Since oxygen, especially its metabolic products, hydrogen peroxide and superoxide anion, are cytotoxic, we intended to culture cells under reduced oxygen concentration in order to examine biological effects of oxygen on cells. For this purpose, a new type of nitrogen gas generator was constracted and connected to a CO₂ incubator to reduce oxygen concentration less than 20%. The mechanistic principal of the generator is to remove oxygen from the incoming air using an adsorption column with carbon molecular sieves (CMS) and to obtain almost 100% pure nitrogen gas. Plating efficiencies and growth rates of various types of cells were tested under reduced oxygen conditions. As a result, most of the cell lines examined showed higher plating efficiency and growth rate compared with under conventional culture conditions at a humidified atmosphere of 95% air and 5% CO₂. The use of this new type of the nitrogen gas generator has the following merits: 1) no need to use N₂ gas cylinder,2) no need to daily check the cylinder,3) no frequent exchange of empty cylinder,4) no troublesome labor for its exchange,5) suitable for study of oxygen effects on cells.

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In this report, we studied effect of monoclonal antibody (MoAb) to EGF-r designated as 12-93 on the growth of squamous cell carcinoma cells (SCC) and salivary gland adenocarcinoma cells (SAC) in vivo, and targeting immunotherapy using 12-93 MoAb-conjugated LAK cells against oral cancer cells in vitro. A 12-93 MoAb inhibited the growth of SCC and SAC in vivo. The 12-93-conjugated LAK cells showed significantly enhanced cytolysis of 12-93 reactive A431 and HSG cells but not Raji cells which dose not react with 12-93. These results indicated that 12-93 will be a viable alternative to tumor specific MoAb and 12-93-conjugated LAK cells may provide an effective strategy for targeting adoptive immunotherapy of cancer.

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Increase in the incubation temperature of infected Aedes albopictus clone C6/36cells from its optimal growth temperature of 28°C to 32 and 37°C showed a concomitant rise in the production of dengue virus type 2 antigen and genomic RNA. The quantitative reverse transcription-polymerase chain reaction using an internal standard as a measuring tool for the viral genomic RNA showed that RNA production was higher in the cells and in the extracellular fluid from the cultures incubated at 32 and 37°C than at 28°C. The presence of viral antigen and viral genomic RNA was also detected 1-2days earlier in the cultures incubated at elevated temperatures.

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Combined effects of methyl methanesulfonate (MMS) and ethyl methanesulfonate (EMS), which were administered successively for each 3 h at different times, or with an interval time of incubation in normal medium for 3 h between treatments with two chemicals were examined on survival and induction of 6TG-resistant and OUA-resistant mutations in Chinese hamster V79 cells.
Pre-treatment with EMS decreased markedly the survival of cells treated with MMS compared with that of cells treated simultaneously with both chemicals. The insertion of interval time between treatments with both chemicals restored the cell survival to that treated with EMS alone. The pre-treatment with MMS also decreased the survival of cells treated with EMS more markedly than that of cells treated with two chemicals simultaneously.
When cells were pre-treated with EMS, the frequency of 6TG-resistant mutations induced by MMS enhanced to be higher than that of cells treated with both chemicals simultaneously. In this case, the restoration effect of incubation time between treatments with two chemicals was found. On the other hand, pre-treatment with MMS, no detectable change in the frequency of 6TG-resistant mutations induced by EMS was found, compared with that in cells treated with both chemicals simultaneously.
In the induction of OUA-resistant mutations induced by EMS, pre-treatment with MMS increased the mutation frequency compared with that in cells treated with both chemicals simultaneously. Also in the simultaneous treatment with both chemicals, the frequency of QUA-resistant mutations was higher than that of mutations induced by EMS alone. The insertion of interval between two treatments with both chemicals reduced the mutation frequency.

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