Surface Proton Conduction of Sm-Doped CeO2-δ Thin Film Preferentially Grown on Al2O3 (0001).

Sm-doped CeO2-δ (Ce0.9Sm0.1O2-δ; SDC) thin films were prepared on Al2O3 (0001) substrates by radio frequency magnetron sputtering. The prepared thin films were preferentially grown along the [111] direction, with the spacing of the (111) plane (d111) expanded by 2.6% to compensate for a lattice mismatch against the substrate. The wet-annealed SDC thin film, with the reduced d111 value, exhibited surface protonic conduction in the low-temperature region below 100 °C. The O1s photoemission spectrum exhibits H2O and OH- peaks on the SDC surface. These results indicate the presence of physisorbed water layers and the generation of protons on the SDC (111) surface with oxygen vacancies. The protons generated on the SDC surface were conducted through a physisorbed water layer by the Grotthuss mechanism.

Sex-based differences in CD103+ dendritic cells promote female-predominant Th2 cytokine production during allergic asthma.

BACKGROUND: Gender disparities in adult patients with asthma regarding its prevalence and severity are mainly due to enhanced type 2 T-helper (Th2) cytokine production in female patients compared to that in male patients. However, the pathways mediating this effect remain unclear. OBJECTIVE: We aimed to determine the roles of two major subsets of dendritic cells (DCs) in females, specifically those displaying CD11b or CD103, during enhanced Th2 priming after allergen exposure, using an ovalbumin-induced asthma mouse model. METHODS: Sex-based differences in the number of DCs at inflamed sites, costimulatory molecule expression on DCs, and the ability of DCs to differentiate naïve CD4+ T cells into Th2 population were evaluated after allergen exposure in asthmatic mice. In addition, we assessed the role of 17ß-oestradiol in CD103+ DC function during Th2 priming in vitro. RESULTS: The number of CD11bhigh DCs and CD103+ DCs in the lung and bronchial lymph node (BLN) was increased to a greater extent in female mice than in male mice at 16 to 20 hours after ovalbumin (OVA) inhalation. In BLNs, CD86 and I-A/I-E expression levels and antigen uptake ability in CD103+ DCs, but not in CD11bhigh DCs, were greater in female mice than in male mice. Furthermore, CD4+ T cells cultured with CD103+ DCs from female mice produced higher levels of interleukin (IL)-4, IL-5, and IL-13, compared with CD4+ T cells cultured with CD103+ DCs from male mice. The 17ß-oestradiol-oriented enhancement of CD86 expression on CD103+ DCs after allergen exposure induced the enhanced IL-5 production from CD4+ T cells. CONCLUSIONS AND CLINICAL RELEVANCE: These findings suggest that with regard to asthma, enhanced Th2 cytokine production in females might be attributed to 17ß-oestradiol-mediated Th2-oriented CD103+ DCs in the BLN.

Morphological properties of tectal neurons that project to the nucleus geniculatus lateralis, pars ventralis (GLv) and the surrounding ventral thalamus in chicks.

Layer 10 neurons of the chick tectum were morphologically investigated. The layer 10 neurons displayed heterogeneous immunoreactivities to calcium-binding proteins (CaBPs). Calbindin (CB)-immunoreactive (ir) neurons had pyramidal or round somata, primarily found in layers 5, 9, and 13. Parvalbumin (PV)-ir neurons were of various shapes with small to large somata (109.7±48.6µm(2)) that were located mainly in layers 4 and 10. Calretinin (CR)-ir neurons had small to middle-sized somata (79.3±9.7µm(2)) located primarily in layers 10 and 13, and most of them were similar to typical radial cells in size and shape. Two distinct types of neurons that projected to the nucleus geniculatus lateralis, pars ventralis (GLv) and ventral thalamus were demonstrated in layer 10. Type 1 cells had small to middle-sized somata (74.3±33µm(2)), and each cell had a single apical dendrite that ramified into bush-like branches in layer 7. These cells corresponded to CR-ir neurons and radial cells in size and shape. Type 2 cells had larger somata (124.7±52.6µm(2)), and their shapes were pyramidal, polygonal, or oval. They had multiple obliquely ascending dendrites that ramified into bush-like branches in layer 7. These cells often appeared similar to PV-ir neurons.

Ten-year hip fracture incidence rate trends in a large California population, 1997-2006.

UNLABELLED: Hip fractures are a large public health problem with significant negative impact on an individual's overall health and survival. But while the total numbers of persons affected by hip fractures may be anticipated to increase, incidence rates appear to be declining. INTRODUCTION: To describe annual hip fracture incidence rate trends in an integrated health-care organization over 1997-2006, during which a proactive bone health program was initiated program-wide and other secular trends occurred in the population. METHODS: For this ecologic trend study, we identified all men and women ≥45 years old as of January 1 of each year. Incident fractures for each year were identified using ICD-9 diagnosis codes 820-820.9, excluding all subjects who had fractures in prior years. Annual person-time at risk for hip fracture was determined from enrollment data. Sex- and age-specific and adjusted annual incidence rates were calculated. RESULTS: The overall annual hip fracture incidence rate for men declined from 1.52/1,000 person-years in 1997 to 1.29/1,000 person-years in 2006, a 15.3% (95% confidence interval [CI]=6.2-24.5) decrease. For women, incidence declined from 2.65/1,000 person-years in 1997 to 2.24/1,000 person-years in 2006, a 15.3% (95% CI=8.7-21.9) decrease. Among subjects aged 85 years or older, incidence rates for men declined from 27.0/1,000 to 18.9/1,000 person-years, and for women they declined from 32.7/1,000 to 27.1/1,000 person-years. CONCLUSION: Hip fracture incidence has been declining in all age groups over the past 10 years. While many factors may contribute to this decline, the results are consistent with a potential benefit of the active bone health intervention.

Evolutionary transformation of the cervicobrachial plexus in the colugo (Cynocephalidae: Dermoptera) with a comparison to treeshrews (Tupaiidae: Scandentia) and strepsirrhines (Strepsirrhini: Primates).

Four cervicobrachial plexuses from two colugos (Dermoptera), which are gliding mammals with semi-elongated necks, were dissected with imaging analysis and compared with those in its relatives, 12 sides of six treeshrews (Scandentia) and 32 sides of 16 strepsirrhines (Primates), for considering of its evolutionary constraint and functional adaptation. (1) The relative cervical length in the colugos was significantly longer than those in the others, regardless of the number and proportion of vertebrae. (2) In all examined colugos, the cervical plexus exhibited broader cervical root segments comprising the hypoglossal (N. XII) and first to fifth cervical (C1-C5) nerves, whereas the brachial plexus exhibited concentrated segments comprising C6 to the first thoracic nerve (T1) and part of T2. (3) On the other hand, the cervical plexus composed of N. XII and C1-C4 and the brachial plexus composed of C5-T1(2) were formed in all treeshrews (12/12 sides, 100.0%) and most strepsirrhines (27/32 sides, 84.4%) as seen in most terrestrial placental mammals. (4) Similar root segments of broader cervical and concentrated brachial plexuses were found in five sides of three strepsirrhines (15.6%), which are species with somewhat longer necks than the other strepsirrhines and treeshrews. Based on present and previous reports on elongated and shortened neck mammals, the modified root segments of the cervicobrachial plexus in the colugo appears to be related more to neck length than to its ecological habit, specialized locomotion, or any phylogenetic constraint.

Anatomical architecture of the brachial plexus in the common hippopotamus (Hippopotamus amphibius) with special reference to the derivation and course of its unique branches.

The anatomy of the brachial plexus in the common hippopotamus (Hippopotamus amphibius), which has not been previously reported, was first examined bilaterally in a newborn hippopotamus. Our observations clarified the following: (1) the brachial plexus comprises the fifth cervical (C5) to first thoracic (T1) nerves. These formed two trunks, C5-C6 and C7-T1; in addition, the axillary artery passed in between C6 and C7, (2) unique branches to the brachialis muscle and those of the lateral cutaneous antebrachii nerves ramified from the median nerve, (3) nerve fibre analysis revealed that these unique nerve branches from the median nerve were closely related and structurally similar to the musculocutaneous (MC) nerve; however, they had changed course from the MC to the median nerve, and (4) this unique branching pattern is likely to be a common morphological feature of the brachial plexus in amphibians, reptiles and certain mammals.

Sex-related splenocyte function in a murine model of allergic asthma.

BACKGROUND: The prevalence and severity of asthma are higher among boys than girls, but the ratios are reversed after puberty. These observations strongly suggest that sex hormones have a role in the pathogenesis of the disease. However, the mechanisms underlying the gender differences in asthma are not fully understood. OBJECTIVE: The aim of this study was to investigate sex differences in allergic inflammation in terms of immune function. METHODS: Male and female C57BL/6 mice were sensitized and challenged with ovalbumin (OVA). OVA-specific IgE in serum and airway inflammation were compared between sexes. Splenocytes from OVA-sensitized male or female donor mice were transferred to male or female naïve recipient mice. Subsequently, the recipient mice were challenged, followed by the evaluation of OVA-specific IgE and airway inflammation. Cytokines secreted from splenocytes of the sensitized mice were measured. RESULTS: The levels of OVA-specific IgE and the allergen-induced airway inflammation were higher in female than in the male mice. The contents of T-helper type 2 (Th2) cytokines, IL-4, IL-5 and IL-13, in the bronchoalveolar lavage fluid from female mice were higher than those from male mice. The airway inflammation in female recipients transferred with splenocytes from female donors was more severe than that in any other combination of recipients and donors. Splenocytes from the sensitized female mice produced more of the Th2 cytokine, IL-5, than those from the sensitized male mice upon stimulation with OVA. CONCLUSION: Our findings suggest that the sex difference in allergic airway inflammation may be attributable to the sex difference in not only the hormonal environment but also in the immune cells themselves.

Mutations of carnitine palmitoyltransferase II (CPT II) in Japanese patients with CPT II deficiency.

Carnitine palmitoyltransferase II (CPT II) deficiency is an inherited disorder involving beta-oxidation of long-chain fatty acids. CPT II deficiency is a wide-spectrum disorder that includes a lethal neonatal form, an infantile form, and an adult-onset form. However, the ethnic characteristics and the relationship between genotype and clinical manifestation are not well understood. We investigated three non-consanguineous Japanese patients with CPT II deficiency and examined cell lines from 4 unrelated patients and 50 healthy donors. The CPT 2 gene was typed by direct DNA sequencing of polymerase chain reaction-amplified gene products. Case 1 (infantile form) was heterozygous for a phenylalanine to tyrosine substitution at position 383 (p.F383Y) and a novel valine to leucine substitution at 605 (p.V605L). Cases 2, 4, and 5 (infantile form) and case 3 (adult-onset form) were heterozygous for a single mutation at F383Y. Case 6 (adult-onset form) was compound heterozygous at the CPT 2 locus, with deletion of cytosine and thymine at residue 408, resulting in a stop signal at 420 (p.Y408fsX420), and an arginine to cysteine substitution at position 631 (p.R631C). Case 7 (adult-onset form) was homozygous for the p.F383Y mutation. In conclusion, we identified p.F383Y mutations in six of seven patients with CPT II deficiency and two novel variants of the coding gene: p.Y408fsX420 and p.V605L. These mutations differ from those in Caucasian patients, who commonly harbor p.S113L, p.P50H, and p.Q413fsX449 mutations; therefore, our data and those of other Japanese groups suggest that the p.F383Y mutation is significant in Japanese patients with CPT II deficiency.

The involvement of type 1a angiotensin II receptors in the regulation of airway inflammation in a murine model of allergic asthma.

BACKGROUND: There has been increasing evidence suggesting the involvement of angiotensin II (Ang II) and type 1 Ang II receptors (AT1) in the pathogenesis of bronchial asthma. However, whether such an involvement would promote or suppress the pathophysiology of asthma is controversial. OBJECTIVE: The aim of this study was to investigate the role of AT1 in the development of allergic airway inflammation. METHODS: Agtr1a+/+ [wild-type C57BL/6 mice (WT)] and Agtr1a-/- mice [AT1a knockout mice (AT1aKO)] with a genetic background of C57BL/6 were systemically sensitized to ovalbumin (OVA), followed by OVA inhalation. OVA-specific IgE in serum obtained just before the inhalation was measured. Bronchoalveolar lavage (BAL) fluid and lung tissues were obtained at various time-points. Cell numbers and differentiation, and cytokine contents in BAL fluids were determined. Peribronchial accumulation of eosinophils and mucus inclusions in the bronchial epithelium were evaluated in lung tissues stained histochemically. Cell numbers and differentiation in BAL fluids of the mice were also determined after lipopolysaccharide (LPS) inhalation. RESULTS: The levels of OVA-specific IgE in AT1aKO were significantly higher than those in WT. The numbers of total cell, eosinophils and lymphocytes in BAL fluids 7 days after OVA inhalation in AT1aKO were significantly higher than those in WT. Airway inflammation in bronchial tissues in terms of eosinophil accumulation and mucus hypersecretion in AT1aKO was also stronger than in WT. The contents of IL-4, IL-5 and IL-13, but not IFN-gamma, in BAL fluids of AT1aKO were significantly higher than those of WT. In contrast, neutrophil accumulation in BAL fluids after LPS inhalation was significantly higher in WT than in AT1aKO. CONCLUSION: AT1a might be involved in the negative regulation of the development of allergic airway inflammation through polarizing the T-helper (Th) balance towards Th1 predominance. Therefore, it would be of clinical importance to investigate the effects of long-term administration of AT1 blockers on the Th1/Th2 balance in hypertensive patients with bronchial asthma.

Microtopography of the dual corticothalamic projections originating from domains along the frequency axis of the cat primary auditory cortex.

Spatial relationships between clusters of corticothalamic (CT) large terminals originating from cortical domains tuned to different frequencies were examined by pair-injecting two different anterograde tracers. Large-terminal CT projection originating from layer 5 was highly divergent with each injection site producing, on average, 15 local clusters distributing throughout non-lemniscal thalamic nuclei following a single anterograde tracer injection in the cat primary auditory cortex. Paired injections in higher- and lower-frequency cortical domains, resulting in labeling of two independent sets of terminal clusters, showed five recognizable patterns of spatial interaction between them. (1) In the ventral division of the medial geniculate complex (vMGC), sheet-like plexuses of small terminals of different origins were situated in parallel, with minimal overlap. (2) Extensive overlap of two low-density plexuses of differently labeled small terminals was observed in the medial division of the medial geniculate complex (MGC). (3) At the transition zones between the vMGC and the superficial dorsal nucleus of the MGC dorsal division, and between the vMGC and the ventrolateral nucleus, there were relatively broad clusters of a high density of large-terminal structures from the two cortical domains, which overlapped extensively. (4) At multiple loci in the nonlemniscal nuclei, pairing of two small clusters of differently labeled large terminals was observed. (5) Small unpaired clusters of large terminals were also found in the nonlemniscal nuclei. For large terminals, approximately 14%, 59%, and 27% clusters per injection demonstrated patterns 3, 4, and 5, respectively. The results provide evidence for the precise topographical organization for the large-terminal CT system at the microscopic level despite its highly divergent projection. This microtopographical projection from the tonotopic cortical field to non-tonotopic thalamic nuclei may raise the possibility of presence of a map that has not been defined in auditory non-lemniscal thalamic nuclei yet.

Significant correlations between the flow volume of patent ductus venosus and early neonatal liver function: possible involvement of patent ductus venosus in postnatal liver function.

BACKGROUND: The biochemical features of portosystemic venous shunt with high flow volume are hypergalactosaemia, hyperammonaemia, prolonged blood coagulation time, and raised serum bile acid concentration. The ductus venosus remains open with shunt flow in most neonates for a certain period after birth. However, the effects of blood flow through the ductus venosus on neonatal liver function remain unclear. OBJECTIVE: To elucidate the effect of patency of the ductus venosus on liver function in early neonates. METHODS: Subjects were divided into three groups by gestational age (group I, 29-32 weeks; group II, 33-36 weeks; group III, 37-41 weeks). The shunt flow volume through the ductus venosus was examined serially using ultrasonography, and correlations between flow volume and liver function in the respective groups were calculated during the first week after birth. RESULTS: Group I had a higher flow volume and later functional closure than the other two groups. Plasma ammonia and serum total bile acid concentrations correlated with flow volume in groups I and II, and blood galactose and galactose 1-phosphate concentrations correlated significantly with flow volume in group III. Percentage hepaplastin also correlated significantly with flow volume in all groups, but plasma vitamin K concentration did not in any group. CONCLUSIONS: Patent ductus venosus has a considerable effect on crucial liver functions such as ammonia detoxification, blood coagulation, and regulation of serum total bile acid concentration in early neonates.

Isofrequency band-like zones of activation revealed by optical imaging of intrinsic signals in the cat primary auditory cortex.

Neurons of similar frequency preference are arranged in isofrequency bands (IFBs) across the primary auditory cortex (AI) of many mammals. Across the AI of the cat, one of the most frequently studied species for auditory anatomy and function, we demonstrate IFB-like responses using optical imaging of intrinsic signals (OIS). Optically defined activations were extensively elongated along the dorsoventral axis of AI (the ratio of the major and minor axes was approximately 2:1), and systematically shifted as a function of stimulus frequency. The elongation of this IFB-like zone was more conspicuous at higher frequencies. In the ventral sector of the imaged field, the IFB-like zones of activation evoked at different pure tone frequencies tended to overlap extensively. Electrophysiological recording from loci within the optically defined zones of activation revealed matched responses to the frequencies used for optical imaging at 65% of these loci. The dorsoventral orientation of these zones of activation was also closely matched with the orientation of tangentially spreading intrinsic axon terminals, as revealed anatomically. The visualization of IFB-like architecture and tonotopic organization by OIS provides a basic framework for investigating the relationships of different spectral channels and between multiple acoustic parameters at a neuronal population level.

Cortical convergence from different frequency domains in the cat primary auditory cortex.

Primary auditory cortex (AI) has a tonotopic map consisting of orderly isofrequency (IF) bands, and cortical connections are commonly supposed to link domains preferring similar characteristic frequencies (CFs) within AI and in auditory association cortex. The interaction of different frequency channels, however, has not fully been understood in terms of anatomical substrates. Here, by injecting two anterograde tracers in different frequency domains of cat AI, without overlap of the injection cores, we attempted to relate the anatomical mapping of cortical outputs to physiologically defined fields in the auditory cortex. Consistent with previous studies, patches of labeled axon terminals were oriented largely along the IF axis. In regions distant from the injection sites, however, terminal patches were divergent in distribution. This divergence resulted in a complex geometry of partial overlap of projections originating from the two injection sites. The relative extent of the overlap tended to vary depending on the distance between the two injection sites. Physiological mapping for tonotopy across auditory fields revealed that projectional overlap was characteristic of dorsal AI and the dorsoposterior field and, to a lesser extent, in the secondary auditory field. Considering the differences in frequency representation in different AI IF bands, the anatomical convergence of projections tuned to different CFs could contribute to the spectral integration of sound components. Furthermore, the different extent of convergence in the functionally distinct fields might reflect field-specific processing of acoustic signals.

Myocardial infarction caused by rheumatoid vasculitis: histological evidence of the involvement of T lymphocytes.

Rheumatoid arthritis (RA) is a chronic joint disease that can be complicated with extra-articular manifestations due to vasculitis. We describe a patient with RA who developed systemic vasculitis and died of myocardial infarction. Autopsy demonstrated vasculitis of the left anterior descendent and circumflex coronary arteries, which were narrowed or occluded with organizing thrombosis. Formation of granuloma with multinucleated giant cells was also observed in media of the circumflex artery. There was no microscopic evidence of atheroma formation in the coronary arteries. Of note, there was a follicle-like infiltration of CD45RO-positive T lymphocytes in interna of the left coronary arteries and the right renal artery. Although not frequently reported, coronary vasculitis as a cause of myocardial infarction should be considered in patients with RA. Moreover, our results suggest that infiltration of T lymphocytes might be involved in the development of rheumatoid vasculitis.

Mechanism of tonic spasms in West syndrome viewed from ictal SPECT findings.

To clarify the pathophysiology of tonic spasms, 21 patients with West syndrome were analyzed using ictal and interictal single photon emission computed tomography (SPECT). We focused on whether ictal perfusion changes were observed in the focal cortical region. Eight of the patients studied showed definite focal cortical ictal hyperperfusion, indicating that there is a unique subset of West syndrome that can be classified as infantile localization-related epilepsy. Of those eight patients, only two showed asymmetric spasms, suggesting that seizure symptomatology in infants gives only limited information on the localization-related nature of epilepsy. Furthermore, the activation of subcortical structures by focal cortical regions might be attributable to the symmetric seizure phenomena. Thirteen patients showed a diffuse pattern in their ictal SPECTs; this probably included patients with diffuse hyperperfusion and those with no changes. The following have yet to be determined: (1) whether West syndrome is divided into subgroups based on the origin of spasms, in that some patients have the origin in the cortical hemisphere and some have the origin in structures other than the cortical hemisphere, such as the brain stem; (2) whether differences in ictal SPECT patterns reflect a unique nature of tonic spasms in West syndrome, where tonic spasms appear in clusters and the interval of each spasm is different among each patient.

Circumvention of acquired resistance to doxorubicin in K562 human leukemia cells by oxatomide.

We studied the effect of oxatomide, an antiallergic drug, on the resistance of K562 cells to doxorubicin. Oxatomide synergistically potentiated the cytotoxicity of doxorubicin in doxorubicin-resistant K562 cells (K562/DXR) at a concentration of 1-10 microM, but had hardly any synergistic effect on the parental cell line (K562) at the same concentration. Oxatomide inhibit P-glycoprotein pump-efflux activity and the binding of [3H]-azidopine to the cell-surface protein P-glycoprotein, in a dose-related manner. These results indicate that oxatomide reverses the multidrug-resistance phenotype through direct interaction with P-glycoprotein.

Apoptosis induced by doxorubicin and cinchonine in P388 multidrug-resistant cells.

Acquired drug resistance is a major factor in the failure of doxorubicin-based cancer chemotherapy. We determined the ability of cinchonine to reverse doxorubicin drug resistance in a doxorubicin-resistant leukaemia cell line (mouse P388/DOX). A non-cytotoxic concentration of cinchonine (10 microM) increased the sensitivity to doxorubicin of multidrug-resistant P388/DOX cells and significantly enhanced the doxorubicin-induced apoptosis and DNA fragmentation in resistant cells, but had no effect in parent cells. Time-course studies demonstrated that DNA fragmentation was present 24 h after incubation with doxorubicin and cinchonine, indicating that DNA degradation was a preceding event. In cultured cells, cinchonine increased the intracellular accumulation of doxorubicin in the resistant cells in a dose-dependent manner. Using flow cytometry to measure the inhibition of the P-glycoprotein (P-gp) dependent efflux of rhodamine 123, cinchonine was found to be considerably more effective than quinine. The results with cinchonine suggest that there may be quinine derivatives with a similar capacity to inhibit drug transport by P-gp. Additionally, the G2/M phase cell population in resistant cells is increased by doxorubicin/cinchonine treatment. Exposure of resistant cells to 1 microM doxorubicin and 10 microM cinchonine resulted in the expression of Fas (APO-1/CD95) in cells after 6 h. These studies demonstrate that the cell killing effects of doxorubicin and cinchonine in resistant cells

Reversal of vinblastine resistance in human leukemic cells by haloperidol and dihydrohaloperidol.

Haloperidol, an antipsychotic, was investigated in cells overexpressing P-glycoprotein to detemine whether it was a clinically effective drug to reverse for reversing multidrug resistance (MDR) mediated by P-glycoprotein. A nontoxic concentration of haloperidol (1-30 microM) enhanced the cytotoxic effects of vinblastine (VBL) concentration-dependently in VBL-resistant human leukemia (K562/VBL) cells, but had no effect in the parent cells. Haloperidol also enhanced the cytotoxicities of epirubicin, doxorubicin and actinomycin D in the K562/VBL cells, but not those of idarubicin or cisplatin; this enhancement was less than that of the VBL toxicity in the VBL-resistant tumor line. Haloperidol increased the intracellular accumulation of VBL in the K562/VBL cells, and the binding of [3H]-azidopine to the cell-surface protein, P-glycoprotein, was inhibited by haloperidol in a concentration-dependent manner. Haloperidol was less potent than verapamil. Thus, haloperidol appeared to potentiate anticancer agents through the reversal of MDR by competitively inhibiting drug-binding to P-glycoprotein. In contrast, the main metabolite of haloperidol, dihydrohaloperidol, without antipsychotic activity, had less of an effect. Therefore, haloperidol might be useful in reversing drug-resistance.

Mechanism of resistance to oxidative stress in doxorubicin resistant cells.

Doxorubicin (DOX) is an anthracycline drug widely used in chemotherapy for cancer patients, but it often gives rise to multidrug resistance in cancer cells. The purpose of this work was to study the effect of hydrogen peroxide in DOX-sensitive mouse P388/S leukemia cells and in the DOX-resistant cell line. Hydrogen peroxide induced a significant increase in dose- and time-response cell death in cultured P388/S cells. The degree of cell death in P388/DOX cells induced by hydrogen peroxide was less than that in P388/S cells treated with hydrogen peroxide. Parent cells exposed to 3 mM of hydrogen peroxide showed a loss of mitochondrial membrane potential correlated with cell death. Hydrogen peroxide at a concentration greater than 0.3 mM increased the intracellular Ca2+ of P388/S cells dose-dependently; however, no change following addition of hydrogen peroxide (0.3-1 mM) was observed in the resistant cells. Hydrogen peroxide (0.1 and 1 mM) treatment also induced the production of intracellular ROS in P388/S cells, while no such increase was produced by this substance in P388/DOX cells. Resistant cells also showed a significant level of glutathione (GSH) compared with the parent cells. In addition, N-acetyl-L-cysteine and reduced GSH antioxidants abolished death of P388/S cells caused by hydrogen peroxide. Therefore, it is believed that the reduced effect of oxidative stress towards the resistant cells may be related to an increase in intracellular GSH level.