Cynomolgus monkeys, used as an animal model to predict human pharmacokinetics, occasionally show different oral absorption patterns to humans due to differences in their intestinal metabolism. In this study, we investigated the differences between intestinal hydrolytic activities in cynomolgus monkeys and humans, in particular the catalyzing activities of their carboxylesterase 2 (CES2) isozymes. For this purpose we used both human and monkey microsomes and recombinant enzymes derived from a cell culture system. Monkey intestinal microsomes showed lower hydrolytic activity than human microsomes for several substrates. Interestingly, in contrast to human intestinal hydrolysis, which is not enantioselective, monkey intestine showed preferential R-form hydrolysis of propranolol derivatives. Recombinant CES2 isozymes from both species, mfCES2v3 from monkeys and human hCE2, showed similar metabolic properties to their intestinal microsomes when expressed in HEK293 cells. Recombinant hCE2 and mfCES2v3 showed similar Km values for both enantiomers of all propranolol derivatives tested. However, recombinant mfCES2v3 showed extreme R-enantioselective hydrolysis, and both hCE2 and mfCES2v3 showed lower activity for O-3-methyl-n-butyryl propranolol than for O-n-valeryl and O-2-methyl-n-butyryl propranolol. This lower hydrolytic activity was characterized by lower Vmax values. Docking simulations of the protein-ligand complex demonstrated that the enantioselectivity of mfCES2v3 for propranolol derivatives was possibly caused by the orientation of its active site being deformed by an amino acid change of Leu107 to Gln107 and the insertion of Met309, compared with hCE2. In addition, molecular dynamics simulation indicated the possibility that the interatomic distance between the catalytic triad and the substrate was elongated by a 3-positioned methyl in the propranolol derivatives. Overall, these findings will help us to understand the differences in intestinal hydrolytic activities between cynomolgus monkeys and humans.

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The current study sought to examine differences in physiological responses to comfortable thermal stimuli applied to the soles of the feet during the simultaneous presentation of other sensory stimuli. As relaxing stimuli, underwater movie footage, classical music, light blue illumination, vibration of the trunk, and the odor of grapefruit oil were each presented simultaneously with a thermal stimulus. Electroencephalography of parietal and cerebral blood flow in the prefrontal cortex were measured. An increase in α-wave activity and a decrease in cerebral blood flow were found for all combinations of stimuli compared with baseline. Additionally, the results revealed differences in response speed depending on the stimulus presentation condition. However, the tendency suggesting a difference in response times depending on the stimulus condition was similar to that of the thermal stimulus alone. The results indicated that thermal stimulation has a substantial effect on the feeling of relaxation.

The purpose of this study is to construct the determination method of relaxation level based on fluctuations of physiological indexes. In the first step, we revealed gradual transition of physiological indexes in the Electrocardiogram and Electroencephalogram during enhancing relaxation in the experiments. In that transition, the heart rate decreases at the beginning, then the alpha wave time content increases and then fall at the end, and the HF (High Frequency) component in the heart rate variability continuously increases. According to this result, we found that the relaxation state could be discriminated into four levels by visually observation. In the second step, we attempted to segment the time series of physiological indexes into plural clusters with the double articulation analysis. Through this process, we built the method to determine the seven levels of relaxation associated with the preceding clusters. In the final step, we verified the validity of this method.