Biology subjects

Fujioka, H.

Publications and source records attributed to Fujioka, H..

7 recordsLinked to original sources

bioRxiv2025

Chronic cervical vibration ameliorates depression-like behavior in Wistar-Kyoto rats

Major depressive disorder (MDD) is a highly prevalent psychiatric condition, and a substantial proportion of patients exhibit inadequate responses to conventional pharmacotherapy. Somatosensory processing abnormalities and altered thalamo-cortical connectivity have been implicated in the pathophysiology of MDD, raising the possibility that targeted somatosensory stimulation may modulate affective circuits. Here, we examined whether chronic cervical vibration improves depression-like behaviors in Wistar-Kyoto (WKY) rats, a well-established model of treatment-resistant depression. Rats received repeated vibration stimulation applied to the cervical region. Behavioral effects were evaluated using the novelty-suppressed feeding test (NSFT) and the forced swim test (FST). Swimming activity was quantified during the late-phase of the FST to exclude early panic-like behavior. Immunohistochemistry for c-Fos was performed in the dorsal raphe (DR), lateral habenula (LHb), paraventricular nucleus of the hypothalamus (PVN), and prefrontal cortex (PFC). Vibration-treated rats showed significantly shorter feeding latencies in the NSFT and significantly increased swimming distance during the analysis period of the FST. No significant group differences in c-Fos expression were observed in DR, LHb, PVN, or PFC. These findings indicate that chronic cervical vibration produces reproducible improvements in depressive-like behavior in WKY rats. Because c-Fos activity remained unchanged, the behavioral effects may reflect gradual changes in broader network processing rather than acute activation of monoaminergic or habenular-prefrontal pathways. Cervical vibration represents a simple, non-invasive sensory intervention with translational potential. Additional mechanistic studies are warranted.

neuroscience↗

bioRxiv2022

Ants dynamically adjust liquid foraging strategies in response to biophysical constraints

Ant foragers need to provide food to the rest of the colony, which often requires transport over long distances. Foraging for liquid is especially challenging because it is difficult to transport and share. Many social insects store liquid food inside the crop to transport it to the nest, and then regurgitate this fluid to distribute it to nestmates through a behaviour called trophallaxis. Some ants instead transport fluids with a riskier behaviour called pseudotrophallaxis - holding a drop of liquid between the mandibles through surface tension. Ants can then share this droplet with nestmates without ingestion or regurgitation. Here, we hypothesised that ants optimise their liquid-collection approach depending on viscosity. Working with a ponerine ant that uses both trophallaxis and pseudotrophallaxis, we investigated why each liquid-collection behaviour might be favoured under different conditions by measuring biophysical properties, collection time, and reaction to food quality for typical and viscosity-altered sucrose solutions. We found that ants can collect more liquid food per unit time by mandibular grabbing than by drinking. At high viscosities, which in nature correspond to high sugar concentrations, ants switched their liquid collection method to mandibular grabbing in response to viscosity, and not to sweetness. Our results demonstrate that ants change their transport and sharing methods according to viscosity - a proxy for sugar concentration in nature - increasing the mass of sugar returned to the nest per trip.

animal behavior and cognition↗

bioRxiv2022

Super-resolution vibrational imaging based on photoswitchable Raman probe

Super-resolution vibrational microscopy is a promising tool to increase the degree of multiplexing of nanometer-scale biological imaging, because the spectral linewidth of molecular vibration is about 50 times narrower than that of fluorescence. However, current techniques of super-resolution vibrational microscopy still suffer from various limitations including the need for cell fixation, high power loading or complicated frequency-modulated detection schemes. Herein we utilize photoswitchable stimulated Raman scattering (SRS) to develop a method that we call reversible saturable optical Raman transitions (RESORT) microscopy, which overcomes these limitations. We first describe a new kind of photoswitchable Raman probe designated DAE620 and then we employ a standard SRS detection scheme to validate its signal activation and depletion characteristics when exposed to low-power (microwatt level) continuous-wave laser light. By harnessing the SRS signal depletion of DAE620 through a donut-shaped beam, we demonstrate super-resolution vibrational imaging of mammalian cells with excellent chemical specificity and spatial resolution beyond the optical diffraction limit. Our results indicate RESORT microscopy to be an effective tool with high potential for multiplexed super-resolution imaging of live cells.

bioengineering↗

bioRxiv2021

Near-infrared imaging in fission yeast by genetically encoded biosynthesis of phycocyanobilin

Near-infrared fluorescent protein (iRFP) is a bright and stable fluorescent protein with excitation and emission maxima at 690 nm and 713 nm, respectively. Unlike the other conventional fluorescent proteins such as GFP, iRFP requires biliverdin (BV) as a chromophore because iRFP originates from bacteriophytochrome. Here, we report that phycocyanobilin (PCB) functions as a brighter chromophore for iRFP than BV, and biosynthesis of PCB allows live-cell imaging with iRFP in the fission yeast Schizosaccharomyces pombe. We initially found that fission yeast cells did not produce BV, and therefore did not show any iRFP fluorescence. The brightness of iRFP attached to PCB was higher than that of iRFP attached to BV in vitro and in fission yeast. We introduced SynPCB, a previously reported PCB biosynthesis system, into fission yeast, resulting in the brightest iRFP fluorescence. To make iRFP readily available in fission yeast, we developed an endogenous gene tagging system with iRFP and all-in-one integration plasmids, which contain genes required for the SynPCB system and the iRFP-fused marker proteins. These tools not only enable the easy use of iRFP in fission yeast and the multiplexed live-cell imaging in fission yeast with a broader color palette, but also open the door to new opportunities for near-infrared fluorescence imaging in a wider range of living organisms.

cell biology↗

bioRxiv2020

Individual Ants Do Not Show Active/rest Rhythms in Natural Nest Conditions

Circadian rhythms, which respond to the day/night cycle on the earth, arise from the endogenous timekeeping system within organisms, called the biological clock. For accurate circadian rhythms, endogenous oscillations are synchronized to light and temperature. In social insects, both abiotic and biotic factors (i.e., social interactions) play a significant role in active/rest rhythm regulation. However, it is challenging to monitor individual active-rest rhythms in a colony because of the large group size and small body size. Therefore, it is unclear how social interactions coordinate each individuals active/rest rhythms. This study developed an image-based tracking system using 2D barcodes for Diacamma sp. (a monomorphic ant) and measured the locomotor activities of all colony members under laboratory colony conditions. We also investigated the effect of broods on active/rest rhythms by removing all broods under colony conditions. Active/rest rhythms appeared only in solitary ants, not under colony conditions. In addition, arrhythmic active-rest rhythms were retained after brood removal. Therefore, a mixture of social interactions, not abiotic factors, induces the loss of active/rest rhythms. These results contribute to the knowledge of the diversity pattern of circadian rhythms in social insects.

animal behavior and cognition↗

bioRxiv2020

Bipartite network analysis of task-ant associations reveals task groups and absence of colonial diurnal activity

Social insects are one of the best examples of complex self-organised systems exhibiting task allocation. How task allocation is achieved is the most fascinating question in behavioural ecology and complex systems science. However, it is difficult to comprehensively characterise task allocation patterns due to behavioural complexity, such as the individual variation, context dependency, and chronological variation. Thus, it is imperative to quantify individual behaviours and integrate them into colony levels. Here, we applied bipartite network analyses to characterise individual-behaviour relationships. We recorded the behaviours of all individuals with verified age in ant colonies and analysed the individual-behaviour relationship at the individual, module, and network levels. Bipartite network analysis successfully detected the module structures, illustrating that certain individuals performed a subset of behaviours (i.e., task groups). We confirmed age polyethism by comparing age between modules. Additionally, to test the daily rhythm of the executed tasks, the data were partitioned between daytime and nighttime, and a bipartite network was re-constructed. This analysis supported that there was no daily rhythm in the tasks performed. These findings suggested that bipartite network analyses could untangle complex task allocation patterns and provide insights into understanding the division of labour.

animal behavior and cognition↗

bioRxiv2018

PTBP2-dependent alternative splicing regulates protein transport and mitochondria morphology in post-meiotic germ cells.

The RNA binding protein PTBP2 (polypyrimidine tract binding protein 2) is a key regulator of tissue-specific alternative RNA splicing. In the testis, PTBP2 is expressed in meiotic and post-meiotic germ cells (spermatocytes and spermatids, respectively). In these cells, PTBP2 is required for proper alternative mRNA splicing for over 200 genes, disproportionately affecting genes encoding proteins involved in protein trafficking via transport vesicles. In this study, we used electron microscopy to test the hypothesis that protein trafficking is impaired in the absence of PTBP2, and to further investigate why spermatogenesis abruptly ceases in PTBP2-deficienct spermatids. Ultrastructural analysis shows that protein trafficking in spermatids is aberrant in the absence of PTBP2. Unexpectedly, we also found that mitochondria morphology and number are significantly altered in PTBP2-deficient spermatids, consistent with increased mitochondria fission. Furthermore, we show that genes with key roles in mitochondria dynamics and function are post-transcriptionally regulated by PTBP2 and in different stages of spermatogenesis. Collectively, the data provide ultrastructural evidence that alternative splicing regulation by PTBP2 during spermatogenesis is critical for proper regulation of protein trafficking and mitochondria morphology.

developmental biology↗