Seikichi Suzuki

Augmentation of interleukin 1 and interleukin 2 production by OK-432

Intraperitoneal (i.p.) administration of OK-432 augmented both interleukin 1 (IL-1) and interleukin 2 (IL-2) production to the rechallenge of OK-432 in vitro. Peritoneal exudate cells (PEC) of mice 8 days after i.p. injection with OK-432 (1 KE/mouse) showed maximum IL-1 production to the restimulation with OK-432 in vitro. OK-432-induced IL-1 was consisted of three molecular weight species (two major peaks: 85 K and 15 K daltons and one minor peak: 67 K daltons) on Sephadex G-100 chromatography. Splenocytes of mice 4 days after i.p. injection with OK-432 (1 KE/mouse) demonstrated maximum IL-2 production to the in vitro rechallenge of OK-432, however, in vivo OK-432 administration failed to enhance ConA-induced IL-2 production in vitro. From gel filtration analysis, OK-432 induced IL-2 had an unique molecular weight (approximately 70 K daltons). From these results, OK-432-induced augmentation of cellular immunity against tumor cells might be due to the activation of so-called lymphokine cascade reaction mediated by IL-1 and IL-2.

Isolation of 2.4-Dichlorophenol from a soil fungus and its biological significance

2.4-Dichlorophenol was isolated from the fermented broth of a soil Penicillium. Although some derivatives of 2.4-dichlorophenol were known as synthetic plant hormones, it is the first that 2.4-dichlorophenol was isolated from living world. This fact suggests some derivatives of it are not artifact hormones but growth regulatory hormones of plants as well as gibberellins and cytokinins. The evidence was presented that the fungus produced some derivatives of 2.4-dichlorophenol in addition to stress the biological significance of the isolation.

Studies on Antiviral and Antitumor Antibiotics: Part XII. Effect of Geodin on Virus Multiplication

Antiviral activity of geodin obtained from a soil fungus was studied employing the Newcastle disease virus—chick embryo fibroblasts culture system. In a plate assay method, the minimum inhibitory concentration was about 9 μg/ml and cytotoxicity was detected at 36 μg/ml. Hemagglutinin synthesis was completely suppressed in a tube assay method when 4 μg/ml of geodin was added after the infection (50 plaque forming units/cell), but at this concentration cytotoxic effect of the antibiotic was observed. At sub-inhibitory concentrations, a dose response was shown in the yield of hemagglutinin and infective virus at 16 hr after the infection, and at this time cytopathic effect was partially or completely arrested depending on the antibiotic concentrations even when complete inhibition of hemagglutinin synthesis was not observed. Geodin did not have any effect on the activity of free virus particles and their adsorption to host cells. The inhibition site of geodin exists somewhere between viral adsorption and vir...

Studies on Antiviral and Antitumor Antibiotics: Part XVI. Screening of Antiviral Antibiotics by Paper-disc Agar-diffusion Plaque-inhibition Method

A screening for antiviral antibiotics was carried out using paper-disc agar-diffusion method. The microorganisms tested were unidentified soil fungi and the type cultures of our laboratory including actinomycetes, fungi, yeasts and bacteria. Mycelia or cells were extracted with acetone and the antiviral activity of the acetone extracts was determined. The extracts of actinomycetes mycelia showed the highest frequency of the appearance of antiviral activity against Newcastle disease virus. The frequencies of the appearance of antiviral activity in fungal and bacterial type cultures were the same degree and that of yeasts was low. Antiviral activity of the principles thus obtained was studied by microscopic observation in tube cultures using HeLa cells as a host.