In PNAS, Paul Nelson and Joanna Masel present a theoretical result showing that aging in multicellular organisms is inevitable (1). The argument is as simple as it is powerful. Cellular senescence is a well-known consequence of the second law of thermodynamics, due to mutations, epigenetic misregulation, and protein misfolding. Molecular accidents in a cell can happen and they consequently do h...

We presented a cell kill pharmacodynamic model for cell cycle phase-specific antitumor agents as well as that for cell cycle phase-nonspecific agents. The former was based upon assumptions that a cell population could be divided into a drug-sensitive population having sensitive (or specific) cell cycle phase(s) and a drug-resistant population in resistant cell cycle phases. This model revealed ...

The aim of this study is to investigate the effects of cold atmospheric pressure plasma (CAP)-induced radicals on the epidermal growth factor receptor (EGFR), which is overexpressed by oral squamous cell carcinoma, to determine the underlying mechanism of selective killing. CAP-induced highly reactive radicals were observed in both plasma plume and cell culture media. The selective killing effe...

The presence of oxygen in tumours has substantial impact on treatment outcome; relative to anoxic regions, well-oxygenated cells respond better to radiotherapy by a factor 2.5–3. This increased radioresponse is known as the oxygen enhancement ratio. The oxygen effect ismost commonly explained by the oxygen fixation hypothesis, which postulates that radical-inducedDNAdamage can be permanently ‘f...

The presence of oxygen in tumours has substantial impact on treatment outcome; relative to anoxic regions, well-oxygenated cells respond better to radiotherapy by a factor 2.5–3. This increased radioresponse is known as the oxygen enhancement ratio. The oxygen effect ismost commonly explained by the oxygen fixation hypothesis, which postulates that radical-inducedDNAdamage can be permanently ‘f...

A radio assay employing 14C-uridine to measure the intracellular killing of Candida albicans by phagocytes is presented. The principle of this new method is that after killing of Candida albicans by phagocytes RNA synthesis stops and therefore uridine uptake is diminished whilst viable candida in cultures would take up uridine and as a result, high CPM counts can be obtained within 135 min...

Mice bearing transplanted AKR leukemia received daunorubicin either as a single dose or as four equally divided doses (0.2 mg/mouse; four times) with the time interval between the divided doses varying from 12 to 36 hr; survival of leukemia colony-forming cells was then assayed. When daunorubicin was administered in any of the fractionated schedules, the dose-survival curve was exponential with...

Although the nucleoside analogues fludarabine and chlorodeoxyadenosine have become important therapeutic agents in chronic lymphocytic leukemia (CLL), their effectiveness is limited by drug resistance. Because such resistance is likely to result from impaired drug-induced apoptosis, it is clearly important to understand the mechanisms involved in this process. Whereas p53 can contribute to the ...

The effect of various sulfhydryl compounds on the survival of exponentially growing monolayer cultures of Chinese ham ster cells (HA1 ) heated to temperatures of 37-43° was exam ined. Concentrations of cysteamine which were nontoxic or minimally toxic at room temperature or 37° became increas ingly toxic at elevated temperatures, greatly potentiating the killing produced by heat alone in the ...