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Research on chlorophyll degradation has progressed significantly in recent decades. In the 1990s, the structure of linear tetrapyrrole, which is unambiguously a chlorophyll degradation product, was determined. From the 2000s until the 2010s, the major enzymes involved in chlorophyll degradation were identified, and the pheophorbide a oxygenase/phyllobilin pathway was established. This degradation pathway encompasses several steps: (1) initial conversion of chlorophyll b to 7-hydroxymethyl chlorophyll a; (2) conversion of 7-hydroxymethyl chlorophyll a to chlorophyll a; (3) dechelation of chlorophyll a to pheophytin a; (4) dephytylation of pheophytin a to pheophorbide a; (5) opening of the macrocycle to yield a red chlorophyll catabolite; and (6) conversion of red chlorophyll catabolite to phyllobilins. This pathway converts potentially harmful chlorophyll into safe molecules of phyllobilins, which are stored in the central vacuole of terrestrial plants. The expression of chlorophyll-degrading enzymes is mediated by various transcription factors and influenced by light conditions, stress, and plant hormones. Chlorophyll degradation is differently regulated in different organs and developmental stages of plants. The initiation of chlorophyll degradation induces the further expression of chlorophyll-degrading enzymes, resulting in the acceleration of chlorophyll degradation. Chlorophyll degradation was initially considered the last reaction in senescence; however, chlorophyll degradation plays crucial roles in enhancing senescence, degrading chlorophyll-protein complexes, forming photosystem II, and maintaining seed quality. Therefore, controlling chlorophyll degradation has important agricultural applications.
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The polarization balance of M1/M2 macrophages with different functions is important in osteogenesis and bone repair processes. In a previous study, we succeeded in developing honeycomb tricalcium phosphate (TCP), which is a cylindrical scaffold with a honeycomb arrangement of straight pores, and we demonstrated that TCP with 300 and 500 µm pore diameters (300TCP and 500TCP) induced bone formation within the pores. However, the details of the influence of macrophage polarization on bone formation using engineered biomaterials, especially with respect to the geometric structure of the artificial biomaterials, are unknown. In this study, we examined whether differences in bone tissue formation due to differences in TCP geometry were due to the polarity of the assembling macrophages. Immunohistochemistry for IBA-1, iNOS, and CD163 single staining was performed. The 300TCP showed a marked infiltration of iNOS-positive cells, which are thought to be M1 macrophages, during the osteogenesis process, while no involvement of CD163-positive cells, which are thought to be M2 macrophages, was observed in the TCP pores. In addition, 500TCP showed a clustering of iNOS-positive cells and CD163-positive cells at 2 weeks, suggesting the involvement of M2 macrophages in the formation of bone tissue in the TCP pores. In conclusion, we demonstrated for the first time that the geometrical structure of the artificial biomaterial, i.e., the pore size of honeycomb TCP, affects the polarization of M1/2 macrophages and bone tissue formation in TCP pores.
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Single-chain fragment variables (scFvs), composed of variable heavy and light chains joined together by a peptide linker, can be produced using a cost-effective bacterial expression system, making them promising candidates for pharmaceutical applications. However, a versatile method for monitoring recombinant-protein production has not yet been developed. Herein, we report a novel anti-scFv aptamer-based biosensing system with high specificity and versatility. First, anti-scFv aptamers were screened using the competitive systematic evolution of ligands by exponential enrichment, focusing on a unique scFv-specific peptide linker. We selected two aptamers, P1-12 and P2-63, with KD = 2.1 µM or KD = 1.6 µM toward anti-human epidermal growth factor receptor (EGFR) scFv, respectively. These two aptamers can selectively bind to scFv but not to anti-EGFR Fv. Furthermore, the selected aptamers recognized various scFvs with different CDRs, such as anti-4-1BB and anti-hemoglobin scFv, indicating that they recognized a unique peptide linker region. An electrochemical sensor for anti-EGFR scFv was developed using anti-scFv aptamers based on square wave voltammetry. Thus, the constructed sensor could monitor anti-EGFR scFv concentrations in the range of 10-500 nM in a diluted medium for bacterial cultivation, which covered the expected concentration range for the recombinant production of scFvs. These achievements promise the realization of continuous monitoring sensors for pharmaceutical scFv, which will enable the real-time and versatile monitoring of large-scale scFv production.
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Aptâmeros de Nucleotídeos , Técnicas Biossensoriais , Receptores ErbB , Anticorpos de Cadeia Única , Aptâmeros de Nucleotídeos/química , Técnicas Biossensoriais/métodos , Anticorpos de Cadeia Única/química , Anticorpos de Cadeia Única/imunologia , Humanos , Proteínas Recombinantes/genética , Técnica de Seleção de Aptâmeros/métodos , Técnicas Eletroquímicas/métodosRESUMO
Talking to oneself using the second-person pronoun ["you" has been shown to enhance performance and autonomous motivation in English speakers. However, there is a lack of evidence on whether it can be replicated for speakers of other languages, such as Japanese, in which the grammatical subject is usually omitted in daily conversation. Based on self-determination theory, the present study examined the effects of second-person self-talk for a sample of Japanese individuals on task performance, intrinsic motivation, and three styles of extrinsically motivated regulations: identified, introjected, and external. We randomly assigned 411 undergraduate students to either an experimental group (second-person self-talk, first-person self-talk, and non-subject self-talk) or a control group. An anagram task was used to assess performance. No significant difference was found between the four groups in intrinsic motivation or performance. For extrinsic regulations, the results showed that first-person self-talk led to higher external regulation than non-subject self-talk and the control group. The possible reason for contradictory findings with our hypothesis and implications have been discussed.
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Motivação , Humanos , Masculino , Feminino , Adulto Jovem , Japão , Adulto , Autonomia Pessoal , Povo Asiático/psicologia , Idioma , Análise e Desempenho de Tarefas , Adolescente , População do Leste AsiáticoRESUMO
AIM: To determine the postpartum urinary retention rate and risk factors after delivery using epidural analgesia. METHODS: This single-center retrospective study targeted 341 women who gave birth after at least 37 weeks of gestation from April to August 2021; from this cohort, 208 patients were examined. The postpartum urinary retention rate was compared between the no epidural analgesia group (n = 107) and epidural analgesia group (n = 101). Subsequently, risk factors for postpartum urinary retention were investigated in the epidural analgesia group. RESULTS: After adjustment by propensity score matching for age, body mass index, being primiparous, and labor induction as covariates, the analysis of the incidence of postpartum urinary retention revealed that the epidural analgesia group exhibited a significantly higher postpartum urinary retention rate than the no epidural analgesia group (30% vs. 11%, p = 0.02). The investigation results regarding risk factors for postpartum urinary retention in the epidural analgesia group obtained through a univariate analysis showed that being primiparous and having a prolonged second stage of labor were significantly correlated with postpartum urinary retention. Multivariate analysis indicated that a prolonged second stage of labor was an independent risk factor for postpartum urinary retention (p = 0.03; odds ratio: 3.18; 95% confidence interval: 1.08-9.77). All patients recovered from postpartum urinary retention by day 4. CONCLUSIONS: The postpartum urinary retention rate after delivery using epidural analgesia was 25.7%. In the case of epidural analgesia deliveries, a prolonged second stage of labor was an independent risk factor for postpartum urinary retention.
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Analgesia Epidural , Retenção Urinária , Humanos , Feminino , Gravidez , Analgesia Epidural/efeitos adversos , Segunda Fase do Trabalho de Parto , Estudos Retrospectivos , Retenção Urinária/epidemiologia , Retenção Urinária/etiologia , Período Pós-Parto , Fatores de RiscoRESUMO
No epidemiological studies have examined the health effects of daily bathing in radon hot springs. In this cross-sectional study, we investigated the associations between radon hot spring bathing and health conditions. The target population was 5,250 adults ≥ 20 years old in the town of Misasa, Japan. We collected information about the participants' bathing habits and alleviation of a variety of disease symptoms, and their self-rated health (SRH). Unadjusted and adjusted odds ratios (ORs) and 95% confidence intervals (CI) were calculated. In both the adjusted and unadjusted models of hypertension, significant associations between the > 1×/week hot spring bathing and the alleviation of hypertension symptoms were observed compared to the group whose hot spring bathing was <1×/week: adjusted model, OR 5.40 (95%CI: 1.98-14.74); unadjusted model, 3.67 (1.50-8.99) and for gastroenteritis: adjusted model, 9.18 (1.15-72.96); unadjusted model, 7.62 (1.59-36.49). Compared to the no-bathing group, higher SRH was significantly associated with both bathing < 1×/week: unadjusted model, 2.27 (1.53-3.37) and > 1×/week: adjusted model, 1.91 (1.15-3.19). These findings suggest that bathing in radon hot springs is associated with higher SRH and the alleviation of hypertension and gastroenteritis.
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Autoavaliação Diagnóstica , Gastroenterite , Fontes Termais , Hipertensão , Radônio , Radônio/uso terapêutico , Banhos , Japão , Humanos , Estudos Transversais , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Hipertensão/terapia , Gastroenterite/terapiaRESUMO
The liver's susceptibility to oxidative stress after a combination of forced swim test (FST) and low-dose-rate γ-irradiation has been observed. Therefore, this study aims to clarify the effects of low-dose (0.1 and 0.5 Gy)/high-dose-rate (1.2 Gy/min) irradiation on combined oxidative stressors-liver damage associated with FST and alcohol administration. In addition, the effects of similar irradiation on FST-induced immobility, which induces psychomotor retardation, and antioxidative effects on the brain, lungs, liver and kidneys were investigated, and the results were compared with those of a similar previous study that utilized low-dose-rate irradiation. Low-dose/high-dose-rate (especially 0.5 Gy) irradiation temporarily worsened liver antioxidant function and hepatic function with FST- and alcohol administration-related oxidative damage; however, the damages improved soon after. In addition, the increase in total glutathione content in the liver contributed to the early improvement of hepatic functions. However, pre-irradiation did not suppress immobility during the FST. The results also suggested that the effects of low-dose/high-dose-rate irradiation on the antioxidant functions of each organ after the FST were different from those of low-dose/low-dose-rate irradiation. Overall, this study provides further insights into the effects of low-dose irradiation on exposure to a combination of different oxidative stressors. It will also contribute to the elucidation of dose rate effects on oxidative stress in the low-dose irradiation range.
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Antioxidantes , Estresse Oxidativo , Animais , Camundongos , Álcoois/toxicidade , Antioxidantes/metabolismo , Raios gama , Glutationa , Fígado/efeitos da radiação , Estresse Oxidativo/efeitos da radiaçãoRESUMO
Environmental factors affect the growth of microorganisms and therefore alter the composition of microbiota. Correlative analysis of the relationship between metagenomic composition and the environmental gradient can help elucidate key environmental factors and establishment principles for microbial communities. However, a reasonable method to quantitatively compare whole metagenomic data and identify the primary environmental factors for the establishment of microbiota has not been reported so far. In this study, we developed a method to compare whole proteomes deduced from metagenomic shotgun sequencing data, and quantitatively display their phylogenetic relationships as metagenomic trees. We called this method Metagenomic Phylogeny by Average Sequence Similarity (MPASS). We also compared one of the metagenomic trees with dendrograms of environmental factors using a comparison tool for phylogenetic trees. The MPASS method correctly constructed metagenomic trees of simulated metagenomes and soil and water samples. The topology of the metagenomic tree of samples from the Kirishima hot springs area in Japan was highly similarity to that of the dendrograms based on previously reported environmental factors for this area. The topology of the metagenomic tree also reflected the dynamics of microbiota at the taxonomic and functional levels. Our results strongly suggest that MPASS can successfully classify metagenomic shotgun sequencing data based on the similarity of whole protein-coding sequences, and will be useful for the identification of principal environmental factors for the establishment of microbial communities. Custom Perl script for the MPASS pipeline is available at https://github.com/s0sat/MPASS.
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Metagenoma , Microbiota , Filogenia , Microbiota/genética , Japão , Metagenômica/métodosRESUMO
Most studies on autonomy support and controlling parenting rely on children's perceptions, despite the limitations of this approach. This study investigated congruency between autonomy support and controlling parenting reported by mothers and adolescents and their association with adolescents' depressive symptoms via basic psychological needs satisfaction. Participants included 408 Japanese mother-adolescent (Mage = 13.73, SD = 0.90, 52% female) pairs who completed a questionnaire at two time points four months apart. Results demonstrated low to moderate levels of mother-adolescent agreement. Cross-lagged regression models revealed that mothers' reported autonomy support positively predicted adolescents' basic psychological needs satisfactions, which was negatively associated with depressive symptoms. The independent roles of parenting reported by mothers and adolescents for adolescents' well-being were discussed.
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Relações Mãe-Filho , Poder Familiar , Criança , Humanos , Feminino , Adolescente , Masculino , Poder Familiar/psicologia , Relações Mãe-Filho/psicologia , Depressão/psicologia , Autonomia Pessoal , Mães/psicologiaRESUMO
The pathways for synthesizing tetrapyrroles, including heme and chlorophyll, are well-conserved among organisms, despite the divergence of several enzymes in these pathways. Protoporphyrinogen IX oxidase (PPOX), which catalyzes the last common step of the heme and chlorophyll biosynthesis pathways, is encoded by three phylogenetically-unrelated genes, hemY, hemG and hemJ. All three types of homologues are present in the cyanobacterial phylum, showing a mosaic phylogenetic distribution. Moreover, a few cyanobacteria appear to contain two types of PPOX homologues. Among the three types of cyanobacterial PPOX homologues, only a hemJ homologue has been experimentally verified for its functionality. An objective of this study is to provide experimental evidence for the functionality of the cyanobacterial PPOX homologues by using two heterologous complementation systems. First, we introduced hemY and hemJ homologues from Gloeobacter violaceus PCC7421, hemY homologue from Trichodesmium erythraeum, and hemG homologue from Prochlorococcus marinus MIT9515 into a ΔhemG strain of E. coli. hemY homologues from G. violaceus and T. erythraeum, and the hemG homologue of P. marinus complimented the E. coli strain. Subsequently, we attempted to replace the endogenous hemJ gene of the cyanobacterium Synechocystis sp. PCC6803 with the four PPOX homologues mentioned above. Except for hemG from P. marinus, the other PPOX homologues substituted the function of hemJ in Synechocystis. These results show that all four homologues encode functional PPOX. The transformation of Synechocystis with G. violaceus hemY homologue rendered the cells sensitive to an inhibitor of the HemY-type PPOX, acifluorfen, indicating that the hemY homologue is sensitive to this inhibitor, while the wild-type G. violaceus was tolerant to it, most likely due to the presence of HemJ protein. These results provide an additional level of evidence that G. violaceus contains two types of functional PPOX.
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Cianobactérias , Escherichia coli , Protoporfirinogênio Oxidase/genética , Protoporfirinogênio Oxidase/metabolismo , Escherichia coli/genética , Filogenia , Cianobactérias/genética , Heme/metabolismo , Clorofila/metabolismoRESUMO
Jatropha curcas is a drought-tolerant plant that maintains its photosynthetic pigments under prolonged drought, and quickly regains its photosynthetic capacity when water is available. It has been reported that drought stress leads to increased thermal dissipation in PSII, but that of PSI has been barely investigated, perhaps due to technical limitations in measuring the PSI absolute quantum yield. In this study, we combined biochemical analysis and spectroscopic measurements using an integrating sphere, and verified that the quantum yields of both photosystems are temporarily down-regulated under drought. We found that the decrease in the quantum yield of PSII was accompanied by a decrease in the core complexes of PSII while light-harvesting complexes are maintained under drought. In addition, in drought-treated plants, we observed a decrease in the absolute quantum yield of PSI as compared with the well-watered control, while the amount of PSI did not change, indicating that non-photochemical quenching occurs in PSI. The down-regulation of both photosystems was quickly lifted in a few days upon re-watering. Our results indicate, that in J. curcas under drought, the down-regulation of both PSII and PSI quantum yield protects the photosynthetic machinery from uncontrolled photodamage.
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Jatropha , Complexo de Proteína do Fotossistema I , Complexo de Proteína do Fotossistema I/metabolismo , Jatropha/metabolismo , Transporte de Elétrons/fisiologia , Secas , Regulação para Baixo , Folhas de Planta/metabolismo , Fotossíntese/fisiologia , Água/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , ClorofilaRESUMO
A large body of research has shown that parents play a vital role in the development of adolescents' depression. However, previous research has overlooked the effects of a potentially critical factor, namely, parental perceptions, and beliefs about adolescents' depression. The present study examined whether parental perceptions of an adolescent's depressive symptoms predict longitudinal changes in adolescents' symptoms (i.e., the parental perception effect). The longitudinal relationship between adolescents' depressive symptoms and parental perceptions of the adolescents' symptoms was analyzed in three independent groups of parent-adolescent pairs (in total N = 1,228). Parental perception and monitoring effects were found in Studies 1B and 2 only in the depressive mood subscale. While a decreased enjoyment subscale showed a perception effect in Study 1A, we obtained null results from other studies. We synthesized the results by applying meta-analytic structural equation modeling to obtain a more robust estimate. The analysis qualified both perception and monitoring effects in both subscales. Our results suggest that when parents believe that their adolescent child is depressed, adolescents are cognitively biased by their parental perceptions over time, resulting in more severe depressive symptoms. (PsycInfo Database Record (c) 2023 APA, all rights reserved).
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Comportamento do Adolescente , Depressão , Criança , Humanos , Adolescente , Depressão/diagnóstico , Relações Pais-Filho , Pais , PercepçãoRESUMO
Aim: This study aimed to examine the effects of real-time online clinical practice using real-time virtual reality (VR) compared with 2D PC screening on reducing stigma toward dementia, and to investigate the feasibility of online clinical practice using VR. Methods: A single-center, open-label, randomized controlled trial was conducted. Occupational therapy students were randomized to view occupational therapy evaluation screens for dementia patients using a VR headset or 2D monitor. The Attitudes Toward Dementia Scale (ADS), the Dementia Knowledge Scale (DKS), and Images of the Elderly with Dementia (IED) were assessed before and after the intervention. The level of clinical practice satisfaction and the System Usability Scale (SUS) were also assessed. Results: The number of subjects in the intervention and control groups was 10 and 9, respectively. In ADS scores and IED, the main effect was shown in both groups and did not show interactions. In DKS scores, the main effect and interaction were not shown. The VR headset tended to be more usable than the 2D monitor in terms of usability. Satisfaction ratings indicated the characteristics of a realistic clinical experience through real-time VR viewing. Conclusion: Real-time VR and 2D online clinical practice could reduce the stigma toward dementia, but there were no significant differences between the types. The real-time VR experience was more similar to actual clinical practice than a 2D PC screening due to the sense of immersion, but issues in blinding and lack of audio and video quality were found.
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Objective: Maintaining or improving regular walking speed can help extend healthy life expectancy and prevent frailty. The evaluation of walking speed can help individuals meet their daily exercise goals; therefore, it may be beneficial as a public health policy for residents to measure and evaluate their walking speed easily. This study aimed to verify the validity and reliability of a smartphone application for the 10-m walk test, measured in the general population. Methods: The study participants were men (n = 20) and women (n = 20) aged 65-85 years. The 10-m walk tests were performed at the usual walking speed, using the stopwatch function of a newly developed smartphone application. A total of three 10-m walk tests were performed simultaneously with the study participants and professional fitness instructors to evaluate the criterion-related validity and the test-retest reliability. Results: A strong positive correlation was found in the criterion-related validity by the study participants and professional staff for the average of the three trials {r = 0.961 [95% confidence interval (CI) = 0.927, 0.979]}. The results revealed good reliability, with an intraclass correlation coefficient of 0.712 (95% CI = 0.571, 0.823). Conclusion: The smartphone application walking speed measurement method can be widely used by the general public and is useful for health promotion.
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Typical indications for radon therapy include autoimmune diseases such as rheumatoid arthritis (RA). We had previously reported that radon inhalation inhibits Th17 immune responses in RA mice by activating Th1 and Th2 immune responses. However, there are no reports on how radon inhalation affects the activated Th1 and Th17 immune responses, and these findings may be useful for identifying new indications for radon therapy. Therefore, in this study, we investigated the effect of radon inhalation on the lipopolysaccharide (LPS)-induced inflammatory response, focusing on the expression of related cytokines and antioxidant function. Male BALB/c mice were exposed to 2000 Bq/m3 radon for one day. Immediately after radon inhalation, LPS was administered intraperitoneally at 1.0 mg/kg body weight for 4 h. LPS administration increased the levels of Th1- and Th17-prone cytokines, such as interleukin-2, tumor necrosis factor-α, and granulocyte-macrophage colony-stimulating factor, compared to no treatment control (sham). However, these effects were suppressed by radon inhalation. IL-10 levels were significantly increased by LPS administration, with or without radon inhalation, compared to sham. However, radon inhalation did not inhibit oxidative stress induced by LPS administration. These findings suggest that radon inhalation has immunomodulatory but not antioxidative functions in LPS-induced injury.
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Inflamação , Radônio , Administração por Inalação , Animais , Antioxidantes/metabolismo , Imunidade , Inflamação/induzido quimicamente , Inflamação/terapia , Lipopolissacarídeos/metabolismo , Lipopolissacarídeos/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Radônio/uso terapêutico , Fator de Necrose Tumoral alfaRESUMO
Chlorophyll breakdown is observed during senescence. The first step in chlorophyll breakdown is the removal of central Mg by Mg-dechelatase. This reaction is the rate-limiting step in the chlorophyll breakdown pathway. We evaluated the effect of induced chlorophyll breakdown on abscission through the removal of Mg by Mg-dechelatase. Poplar transformants carrying the dexamethasone-inducible Mg-dechelatase gene were prepared using the Arabidopsis Stay-Green1 cDNA. When leaves were treated with dexamethasone, chlorophyll was degraded, photosynthetic capacity was reduced, and an abscission zone was formed, resulting in leaf abscission. In addition, ethylene, which plays an important role during senescence, was produced in this process. Thus, chlorophyll breakdown induces the phenotype in the same way as commonly observed during leaf senescence. This study suggests a physiological role of chlorophyll breakdown in the leaf abscission of deciduous trees. Furthermore, this study shows that the dexamethasone-inducible gene expression system is an available option for deciduous tree studies.
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Arabidopsis , Populus , Arabidopsis/metabolismo , Clorofila/metabolismo , DNA Complementar/metabolismo , DNA Complementar/farmacologia , Dexametasona/metabolismo , Dexametasona/farmacologia , Enzimas , Etilenos/metabolismo , Regulação da Expressão Gênica de Plantas , Folhas de Planta/metabolismo , Populus/genética , Populus/metabolismo , Árvores/metabolismoRESUMO
OBJECTIVE: Cognitive decline is an important and well-documented health problem. The Mini-Cog, a simple cognitive function test, is recommended as a potential early cognitive screening tool. Kanagawa Prefecture, one of the largest prefectures in Japan, developed this self-testing application on a smartphone to enable a large number of residents to assess their cognitive function. This study aimed to verify the validity and reliability of the Mini-Cog. RESULTS: Twenty men and 20 women aged 65-85 years were enrolled. Criterion-related validity of the method tested by professional staff was found to have an acceptable positive association. The test-retest reliability was lower than the clinically expected intraclass correlation coefficient value because of the inclusion of learning and order effects. If the Mini-Cog score of this application is low, the system is equipped with a function that advises the users on preventing cognitive decline, directing them to the appropriate services, and recommending visits to a medical institution. Therefore, the system can be used continuously as a tool for health behaviors and promotions.
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Smartphone , Feminino , Humanos , Japão , Masculino , Testes de Estado Mental e Demência , Testes Neuropsicológicos , Reprodutibilidade dos TestesRESUMO
This study examined whether engaging in physical exercise during a university class would have beneficial effect on students' learning motivation. One hundred and forty-nine participants took part in a psychology class over nine weeks (one lesson per week); for each lesson, participants engaged in a three-minute physical activity (low-intensity aerobic exercise) or control activity (watching a video), about 20 min after the lesson started. Participants reported higher vigour and lower fatigue during the class when they exercised than when they engaged in control activities. These findings suggest the utility of incorporating a short exercise activity in university settings to enhance students' classroom motivation.
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The assembly process of photosystem II (PSII) requires several auxiliary proteins to form assembly intermediates. In plants, early assembly intermediates comprise D1 and D2 subunits of PSII together with a few auxiliary proteins including at least ONE-HELIX PROTEIN1 (OHP1), OHP2, and HIGH-CHLOROPHYLL FLUORESCENCE 244 (HCF244) proteins. Herein, we report the basic characterization of the assembling intermediates, which we purified from Arabidopsis transgenic plants overexpressing a tagged OHP1 protein and named the OHP1 complexes. We analyzed two major forms of OHP1 complexes by mass spectrometry, which revealed that the complexes consist of OHP1, OHP2, and HCF244 in addition to the PSII subunits D1, D2, and cytochrome b559. Analysis of chlorophyll fluorescence showed that a major form of the complex binds chlorophyll a and carotenoids and performs quenching with a time constant of 420 ps. To identify the localization of the auxiliary proteins, we solubilized thylakoid membranes using a digitonin derivative, glycodiosgenin, and separated them into three fractions by ultracentrifugation, and detected these proteins in the loose pellet containing the stroma lamellae and the grana margins together with two chlorophyll biosynthesis enzymes. The results indicated that chlorophyll biosynthesis and assembly may take place in the same compartments of thylakoid membranes. Inducible suppression of the OHP2 mRNA substantially decreased the OHP2 protein in mature Arabidopsis leaves without a significant reduction in the maximum quantum yield of PSII under low-light conditions, but it compromised the yields under high-light conditions. This implies that the auxiliary protein is required for acclimation to high-light conditions.
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Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Clorofila/metabolismo , Clorofila A/metabolismo , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Tilacoides/metabolismoRESUMO
The Mg-dechelatase enzyme encoded by the Stay-Green (SGR) gene catalyzes Mg2+ dechelation from chlorophyll a. This reaction is the first committed step of chlorophyll degradation pathway in plants and is thus indispensable for the process of leaf senescence. There is no structural information available for this or its related enzymes. This study aims to provide insights into the structure and reaction mechanism of the enzyme through biochemical and computational analysis of an SGR homolog from the Chloroflexi Anaerolineae (AbSGR-h). Recombinant AbSGR-h with its intact sequence and those with mutations were overexpressed in Escherichia coli and their Mg-dechelatase activity were compared. Two aspartates - D34 and D62 were found to be essential for catalysis, while R26, Y28, T29 and D114 were responsible for structural maintenance. Gel filtration analysis of the recombinant AbSGR-h indicates that it forms a homo-oligomer. The three-dimensional structure of AbSGR-h was predicted by a deep learning-based method, which was evaluated by protein structure quality evaluation programs while structural stability of wild-type and mutant forms were investigated through molecular dynamics simulations. Furthermore, in concordance with the results of enzyme assay, molecular docking concluded the significance of D34 in ligand interaction. By combining biochemical analysis and computational prediction, this study unveils the detailed structural characteristics of the enzyme, including the probable pocket of interaction and the residues of structural and functional importance. It also serves as a basis for further studies on Mg-dechelatase such as elucidation of its reaction mechanism or inhibitor screening.