Publications by authors named "Ryota Nakajima"

The influx of microplastics (MPs) into the Arctic Ocean poses a collective risk, particularly with pronounced sea ice depletion due to global warming. A total of 73 replicate sediment samples were collected at different depths (38 to 79 m) from Chukchi and the Beaufort Seas at 8 stations in the Arctic region during the R/V Mirai cruise (MR22-06C) from August to September 2022. The average concentration of MPs is 79.

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The Kuroshio Extension recirculation gyre in the western North Pacific is an accumulation site of plastic litter transported by the Kuroshio Current. A sediment trap was moored at a depth of 4900 m at Station KEO within the Kuroshio Extension recirculation gyre, and the vertical flux of microplastics in sinking particles of size <1 mm was observed. Forty-one sediment-trap samples collected from July 1, 2014, to October 2, 2016, were analyzed with a micro-Fourier transform infrared spectrometer and microplastics were detected in all samples.

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The rhizomes of Schott and Solander are widely used for treating amnesia in traditional Chinese medicine. In contrast, their leaves are usually discarded without their medicinal properties being known. Here, we found that the hot water extract of leaves improved cognition and tau pathology in model mice of frontotemporal dementia, similar to or even better than that of rhizomes.

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Article Synopsis
  • Microbes are capable of breaking down biodegradable plastics in various environments, but their effectiveness in the deep sea was previously uncertain.
  • Research showed that certain biodegradable plastics were decomposed by microorganisms at deep-sea locations, although the rate of degradation decreased with increasing water depth.
  • Analysis revealed that specific microbes with genes for degrading plastic were present, indicating that while degradation occurs in the deep sea, it's significantly less efficient compared to coastal areas.
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With the high number of microplastic-like particles captured by net hauls including manta or neuston nets, it is often required to subsample in order to decrease sample volume for microplastic enumeration and analysis. Plankton splitter is commonly used to divide microplastic samples. However, current devices such as Folsom plankton splitter and Motoda box splitter have accuracy issues in separating highly buoyant microplastics, namely expanded polystyrene (EPS) as they tend to adhere to the inner walls.

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In the brain, many regions work in a network-like association, yet it is not known how durable these associations are in terms of activity and could survive without structural connections. To assess the association or similarity between brain regions with a generating approach, this study evaluated the similarity of activities of neurons within each region after disconnecting between regions. The "generation" approach here refers to using a multi-layer LSTM (Long Short-Term Memory) model to learn the rules of activity generation in one region and then apply that knowledge to generate activity in other regions.

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The brain is an organ that functions as a network of many elements connected in a nonuniform manner. In the brain, the neocortex is evolutionarily newest and is thought to be primarily responsible for the high intelligence of mammals. In the mature mammalian brain, all cortical regions are expected to have some degree of homology, but have some variations of local circuits to achieve specific functions performed by individual regions.

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  • Understanding how microplastics behave in oceans is key to tackling marine plastic pollution, especially since the deep seafloor is a major accumulation area for them.
  • A study in Sagami Bay revealed that the deepest parts of the ocean had a higher density of microplastics than previously seen, showing significant differences in the types and shapes of plastic found there compared to shallower areas.
  • The research indicates that microplastics from the surface layer sink to the abyssal plains, while those from land sources settle in shallower depths and are moved deeper by underwater currents.
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Background: This study aimed to conduct a preliminary evaluation of the effects of 6-methylsulfinylhexyl isothiocyanate (6-MSITC) contained in wasabi rhizomes on fatigue and sleep and to examine its safety through overdose study.

Methods: A total of 20 healthy volunteers who were experiencing daily fatigue were given powder containing 6-MSITC (4.8 mg/day of 6-MSITC) extracted from wasabi for 4 weeks.

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The accumulation of polybrominated diphenyl ethers (PBDEs) and benzotriazole UV stabilizers (BZT-UVs) were examined in the hadal amphipod caught from a near-land trench off the Japan island (9200 m). were collected from two distinct sites: one is located at the outlet of submarine canyons directly connected to land and the other is apart from the outlet and geographically isolated from the first site. The level of the PBDEs in at the canyon outlet (mean 219 ng/g lipid weight (l.

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A new organic superconductor (TEA)(HEDO-TTF-dc)·2(HCO) (HEDO-TTF-dc = ethylenedioxy-tetrathiafulvalene dicarboxylic acids) with an onset of 4.0 K, was successfully obtained using oxalic acid and HEDO-TTF-dc anion donor. The crystal structure analysis indicated that strong π-π overlaps and very strong intra- and inter-molecular hydrogen-bonding interactions exist between the HEDO-TTF-dc anion donors and oxalic acid molecules.

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Lipopolysaccharide (LPS), a component of the outer membrane of gram-negative bacteria, induces various biological reactions in vivo. Our previous study suggested that LPS administration disrupts respiratory chain complex activities, enhances reactive oxygen species production, especially in the liver mitochondria, and sensitizes mitochondrial permeability transition (MPT) pore opening in rats. However, it is unknown whether LPS-induced MPT pore opening in rats is similarly observed in mice and whether the mechanism is the same.

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Background: Wasabi (Eutrema japonicum) is a common pungent spice used in Japan. 6-Methylsulfinylhexyl isothiocyanate (6-MSITC) found in the rhizome of wasabi has been shown to have anti-inflammatory and antioxidant effects, as well as improve neuroinflammation and memory. Therefore, we hypothesized that these effects would be beneficial for treating myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

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Nicotinamide adenine dinucleotide (NAD) is a coenzyme essential for energy production. Recently, associations between NAD and aging-related diseases have been reported, and NAD precursors that increase NAD concentration in the body have been acknowledged as anti-aging supplements. However, there have been only a few studies on the link between aging or aging-related diseases and human blood NAD concentration because NAD and its precursors are unstable in blood and difficult to measure.

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The recent influx of microplastics into the Arctic Ocean may increase environmental stress on the western Arctic marine ecosystem, which is experiencing significant sea-ice loss due to global warming. Quantitative data on microplastics in the western Arctic Ocean are very limited, and the microplastic budget of the water column is completely unknown. To fill in gaps in our knowledge of Arctic microplastics, we observed surface concentrations (number of particles per unit volume of seawater) of meso- and microplastics using a neuston net, and we observed wind speeds and significant wave heights in the Chukchi Sea, Bering Strait, and Bering Sea.

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Chitin is a key component of hard parts in many organisms, but the biosynthesis of the two distinctive chitin allomorphs, α- and β-chitin, is not well understood. The accurate determination of chitin allomorphs in natural biomaterials is vital. Many chitin-secreting living organisms, however, produce poorly crystalline chitin.

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Acute myocarditis is a rare but serious complication associated with mRNA-based coronavirus disease 2019 (COVID-19) vaccination. In this article, four COVID-19 mRNA vaccination induced myocarditis cases managed at our tertiary Medical Center have been discussed. Three patients had typical myocarditis.

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Few studies have investigated the prevalence of polybrominated diphenyl ethers (PBDEs) in deep-sea sharks. In this study, the levels and profiles of PBDEs were determined in liver samples of eight different species of deep-sea sharks collected in Suruga Bay, Japan. Widespread contamination of PBDEs in the deep-sea environment was reconfirmed in this study as these persistent organic pollutants (POPs) were detected in all specimens analyzed.

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Article Synopsis
  • Hyperspectral data were analyzed for nine types of plastic particles in both large (1 mm) and small (100-500 μm) sizes on dry and wet glass fiber filters.
  • Smaller particles showed weaker reflectances, particularly on wet filters, due to the interaction between particle size and water absorption of infrared light.
  • Robust classification models were developed to accurately identify polymer types in wet conditions, even detecting microalgae-covered polystyrene beads, facilitating faster and easier analysis of microplastics.
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  • The study focuses on the abyssal seafloor at depths of 5700-5800 m beneath the Kuroshio Extension current system in the Northwest Pacific, highlighting limited knowledge about plastic debris in this region.
  • Video imagery was used to quantitatively assess the presence of plastic debris, finding that single-use plastics, particularly bags and food packaging, were the most common types of debris observed.
  • The density of plastic debris in this deep-sea zone was recorded at an average of 4561 items/km, indicating that the Northwest Pacific abyssal plain is a significant accumulation site for plastic pollution.
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Plastic waste has become a growing concern in terms of marine pollution, but little information is available on plastic debris and its possible risks of chemical additives exposure in the deep-sea. This study focused on identification of polymer type and additive concentrations in 21 plastic debris collected from deep-sea of Sagami Bay, Japan and West Pacific Ocean under the Kuroshio Extension and its recirculation gyre (KERG) zone (water depth: 1388-5819 m). Polyethylene (PE) was dominant polymer (57% of the total) in samples, followed by polyvinylchloride (PVC), epoxy resin, polyester (PES), and polypropylene.

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The retinoic acid receptor-related orphan nuclear receptor gamma t (RORγt), which is a promising therapeutic target for immune diseases, is a major transcription factor of genes related to psoriasis pathogenesis, such as interleukin (IL)-17A, IL-22, and IL-23R. Inspired by the co-crystal structure of RORγt, a 6-oxo-4-phenyl-hexanoic acid derivative 6a was designed, synthesized, and identified as a ligand of RORγt. The structure-activity relationship (SAR) studies in 6a, which focus on the improvement of its membrane permeability profile by introducing chlorine atoms, led to finding 12a, which has a potent RORγt inhibitory activity and a favorable pharmacokinetic profile.

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The comparative severity of patent foramen ovale (PFO)-related stroke in patients without atrial fibrillation (AF) and AF-related stroke in patients without PFO is unknown. Therefore, we compared the severity of PFO-related stroke and AF-related stroke. Twenty-six patients who underwent transesophageal echocardiography (TEE) were diagnosed with cardioembolic stroke from July 2018 to March 2020.

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Article Synopsis
  • - Plastic pollution poses serious threats to both aquatic and terrestrial ecosystems, and detecting small microplastics quickly is still a challenge.
  • - Researchers developed a method using optimized hyperspectral imaging to enhance the detection of microplastics by improving setup components, including lighting and camera adjustments.
  • - The enhanced imaging system significantly improved detection resolution from 250 µm to 14.8 µm, allowing for the rapid identification of microplastics as small as 100 µm, which could help better assess microplastic pollution.
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The retinoic acid receptor-related orphan nuclear receptor γt (RORγt), a promising therapeutic target, is a major transcription factor of genes related to psoriasis pathogenesis such as interleukin (IL)-17A, IL-22, and IL-23R. On the basis of the X-ray cocrystal structure of RORγt with , an analogue of the known piperazine RORγt inverse agonist , triazolopyridine derivatives of were designed and synthesized, and analogue was found to be a potent RORγt inverse agonist. Structure-activity relationship studies on , focusing on the treatment of its metabolically unstable cyclopentyl ring and the central piperazine core, led to a novel analogue, namely, 6-methyl--(7-methyl-8-(((2,4)-2-methyl-1-(4,4,4-trifluoro-3-(trifluoromethyl)butanoyl)piperidin-4-yl)oxy)[1,2,4]triazolo[1,5-]pyridin-6-yl)nicotinamide (), which exhibited strong RORγt inhibitory activity and a favorable pharmacokinetic profile.

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