Biology subjects

Kuriyama, K.

Publications and source records attributed to Kuriyama, K..

8 recordsLinked to original sources

bioRxiv2026

A Proof-of-Concept Study on Attached Spirulina Cultivation Under Microgravity and Partial Gravity Aboard the ISS

Microalgal attached cultivation circumvents gas-liquid separation issues of liquid-suspended cultivation, yet performance under reduced gravity remains unevaluated. As a proof-of-concept, we evaluated Arthrospira platensis (Spirulina) cultivation under artificial 1G, 1/6G, and microgravity ({micro}G) on the International Space Station. Spirulina expanded without cell detachment, medium floating, or component separation, with relative radial growth rates of 0.28%0.5 day-1 (1G), 0.22%0.5 day-1 (1/6G), and 0.17-0.21%0.5 day-1 ({micro}G), demonstrating feasibility in space.

bioengineering↗

bioRxiv2026

Identification of a microRNA with a mutation in the loop structure in the silkworm Bombyx mori

MicroRNAs (miRNAs) play essential roles in the posttranscriptional regulation of gene expression in organisms. In the process of synthesizing mature miRNAs from miRNA precursors, the miRNA precursors are cleaved via Dicer at their loop structure, after which the miRNA precursors become mature and regulate transcription. However, the consequences of altering the loop sequence are not fully understood. The silkworm Bombyx mori is a lepidopteran insect with many genetic strains. We identified a mutant of the miRNA miR-3260 whose the part of the loop structure was lacking in a silkworm strain with translucent larval skin. Here, we aimed to analyze the role of wild-type miR-3260 and the influence of the mutation of the loop structure in B. mori. First, we identified the genomic region responsible for the translucent larval skin phenotype and determined that the mutated miR-3260 nucleotide sequences. Then, we predicted the binding partners of wild-type miR-3260 using the RNA hybrid tool and found two juvenile hormone (JH)-related genes as targets of wild-type miR-3260. Next, we assessed the relationships between miR-3260 and JH and found that miR-3260 was highly expressed in the Corpora allata and its expression responded to JH treatment. Meanwhile, miR-3260 mimic and inhibitor did not induce the typical phenotypes associated with JH in B. mori. Then, we compared the dicing products from wild-type and mutant miR-3260 precursors and observed that neither form underwent Dicer-mediated cleavage when the loop structure was altered. These results suggest that loop mutations in the miR-3260 precursor may not influence dicing activity, consistent with the lack of observable phenotypic effects.

molecular biology↗

bioRxiv2025

Luteal-phase resistance training enhances nocturnal heat dissipation and delta power during sleep

Study ObjectivesThis study examined the effects of resistance training on sleep architecture, physiological heat dissipation, and {delta} power in young adult women during the follicular and luteal phases of the menstrual cycle. MethodsNine healthy young women participated in a four-condition crossover protocol comprising (1) follicular phase non-exercise, (2) follicular phase exercise, (3) luteal phase non-exercise, and (4) luteal phase exercise. The exercise condition consisted of 30 minutes of resistance training at 70% of one-repetition maximum performed during the day. During each night, electroencephalography, body temperature, and core body temperature were measured in the home environment. The distal-proximal body temperature gradient (DPG), which is a validated indicator of heat dissipation, was calculated ResultsResistance training enhanced heat dissipation, as reflected by increased DPG values, and increased the proportion of stage N3 sleep during both menstrual cycle phases, with more pronounced effects during the luteal phase. Sleep from bedtime to wake time was divided into four equal segments. Under the luteal phase with exercise, the appearance of stage N3, {delta} power, and the DPG were elevated in the mid-to-late segments of sleep. ConclusionsThese findings suggest that daytime resistance training promotes nocturnal deep sleep and facilitates thermoregulatory heat loss, as indicated by an increased DPG, particularly during the luteal phase when thermoregulation is less stable than the follicular phase. This training may represent a practical intervention to improve sleep quality and physiological recovery in women across different phases of the menstrual cycle. STATEMENT OF SIGNIFICANCEWomen often experience sleep disturbances during the luteal phase of the menstrual cycle, but the physiological mechanisms and effective interventions remain unclear. This study shows that daytime resistance training enhances nighttime heat dissipation and increases slow-wave sleep during this phase. These findings suggest that exercise is a practical approach to alleviate menstrual cycle-related sleep issues. By clarifying how exercise interacts with thermoregulation and sleep across the cycle, this work contributes to understanding female-specific sleep physiology and supports the development of non-pharmacological strategies to improve womens sleep health in women. Future research should examine the long-term effects of daytime resistance training and compare different exercise modalities across diverse populations.

neuroscience↗

bioRxiv2025

Light stimulation system for measuring pupillary light responses based on Maxwellian view optical system using a retina presentation type viewfinder

BackgroundMelanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGC) contribute predominantly to non-image-forming effects of light, such as light-induced circadian phase shift, melatonin suppression, and pupillary light reflex. Post-illumination pupil response (PIPR) has been well-used for the evaluation of ipRGC sensitivity for humans since it is able to detect ipRGC function independently from conventional cones. However, pharmacological mydriasis or a specialized light stimulation system, such as the Maxwellian view (MV) optical system, is required to avoid dynamic pupil constriction in the stimulated eye for effective PIPR measurements, which makes these approaches less practical and difficult to implement in standard experimental settings. In this context, we propose the application of a retinal projection viewfinder based on the MV system as a practical approach for measuring PIPR, and evaluate the feasibility of this approach by comparing its performance with a typical LED-based optical system. MethodsTwenty-two healthy participants underwent pupillometry using both the MV-based viewfinder and a typical LED-based system. Monochromatic red and blue light stimuli were presented for durations of 1 and 10 seconds. Pupil responses, including maximum constriction, PIPR amplitude after 6 seconds from the light offset, area under the curve (AUC) values of PIPR, and sustained slopes, were analyzed using a linear mixed-effects model to assess the differences between the two systems. ResultsThe MV-based viewfinder significantly enhanced net PIPR amplitude (p < 0.05) and sustained slope (p < 0.01) during 10-second light stimulation compared to the LED system, demonstrating its capability to effectively measure ipRGC-driven responses. In contrast, no significant differences were observed in the net AUC values. These results highlight that the MV-based viewfinder enables effective PIPR measurements by delivering constant and controlled light stimulation directly to the retina, minimizing the effects of dynamic pupil constriction during light stimulation. ConclusionsThe MV-based viewfinder showed feasibility as an effective method for measuring PIPR without requiring pharmacological dilation or complex optical instrumentation. This approach has strong potential for advancing the assessment of human ipRGC function using pupillary responses.

neuroscience↗

bioRxiv2024

Leg stiffness adjustment during hopping by dynamic interaction between the muscle and tendon of the triceps surae

The biomechanics underlying bouncing exercises are characterized by the spring-like behavior of the human leg. However, the mechanism underlying the mechanistic contribution of muscle dynamics to the adjustment of leg stiffness is unclear. This study aimed to elucidate the mechanisms governing the changes in leg stiffness during hopping at different frequencies by examining the dynamics of the muscle-tendon complex (MTC) of the medial gastrocnemius muscle (MG). We hypothesized that an increase in muscle stiffness would augment leg stiffness, thereby enabling hopping at higher frequencies. Kinematic and kinetic data were obtained using a motion capture system and force plates. Simultaneously, ultrasound images of the MG were acquired to quantify the muscle fascicle length and pennation angle. The results showed that the stiffness of the MTC increased with hop frequency and exhibited a strong correlation with the leg stiffness. In addition, with increasing frequency, the fascicle contractions shifted from isometric to concentric. To explain these results, an MTC model comprising a contractile component (CC) and series elastic component (SEC) was constructed. We observed a negative CC stiffness, which increased the MTC stiffness. Although this result appears to diverge from our initial hypothesis, the effect of negative CC stiffness on MTC stiffness can be understood, from the perspective of two springs in series, as an extension of the very high stiffness effect. This quantitative understanding of the dynamic interaction between the muscle and tendon offers a unified framework for interpreting various results of previous studies on fascicle dynamics during hopping.

bioengineering↗

bioRxiv2023

Bidirectional feedforward regulatory loop of Dicer-like 4 and flavonoids causes floral bicolor patterning in petunia and dahlia

Floral bicolor pigmentation is caused by naturally occurring RNA interference (RNAi) in some cultivars of petunia and dahlia. In both plants, the chalcone synthase gene is highly expressed only in the pigmented region of bicolor petals. However, it remains unknown why RNAi is induced only in the unpigmented region. To elucidate the mechanism of this clear bicolor pattern formation, we examined the dicing activity of Dicer-like 4 (DCL4), which produces small interfering RNAs essential for the induction of RNAi. We showed that the crude extract in the pigmented petal region inhibits dicing activity of DCL4, but not when flavonoids were depleted from the extract. Moreover, we showed the inhibitory activity was associated with flavonoid aglycons. The in vivo dicing activities were detected in the intact protoplasts prepared from the unpigmented region but not from the pigmented region. These results suggest that in the unpigmented region, flavonoids that inhibit DCL4 are not synthesized, and RNAi is maintained, whereas in the pigmented region, DCL4 is inhibited by flavonoids, RNAi is not induced, and anthocyanin biosynthesis is maintained, which ensures RNAi inhibition. Therefore, a clear bicolor pattern is generated by the bidirectional feedforward mechanism of antagonizing DCL4 and flavonoids.

plant biology↗

bioRxiv2023

Conserved cysteine residues in Kaposis sarcoma herpesvirus ORF34 are necessary for viral production and viral pre-initiation complex formation.

Kaposis sarcoma herpesvirus (KSHV) ORF34 plays a significant role as a component of the viral pre-initiation complex (vPIC), which is indispensable for late gene expression across beta and gamma herpesviruses. Although the key role of ORF34 within the vPIC and its function as a hub protein have been recognized, further clarification regarding its specific contribution to vPIC functionality and interactions with other components is required. This study employed a deep-learning algorithm-assisted structural model of ORF34, revealing highly conserved amino acid residues across human beta- and gamma-herpesviruses localized in structured domains. Thus, we engineered ORF34 alanine-scanning mutants by substituting conserved residues with alanine. These mutants were evaluated for their ability to interact with other vPIC factors and restore viral production in cells harboring the ORF34-deficient KSHV-BAC. Our experimental results highlight the crucial role of the 4 cysteine residues conserved in ORF34: a tetrahedral arrangement consisting of a pair of C-Xn-C consensus motifs. This suggests the potential incorporation of metal cations in interacting with ORF24 and ORF66 vPIC components, facilitating late gene transcription, and promoting overall virus production by capturing metal cations. In summary, our findings underline the essential role of conserved cysteines in KSHV ORF34 for effective vPIC assembly and viral replication, thereby enhancing our understanding of the complex interplay between the vPIC components. IMPORTANCEThe initiation of late gene transcription is universally conserved across the gamma- and beta-herpesvirus families. This process employs a viral pre-initiation complex (vPIC), which is analogous to a cellular PIC. Although KSHV ORF34 is a critical factor for viral replication and is a component of the vPIC, the specifics of vPIC formation and the essential domains crucial for its function remain unclear. Structural predictions suggest that the 4 conserved cysteines (C170, C175, C256, and C259) form a tetrahedron that coordinates the metal cation. We further investigated the role of these conserved amino acids in interactions with other vPIC components, late gene expression, and virus production, to demonstrate for the first time that these cysteines are pivotal for these functions. This discovery not only deepens our comprehensive understanding of ORF34 and vPIC dynamics but also lays the groundwork for more detailed studies on herpesvirus replication mechanisms in future research.

microbiology↗

bioRxiv2019

Kaposi’s sarcoma-associated herpesvirus ORF66 is essential for late gene expression and virus production via interaction with ORF34

Kaposis sarcoma-associated herpesvirus (KSHV) is closely associated with B-cell and endothelial cell malignancies. After the initial infection, KSHV retains its viral genome in the nucleus of the host cell and establishes a lifelong latency. During lytic infection, KSHV encoded lytic-related proteins are expressed in a sequential manner and are classified as immediate early, early, and late gene transcripts. The transcriptional initiation of KSHV late genes is thought to require the complex formation of the virus specific pre-initiation complex (vPIC), which may consist of at least 6 transcription factors (ORF18, 24, 30, 31, 34, and 66). However, the functional role of ORF66 in vPIC during KSHV replication remains largely unclear. Here, we generated ORF66-deficient KSHV using a BAC system to evaluate its role during viral replication. While ORF66-deficient KSHV demonstrated mainly attenuated late gene expression and decreased viral production, viral DNA replication was unaffected. CHIP analysis showed that ORF66 bound to the promoters of late gene (K8.1), but did not to those of latent gene (ORF72), immediate early gene (ORF16) and early gene (ORF46/47). Furthermore, we found that three highly conserved C-X-X-C sequences and a conserved leucine-repeat in the C-terminal region of ORF66 were essential for interaction with ORF34 and viral production. The interaction between ORF66 and ORF34 occurred in a zinc-dependent manner. Our data support a model, in which ORF66 serves as a critical vPIC component to promote late viral gene expression and viral production.\n\nIMPORTANCEKSHV ORF66, a late gene product, and vPIC are thought to contribute significantly to late gene expression during the lytic replication. However, the physiological importance of ORF66 in terms of viral replication and vPIC formation remains poorly understood. Therfore, we generated a ORF66-deficient BAC clone and evaluated its viral replication. Results showed that ORF66 played a critical role in virus production and the transcription of L genes. To our knowledge, this is the first report showing ORF66 function in virus replication using ORF66-deficient KSHV. We also clarified that ORF66 interacted with the transcription start site of K8.1 gene, a late gene. Furthermore, we identified the ORF34-binding motifs in the ORF66 C-terminus: three C-X-X-C sequences and a leucine-repeat sequence, which are highly conserved among {beta}- and {gamma}-herpesviruses. Our study provides insights into the regulatory mechanisms of not only the late gene expression of KSHV but also those of other herpesviruses.

microbiology↗