Dynamic CT of portal hypertensive gastropathy: significance of transient gastric perfusion defect sign

AIM

To evaluate the "transient gastric perfusion defect" sign as a way of diagnosing portal hypertensive gastropathy (PHG) on multidetector computed tomography (CT).

MATERIALS AND METHODS

Ninety-two consecutive patients with cirrhosis underwent three-phase CT and endoscopy. Endoscopy was performed within 3 days of the CT examination. As controls, 92 patients without clinical evidence of chronic liver diseases who underwent CT and endoscopy were enrolled; the findings at endoscopy were used as a reference standard for patients with PHG. Two radiologists who were unaware of the results of the endoscopy retrospectively interpreted the CT images. PHG was diagnosed on dynamic CT if the transient gastric perfusion defect sign was present. The transient gastric perfusion defect was defined as the presence of transient, segmental or subsegmental hypo-attenuating mucosa in the fundus or body of the stomach on hepatic arterial imaging that returned to normal attenuation on portal venous or equilibrium-phase imaging. The frequency of the transient gastric perfusion defect sign was compared between these two groups using Fisher's exact test. The frequency, sensitivity, specificity, positive predictive values, and negative predictive values of the transient gastric perfusion defect sign were also compared between patients with PHG and without PHG in the cirrhosis group.

RESULTS

Nine patients of 92 patients with cirrhosis were excluded because of previous procedure or motion artifact; the remaining 83 patients with cirrhosis were evaluated. In the cirrhosis group, 40 (48.1%) of 83 patients showed the transient gastric perfusion defect sign. In the control group, none of the 92 patients showed the transient gastric perfusion defect sign. In the cirrhotic group, the frequency of the transient gastric perfusion defect sign was significantly higher in the patients with PHG (75%, 36/48) than in patients without PHG (11.4%, 4/35). The sensitivity, specificity, positive predictive values, and negative predictive values of the sign for CT diagnosis of PHG in the cirrhosis group were 75, 88.6, 90, and 72.1% respectively.

CONCLUSION

The transient gastric perfusion defect sign could be used as a relatively specific sign of PHG in patients with cirrhosis.

A Bedside System for Combined RNA and PAC in Heart Failure

Assessment of right ventricular (RV) function is inherently more difficult than left ventricular (LV) function because of the unusual geometry. We have developed a bedside system that integrates a multiwire gamma camera (MWGC) with pulmonary artery catheterization (PAC). This system permits simultaneous acquisition of first pass radionuclide angiography (RNA) images and pressure data from the catheter as well as acquisition of thermodilution data. The system provides highly accurate quantitative measurement of RV and LV ejection fractions, which are indicators of systolic function. This combined RNA-PAC technique permits simple and accurate calculation of both right and left ventricular volume of the ventricular cavity by dividing stroke volume by ejection fraction. Because these data are based on measurements that are non-geometric, this technique for volume measurement is extremely accurate and far surpasses any of the currently available modalities. The system is capable of generating curves relating RV volumes and pressures, which are critical in evaluation of heart failure (HF) patients. Clinical studies were successfully performed on 25 patients, and the results were of high quality and were reproducible. In summary, the system for the first time provides a novel method of generation of RV pressure-volume loops, using a hybrid method of right heart catheterization and RNA.

Phenylalkyl 1,2-diamines as sigma receptor ligands: The discovery of novel anti-depressant agents

This article focuses on the study of phenylalkyl 1,2-diamines as sigma-receptor ligands for the discovery of antidepressant agents. We synthesized N-chain substituted phenylalkyl 1,2-diamine derivatives. Phenylalkyl 1,2-diamines are one of the most important class of therapeutical medicines useful in managing central nervous system diseases and have been used mainly to treat obesity, narcolepsy, minimal brain dysfunction, and mild depression. In the present study, we found that phenylalkyl 1,2-diamine and amide compounds were strongly bound to the sigma-receptors and showed a potent activity of mice forced swimming test. Our article, after briefly outlining the background and nature of sigma-receptor ligands, explores the antidepressant activity of phenylalkyl 1,2-diamines.

Hepatic corticosteroid-binding globulin (CBG) messenger RNA expression and plasma CBG concentrations in young pigs in response to heat and social stress1,2

Plasma cortisol, porcine corticosteroid-binding globulin (pCBG), hepatic CBG expression, and other physiological and behavioral measures of stress were studied in pigs in response to elevated temperature in conjunction with establishing a social hierarchy. Twenty-four crossbred pigs were weaned at 25 d of age (three or six pigs from six sows) and housed in littermate groups at 23 +/- 2 degrees C. At 57 d of age (d 0), animals were weighed and placed under general anesthesia for collection of blood (10 mL) and liver (approximately 100 mg) samples. On d 1, three unacquainted pigs of similar BW (23 +/- 1 kg) from different litters were allotted to each of eight nursery pens within two environmentally controlled rooms (12 pigs per room). From d 1 to 7, one room was maintained at 23 +/- 2 degrees C (CON) and the other at 33 +/- 2 degrees C (HEAT). Both rooms were kept at 23 +/- 2 degrees C from d 8 to 14. Animals were videotaped for 72 h beginning on d 1 and 8 to document behavioral changes in response to room temperature. The social hierarchy of pigs within each pen was based on fight activity recorded on d 1 to 3. Blood and liver tissue were collected again on d 7 and 14. The ADG for HEAT pigs increased (P < 0.05) over d 8 to 14 compared with d 1 to 7. In contrast to CON pigs, HEAT pigs displayed increased (P < 0.01) drinking but decreased feeding and lying in contact with other pigs from d 1 to 3, and similar drinking and feeding but increased (P < 0.01) lying with contact behaviors from d 8 to 10. With the exception of subordinate pigs exhibiting less (P < 0.05) frequent standing/walking behavior than the dominant or intermediate pigs on d 1 to 3, frequency of behaviors for both recorded time periods did not differ among pigs due to social status, regardless of treatment. The concentration of plasma haptoglobin in HEAT pigs on d 7 compared with d 0 increased (467 vs. 763 mg/L; P < 0.05), whereas cortisol and pCBG decreased (274 vs. 235 nmol/L and 11.4 vs. 9.9 mg/L, respectively; P < 0.05) as a result of treatment. The free cortisol index (total cortisol/pCBG) was greater (P < 0.05) in HEAT pigs on d 14 than on d 0 or 7. Hepatic CBG mRNA level was not affected by treatment. On d 14, HEAT pigs had plasma cortisol, pCBG, and haptoglobin concentrations similar to those of CON pigs. These results indicate that measured behavioral and physiological responses were not related to social status, and decreased circulating levels of cortisol and pCBG in pigs following a 7-d exposure to elevated temperature may not be determined by hepatic CBG mRNA expression.

Which types of stent, uncovered or covered, should be used in gastric outlet obstructions?

BACKGROUND

Self-expandable metallic stents (SEMS) have been widely used in inoperable malignant gastric outlet obstructions, but stent obstructions caused by tumor ingrowth and migration are a major problem of SEMS. The aims of this study were to assess the rate of stent restenosis, to identify lesion characteristics related to early restenosis by tumor ingrowth, and, in particular, to find suitable patient groups for uncovered or covered stents at first implantation.

METHODS

Forty-nine patients were reviewed: stomach cancer in 34 patients, primary duodenal cancer in 3 patients, pancreatic cancer in 5 patients, and common bile duct cancer in 7 patients. In principle, uncovered stents were initially placed at the time when obstruction symptoms occurred and the endoscope would not pass through. Stent obstruction due to tumor ingrowth within 4 weeks after the first stent implantation was regarded as early stent restenosis.

RESULTS

Technical success was seen in 49/49 patients (100%). Migration did not occur. Stent obstructions caused by tumor overgrowth were found in 2/49 patients (4.1%) after 1 month. Stent obstructions caused by tumor ingrowth occurred in 14/49 patients (28.5%), and 7 of them (14.3%) were found to have early restenosis. The only statistically significant factor for early restenosis was stenosis site, and early restenosis was more frequent in the postoperative anastomosis site in the current study; a) 2/18 antropyloric obstructions (11.1%), b) 1/15 pyloric and duodenal bulb obstructions (6.7%), c) 0/10 duodenal second portion obstructions (0%), and d) 4/6 postoperative anastomosis site obstructions (66.7) (P < 0.05, 95% CI 0.003-0.005).

CONCLUSIONS

Uncovered stents are technically feasible and effective for most malignant gastric outlet obstructions. However, because of frequent early restenosis among patients with postoperative anastomosis site obstructions, the placement of covered or simultaneous dual stents to prevent early restenosis should be considered when stenting postoperative anastomosis site obstructions.

Partial nucleotide sequence of the porcine corticosteroid-binding globulin (CBG) cDNA and specification of CBG expression sites in postnatal pigs

The purpose of this study was to develop a porcine CBG cDNA probe in order to examine the porcine CBG mRNA expression in major tissues from the postnatal pig. The reverse transcriptase-polymerase chain reaction (RT-PCR) was conducted to develop the porcine CBG cDNA probe using total RNA extracted from liver of 40-day-old pig. The RT-PCR product was subcloned into the pGEM vector (Promega, Madison, WI) and subjected to restriction enzyme treatments and DNA sequencing. Northern blot analysis was conducted using total RNA extracted from samples (approximately 200 mg) of liver, lung, kidney, and whole adrenal tissue that were collected from pigs on day 3 (n = 2) or day 40 (n = 2) postpartum. A 500 bp partial porcine CBG cDNA encoded 166 amino acids and had 83, 78, and 77% homology to a 494-nucleotide sequence of CBG from sheep, human, and rabbit, respectively. The deduced peptide sequence of the partial porcine CBG showed 77, 62, 60, and 51% homology to sheep, human, rabbit, and rat CBG sequences, respectively. An approximately 1.53 kb CBG mRNA was detected only in the liver tissue. In conclusion, the development of a partial CBG cDNA for swine makes it possible to study the ontogeny and the regulation of CBG synthesis at the molecular level and, based on tissues examined in this study, the liver appears to be the primary source of CBG biosynthesis in the postnatal pig.

Life on carbon monoxide: X-ray structure of Rhodospirillum rubrum Ni-Fe-S carbon monoxide dehydrogenase

A crystal structure of the anaerobic Ni-Fe-S carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum has been determined to 2.8-A resolution. The CODH family, for which the R. rubrum enzyme is the prototype, catalyzes the biological oxidation of CO at an unusual Ni-Fe-S cluster called the C-cluster. The Ni-Fe-S C-cluster contains a mononuclear site and a four-metal cubane. Surprisingly, anomalous dispersion data suggest that the mononuclear site contains Fe and not Ni, and the four-metal cubane has the form [NiFe(3)S(4)] and not [Fe(4)S(4)]. The mononuclear site and the four-metal cluster are bridged by means of Cys(531) and one of the sulfides of the cube. CODH is organized as a dimer with a previously unidentified [Fe(4)S(4)] cluster bridging the two subunits. Each monomer is comprised of three domains: a helical domain at the N terminus, an alpha/beta (Rossmann-like) domain in the middle, and an alpha/beta (Rossmann-like) domain at the C terminus. The helical domain contributes ligands to the bridging [Fe(4)S(4)] cluster and another [Fe(4)S(4)] cluster, the B-cluster, which is involved in electron transfer. The two Rossmann domains contribute ligands to the active site C-cluster. This x-ray structure provides insight into the mechanism of biological CO oxidation and has broader significance for the roles of Ni and Fe in biological systems.

Redox-dependent activation of CO dehydrogenase from Rhodospirillum rubrum

Studies of initial activities of carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum show that CODH is mostly inactive at redox potentials higher than -300 mV. Initial activities measured at a wide range of redox potentials (0--500 mV) fit a function corresponding to the Nernst equation with a midpoint potential of -316 mV. Previously, extensive EPR studies of CODH have suggested that CODH has three distinct redox states: (i) a spin-coupled state at -60 to -300 mV that gives rise to an EPR signal termed C(red1); (ii) uncoupled states at <-320 mV in the absence of CO(2) referred to as C(unc); and (iii) another spin-coupled state at <-320 mV in the presence of CO(2) that gives rise to an EPR signal termed C(red2B). Because there is no initial CODH activity at potentials that give rise to C(red1), the state (C(red1)) is not involved in the catalytic mechanism of this enzyme. At potentials more positive than -380 mV, CODH recovers its full activity over time when incubated with CO. This reductant-dependent conversion of CODH from an inactive to an active form is referred to hereafter as "autocatalysis." Analyses of the autocatalytic activation process of CODH suggest that the autocatalysis is initiated by a small fraction of activated CODH; the small fraction of active CODH catalyzes CO oxidation and consequently lowers the redox potential of the assay system. This process is accelerated with time because of accumulation of the active enzyme.

Redox-dependent CO2 reduction activity of CO dehydrogenase from Rhodospirillum rubrum

Carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum catalyzes both the oxidation of CO and the reduction of CO(2). Studies of the redox dependence of CO(2) reduction by R. rubrum CODH show that (1) CODH is unable to catalyze CO(2) reduction at potentials greater than -300 mV; (2) the maximum activity is observed at potentials less than -480 mV; and (3) the midpoint potential (E(m)) of the transition from minimum to maximum CO(2) reduction activity occurs at approximately -339 mV. These results indicate that the C(red1) state of R. rubrum CODH (E(m) = -110 mV; g(zyx)() = 2.03, 1.88, 1.71) is not competent to reduce CO(2). Nernst analyses suggest that the reduction of CODH from the C(red1) state to the CO(2)-reducing form (C(unc), g(zyx)() = 2.04, 1.93, 1.89; E < approximately -300 mV) of the enzyme is a one-electron process. For the entire redox range, viologens stimulate CO(2) reduction by CODH more than 50-fold, and it is proposed that viologens accelerate the redox equilibration of redox buffers and [Fe(4)S(4)](B) during catalysis.

Evidence for a ligand CO that is required for catalytic activity of CO dehydrogenase from Rhodospirillum rubrum

Radiolabeling studies support the existence of a nonsubstrate CO ligand (CO(L)) to the Fe atom of the proposed [FeNi] cluster of carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum. Purified CODH has variable amounts of CO(L) dissociated depending on the extent of handling of the proteins. This dissociated CO(L) can be restored by incubation of CODH with CO, resulting in a 30-40% increase in initial activity relative to as-isolated purified CODH. A similar amount of CO(L) binding is observed when as-isolated purified CODH is incubated with (14)CO: approximately 0.33 mol of CO binds per 1 mol of CODH. Approximately 1 mol of CO was released from CO-preincubated CODH upon denaturation of the protein. No CO could be detected upon denaturation of CODH that had been incubated with cyanide. CO(L) binds to both Ni-containing and Ni-deficient CODH, indicating that CO(L) is liganded to the Fe atom of the proposed [FeNi] center. Furthermore, the Ni in the CO(L)-deficient CODH can be removed by treatment with a Ni-specific chelator, dimethylglyoxime. CO preincubation protects the dimethylglyoxime-labile Ni, indicating that CO(L) is also involved in the stability of Ni in the proposed [FeNi] center.

Long-term outcome of patients with intermediate-risk exercise electrocardiograms who do not have myocardial perfusion defects on radionuclide imaging

BACKGROUND

The appropriate management of patients with intermediate-risk Duke treadmill scores is not established. The purpose of this study was to determine the long-term risk of subsequent cardiovascular events in patients with an intermediate-risk treadmill score who do not have myocardial perfusion defects on radionuclide imaging.

METHODS AND RESULTS

The existing databases of the nuclear cardiology laboratories of 4 academic institutions were searched retrospectively. A total of 4649 patients were identified who had intermediate-risk Duke treadmill scores (-10 to 4), normal or near-normal exercise single photon-emission computed tomographic myocardial perfusion images using either thallium-201 or technetium-99m sestamibi, and no previous coronary revascularization. Follow-up was 95% complete. Cardiovascular survival was 99.8% at 1 year, 99.0% at 5 years, and 98.5% at 7 years. Cardiac survival free of myocardial infarction was similarly high at 96.6% at 7 years. Cardiac survival free of myocardial infarction or revascularization was 87.1% at 7 years. Near-normal scans and cardiac enlargement were independent predictors of time to cardiac death. Seven-year cardiac survival was still high at 97.0% in the 357 patients with near-normal scans and normal cardiac size and somewhat lower, at 89.0%, in the 167 patients with cardiac enlargement.

CONCLUSIONS

Patients with an intermediate-risk treadmill score but with normal or near-normal exercise myocardial perfusion images and normal cardiac sizes are at low risk for subsequent cardiac death and can be safely managed medically until their symptoms warrant revascularization. The appropriate management of patients with cardiac enlargement will remain a matter of clinical judgment.

Comparison of dobutamine echocardiography, dobutamine sestamibi, and rest-redistribution thallium-201 single-photon emission computed tomography for determining contractile reserve and myocardial ischemia in ischemic cardiomyopathy

Both dobutamine stress echocardiography (DSE) and myocardial perfusion scintigraphy are used to assess myocardial viability. Few studies have compared the data on myocardial viability and ischemia by low and peak dose DSE and myocardial perfusion imaging in the same patients. Fifty-four patients (45 men and 9 women aged 65 +/- 9 years) with ischemic cardiomyopathy (mean ejection fraction 24 +/- 9%) underwent rest 4-hour redistribution thallium-201 single-photon emission computed tomography (SPECT), low and peak dose DSE, and dobutamine sestamibi SPECT. A total of 864 segments were analyzed (16 segments/patient). Wall motion abnormality was present in 796 segments (92%), and contractile reserve during dobutamine infusion was seen in 400 of these segments (50%). Contractile reserve was seen in 331 of 509 hypokinetic segments (65%) and 69 of 287 akinetic/dyskinetic segments (24%) (p <0.001). Contractile reserve was more frequent in segments with normal thallium uptake (64%), reversible thallium defects (42%), or mild to moderate fixed thallium defects (48%) than severely fixed defects (22%) (p <0.05 each). Concordant information about viability by thallium imaging and DSE was obtained in 62% of segments. Dobutamine sestamibi ischemia was seen in 518 of 796 segments (65%) compared with 265 segments (33%) by DSE (p <0.001). Scintigraphic ischemia was noted in 126 of 195 segments (65%) demonstrating biphasic response, 129 of 205 segments (63%) showing sustained improvement, 42 of 70 segments (60%) deteriorating during dobutamine infusion, and 221 of 326 (68%) demonstrating no change (p = NS). Thus, in patients with ischemic cardiomyopathy, contractile reserve is more frequent in hypokinetic segments than akinetic/dyskinetic segments. The number of segments with normal or near-normal thallium uptake or with scintigraphic ischemia is significantly greater than the number of those capable of increasing contractile function or demonstrating an ischemic response during dobutamine echocardiography.

Impact of stress single-photon emission computed tomography perfusion imaging on downstream resource utilization

This study shows that in patients with intermediate pretest probability of coronary artery disease stress single-photon emission computed tomography perfusion imaging decreases the rate of coronary angiography and coronary revascularization and is economically a superior strategy to routine coronary angiography.

Comparison of the prognostic value of qualitative versus quantitative stress tomographic perfusion imaging

This study compared qualitative assessment of exercise thallium imaging to quantitative assessment in predicting outcome in 713 patients with 78% prevalence of coronary artery disease by coronary angiography; during a mean follow-up of 52 months, there were 106 hard cardiac events (death or nonfatal myocardial infarction). The qualitative method provided important prognostic information; however, unlike the quantitative technique, less patients were assigned to either the low- or high-risk group and proportionally more patients into the intermediate-risk group, which may limit the clinical usefulness of the technique.

Regulation of 2-carboxy-D-arabinitol 1-phosphate phosphatase: activation by glutathione and interaction with thiol reagents

2-Carboxy-D-arabinitol 1-phosphate (CA1P) phosphatase de- grades CA1P, an inhibitor associated with the regulation of ribulose bisphosphate carboxylase/oxygenase in numerous plant species. CA1P phosphatase purified from Phaseolus vulgaris was partially inactivated by oxidizing conditions during dialysis in air-equilibrated buffer. Phosphatase activity could then be stimulated 1.3-fold by dithiothreitol and also by addition of reduced thioredoxin from Escherichia coli. These effects were enhanced synergistically by the positive effector, fructose 1, 6-bisphosphate (FBP). Most notably, CA1P phosphatase activity was stimulated up to 35-fold by glutathione, and was sensitive to the ratio of reduced (GSH) to oxidized (GSSG) forms. At concentrations of glutathione approximating measured levels in chloroplasts of P. vulgaris (5 mM total S), CA1P phosphatase exhibited >20-fold stimulation by a change in the redox status of glutathione from 60 to 100% GSH. This stimulation was augmented further by reduced E. coli thioredoxin. In contrast, FBP, which activates CA1P phosphatase under reducing conditions, was strongly inhibitory in the presence of GSSG. We propose that glutathione may have an appreciable role in the light/dark regulation of CA1P phosphatase in vivo. A model for the reversible activation of CA1P phosphatase by GSH was derived based upon the various responses of the enzyme's activity to a range of thiol reagents including N-ethylmaleimide, 5, 5'-dithiobis-(2-nitrobenzoic acid) and arsenite. These data indicate that the bean enzyme contains two physically distinct sets of thiol groups that are critical to its redox regulation.

Predictors of outcome of medically treated patients with left main/three-vessel coronary artery disease by coronary angiography

This study examined the prognostic value of single-photon emission computed tomography in angiographically high-risk patients with left main and/or 3-vessel coronary artery disease who were treated medically. Multivariable Cox survival analysis revealed the single-photon emission computed tomography score (based on size of perfusion abnormality, multivessel abnormality, left ventricular dilation, and lung uptake) as the only independent predictor of outcome.

Comparison of the polar maps method and the summed stress score for predicting outcome in medically treated patients with coronary artery disease

This study showed that quantitative analysis of SPECT perfusion images provide comparable prognostic information to summed stress score in medically treated patients with coronary artery disease.