly acidic environment as present at sites of inflammation.