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Some strains of Gibberella fujikuroi (Saw.) Wr. (conidial state Fusarium moniliforme (Sheld.) emend. Snyder & Hansen) produce metabolic products with plant‐growth‐promoting properties. The capacity to produce such substances is common in rice‐infecting strains of G. fujikuroi; isolates from other hosts only infrequently produce such metabolites. From a selected rice‐infecting strain a plant‐growth‐promoting substance has been isolated in pure form. This substance, gibberellic acid, is distinct in chemical properties from the gibberellins described by Japanese investigators. In surface culture on Raulin‐Thom medium (2.5% sucrose) yields of 40 mg./1. are obtained in 14 days at 25°. In submerged aerated culture yields approaching 200 mg./1. are obtained on Raulin‐Thom medium (4% sucrose) in 18 days at 25°. Under such conditions, although gibberellic acid begins to appear in the medium during the latter part of the phase of active growth, at least 75%, and probably more, of the total final yield is produced after maximum dry weight has been reached and rapid uptake of sugar and ammonia‐nitrogen has ceased.

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Hepatocytes from fasted rats, previously maintained as a monolayer in a serum-free glucagon-containing culture medium are demonstrated to provide a useful model system for the study of receptor-mediated mechanisms of insulin action. The cultured liver cells show glucagon- and insulin-responsive biological effects. These cultures show the long-term effects of insulin on the syntheses of protein ([3H]leucine incorporation), glycogen, and lipids (conversion of [3H]glucose) in a dose-dependent manner in the physiological range of insulin concentrations. The order of the effects of different analogues of insulin on each of the bioactivities studied at 37 degrees C is the same as their order to compete at 25 degrees C for binding to insulin-specific receptors. The characterization of radioactive products of 125I-insulin using gel filtration and anti-insulin A chain antibody has shown a transient accumulation of insulin A chain, indicating that the sequential pathway of insulin degradation is operative in the anchored, cultured hepatocytes. Whereas the synthesis of proteins proceeds linearly after insulin inoculation, the syntheses of glycogen and lipids first occur after a lag period of about 10 and 12 h, respectively. None of the three 125I-labeled fragments or products of 125I-insulin released in the culture mediums showed any biological activity (glycogenesis) in cultured hepatocytes although a high-molecular-weight 125I-product isolated from cells could not be tested because of its insolubility. The possibility that the insulin effects might have been mediated via a nonradioactive fragment of insulin or another chemical agent remains open.