Kazumitsu Hanai

Transforming growth factor-beta activated during exercise in brain depresses spontaneous motor activity of animals. Relevance to central fatigue

Intracerebroventricular administration into sedentary mice of the high molecular mass fraction of cerebrospinal fluid (CSF) from exercise-exhausted rats produced a decrease in spontaneous motor activity [K. Inoue, H. Yamazaki, Y. Manabe, C. Fukuda, T. Fushiki, Release of a substance that suppresses spontaneous motor activity in the brain by physical exercise, Physiol. Behav. 64 (1998) 185-190]. CSF from sedentary rats had no such effect. This suggests the presence of a substance regulating the urge for motion as a response to fatigue. A bioassay system using hydra, a freshwater coelenterate, showed an activity indistinguishable from transforming growth factor-beta (TGF-beta) in the CSF from exercise-fatigued rats, while not in that from sedentary rats. The increase in the concentration of active TGF-beta in the CSF from exercise-fatigued rat was also ascertained by another bioassay system using mink lung epithelial cells (Mv1Lu). Injection of TGF-beta into the brains of sedentary mice elicited a similar decrease in spontaneous motor activity in a dose-dependent manner. Increasing the exercise load on rats raised both the levels of active TGF-beta and the activity of depression on spontaneous motor activity of mice in the CSF of rats. Taken together, these results suggest that exercise increases active TGF-beta in the brain and it creates the feeling of fatigue and thus suppresses spontaneous motor activity.

Hydra biological detection of biologically active peptides in rat cerebrospinal fluid

The Hydra bioassay system utilizes a tentacle ball formation (TBF), a component of the feeding response of hydra, elicited by S-methyl-glutathione. TBF is modulated by many biologically active peptides in a specific way to individual peptides, and is useful in investigating biologically active peptides in a complex biological sample. We applied the hydra bioassay to explore a possible biologically active substance responsible for the decrease in the motor activity of the mice. The suppression of the CSF obtained from rats after exhaustive exercise was marked lower than that of sedentary rats. Addition of transforming growth factor-beta (TGF-beta), which is the only substance known to nullify TBF, to CSF of the sedentary rat reproduced this change in the suppression of the TBF. This system is useful to screen active peptides in small amounts of biological samples containing very low concentrations of peptides.

New index based on the physical separation of motion into three categories for characterizing the effect of cocaine in mice.

Characterization of open-field behavior and locomotor activity is widely used to assess the influence of a drug on mouse or rat behavior. In this study, we developed an index for characterizing the behavior of cocaine-administered mice (C57BL/6, DBA/2, and BALB/c). Because a three-exponential-model exhibited the best fit to the obtained data among the different probability density functions, we divided each walking episode into three categories according to the duration of movement. We found a significant difference in decay variation of mean speed with time in the case of long walking duration. To clarify this difference quantitatively, we developed an index for the changes in locomotion control, based on a heuristic argument regarding the ratio of the coefficients of the drag term obtained by the biphasic motion-equation model. The index had a significant dose-related effect in each strain and a significant strain effect in high-concentration drug. Therefore, it would thus be useful for examining the effect of the drug on locomotor activity in mice. Moreover, evaluating other characters suggested previously, the proposed index had good advantage to differentiate the dose-related response in the three species of inbred mice.

In Situ Potentiation of the Glutathione-binding Protein for the Tentacle Ball Formation by a Protease and Efficient Ingestion of Prey in Hydra

Within minutes, brief treatment with trypsin potentiated tentacle ball formation in Hydra japonica, a new behavioral response to reduced glutathione. With the potentiation of this behavioral response, new glutathione-binding proteins were immediately detected after the trypsin treatment of live Hydra, indicating that trypsin activated the glutathione-binding protein in situ. Fixed brine shrimp (Artemia francisca) were more efficiently ingested in the presence of trypsin and S-methylglutathione (GSM) than in the presence of GSM alone, suggesting a biological role of this behavioral potentiation by trypsin in the feeding chain of Hydra. Ingestion of live A. francisca was significantly reduced in the presence of soybean trypsin inhibitor, suggesting that a protease, possibly released from the wounded prey, plays a role in the feeding in vivo. As for Hydra swallowing its captured prey, a small hydra head piece was isolated and measured as it crept along a thin nylon line; advancement of the head was the same in the presence of both GSM alone, and in that of GSM and trypsin together. Together, these results indicate that the chemoreceptor potentiated in situ by a trypsin-like protease specifically evokes tentacle ball formation resulting in an efficient transfer of prey on the tentacle to the mouth.