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In today's Japan, many individuals live in what is known as a stress society, where daily stress has become a common occurrence. The causes of stress vary from person to person and may be attributed to factors such as social environment and human relationships. Excessive stress can result in oxidative stress, which can have significant impact on both the mind and body. In fact, severe stress can lead not only to sleep disorders such as insomnia but also to mental illnesses such as depression. Theanine, a component derived from glutamic acid and ethylamine found in the roots of tea plants, is present in green tea and contributes to its umami taste. It has been approved as a functional food for stress and sleep. Theanine is known for its relaxing effects and its ability to improve sleep quality. Studies have also indicated its effectiveness in treating mental illnesses such as schizophrenia and depression. By understanding the functionality of theanine and investigating tea-based beverages that can be ingested most efficiently, it is believed that we can contribute to the prevention of diseases associated with reactive oxygen species generated by stress. In this study, we first evaluated the antioxidant effects of theanine using electron spin resonance (ESR) equipment. Next, we measured the amount of theanine in tea beverages using a liquid chromatograph/fluorescence detector (LC/FL). The ESR results demonstrated that theanine exhibits antioxidant activity by inhibiting the generation of reactive oxygen species through copper ions. Moreover, we found that Camellia sinensis, represented by green tea and black tea, contains a significant amount of theanine. [ABSTRACT FROM AUTHOR]

We report a novel method for determination of glass transition temperatures that applies the phenomenon of microwave power saturation in electron spin resonance (ESR). Amorphous polystyrene (PS) and semi-crystalline polyethylene (PE) were used as samples for the measurement. In order to evaluate the glass transition temperature (Tg) at the specific sites in the polymers, we spin-labeled the end or inner segments in PS and inner segments in PE with paramagnetic species. When the microwave power is small enough, the intensity of ESR spectrum is proportional to the square root of the magnitude of the microwave power. However, the intensity of the spectrum no longer increases when an excess power is applied. This is the power saturation phenomenon which is influenced by the relaxation time of the molecular mobility around the spin labels. No significant difference in Tg of PS between end and inner segments was revealed by the ESR microwave power saturation method. This can be explained by in terms of cooperation in the segmental motion at the Tg. As for PE, it was found that Tg in the amorphous region of PE depended on the crystallinity. [ABSTRACT FROM AUTHOR]

Effects of vulcanization parameters on the mechanical fatigue of vulcanized rubber were evaluated from Electron Spin Resonance (ESR) results and stress-strain behavior of the vulcanized polyisoprene. It was found from ESR absorption curves that carbon radicals produced by the breakdown of polymer backbone with the g-value of 2.004 were present. The g-value of sulfur radicals in the vulcanized samples by sulfur was depends on the chemical structure of the vulcanization accelerator. The g-values were 2.004 and 2.014 for the N-cyclohexyl-2-benzothiazol-sulfenamide (CZ) and Tetramethyl thiuram disuffide (TMTD), respectively. For the samples vulcanized by sulfur and CZ, the radical concentration calculated from absorption curves with the g-value of 2.004 increased with the increase of mechanical energy applied to the samples by stretching of the samples. The concentration was larger for the samples in which sulfur-carbon linkages were present than for the samples with sulfur-sulfur linkages, and the smallest for samples vulcanized by peroxide. These results are discussed in relation to the mechanical fatigue of vulcanized rubber. [ABSTRACT FROM AUTHOR]

Hypoxia has been known to be a feature associated with tumor radioresistance. So far, clinical strategies to overcome chronic hypoxia due to the limitation of the oxygen diffusion have been designed. However, intermittent or acute/cycling hypoxia, whose frequency can range between a few cycles per minutes to hours, is receiving increased attention, because this type of hypoxia has been reported to have an influence on tumor malignancy as well as treatment resistance via increased expression of pro-survival pathways. Therefore, a priori information on fluctuating hypoxia can be important in clinical treatment planning, but complicated dynamics makes it difficult to elucidate biological significance of intermittent hypoxia.Here, we illustrate the use of pulsed electron spin resonance imaging (ESRI) as a novel imaging method to directly monitor fluctuating oxygenation i.e. cycling hypoxia in transplanted tumors. A common resonator platform for both ESRI and magnetic resonance imaging (MRI) provided pO 2 maps with anatomical guidance without positional movement. Oxygen images every 3 min in pO 2 could visualize the rapid oxygen fluctuation and distinguish the cycling hypoxia and chronic hypoxia. Furthermore, we have examined the vascular renormalization process by longitudinally pO 2 mapping during treatments with a multi-tyrosine kinase inhibitor sunitinib. Transient improvement in tumor oxygenation and the decrease of cycling tumor hypoxia were visualized by ESRI 2 to 4 days following antiangiogenic treatments. Radiation treatment during this time period of improved oxygenation by antiangiogenic therapy resulted in a synergistic delay in tumor growth.In conclusion, this ESRI technique combined with MRI, may offer a powerful clinical tool to noninvasively detect variable hypoxic status in tumors and to identify a window of vascular renormalization to maximize the effects of combination therapy with antiangiogenic drugs.