Transcript accumulation from the rpoS gene encoding a stationary-phase sigma factor in Pseudomonas chlororaphis strain O6 is regulated by the polyphosphate kinase gene

Polyphosphate levels are modulated by the actions of polyphosphate kinase, encoded by ppk, and exopolyphosphatase, encoded by ppx. The genes ppk and ppx are adjacent to each other in the genome of the root colonizer, Pseudomonas chlororaphis O6. A ppk-deficient mutant was more sensitive to oxidative stress than the wild-type and the ppx mutant. Transcripts from ppx increased as cultures matured from mid- to late-logarithmic and stationary phases, whereas abundance was greater for ppk in the late-logarithmic phase than in the stationary phase. Transcript accumulation from the rpoS gene, encoding the stationary-phase sigma factor RpoS, was decreased in the mid- and late-logarithmic and stationary phases in the ppk mutant. Thus, ppk regulates rpoS transcript accumulation in P. chlororaphis 06. However, mutations in either the ppk or ppx genes had no effect on induction of systemic resistance in plants colonized by P. chlororaphis O6.

Quantification and thickness correction of EFTEM phosphorus maps

We describe a method for correcting plural inelastic scattering effects in elemental maps that are acquired in the energy filtering transmission electron microscope (EFTEM) using just two energy windows, one above and one below a core edge in the electron energy loss spectrum (EELS). The technique is demonstrated for mapping low concentrations of phosphorus in biological samples. First, the single-scattering EELS distributions are obtained from specimens of pure carbon and plastic embedding material. Then, spectra are calculated for different specimen thicknesses t, expressed in units of the inelastic mean free path lambda. In this way, standard curves are generated for the ratio k0 of post-edge to pre-edge intensities at the phosphorus L2,3 excitation energy, as a function of relative specimen thickness t/lambda. Thickness effects in a two-window phosphorus map are corrected by successive acquisition of zero-loss and unfiltered images, from which it is possible to determine a t/lambda image and hence a background k0-ratio image. Knowledge of the thickness-dependent k0-ratio at each pixel thus enables a more accurate determination of the phosphorus distribution in the specimen. Systematic and statistical errors are calculated as a function of specimen thickness, and elemental maps are quantified in terms of the number of phosphorus atoms per pixel. Further analysis of the k0-curve shows that the EFTEM can be used to obtain reliable two-window phosphorus maps from specimens that are considerably thicker than previously possible.

Pinusolide and 15-methoxypinusolidic acid attenuate the neurotoxic effect of staurosporine in primary cultures of rat cortical cells

BACKGROUND AND PURPOSE

Apoptosis is a fundamental process required for neuronal development but also occurs in most of the common neurodegenerative disorders. In an attempt to obtain an anti-apoptotic neuroprotective compound from natural products, we isolated the diterpenoids, pinusolide and 15-MPA, from B. orientalis and investigated their neuroprotective activity against staurosporine (STS) -induced neuronal apoptosis. In addition, we determined the anti-apoptotic mechanism of these compounds in rat cortical cells.

EXPERIMENTAL APPROACH

Primary cultures of rat cortical cells injured by STS were used as an in vitro assay system. Cells were pretreated with pinusolide or 15-MPA before exposure to STS. Anti-apoptotic activities were evaluated by the measurement of cytoplasmic condensation and nuclear fragmentation. The levels of cellular peroxide, malondialdehyde (MDA) and [Ca(2+)]i, as well as the activities of superoxide dismutase (SOD) and caspase-3/7, were measured.

KEY RESULTS

Pinusolide and 15-MPA, at a concentration of 5.0 ìM, reduced the condensed nuclei and rise in [Ca(2+)]i that accompanies apoptosis induced by 100 nM STS. Pinusolide and 15-MPA also protected the cellular activity of SOD, an antioxidative enzyme reduced by STS insult. Furthermore, the overproduction of reactive oxygen species and lipid peroxidation induced by STS was significantly reduced in pinusolide and 15-MPA treated cells. In addition, pinusolide and 15-MPA inhibited STS-induced caspase-3/7 activation.

CONCLUSIONS AND IMPLICATIONS

These results show that pinusolide and 15-MPA protect neuronal cells from STS-induced apoptosis, probably by preventing the increase in [Ca(2+)]i and cellular oxidation caused by STS, and indicate that they could be used to treat neurodegenerative diseases.

Inhibitory effect of C-type natriuretic peptide on L-type calcium channel currents in gastric antral myocytes of guinea pigs

The role of C-type natriuretic peptide (CNP) in the gastrointestinal tract is still unclear. This study was designed to investigate the effect of CNP on barium current (I(Ba)) through the L-type calcium channel in gastric antral myocytes of guinea pigs. The whole-cell patch clamp technique was performed in gastric antral myocytes isolated by collagenase in guinea pigs. CNP significantly inhibited I(Ba) in a dose-dependent manner at the concentrations of 0.001, 0.01, and 0.1 micromol/l, CNP inhibited I(Ba) to 81.56 +/- 2.48 %, 73.64 +/- 3.65 %, and 57.77 +/- 4.93 % of control at 0 mV, respectively. The values of steady-state half-inactivation voltage (33.6 +/- 2.6 mV and 33.8 +/- 3.4 mV, in control and CNP groups, respectively) or the half-activation voltage (-12.6 +/- 2.2 mV and 12.4 +/- 1.8 mV) of I(Ba) were not significantly changed (p > 0.05, n = 6). 8-br-cGMP (1 mmol/l) mimicked the effect of CNP on I(Ba), and the peak current of I(Ba) was inhibited from -403.84 +/- 61.87 pA to 318.94 +/- 67.17 pA (p < 0.05, n = 5). In the presence of LY83583 (0.1 micromol/l), a nonspecific inhibitor of guanylate cyclase, CNP (0.1 micromol/l)-induced inhibition of I(Ba) was partially blocked (n = 13, p < 0.05 ). However, when the cell was pretreated with zaprinast (0.1 micromol/l), an inhibitor of cyclic guanosine monophosphate (cGMP) sensitive phosphoesterase, the inhibitory effect of CNP on I(Ba) was significantly potentiated (n = 11, p < 0.05). KT5823 (1 micromol/l), a cGMP-dependent protein kinase (PKG) inhibitor, almost completely blocked CNP-induced inhibition of I(Ba). The results suggested that CNP can inhibit L-type calcium channel currents, and the inhibitory effect is mediated by pGC-cGMP-PKG-dependent signal pathway in gastric antral myocytes of guinea pigs.

Effect of β-alanine administration on carbon tetrachloride-induced acute hepatotoxicity

Mice were supplemented with beta-alanine (3%) in drinking water for one week. beta-Alanine intake reduced hepatic taurine levels, but elevated cysteine levels significantly. Hepatotoxicity of CCl4 in mice fed with beta-alanine was decreased as determined by changes in serum enzyme activities. Hepatic glutathione and taurine concentrations after CCl4 challenge were increased markedly by beta-alanine intake. The enhanced availability of cysteine for synthesis of glutathione and/or taurine appears to account for the hepatoprotective effects of beta-alanine against CCl4-induced liver injury.

Comparison between high and low molecular weight hyaluronates in knee osteoarthritis patients: open-label, randomized, multicentre clinical trial

Efficacy and safety of high and low molecular weight hyaluronates in knee osteoarthritis patients were compared in a randomized, open-label trial. Patients in the high molecular weight hyaluronate group were treated once weekly for 3 weeks and in the low molecular weight group once weekly for 5 weeks. We evaluated weight-bearing pain, degree of flexion, swelling and knee tenderness; frequency and amount of rescue medication; patient and investigator global assessment of pain, and safety over 12 weeks after final injection of study medication. Significant improvements in pain and WOMAC-Likert scores were observed in both groups, but not between groups. Knee joint pain improvement was noted in both groups by patients and investigators during follow-up. Close correlation was observed between patient- and investigator-reported data. There was no significant difference in side-effects between the groups. In conclusion, the efficacy and safety of high and low molecular weight hyaluronate are similar.

Caveolin-1 is down-regulated and inversely correlated with HER2 and EGFR expression status in invasive ductal carcinoma of the breast

AIMS

To evaluate the caveolin-1 status of invasive ductal carcinoma and its correlation with other important parameters of breast carcinogenesis. Caveolin-1, the main structural protein of caveolae, is involved in the regulation of several intracellular signalling pathways and also functions as a tumour suppressor in breast carcinogenesis.

METHODS AND RESULTS

One hundred and thirty cases of invasive ductal carcinomas with matched normal breast tissue were evaluated immunohistochemically for caveolin-1 expression. Using a tissue microarray, caveolin-1 expression was also correlated with the expression of other antigens such as eostrogen receptor, progesterone receptor, epidermal growth factor receptor (EGFR), HER2, beta-catenin, E-cadherin, p53, Ki67 and with clinicopathological parameters. Immunohistochemical results showed strong expression of caveolin-1 in all normal breast epithelial cells, but a reduction of caveolin-1 expression in 56 cases (43.1%) of invasive ductal carcinoma. Furthermore, a statistically significant inverse correlation between caveolin-1 and EGFR and HER2 was noted (P < 0.001).

CONCLUSIONS

Our results indicate a reduction in caveolin-1 expression in invasive ductal carcinoma of the breast, which supports in vitro studies of its role as a tumour suppressor. Caveolin-1 also shows an inverse correlation with EGFR and HER2, which fits with its function as a negative regulator of signal transduction.

Intrathecal clonidine does not reduce post-spinal shivering

BACKGROUND

After general or epidural anesthesia, clonidine is known to be effective in suppressing established shivering. The aim of this study was to assess the preventive effect of intrathecal clonidine on post-spinal shivering compared with intravenous (i.v.) clonidine.

METHODS

One hundred and fifty patients scheduled for orthopedic surgery were randomly allocated into three groups to receive either 1 microg/kg clonidine i.v. (IV group) or the same volume of isotonic saline (control and IT groups) at 5 min before spinal anesthesia. Spinal anesthesia was performed with 12-15 mg hyperbaric bupivacaine 0.5% plus either 1 ml of saline (control and IV groups) or 150 microg clonidine (IT group). Shivering was evaluated for a period of 90 min and graded as none, mild, moderate, and severe.

RESULTS

Twenty patients (40%) in the control group and 17 patients (34%) in the IT group showed shivering compared with four (8%) in the IV group. Patients with moderate-to-severe shivering were only seen in the control and IT group, and the maximal intensity of shivering was not different between the two groups. Patients in the IV group were significantly more sedated than the other groups.

CONCLUSIONS

The intrathecal administration of clonidine 150 microg fails to prevent post-spinal shivering; by contrast, we have confirmed that i.v. clonidine 1 microg/kg is an effective method to prevent shivering in patients undergoing spinal anesthesia for orthopedic surgery.

Production of N-acetyl-beta-D-glucosamine from chitin by Aeromonas sp. GJ-18 crude enzyme

A bacterium, GJ-18, having strong chitinolytic activity was isolated from coastal soil. The isolated strain was identified as Aeromonas sp. by morphological and biochemical properties along with 16S rRNA gene sequence. The crude chitinolytic activity of culture supernatants was maximal on the 5th day of culture. Below 45 degrees C, chitin was effectively hydrolyzed to N-acetyl-beta-D-glucosamine (GlcNAc) by Aeromonas sp. GJ-18 crude enzymes, but hydrolysis decreased markedly above 50 degrees C. The optimum pH for enzyme activity was 5.0. TLC and HPLC analysis revealed that, below 45 degrees C, the major reaction product was GlcNAc with a small amount of (GlcNAc)(2) and (GlcNAc)(3), whereas above 50 degrees C the major product was (GlcNAc)(2). When swollen chitin (100 mg) was incubated with crude enzyme preparations (10 U) at 40 degrees C, chitin was hydrolyzed to 83.0 and 94.9% yield of GlcNAc within 5 and 9 days, respectively.

Flavonol glycosides with free radical-scavenging activity of Saururus chinensis

An activity-guided fractionation procedure was used to identify the antioxidative components of the aerial parts of Saururus chinensis. The antioxidant activity was investigated with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical- and superoxide anion-scavenging assays. Three active compounds (flavonol glycosides) were identified.

Mycelial culture of Phellinus linteus protects primary cultured rat hepatocytes against hepatotoxins

Hepatoprotective activity of Phellinus linteus was studied using H(2)O(2)- or galactosamine-injured primary cultures of rat hepatocytes as screening systems. The methanolic extract of the mycelial culture of Phellinus linteus significantly protected against hepatotoxins-induced toxicity in primary cultured rat hepatocytes as seen from the decreased level of glutamic pyruvic transaminase released from the injured hepatocytes. The methanolic extract of the mycelial culture of Phellinus linteus was subsequently fractionated with n-hexane, ethyl acetate, n-butanol and water. Among these fractions, 100 microg/mL of the ethyl acetate fraction was the most active one. The relative protections were 68.9 +/- 5.3% in H(2)O(2)-injured hepatocytes and 46.8 +/- 3.9% in galactosamine-injured hepatocytes, respectively. The ethyl acetate fraction appeared to maintain the glutathione level which was decreased by the treatment of H(2)O(2) or galactosamine and restored the level of RNA synthesis more than two times compared to galactosamine-injured hepatocytes. These results suggest that the ethyl acetate fraction of the mycelial culture of Phellinus linteus protects hepatocytes from H(2)O(2)- or galactosamine-induced injury by maintaining hepatic glutathione level and RNA synthesis as well.

Sequence variation in the gene encoding the major capsid protein of Korean fish iridoviruses

Ten iridoviruses were isolated from cultured fish from various regions in Korea; 7 from rock bream, 1 from red sea bream, 1 from sea bass, and 1 from rockfish. The full open-reading frame (ORF) encoding the major capsid protein (MCP) (1362 bp) from ten iridoviruses were sequenced and the nucleotide sequences were phylogenetically analyzed. Phylogenetic analysis revealed that the ten Korean isolates were classified into one cluster. However, their sequences were not identical and, based on the nucleotide sequence variation, they could be further divided into two subgroups. While nine Korean isolates were similar to the Japanese isolate red sea bream iridovirus (RSIV), one isolate was distinct from other iridovirus isolates. These results suggest that a diversity of iridoviruses exist in Korea and that a new variant strain has emerged.

The effects of cryoanalgesia combined with thoracic epidural analgesia in patients undergoing thoracotomy

This study was performed to evaluate the effects of cryoanalgesia combined with thoracic epidural analgesia on pain and respiratory complications in patients undergoing thoracotomy. Ninety patients were prospectively randomised to epidural analgesia alone (n = 45) or epidural analgesia and cryoanalgesia combined (n = 45). We monitored the use of rescue pain medication and changes in forced vital capacity and forced expired volume in 1 s, and recorded pain and opioid-related side-effects during the immediate postoperative period. The incidence of post-thoracotomy pain and numbness were also assessed up to the sixth month after surgery. Cryoanalgesia combined with thoracic epidural analgesia was associated with earlier recovery in pulmonary function, less pain during movement and a lower daily requirement for rescue analgesia one week after surgery. However, the combination of cryoanalgesia and epidural analgesia failed to decrease the incidence of long-term pain and numbness. In view of its associated long-term morbidity, cryoanalgesia combined with thoracic epidural analgesia is not recommended for patients undergoing thoracotomy.

Ap-let neurons--a peptidergic circuit potentially controlling ecdysial behavior in Drosophila

Here we describe a novel set of peptidergic neurons conserved throughout all developmental stages in the Drosophila central nervous system (CNS). We show that a small complement of 28 apterous-expressing cells (Ap-let neurons) in the ventral nerve cord (VNC) of Drosophila larvae co-express numerous gene products. The products include the neuroendocrine-specific bHLH regulator called Dimmed (Dimm), four neuropeptide biosynthetic enzymes (PC2, Fur1, PAL2, and PHM), and a specific dopamine receptor subtype (dDA1). For the PC2, Fur1, and PAL2 enzymes, and for the dDA1 receptor, this neuronal pattern represents the vast majority of their total expression in the VNC. In addition, while Dimm and PHM are present in the peritracheal Inka cells in larvae, pupae, and adults, Ap, PC2, Fur1, PAL2, and dDA1 are not. PC2, PAL2, and DA1 receptor expression were all controlled by both dimm and ap. Previous genetic analysis of animals deficient in PC2 revealed an abnormal larval ecdysis phenotype. Together, these data support the hypothesis that the small cohort of Ap-let interneurons regulates larval ecdysis behavior by secretion of an unidentified amidated peptide(s). This hypothesis further predicts that the production of the Ap-let neuropeptide(s) is dependent on each of four specific enzymes, and that a certain aspect(s) of its production and/or release is regulated by dopamine input.

Competitiveness in root colonization by Pseudomonas putida requires the rpoS gene

The rpoS gene in Pseudomonas putida was essential for plant root colonization under competitive conditions from other microbes. The RpoS- mutant survived less well than the wild-type strain in culture medium, and unlike the wild-type, failed to colonize the roots in a peat matrix containing an established diverse microflora. The RpoS-deficient P. putida isolate was generated by insertion of a glucuronidase-npt cassette into the rpoS gene. The RpoS mutant had dose-dependent increased sensitivity to oxidative stress and produced Mn-superoxide dismutase activity earlier than the parent. While extracts from wild-type P. putida stationary-phase cells contained three isozymes of catalase (CatA, CatB, and CatC), the sigma38-deficient P. putida lacked CatB. These results are consistent with previous findings that CatB is induced in stationary-phase.

Efficacy of Prophylactic Ondansetron in a Patient-Controlled Analgesia Environment

We conducted a prospective, randomized, double-blind, placebo-controlled trial to examine the efficacy of prophylactic ondansetron on post-operative nausea and vomiting (PONV) during opioid patient-controlled analgesia (PCA). In total, 374 patients using opioid PCA, but otherwise considered to be low risk for PONV, were randomly allocated to ondansetron (4 mg given intravenously and 16 mg added into the PCA pump) or saline (control group). PONV was evaluated in terms of nausea graded on a visual analogue scale, and the number of patients who experienced emetic episodes or needed rescue anti-emetics in the 48-h post-operative period. Patient satisfaction for PCA was scored at the end of the evaluation period. The only difference between the two groups was the higher number of headaches in the ondansetron group. In patients using opioid PCA, but with no other high risk factors for PONV, prophylactic ondansetron does not have any clinical benefit.

Alterations in hepatic metabolism of sulfur-containing amino acids induced by ethanol in rats

Alterations in hepatic metabolism of S-amino acids were monitored over one week in male rats treated with a single dose of ethanol (3 g/kg, ip). Methionine and S-adenosylhomocysteine concentrations were increased rapidly, but S-adenosylmethionine, cysteine, and glutathione (GSH) decreased following ethanol administration. Activities of methionine adenosyltransferase, cystathionine gamma-lyase and cystathionine beta-synthase were all inhibited. gamma-Glutamylcysteine synthetase activity was increased from t = 8 hr, but GSH level did not return to control for 24 hr. Hepatic hypotaurine and taurine levels were elevated immediately, but reduced below control in 18 hr. Changes in serum and urinary taurine levels were consistent with results observed in liver. Cysteine dioxygenase activity was increased rapidly, but declined from t = 24 hr. The results show that a single dose of ethanol induces profound changes in hepatic S-amino acid metabolism, some of which persist for several days. Ethanol not only inhibits the cysteine synthesis but suppresses the cysteine availability further by enhancing its irreversible catabolism to taurine, which would play a significant role in the depletion of hepatic GSH.

Hepatoprotective effect of baicalin, a major flavone from Scutellaria radix, on acetaminophen-induced liver injury in mice

The protective effects of baicalin (BA), a major flavone from Scutellaria radix, on acetaminophen (AP)-induced hepatotoxicity and the possible mechanism(s) of its protective action were investigated in mice. Treatment with BA (300 mg/kg, p.o.) 0.5 h after AP administration significantly prevented an increase in plasma alanine aminotransferase and aspartate aminotransferase activities and AP-induced hepatic necrosis, and also reduced AP-induced mortality from 43% to 0%. In addition, oral treatment with BA significantly prevented AP-induced depletion of glutathione (GSH) contents. However, BA treatment, by itself, did not affect hepatic GSH contents. The effect of BA on the cytochrome P450 2E1 (CYP2E1), the major isozyme involved in AP bioactivation, was investigated. Oral treatment of mice with BA resulted in a significant decrease in AP-induced CYP2E1 activity together with its inhibition of AP-induced CYP2EI expression. These results show that the hepatoprotective effects of BA against AP overdose may be due to its ability to block the bioactivation of AP by inhibiting CYP2E1 expression.

Comparative bioavailability of silibinin in healthy male volunteers

AIM

To study a comparative bioavailability of Liverman capsule to Legaion capsule and Silymarin tablet (which contain silibinin) in 24 healthy volunteers.

VOLUNTEERS AND METHODS

Twenty-four healthy male Korean volunteers received each medicine at the silibinin dose of 120 mg in a 3 x 3 crossover study. There was a 1-week washout period among the doses. Plasma concentrations of silibinin were monitored by a high-performance liquid chromatography for over a period of 12 hours after the administration. AUCinf (the area under the plasma concentration-time curve from time zero to time infinity) was calculated by the trapezoidal rule extrapolation method. Cmax (maximum plasma drug concentration) and tmax (time to reach a Cmax) were compiled from the plasma concentration-time data. Analysis of variance was carried out using logarithmically transformed AUCinf, AUC(0-12h), and Cmax and untransformed tmax.

RESULTS

After an oral administration of Liverman capsule, the pharmacokinetic parameters of silibinin, such as AUC(0-12h) (5.59, 4.24 and 13.9 microg/ml x h for Legalon capsule, Silymarin tablet and Liverman capsule, respectively) and AUCinf (6.00, 4.63 and 15.1 microg/ml x h) were significantly greater, Cmax (1.33, 1.13 and 6.04 microg/ml) was significantly higher and tmax (1.83, 2.10 and 0.875 h) was significantly faster than those after Legalon capsule and Silymarin tablet.

CONCLUSION

These results indicate that the absorption and the extent of relative oral bioavailability of silibinin after Liverman capsule were significantly faster and greater, respectively, than those after Legalon capsule and Silymarin tablet.

Gene expression analysis in cucumber leaves primed by root colonization with Pseudomonas chlororaphis O6 upon challenge-inoculation with Corynespora cassiicola

Root colonization by Pseudomonas chlororaphis O6, a non-pathogenic rhizobacterium, induced systemic resistance in cucumber against target leaf spot caused by Corynespora cassiicola. A cDNA library was constructed using mRNA extracted from cucumber leaves 12 h after inoculation with C. cassiicola, using plants colonized by O6. To identify genes involved in O6-mediated induced systemic resistance (ISR), we employed a subtractive hybridization method using mRNAs extracted from pathogen-challenged cucumber leaves of plants lacking colonization. Differential screening of the cDNA library led to the isolation of six distinct genes encoding a GTP binding protein, a 60S ribosomal protein, a hypersensitive-induced reaction protein, a ubiquitin extension protein, a pyridine nucleotide-disulfide oxidoreductase, and a signal recognition particle receptor. Expression of these genes was not induced by O6 colonization alone. Rather, transcript accumulation of these genes increased significantly faster and stronger in the O6 colonized than in non-colonized plants after challenge infection. Therefore, O6-mediated ISR may be associated with an enhanced capacity for the rapid and effective activation of cellular defence responses after challenge inoculation.

Octopamine receptor OAMB is required for ovulation in Drosophila melanogaster

Octopamine is a major monoamine in invertebrates and affects many physiological processes ranging from energy metabolism to complex behaviors. Octopamine binds to receptors located on various cell types and activates distinct signal transduction pathways to produce these diverse effects. We previously identified one of the Drosophila octopamine receptors named OAMB that produces increases in cAMP and intracellular Ca2+ upon ligand binding. It is expressed at high levels in the brain. To explore OAMB's physiological roles, we generated deletions in the OAMB locus. The resultant oamb mutants were viable without gross anatomical defects. The oamb females displayed normal courtship and copulation; however, they were impaired in ovulation with many mature eggs retained in their ovaries. RT-PCR, in situ hybridization, and expression of a reporter gene revealed that OAMB was also expressed in the thoracicoabdominal ganglion, the female reproductive system, and mature eggs in the ovary. Moreover, analysis of various alleles pinpointed the requirement for OAMB in the body, but not in the brain, for female fecundity. The novel expression pattern of OAMB and its genetic resource described in this study will help advance our understanding on how the neuromodulatory or endocrine system controls reproductive physiology and behavior.

Subphrenic bronchogenic cyst mimicking a juxtahepatic solid lesion

Most bronchogenic cysts occur in the mediastinum. However, they may be found near any organ derived from the embryonic foregut, even in the extrathoracic region. We report a case of subphrenic bronchogenic cyst that was initially confused with a solid lesion because of its unusual location and atypical appearance on ultrasonography, computed tomography, and magnetic resonance imaging.