A newpeptide antibiotic, cypemycin, with a molecular weight of 2,097 (M +H), was isolated from the culture broth of Streptomyces sp. OH-4156.The antibiotic possesses cytocidal activity against P388 leukemia cells in vitro at a concentration of 1.3 //g/ml (IC50 values), and the antibiotic showed antimicrobial activities against Micrococcus luteus (MIC, 0.2 /jg/ml).In the course of a screening program for novel antibiotics showing cytocidal activity, cypemycin was isolated from the culture broth of Streptomyces sp. OH-4156 which had been isolated from a soil sample collected in Tokyo, Japan. The antibiotic exhibited cytocidal activity against mammalian tumor cells in vitro, and antimicrobial activity against Micrococcus luteus.The present paper deals with taxonomic studies of the producing strain, and the production, isolation and physico-chemical properties of the new antibiotic. The preliminary biological activities of cypemycin are also described.
Materials and Methods General Experimental ProceduresSilica gel 60 (Merck) and Sephadex LH-20 (Pharmacia Fine Chemicals) were used for column chromatography and pre-coated TLCplates of Silica gel 60 (Merck) was used for TLC analysis.
Taxonomic StudiesThe type diaminopimelic acid (DAP) was determined by the method of Takahashi et al}\ To investigate the cultural and physiological characteristics, the International Streptomyces Project (ISP) media recommended by Shiriling and Gottlieb2) and those recommended by Waksman3) were used. Cultures were observed after incubation at 27°C for 2 weeks. Color names and hue numbers indicated in Table 1 are those of the Color Harmony Manual (4th Ed.)4). The utilization of carbon sources was tested by growth on Pridham and Gottlieb's medium5) containing a 1%carbon source at 27°C.
Cytotoxic Activity TestsSeven strains of established mammaliancells were maintained in monolayers or in suspension in Eagle's minimum essential medium (MEM)supplemented with 10% bovine serum and kanamycin (60 Atg/ml). To determine the cytotoxicity of cypemycin, cells suspended in 200 /zl of the medium were plated in a 96-well culture plate (Falcon) and incubated for 24 hours at 37°C in a 5% CO2-95%air atmosphere. To each well was added 5 fi\ of medium containing a different concentration of cypemycin. After 72 hours of incubation, the cell growth was evaluated by the method of Miravelli et al.6\
Dry drilling of composite/metallic stacks for aircraft components is extremely difficult to keep sufficient hole quality and efficiency of drilling process. Problems of the dry drilling of those kinds of stacks are chip ejection, chip formation and high temperature especially for titanium alloy. To clear these problems, low-frequency vibration (10-50 Hz) drilling is proposed in this study. Controlled sinusoidal vibration was given in drill axis direction with constant feed motion. The relationship between vibration conditions, such as vibration amplitude, frequency and drill feed rate, and chip formation and drilling temperature were investigated. As a result, low-frequency vibration drilling can control chip formation to reduce chip jamming and can reduce drilling temperature. Temperature measured at the cap burr decreased by 300 degrees C or more when low-frequency vibration was applied compared with the conventional drilling. Also the wear rate of the drill is decreased when the vibration is applied.
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