Biology subjects

Shimoda, S.

Publications and source records attributed to Shimoda, S..

4 recordsLinked to original sources

bioRxiv2026

Circadian Regulation of Taste Sensitivity in Human and Rat Active Periods

Most organisms exhibit endogenous 24-h rhythms that align physiology and behavior with the time of day; however, whether taste sensitivity oscillates in a circadian manner remains unclear, limiting our understanding of its role in feeding behavior. Here, we show that sensitivity to sweet and bitter tastes exhibits circadian modulation, peaking during the active period: daytime in humans and the dark phase in nocturnal rats. In humans, the rhythmicity of sweet taste was evident in detection but not recognition thresholds, indicating circadian modulation at the level of primary sensory processing rather than higher-order cognitive processes. In rats, increased sensitivity during the dark phase was accompanied by upregulation of taste-related genes in type II taste cells in tongue. These findings provide evidences that circadian regulation of taste sensitivity is conserved across species and appears to operate predominantly at the peripheral level. This mechanism may have evolved to optimize energy intake while minimizing exposure to dietary toxins, potentially contributing to survival and continuing to influence modern eating behavior through circadian-sensory-nutritional interactions.

physiology↗

bioRxiv2023

Assessing climate change risks associated with precipitation at unfavorable times in winter wheat using an improved crop calendar model incorporating vernalization and winter survival

Crop phenology calendars are necessary for designing breeding goals and for developing effective management practices. Winter wheat is a representative biennial, the cultivation schedule of which is constrained by winter climate conditions, particularly the processes of vernalization and winter survival. Here, we present improvements to a rule-based crop phenology model by incorporating these factors so that it can be used to accurately estimate the phenological events of winter wheat from daily meteorological data. We tested the improved model in Hokkaido, the northernmost Japanese island, which is characterized by seasonal snow cover and a wet summer. The results confirmed that implementing these factors contributed to accurate estimates of peak occurrence dates of winter wheat phenological events. Furthermore, we applied the improved model to simulate wheat phenology under 2 K and 4 K warmer scenarios. The results showed a delayed sowing period up to approximately one month and slight advancements in both flowering and harvesting, leading to a shorter growth period. While this shortened period may be largely compensated by a decrease in the snow-covered period, the shifts in the vegetative and reproductive phases may have a significant influence on sink-source balance of wheat. We also assessed the risks of pollination failure and preharvest sprouting, both of which are associated with the timing of precipitation, based on the number of rainy days around flowering, and the incidence of precipitation over two consecutive days around the time of harvesting. Our simulations suggested increased risk of pollination failure and reduced risk of preharvest sprouting, leading to an increase in the probability of crop failure. These findings underscore the importance of implementing adaptive measures to mitigate precipitation-related risk under future climate scenarios. Further, the findings provide valuable insights for winter wheat breeders and agronomists, thereby facilitating crop production adaptation strategies.

plant biology↗

bioRxiv2023

Structure-dependent spontaneous calcium dynamics in cultured neuronal networks on microcontact-printed substrates

Microcontact printing (CP) is widely used in neuroscience research. However, CP yields reduced cell-substrate adhesion compared with directly coating cell adhesion molecules. Here, we demonstrate that the reduced cell-substrate adhesion caused by CP, high seeding density, and the local restriction would separately contribute to more aggregated (neurons closer to each other in separate clusters) neuronal networks. Calcium recordings revealed that more aggregated networks presented fewer spontaneous calcium activity patterns, and were more likely dominated by synchronized network-wide calcium oscillation (network bursts). First, on a uniform microcontact-printed substrate, densely seeded neurons were reaggregated into a Petri dish-wide network consisting of small clusters, of which the calcium dynamics were dominated by network bursts. Next, further analysis revealed this dominance was maintained since its appearance, and the initiation and propagation of bursts in the small-cluster network shared a similar mechanism with that of homogeneous networks. Then, sparsely seeded neurons formed several networks with different aggregation degrees, in which the less clustered ones presented abundant time-varying subnetwork burst patterns. Finally, by printing locally restricted patterns, highly clustered networks formed, where dominant network bursts reappeared. These findings demonstrate the existence of structure-dependent spontaneous calcium dynamics in cultured networks on microcontact-printed substrates, which provide important insights into designing cultured networks by using CP, and into deciphering the onset and evolution of network bursts in developmental nerve systems.

neuroscience↗

bioRxiv2019

Long-term associative memory in rats: effects of familiarization period in object-place-context recognition test

Spontaneous recognition tests, which utilize rodents innate tendency to explore novelty, can evaluate not only simple non-associative recognition memory but also more complex associative memory in animals. In the present study, we investigated whether the length of the object familiarization period (sample phase) improved subsequent novelty discrimination in the spontaneous object, place, and object-place-context (OPC) recognition tests in rats. In the OPC test, rats showed a significant novelty preference only when the familiarization period was 30 min but not when it was 5 min or 15 min. However, the rats exhibited a successful discrimination between the stayed and replaced objects under 15 min and 30 min familiarization period conditions in the place recognition test and between the novel and familiar objects under all conditions of 5, 15 and 30 min in the object recognition test. Our results suggest that the extension of the familiarization period improves performance in the spontaneous recognition paradigms, and a longer familiarization period is necessary for long-term associative recognition memory than for non-associative memory.

animal behavior and cognition↗