Evaluation of different algal species sensitivity to mercury and metolachlor by PAM-fluorometry

In this study, the pulse-amplitude-modulation (PAM)-fluorometric method was used to evaluate the difference in the sensitivity to mercury (Hg) and metolachlor of six algal species: Ankistrodesmus falcatus, Selenastrum capricornutum, Chlorella vulgaris, Nannoplankton (PLS), Microcystis aeruginosa and Pediastrum biwae. We found that the fluorescence parameters (phiM, the maximal photosystem II (PSII) quantum yield, phi'M, the operational PSII quantum yield at steady state of electron transport, Q(P), the photochemical quenching value, and Q(N), the non-photochemical quenching value) were appropriate indicators for inhibitory effects of mercury but only phi'M and Q(N) were useful for metolachlor. The examined algal species showed very different levels of sensitivity to the effect of Hg and of metolachlor. The most sensitive species to Hg and metolachlor were respectively M. aeruginosa and A. falcatus, while the least sensitive were C. vulgaris and P. biwae. We interpreted these differences by the action mode of pollutants and by the different metabolism properties and morphological characteristics between algal species. These results related to fluorescence parameters may offer useful tool to be used in bioassay for different pollutants. Heterogeneous algal sensitivity to the same pollutant suggests the need to use a battery of species to evaluate the effects of mixtures of pollutants in aquatic systems.

Effects of cysteine on the pharmacokinetics of intravenous phenytoin in rats with protein-calorie malnutrition

The effects of cysteine on the pharmacokinetics of phenytoin and one of its metabolites, 5-(p-hydroxyphenyl)-5-phenylhydantoin (pHPPH) were investigated after intravenous administration of phenytoin, 25 mg/kg, to control rats (4-week fed on 23% casein diet) and rats with PCM (protein-calorie malnutrition, 4-week fed on 5% casein diet) and PCMC (PCM with oral cysteine supplementation, 250 mg/kg, twice daily starting from the fourth week). In rats with PCM and PCMC, the phenytoin hydroxylation (to form pHPPH) activities were significantly smaller (164, 103 and 95.3 pmol/min per mg protein for the control rats, and rats with PCM and PCMC, respectively) than that in control rats. In rats with PCMC, the intrinsic clearance of phenytoin, CL(int) was significantly slower than those in control rats and rats with PCM (0.175, 0.131 and 0.044 ml/min). The above data suggested that the formation of pHPPH could be reduced in rats with PCM and PCMC. This was supported by significantly smaller 24-h urinary excretion of pHPPH (54.7, 35.6 and 32.5% of intravenous dose of phenytoin) in rats with PCM and PCMC than that in control rats. In rats with PCM, the maximum velocity (0.344, 0.203 and 0.196 microg/min), apparent volume of distribution in central compartment (44.4, 65.4 and 72.2 ml/kg) of phenytoin, and total area under the plasma concentration-time curve from time zero to time infinity (609, 714 and 1210 microg min/ml), renal clearance (20.5, 13.4 and 4.67 ml/min per kg) and 24-h urinary excretion (54.7, 35.6 and 32.5% of intravenous dose of phenytoin) of pHPPH were not returned to control levels by cysteine supplementation (rats with PCMC). This could be mainly due to the fact that the phenytoin hydroxylation activity in rats with PCMC was not returned to control level.

Treatment of chronic osteomyelitis in Korea

OBJECTIVE

We sought to investigate the clinical and histopathologic features of chronic osteomyelitis and its treatment in Koreans.

STUDY DESIGN

A total of 49 patients (ages 11-79 years; mean, 47.3 years) were examined in this retrospective chart review. In a new treatment protocol used for 39 patients, chronic osteomyelitis of the jaws was treated by surgical intervention and 2 weeks of intravenous antibiotics, followed by 6 weeks of oral antibiotics, whereas a control group consisting of 10 patients was treated by surgery alone. Surgical therapy consisted of decortication or sequestrectomy and saucerization of the affected bone. A successful outcome was defined as the resolution of symptoms after surgery alone or after surgery and 8 weeks of antibiotic therapy. Failure was defined as a case requiring a second operation and 8 additional weeks of antibiotic therapy.

RESULTS

A successful outcome was seen in 94.9% of patients on the new treatment protocol, as well as in 60% of control patients. A purulent discharge developed in 2 cases after the new treatment protocol and in 4 control cases, but the patients were treated successfully with a second operation.

CONCLUSIONS

Surgery followed by antibiotic therapy for at least 8 weeks is an effective method for treating chronic osteomyelitis of the jaws.

A novel denitrifying bacterial isolate that degrades trimethylamine both aerobically and anaerobically via two different pathways

The aerobic and anaerobic degradation of trimethylamine by a newly isolated denitrifying bacterium from an enrichment culture with trimethylamine inoculated with activated sludge was studied. Based on 16S rDNA analysis, this strain was identified as a Paracoccus sp. The isolate, strain T231, aerobically degraded trimethylamine, dimethylamine and methylamine and released a stoichiometric amount of ammonium ion into the culture fluid as a metabolic product, indicating that these methylated amines were completely degraded to formaldehyde and ammonia. The strain degraded trimethylamine also under denitrifying conditions and consumed a stoichiometric amount of nitrate, demonstrating that complete degradation of trimethylamine was coupled with nitrate reduction. Cell-free extract prepared from cells grown aerobically on trimethylamine exhibited activities of trimethylamine mono-oxygenase, trimethylamine N-oxide demethylase, dimethylamine mono-oxygenase, and methylamine mono-oxygenase. Cell-free extract from cells grown anaerobically on trimethylamine and nitrate exhibited activities of trimethylamine dehydrogenase and dimethylamine dehydrogenase. These results indicate that strain T231 had two different pathways for aerobic and anaerobic degradation of trimethylamine. This is a new feature for trimethylamine metabolism in denitrifying bacteria.

Effects of presurgical and post-surgical irradiation on the healing process of Medpor in dogs

The purpose of this study was to determine the effect of irradiation on the healing process and the effect on the contact surface of Medpor and bone. Eighteen dogs were studied. The animals were divided into three groups. Six non-irradiated dogs served as controls (Group 1). Twelve dogs irradiated on the left femur, before and after implantation of Medpor, were studied. The dogs were euthanized 4 and 8 weeks after Medpor was implanted in presurgical irradiation subgroup animals (Group 2) and after the completion of irradiation in post-surgical irradiation subgroup animals (Group 3). Light microscopic and scanning electron microscopic examinations were performed. The appearance of osteoblasts and bone matrix formation were remarkably late and manifest slight reactions in post-surgical irradiation group compared to the control group presenting the osteoblasts at 4 weeks, and those osteoblasts were not visible in presurgical irradiation group in both the 4-week and 8-week observation. We concluded that the bone remodeling was delayed in the irradiated bone, especially in the presurgical group.

Localized cerebral blood flow response at submillimeter columnar resolution

Functional magnetic resonance imaging (fMRI) has been widely used for imaging brain functions. However, the extent of the fMRI hemodynamic response around the active sites, at submillimeter resolution, remains poorly understood and controversial. With the use of perfusion-based fMRI, we evaluated the hemodynamic response in the cat visual cortex after orientation-specific stimuli. Activation maps obtained by using cerebral blood flow fMRI measurements were predominantly devoid of large draining vein contamination and reproducible at columnar resolution. Stimulus-specific cerebral blood flow responses were spatially localized to individual cortical columns, and columnar layouts were resolved. The periodic spacing of orientation columnar structures was estimated to be 1.1 +/- 0.2 mm (n = 14 orientations, five animals), consistent with previous findings. The estimated cerebral blood flow response at full width at half-maximum was 470 microm under single-stimulus conditions without differential subtraction. These results suggest that hemodynamic-based fMRI can indeed be used to map individual functional columns if large-vessel contributions can be minimized or eliminated.

Resolution analysis of incoherent triangular holography

We derived the point-spread function (PSF) including the recording and reconstruction systems of the modified triangular interferometer; the modified triangular interferometer forms incoherent holograms without bias and the conjugate image. We also derived and analyzed the resolution of the modified triangular interferometer and compared it with that of the conventional one for amplification factor, wavelength, and hologram size.

Inadequate implant angulation resulting from oroantral fistula: case report

Successful implant surgery is largely dependent on good treatment planning and careful surgery. A complete treatment plan must encompass both surgical and prosthetic considerations for the implant restoration. Some compromised implants are restorable, and the result can be acceptable if they can be adjusted into a more ideal position. The goals of the segmental osteotomy are the preservation of a healthy dental unit, the creation of a more ideal environment for dental restoration and occlusal reconstruction, the optimization of cost effectiveness, and the minimization of edentulous space. The purpose of this study is to present the segmental maxillary osteotomy to reposition the alveolar segment with its implant that was in a highly compromised situation.

cDNA cloning of two isoforms of ornithine carbamoyltransferase from Canavalia lineata leaves and the effect of site-directed mutagenesis of the carbamoyl phosphate binding site

The immunoscreening method was used to isolate cDNAs of 1323 bp (ClOCT1) and 1433 bp (ClOCT2) encoding two ornithine carbamoyltransferases (OCT, EC 2.1.3.3) from the cDNA expression library of Canavalia lineata leaves constructed in a lambdaZAP Express vector. ClOCT1 and ClOCT2 encode 359 and 369 amino acids, respectively. The N-terminals of deduced amino acid sequences of the two cDNAs showed typical features of the transit peptide of chloroplast targeting proteins. The ornithine-binding domain (FMHCLP) and catalytic domain (HPXQ) of ClOCT1 and ClOCT2 and the carbamoyl phosphate (CP)-binding site of ClOCT1 (SMRTR) are identical to OCTs of other plant species, pea and Arabidopsis thaliana. However, the CP-binding site sequence of ClOCT2, SLRTH, has not yet been reported. Both ClOCT1 and ClOCT2 cDNAs were expressed in Escherichia coli BL21 (DE3) by using expression vector pET30a. Recombinant ClOCT1 protein showed 14 times higher ornithine-dependent OCT activity than canaline-dependent OCT activity. In contrast, recombinant ClOCT2 protein showed 13 times higher canaline-dependent OCT activity than ornithine-dependent OCT activity. The two amino acids of the CP-binding site of ClOCT2 (SLRTH) were combinatorially changed to those of the CP-binding site of ClOCT1 (SMRTR) by site-directed mutagenesis. When Leu-118 of ClOCT2 was changed to Met, ornithine-dependent activity was increased significantly. It is assumed that the substrate specificity of ClOCT1 or ClOCT2 proteins partially depends on the amino acid sequence of the CP-binding site.

Sinus node recovery after 25 years of atrial flutter

This case report demonstrates that the sinus node can recover relatively quickly even after being suppressed by atrial flutter for 25 years, and that a permanent pacemaker may not always be necessary in all patients with sinus arrest after a successful atrial flutter ablation.

Determination of a chemopreventive agent, Oltipraz, in rat plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for the determination of a chemopreventive agent, Oltipraz, in rat plasma and urine. The sample preparation was simple; 2 volumes of acetonitrile were added to deproteinize the biological sample. A 50-microl aliquot of the supernatant was injected onto a C18 reversed-phase column. The mobile phase, acetonitrile : 0.5 mM ammonium acetate (55: 45, v/v for rat plasma and 45 : 55, v/v for rat urine), was run at a flow-rate of 1.5 ml/min. The column effluent was monitored using an ultraviolet detector set at 305 nm. The retention times for Oltipraz in rat plasma and urine were approximately 5.8 and 8.6 min, respectively. The detection limits of Oltipraz in rat plasma and urine were 20 and 50 ng/ml, respectively. The coefficients of variation of the assay (within-day and between-day) were generally low (below 4.65%) in concentration ranges from 0.02 (0.05) to 10 microg/ml for rat plasma and urine. No interference from endogenous substances was found.

2-(Allylthio)pyrazine, a cancer chemopreventive agent, inhibits liver fibrosis induced by dimethylnitrosamine in rats: role of inhibition of transforming growth factor-beta1 expression

Exposure to nitrosamines may be the occupational risk factor for liver cirrhosis. 2-(Allylthio)pyrazine, a chemopreventive agent, inhibits CYP2E1 and induces phase II enzymes. We examined the effects of 2-(allylthio)pyrazine on hepatic fibrosis, a prepathologic state of cirrhosis, and on the expression of transforming growth factor-beta1 induced by dimethylnitrosamine. Treatment of rats with dimethylnitrosamine for 4 weeks increased plasma alanine/aspartate amino-transferase and y-glutamyl transpeptidase activities, and bilirubin content, whereas the total plasma protein and albumin levels were decreased. 2-(Allylthio)pyrazine inhibited dimethylnitrosamine-induced increases in the enzyme activities and bilirubin, and restored the plasma protein and albumin contents. Masson's trichrome staining showed that dimethylnitrosamine induced liver fibrosis, the extent of which was reduced by 2-(allylthio)pyrazine treatments. Reverse transcription-polymerase chain reaction analysis revealed that 2-(allylthio)pyrazine inhibited production of transforming growth factor-beta1 mRNA by dimethylnitrosamine. These results demonstrated that 2-(allylthio)pyrazine might inhibit dimethylnitrosamine-induced liver fibrosis due to suppression of CYP2E1 expression and transforming growth factor-beta1 production.

8-Cl-cAMP induces cell cycle-specific apoptosis in human cancer cells

8-Cl-cyclic adenosine monophosphate (8-Cl-cAMP) has been known to induce growth inhibition and differentiation in a variety of cancer cells by differential modulation of protein kinase A isozymes. To understand the anticancer activity of 8-Cl-cAMP further, we investigated the effect of 8-Cl-cAMP on apoptosis in human cancer cells. Most of the tested human cancer cells exhibited apoptosis upon treatment with 8-Cl-cAMP, albeit with different sensitivity. Among them, SH-SY5Y neuroblastoma cells and HL60 leukemic cells showed the most extensive apoptosis. The effect of 8-Cl-cAMP was not reproduced by other cAMP analogues or cAMP-elevating agents, showing that the effect of 8-Cl-cAMP was not caused by simple activation of protein kinase A (PKA). However, competition experiments showed that the binding of 8-Cl-cAMP to the cAMP receptor was essential for the induction of apoptosis. After the treatment of 8-Cl-cAMP, cells initially accumulated at the S and G2/M phases of the cell cycle and then apoptosis began to occur among the population of cells at the S/G2/M cell cycle phases, indicating that the 8-Cl-cAMP-induced apoptosis is closely related to cell cycle control. In support of this assumption, 8-Cl-cAMP-induced apoptosis was blocked by concomitant treatment with mimosine, which blocks the cell cycle at early S phase. Interestingly, 8-Cl-cAMP did not induce apoptosis in primary cultured normal cells and non-transformed cell lines, showing that 8-Cl-cAMP-induced apoptosis is specific to transformed cells. Taken together, our results show that the induction of apoptosis is one of the mechanisms through which 8-Cl-cAMP exerts anticancer activity.

Atomic-scale dynamics of the formation and dissolution of carbon clusters in SiO(2)

Oxidation of SiC produces SiO(2) while CO is released. A "reoxidation" step at lower temperatures is, however, necessary to produce high-quality SiO(2). This step is believed to cleanse the oxide of residual C without further oxidation of the SiC substrate. We report first-principles calculations that describe the nucleation and growth of O-deficient C clusters in SiO(2) under oxidation conditions, fed by the production of CO at the advancing interface, and their gradual dissolution by the supply of O under reoxidation conditions. We predict that both CO and CO(2) are released during both steps.

Activation of phosphatidylinositol 3-kinase by oxidative stress leads to the induction of microsomal epoxide hydrolase in H4IIE cells

We have shown that PI3-kinase played an essential role in the ARE-mediated rGSTA2 induction by oxidative stress following SAAD (Mol. Pharmacol. 58 (2000) 1017). Microsomal epoxide hydrolase (mEH), which detoxifies a variety of epoxide intermediates produced from various xenobiotics, is inducible by oxidative stress. In the present study, we studied whether sulfur amino acid deprivation (SAAD) activated phosphatidylinositol 3-kinase (PI3-kinase)/Akt and induced mEH in H4IIE cells. The role of PI3-kinase activation on the mEH induction by SAAD was also investigated. PI3-kinase was activated from 10 min through 12 h after SAAD, the activity of which returned to control level at 24 h. The activation of PI3-kinase led to increases in the activity of Akt at the same time points. Northern and Western blot analyses revealed that the mEH mRNA level was four-fold increased at 48 h, which accompanied the induction of mEH protein. Wortmannin or LY294002, PI3-kinase inhibitors, completely inhibited the increases in mEH mRNA and protein by SAAD. These results demonstrated that SAAD activated the PI3-kinase/Akt pathway at early stages and induced mEH, presumably as an adaptive response, and that the PI3-kinase/Akt pathway played a crucial role in the induction of mEH.

Implant-related damage to an adjacent tooth: a case report

Implant-related damage to an adjacent tooth is shown to be an iatrogenic complication. The affected tooth may require apical curettage, root canal therapy, apicoectomy, or even extraction. A case is presented of a patient who complained of damage to an adjacent root after implant placement.

Perfusion imaging using dynamic arterial spin labeling (DASL)

Recently, a technique based on arterial spin labeling, called dynamic arterial spin labeling (DASL (Magn Reson Med 1999;41:299-308)), has been introduced to measure simultaneously the transit time of the labeled blood from the labeling plane to the exchange site, the longitudinal relaxation time of the tissue, and the perfusion of the tissue. This technique relies on the measurement of the tissue magnetization response to a time varying labeling function. The analysis of the characteristics of the tissue magnetization response (transit time, filling time constant, and perfusion) allows for quantification of the tissue perfusion and for transit time map computations. In the present work, the DASL scheme is used in conjunction with echo planar imaging at 4.7 T to produce brain maps of perfusion and transit time in the anesthetized rat, under graded hypercapnia. The data obtained show the variation of perfusion and transit time as a function of arterial pCO2. Based on the data, CO2 reactivity maps are computed. Published 2001 Wiley-Liss, Inc.

In vivo measurements of brain glucose transport using the reversible Michaelis-Menten model and simultaneous measurements of cerebral blood flow changes during hypoglycemia

Glucose is the major substrate that sustains normal brain function. When the brain glucose concentration approaches zero, glucose transport across the blood-brain barrier becomes rate limiting for metabolism during, for example, increased metabolic activity and hypoglycemia. Steady-state brain glucose concentrations in alpha-chloralose anesthetized rats were measured noninvasively as a function of plasma glucose. The relation between brain and plasma glucose was linear at 4.5 to 30 mmol/L plasma glucose, which is consistent with the reversible Michaelis-Menten model. When the model was fitted to the brain glucose measurements, the apparent Michaelis-Menten constant, Kt, was 3.3 +/- 1.0 mmol/L, and the ratio of the maximal transport rate relative to CMRglc, Tmax/CMRglc, was 2.7 +/- 0.1. This Kt is comparable to the authors' previous human data, suggesting that glucose transport kinetics in humans and rats are similar. Cerebral blood flow (CBF) was simultaneously assessed and constant above 2 mmol/L plasma glucose at 73 +/- 6 mL 100 g(-1) min(-1). Extrapolation of the reversible Michaelis-Menten model to hypoglycemia correctly predicted the plasma glucose concentration (2.1 +/- 0.6 mmol/L) at which brain glucose concentrations approached zero. At this point, CBF increased sharply by 57% +/- 22%, suggesting that brain glucose concentration is the signal that triggers defense mechanisms aimed at improving glucose delivery to the brain during hypoglycemia.

Ameloblastoma: a clinical, radiographic, and histopathologic analysis of 71 cases

OBJECTIVES

The purpose of this study was to compare the clinical, radiologic, and histopathologic features of 71 intraosseous ameloblastomas.

STUDY DESIGN

Data with respect to the patients' ages, sex, tumor locations, and surgical treatment history, as well as the radiographic findings and number of recurrences, were analyzed. The histologic types of and radiologic findings regarding tumors with higher recurrence rates were also investigated.

RESULTS

The patients' ages at biopsy ranged from 11 to 70 years (mean, 30.4 years). Thirty-nine (54.9%) of the 71 subjects were males, and 32 (45.1%) were females. Sixty-two (87.3%) of the 71 ameloblastomas were located in the mandible. Swelling was the most common symptom and was experienced by 27 (38.0%) patients. Radiographically, 42 (59.2%) of the 71 tumors were unilocular with a well-demarcated border. Of the remaining 29 cases, 14 were multilocular, 2 were of soap-bubble shape, and 13 were unknown in appearance. The most common histologic pattern was plexiform, rather than follicular or acanthomatous. Sixteen cases of ameloblastoma had developed in a cyst. The overall recurrence rate was 21.1%, and the average age of the patient at recurrence was 26.4 years.

CONCLUSIONS

When the diagnosis of ameloblastoma in young people remains in doubt after clinical and radiologic examination, a biopsy is necessary. Long-term follow-up at regular intervals after surgery is also recommended.

DA-125, a novel anthracycline derivative showing high-affinity DNA binding and topoisomerase II inhibitory activities, exerts cytotoxicity via c-Jun N-terminal kinase pathway

PURPOSE

DA-125 [(8S,10S)-8-(3-Aminopropanoyloxyacetyl)-10-[(2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl) oxy]-7,8,9,10-tetrahydro-6,8,11-trihydroxy-1-methoxy-5,12-naphthacene-dione hydrochloride] is a novel anthracycline derivative with anticancer activity. In the present study, we compared the cytotoxicity of DA-125 with that of doxorubicin in H4IIE rat hepatoma cells and investigated the mechanistic basis. Because activation of MAP kinases, in particular c-Jun N-terminal kinase (JNK), is implicated in apoptotic cell death, the signaling pathways responsible for DA-125-induced apoptosis were studied.

METHODS

Cytotoxicity and apoptosis were measured in H4IIE cells and cells were stably transfected with a dominant-negative mutant of JNK1 (JNK1-) by MTT and TUNEL assays. Inhibition of topoisomerase II activity was determined in vitro. Drug accumulation and DNA binding affinity were determined by fluorescence spectroscopy.

RESULTS

The cytotoxicity of DA-125 was greater than that of doxorubicin (IC50 11.5 vs 70 microM). DA-125 induced apoptosis with 30-fold greater potency than doxorubicin. Inhibition of topoisomerase II by DA-125 was fourfold greater. The presence of excess beta-alanine, a DA-125 moiety, failed to alter cytotoxicity and accumulation of DA-125, indicating that the improved cytotoxicity of DA-125 did not result from the beta-alanine moiety. Greater cellular accumulation of DA-125 correlated with its high-affinity DNA binding. Although neither PD98059 nor SB203580 altered the degree of cytotoxicity induced by DA-125, JNK1 cells exhibited about a twofold greater viability than control cells. DA-125-induced apoptosis was also decreased in JNK1- -transfected cells.

CONCLUSIONS

DA-125 potently inhibited topoisomerase II activity and induced apoptosis by a high rate of prooxidant production. DA-125 exhibited high-affinity DNA binding with improved cellular drug accumulation. Apoptosis induced by DA-125 involved the pathway of JNK1, but not ERK1/2 or p38 kinase.

Changes in human regional cerebral blood flow and cerebral blood volume during visual stimulation measured by positron emission tomography

The hemodynamic mechanism of increase in cerebral blood flow (CBF) during neural activation has not been elucidated in humans. In the current study, changes in both regional CBF and cerebral blood volume (CBV) during visual stimulation in humans were investigated. Cerebral blood flow and CBV were measured by positron emission tomography using H(2)(15)O and (11)CO, respectively, at rest and during 2-Hz and 8-Hz photic flicker stimulation in each of 10 subjects. Changes in CBF in the primary visual cortex were 16% +/- 16% and 68% +/- 20% for the visual stimulation of 2 Hz and 8 Hz, respectively. The changes in CBV were 10% +/- 13% and 21% +/- 5% for 2-Hz and 8-Hz stimulation, respectively. Significant differences between changes in CBF and CBV were observed for visual stimulation of 8 Hz. The relation between CBF and CBV values during rest and visual stimulation was CBV = 0.88CBF(0.30). This indicates that when the increase in CBF during neural activation is great, that increase is caused primarily by the increase in vascular blood velocity rather than by the increase in CBV. This observation is consistent with reported findings obtained during hypercapnia.

Activation of phosphatidylinositol 3-kinase and Akt by tert-butylhydroquinone is responsible for antioxidant response element-mediated rGSTA2 induction in H4IIE cells

The protective adaptive response to electrophiles and reactive oxygen species is mediated by enhanced expression of phase II detoxifying genes, including glutathione S-transferases, through activation of antioxidant response element (ARE). The current study was designed to investigate the role of phosphatidylinositol 3-kinase (PI3-kinase)-Akt and mitogen-activated protein (MAP) kinase signaling pathways in the induction of rGSTA2 by tert-butylhydroquinone (t-BHQ). Nuclear ARE complex was activated 1 to 6 h after treatment of H4IIE cells with t-BHQ. The rGSTA2 mRNA level was elevated 6 to 24 h after t-BHQ treatment, which led to the enzyme induction. Activities of PI3-kinase and Akt were increased 10 min through 6 h after t-BHQ treatment, whereas wortmannin or LY294002, PI3-kinase inhibitors, completely abolished ARE binding activity and increases in rGSTA2 mRNA and protein. Extracellular signal-regulated kinase (ERK), p38 MAP kinase, and c-Jun N-terminal kinase (JNK) were all activated by t-BHQ. Treatment with PD98059, an ERK inhibitor, however, increased rGSTA2 mRNA and further enhanced t-BHQ-induced expression of rGSTA2. Neither SB203580 nor overexpression of JNK1 dominant negative mutant altered t-BHQ-inducible rGSTA2 expression. These results demonstrated that t-BHQ activated PI3-kinase and Akt, which was responsible for ARE-mediated rGSTA2 induction, and that ERK might negatively regulate rGSTA2 expression, whereas activation of p38 MAP kinase or of JNK by t-BHQ was not associated with the enzyme induction.

Relative changes of cerebral arterial and venous blood volumes during increased cerebral blood flow: implications for BOLD fMRI

Measurement of cerebral arterial and venous blood volumes during increased cerebral blood flow can provide important information regarding hemodynamic regulation under normal, pathological, and neuronally active conditions. In particular, the change in venous blood volume induced by neural activity is one critical component of the blood oxygenation level-dependent (BOLD) signal because BOLD contrast is dependent only on venous blood, not arterial blood. Thus, relative venous and arterial blood volume (rCBV) and cerebral blood flow (rCBF) in alpha-chlorolase-anesthetized rats under hypercapnia were measured by novel diffusion-weighted (19)F NMR following an i.v. administration of intravascular tracer, perfluorocarbons, and continuous arterial spin labeling methods, respectively. The relationship between rCBF and total rCBV during hypercapnia was rCBV(total) = rCBF(0.40), which is consistent with previous PET measurement in monkeys. This relationship can be linearized in a CBF range of 50-130 ml/100 g/min as DeltarCBV(total)/ DeltarCBF = 0.31 where DeltarCBV and DeltarCBF represent rCBV and rCBF changes. The average arterial volume fraction was 0.25 at a basal condition with CBF of approximately 60 ml/100 g/min and increased up to 0.4 during hypercapnia. The change in venous rCBV was 2-fold smaller than that of total rCBV (DeltarCBV(vein)/DeltarCBF = 0.15), while the arterial rCBV change was 2.5 times larger than that of total rCBV (DeltarCBV(artery)/DeltarCBF = 0.79). These NMR results were confirmed by vessel diameter measurements with in vivo videomicroscopy. The absolute venous blood volume change contributes up to 36% of the total blood volume change during hypercapnia. Our findings provide a quantitative physiological model of BOLD contrast.

Glutathione S-transferase mu modulates the stress-activated signals by suppressing apoptosis signal-regulating kinase 1

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase that can activate the c-Jun N-terminal kinase and the p38 signaling pathways. It plays a critical role in cytokine- and stress-induced apoptosis. To further characterize the mechanism of the regulation of the ASK1 signal, we searched for ASK1-interacting proteins employing the yeast two-hybrid method. The yeast two-hybrid assay indicated that mouse glutathione S-transferase Mu 1-1 (mGSTM1-1), an enzyme involved in the metabolism of drugs and xenobiotics, interacted with ASK1. We subsequently confirmed that mGSTM1-1 physically associated with ASK1 both in vivo and in vitro. The in vitro binding assay indicated that the C-terminal portion of mGSTM1-1 and the N-terminal region of ASK1 were crucial for binding one another. Furthermore, mGSTM1-1 suppressed stress-stimulated ASK1 activity in cultured cells. mGSTM1-1 also blocked ASK1 oligomerization. The ASK1 inhibition by mGSTM1-1 occurred independently of the glutathione-conjugating activity of mGSTM1-1. Moreover, mGSTM1-1 repressed ASK1-dependent apoptotic cell death. Taken together, our findings suggest that mGSTM1-1 functions as an endogenous inhibitor of ASK1. This highlights a novel function for mGSTM1-1 insofar as mGSTM1-1 may modulate stress-mediated signals by repressing ASK1, and this activity occurs independently of its well-known catalytic activity in intracellular glutathione metabolism.