Seasonality in mood and behaviours of Japanese residents in high-latitude regions: transnational cross-sectional study

Background

Daylight hours in high-latitude regions tend to be longer than those in Japan in summer, and shorter than those in Japan in winter. For example, daylight hours in London in winter are one-third those of Tokyo. Therefore, this study investigated and compared seasonal changes in mood and behaviours of Japanese individuals living in and outside Japan.

Methods

Surveys were conducted with Japanese residents in summer and winter in the UK (n?=?106), Nordic countries (n?=?40), Southeast Asia (n?=?50), and Japan (n?=?96). First, summer and winter General Health Questionnaire–28 (GHQ28) scores of each regional group were analysed. Subsequently, month-wise differences in mood and behaviours were compared across the four geographical regions.

Results

Summer and winter GHQ28 scores of participants living in the UK and Nordic countries differed significantly, while no seasonal differences were observed for residents in Japan and Southeast Asia. Further, in the UK and Nordic countries, summer was associated with better mood and more activity, while winter was linked to lowered mood and reduced activity.

Conclusion

The results indicate that Japanese living in the UK and Nordic countries (high-latitude regions) experience seasonal fluctuations in depressive symptoms that may be linked to drastic seasonal environmental changes. Observed over a 12-month period, their mood and behaviour declined in winter and improved in summer. Therefore, considering the prevalence of overseas stressors that differ from those in their home country, it is necessary to investigate the effectiveness of support systems that help migrants adapt to seasonal changes in high-latitude regions.

     

Foetal distribution of inhaled mercury vapor in normal and acatalasaemic mice

Levels of mercury distribution in placenta, amniotic sac and foetus and those in brain and liver of maternal acatasaemic mice were higher than those of normal, respectively. The levels of mercury distribution in the blood and lungs of maternal acatalasaemic mice exposed to metallic mercury vapor were also lower than those of normal. Mercury concentrations in placenta and foetus of acatalasaemic mice following exposure to metallic mercury vapor were higher than those of normal. Maternal acatalasaemic mice had decreased levels of mercury in the blood than those of normal mice. Thus, the placenta/blood or foetus/blood ratio of mercury concentration in acatalasaemic mice was significantly higher than that in normal mice. Similarly the brain/blood or liver/blood ratio of maternal acatalasaemic mice was higher than that of normal mice. These results suggest that metallic mercury in the blood readily passed through the blood-brain, blood-foetus barriers. In contrast to the results on exposures of mice to metallic mercury, the foetus/maternal blood ratio of mercuric concentration in the acatalasaemic mice following injection of mercuric chloride was similar to that in the normal mice. Moreover, the foetus/maternal blood ratio of mercury concentration in acatalasaemic or normal mice injected with mercuric chloride was lower than those in acatalasaemic or normal mice exposed to metallic mercury.     

Investigation of the heterogeneity of heterogalactan from the fruit bodies of Fomitopsis pinicola, by employing concanavalin A-Sepharose affinity chromatography

A heterogalactan was isolated from the hot water extract of fruit bodies of Fomitopsis pinicola by a combination of fractionation procedures including precipitation with ethanol and with Cetavlon, and chromatography on columns of DEAE-cellulose and Sephadex G-100. Despite its apparent homogeneity on gel filtration, zone electrophoresis, sedimentation equilibration, and immunodiffusion analyses, the neutral component of heterogalactan was further fractionated into unbound, weakly bound, and strongly bound forms by affinity chromatography on a column of concanavalin A-Sepharose CL 4B. The former two polysaccharides fractions eluted with 0.1 M phosphate buffer (pH 7.0) were found to be a fucogalactan and a mannofucogalactan, respectively. A more tightly bound fraction (mannofucogalactan) was subsequently eluted with 0.1 M glucose in 1 M NaCl. The results of methylation, complete Smith degradation, and proton and 13C NMR spectroscopic analyses indicated that the three kinds of heterogalactans are all highly branched polysaccharides containing a framework of (1 leads to 6)-linked alpha-D-galactopyranosyl residues, the C-2 positions of which are substituted in different proportions with either single L-fucopyranosyl residues or disaccharide units of 3-O-alpha-D-mannopyranosyl-L-fucopyranose residues.     

Extraadrenal expression of steroid 21-hydroxylase and 11β-hydroxylase by a benign testicular leydig cell tumor

We present an unusual case with bilateral testicular Leydig cell tumors displaying extraadrenal expression of steroid 21-hydroxylase and 11β-hydroxylase. Histological examination of a 38-yr-old man infertile due to azoospermia showed him to have bilateral testicular Leydig cell tumors. The in vitro steroidogenic potential of the tumors and their adjacent testicular tissue was evaluated using organ culture. Tumor tissue was found to secrete deoxycorticosterone (DOC), corticosterone (B) and cortisol, which are not produced in normal adult testis, into the medium, while testicular tissue adjacent to the tumors secreted a small amount of DOC and B. Northern blot analysis with cytochrome P-450_C21 complementary DNA (cDNA) and P-450_11β cDNA as probes revealed that the tumor contained a considerable amount of mRNA for P-450_C21 and P-450_11β, while the mRNAs were not detected in the testicular tissues adjacent to the tumors. It is suggested that the high local levels of estrogen and/or progesterone within the Leydig cell tumors and their adjacent testicular tissues induced extraadrenal expression of steroid 21-hydroxylase and 11β-hydroxylase by the tumors and their adjacent testicular tissues.     

How the scrub height of dwarf pine Pinus pumila decreases at the treeline

Plant height decreases much within narrow altitudinal spans near treelines. We compared the stem age, stem inclination and shoot elongation rates of alpine dwarf pine Pinus pumila between the upper distribution limit (treeline, 2,850 m a.s.l.) and the lower distribution limit (2,500 m a.s.l.) on Mount Norikura in central Japan, to examine how the growth traits of P. pumila change with altitude. The mean stem height at the upper distribution limit (49 cm) was about a quarter of that at the lower distribution limit (187 cm). The mean ratio of stem height to length was lower at the upper distribution limit than at the lower distribution limit, indicating that P. pumila stems inclined more at the higher altitude. The mean stem age at the upper distribution limit (48 years) was less than a half of that at the lower distribution limit (109 years). Although the shoot elongation rate positively correlated with stem length at the two altitudes, the shoot elongation rate at a given stem length was lower at the upper distribution limit than at the lower distribution limit. Thus, less developed scrub at the upper distribution limit than at the lower distribution limit was due to shorter stem age, more creeping stems and lower shoot elongation rates. Generally, wind velocity is greater in higher altitudes. Probably, strong wind reduces the growth and mean stem age of P. pumila stems at the upper distribution limit. Therefore, this study concludes that the scrub height of P. pumila is controlled not only by temperature, but also by strong wind.     

Ranging patterns of Japanese macaques in the coniferous forest of Yakushima: Home range shift and travel rate

Ranging is one of the most important behavioral adaptations for coping with seasonally fluctuating food and thermal conditions. We studied the ranging patterns, in particular home range shift and travel rate of Japanese macaques (Macaca fuscata) in the coniferous forest of Yakushima by tracking a group for 17 months. We also supplemented our data with records collected every August over a 5-year annual census. The macaque group used the eastern part of their home range from May to September and the western part during the rest of the year. The eastern part of the home range was largely primary forest in the national park, and the altitude was higher than in the western part. When they used the western part, the macaques ate more herbs and fruits from small-sized trees, the availability of which was higher in the logged forest. This east–west home range shift occurred repeatedly over multiple years. A neighboring group occupied the western part of the focal group's home range in summer, which the focal group did not use in that season. Both temperature and diet affected seasonal changes in the monthly average travel rate. Animals need more energy for thermoregulation when the temperature is low, so the macaques decreased their ranging efforts to save energy at times of low temperature. They increased their ranging distance to eat fungi, since their encounters with this food would increase with the total distance walked. They also increased their travel rate when eating flowers, which had lower food patch (tree) density than other foods such as fruits. The data supported the hypothesis that the macaques capitalize on habitat heterogeneity in a seasonally fluctuating habitat by shifting their home range and modifying their travel rate.     

Coumarin and Euponin,Two Inhibitors for Insect Development from Leaves of Eupatorium japonicum

An ovicide and a larval growth inhibitor against Drosophila melanogaster were isolated from leaves of Eupatorium japonicum. The ovicide was identified as coumarin. The structure of the larval growth inhibitor, a new naturally occurring guaianolide named euponin, was elucidated on the basis of spectral and chemical evidence. The inhibitory effects of these agents on the egg and larva were also described.