Biology subjects

Kikuta, S.

Publications and source records attributed to Kikuta, S..

7 recordsLinked to original sources

bioRxiv2026

Hierarchical neuronal processing in primary somatosensory cortex during action observation

Voluntary movement requires the central nervous system to transform and integrate visual and somatosensory information into coordinated motor outputs. Although mirror-like neuronal activity during both action execution and observation has been extensively described in premotor, motor, and parietal cortices, it remains unknown whether the primary somatosensory cortex (S1) also participates in the action observation network. Here, we recorded single-unit activity from cytoarchitectonically defined areas 3a, 3b, 1, and 2 in macaque S1 while monkeys either executed or observed grasping movements. Approximately one-third of neurons across S1 modulated their firing during action observation, with the proportion of responsive neurons increasing from area 3 to areas 1 and 2, consistent with the hierarchical organization of somatosensory processing. Most action observation neurons showed congruent activity during action execution and observation, suggesting that these responses may reflect top-down motor-related or integrated visuomotor signals and are unlikely to be explained by visual input alone. The higher prevalence of action observation neurons in areas 1 and 2 suggests that action observation-related signals preferentially influence later stages of somatosensory processing, potentially via cortico-cortical interactions with motor and parietal regions.

neuroscience↗

bioRxiv2025

Dynamic and context-dependent modulation of proprioceptive input in primate primary motor cortex

During voluntary movement, somatosensory input is attenuated--sensory gating--which may prevent the CNS from being overwhelmed by predictable afferent feedback not essential for motor control. In the cerebral cortex, sensory gating has been demonstrated in primary (S1) and higher-order sensory areas. The primary motor cortex (M1) is the major cortical output relay to the spinal cord and muscles, and proprioceptive feedback is crucial for shaping motor output, much as in S1. However, whether proprioceptive signals to M1 are attenuated during movement, and if so, why, remains unclear. We recorded somatosensory-evoked potentials (SEPs) in M1 of two monkeys performing a wrist task while electrically stimulating muscle and cutaneous afferents innervating forearm extensors and adjacent skin. Both local field potentials and single-neuron recordings revealed significant suppression of muscle-evoked SEPs during Active movement and Static hold phases, providing direct evidence that proprioceptive input to M1 is generally gated during motor execution, as previously reported for cutaneous input. Yet, amidst this suppression, SEPs in a subset of M1 neurons were preserved during Static hold, especially those evoked by antagonist muscle afferents. Because monkeys had to maintain precise joint angles for stable posture, these results suggest that proprioceptive signals from antagonist muscles--likely reflecting spindle activity in lengthening muscles--escape attenuation to provide information essential for joint angle control. Overall, our findings demonstrate that while proprioceptive input to M1 is broadly suppressed during motor output, specific afferent signals from antagonist muscles are selectively maintained in a context-dependent manner to support posture control.

neuroscience↗

bioRxiv2023

A Sodium-dependent Trehalose Transporter Contributes to Anhydrobiosis in Insect Cell Line, Pv11

Pv11 is the only animal cell culture that, when preconditioned with a high concentration of trehalose, can be preserved in the dry state at room temperature for more than one year while retaining the ability to resume proliferation. This extreme desiccation tolerance is referred to as anhydrobiosis. Here we identified a novel transporter that contributes to the recovery of Pv11 cells from anhydrobiosis. In general, the SLC5 family of secondary active transporters co-transport Na+ and carbohydrates including glucose. Here we identified a novel transporter STRT1 (sodium-ion trehalose transporter 1) belonging to the SLC5 family that is highly expressed in Pv11 cells and transports trehalose with Na+ dependency. This is the first report of an SLC5 family member that transports a naturally occurring disaccharide, such as trehalose. Knockout of the Strt1 gene significantly reduced the viability of Pv11 cells upon rehydration after desiccation. During rehydration, when intracellular trehalose is no longer needed, Strt1-knockout cells released the disaccharide more slowly than the parent cell line. During rehydration, Pv11 cells became roughly spherical due to osmotic pressure changes, but then returned to their original spindle shape after about 30 min. Strt1-knockout cells, however, required about 50 min to adopt their normal morphology. STRT1 probably regulates intracellular osmolality by releasing unwanted intracellular trehalose with Na+, thereby facilitating the recovery of normal cell morphology during rehydration. STRT1 likely improves the viability of dried Pv11 cells by rapidly alleviating the significant physical stresses that arise during rehydration. Significance StatementThis is the first report of an SLC5 family member, STRT1 (sodium ion trehalose transporter 1), with Na+-dependent trehalose transport activity. A Strt1-knockout cell line revealed that STRT1 likely plays an important role during anhydrobiosis in Pv11 cells: it efficiently discharges unwanted trehalose in the presence of Na+ during rehydration of dried Pv11 cells, effectively reducing intracellular osmolality and thereby restoring cell morphology to a normal state.

biochemistry↗

bioRxiv2023

Modulation of somatosensory signal transmission in the primate cuneate nucleus during voluntary hand movement

Successful extraction of tactile and kinematic information is crucial for appropriate motor actions in daily life. To achieve this objective, sensory signals should be effectively regulated during motor actions. This regulation is understood both empirically and conceptually, but it is not well known where and how it is implemented in the central nervous system. Here, we show that, during voluntary movement, sensory signals are already attenuated in the primate cuneate nucleus, an early processing site in the ascending lemniscus pathway. The degree of suppression was comparable with the one reported in the cortex, suggesting that psychological attenuation of somatosensation could be ascribed to the cuneate. The results also revealed that this sensory attenuation was of descending origin, suggesting that cortical sensory prediction signals could regulate cuneate sensory transmission for extracting meaningful, and attenuate unnecessary, signals for movement regulation. This recurrent sensory modulation mechanism between cortical and subcortical areas may generalize to other sensory modalities and cognitive processes.

neuroscience↗

bioRxiv2021

Insulin-dependent maturation of newly generated olfactory sensory neurons after injury

Loss of olfactory sensory neurons (OSNs) after injury to the olfactory epithelium (OE) triggers the generation of OSNs that are incorporated into olfactory circuits to restore olfactory sensory perception. This study addresses how insulin receptor-mediated signaling affects the functional recovery of OSNs after OE injury. Insulin levels were reduced in mice by ablating the pancreatic beta cells via streptozotocin injections. These streptozotocin-induced diabetic and control mice were then intraperitoneally injected with the olfactotoxic drug methimazole to selectively ablate OSNs. The OE of diabetic and control mice regenerated similarly until day 14 after injury. Thereafter, the OE of diabetic mice contained fewer mature and more apoptotic OSNs than control mice. Functionally, diabetic mice showed reduced electro-olfactogram responses and their olfactory bulbs had fewer c-Fos-active cells following odor stimulation, as well as performed worse in an odor-guided task compared to control mice. Insulin administered intranasally during day 8 to 13 after injury was sufficient to rescue recovery of OSNs in diabetic mice compared to control levels, while insulin administration between days 1 - 6 did not. During this critical time window on day 8 - 13 after injury, insulin receptors are highly expressed and intranasal application of insulin receptor antagonist inhibits regeneration. Furthermore, an insulin-enriched environment could facilitate regeneration even in non-diabetic mice. These results indicate that insulin facilitates the regeneration of OSNs after injury and suggest a critical stage during recovery (8 - 13 days after injury) during which the maturation of newly generated OSNs is highly dependent on and promoted by insulin. Significance StatementAlthough insulin receptor signaling is known to influence on cellular processes such as proliferation and apoptosis, it is poorly understood whether the insulin influences the regeneration of olfactory sensory neurons (OSNs) after injury. We compared the maturation processes of new OSNs after the methimazole-induced loss of pre-existing OSNs between diabetic and control mice. The results show that the regeneration of new OSNs depend on sufficient insulin levels during a specific temporal window, when insulin receptor expression is highly upregulated. Furthermore, an insulin-enriched environment via nasal insulin application during the critical period facilitates OSNs regeneration even in non-diabetic mice. The present results have implications for intranasal application of insulin as potential clinical therapeutics to facilitate OSNs regeneration after the injury.

neuroscience↗

bioRxiv2017

A mannitol/sorbitol receptor stimulates dietary intake in Tribolium castaneum

Perception of chemical stimuli by insects aids in accepting or rejecting food. Gustatory receptors (Grs) regulating external signals in chemosensory organs have been found in many insects. Tribolium castaneum, a major pest of stored products, possesses over 200 Gr genes. An expanded repertoire of Gr genes appears to be required for diet recognition in generalist feeders; however, it remains unclear whether T. castaneum recognizes a suite of chemicals common to many products or whether it is attracted to specific chemicals, and whether its Grs are involved in its feeding behavior. It is difficult to determine the food preference of T. castaneum based on its dietary intake due to a lack of appropriate methodology. This study established a novel dietary intake estimation method using gypsum, designated the TribUTE (Tribolium Urges To Eat) assay. T. castaneum adults were fed gypsum block without added organic compounds. Sugar preference was determined by adding sweeteners and measuring the amount of gypsum in the excreta. Mannitol was the strongest attractant of T. castaneum dietary intake; in addition, TcGr20 was responsible for mannitol and sorbitol responses in Xenopus oocyte expression, but did not respond to any other non-volatile compounds tested. The EC50 values of TcGr20 for mannitol and sorbitol were 72.6 mM and 90.6 mM, respectively, suggesting that TcGr20 is a feasible receptor for the recognition of mannitol in lower concentrations. TcGr20 was expressed in the antennae, where the perception of mannitol would occur. We examined whether TcGr20 was involved in mannitol recognition using RNAi and the TribUTE assay. The amounts of excreta in TcGr20 dsRNA-injected adults decreased significantly despite the presence of mannitol, compared to that of the control adults. Taken together, our results suggest that T. castaneum adults recognized mannitol/sorbitol using TcGr20 receptors, thereby facilitating their dietary intake.\n\nAbbreviation

biochemistry↗

bioRxiv2017

Towards Water-Free Biobanks: Long-Term Dry-Preservation At Room Temperature Of Desiccation-Sensitive Enzyme Luciferase In Air-Dried Insect Cells

Desiccation-tolerant cultured cells Pv11 derived from the anhydrobiotic Polypedilum vanderplanki embryo endure complete desiccation because of their ametabolic state and resume their metabolism after rehydration. These features led us to develop a novel dry preservation technology for enzymes as it was still unclear whether Pv11 cells preserved an exogenous enzyme in the dry state. This study shows that Pv11 cells protect an exogenous desiccation-sensitive enzyme, luciferase, preserving the enzymatic activity even after dry storage for 372 days at room temperature. A process including pre-incubation with trehalose, dehydration, storage, and rehydration allowed Pv11 (Pvll-Luc) cells stably expressing luciferase to survive desiccation and still emit luminescence caused by luciferase after rehydration. Luminescence produced by luciferase in Pvll-Luc cells after rehydration did not significantly decrease in presence of a translation inhibitor, showing that the activity did not derive from de novo enzyme synthesis following the resumption of cell metabolism. These findings indicate that the surviving Pv11 cells almost completely protect luciferase during desiccation. Lacking of the preincubation step resulted in the loss of luciferase activity after rehydration. We showed that preincubation with trehalose associated to induction of desiccation-tolerant related genes in Pv11 cells allowed effective in vivo preservation of enzymes in the dry state.

biochemistry↗