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NIBB / News : PressRelease tag:www.nibb.ac.jp,2011-06-12:/pressroom//6 2026-07-10T01:35:09Z [Press Release] A New and Efficient Method for Preparing Pseudopregnant Mice Promotes Laboratory Animal Welfare tag:www.nibb.ac.jp,2026:/pressroom/news//7.10638 2026-07-06T02:00:00Z 2026-07-06T02:16:10Z NIBB - OFFICE OF PUBLIC RELATIONS AND INTERNATIONAL COOPERATION Researchers at the National Institute for Basic Biology (NIBB) have developed an alternative approach for preparing pseudopregnant recipient mice by utilizing female mice showing nonestrous signs. By combining the Lee-Boot and Whitten effects, this method achieves stable copulation and pregnancy rates. The approach offers a practical solution for research facilities to significantly reduce the number of stock animals maintained for embryo transfers, directly aligning with the "Reduction" principle of laboratory animal welfare (the 3Rs).

A mouse maintained in a laboratory environment.

In biomedical research utilizing mouse models, the preparation of pseudopregnant recipient females is a standard step in embryo transfer protocols. Conventionally, this process requires technicians to select female mice demonstrating clear signs of estrus. Because only a limited percentage of mice naturally enter this stage daily, facilities often maintain a relatively large stock of female mice. Furthermore, group housing can induce the "Lee-Boot effect," a biological phenomenon where caged females suppress each other's estrous cycles, thereby decreasing selection efficiency and requiring careful management to ensure animal well-being.

In a study published in the Journal of the American Association for Laboratory Animal Science (JAALAS), Yuji Noguchi and Eiji Watanabe at the National Institute for Basic Biology (NIBB) investigated a methodological adjustment to this protocol. The study explores whether pseudopregnant recipients can be reliably prepared by actively utilizing female mice that exhibit nonestrous signs, rather than searching exclusively for those in estrus.

The evaluated method integrates existing biological effects to optimize institutional resources. First, female mice were group-housed to intentionally induce the Lee-Boot effect, maximizing the proportion of nonestrous individuals. These female mice were then introduced to vasectomized males for three days. The introduction of male pheromones stimulates the "Whitten effect," synchronizing the females' estrous cycles and leading to targeted copulation on the third day.

"By adjusting our protocol to include mice showing nonestrous signs, which are typically bypassed in standard screening, we can establish a more predictable and sustainable preparation system," states Yuji Noguchi, the lead author of the study. Eiji Watanabe, the corresponding author of the study, further highlights the broader ethical and practical impact of this research: "The primary benefit of this approach is that it allows laboratories to significantly minimize the number of stock animals they need to maintain. This optimizes facility space and directly supports the 3Rs principles—specifically the 'Reduction' of animal use in scientific procedures."

[Paper Information]
Journal of the American Association for Laboratory Animal Science
Preparation of Pseudopregnant Recipient Females Using Female Mice (Mus musculus) Showing Nonestrous Signs: Investigation of a Unique Approach Based on the Whitten Effect
Yuji Noguchi and Eiji Watanabe
DOI: https://doi.org/10.30802/AALAS-JAALAS-25-131 ]]> [Press Release] How does light travel through the cell’s inhomogeneous interior? A coupled transport model captures refraction and attenuation simultaneously and confirms optical reciprocity in heterogeneous biological media tag:www.nibb.ac.jp,2026:/pressroom/news//7.10597 2026-06-01T06:00:00Z 2026-06-09T01:44:34Z NIBB - OFFICE OF PUBLIC RELATIONS AND INTERNATIONAL COOPERATION Researchers at ExCELLS derive a coupled transport model that simultaneously reconstructs refractive-index fluctuations and attenuation coefficients without weak-absorption approximations, and experimentally verify optical reciprocity in HeLa cells.

Light traveling through living cells is shaped by two interlinked processes—refraction from inhomogeneous structure and attenuation from absorption and scattering. Conventional phase-imaging methods can describe only one at a time. A new study from the Exploratory Research Center on Life and Living Systems (ExCELLS) of the National Institutes of Natural Sciences introduces a unified transport model that captures both processes simultaneously, defines exactly where the model can be applied, and confirms that biological tissues preserve a fundamental symmetry of light propagation across three orders of magnitude in optical depth. The model’s outputs may further be translated into intracellular physical properties such as fluid viscosity, density, and local temperature, opening a route toward reading cellular environments quantitatively through light.

Quantitative phase imaging extracts phase information from through-focus intensity images without interferometry, with the transport of intensity equation (TIE) as its mathematical foundation. The classical TIE, however, assumes purely refractive objects—an assumption that breaks down for real biological samples, where refraction and attenuation are intertwined. A research team led by Dr. Masaki Watabe (Exploratory Research Center on Life and Living Systems (ExCELLS) / (National Institute for Basic Biology (NIBB)) and Dr. Joe Sakamoto (Exploratory Research Center on Life and Living Systems (ExCELLS) / National Institute for Physiological Sciences (NIPS)) started from the paraxial wave equation with a complex optical potential and derived a coupled transport model (the coupled TIE-TPE framework) consisting of two transport equations—a generalized TIE for intensity evolution and a transport of phase equation (TPE) for phase evolution. By decomposing the refractive index into a uniform mean field and a local fluctuation field, the resulting non-divergent system simultaneously reconstructs refractive-index fluctuations (Δn) and attenuation coefficients (μ) without linearization or weak-absorption approximations.

The model also yields explicit validity bounds—derived from the paraxial condition combined with photon-counting statistics and the diffraction limit—that specify in advance the parameter range over which reconstruction is guaranteed to be consistent. Experimental validation was carried out across three systems with markedly different optical properties: precision-fabricated microlens arrays (numerical aperture NA = 0.45), cultured HeLa cells (NA = 1.20), and HeLa cell membranes imaged with an oil-immersion objective (NA = 1.49). In all cases, the reconstructed Δn and μ distributions fell within the predicted validity region, and subcellular structures including nuclei and organelles were clearly resolved through refractive-index contrast even in the transparent-limit regime where attenuation signals approach detection thresholds.

The authors further introduced an attenuation asymmetry parameter Aκ—quantifying the imbalance between forward and backward propagation—and measured it as a function of optical depth. Aκ was found to be statistically consistent with zero across three orders of magnitude in optical depth, with systematic errors from high-numerical-aperture optics remaining well below statistical uncertainties. This provides the first quantitative experimental confirmation that optical reciprocity is preserved in heterogeneous biological media at the wavelength scale.

FIg. HeLa cell results
Results for HeLa cells. (a) Optical path for the bright-field imaging system with a wide-field microscope. (b) Through-focus intensity distributions I(r⊥, z₀ − Δz), I(r⊥, z₀), and I(r⊥, z₀ + Δz). (c) Phase distributions reconstructed from the three intensity images. (d) Reconstructed spatial distribution of the refractive-index fluctuation Δn and (e) the attenuation coefficient μ. (f) Correlation pattern between Δn(r⊥, z₀) and μ(r⊥, z₀). The black solid line indicates the 3σ confidence level, and the green area shows the physical parameter boundaries (validity region) given by the validity-bound equation in the main text. In this sample, 65,055 events (24.82%) fall outside the green region. (g) Attenuation asymmetry Aκ as a function of optical depth log₁₀|μΔz|. The blue solid line and band denote the statistical mean and the root mean squared (RMS) value of Aκ, respectively, and the dashed line indicates Aκ = 0.

[EurekAlert!]
https://www.eurekalert.org/news-releases/1130448

[Paper Information]
Journal Name: Physical Review A
Journal Title: Coupled amplitude-phase transport in heterogeneous optical media
Article Publication Date: 18 May 2026
DOI: 10.1103/zjh7-3bdb
]]> [Press Release] Head stabilization behavior and underlying neural circuit mechanisms discovered in fish without a “neck” tag:www.nibb.ac.jp,2026:/pressroom/news//7.10595 2026-05-18T06:00:00Z 2026-06-09T01:32:45Z NIBB - OFFICE OF PUBLIC RELATIONS AND INTERNATIONAL COOPERATION Uncovering the origins of head stabilization mechanisms that rely on the “neck”

In tetrapods with a “neck,” head stability is achieved by contracting and relaxing neck muscles. Whether head stabilization exists in fish, which lack a “neck,” was previously unknown. The research group discovered for the first time that fish can also stabilize their heads against tilting, and identified the neural circuits and muscles responsible for this behavior. The neural circuit architecture underlying head stabilization in fish shares features with that governing neck-based head stabilization in tetrapods, suggesting this research may shed light on the evolutionary origins of head stabilization behavior and the morphological neck.

Postural control is a fundamental behavior for most animals, and head stability in particular plays a crucial role in achieving stable sensory input, accurate spatial perception, and efficient motor output. Tetrapods, including humans, possess a “neck” — a structure that separates the skull from the trunk skeleton — and stabilize their head in space by contracting and relaxing neck muscles in response to body tilt. This reflexive mechanism is known as the vestibulo-collic reflex. Fish, by contrast, have their skull directly connected to the trunk skeleton and therefore lack a morphological “neck.” Whether these neckless animals possess a head stabilization behavior equivalent to the tetrapod vestibulo-collic reflex was unknown.

A research group led by Takumi Sugioka (Researcher), Masashi Tanimoto (Assistant Professor), and Shin-ichi Higashijima (Professor) at the Exploratory Research Center on Life and Living Systems (ExCELLS) / National Institute for Basic Biology (NIBB), National Institutes of Natural Sciences, collaborated with Dr. Herwig Baier and Dr. Tod R. Thiele from the Max Planck Institute in Germany. Using larval zebrafish — a model organism with a relatively simple body plan well-suited for neural circuit research — the team first conducted detailed behavioral observations. They found that the degree of trunk flexion changes in accordance with the angle of body tilt. This trunk flexion shifts the orientation of the head toward horizontal, effectively stabilizing the head in space.

Next, the group succeeded in identifying the neural circuits and muscles involved in trunk flexion through activity measurements and cell ablation experiments during tilting. Although head stabilization behavior in fish — which lack a morphological neck — had not been previously characterized, this study demonstrates for the first time that fish also possess such behavior. Because fish lack a “neck,” the muscles involved cannot be called “neck muscles.” Nevertheless, the neural circuit underlying this behavior shares multiple structural and neuronal features with the mammalian vestibulo-collic reflex circuit. These findings suggest that the trunk flexion observed in fish may represent an evolutionarily ancestral mechanism of the vestibulo-collic reflex. This research is expected to illuminate the origins of the vestibulo-collic reflex and may open new avenues for understanding the evolutionary emergence of the vertebrate neck.

During head-up posture, fish perform ventral flexion of the trunk to partially stabilize the head. Conversely, during head-down posture, they perform dorsal flexion to achieve head stabilization. Ventral flexion during head-up tilting is driven by the circuit shown in orange (vestibular nucleus -> reticulospinal neurons -> spinal motor neurons -> ventral specialized muscles), while dorsal flexion during head-down tilting is driven by the circuit shown in green (vestibular nucleus -> spinal motor neurons -> dorsal specialized muscles).

[EurekAlert!]
https://www.eurekalert.org/news-releases/1129448

[Paper Information]
Journal Name: Communications Biology
Article Title: Head stabilization behavior and underlying circuit mechanisms in larval zebrafish
Article Publication Date: April 4th 2026
DOI: doi.org/10.1038/s42003-026-09990-4
]]> [Press Release] A new way to detect life beyond Earth without knowing what life looks like -Researchers propose a population-scale biosignature based on how life may spread between planets- tag:www.nibb.ac.jp,2026:/pressroom/news//7.10584 2026-04-15T05:00:00Z 2026-04-15T06:40:54Z NIBB - OFFICE OF PUBLIC RELATIONS AND INTERNATIONAL COOPERATION A research team of Specially Appointed Associate Professor Harrison B. Smith of Earth-Life Science Institute (ELSI) at Institute of Science Tokyo and Specially Appointed Associate Professor Lana Sinapayen of National Institute for Basic Biology has developed a new approach to detecting life beyond Earth that does not rely on identifying specific biological markers. Instead, the study suggests that life may be detectable through patterns emerging across groups of planets, offering a new framework for astrobiology in situations where traditional biosignatures are ambiguous or unreliable.
One of the main challenges in astrobiology is establishing whether observed features of distant planets genuinely indicate the presence of life. Traditional biosignatures, such as atmospheric gases, can often produce false positives through non-biological processes. Although technosignatures might offer more reliable signals, they rely heavily on strong assumptions about the nature and behaviour of extraterrestrial intelligence.

To overcome these limitations, the researchers considered a fundamentally different idea: instead of searching for life on individual planets, what if life could be detected through its collective effects across many planets?

The study presents an "agnostic biosignature"—a method that does not rely on knowing in detail what life consists of or how it functions. Instead, it is based on two broad assumptions: that life can spread between planets (for example, through panspermia), and that it can modify planetary environments over time.

Using an agent-based simulation, the researchers modelled how life might spread across star systems and alter planetary characteristics. They discovered that if life extends and impacts planetary environments, it produces detectable statistical correlations between planet locations and their observable traits.

Crucially, these correlations appear even without pinpointing a particular biosignature on any individual planet.

Beyond detecting the presence of life, the researchers also developed a method to identify which planets are most likely to host it. By clustering planets based on their observable characteristics and spatial relationships, they were able to isolate groups of planets with a high probability of having been influenced by life.

This approach prioritises reliability over completeness: it minimises false positives, even if it misses some life-bearing planets. Such a strategy is especially useful for guiding follow-up observations with limited telescope time.

"By focusing on how life spreads and interacts with environments, we can search for it without needing a perfect definition or a single definitive signal," said Harrison B. Smith. Lana Sinapayen added, "Even if life elsewhere is fundamentally different from life on Earth, its large-scale effects, such as spreading and modifying planets, may still leave detectable traces. That's what makes this approach compelling."

The findings indicate that future astronomical surveys, which will observe large numbers of exoplanets, could employ statistical methods to detect life on a population level. This approach might be especially useful when individual biosignatures are faint, ambiguous, or susceptible to false positives.

The study also highlights the importance of better understanding the baseline diversity of planets formed without life, as this will improve the reliability of detecting deviations caused by biological processes.

While the current work relies on simulations, it provides a conceptual basis for a new category of life-detection methods. The researchers emphasise that future efforts must incorporate more realistic planetary data and galactic dynamics. Nevertheless, the results suggest that life could be detectable even without understanding its chemistry, by recognising the patterns it leaves throughout the cosmos.

Image 1.
Title: Iterative terraformation
Caption: The concept behind the model is simple: life can travel to and terraform planets around other stars. In doing so, the planet that life travels to becomes more similar to the planet it came from. In this example, life from a planet resembling Earth travels to a red planet. The process plays out again and again. Each time, after being terraformed, a planet becomes more "Earth-like" than would be expected from random chance, given the locations of the planets. However, the focus is not on identifying Earth-like planets. Instead, the aim is to identify any group of planets that are more similar to each other than would be expected by chance, and are localised in space. This technique is agnostic: it does not require making assumptions about habitability or passing judgment on the "kinds of planets" that are amenable to life.
Credit: Harrison B. Smith
License: CC BY-NC-ND

Image 2.
Title: Panspermia correlations
Caption: If life can travel to other planets and terraform them, it is expected that patterns will emerge between the locations of planets and their observable characteristics (for example, atmospheric composition). On the left, planets (coloured dots) show no correlation between their locations and their characteristics (represented by colour). However, if life capable of panspermia and terraforming arises, then correlations emerge (shown as dashed line groups of similar colours). In the model, life chooses its destination by looking for the planet with the most similar composition within some maximum distance (shown on the left by a dashed circle).
Credit: Harrison B. Smith
License: CC BY-NC-ND

]]> [Press Release] New microscope reveals previously hidden differences in photosynthetic light-harvesting antennae tag:www.nibb.ac.jp,2026:/pressroom/news//7.10582 2026-04-13T05:00:00Z 2026-04-30T05:42:02Z NIBB - OFFICE OF PUBLIC RELATIONS AND INTERNATIONAL COOPERATION
Plants and photosynthetic bacteria have a wide variety of light-harvesting antennae in which pigment molecules are precisely arranged to utilize light energy efficiently. However, these molecular arrangements are not perfectly uniform and vary from particle to particle because of conformational distortions and fluctuations. Such structural variations are considered to perturb excited states and energy transfer processes triggered by light absorption. Because these early excitation dynamics initiate a cascade of photosynthetic photochemical reactions, understanding the effects of such fluctuations and heterogeneities is essential for revealing how phototrophic organisms maintain efficient and stable photosynthesis.

To analyze these fluctuations and heterogeneities, single-molecule fluorescence spectroscopy has been widely utilized. However, the fluorescence-based approach faces fundamental challenges in observing ultrafast and multistep processes, as well as non-fluorescent dark states and radical species. In contrast, transient absorption spectroscopy can track excitation dynamics, including excited-state relaxation and energy transfer, on the femtosecond timescale. Until now, however, improving its sensitivity to the single-molecule level has remained a major challenge. This technical breakthrough is expected to open the door to a deeper understanding of the regulatory mechanisms of photosynthetic photochemical systems in which fluctuations and heterogeneities are intrinsic.

An article published in The Journal of Physical Chemistry Letters describes a new transient absorption microscope developed by a research group led by Prof. Toru Kondo at the National Institute for Basic Biology (NIBB) / the Exploratory Research Center on Life and Living Systems (ExCELLS) / SOKENDAI. This microscope integrates a unique optical alignment for single-objective absorption microscopy, a highly sensitive balanced detector, and lock-in-amplified detection, allowing femtosecond time-resolved transient absorption measurements to be performed continuously at a high repetition rate. Moreover, steady-state absorption and fluorescence measurements, i.e., simultaneous absorption and fluorescence imaging, can be performed. Furthermore, the fluorescence spectrum and lifetime can be acquired. The spatial resolution is ~300 nanometers, near the diffraction limit; the temporal resolution is less than 200 femtoseconds; and the detection sensitivity of the transient absorption signal is about 10^–7 in absorbance, approaching the single-molecule level.

Using the newly developed microscope, the research group analyzed Zn-HM pigment self-aggregates that mimic the chlorosome, a photosynthetic light-harvesting antenna found in green sulfur bacteria. As a result, they identified two kinetic components with nearly identical time constants based on differences in their time-constant distributions that are averaged out in conventional ensemble measurements. Moreover, they succeeded in quantifying the photophysical properties associated with these components, such as absorbance, fluorescence efficiency, and fluorescence peak ratio, revealing how structural heterogeneity and disorder contribute to excitation dynamics and excitonic coherence domains.

Graduate student Shun Arai, the first author of the paper, says, “Structural fluctuations and heterogeneities inherently exist not only in photosynthetic systems, but also in living systems as a whole. We believe that our original microscope and analytical framework can deepen our understanding of living systems from the perspective of heterogeneous local dynamics”. Furthermore, Toru Kondo says, “A key advance of this work is the establishment of a new spectroscopic analysis method that exploits interparticle heterogeneity itself as meaningful information, rather than focusing only on average time constants. Although heterogeneity has often been treated merely as noise and averaged out, this study shows that actively resolving it can reveal the essential photophysical properties”.

The new ultrafast microspectroscopic approach established in this study can be widely applied to the analysis of light-harvesting antennae and reaction centers responsible for photoconversion processes in photosynthetic organisms. Moreover, its applicability is not limited to photosynthesis research but also extends to materials development research on organic photofunctional devices, artificial light-harvesting systems, and molecular electronics. It is expected to provide novel materials design principles by revealing the relationship between microscopic structures and photophysical properties at the single-molecule or single-particle level, a relationship that is difficult to elucidate using conventional ensemble-averaging techniques.

Fig. Schematic diagram (left) and photograph (right) of the newly developed high-sensitivity transient absorption microscope.
Image credit: Toru Kondo

EurekAlert!
https://www.eurekalert.org/news-releases/1125960]]> [Press Release] Gravity sensing without a brain: a minimal neural circuit controls posture in a ctenophore tag:www.nibb.ac.jp,2026:/pressroom/news//7.10503 2026-03-13T05:00:00Z 2026-03-27T00:18:43Z NIBB - OFFICE OF PUBLIC RELATIONS AND INTERNATIONAL COOPERATION

A research team led by Dr. Kei Jokura (National Institute for Basic Biology (NIBB) and Exploratory Research Center on Life and Living Systems (ExCELLS)) and Prof. Gáspár Jékely (Centre for Organismal Studies (COS), Heidelberg University) examined the cellular organization and neural connectivity of the ctenophore gravity-sensing organ, the statocyst. In work published in eLife, they used volume electron microscopy to reconstruct the larval statocyst in three dimensions and generate its complete connectome. Reconstructing more than 1,000 cells across 12 distinct cell types, the team found that the entire neural network is composed of just three large, morphologically complex, multinucleated neurons.

"It was striking to find that the entire network is built from only three neurons," says Jokura.

Previous studies had suggested neural involvement in controlling the balancer cilia, but the circuit architecture itself had remained unknown. "The statocyst consists of a statolith and four bundles of cilia known as balancer cilia," Jokura explains. "These balancer cilia beat spontaneously, and their amplitude changes with body tilt. Mechanical signals are transmitted from the balancer cilia to the comb rows, ultimately regulating swimming behavior." These three neurons form an interconnected network that modulates this beating of the balancer cilia.

Using high-speed imaging, the researchers then examined how this activity is controlled. Ciliary arrest events showed slight temporal delay, whereas the reactivation occurred almost simultaneously. Integrating these dynamics with the reconstructed circuit suggests that distinct neurons independently regulate the arrest and restart phases of ciliary movement. "The statocyst is not simply a relay," Jokura adds. "It is an active, integrative circuit that dynamically coordinates ciliary activity."

These findings provide new insight into the fundamental organization of nervous systems. Nervous systems are often viewed as centralized structures that collect sensory inputs and issue motor commands. Here, however, a decentralized nerve net achieves precise motor control without a central integrative hub. More broadly, the results suggest that neural circuits can operate as self-organized control systems, generating coordinated outputs through network-level interactions. This challenges the traditional linear view of nervous system evolution, in which simple nerve nets gradually gave rise to centralized brains. Instead, sophisticated integrative mechanisms may already have existed in early-diverging animal lineages.

The team now aims to uncover the electrophysiological and molecular basis of this network, to understand how diverse sensory inputs are integrated within the statocyst.

A ctenophore larva. The small, round, bright structure in the upper right is the statolith, inside the statocyst, a gravity-sensing organ.
Credit: Kei Jokura

Eurekalert!
https://www.eurekalert.org/news-releases/1121500

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