Changes in vestibular-related responses to combined noisy galvanic vestibular stimulation and cerebellar transcranial direct current stimulation.

Vestibular nuclei and cerebellar function comprise vestibular neural networks that control vestibular-related responses. However, the vestibular-related responses to simultaneous stimulation of these regions are unclear. This study aimed to examine whether the combination of noisy galvanic vestibular stimulation (nGVS) and cerebellar transcranial direct current stimulation (ctDCS) using a complex transcranial electrical stimulation device alters vestibular-dominant standing stability and vestibulo-ocular reflex (VOR) function. The center of foot pressure (COP) sway and VOR of participants (28 healthy, young adults) were assessed under four conditions of transcranial electrical stimulation using nGVS and ctDCS. The COP was calculated with the participant standing on a soft-foam surface with eyes closed using a force plate to evaluate body sway. VOR measurements were collected via passive head movements and fixation on a target projected onto the front wall using a video head impulse test (vHIT). VOR gain was calculated in six directions using a semicircular canal structure based on the ratio of eye movement to head movement. The nGVS + ctDCS and nGVS + sham ctDCS conditions decreased COP sway compared to the sham nGVS + ctDCS and sham nGVS + sham ctDCS conditions. No significant differences were observed in the main effect of stimulation or the interaction of stimulation and direction on the vHIT parameters. The results of this study suggest that postural stability may be independently affected by nGVS. Our findings contribute to the basic neurological foundation for the clinical application of neurorehabilitation using transcranial electrical stimulation of the vestibular system.

Intravenous immunoglobulin treatment for obstetric antiphospholipid syndrome refractory to conventional therapy: A single-arm, open-labelled multicentre clinical trial.

OBJECTIVES: The objective of the study was to compare the efficacy of intravenous immunoglobulin (IVIG) therapy for obstetric antiphospholipid syndrome (APS) refractory to conventional treatment. METHODS: We conducted a single-arm, open-label multicentre clinical intervention trial. The enrolled criteria were patients with refractory APS who had a history of still or premature birth before 30 weeks of gestational age, even though they had been treated with conventional treatment, i.e. heparin and low-dose aspirin. After confirming the foetal heartbeats, a single course of IVIG (0.4 g/kg body weight daily for 5 days) was added to conventional treatment. The primary outcome was a live birth ratio of >30 weeks of gestational period, and the secondary outcome included improving pregnancy outcomes compared to previous pregnancy. RESULTS: Twenty-five per cent of patients (2 of 8 cases) achieved a live birth after the 30th week of pregnancy by IVIG-only add-on treatment, which is the same prevalence as the historical control. However, by adding other second-line therapy to IVIG and conventional treatment, further three patients (37.5%) achieved improvements in pregnancy outcome compared to previous treatments. In total, five patients (62.5%) were able to achieve preferable pregnancy outcomes through combination treatment including IVIG. CONCLUSIONS: This clinical trial could not demonstrate the efficacy of IVIG-only add-on therapy at improving the pregnancy outcomes of patients with obstetric APS refractory to conventional treatment. However, the combination of IVIG with rituximab or statins adding to conventional treatment improved pregnancy outcomes and resulted in more live births. Further studies are needed to investigate the efficacy of multi-targeted therapy to treat obstetric refractory APS.

Development of quality indicators for pregnancy and childbirth in patients with systemic lupus erythematosus.

OBJECTIVES: A quality indicator for the treatment of systemic lupus erythematosus during pregnancy and childbirth that is useful for sharing standard treatment policies has not yet been developed. This study aimed to develop a quality indicator for systemic lupus erythematosus associated with pregnancy and childbirth. METHODS: To identify candidate quality indicators, we conducted a systematic literature review on the development of quality indicators for systemic lupus erythematosus related to pregnancy and childbirth and on clinical practice guidelines. Candidate quality indicator items were extracted from the final selected articles, and a first evaluation, panel meeting, and second evaluation were conducted to determine whether the candidate items were appropriate as quality indicators. Items for which all panel members reached a consensus were designated pregnancy and childbirth-related systemic lupus erythematosus quality indicators. RESULTS: Four articles on systemic lupus erythematosus-quality indicator development and 28 practice guidelines were listed through abstract/text screening. Based on these studies, 52 candidate quality indicators were extracted that were limited to items related to pregnancy and childbirth, and 41 items were selected on which all panel members agreed. CONCLUSION: We developed pregnancy-related systemic lupus erythematosus quality indicators using the RAND/UCLA method and selected 41 items, which could be used clinically.

Influence of blood lactate variations and passive exercise on cardiac responses.

[Purpose] This study aimed to investigate cardiovascular responses, including heart rate (HR) and heart rate variability (HRV), to various hyperlactatemia-passive exercise interactions. [Participants and Methods] Nine healthy male participants performed upper limb passive cycling movement, and their HR and HRV were assessed while their blood lactate levels were manipulated by sustained handgrip exercise at control, 15% maximum voluntary contraction (MVC), and 30% MVC, followed by postexercise circulatory occlusion. [Results] HR and root mean squared standard difference (rMSSD) of HRV response remained constant at all blood lactate levels during passive exercise (HR: control, 75.8 ± 3.4 bpm; 15% MVC, 76.9 ± 2.7 bpm; and 30% MVC, 77.0 ± 3.7 bpm; rMSSD: control, 33.2 ± 6.9 ms; 15% MVC, 36.3 ± 7.3 ms; and 30% MVC, 37.3 ± 8.9 ms). [Conclusion] Manipulating metaboreflex activation did not significantly alter HR or HRV during passive exercise. These results suggest that, in healthy participants, the interactions between mechanical and metabolic stimuli do not affect HR and HRV responses, implying that passive exercise may be safely implemented.

Activation of neurons and satellite glial cells in the DRG produces morphine-induced hyperalgesia.

Activation of neurons and glial cells in the dorsal root ganglion is one of the key mechanisms for the development of hyperalgesia. The aim of the present study was to examine the role of neuroglial activity in the development of opioid-induced hyperalgesia. Male rats were treated with morphine daily for 3 days. The resultant phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 in the dorsal root ganglion was analyzed by immunohistochemistry and Western blotting. Pain hypersensitivity was analyzed using behavioral studies. The amount of cytokine expression in the dorsal root ganglion was also analyzed. Repeated morphine treatment induced hyperalgesia and marked induction of phosphorylated ERK1/2 in the neurons and satellite glial cells on day 3. An opioid receptor antagonist, toll like receptor-4 inhibitor, MAP/ERK kinase (MEK) inhibitor and gap junction inhibitor inhibited morphine-induced hyperalgesia and ERK1/2 phosphorylation. Morphine treatment induced alteration of cytokine expression, which was inhibited by the opioid receptor antagonist, toll like receptor-4 inhibitor, MEK inhibitor and gap junction inhibitor. Dexamethasone inhibited morphine-induced hyperalgesia and ERK1/2 phosphorylation after morphine treatment. The peripherally restricted opioid receptor antagonist, methylnaltrexone, inhibited hyperalgesia and ERK1/2 phosphorylation. Morphine activates ERK1/2 in neurons and satellite glial cells in the dorsal root ganglion via the opioid receptor and toll like receptor-4. ERK1/2 phosphorylation is gap junction-dependent and is associated with the alteration of cytokine expression. Inhibition of neuroinflammation by activation of neurons and glia might be a promising target to prevent opioid-induced hyperalgesia.

Near-isogenic lines for resistance to brown planthopper with the genetic background of Indica Group elite rice (Oryza sativa L.) variety 'IR64'.

The brown planthopper (BPH), Nilaparvata lugens Stål, is an insect pest that severely damages rice (Oryza sativa L.) in Asia, causing huge yield loss. Use of resistant variety is a cost-effective and eco-friendly strategy for maintaining BPH populations below the economic injury level. However, current BPH populations have been changed to virulence against resistant varieties. In this study, to estimate effective combinations among eight BPH resistance genes (BPH32, BPH17-ptb, BPH20, BPH17, BPH3, BPH25, BPH26 and qBPH6), eight near-isogenic lines with the genetic background of an Indica Group rice variety 'IR64' (IR64-NIL) were developed using marker-assisted selection. The genome recoveries of these NILs ranged from 89.3% to 98.8% and agronomic traits of them were similar to those of 'IR64'. In modified seed box screening test, resistance level of IR64-NILs was higher than that of 'IR64'. In antibiosis test, high adult mortalities of BPH (from 56.0% to 97.0%) were observed among NILs, in comparison with that of 'IR64'. Among IR64-NILs, the line carrying BPH17 showed the highest resistance level at all tests. Thus, these IR64-NILs with multiple BPH resistance genes could be valuable breeding lines for enhancing resistance levels by gene pyramiding and multiline variety.

Development of pyramided lines carrying brown planthopper resistance genes in the genetic background of Indica Group rice (Oryza sativa L.) variety 'IR64'.

The development of resistant rice (Oryza sativa L.) varieties is a key strategy for the eco-friendly control of brown planthopper (BPH: Nilaparvata lugens Stål). However, BPH outbreaks occur frequently owing to the evolution of virulent strains in the field and the rapid breakdown of monogenic resistance to BPH. Therefore, to enhance BPH resistance and gauge the effectiveness of gene pyramiding against strongly virulent BPH, we developed pyramided lines (PYLs) in the genetic background of 'IR64' carrying BPH resistance genes. We developed six IR64-PYLs (BPH3 + BPH17, BPH32 + BPH17, BPH32 + BPH20, BPH3 + BPH17-ptb, BPH20 + BPH3, and BPH17-ptb + BPH32) through marker-assisted selection. To assess the resistance of the IR64-PYLs, we conducted antibiosis test, honeydew test, and modified seedbox screening test (MSST) using strongly virulent BPH populations. The level of BPH resistance increased in all six IR64-PYLs compared to both 'IR64' and the corresponding NILs in MSST. Among them, IR64-BPH3 + BPH17 and IR64-BPH32 + BPH17 exhibited the highest resistance to BPH. However, the resistance level of most IR64-PYLs was not significantly higher than that of the corresponding NILs in antibiosis test. Thus, these PYLs could serve as a valuable resource for breeding programs aimed at improving resistance to virulent strains of BPH and enhancing their durability.

Development and characterization of near-isogenic lines for brown planthopper resistance genes in the genetic background of japonica rice 'Sagabiyori'.

The brown planthopper (BPH: Nilaparvata lugens Stål) is one of the most destructive insects in rice production. The use of host plant resistance has potential to reduce damage caused by BPH. The heat tolerance japonica rice 'Sagabiyori', with superior grain quality and high soluble starch in the stem, is highly susceptible to damage by BPH. Here, to enhance its BPH resistance, we developed seven near-isogenic lines (NILs) carrying BPH2, BPH17-ptb, BPH32, BPH3, BPH17, BPH20, and BPH21 through marker-assisted selection and evaluated resistance to two BPH populations. Most lines were more resistant to the Hadano-1966 BPH population than Sagabiyori but were less effective against the highly virulent Koshi-2013 population. Nevertheless, in antixenosis tests, Koshi-2013 settled less on all NILs than on Sagabiyori. In addition, adult mortality and the percentage of fresh weight loss of lines carrying BPH17 and BPH3 indicated that these lines have higher resistance to Koshi-2013 than Sagabiyori. Current study revealed that BPH resistance of Sagabiyori became stronger by transferring BPH3 and BPH17 genes. Thus, BPH3 and BPH17 might be valuable for breeding programs to enhance BPH resistance of high grain quality rice varieties with heat tolerance.

Identification and characterization of stable QTLs for vascular bundle number at the panicle neck in rice (Oryza sativa L.).

A large vascular bundle number (VBN) in the panicle neck in rice (Oryza sativa L.) is related to the ability to transport assimilates from stem and leaf to reproductive organs during seed maturation. Several quantitative trait loci (QTLs) for VBN have been identified by using segregating populations derived from a cross between indica and japonica rice cultivars. However, the detailed location, effect, and interaction of QTLs for VBN were not understood well. Here, to elucidate the genetic basis of VBN, we identified three stable QTLs for VBN-qVBN5, qVBN6 and qVBN11-by using 71 recombinant inbred lines derived from a cross between indica 'IR24' and japonica 'Asominori'. We confirmed their positions and characterized their effects by using chromosome segment substitution lines (CSSLs) with an 'IR24' genetic background. qVBN6 had the most substantial effect on VBN, followed by qVBN11 and qVBN5. We developed pyramided lines carrying two QTLs for VBN to estimate their interaction. The combination of qVBN6 and qVBN11 accumulated VBN negatively in the pyramided lines owing to the independent actions of each QTL. The QTLs detected for VBN will enhance our understanding of genetic mechanisms of VBN and can be used in rice breeding.

Mapping stress inside living cells by atomic force microscopy in response to environmental stimuli.

The response of cells to environmental stimuli, under either physiological or pathological conditions, plays a key role in determining cell fate toward either adaptive survival or controlled death. The efficiency of such a feedback mechanism is closely related to the most challenging human diseases, including cancer. Since cellular responses are implemented through physical forces exerted on intracellular components, more detailed knowledge of force distribution through modern imaging techniques is needed to ensure a mechanistic understanding of these forces. In this work, we mapped these intracellular forces at a whole-cell scale and with submicron resolution to correlate intracellular force distribution to the cytoskeletal structures. Furthermore, we visualized dynamic mechanical responses of the cells adapting to environmental modulations in situ. Such task was achieved by using an informatics-assisted atomic force microscope (AFM) indentation technique where a key step was Markov-chain Monte Carlo optimization to search for both the models used to fit indentation force-displacement curves and probe geometry descriptors. We demonstrated force dynamics within cytoskeleton, as well as nucleoskeleton in living cells which were subjected to mechanical state modulation: myosin motor inhibition, micro-compression stimulation and geometrical confinement manipulation. Our results highlight the alteration in the intracellular prestress to attenuate environmental stimuli; to involve in cellular survival against mechanical signal-initiated death during cancer growth and metastasis; and to initiate cell migration.

Effectiveness of knee pad as an additional device for wheelchairs in improving upper-limb dexterity during seated tasks: a pilot study.

[Purpose] This study aimed to examine how supporting the knee from the front with a knee pad affected upper-limb dexterity while sitting. [Participants and Methods] A total of 14 healthy adult males were included in the study. As a measure of upper-limb dexterity, the number of pins was counted when the Purdue pegboard test was performed for 60 seconds. In addition, the ease of task performance was assessed using the visual analogue scale. There were two experimental conditions, with and without knee pad. The paired t-test was used to detect differences between the two conditions. A p-value of 0.05 was considered statistically significant. [Results] The Purdue pegboard test was 29.4 ± 2.5 and 27.9 ± 3.6 pins with and without knee pad, respectively. The VAS was 76.1 ± 10.3 and 62.9 ± 14.1 with and without knee pad, respectively. Both measured values were significantly higher with knee pad than without. [Conclusion] Supporting the knees from the front with knee pad improves upper-limb functionality while sitting, making it easier to perform seated tasks.

Congenital cytomegalovirus infection after maternal primary infection in a patient with systemic lupus erythematosus: A case report and literature review.

BACKGROUND: Management of infectious complications in pregnant women receiving immunosuppressive therapy for systemic lupus erythematosus (SLE) is important. Maternal infection with cytomegalovirus (CMV) often causes congenital CMV infection in the foetus. Thus far, there are only few reports on congenital CMV infection after maternal reactivation in patients with SLE. We report the first case of congenital CMV infection after maternal primary infection in a patient with SLE. CASE PRESENTATION: A 19-year-old Japanese primigravida with SLE received treatment with prednisolone 3 mg/day and azathioprine 75 mg/day at conception. At 7 weeks of gestation, she suddenly developed fever and had decreased white blood cell and platelet counts and elevated aspartate aminotransferase and alanine aminotransferase levels. These clinical findings led to a diagnosis of SLE exacerbation. The prednisolone dose was increased to 15 mg/day, and hydroxychloroquine (200 mg/day) was administered. Consequently, all clinical findings normalised at 12 weeks. At 19 weeks, foetal ultrasound findings revealed oligohydramnios, brain hypoplasia, ventriculomegaly and hyperechogenic bowel. Maternal serological test results indicated increased CMV-specific IgG and IgM levels, low IgG avidity (26%), and positive CMV antigenemia. The foetus was diagnosed with symptomatic congenital CMV infection transmitted from the maternal primary infection. After counselling about the severe prognosis of the foetus, the mother decided to terminate her pregnancy and underwent artificial abortion at 21 weeks. DISCUSSION: The foetus of a mother with SLE who is receiving immunosuppressive therapy may be at increased risk of transmission and aggravation of congenital CMV infection; thus, preventive management and screening for congenital CMV infection during pregnancy are recommended for such patients. Maternal CMV infection shows clinical findings similar to those of SLE exacerbation, and careful differential diagnosis by maternal serological evaluation and foetal ultrasound scans is required.

Mechanomics Biomarker for Cancer Cells Unidentifiable through Morphology and Elastic Modulus.

Cellular mechanical properties are potential cancer biomarkers used for objective cytology to replace the current subjective method relying on cytomorphology. However, heterogeneity among intra/intercellular mechanics and the interplay between cytoskeletal prestress and elastic modulus obscured the difference detectable between malignant and benign cells. In this work, we collected high density nanoscale prestress and elastic modulus data from a single cell by AFM indentation to generate a cellular mechanome. Such high dimensional mechanome data was used to train a malignancy classifier through machine learning. The classifier was tested on 340 single cells of various origins, malignancy, and degrees of similarity in morphology and elastic modulus. The classifier showed instrument-independent robustness and classification accuracy of 89% with an AUC-ROC value of 93%. A signal-to-noise ratio 8 times that of the human-cytologist-based morphological method was also demonstrated, in differentiating precancerous hyperplasia cells from normal cells derived from the same lung cancer patient.

Correction: Speedy one-pot electrochemical synthesis of giant octahedrons from in situ generated pyrrolidinyl PAMAM dendrimer.

Correction for 'Speedy one-pot electrochemical synthesis of giant octahedrons from in situ generated pyrrolidinyl PAMAM dendrimer' by Anup Singhania et al., Soft Matter, 2020, 16, 9140-9146, DOI: 10.1039/D0SM00819B.

Possible prevention of post-partum depression by intake of omega-3 polyunsaturated fatty acids and its relationship with interleukin 6.

AIM: This study examined whether the intake of omega-3 polyunsaturated fatty acids (PUFA) prevented post-partum depression and if interleukin 6 (IL-6) was involved in this effect. We hypothesized that omega-3 supplementation has a protective effect against post-partum depression. METHODS: We measured eicosapentaenoic acid (EPA), the arachidonic acid (AA)/EPA ratio, and IL-6 in 80 singleton pregnant women during the first and second trimesters, and post-partum. The women also completed a dietary questionnaire, and post-partum depression was measured using the Edinburgh Postnatal Depression Scale (EPDS). We examined the correlations between the frequency of eating fish and EPA, the AA/EPA ratio and IL-6 in the first and second trimesters, and post-partum. We also investigated the correlation between the EPDS and the EPA, the AA/EPA ratio and IL-6. RESULTS: The frequency of eating fish was significantly correlated with EPA in the second trimester and post-partum and with the AA/EPA ratio in the second trimester. There was no correlation between IL-6 levels and the frequency of eating fish. Post-partum levels of EPA and the AA/EPA ratio were higher in the EPDS >7 group than in the EPDS ≤7 group. In the second trimester, a higher AA/EPA ratio was associated with EPDS >7. IL-6 levels did not differ between the two groups. CONCLUSION: In conclusion, a low dietary intake of omega-3 PUFA during pregnancy was correlated with lower EPA levels, which tended to lead to post-partum depression. The relationship between the IL-6 level and the pathogenesis of post-partum depression was unclear from the results of this study.

Substitution mapping and characterization of brown planthopper resistance genes from indica rice variety, 'PTB33' (Oryza sativa L.).

Rice (Oryza sativa L.) yield is severely reduced by the brown planthopper (BPH), Nilaparvata lugens Stål, in Asian countries. Increasing resistance in rice against BPH can mitigate yield loss. Previous reports indicated the presence of three BPH resistance genes, BPH2, BPH17-ptb, and BPH32, in durable resistant indica rice cultivar 'PTB33'. However, several important questions remain unclear; the genetic locations of BPH resistance genes on rice chromosomes and how these genes confer resistance, especially with relationship to three major categories of resistance mechanisms; antibiosis, antixenosis or tolerance. In this study, locations of BPH2, BPH17-ptb, and BPH32 were delimited using chromosome segment substitution lines derived from crosses between 'Taichung 65' and near-isogenic lines for BPH2 (BPH2-NIL), BPH17-ptb (BPH17-ptb-NIL), and BPH32 (BPH32-NIL). BPH2 was delimited as approximately 247.5 kbp between RM28449 and ID-161-2 on chromosome 12. BPH17-ptb and BPH32 were located between RM1305 and RM6156 on chromosome 4 and RM508 and RM19341 on chromosome 6, respectively. The antibiosis, antixenosis, and tolerance were estimated by several tests using BPH2-NIL, BPH17-ptb-NIL, and BPH32-NIL. BPH2 and BPH17-ptb showed resistance to antibiosis and antixenosis, while BPH17-ptb and BPH32 showed tolerance. These results contribute to the development of durable BPH resistance lines using three resistance genes from 'PTB33'.

Development and evaluation of pyramiding lines carrying early or late heading QTLs in the indica rice cultivar 'IR64'.

The heading date is an important trait for determining regional and climatic adaptability in rice. To expand the adaptability of the indica rice cultivar 'IR64', we pyramided multiple early or late heading quantitative trait locus (QTLs) in the 'IR64' genetic background by crossing previously developed near-isogenic lines (NILs) with a single QTL for early or late heading. The effects of pyramiding QTLs were observed in three different climatic zones of the Philippines, Madagascar, and Japan. The early heading pyramiding lines (PYLs) headed 6.2 to 12.8 days earlier than 'IR64' while the late heading PYLs headed 18.8 to 27.1 days later than 'IR64'. The PYLs tended to produce low grain yield compared to 'IR64'. The low yield was not improved by combining SPIKE, which is a QTL that increases the number of spikelets per panicle. Conversely, 'IR64-PYL(7+10)' carrying Hd5 and Hd1 headed earlier, produced more tillers, and more panicles per m2 than 'IR64', and mitigated the yield decrease in early heading. These results suggest that the effects of pyramided QTLs on heading date were consistent across various environments and PYLs could be used to enhance the adaptation of 'IR64' in other rice growing environments.

Radio Waveguide-Double Ratchet Rotors Work in Unison on a Surface to Convert Heat into Power.

Synchronizing thousands of 100% efficient rotors in a macrodevice for harvesting noise is unapprehended. Thermodynamically, realizing a thermal gradient at the atomic scale is critical. Harvesting free thermal energy or noise by resonance has a hidden clause; either externally activating a directed self-powered motion or constructing a nanoscale power supply. To accomplish this, we combined two rotor concepts, Brownian rotor, BR, and power stroke, PS, rotors available in living systems in two planes of a single molecule. Quantum tunneling images reveal how a radio-wave guided synchronization of PS-BR combination tweaks rotational dynamics of a rotor to bypass the necessity of temperature gradient (ΔT). Live imaging of thermal noise movement as electron density between a pair of molecular planes helped in optimizing the rotor design. The rotor's monolayer harvests heat from the liquid's Brownian noise and electromagnetic noise, together delivering a finite, usable power. The chip supplies the power if we wet the surface or shine electric noise.

Simplified disease activity index and clinical disease activity index before and during pregnancy correlate with those at postpartum in patients with rheumatoid arthritis.

OBJECTIVES: We explored rheumatoid arthritis (RA) disease activity before, during, and after pregnancy in patients treated with tight control and investigated the association between disease activity in the postpartum period and those before and during pregnancy. METHODS: We retrospectively reviewed disease activity and medications of 27 patients before pregnancy, at every trimester, and in the postpartum period. RESULTS: Prednisolone was administered to 33% of patients with a median dose of 0 (0-2.5) mg/day and biologic agents was 78% in the third trimester. The median remission rates during all periods were the Disease Activity Score-28-C-reactive Protein assessed with three variables (DAS28-CRP-3) 85%, Simplified Disease Activity Index (SDAI) 55%, and Clinical Disease Activity Index (CDAI) 54%. Although SDAI and CDAI decreased significantly from before pregnancy to the first trimester and increased from the third trimester to the postpartum period, DAS28-CRP-3 did not change during all periods. Although SDAI and CDAI before and during pregnancy were significantly correlated with those in the postpartum period, DAS28-CRP-3 was not. CONCLUSIONS: Tight control before pregnancy suppressed RA disease activity during pregnancy and in the postpartum period. SDAI/CDAI before and during pregnancy were predictive for disease activity in the postpartum period.

The reliability of VO2 kinetics during a 6-minute walking test is influenced by walk speed.

[Purpose] This study aimed to investigate the reliability of time constant measurements of oxygen intake at fast and comfortable speeds during a 6-min waling test. [Participants and Methods] The study included 10 healthy young males who walked at 4.5 km/h and 6.0 km/h twice for 6 min each in speed treadmill. Breath-by-breath gas exchange data were continuously measured and used to calculate the time constant of oxygen uptake. The reproducibility and variability of the variables were verified using the limit of agreement, inter-class correlation coefficient, coefficient of variation, and standard error of measurement. [Results] The limit of agreement was -8.5 to 2.3 s and -3.9 to 2.1 s for speeds 4.5 km/h and 6.0 km/h, respectively. The inter-class correlation coefficient, coefficient of variation, and standard error of measurement of the time constant for both speeds were 0.52 and 0.83, 11.2% and 6.4%, and 5.3 s and 1.8 s, respectively. [Conclusion] The results of this study suggested that the cardiopulmonary response, in terms of oxygen uptake, was more consistent during fast walking than during comfortable walking in a 6-min walking test with constant speed.