Biology subjects

Kitagawa, N.

Publications and source records attributed to Kitagawa, N..

3 recordsLinked to original sources

bioRxiv2025

Dual resistance to cold and ethanol in Penicillium species persistently contaminating donated cadavers

Modern cadaver preservation techniques, such as low-concentration formaldehyde methods, are increasingly adopted to mitigate health risks and improve tissue fidelity for medical education and surgical training. However, these environments potentially foster fungal contamination. This study aimed to identify contaminating species from cadaveric surfaces stored under specific preservation conditions and establish effective countermeasures. Genetic identification revealed Penicillium paneum as the predominant species, while Penicillium corylophilum was also detected. These species exhibited distinctive traits, including vigorous growth at 4{degrees}C and marked ethanol tolerance, that explain their persistence in this preservation environment. Antifungal susceptibility testing demonstrated that these isolates were highly susceptible to commonly used disinfectants such as benzalkonium chloride, chlorhexidine gluconate, and phenol. Our findings indicate that these Penicillium species are uniquely adapted to low-temperature and ethanol-rich preservation environments. The incorporation of the identified disinfectants into preservation solutions offers a practical and effective strategy for controlling persistent fungal contamination in cadaveric facilities.

microbiology↗

bioRxiv2025

Excessive chondrogenesis in the blastema initiates during hypomorphic limb regeneration in Xenopus froglet, but not during patterned limb regeneration in Xenopus tadpoles and newts

Xenopus laevis tadpoles and newts regenerate a limb almost completely after amputation, with recapitulation of the patten formation of the limb. Metamorphosed Xenopus froglets form a cone-shaped regenerating blastema, similar to tadpoles and newts, but ultimately regenerate only a hypomorphic cartilaginous spike. Previous study suggested that excessive chondrogenesis, distinct from Xenopus tadpoles, may occur in the regenerating limb of a froglet and may prevent pattern formation during regeneration. However, it remains unclear whether excessive chondrogenesis actually occurs in froglet blastemas. If it does, when does it initiate and how does it progress in the blastemas? To answer these questions, we examined the extent of chondrogenesis in regenerating blastemas which have the common morphological shapes observed in newts (Pleurodeles waltl), Xenopus laevis tadpoles, and froglets. To evaluate excessive chondrogenesis, we developed a simplified procedure using immunofluorescence for cartilage markers (Sox9 or Col2a1) and quantitative image analysis. Our analysis revealed that signs of excessive chondrogenesis were detected not in newts and tadpoles but in froglets blastemas. During limb regeneration in froglets, the first sign of excessive chondrogenesis was detected in the cone-shaped blastema at the medium bud (MB) stage, and excessive chondrogenesis progressed to a more severe state as the blastema grew. These results indicate that excessive chondrogenesis initiates specifically in froglet blastemas at the MB stage at the latest and progresses in a definite spatio-temporal manner. Further elucidation of the mechanisms underlying froglet-specific excessive chondrogenesis in the blastema may lead to the recovery of patterned limb regeneration in froglets with adequate inhibition of chondrogenesis.

developmental biology↗

bioRxiv2023

Time-dependent neural arbitration between cue associative and episodic fear memories

After traumatic events, simple cue-threat associative memories strengthen while episodic memories become fragmented. However, how the brain prioritizes cue associations over episodic coding of traumatic events remains unclear. Here, we developed a new episodic threat conditioning paradigm in which participants concurrently form two memory representations: cue associations and episodic cue sequence. We discovered that these two distinct memories compete for physiological fear expression, reorganizing overnight from an overgeneralized cue-based to a precise sequence-based expression. With multivariate fMRI, we track inter-area communication of the memory representations and demonstrate that a shift from hippocampal-dominant to prefrontal-dominant control of the fear regulatory circuit governs this memory maturation. Critically, this overnight reorganization is altered in individuals with heightened trait anxiety. Together, these findings suggest the brain prioritizes generalizable associative memories under recent traumatic stress, but resorts to selective episodic memories 24 hrs later. Time-dependent memory competition provides a unifying account for memory dysfunctions in posttraumatic stress disorders.

neuroscience↗