New studies on trans-anethole oxide and trans-asarone oxide

The widespread use of naturally occurring alkenylbenzenes as flavoring and fragrance agents has led to a long-standing interest in their toxicity and carcinogenicity. Among them several allyl- and propenylbenzenes have been found to be mutagenic and carcinogenic. It has been shown that the carcinogenicity of several allylbenzenes can be related to the formation of electrophilic sulfuric acid esters following 1'-hydroxylation. Unlike the allylbenzenes, the mechanisms of carcinogenesis of propenylbenzenes such as anethole and asarone are not clear. It has been reported that one of the main metabolic pathways of trans-anethole is the epoxidation of the side chain 1,2-double bond, which was responsible for cytotoxicity but not for genotoxicity. However, we report here that synthetic trans-anethole oxide prepared from trans-anethole and dimethyldioxirane is not only mutagenic for Salmonella tester strains but is also carcinogenic in the induction of hepatomas in B6C3F1 mice and skin papillomas in CD-1 mice. Synthetic trans-asarone oxide was also carcinogenic in the induction of hepatomas as well as mutagenic for Salmonella strains. Further studies are needed on these side chain oxides of trans-anethole and trans-asarone as possible metabolites in the toxicity, mutagenicity and carcinogenicity of these and other propenylbenzenes.

2-(Allylthio)pyrazine inhibition of aflatoxin B1-induced hepatocarcinogenesis in rats

2-(Allylthio)pyrazine (2-AP), a synthetic pyrazine derivative with an allylsulfur moiety, has hepatoprotective effects against toxicants. Effect of 2-AP on hepatic tumorigenesis in association with glutathione S-transferase (GST) induction was examined in rats exposed to aflatoxin B1 (AFB1). Both AFB1-DNA adduct formation in the liver and urinary elimination of 8,9-dihydro-8-(N7-guanyl)-9-hydroxy-aflatoxin B1 (AFB1-N7-guanine) adduct were also determined. Male Sprague Dawley rats were treated with 2-AP at the daily oral doses of 10, 25 and 50 mg/kg for 16 consecutive days, during which four repeated doses of AFB1 (1.0 mg/kg) were given to the animals. Rats were then subjected to two-thirds of hepatectomy, followed by administration of phenobarbital (PB). Focal areas of hepatocellular alteration were identified after 44 days and preneoplastic foci expressing the placental form of glutathione S-transferase P (GST-P) were quantified by immunostaining of liver sections. 2-AP reduced the volume of liver occupied by GST-P foci by 65-96%. Under these experimental conditions, 2-AP treatment resulted in significant elevations in GST activity in the liver. Levels of radiolabeled AFB1 covalently bound to hepatic DNA, RNA and proteins were significantly reduced in rats treated with 2-AP for 5 days. 2-AP pretreatment also caused a 45% reduction in the urinary elimination of AFB1-N7-guanine adduct over the 24-h postdosing period. The present findings demonstrated that 2-AP exhibited protective effects against AFB1-induced hepatocarcinogenesis in rats with a marked decrease in the level of AFB1-DNA adduct. Reduction of hepatic DNA adducts might result from elevations of activity of GST, which catalyzes detoxification of the carcinogen.

Grafting of large defects of the jaws with a particulate dentin-plaster of paris combination

OBJECTIVE

The purpose of this report is to show the usefulness and discuss the effects of a particulate dentin and plaster of paris combination as a bone graft material in jaw defects.

STUDY DESIGN

This was a retrospective evaluation of 10 patients with jaw defects who underwent grafting with a combination of particulate dentin and plaster of paris. The material was used when the defects were more than 20 mm in diameter. The ratio was 2:1 by weight. Patients were examined for any evidence of infection and recurrence during the follow-up periods.

RESULTS

During a mean follow-up of 52.2 months (range, 50 to 57 months), patients had minor immediate postoperative complications. These complications were swelling and perforation; they were treated without problems through use of incision and drainage, antibiotic treatment, and buccal flap.

CONCLUSIONS

On the basis of the results that we obtained radiographically and clinically, it may be concluded that the particulate dentin plaster mixture is a useful and readily available material for bone substitute.

Analysis of cDNAs expressed during first cell division of petunia petal protoplast cultures using expressed sequence tags

A large-scale sequence analysis of randomly selected cDNA clones was performed to isolate numerous genes in petunia petal protoplast cultures. We have partially sequenced 1158 randomly selected genes of the cDNA library constructed from 2-6 d cultured petal protoplasts. Three hundred and sixty-five different genes were identified, 25% of which showed significant similarity to existing sequences in the petunia, and an array of other organisms. In this report, 90 independent genes are analyzed in detail. A functional categorization of the database-matched expressed sequence tags (ESTs) showed that defense- or stress-related genes, as well as genes involved in the primary metabolic pathways and in the transcriptional or translational apparatus are abundantly represented. In particular, ESTs were identified with apparent homologies to the cyclin-dependent kinase, histone, actin-depolymerizing factor, proteasome, and ubiquitin which are expected to be related to cell division or to cell cycle control.

Molecular basis for hepatic detoxifying enzyme induction by 2-(allylthio)pyrazine in rats in comparison with oltipraz: effects on prooxidant production and DNA degradation

The expression of hepatic microsomal epoxide hydrolase (mEH) and glutathione S-transferases (GSTs) by 2-(allylthio)pyrazine (2-AP), an experimental chemopreventive agent, was investigated in rats. Northern blot analysis revealed that 2-AP caused increases in mEH, rGSTA2/3/5, and rGSTM1/2 mRNA levels. mEH and rGSTA2 proteins were also induced. Molecular basis of the enzyme induction by 2-AP was studied in comparison with oltipraz (Olt). Rats exposed to buthionine sulfoximine, a GSH-depleting agent, before treatment with either 2-AP or Olt exhibited greater increases in the mRNA levels than the individual treatment. Conversely, increases of the mRNAs were prevented by cysteine treatment, indicating that metabolic intermediates or reactive oxygens produced from the agents could be reduced by cysteine. Gel shift analysis revealed that nuclear factor-kappaB, which is associated with the altered cellular redox state, was not activated by the agents. Effects of these agents on the breakage of phix-174 DNA were compared in vitro. 2-AP effectively reduced the conversion of supercoiled DNA to the open circular form induced by benzenetriol and prevented benzenetriol- and iron-catalyzed degradation of DNA, whereas Olt failed to prevent strand breakage of DNA. These results provided evidence that: 1) 2-AP was effective in elevating the hepatic mEH and GST gene expression in rats, which might be mediated with the production of reactive oxygen species; 2) nuclear factor-kappaB activation was not involved in the induction of the detoxifying enzymes by either 2-AP or Olt in spite of their production of reactive oxygens in vivo; and 3) the antioxidant effect of 2-AP in vitro differed from that of Olt.

Determination of relative CMRO2 from CBF and BOLD changes: significant increase of oxygen consumption rate during visual stimulation

The blood oxygenation level-dependent (BOLD) effect in functional magnetic resonance imaging depends on at least partial uncoupling between cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) changes. By measuring CBF and BOLD simultaneously, the relative change in CMRO2 can be estimated during neural activity using a reference condition obtained with known CMRO2 change. In this work, nine subjects were studied at a magnetic field of 1.5 T; each subject underwent inhalation of a 5% carbon dioxide gas mixture as a reference and two visual stimulation studies. Relative CBF and BOLD signal changes were measured simultaneously using the flow-sensitive alternating inversion recovery (FAIR) technique. During hypercapnia established by an end-tidal CO2 increase of 1.46 kPa, CBF in the visual cortex increased by 47.3 +/- 17.3% (mean +/- SD; n = 9), and deltaR2* was -0.478 +/- 0.147 sec(-1), which corresponds to BOLD signal change of 2.4 +/- 0.7% with a gradient echo time of 50 msec. During black/white visual stimulation reversing at 8 Hz, regional CBF increase in the visual cortex was 43.6 +/- 9.4% (n = 18), and deltaR2* was -0.114 +/- 0.086 sec(-1), corresponding to a BOLD signal change of 0.6 +/- 0.4%. Assuming that CMRO2 does not change during hypercapnia and that hemodynamic responses during hypercapnia and neural stimulation are similar, relative CMRO2 change was determined using BOLD biophysical models. The average CMRO2 change in the visual cortex ranged from 15.6 +/- 8.1% (n = 18) with significant cerebral blood volume (CBV) contribution to 29.6 +/- 18.8% without significant CBV contribution. A weak positive correlation between CBF and CMRO2 changes was observed, suggesting the CMRO2 increase is proportional to the CBF increase.

Description of hydration free energy density as a function of molecular physical properties

A method to calculate the solvation free energy density (SFED) at any point in the cavity surface or solvent volume surrounding a solute is proposed. In the special case in which the solvent is water, the SFED is referred to as the hydration free energy density (HFED). The HFED is described as a function of some physical properties of the molecules. These properties are represented by simple basis functions. The hydration free energy of a solute was obtained by integrating the HFED over the solvent volume surrounding the solute, using a grid model. Of 34 basis functions that were introduced to describe the HFED, only six contribute significantly to the HFED. These functions are representations of the surface area and volume of the solute, of the polarization and dispersion of the solute, and of two types of electrostatic interactions between the solute and its environment. The HFED is described as a linear combination of these basis functions, evaluated by summing the interaction energy between each atom of the solute with a grid point in the solvent, where each grid point is a representation of a finite volume of the solvent. The linear combination coefficients were determined by minimizing the error between the calculated and experimental hydration free energies of 81 neutral organic molecules that have a variety of functional groups. The calculated hydration free energies agree well with the experimental results. The hydration free energy of any other solute molecule can then be calculated by summing the product of the linear combination coefficients and the basis functions for the solute.

Chemopreventive effects of 2-(allylthio)pyrazine

A series of organosulfur compounds were synthesized with the aim of developing chemopreventive compounds active against hepatotoxicity and chemical carcinogenesis. 2-(Allylthio) pyrazine (2-AP) was effective in inhibiting cytochrome P450 2E1-mediated catalytic activities and protein expression, and in inducing microsomal epoxide hydrolase and major glutathione S-transferases. 2-AP reduced the hepatotoxicity caused by toxicants and elevated cellular GSH content. Development of skin tumors, pulmonary adenoma and aberrant crypt foci in colon by various chemical carcinogens was inhibited by 2-AP pretreatment. Anticarcinogenic effects of 2-AP at the stage of initiation of tumors were also observed in the aflatoxin B1 (AFB1)-induced three-step medium-term hepatocarcinogenesis model. Reduction of AFB1-DNA adduct by 2-AP appeared to result from the decreased formation of AFB1-8,9-epoxide via suppression of cytochrome P450, while induction of GST by 2-AP increases the excretion of glutathione-conjugated AFB1. 2-AP was a radioprotective agent effective against the lethal dose of total body irradiation and reduced radiation-induced injury in association with the elevation of detoxifying gene expression. 2-AP produces reactive oxygen species in vivo, which is not mediated with the thiol-dependent production of oxidants and that NF-kappa B activation is not involved in the induction of the detoxifying enzymes. The mechanism of chemoprotection by 2-AP may involve inhibition of the P450-mediated metabolic activation of chemical carcinogens and enhancement of electrophilic detoxification through induction of phase II detoxification enzymes which would facilitate the clearance of activated metabolites through conjugation reaction.

Synthesis and analgesic and anti-inflammatory activities of 1,2-benzothiazine derivatives

Three 1,2-benzothiazine derivatives were synthesized, and their analgesic/anti-inflammatory efficacy and their effects on gastric irritation were evaluated. Among the three compounds, 39 exhibited the most potent analgesic action, but the effect was weaker than that of piroxicam. Nonetheless, the compound showed 4 times more potent analgesic action with less gastric damage than did ibuprofen. These compounds did not show anti-inflammatory effect at an oral dose of 5 mg/kg.

Thioureas differentially induce rat hepatic microsomal epoxide hydrolase and rGSTA2 irrespective of their oxygen radical scavenging effect: effects on toxicant-induced liver injury

Thioureas have been employed as potent hydroxyl radical scavengers and also inhibit production of oxygen free radicals. The in vitro oxygen radical scavenging effect by N,N'-substituted thioureas including dimethylthiourea (DMT), diethylthiourea (DET), tetramethylthiourea (TMT) and diphenylthiourea (DPT) was assessed by the conversion of phi x-174 DNA from supercoiled DNA to the open circular form or to fragmented DNA. Addition of the N,N'-substituted thioureas to the incubation mixture significantly prevented a single strand breakage of phi x-174 DNA induced by autooxidation of benzenetriol. These thioureas were also effective in preventing degradation of phi x-174 DNA induced by autooxidation of benzenetriol in the presence of ferrous iron. In view of the in vitro radical scavenging effect by the thioureas and the role of reactive oxygen species in the induction of phase II detoxifying enzymes, expression of microsomal epoxide hydrolase (mEH) and rGSTA2 in response to these agents was investigated in the rat liver. Rats treated with each of the alkylthioureas exhibited marked increases of mEH and rGSTA2 mRNA levels with TMT being the most effective. DPT an arylthiourea, however, was minimally active in increasing the mRNAs. Time-course studies revealed that DMT, DET and TMT increased the mRNA levels to the greatest extent at 24 h after a single dose of treatment. The levels of mEH and rGSTA2 mRNA were elevated in a dose-dependent manner by the alkylthioureas. Immunoblot analysis showed that the alkylthioureas induced mEH and rGSTA2 proteins in the liver (0.6 mmol/kg per day, 3 days), which was consistent with the increases in the mRNA levels. DMT, DET or TMT enhanced CCl4-induced liver toxicity, as monitored by plasma aminotransferase activity, although each of the agents alone caused only slight increase in the alanine aminotransferase activity. In contrast to the effects of the alkylthioureas, DPT protected the liver against the toxicant-induced injury. All of the thioureas prevented decreases in the hepatic glutathione level by CCl4. Expression of cytochrome P450 2E1 and P450 2B1/2, which are implicated with metabolic activation of CCl4, was assessed after treatment with the thioureas. P450 2E1 and P450 2B1/2 were differentially induced by the alkylthioureas with the expression of P450 2E1 being inversely related with that of P450 2B1/2. These results showed that N,N'-substituted alkylthioureas were capable of inducing mEH and rGSTA2 in the liver with elevation of the mRNAs, that induction of mEH and rGSTA2 by these alkylthioureas might be mediated by production of the reactive oxygens derived from metabolic activation of the agents irrespective of their radical scavenging effect and that the agents rather enhanced toxicant-induced liver injury with the induction of P450 2E1 or P450 2B1/2.

Inhibitory effects of isopropyl-2-(1,3-dithietane-2-ylidene)-2- [N-(4-methylthiazol-2-yl)carbamoyl]acetate (YH439) on benzo[a]pyrene-induced skin carcinogenesis and micronucleated reticulocyte formation in mice

Recently, a great deal of attention has been devoted to organosulfur compounds with potential cancer chemopreventive properties. Many sulfur-containing substances present in Brassica plants have been reported to possess striking anticarcinogenic and antimutagenic activities. Besides naturally occurring organosulfur compounds, certain synthetic sulfur-containing pharmaceuticals, such as oltipraz and sulindac, are known to exert substantial chemopreventive or chemoprotective effects. Isopropyl-2-(1, 3-dithietane-2-ylidene)-2-[N-(4-methylthiazol-2-yl)carbamoyl ]acetate (YH439) was initially developed for its possible use as a hepatoprotectant. The compound has been found to up-regulate the expression of cytochrome P-450 IA1 [I.J. Lee, K.S. Jeong, B.J. Roberts, A.T. Kallarakal, P. Fernandez-Salguero, F.J. Gonzalez, B.J. Song, Transcriptional induction of the cytochrome P-450 1A1 gene by a thiazolium compound YH439, Mol. Pharmacol. 49 (1996) 980-988.] which plays a pivotal role in metabolism of the majority of polycyclic aromatic carcinogens and mutagens, such as benzo[a]pyrene (B[a]P). In the present study, we found that oral administration of YH439 to CD-1 mice significantly suppressed B[a]P-initiated skin tumorigenesis. B[a]P-induced formation of micronuclei in mouse peripheral reticulocytes was also attenuated by YH439 pretreatment. Likewise, diallyl sulfide, a major volatile thioether present in garlic, also protected against B[a]P-induced skin tumorigenesis and micronucleated reticulocyte formation in mice.

Characterization of cDNAs encoding cytoplasmic ribosomal protein L15 and L27a in petunia (Petunia hybrida): primary structures and coordinate expression

We have isolated two cDNA clones, PhRL15 and PhRL27a, encoding cytoplasmic ribosomal proteins L15 and L27a, from a cDNA library prepared from petunia petal protoplast cultures. An expressed sequence tag (EST) strategy was employed. PhRL15 and PhRL27a contained open reading frames corresponding to proteins of 204 and 150 amino acids and molecular weights of 24,100 and 17,000Da, respectively. The deduced amino acid sequences of these clones are about 60% to 70%, identical with those of yeast and rat. Southern blot analysis indicates that each gene may be encoded by a small multigene. The transcription levels of both clones were high in young vegetative organs, at the early event of floral development, and in dividing petal protoplast, and relatively low in highly differentiated reproductive organs. Our results demonstrate that the expression levels of both clones are correlated with the rate of growth and coordinatively controlled in petunia plant.

Reproducibility of BOLD-based functional MRI obtained at 4 T

The reproducibility of activation patterns in the whole brain obtained by functional magnetic resonance imaging (fMRI) experiments at 4 Tesla was studied with a simple finger-opposition task. Six subjects performed three runs in one session, and each run was analyzed separately with the t-test as a univariate method and Fisher's linear discriminant analysis as a multivariate method. Detrending with a first- and third-order polynomial as well as logarithmic transformation as preprocessing steps for the t-test were tested for their impact on reproducibility. Reproducibility across the whole brain was studied by using scatter plots of statistical values and calculating the correlation coefficient between pairs of activation maps. In order to compare reproducibility of "activated" voxels across runs, subjects and models, 2% of all voxels in the brain with the highest statistical values were classified as activated. The analysis of reproducible activated voxels was performed for the whole brain and within regions of interest. We found considerable variability in reproducibility across subjects, regions of interest, and analysis methods. The t-test on the linear detrended data yielded better reproducibility than Fisher's linear discriminant analysis, and therefore seems to be a robust although conservative method. Preliminary data indicate that these modeling results may be reversed by preprocessing to reduce respiratory and cardiac physiological noise effects. The reproducibility of both the position and number of activated voxels in the sensorimotor cortex was highest, while that of the supplementary motor area was much lower, with reproducibility of the cerebellum falling in between the other two areas.

T cell subsets in chronic hepatitis B and the effect of prednisolone withdrawal and interferon alpha-2b

OBJECTIVES

The evaluations of the pathogenetic roles of cell mediated immunity and of the preventive effect for disease progression with interferon(IFN) treatment in patients with chronic active hepatitis-B(CAH-B) are the objectives of this study.

METHODS

Thirty-two patients with CAH-B were treated with interferon alpha-2b(IFN alpha-2b) with prednisolone withdrawal and 30 control patients were treated with conventional hepatotonics for 6 months. Peripheral total T cell fractions and T cell subsets of the patients with CAH-B, treated with IFN alpha-2b with prednisolone withdrawal, were examined 1 month before administration of prednisolone, and compared with 12 normal controls for assessing the potential role of cellular immunity in the development of CAH-B. To estimate the effectiveness of IFN therapy for the patients with CAH-B, levels of various liver function tests, HBsAg, anti-HBs, HBeAg, anti-HBe, HBV DNA, anti-HCV and others were assessed for the treatment group and compared with control patients at pre- and post-treatment period each.

RESULTS

The value of CD4 was significantly lower in patients with CAH-B than normal controls (36.3 +/- 7.7% vs 42.1 +/- 5.7%, p < 0.05) and the value of CD8 was significantly higher in patients with CAH-B than normal controls (30.6 +/- 10.3% vs 24.3 +/- 5.2%, p < 0.05) before prednisolone administration. The patients in responder group (n = 26) had significantly lower CD4 cells compared with normal controls, but non-responders (n = 6) did not have. The levels of liver function test(LFT) in the patients with IFN alpha-2b treatment with prednisolone withdrawal were not different from the control patient group at pretreatment, but significantly lower than control patient group's after treatment, regardless of response to IFN alpha-2b treatment with prednisolone withdrawal.

CONCLUSIONS

The cellular immunity of the host may have a potential role in the pathogenesis of chronicity of hepatitis B infection. IFN alpha-2b treatment with prednisolone withdrawal may be regarded as one of the effective treatment modalities for the inhibition of disease progression in patients with CAH-B.

Lipopolysaccharide inhibition of rat hepatic microsomal epoxide hydrolase and glutathione S-transferase gene expression irrespective of nuclear factor-kappaB activation

Lipopolysaccharide (LPS) is an endotoxin involved in septic shock syndrome and potentiates toxicant-induced liver injury. The effects of LPS on the constitutive and inducible expression of hepatic microsomal epoxide hydrolase (mEH) and glutathione S-transferase (GST) genes were studied in rats. Northern blot analysis showed that treatment of rats with LPS caused suppression in mEH and GST gene expression. The mEH mRNA level was decreased in a time-dependent manner following a single dose of LPS (1 mg/kg, i.v.), resulting in levels of 52%, 22%, 17%, and 94% of those in untreated animals at 2, 6, 12, and 24 hr, respectively. The levels of rGSTA2 and rGSTA3 mRNA were suppressed in response to an LPS injection to the similar extents as observed in mEH mRNA, whereas rGSTM1 and rGSTM2 mRNA levels were less affected. LPS inhibited mEH gene expression at the doses of 1 microg or greater. Whereas treatment of rats with allyl disulfide (ADS), oltipraz (OZ) or pyrazine (PZ) at the dose of 50 mg/kg caused increases in the mEH mRNA level at 12 hr, a concomitant LPS injection (1 mg/kg) resulted in 80%-95% suppression of the inducible gene expression. The inducible rGSTA2, rGSTA3, rGSTM1, and rGSTM2 mRNA levels were also 50%-90% decreased at 12 hr after LPS treatment, with the relative change in rGSTA being greater than that in rGSTM. Three consecutive daily treatments with LPS (10 microg/kg/day) resulted in significant decreases of the constitutive and PZ (50 mg/kg/day, i.p. for 3 days)-inducible mEH and GST mRNA levels, which were consistent with those in the protein levels. Gel shift retardation analysis showed that LPS substantially activated the hepatic nuclear p65/p50 nuclear factor-kappaB (NF-kappaB) complex with the maximal effect observed at 1 hr at the doses of 1 microg/kg or greater. LPS-induced activation of nuclear NF-kappaB (1 microg/kg, i.v.) failed to be inhibited by concomitant treatment with the mEH and GST inducers, including ADS (300 mg/kg, p.o.), OZ (300 mg/kg, p.o.), and PZ (300 mg/kg, i.p.), indicating that NF-kappaB activation was not required for suppression of the gene expression by LPS. In contrast, GdCl3, an inhibitor of mEH and GST expression, inhibited LPS-induced activation of the p65/p50 NF-kappaB. These gel shift analyses provided evidence that LPS-induced activation of the NF-kappaB was not responsible for alterations in the gene expression. In summary, the results of this research demonstrate that LPS effectively inhibits constitutive and inducible mEH and GST expression with decreases in their mRNA levels, and that LPS suppression in the expression of the detoxifying enzymes is not mediated with its activation of NF-kappaB.

Differential induction of rat hepatic microsomal epoxide hydrolase and rGSTA2 by diazines: the role of cytochrome P450 2E1-mediated metabolic activation

Previous studies have shown that pyridazine (PD) and pyrazine (PZ) are efficacious in inducing microsomal epoxide hydrolase (mEH) in the liver with elevation of the mRNA level. The present study was designed to investigate the expression of mEH and rGSTA2 genes in response to the diazines including PD, PZ and pyrimidine (PM) and the basis for their enzyme induction. Rats treated with either PD or PZ for 3 days resulted in marked increases in mEH and rGSTA2 mRNA levels with concomitant induction of the proteins, whereas PM failed to elevate the mRNA levels. Treatment of rats with a single dose of PD or PZ showed dose-dependent increases in mEH and rGSTA2 mRNA levels at 24 h with ED50 values being approximately 10 mg/kg. Time-course studies showed that the mRNA levels were increased to maximal extents at 24-48 h after treatment. Studies were extended to assess the mechanistic basis for the enzyme induction by PD and PZ. beta-Naphthoflavone (BNF) caused a 6-fold increase of rGSTA2 mRNA in the liver (100 mg/kg per day, p.o., 3 days), as compared to control, whereas the agent failed to increase mEH mRNA level. Administration of PD or PZ (50 mg/kg) to BNF-pretreated rats resulted in no enhanced increase of the mEH mRNA as compared to the individual treatment, while the rGSTA2 mRNA level was additively elevated, suggesting the possibility that increases of the mEH and rGSTA2 mRNAs by PD or PZ might be mediated with antioxidant responsive element(s) in the genes, but not with xenobiotic responsive element. Western blot analysis revealed that cytochrome P450 2E1 was induced 3- to 4-fold by both PD and PZ, whereas PM failed to induce P450 2E1. Concomitant treatment of rats with PD or PZ in combination with acetone, a substrate for P450 2E1, caused no significant increase in the mEH and rGSTA2 mRNA levels relative to that in untreated animals, whereas PD or PZ treatment without a concomitant acetone administration resulted in marked increases of the mRNAs. Diazine-inducible mEH and rGSTA2 mRNA levels were approximately 2-fold enhanced in P450 2E1-induced starved rats, as compared to those in diazine-treated unstarved animals. These data indicate that P450 2E1-mediated bioactivation of the diazines might contribute to transcriptional activation of the mEH and GST genes. These results provide evidence that both PD and PZ efficaciously induce mEH and rGSTA2 in the liver with increases in the mRNA levels, while PM is ineffective, and that induction of mEH and rGSTA2 may be mediated through bioactivation of the diazines by P450 2E1.

Correlation of increased mortality with the suppression of radiation-inducible microsomal epoxide hydrolase and glutathione S-transferase gene expression by dexamethasone: effects on vitamin C and E-induced radioprotection

Previous studies in this laboratory have shown that gamma-ray ionizing radiation in combination with oltipraz, a radioprotective agent, enhances hepatic microsomal epoxide hydrolase (mEH) and glutathione S-transferase (GST) expression. The present study was designed to investigate the effects of dexamethasone on the radiation-inducible expression of mEH and rGST genes and on the vitamin C and E-induced radioprotective effects in association with the expression of the genes. Treatment of rats with a single dose of dexamethasone (0.01-1 mg/kg, p.o.) caused a dose-dependent decrease in the constitutive mEH gene expression at 24 hr. The radiation-inducible mEH mRNA level (threefold increase after 3 Gy gamma-irradiation) was decreased by 21% and 88% by dexamethasone at the doses of 0.1 and 1 mg/kg, respectively. Although dexamethasone alone caused 2- to 5-fold increases in the hepatic rGSTA2 mRNA level, rats treated with dexamethasone prior to 3 Gy irradiation exhibited 80%-93% suppression in the radiation-inducible increases in the rGSTA2 mRNA level. The inducible rGSTA3 and rGSTA5 mRNA levels were also significantly decreased by dexamethasone, whereas the rGSTM1 mRNA level was reduced to a lesser extent. Vitamin C and/or E, however, failed to enhance the radiation-inducible increases in hepatic mEH and rGST mRNA levels. Whereas rats exposed to 3 Gy irradiation with or without vitamin C treatment (30 or 200 mg/kg/day, p.o., 2 days) exhibited approximately threefold increases in the mEH and rGSTA2/3/5 mRNA levels relative to untreated animals, dexamethasone treatment (1 mg/kg, p.o.) resulted in 64%-96% decreases in the mRNA levels at 24 hr. The inducible rGSTM1/2 mRNA levels in the vitamin C/E-treated rats were approximately 50% suppressed by dexamethasone. Although vitamin C and/or E treatment (200 mg/kg/day, p.o., 2 days) improved the 30-day survival rates of the 8 Gy gamma-irradiated mice from 39% up to 74%, the improved survival rate of gamma-irradiated animals was reduced to 30% by dexamethasone pretreatment (1 mg/kg/day, 2 days). The mean survival time of dexamethasone-treated animals was reduced to approximately 2 days from 14 days in the animals with total body irradiation alone. No significant hematologic changes were observed in mice at 10 days after dexamethasone plus gamma-irradiation, as compared with irradiation alone. These results demonstrate that: dexamethasone substantially suppresses radiation-inducible mEH, rGSTA and rGSTM expression in the liver; vitamins C/E exhibit radioprotective effects without enhancing radiation-inducible mEH and GST gene expression; and inhibition of radiation-inducible mEH and rGST gene expression in the vitamin C- and E-treated animals by dexamethasone was highly correlated with reduction in the survival rate and the mean survival time of gamma-irradiated animals.

Simultaneous oxygenation and perfusion imaging study of functional activity in primary visual cortex at different visual stimulation frequency: quantitative correlation between BOLD and CBF changes

A relationship between regional cerebral blood flow (CBF) and blood oxygenation level dependent (BOLD) changes in the primary visual cortex (V1) at varied visual stimulation frequency has been examined quantitatively using the multislice FAIR technique. A linear correlation in the common activation areas between functional BOLD and CBF maps was observed. This supports the hypothesis that the task-stimulated BOLD changes in microvasculature are correlated with the CBF changes that presumably reflect the degree of neuronal activity. The linear correlation coefficients for intrasubject comparisons are more significant than those for intersubject comparisons. This suggests that using intrasubject comparisons for quantitative studies of neuronal activity related to different task stimuli and task performances should be more reliable than using intersubject comparisons.

Cortical tissue-specific accumulation of the root-specific ns-LTP transcripts in the bean (Phaseolus vulgaris) seedlings

The characterization of a cDNA clone encoding non-specific lipid transfer protein (PvLTP, formerly named PVR3) in the roots of bean seedlings has been previously reported. In this study, we examined the temporal and spatial accumulation of PvLTP mRNA and the effect of the auxin naphthaleneacetic acid (NAA) on the accumulation of PvLTP mRNA during root development. In situ hybridization showed that accumulation of PvLTP mRNA is highly tissue-specific. Accumulation was detected in the cortical tissue, but not in other tissues of root, including the quiescent center and root cap. Within the cortical tissue, accumulation of PvLTP mRNA was developmentally regulated; accumulation of PvLTP mRNA was high in the cortical tissue of the proximal and ground meristem and declined as cortical tissue developed further. Since the appropriate distribution of auxin is an important factor responsible for the maintenance of root meristem organization. We examined effect of auxin on the accumulation of PvLTP mRNA in relation to the development of cortical tissue. In bean seedlings grown on medium supplemented with 5 microM NAA, morphological alternations, including radial root expansion and abnormal tissue organization in the root apical meristem, were observed. Only faint accumulation signals of PvLTP mRNA were observed in the cortical tissue of proximal meristem region, indicating that cortical tissue development was repressed by exogenous NAA. However, our results suggest that the change in accumulation of PvLTP mRNA is not direct regulatory effect but reflective effect of altered development of cortical tissue that was induced by exogenous NAA. The temporal and spatial accumulation of PvLTP mRNA indicates that PvLTP is a useful marker for the development of cortical tissue in the root tip in bean seedlings.

Effects of movement predictability on cortical motor activation

Humans have the ability to make motor responses to unpredictable visual stimuli, and do so as a matter of course on a daily basis. We used functional magnetic resonance imaging (fMRI) to examine the neural substrate of this behavior in six cortical motor areas. We found that five of these areas (premotor, cingulate, supplementary motor area, pre-supplementary motor area, and superior parietal lobule) showed increased activation in association with an unpredictable behavior compared to a predictable one; only the motor cortex remained unchanged. There was also a quantitative relation between the response time and functional activation in the premotor and cingulate cortex. There was less activation across all the motor areas with repetition of the motor tasks. With the exception of the pre-supplementary motor area, all areas were significantly lateralized, with a greater volume of activation in the hemisphere contralateral to the performing hand. In addition, a left hemisphere dominance was found in the activation of motor cortex and supplementary motor areas. Our results suggest that activation in motor areas is differentially and quantitatively related to higher order aspects of motor behavior such as movement predictability.

Radioprotective effects of 2-(allylthio)pyrazine an experimental chemopreventive agent: effects on detoxifying enzyme induction

2-(Allylthio)pyrazine (2-AP), which is effective in suppressing constitutive and inducible cytochrome P450 2E1 expression, exhibits hepatoprotective and chemopreventive effects. The radioprotective effects of 2-AP were examined in animals in association with the expression of microsomal epoxide hydrolase (mEH) and glutathione S-transferases (GSTs). 2-AP pretreatment (100 mg/kg/day, for 2 days) prior to total body irradiation (TBI) at the dose of 8 Gy increased the 30 day survival rate of mice to 91% from 48% in TBI alone. 2-AP caused an increase in the mean survival time of mice exposed to 9 Gy of TBI. Light microscopic examinations revealed that exposure of mice to 8 Gy of gamma-ray radiation resulted in hepatocyte degeneration in the surviving animals at day 1 through day 22 with certain extents of necrosis observed at early times, whereas 2-AP pretreatment protected the liver against ionizing radiation with no hepatic necrosis being observed. Mice irradiated at the dose of 8 Gy showed time-related decreases in the counts of WBC, RBC and platelet. 2-AP treatment, however, failed to protect the peripheral blood cells against gamma-irradiation and resulted in no improvement in the ratio of myeloid to erythroid bone marrow cells, as compared to TBI alone. Northern blot analysis revealed that exposure of mice to 8 Gy of TBI plus 2-AP exhibited greater mEH and mGSTA3 mRNA levels in the liver than those with TBI alone, although mGSTP1 mRNA level failed to be altered. Studies were also extended to determine the effects of 0.5 Gy gamma-irradiation in combination with 2-AP on the expression of hepatic mEH and GST genes in rats. Whereas mEH, rGSTA2, rGSTA3 and rGSTA5 mRNA levels were elevated 2- to 2.8-fold at 24 h after 2-AP treatment at the dose of 30 mg/kg, rats exposed to both 2-AP and 0.5 Gy of irradiation showed greater relative increases in the mRNAs. 2-AP enhanced the mEH and rGSTA2 gene expression to greater extents at day 1 after irradiation than after 3-5 consecutive daily treatment. The radiation-inducible mRNA levels of rGSTA3/5 and rGSTM1/2 were affected less by 2-AP pretreatment than were those of mEH and rGSTA2. These results demonstrate that 2-AP exhibits radioprotective efficacy against gamma-ray ionizing radiation in both mice and rats, which might be associated with enhanced expression of mEH and GST genes, but not with hematological improvement.

Purification of ornithine carbamoyltransferase from kidney bean (Phaseolus vulgaris L.) leaves and comparison of the properties of the enzyme from canavanine-containing and -deficient plants

Kidney bean (Phaseolus vulgaris L.) ornithine carbamoyltransferase (OCT; EC 2.1.3.3) was purified to homogeneity from leaf homogenates in a single-step procedure, using delta-N-(phosphonoacetyl)-L-ornithine-Sepharose 6B affinity chromatography. The 8540-fold-purified OCT exhibited a specific activity of 526 micromoles citrulline per minute per milligram of protein at 35 degrees C and pH 8.0. The enzyme represents approximately 0.01% of the total soluble protein in the leaf. The molecular mass of the native enzyme was approximately 109 kDa as estimated by Sephacryl S-200 gel filtration chromatography. The purified protein ran as a single band of molecular mass 36 kDa when subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and at a single isoelectric point of 6.6 when subjected to denaturing isoelectric focusing. These results suggest that the enzyme is a trimer of identical subunits. Among the tested amino acids, L-cysteine and S-carbamoyl-L-cysteine were the most effective inhibitors of the enzyme. The OCT of kidney bean showed a very low activity towards canaline. The OCTs of canavanine-deficient plants have very low canaline-dependent activities, but the OCTs of canavanine-containing plants showed high canaline-dependent activities. It was assumed that the substrate specificity of this enzyme determines the canavanine synthetic activity of the urea cycle.

Chemopreventive effects of 2-(allylthio)pyrazine on hepatic lesion, mutagenesis and tumorigenesis induced by vinyl carbamate or vinyl carbamate epoxide

2-(Allylthio)pyrazine (2-AP), synthesized for its possible use as a hepatoprotective agent, has been found to selectively inhibit rat hepatic cytochrome P450 2E1 (Kim et al., Biochem. Pharmacol., 53, 261-269, 1997), while it enhances the activities of phase II detoxification enzymes such as glutathione S-transferase and epoxide hydrolase. As part of a program in evaluating the chemopreventive potential of 2-AP, we have determined its effects on hepatotoxicity, mutagenicity and tumorigenicity of vinyl carbamate (VC), a prototypic hepatocarcinogen preferentially activated by P450 2E1 to the ultimate carcinogenic metabolite vinyl carbamate epoxide (VCO), which undergoes detoxification by glutathione conjugation and oxirane hydrolysis. Administration of 2-AP (100 mg/kg body wt) to male Sprague-Dawley rats by gavage, 2 days, 1 day and 4 h prior to VC or VCO, markedly ameliorated the hepatotoxicity of these compounds as determined by decreased serum aspartate aminotransferase and alanine aminotransferase activities. Furthermore, 2-AP pre-treatment significantly suppressed the VC-induced hepatocarcinogenesis in infant male B6C3F1 mice. In a separate experiment, the multiplicities of skin tumors formed in female ICR mice treated with 5.8 micromol of VC or VCO were inhibited 58 and 70%, respectively, by pre-treatment with 2-AP by oral administration. The mutational spectrum of ras-oncogene in papillomas was not altered by 2-AP pre-treatment. 2-AP also inhibited the mutagenicity of VC in the Salmonella-microsome assay. Taken together, these findings suggest that 2-AP is a potential chemopreventive agent.

On the characteristics of functional magnetic resonance imaging of the brain

In this review we discuss various recent topics that characterize functional magnetic resonance imaging (fMRI). These topics include a brief description of MRI image acquisition, how to cope with noise or signal fluctuation, the basis of fMRI signal changes, and the relation of MRI signal to neuronal events. Several observations of fMRI that show good correlation to the neurofunction are referred to. Temporal characteristics of fMRI signals and examples of how the feature of real time measurement is utilized are then described. The question of spatial resolution of fMRI, which must be dictated by the vascular structure serving the functional system, is discussed based on various fMRI observations. Finally, the advantage of fMRI mapping is shown in a few examples. Reviewing the vast number of recent fMRI application that have now been reported is beyond the scope of this article.