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The purpose of this study was to investigate how gravity level affects the excitability of the soleus muscle (SOL) motoneuron pool to Ia afferent input while erect posture is maintained in humans. Three healthy male subjects participated in an experiment whereby three different gravity conditions [microgravity (MG), normal gravity (NG), and hypergravity (HG)] were imposed using a parabolic flight procedure. The SOL H-reflex was evoked every 2 s while the subjects kept an erect posture. The stimulus intensity was controlled automatically on a real-time basis by personal computer to induce the constant amplitude of M-wave (10+/-5% of maximal M-wave amplitude). The background electromyographic activity (BGA) of the SOL was largest during HG, while it was almost absent during MG. The SOL H-reflex amplitude was significantly larger during HG and MG than during NG ( P<0.05). During NG and HG, there was a linear relationship between the BGA and the H-reflex amplitude; the difference in the SOL H-reflex amplitude between both gravity conditions could be explained in terms of the BGA level. However, during MG, despite the absence of BGA, the SOL H-reflex amplitude was larger than that during NG. Furthermore, when the subjects voluntarily activated the SOL by applying a load to the lower limb joints and spine by pulling a handle upward, this H-reflex enhancement almost disappeared. These results suggest that the somatosensory systems detecting a load at the lower limbs and/or vertebral column might play a role in reducing the excitability of the SOL motoneuron pool to Ia afferent inputs by presynaptic inhibition.

Ciguatera fish poisoning (CFP) caused by the consumption of fish that have accumulated ciguatoxins (CTXs) affects more than 50000 people annually. The spread of CFP causes enormous damage to public health, fishery resources, and the economies of tropical and subtropical endemic regions. The difficulty in avoiding CFP arises from the lack of sensitive and reliable analytical methods for the detection and quantification of CTXs in contaminated fish, along with the normal appearance, smell, and taste of fish contaminated with the causative toxins. Thus, an accurate, sensitive, routine, and portable detection method for CTXs is urgently required. We have successfully developed a highly sensitive fluorescent sandwich ELISA, which can detect, differentiate, and quantify four major CTX congeners (CTX1B, CTX3C, 51-hydroxyCTX3C, and 54-deoxyCTX1B) with a detection limit of less than 1 pg/mL. The ELISA protocol, using one microtiter plate coated with two mAbs (10C9 and 3G8), and ALP-linked 8H4, can detect any of the four CTX congeners in a single operation. CTX1B spiked into fish at the FDA guidance level of 0.01 ppb CTX1B equivalent toxicity in fish from Pacific regions was also proven to be reliably detected by this ELISA. Furthermore, the efficiency of extraction/purification procedures and the matrix effect of contaminants in fish were evaluated in detail, since pretreatment and matrix effects are critical for ELISA analysis.

The aim of the present study was to compare risk factors for problematic Internet use (PIU) among Japanese and Chinese university students. A sample of 267 Japanese and 236 Chinese first year university students responded to questionnaires on the severity of PIU, depression, self-image/image of others, and perceived parental child-rearing styles. The results indicated that Japanese participants were more likely to demonstrate PIU than their Chinese counterparts. Compared to Chinese students, Japanese students reported more negative self-image, lower parental care, greater overcontrol, and higher depression scores. The PIU group had a higher depression score compared to the normal Internet use group. Compared with the non-PIU group, the PIU group consisted of more male and Japanese participants. Further, they tended to have more negative self-images, saw their mothers to be less caring, and perceived their mothers and fathers as more overcontrolling. PIU is strongly associated with depression, negative self-image, and parental relations. Finally, mediation analysis revealed that such national differences in PIU between Japanese and Chinese were clarified in depression and perceived mother's care. This cross-national study indicated that depression and perceived mother's care were both significant risk factors that were associated with the national difference in PIU between Japanese and Chinese participants.