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The effect of boron weight percentage in the camphoric carbon target of pulsed laser deposition on the preparation of boron-doped amorphous carbon (a-C:B) films has been studied using standard measurement techniques. XPS results showed the a-C:B films bonding properties almost unchanged at lower Bwt% up to 10 Bwt%, after which it changes with the increase of Bwt%, indicating increasing doping concentration with increase of Bwt% in the target. This phenomenon is further supported by FTIR and Visible-Raman spectroscopy analyses. The variation of bonding and structural properties are also correlated with the optical gap (Eg) and electrical resistivity (ρ) characteristics which are related to successful doping of B for low content of B in the amorphous carbon (a-C) films as the bonding, structural and Eg remain almost unchanged, and the ρ decreased untill the film deposited at 10 Bwt%. Since both the Eg and ρ decrease sharply with higher Bwt%, this phenomenon can be related to the graphitization. [ABSTRACT FROM AUTHOR]

Abstract: Double photoionisation spectra of ethyne and ethyne-d2 have been measured by the TOF–PEPECO technique and by the TPEsCO method with vibrational resolution. With the help of new calculations of the dication structure and Franck–Condon factors we deduce adiabatic double ionisation energies for the first three states of the normal hydrogen isotopomer as 31.74eV (X3Σg-), 32.42 (a1Δg) and 33.07 (b1Σg+). The two techniques give spectra with very different vibrational structure and reasons for the difference are discussed. [Copyright &y& Elsevier]

The effects of boron content in camphoric carbon (CC) and graphite target of pulsed laser deposition (PLD) prepared in vacuum at room temperature on the properties of boron doped amorphous carbon (a-C:B) thin films has been studied. Deposited a-C:B films have been investigated using standard measurement techniques and the effects of B weight percentages (Bwt%) in the target are discussed. The variation of surface morphology, bonding and structural properties, as well as the optical gap (Eg) and electrical resistivity (ρ) of a-C:B films deposited using a CC target are related to the successful doping of B for low B content in the amorphous carbon (a-C) films as the structure and Eg remain almost unchanged, and the ρ decreased for the film deposited using graphite target with B powder up to 10 Bwt%. Since both Eg and ρ decreased sharply with higher Bwt%, this phenomenon may be due to graphitization. For a-C:B films deposited using graphite target with low B content at 1 and 3 Bwt%, as the Eg is observed to increase only slightly when compared with undoped a-C films and with the decrease of ρ, we speculated that the B incorporation induced successful of doping is responsible for the decrease in ρ. [ABSTRACT FROM AUTHOR]

The properties of tetrahedral amorphous carbon (ta-C) films grown by pulsed laser deposition (PLD) using camphoric carbon (CC) target and their respective effects of diamond percentages by weight in the target (Dwt.%) are discussed. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Visible-Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that the Dwt.% noticeably modified the sp3 bonds content and the morphology of the ta-C films. The optical gap (Eg) and electrical resistivity (ρ) increase with Dwt.% up to 1.6 eV and 5.63×107 (Ω cm), respectively, for the ta-C films deposited using target with higher of 50 Dwt.%. We found that the Dwt.% has modified the surface morphological, structural, bonding and physical properties of the camphoric carbon films. [Copyright &y& Elsevier]

Photoelectron-photoion coincidence (PEPICO) spectra at 73.6 nm reveal an interesting fact; from hexafluorobenzene cation the C5F3+ fragment is most abundant whilst from the benzene cation C4H4+ is far more abundant than C5H3+. These contrasting results are connected, as shown by the PEPICO spectra of other fluorinated benzenes, by a regular change of the dominant fragment from C5F3+ to C4H4+ as the number of fluorine atoms decreases. This regularity is consistent with the appearance energies, at QCISD[T] or CBS-QB3 levels, of C5FmH3−m+ in the acetylene-cyclopropene structure and C4FnH4−n+ in the methylene-cyclopropene and/or the vinyl-acetylene structures. The energy-selected PEPICO data further support the theoretical results. [Copyright &y& Elsevier]

OBJECTIVE: To assess energy depletion in skeletal muscle in patients with congestive heart failure by measuring blood purine metabolites during exercise and, at the same time, determine the implications of the ammonia response to exercise in these patients. SETTING: Tottori University Hospital, Yonago, Japan. PATIENTS: 49 heart failure patients (New York Heart Association (NYHA) grades I-III) and 16 normal subjects. MAIN OUTCOME MEASURES: Blood lactate, ammonia, and hypoxanthine levels were measured during exercise with expired gas analysis. RESULTS: In normal exercising subjects as well as in each heart failure subgroup, the ammonia threshold was significantly higher than both the lactate threshold [control: 21.8 (SD 5.3) v 17.4 (3.3) ml/kg/min; NYHA class I: 18.9 (3.8) v 15.5 (2.6); class II: 14.8 (2.5) v 12.7 (2.4); class III: 13.5 (2.6) v 11.8 (2.5)] and the ventilatory threshold (P < 0.01). The difference between the ammonia and lactate thresholds was noted in all normal subjects and in all heart failure patients. The ammonia threshold, however, was significantly lower in heart failure patients than in normal subjects and it decreased with increasing NYHA class (P < 0.01). Maximum ammonia levels were lower in the heart failure group and decreased further with higher NYHA classifications [control: 198 (52) mg/dl; NYHA class I: 170 (74); class II: 134 (58); class III: 72 (15); P < 0.01]. There were significant correlations between maximum ammonia values and maximum lactate, oxygen consumption, and hypoxanthine levels (r = 0.74, 0.48, and 0.87, respectively; P < 0.001). CONCLUSIONS: The ammonia threshold may reflect the onset of ATP depletion in exercising skeletal muscles, as opposed to the onset of anaerobic respiration. It seems therefore that energy depletion in skeletal muscles during exercise occurs after attaining the anaerobic threshold. Both aerobic and anaerobic capacities of skeletal muscle are reduced in patients with congestive heart failure. [ABSTRACT FROM PUBLISHER]

To evaluate purine degradation in patients with congestive heart failure concentrations of serum hypoxanthine, lactate, and noradrenaline were measured before and after submaximal treadmill exercise in 12 patients with chronic congestive heart failure and nine healthy volunteers. In four patients the concentration of hypoxanthine was significantly higher than in the controls or in the remaining eight patients with congestive heart failure. Venous lactate and noradrenaline in the four patients with high concentrations of hypoxanthine were also significantly higher than those in the eight patients with normal concentrations of hypoxanthine. Patients who responded normally were also more likely to have been treated with vasodilators and angiotensin converting enzyme inhibitors. Exercise induced arrhythmias were more common in the patients with high concentrations of hypoxanthine. These results suggest that the excess purine degradation in patients with congestive heart failure might be the result of a "relative" disturbance in the supply of adenosine triphosphate caused by the shift of cellular metabolism from aerobic glycolysis to anaerobic glycolysis during submaximal exercise and that hypoxanthine (a substrate for xanthine oxidase and a source of free radicals) was increased after submaximal exercise in some patients with congestive heart failure. [ABSTRACT FROM PUBLISHER]

Background: Neutron radiation protection factors indicate that the risk of neutron-induced stochastic biological effects is higher compared with other types of ionising radiation, and has strong energy dependence. Recent Monte Carlo studies simulated neutron radiation on a nuclear DNA model and demonstrated that the energy-dependent radiobiological risk of neutrons can be correlated with the induction of DNA damage clusters, particularly those that contain difficult-to-repair double-strand breaks. The main limitation of these studies is that only direct radiation action was investigated. Thus, for a more comprehensive understanding of pre-repair neutron-induced DNA damage, indirect action must be modelled and its impact must be quantified. Methods: An open-source algorithm for indirect action available in the TOPAS-nBio track structure Monte Carlo toolkit was adapted into our group's existing TOPAS and TOPAS-nBio simulation pipeline for neutron and photon radiation. We performed 100 independent simulated irradiations of monoenergetic neutrons from 1 eV to 10 MeV on our existing custom-built nuclear DNA model, and scored various types of DNA damage due to direct and indirect action. The yields of DNA damage were stratified according to the damage-inducing action. For the resulting clusters of DNA damage, we determined the average cluster length and lesion count per cluster. This procedure was also performed for 250-keV x-ray photons that served as our reference radiation. We estimated neutron relative biological effectiveness (RBE) by dividing the neutron-inflicted yield of DNA damage clusters by photon-inflicted counterparts. Finally, we compared our RBE results with established radiation protection factors and previous studies that modelled direct action alone. Results: The inclusion of indirect action increased the yield of DNA damage significantly (the increase varies with damage type). We found that the majority of neutron-induced DNA damage events were isolated simple lesions due to indirect action, while most clustered lesions were hybrid in nature (i.e. contain lesions due to direct and indirect action). As for cluster properties, the inclusion of indirect action increased the average length of clusters by approximately 50% and the number of lesions per cluster by approximately 25%. Our estimated energy-dependent neutron RBE for inducing DNA damage clusters follows similar trends as the established radiation protection factors and the previous direct-action-only estimates, but is lower in magnitude. We found that this lower magnitude is due to the greater impact of indirect action in the yield of photon-induced clustered DNA damage compared with neutron-induced clustered lesions. Conclusion: Indirect action has significant effects on radiation-induced DNA damage clusters in terms of yield, length, and lesion count per cluster, and serves to amplify the effects of direct action. The energy-dependent risk of neutron-induced stochastic effects is likely related to, but not completely explained by, the induction of DNA damage clusters. For a more complete model of neutron RBE, the investigation of factors such as DNA damage repair and non-targeted radiation effects is recommended. [ABSTRACT FROM AUTHOR]

Purpose: Controlled ovarian stimulation (COS) is vital for IVF. We have developed an AI system to support the implementation of COS protocols in our clinical group., Methods: We developed two models as AI algorithms of the AI system. One was the oocyte retrieval decision model, to determine the timing of oocyte retrieval, and the other was the prescription inference model, to provide a prescription similar to that of an expert physician. Data was obtained from IVF treatment records from the In Vitro Fertilization (IVF) management system at the Asada Ladies Clinic, and these models were trained with this data., Results: The oocyte retrieval decision model achieved superior sensitivity and specificity with 0.964 area under the curve (AUC). The prescription inference model achieved an AUC value of 0.948. Four models, namely the hCG prediction model, the hMG prediction model, the Cetrorelix prediction model, and the Estradiol prediction model included in the prescription inference model, achieved AUC values of 0.914, 0.937, 0.966, and 0.976, respectively., Conclusion: The AI algorithm achieved high accuracy and was confirmed to be useful. The AI system has now been implemented as a COS tool in our clinical group for self-funded treatments., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s). Reproductive Medicine and Biology published by John Wiley & Sons Australia, Ltd on behalf of Japan Society for Reproductive Medicine.)

Purpose: In this paper, we described our mathematical model for radiation-induced life shortening in detail and applied the model to the experimental data on mice to investigate the effect of radiation on cancer-related life-shortening., Materials and Methods: Our mathematical model incorporates the following components: (i) occurrence of cancer, (ii) progression of cancer over time, and (iii) death from cancer. We evaluated the progression of cancer over time by analyzing the cancer incidence data and cumulative mortalities data obtained from mice experiments conducted at the Institute for Environmental Sciences (IES)., Results: We analyzed non-irradiated control and 20 mGy/day × 400 days irradiated groups. In the analysis, all malignant neoplasms were lumped together and referred to as 'cancer'. Our analysis showed that the reduction in lifespan (104 days in median) was the result of the early onset of cancer (68 days in median) and the shortening of the cancer progression period (48 days in median)., Conclusions: We described in detail our mathematical model for radiation-induced life-shortening attributed to cancer. We analyzed the mice data obtained from the experiment conducted at the IES using our model. We decomposed radiation-induced life-shortening into the early onset of cancer and the shortening of the cancer progression period.

Purpose: The effect of chronic low dose-rate radiation exposure on cancers was investigated by analyzing the data of mice experiments conducted at the Institute for Environmental Sciences (IES). This analysis focuses on the differences between malignant lymphomas and solid cancers., Materials and Methods: The analysis is conducted based on the mathematical model introduced in our previous work. The model is expanded to analyze malignant lymphomas and solid cancers separately. Using the expanded model, the effect of chronic low dose-rate radiation on malignant lymphomas and solid cancers are discussed based on their occurrences, progressions, and mortalities., Results: Non-irradiated control group and 20 mGy/day × 400 days irradiated groups are analyzed. The analysis showed that radiation exposure shortened mean life expectancy for both malignant lymphomas and solid cancers (shorter by 89.6 days for malignant lymphomas and 149.3 days for solid cancers). For malignant lymphomas, both the occurrence and the progression are affected by radiation exposure. The mean age at which malignant lymphoma developed in mice was shortened by 32.7 days and the mean progression period was shortened by 57.3 days. The occurrence of solid cancer is also affected by radiation exposure, wherein the mean age at which solid cancer develops was shortened by 147.9 days. However, no significant change in progression period of solid cancers was seen in the analysis., Conclusions: The analysis showed that the occurrence and mean lifespan are affected in both malignant lymphomas and solid cancers. The shortening of the progression period is only seen in malignant lymphoma, no significant change was observed in solid cancers.

For regulating the olefin metathesis (OM) activity of the Hoveyda-Grubbs second-generation complex (HG-II), the structural modification of the benzylidene ligand is a useful strategy. This paper reports the effect of a chalcogen atom placed at the end of the benzylidene group on the catalytic properties of HG-II derivatives, using complexes with a thioether or ether component in the benzylidene ligand ( ortho -Me-E-(CH 2 ) 2 O-styrene; E = S, O). Nuclear magnetic resonance and X-ray crystallographic analyses of the complex with a thioether moiety (E = S) proved the ( O , S )-bidentate and trans -dichlorido coordination for the complex. A stoichiometric ligand exchange between HG-II and the benzylidene ligand (E = S) produced the corresponding complex with an 86% yield, confirming higher stability of the complex (E = S) than that of HG-II. Despite the bidentate chelation, the complex (E = S) exhibited OM catalytic activity, indicating the exchangeability of the S -chelating ligand with an olefinic substrate. The green solution color, a characteristic of HG-II derivatives, was retained after the complex (E = S)-mediated OM reactions, indicating high catalyst durability. Conversely, the complex (E = O) rapidly initiated OM reactions; however, it showed low catalyst durability. In the OM reactions conducted in the presence of methanol, the complex (E = S) exhibited higher yields than the complex (E = O) and HG-II: the S -coordination increased the catalyst tolerance to methanol. A coordinative atom (such as sulfur) placed at the terminal of the benzylidene ligand can precisely regulate the reactivity of HG-II derivatives.

The authors performed a combined analysis using the data obtained from continuous low dose rate irradiation experiments on mice conducted at the Institute for Environmental Sciences, namely, cancer incidence data and lifespan data. They estimated the length of cancer progression period, which is difficult to assess experimentally. The combined analysis showed that the mean cancer progression period is 173 d in the control group and 103 d in the irradiated group., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The concept of radiation-induced aging is revisited from the viewpoint of a mathematical model. The effect of radiation on carcinogenesis is treated based on the Armitage-Doll multi-stage theory. The formula obtained for cancer incidence rate indicates that radiation dose can be explained in terms of time. Radiation-induced aging for acute and chronic exposures is described using age-specific cancer incidence rates as a measure of aging. It shows that accelerated aging is related to the dose rate, whereas premature aging is related to the cumulative dose, providing a simple and natural interpretation of radiation-induced aging. The usefulness of this approach is demonstrated by applying the formula to cancer prevalence data from mice chronically exposed to low dose-rate radiation., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Activation of neurohormonal systems contributes to the progression of heart failure (HF). The mechanism(s) whereby these systems become activated is(are) not fully explained. We determined whether vagal cardiopulmonary baroreflex control of renal sympathetic nerve activity is abnormal in dogs with left ventricular (LV) dysfunction in the absence of clinical HF, and the relationship of abnormalities in baroreflexes to the development of the neurohumoral excitatory state., Methods: LV end-systolic and end-diastolic dimensions (echocardiography), arterial baroreflex sensitivity (slope of ΔRR/Δsystolic BP during phenylephrine or nitroglycerin bolus), and neurohumoral profiles (plasma norepinephrine, renin activity, and arginine vasopressin) were measured serially in conscious dogs (n=24) with progressive LV dysfunction due to rapid ventricular pacing. LV dimensions were used to define groups with mild, moderate, and marked LV dilatation (LVD; increase in LV end-diastolic volume <15%, 15-30%, and >30% of control, respectively). Changes in renal nerve activity (RNA) were recorded in response to increases in pulmonary capillary wedge pressure (PCWP) induced by volume infusion in anesthetized, sinoaortic-denervated dogs., Results: Cardiopulmonary baroreflex sensitivity (slope of %ΔRNA/ΔPCWP) for mild LVD (-17.8%/mmHg) was the same as controls (-17.7%/mmHg). However, the slopes of moderate (-5.8%/mmHg) and severe LVD (-1.9%/mmHg) were decreased significantly compared with controls (P < .05). Arterial baroreflex sensitivity was preserved at all stages of LVD. Plasma norepinephrine, renin activity, and arginine vasopressin remained unchanged after 4, 7, and 11 days of pacing., Conclusions: Vagal cardiopulmonary baroreflex control of renal sympathetic nerve activity is blunted early in the development of LVD. These abnormalities precede neurohumoral excitation and abnormal arterial baroreflexes and become apparent when LV end-diastolic volume starts to increase., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Purpose: This is a paper based on a talk given in the BER2018 conference by M. Bando. We first emphasize the importance of collaborations among scientists in various fields for the low dose/dose-rate effects on biological body. We make comparisons of quantitative estimations of mutation caused by the radiation exposure on various animals and plants using one mathematical model. We derive the importance of the spontaneous mutation at the DNA level, which provides the key to understand the biological evolution. We try to make a guide map to solve this problem and find that the mutation is an important stage of the pathway from the DNA damage to the macroscopic biological evolution. Materials and methods: We construct a mathematical model for the mutation, named as 'WAM' model, which takes into account the recovery effect. The model setting is regarded as an extension of the survival and the hazard functions. The WAM model is used to reproduce accumulated data of mutation frequency of animals and plants. Especially the model analysis shows that the dose-rate dependence is important to understand various mutation data. Results and conclusions: The WAM model is successful in reproducing various mutation data of animals and plants. We find that the inclusion of the dose rate is important to understand all the mutation data. Hence, we are able to develop the 'scaling law' to make the cross-species comparison of mutation frequency data. With this finding, we can extract the dominant effect on the mutation to be caused by the spontaneous mutation, and quantify this amount. We are able to write then the artificial radiation frequency by subtracting the spontaneous mutation. With this success, we estimate the origin of the spontaneous mutation as due to ROS, the order of which agrees to the spontaneous mutation.

Background: We investigated the effects of preoperative oral carbohydrate loading on intraoperative catabolism, nutritional parameters, and adipocytokine levels during anesthesia., Methods: Study participants were randomized to two groups who were allowed to consume either no more than 250 mL of 18% oral carbohydrate solution (Arginaid Water: AW group) or no more than 500 mL of plain water (PW group) within the 2 hours before surgery, with no intraoperative glucose administration. Percentage changes from preoperative values of resting metabolic rate (RMR) and total body water (TBW), determined by bioelectrical impedance analysis (BIA), were compared. Blood levels of serum ketone bodies, free fatty acids (FFAs), insulin, 3-methyl histidine, blood glucose, retinol binding protein, adiponectin, and leptin were measured. BIA measurement and blood sampling were performed on entry to the operating room (M1) and 2 hours after the induction of anesthesia (M2). Chi squared test, Mann-Whitney U test, and Wilcoxon's test were used for comparisons of parameters. P values less than 0.05 constituted a significant difference., Results: Seventeen patients per group (34 patients total) were enrolled. RMR and TBW values did not differ between M1 and M2 measurements. Participants in the AW group had lower blood ketone body and FFA levels and higher insulin levels at M1. However, their ketone body and FFA levels rose and insulin levels fell after 2 hours, although ketone body and FFA levels in the AW group were still lower than those in the PW group. Although retinol binding protein, adiponectin, and leptin levels were not different in terms of preoperative oral carbohydrate loading, the levels of these substances in both groups were lower after 2 hours compared with levels on operating room entry., Conclusions: Preoperative oral carbohydrate loading without intraoperative glucose administration appears to suppress catabolism for 2 hours after the start of surgery., Competing Interests: The authors have declared that no competing interests exist.

The Fas/Fas Ligand system is a major apoptosis signaling pathway that is up-regulated in patients with chronic heart failure (CHF). Serum soluble Fas (sFas) levels increase in proportion to the CHF severity and may have prognostic value, therefore, sFas is a promising biomarker of heart failure. In this study, we attempted to identify the determinants of sFas levels in patients with CHF. Serum levels of tumor necrosis factor (TNF)-α and its soluble receptors (sTNF-R1 & sTNF-R2), interleukin (IL)-6, soluble IL-6 receptor (sIL-6R), glycoprotein (gp)130, and sFas were measured in 106 patients with CHF and 39 controls. All subjects performed a symptom-limited cycle ergometer exercise test with expired gas analysis. CHF patients had higher levels of TNF-α, sTNF-R1, sTNF-R2, IL-6, and gp130. Serum levels of sFas (controls versus CHF; 2.60 ± 0.88 versus 3.38 ± 1.23 ng/mL, P = 0.0004) were higher in CHF. On univariate analysis, age (P = 0.0003), NYHA functional class (P = 0.0012), peak VO2 (P < 0.0001), plasma norepinephrine (P = 0.0013), log IL-6 (P < 0.0001), log TNF-α (P = 0.0002), log sTNF-R1 (P < 0.0001), and log TNF-R2 (P < 0.0001) were significantly related to log sFas levels. Multivariate analysis showed that age and log IL-6 and log sTNF-R1 levels were independently associated with log sFas levels (overall R = 0.603, P < 0.0001). Serum levels of sFas were increased in patients with CHF, and age and serum IL-6 and sTNF-R1 levels were independent determinants of sFas levels. These data suggest that proinflammatory cytokine activation is linked to the Fas/Fas Ligand system in patients with CHF.

Photodissociation of amorphous ice films of carbon dioxide and water co-adsorbed at 90 K was carried out at 157 nm using oxygen-16 and -18 isotopomers with a time-of-flight photofragment mass spectrometer. O((3)P(J)) atoms, OH (v = 0) radicals, and CO (v = 0,1) molecules were detected as photofragments. CO is produced directly from the photodissociation of CO(2). Two different adsorption states of CO(2), i.e., physisorbed CO(2) on the surface of amorphous solid water and trapped CO(2) in the pores of the film, are clearly distinguished by the translational and internal energy distributions of the CO molecules. The O atom and OH radical are produced from the photodissociation of H(2)O. Since the absorption cross section of CO(2) is smaller than that of H(2)O at 157 nm, the CO(2) surface abundance is relatively increased after prolonged photoirradiation of the mixed ice film, resulting in the formation of a heterogeneously layered structure in the mixed ice at low temperatures. Astrophysical implications are discussed.

The hydrolytic disproportionation of gaseous NO(2) on water's surface (2 NO(2) + H(2)O → HONO + NO(3)(-) + H(+)) (R1) has long been deemed to play a key, albeit unquantifiable role in tropospheric chemistry. We recently found that (R1) is dramatically accelerated by anions in experiments performed on aqueous microjets monitored by online electrospray mass spectrometry. This finding let us rationalize unresolved discrepancies among previous laboratory results and suggested that under realistic environmental conditions (R1) should be affected by everpresent surfactants. Herein, we report that NO(2)(g) uptake is significantly enhanced by cationic surfactants, weakly inhibited by fulvic acid (FA, a natural polycarboxylic acid) and anionic surfactants, and unaffected by 1-octanol. Surfactants appear to modulate interfacial anion coverage via electrostatic interactions with charged headgroups. We show that (R1) should be the dominant mechanism for the heterogeneous conversion of NO(2)(g) to HONO under typical atmospheric conditions throughout the day. The photoinduced reduction of NO(2) into HONO on airborne soot might play a limited role during daytime.

A 33-year-old Japanese man with atrial tachycardia visited our clinic. He regularly consumed daily alcohol with cola, one cup of regular coffee, and a candy containing 0.7 mg of caffeine per tablet. After stopping his caffeine intake, his arrhythmia ameliorated. Since caffeine might be associated with his arrhythmia, a caffeine load test (equivalent to his daily intake of caffeine) was performed for 4 days. Atrial tachycardia time from a Holter recording was 44.2 minute/day before the caffeine load, compared with 215.2 minute/day during the caffeine load. Plasma caffeine concentration before and during caffeine loading was 3.1 mg/dL and 5.4 mg/dL, respectively. Caffeine use seemed to be an important factor for his atrial tachycardia, since his arrhythmia became worse during caffeine load testing and was ameliorated after the cessation of caffeine.

Reduced coenzyme Q(10) (CoQ(10)H(2)) is known as a potent antioxidant in biological systems. However, it is not yet known whether CoQ(9)H(2) could act as an antioxidant in human cells. The aim of this study is to assess whether exogenously added CoQ(9) can protect human liver cells against injuries induced by a water-soluble radical initiator, 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and a lipid-soluble radical initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). CoQ(9)-enriched cells were obtained by treatment of HepG2 cells with 10 microM CoQ(9) liposomes for 24 h. CoQ(9)-enriched cells were exposed to 10 mM AAPH and 500 microM AMVN over 4 h and 24 h, respectively. The loss of viability after treatment with AAPH or AMVN was much less in CoQ(9)-enriched cells than in naive HepG2 cells. The decrease in glutathione and the increase in thiobarbituric acid-reactive substance after treatment with AAPH or AMVN were also suppressed in CoQ(9)-enriched cells. The incubation of CoQ(9)-enriched cells with AAPH or AMVN led to a decrease in cellular CoQ(9)H(2) and reciprocal increase in cellular CoQ(9) resulting from its antioxidant function. Taken together, it was demonstrated for the first time that exogenously added CoQ(9) could prevent oxidative stress-mediated damage to human cells by virtue of its antioxidant activity.