Biology subjects

Hayakawa, K.

Publications and source records attributed to Hayakawa, K..

8 recordsLinked to original sources

bioRxiv2026

Selective depletion of AMH-expressing granulosa cells in vivo impairs follicular development and fertility in female mice

In mammals, ovarian follicle development is a highly coordinated process that underlies female fertility. Granulosa cells expressing anti-Mullerian hormone (AMH) are widely used as a marker of growing follicles. However, the in vivo roles of granulosa cells in follicular development and female fertility remain unclear. Here, we analyzed AMH-toxin receptor-mediated cell knockout (AMH-TRECK) transgenic (Tg) mice on a NOG background, in which AMH-expressing granulosa cells are specifically depleted by diphtheria toxin (DT). We first found that, after a single DT injection into postnatal AMH-TRECK Tg females, AMH-expressing granulosa cells in primary and secondary follicles exhibited cleaved caspase-3 signals 1 day later and were depleted 4 days later. Second, after repeated DT injections weekly from 1 to 7 weeks of age in AMH-TRECK Tg females, antral follicles and corpora lutea were rarely observed, and the numbers of primordial, primary, and secondary follicles were decreased. Following PMSG and hCG stimulation, repeated DT-injected Tg females exhibited a reduced number of ovulated oocytes with a low proportion of mature oocytes, resulting in reduced IVF rates and fertility. Further, after a cessation of repeated DT treatment, ovarian weight and follicular development recovered: the numbers of primary, secondary, and antral follicles were recovered, whereas the primordial follicle pool remains reduced. We conclude that selective depletion of AMH-expressing granulosa cells in vivo impairs follicular development and fertility. Our model enables assessment of the in vivo effects of granulosa cell depletion and may provide a useful platform for future transplantation-based studies to understand complex follicular dynamics.

developmental biology↗

bioRxiv2025

Couples in the deep: dissolved organic and microbial communities in the oxygenated hypolimnion of a deep freshwater lake

The interaction between dissolved organic matter (DOM) and microbial communities is a critical yet understudied driver of biogeochemical cycling in aquatic ecosystems. Understanding these interactions is essential for elucidating the chemical and microbial dynamics that sustain ecosystem functionings. Here, we combined non-target ultra high-resolution mass spectrometry-based environmental metabolome analysis with microbiome analysis to conduct the first comprehensive investigation of DOM-microbe linkages in both the epilimnion and oxygenated hypolimnion of a deep freshwater lake throughout the stratification period, with Lake Biwa (Japan) as a model system. To facilitate interpretation of DOM-microbe networks, we developed an integrated compound category classification (IC3) framework for assigning molecular formulae (MFs) to specific compound categories. Using a compositional data analysis framework, we identified specific MFs and bacterial taxa that covaried in the hypolimnion, which exhibited substantially more complex networks than the epilimnion. These networks encompassed 1705 out of the 1755 common MFs, representing the majority of total peak intensities, underscoring stronger DOM-microbe coupling in deep waters. Hypolimnion specialist bacteria were associated with specific MFs and co-ocuuring taxa, providing environmental metabolomic evidence for substrate preference and potential symbiotic relations. Notably, more than three-fourths of these MFs in relative abundance were classified as recalcitrant, including lipid-, lignin-, tannin-like, and carboxyl-rich alicyclic molecules, suggesting the capability of hypolimnion specialists to use or produce these compounds. Our study offers the first high-resolution insights into DOM-microbe associations in a deep freshwater lake and establishes a framework for more efficient and robust analyses of such interactions.

ecology↗

bioRxiv2023

Impact of climate change and oligotrophication on quality and quantity of lake primary production: A case study in Lake Biwa

Global climate change and anthropogenic oligotrophication are expected to reshape the dynamics of primary production (PP) in aquatic ecosystems; however, few studies have explored their long-term effects. In theory, the PP of phytoplankton in Lake Biwa may decline over decades due to warming, heightened stratification, and anthropogenic oligotrophication. Furthermore, the PP of large phytoplankton, which are inedible to zooplankton, along with biomass-specific productivity (PBc), could decrease. In this study, data from 1976-2021 and active fluorometry measurements taken in 2020 and 2021 were evaluated. Quantitatively, the temporal dynamics of mean seasonal PP during 1971-2021 were assessed according to the carbon fixation rate to investigate relationships among environmental factors. Qualitatively, phytoplankton biomass, PP, and PBc were measured in two size fractions [edible (S) or inedible (L) for zooplankton] in 2020 and 2021, and the L:S balance for these three measures was compared between 1992 (low-temperature/high-nutrient conditions) and 2020-2021 (high-temperature/low-nutrient conditions) to assess seasonal dynamics. The results indicated that climate change and anthropogenic oligotrophication over the past 50 years have diminished Lake Biwas PP since the 1990s, impacting the phenology of PP dynamics. However, the L:S balance in PP and PBc has exhibited minimal change since 1992. These findings suggest that, although climate change and oligotrophication may reduce overall PP, they do not markedly alter the inedible/edible phytoplankton balance in terms of PP and PBc. Instead, as total PP declines, the production of small edible phytoplankton decreases proportionally, potentially affecting trophic transfer efficiency and material cycling in Lake Biwa.

ecology↗

bioRxiv2022

A newly-recognized population of residual neural crest cells in the adult leptomeninges is re-activated for vascular repair

The neural crest (NC) is a transient structure in vertebrate embryogenesis comprising highly migratory multipotent stem cells that give rise to a diverse array of cell types in organs throughout the body, including initiating neurovascular patterning. It is assumed that neural crest stem cells (NCSCs) disappear after development. Unexpectedly, using single-nucleus RNA-sequencing, we discovered residual quiescent NCSCs in the adult mouse meninges which are activated by injury and contribute to the brains homeostatic response. RNA velocity, pathway, and transcription factor analyses in a murine stroke model (combined with in vivo imaging) show that these adult NCSCs migrate towards the perivascular spaces of the infarct and undergo a perivascular stromal cell transition that is regulated by Ptp1b, Ghr, and Stat3. Loss- and gain-of-function experiments show that these "vestigial" NCSCs are required for restoring vascular endothelial barrier function via {beta}-catenin and Stat3 signaling. These findings suggest that, in the adult, an unexpected reservoir of cells -- once pivotal to embryogenesis and vascular morphogenesis -- are re-invoked for neurovascular repair.

neuroscience↗

bioRxiv2021

Size-dependent susceptibility of lake phytoplankton to light stress: An implication for succession of large green algae in a deep oligotrophic lake

Field observations of the population dynamics and measurements of photophysiology in Lake Biwa were conducted by size class (< vs. > 30 m) from early summer to autumn to investigate the relationships between susceptibility to light stress and cell size. Also, a nutrient bioassay was conducted to clarify whether the growth rate and photosystem II (PSII) photochemistry of small and large phytoplankton are limited by nutrient availability. Large phytoplankton, which have lower intracellular Chl-a concentrations, had higher maximum PSII photochemical efficiency (Fv/Fm) but lower non-photochemical quenching (NPQNSV) than small phytoplankton under both dark and increased light conditions. The nutrient bioassay revealed that the PSII photochemistry of small phytoplankton was restricted by N and P deficiency at the pelagic site even at the end of the stratification period, while that of large phytoplankton was not. These results suggest that large phytoplankton have lower susceptibility to PSII photodamage than small phytoplankton due to lower intracellular Chl-a concentrations. The size dependency of susceptibility to PSII photoinactivation may play a key role in large algal blooms in oligotrophic water.

microbiology↗

bioRxiv2020

Development of photosynthetic carbon fixation model using multi-excitation wavelength fast repetition rate fluorometry in Lake Biwa

Direct measurements of gross primary productivity (GPP) in the water column are essential, but can be spatially and temporally restrictive. Fast repetition rate fluorometry (FRRf) is a bio-optical technique based on chlorophyll a (Chl-a) fluorescence that can estimate the electron transport rate (ETRPSII) at photosystem II (PSII) of phytoplankton in real time. However, derivation of phytoplankton GPP in carbon units from ETRPSII remains challenging because the electron requirement for carbon fixation ([FE]e,C) can vary depending on multiple factors. Also, the FRRf is still relatively novel, especially in freshwater ecosystems where phosphorus limitation and cyanobacterial blooms are common. The goal of the present study is to construct a robust [FE]e,C model for freshwater ecosystems using simultaneous measurements of ETRPSII by FRRf with multi-excitation wavelengths coupled with traditional carbon fixation rate by the 13C method. The study was conducted in oligotrophic and mesotrophic areas in Lake Biwa from July 2018 to May 2019. The combination of excitation light at 444, 512 and 633 nm correctly estimated ETRPSII of cyanobacteria. The range of [FE]e,C in the phytoplankton community varied from 1.1 to 31.0 mol e- mol C-1 during the study period. Generalized liner model showed the best model including 12 physicochemical and biological factors explained 67% of the variance in [FE]e,C. Among all factors, water temperature was the most significant, while PAR intensity was not. The GPP values estimated by FRRf (GPPf) with the best [FE]e,C model relative to 13C (GPP13C) varied 0.5-1.5. Further, GPPf estimated with more parsimonious [FE]e,C models were also comparable to GPP13C. This study quantifies the applicability of the in situ FRRf methodology, and supports continuous monitoring of GPP by FRRf in lakes with large spatio-temporal variability of environmental conditions and phytoplankton assemblages.

microbiology↗

bioRxiv2020

Comparison of de-duplication methods used by WHO Global Antimicrobial Resistance Surveillance System (GLASS) and Japan Nosocomial Infections Surveillance (JANIS) in the surveillance of antimicrobial resistance

A major issue in the surveillance of antimicrobial resistance (AMR) is "de-duplication" or removal of repeated isolates, for which there exist multiple methods. The World Health Organization (WHO) Global Antimicrobial Resistance Surveillance System (GLASS) requires de-duplication by selecting only the first isolate of a given bacterial species per patient per surveillance period per specimen type per age group, gender, and infection origin stratification. However, no study on the comparative application of this method has been reported. The objective of this study was to evaluate differences in data tabulation between the WHO GLASS and the Japan Nosocomial Infections Surveillance (JANIS) system, which counts both patients and isolates after removing repeated isolates of the same bacterial species per multiresistance phenotype isolated from a patient within 30 days, regardless of specimen type. All bacterial data, consisting of approximately 8 million samples from 1795 Japanese hospitals in 2017 were exported from the JANIS database, and were tabulated using either the de-duplication algorithm of GLASS, or JANIS. We compared the tabulated results of the total number of patients whose blood and urine cultures were taken and of the percentage of resistant isolates of Escherichia coli for each priority antibiotic. The number of patients per specimen type tabulated by the JANIS method was always smaller than that of GLASS. There was a small (< 3%) difference in the percentage of resistance of E. coli for any antibiotic between the two methods in both out- and inpatient settings and blood and urine isolates. The two tabulation methods did not show considerable differences in terms of the tabulated percentages of resistance for E. coli. We further discuss how the use of GLASS tabulations to create a public software and website that could help to facilitate the understanding of and treatment against AMR.

microbiology↗

bioRxiv2017

Mid-Infrared Free-Electron Laser-Evoked Discharge Of Crayfish Compound Eyes

Light perception is an intriguing subject, and it has been demonstrated that some animals can perceive wavelengths beyond human vision. However, it is still controversial whether animals can see mid-infrared radiation. A combination of two free-electron laser (FEL) facilities, LEBRA-FEL (Nihon University) and KU-FEL (Kyoto University), can provide light sources with high peak power and spatially coherent monochromatic wavelengths that are continuously tuneable from 400 nm to 20 m. We show that the crayfish (Procambarus clarkii) compound eye responds to pulsed mid-infrared FELs (1 Hz for KU-FEL; 2 Hz for LEBRA-FEL) from 3 to 17 m. Our finding provides insight into the animals visual sensing of mid-infrared radiation, and that the sensing does not depend on thermal effects. Although the behavioural reason for vision in this wavelength range and the mechanism are still under investigation, understanding this type of visual sensing may lead to applications other than photophysical applications.

physiology↗