Cortical Distribution of Fragile Periventricular Anastomotic Collateral Vessels in Moyamoya Disease: An Exploratory Cross-Sectional Study of Japanese Patients with Moyamoya Disease.

BACKGROUND AND PURPOSE: Collateral vessels in Moyamoya disease represent potential sources of bleeding. To test whether these cortical distributions vary among subtypes, we investigated cortical terminations using both standardized MR imaging and MRA. MATERIALS AND METHODS: Patients with Moyamoya disease who underwent MR imaging with MRA in our institution were enrolled in this study. MRA was spatially normalized to the Montreal Neurological Institute space; then, collateral vessels were measured on MRA and classified into 3 types of anastomosis according to the parent artery: lenticulostriate, thalamic, and choroidal. We also obtained the coordinates of collateral vessel outflow to the cortex. Differences in cortical terminations were compared among the 3 types of anastomosis. RESULTS: We investigated 219 patients with Moyamoya disease, and a total of 190 collateral vessels (lenticulostriate anastomosis, n = 72; thalamic anastomosis, n = 21; choroidal anastomosis, n = 97) in 46 patients met the inclusion criteria. We classified the distribution patterns of collateral anastomosis as follows: lenticulostriate collaterals outflowing anteriorly (P < .001; 95% CI, 67.0-87.0) and medially (P < .001; 95% CI, 11.0-24.0) more frequently than choroidal collaterals; lenticulostriate collaterals outflowing anteriorly more frequently than thalamic collaterals (P < .001; 95% CI, 34.0-68.0); and choroidal collaterals outflowing posteriorly more frequently than thalamic collaterals (P < .001; 95% CI, 14.0-34.0). Lenticulostriate anastomoses outflowed to the superior or inferior frontal sulcus and interhemispheric fissure. Thalamic anastomoses outflowed to the insular cortex and cortex around the central sulcus. Choroidal anastomoses outflowed to the cortex posterior to the central sulcus and the insular cortex. CONCLUSIONS: Cortical distribution patterns appear to differ markedly among the 3 types of collaterals.

Tat pathway-mediated translocation of the Sec pathway substrate OprM, an outer membrane subunit of the resistance nodulation division xenobiotic extrusion pumps, in Pseudomonas Aeruginosa.

BACKGROUND: Pseudomonas aeruginosa produces the Sec and Tat protein secretion machineries. The latter appears to be involved in the secretion of virulence factors, including phospholipase C (PlcH), and hence is a potential target of chemotherapeutic agents. METHODS: The signal sequence of OprM, the outer membrane subunit of the xenobiotic extrusion pumps, was substituted with that of PlcH. The antibiotic susceptibility of oprM-deficient cells expressing the hybrid protein PlcH-OprM was evaluated using the agar dilution method. RESULTS: The PlcH-OprM-expressing cells showed resistance to various MexAB-OprM substrate antibiotics. To evaluate the translocation route of PlcH-OprM, tatC encoding an indispensable component of the Tat machinery was knocked out in oprM-deficient cells. The tatC-oprM double mutant expressing PlcH-OprM exhibited antibiotic hypersusceptibility like the oprM-deficient cells, indicating that PlcH-OprM was translocated across the inner membrane exclusively through the Tat system. CONCLUSIONS: This system can be used for the screening of Tat system inhibitors and will be an excellent model for the study of secretion and biogenesis of the ß-barrel outer membrane proteins.

Prevention of excessive collagen accumulation by human intravenous immunoglobulin treatment in a murine model of bleomycin-induced scleroderma.

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrotic changes in skin and other organs involving excessive collagen deposition. Here we investigated the effect of intravenous immunoglobulin (IVIG) on fibrosis in a murine model of bleomycin (BLM)-induced scleroderma. Scleroderma was induced in C3H/He J mice by subcutaneous BLM injections daily for 35 days. The collagen content in skin samples from the BLM-injected group (6·30 ± 0·11 mg/g tissue) was significantly higher than the PBS group (5·80 ± 0·10 mg/g tissue), and corresponded with dermal thickening at the injection site. In contrast, mice treated with IVIG for 5 consecutive days after initiating BLM injection showed lesser collagen content significantly (IVIG group, 5·61 ± 0·09 mg/g tissue; BLM vs. IVIG). In order to investigate the cellular and protein characteristics in the early stage of the model, the skin samples were obtained 7 days after the onset of experiment. Macrophage infiltration to the dermis, monocyte chemoattractant protein (MCP-1)-positive cells, and increased TGF-ß1 mRNA expression were also observed in the BLM group. IVIG inhibited these early fibrogenic changes; MCP-1 expression was significantly lesser for the IVIG group (1·52 ± 0·19 pg/mg tissue) than for the BLM group (2·49 ± 0·26 pg/mg tissue). In contrast, TGF-ß1 mRNA expression was significantly inhibited by IVIG. These results suggest that IVIG treatment may inhibit macrophage recruitment to fibrotic sites by down regulating MCP-1 and TGF-ß production, and thus could be a potential drug for managing fibrotic disorders such as SSc.

Fluids containing a highly branched cyclic dextrin influence the gastric emptying rate.

The rates of gastric emptying for highly branched cyclic dextrin (HBCD) and other carbohydrate (CHO) solutions were examined using ultrasonograph techniques. Ten healthy volunteers ingested water, physiological saline, or solutions containing various CHO, such as HBCD, glucose, maltose, sucrose, and commercially available dextrin. After a subject drank one of the solutions, the relaxed cross-sectional area of the pylorus antrum was measured at rest by real-time ultrasonography. The time required for gastric emptying was correlated with the relaxed cross-sectional area of the pylorus antrum. Among all of the solutions tested, physiological saline was transferred fastest from the stomach to the small intestine. For solutions of the same CHO, 5 % solution was transferred faster than 10 % solution. For CHO solutions other than HBCD, a low osmotic pressure was associated with rapid transfer from the stomach. The gastric emptying time (GET) of HBCD solution increased with an increase in its concentration. A shorter GET was observed for the CHO solutions at 59 to 160 mOsm regardless of their concentration. A sports drink based on 10 % HBCD adjusted to 150 mOsm by the addition of various minerals, vitamins, and organic acids was evacuated significantly (p < 0.05) faster than a 10 % HBCD solution or a sports drink based on 10 % commercially available dextrin (DE16), which has a higher osmotic pressure (269 mOsm). Our results suggest that a shorter GET could be achieved with CHO solutions with osmotic pressures of 59 - 160 mOsm. Therefore, a sports drink based on 10 % HBCD adjusted to 150 mOsm by the addition of minerals, vitamins, and organic acids could supply adequate quantities of CHO, fluid, and minerals simultaneously in a short time, without increasing GET.

[A case of Mycobacterium intracellulare infection complicated by immotile cilia syndrome].

A 25-year-old woman with a history of immotile cilia syndrome (ICS) was admitted to our hospital with dyspnea. Chest roentgenography revealed dense infiltrates in both lower lung fields in addition to bronchiectasis and small nodular opacities, which had been observed previously. Transbronchial lung biopsy demonstrated evidence of non-caseating epithelioid cell granuloma. Sputum specimens were examined, and isolates were identified as Mycobacterium intracellulare. The patient was given antituberculous therapy and clarithromycin, which induced clinical improvement. It is well known that bronchial mucociliary transport is severely impaired in patients with ICS. However, to our knowledge, cases of M. intracellulare infection complicated by ICS have not been reported in Japan. We must pay close attention to the concurrence of these diseases.

Comparison of T-wave alternans and QT interval dispersion to predict ventricular tachyarrhythmia in patients with dilated cardiomyopathy and without antiarrhythmic drugs: a prospective study.

Microvolt T-wave alternans (TWA) and QT interval dispersion (QTD), which reflect temporal and spatial repolarization abnormalities, respectively, have been proposed as useful indices to identify patients at risk for ventricular tachyarrhythmias (VTs). The purpose of this study was to clarify which repolarization abnormality marker is more useful in predicting arrhythmic events in patients with dilated cardiomyopathy (DCM). Forty-two consecutive nonischemic DCM patients underwent the assessment of TWA and QTD. Patients undergoing antiarrhythmic pharmacotherapy, except beta-blockers and those with irregular basic rhythms, were excluded from entry. Eight patients were also excluded because of indeterminate test results. Therefore, 34 DCM patients were prospectively assessed. The end point of the study was the documentation of VT defined as > or = 5 consecutive ectopic beats during the follow-up period. TWA and QTD (> or = 65 msec) were positive in 24 (80%) and 11 (37%) of 30 patients with available follow-up data, respectively. There was no relationship between TWA and QTD. During a follow-up of 13+/-11 months, VTs occurred in 13 patients (43%). In Cox regression analysis, TWA was a significant risk stratifier (p=0.02), whereas QTD was not. The sensitivity, specificity, and positive and negative predictive values of TWA in predicting VTs were 100%, 35%, 54%, and 100%, respectively. TWA could be a useful noninvasive index to identify patients at risk for VTs in the setting of DCM. This study may suggest that temporal repolarization abnormality is associated more with arrhythmogenesis than with spatial repolarization abnormality in DCM patients.

Evidence for coupling of membrane targeting and function of the signal recognition particle (SRP) receptor FtsY.

Recent studies have indicated that FtsY, the signal recognition particle receptor of Escherichia coli, plays a central role in membrane protein biogenesis. For proper function, FtsY must be targeted to the membrane, but its membrane-targeting pathway is unknown. We investigated the relationship between targeting and function of FtsY in vivo, by separating its catalytic domain (NG) from its putative targeting domain (A) by three means: expression of split ftsY, insertion of various spacers between A and NG, and separation of A and NG by in vivo proteolysis. Proteolytic separation of A and NG does not abolish function, whereas separation by long linkers or expression of split ftsY is detrimental. We propose that proteolytic cleavage of FtsY occurs after completion of co-translational targeting and assembly of NG. In contrast, separation by other means may interrupt proper synchronization of co-translational targeting and membrane assembly of NG. The co-translational interaction of FtsY with the membrane was confirmed by in vitro experiments.

Lack of noninvasive markers of ventricular repolarization inhomogeneity in patients with idiopathic ventricular tachyarrhythmia.

Noninvasive markers reflecting repolarization inhomogeneity have been proposed to be useful indices for identifying patients at risk of ventricular arrhythmias based on organic heart disease. In this study, we clarify whether or not repolarization inhomogeneity markers are useful in patients with idiopathic ventricular tachycardia (VT). We investigated T-wave alternans (TWA) and corrected QT-interval dispersion (QTD) in 84 consecutive patients with idiopathic VT, 90 patients with VT associated with organic heart disease (organic VT), and 87 normal individuals. VT was defined as tachycardia lasting > or =5 consecutive ventricular ectopic beats at a rate of > or =120 beats/min. TWA was positive in 20 of 84 patients (24%) with idiopathic VT, 59 of 90 patients (66%) with organic VT, and 16 of 87 normal individuals (18%). The alternans voltage was 2.6 +/- 3.1 micro V in idiopathic VT patients, 5.6 +/- 6.4 micro V in organic VT patients, and 2.9 +/- 5.7 micro V in normal individuals. QTD were 53 +/- 20 ms in idiopathic VT patients, 92 +/- 20 ms in organic VT patients, 46 +/- 18 ms in normal individuals, respectively. A positive TWA test result was seen more (P <.01) frequently, and QTD was longer (P <.01) in organic VT patients compared to normal individuals, whereas there was no difference between idiopathic VT patients and normal individuals. In addition, in patients with idiopathic VT, neither did any of these measurements differ between patients with sustained VT (lasting for > or =30 s) and those with nonsustained VT. Noninvasive markers of repolarization inhomogeneity, such as TWA and QTD, are not useful for identifying patients with idiopathic VT. Repolarization inhomogeneity may not affect to the pathogenesis of idiopathic VT.

Clinical usefulness of the combination of T-wave alternans and late potentials for identifying high-risk patients with moderately or severely impaired left ventricular function.

Ventricular tachyarrhythmia (VT) is an independent risk factor for an increased overall mortality in patients with impaired left ventricular (LV) function, but there is not an established noninvasive tool to detect such patients. The present study aimed to clarify the most useful noninvasive approach for identification of patients with moderately or severely impaired LV function complicated by VT. Sixty-seven patients in New York Heart Association (NYHA) classes I-III with an LV ejection fraction (LVEF) less than 40% and an LV end-diastolic dimension (LVDD) of at least 55 mm on echocardiography were enrolled. Impaired LV function was caused by either ischemic (n=30) or nonischemic dilated cardiomyopathy (n=37). T-wave alternans (TWA), QT dispersion (QTD), and late potentials (LP) on signal-averaged electrocardiography were sequentially determined without using antiarrhythmic drugs. VT was defined as more than 6 consecutive ventricular ectopic beats. The mean NYHA class was 1.9+/-0.7, mean LVEF was 31+/-8%, and mean LVDD was 65+/-10mm. A history of VT was present in 26 of the patients (39%). Univariate and multivariate logistic analysis showed that TWA and LP were closely related to VT, whereas NYHA> or =III, LVEF<30%, LVDD> or =70mm, and QTD> or =90ms were not. The combination of TWA and LP had the most significant value (p=0.0004, odds ratio=8.44) by univariate analysis, and only this combination had significant value in multivariate analysis (p=0.04). Therefore, the combination of TWA and LP could be a useful index for identifying those patients with impaired LV function who are at risk for VT.

Predicting the recurrence of ventricular tachyarrhythmias from T-wave alternans assessed on antiarrhythmic pharmacotherapy: a prospective study in patients with dilated cardiomyopathy.

BACKGROUND: Microvolt T-wave alternans (TWA) has been proposed as a useful index to identify patients at risk of ventricular tachyarrhythmias. Recent studies have demonstrated that antiarrhythmic drugs, such as amiodarone and procainamide, decrease the prevalence of TWA. In this study, we tested whether TWA in patients on antiarrhythmic pharmacotherapy significantly predicts the recurrence of ventricular tachyarrhythmias in patients with dilated cardiomyopathy. METHODS: To evaluate the ability to predict the recurrence of ventricular tachyarrhythmias, determinate TWA and left ventricular ejection fraction (LVEF) were prospectively assessed in 49 patients with ischemic or nonischemic dilated cardiomyopathy on antiarrhythmic pharmacotherapy for sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). The pharmacotherapy consisted of class I (17 patients), III (29 patients), and IV (3 patients) antiarrhythmic drugs. The study endpoint was the first recurrence of sustained VT or VF on treatment during the follow-up period. RESULTS: TWA was positive on antiarrhythmic pharmacotherapy in 30 patients (61%). During a follow-up of 13 +/- 11 months, the sustained VT or VF recurred in 21 of the 41 patients (51%) with available follow-up data. The sensitivity of TWA and LVEF for predicting recurrence of ventricular tachyarrhythmias was 76 and 38%, specificity was 60 and 70%, positive predictive value was 67 and 57%, and negative predictive value was 71 and 52%. Kaplan-Meier event-free analysis revealed that TWA was a significant risk stratifier (P = 0.02), whereas LVEF was not. CONCLUSIONS: This prospective study suggests that TWA significantly predicts the recurrence of ventricular tachyarrhythmias, even on antiarrhythmic pharmacotherapy, in patients with dilated cardiomyopathy. TWA may also be a useful marker for evaluating the efficacy of antiarrhythmic drugs for ventricular tachyarrhythmias.

Intravenous immunoglobulin prevents experimental autoimmune myositis in SJL mice by reducing anti-myosin antibody and by blocking complement deposition.

High-dose intravenous immunoglobulin (IVIG) therapy has been effective in many autoimmune and systemic inflammatory diseases including polymyositis (PM) and dermatomyositis (DM). In the present study we evaluated the efficacy of IVIG using experimental models of PM and DM. An experimental autoimmune myositis (EAM) model was produced in SJL/J mice by an immunization with rabbit myosin B (MB) fraction. In this model, the plasma level of anti-MB antibody was elevated, and mouse IgG and complement C3 were deposited in the muscle fibres. Administration of IVIG dose-dependently reduced the incidences of necrotic and inflammatory changes in the skeletal muscle. IVIG treatment also decreased the elevation of anti-MB antibody level, as well as the deposition of IgG and C3. We next evaluated the effect of IVIG in adoptive EAM mice made by an intravenous injection of lymph node cells previously stimulated with MB. Adoptive EAM mice showed similar lesions in skeletal muscle as EAM mice and IVIG inhibited the lesion development. In vitro experiments demonstrated that IVIG inhibited complement-mediated lysis of human erythrocytes sensitized with anti-human erythrocyte antibodies. The binding of C1q, C4 and C3 to the same cells was also inhibited by IVIG. Taken together these findings suggest that IVIG prevents the development of myositis in EAM and adoptive EAM models by several mechanisms, such as reducing anti-myosin antibody and by blocking complement activation. Our present findings might account for the clinical efficacy of IVIG in PM and DM patients.

Assessment of noninvasive markers in identifying patients at risk in the Brugada syndrome: insight into risk stratification.

OBJECTIVES: The aim of this study was to compare the use of various noninvasive markers for detecting risk of life-threatening arrhythmic events in patients with Brugada syndrome. BACKGROUND: The role of conduction disturbance in arrhythmogenesis of the syndrome is controversial, whereas it is well established that repolarization abnormalities are responsible for arrhythmias. The value of noninvasive markers reflecting conduction or repolarization abnormalities in identifying patients at risk for significant arrhythmias has not been shown. METHODS: We assessed late potentials (LP) using signal-averaged electrocardiography (ECG), microvolt T-wave alternans (TWA), and corrected QT-interval dispersion (QTD) in 44 consecutive patients who had ECGs showing a pattern of right bundle branch block and ST-segment elevation in leads V1 to V3 but structurally normal hearts. The patients were compared with 30 normal individuals. RESULTS: Eleven patients were excluded from data analysis because of an absence of ECG manifestations of Brugada syndrome at the time of the tests. A history of life-threatening events defined as syncope and aborted sudden death was present in 19 of 33 patients (58%); in 15 of the 19 patients, stimulation induced ventricular fibrillation or polymorphic ventricular tachycardia. The LP were present in 24 of 33 patients (73%); TWA were present in 5 of 31 patients (16%); and a QTD >50 ms was present in 9 of 33 patients (27%). The incidence of LP in Brugada patients was significantly (p < 0.0001) higher than in the controls, whereas incidences of TWA and QTD were not significantly different. Multivariate logistic regression analysis revealed that the presence of LP had the most significant correlation to the occurrence of life-threatening events (p = 0.006). CONCLUSIONS: Late potentials are a noninvasive risk stratifier in patients with Brugada syndrome. These results may support the idea that conduction disturbance per se is arrhythmogenic.

Antidiabetic effect of glycyrrhizin in genetically diabetic KK-Ay mice.

We, previously demonstrated that one shot administration of glycyrrhizin (Grz) reduced the postprandial blood glucose rise, using Std ddY mice. Subsequently, we evaluated the effects of long-term Grz treatment (2.7, 4.1 g/kg diet) on diabetic symptoms using genetically non-insulin dependent diabetic model mice (KK-Ay). Male KK-Ay mice were divided into 3 groups: the control group, 0.27% Grz diet (2.7 g of Grz/kg diet) group and 0.41% Grz diet (4.1 g of Grz/kg diet) group. The elevation of blood glucose concentration was almost entirely suppressed in mice fed the 0.41% Grz diet 7 weeks after the beginning of test feeding, although it was not suppressed in mice fed the control diet or the 0.27% Grz diet. Water intake in the control and 0.27% Grz diet groups increased gradually, whereas, this was not true in the 0.41% Grz diet group. Grz treatment significantly lowered blood insulin level. Throughout the experiment, Grz did not affect the food intake or body weight among the three groups. The mice fed the 0.41% Grz diet also improved their tolerance to oral glucose loading 9 weeks after the beginning of test feeding. This study shows that Grz has an antidiabetic effect in noninsulin-dependent diabetes model mice.

Molecular mechanism of MexR-mediated regulation of MexAB-OprM efflux pump expression in Pseudomonas aeruginosa.

To elucidate the molecular mechanism by which the MexR repressor regulates expression of the MexAB-OprM efflux pump, we investigated MexR and the mexR-mexA intergenic DNA (mexOP) interaction, and transcription of the mexA-lacZ reporter gene containing different lengths of mexOP. Homogeneously purified MexR bound specifically to mexOP proximal to mexR. The mexOP-lacZ fusion gene lacking the region immediately proximal to mexR showed minimum enzyme activity, thereby suggesting that a promoter element is located between mexR and the MexR-binding sites. These observations explain the mechanism of self-regulation of mexR expression as well as low and elevated expression of MexAB-OprM in the wild-type strain and nalB-type mutant, respectively, of Pseudomonas aeruginosa.

Identification of essential charged residues in transmembrane segments of the multidrug transporter MexB of Pseudomonas aeruginosa.

The MexABM efflux pump exports structurally diverse xenobiotics, utilizing the proton electrochemical gradient to confer drug resistance on Pseudomonas aeruginosa. The MexB subunit traverses the inner membrane 12 times and has two, two, and one charged residues in putative transmembrane segments 2 (TMS-2), TMS-4, and TMS-10, respectively. All five residues were mutated, and MexB function was evaluated by determining the MICs of antibiotics and fluorescent dye efflux. Replacement of Lys342 with Ala, Arg, or Glu and Glu346 with Ala, Gln, or Asp in TMS-2 did not have a discernible effect. Ala, Asn, or Lys substitution for Asp407 in TMS-4, which is well conserved, led to loss of activity. Moreover, a mutant with Glu in place of Asp407 exhibited only marginal function, suggesting that the length of the side chain at this position is important. The only replacements for Asp408 in TMS-4 or Lys939 in TMS-10 that exhibited significant function were Glu and Arg, respectively, suggesting that the native charge at these positions is required. In addition, double neutral mutants or mutants in which the charged residues Asp407 and Lys939 or Asp408 and Lys939 were interchanged completely lost function. An Asp408-->Glu/Lys939-->Arg mutant retained significant activity, while an Asp407-->Glu/Lys939-->Arg mutant exhibited only marginal function. An Asp407-->Glu/Asp408-->Glu double mutant also lost activity, but significant function was restored by replacing Lys939 with Arg (Asp407-->Glu/Asp408-->Glu/Lys939-->Arg). Taken as a whole, the findings indicate that Asp407, Asp408, and Lys939 are functionally important and raise the possibility that Asp407, Asp408, and Lys939 may form a charge network between TMS-4 and TMS-10 that is important for proton translocation and/or energy coupling.

Atrial double potentials associated with the elimination of the electrical connection between the coronary sinus (CS) and the left atrium in two cases of Wolff-Parkinson-White syndrome with a CS-connected accessory pathway.

A curious retrograde conduction in connection with the coronary sinus (CS) musculature was observed in 2 patients. After the failed ablation procedure, the atrial electrogram during ventricular pacing presented double potentials, the first component of which was sharp and with an activation sequence that was the same before ablation (CS distal to proximal). The second component of the double potentials was dull and had a decremental property; its activation sequence was in reverse (proximal to distal). In both cases, the first component disappeared after successful ablation. These findings suggest that the first component was the CS electrogram conducted over the accessory pathway and the second component was the left atrial electrogram conducted through the inter-atrial septum. The separation of each electrogram is probably the result of a block between the accessory pathway connected to the CS musculature and the left atrium. These are unusual cases of an accessory pathway connected to the CS musculature, which separates the left atrial myocardium at the distal portion from the ostium.

Variation of the mexT gene, a regulator of the MexEF-oprN efflux pump expression in wild-type strains of Pseudomonas aeruginosa.

We found three variations of wild-type strains in terms of mexT-mediated regulation of the MexEF-OprN efflux pump, in which overexpression of the pump results in nfxC-type antibiotic resistance in Pseudomonas aeruginosa. Type-I: the mexT gene of the wild-type strain encoded inactive MexT and the nfxC-type mutants derived from this parent had an additional mutation in mexT converting MexT from the inactive to the active form. Type-II: The mexT gene in the wild-type strain had an 8-bp insert producing inactive MexT and the nfxC-type mutants from this parent had a deletion of the 8-bp insert converting inactive MexT to the active form. Type-III: Both the wild-type strain and its nfxC-type derivative produced identical and active MexT. The nfxC mutant from this parent must have an additional mutation. The original nfxC mutant isolated in 1990 might be derived from the Type-I parent strain.

Lack of an association between T-wave alternans and ST-segment depression during exercise-induced ambulatory ischemia.

It is known that T-wave alternans (TWA), which identify patients at risk for arrhythmic events, often occur during acute coronary occlusion in association with ST-segment elevation. To test the hypothesis that TWA is associated with a certain state/severity of myocardial infarction/ischemia, we assessed the association between TWA and ST-segment depression during exercise-induced ambulatory ischemia. Of 351 consecutive patients with coronary artery disease who underwent assessment of microvolt TWA by exercise, 23 patients with effort angina without a history of infarction with ST depression (> or =0.11 mV) during TWA test were selected. These patients were compared with 222 postinfarction patients consisting of 38 patients with, and 184 patients, without the ST depression, and 18 normal individuals. The incidence (9%) of determinate TWA in the patients with angina was significantly (P < .0001) lower than that (52%) in the postinfarction patients. There was no significant difference between the angina patients and the controls (6%). There was also no difference between the patients with (58%) and without the ST depression (51%) in the postinfarction patients. Moreover, no correlation existed between the TWA voltage and the ST-depression magnitude in both angina and postinfarction patients. We concluded that there is no association between TWA and ambulatory ischemia with ST depression.

Localization of the outer membrane subunit OprM of resistance-nodulation-cell division family multicomponent efflux pump in Pseudomonas aeruginosa.

The outer membrane subunit OprM of the multicomponent efflux pump of Pseudomonas aeruginosa has been assumed to form a transmembrane xenobiotic exit channel across the outer membrane. We challenged this hypothesis to clarify the underlying ambiguity by manipulating the amino-terminal signal sequence of the OprM protein of the MexAB-OprM efflux pump in P. aeruginosa. [(3)H]Palmitate uptake experiments revealed that OprM is a lipoprotein. The following lines of evidence unequivocally established that the OprM protein functioned at the periplasmic space. (i) The OprM protein, in which a signal sequence including Cys-18 was replaced with that of periplasmic azurin, appeared in the periplasmic space but not in the outer membrane fraction, and the protein fully functioned as the pump subunit. (ii) The hybrid OprM containing the N-terminal transmembrane segment of the inner membrane protein, MexF, appeared exclusively in the inner membrane fraction. The hybrid protein containing 186 or 331 amino acid residues of MexF was fully active for the antibiotic extrusion, but a 42-residue protein was totally inactive. (iii) The mutant OprM, in which the N-terminal cysteine residue was replaced with another amino acid, appeared unmodified with fatty acid and was fractionated in both the periplasmic space and the inner membrane fraction but not in the outer membrane fraction. The Cys-18-modified OprM functioned for the antibiotic extrusion indistinguishably from that in the wild-type strain. We concluded, based on these results, that the OprM protein was anchored in the outer membrane via fatty acid(s) attached to the N-terminal cysteine residue and that the entire polypeptide moiety was exposed to the periplasmic space.

Combined assessment of T-wave alternans and late potentials used to predict arrhythmic events after myocardial infarction. A prospective study.

OBJECTIVES: The aim of the present study was to determine whether the combination of two markers that reflect depolarization and repolarization abnormalities can predict future arrhythmic events after acute myocardial infarction (MI). BACKGROUND: Although various noninvasive markers have been used to predict arrhythmic events after MI, the positive predictive value of the markers remains low. METHODS: We prospectively assessed T-wave alternans (TWA) and late potentials (LP) by signal-averaged electrocardiogram (ECG) and ejection fraction (EF) in 102 patients with successful determination results after acute MI. The TWA was analyzed using the power-spectral method during supine bicycle exercise testing. No antiarrhythmic drugs were used during the follow-up period. The study end point was the documentation of ventricular arrhythmias. RESULTS: The TWA was present in 50 patients (49%), LP present in 21 patients (21%), and an EF <40% in 28 patients (27%). During a follow-up period of 13 +/- 6 months, symptomatic, sustained ventricular tachycardia or ventricular fibrillation occurred in 15 patients (15%). The event rates were significantly higher in patients with TWA, LP, or an abnormal EF. The sensitivity and the negative predictive value of TWA in predicting arrhythmic events were very high (93% and 98%, respectively), whereas its positive predictive value (28%) was lower than those for LP and EF. The highest positive predictive value (50%) was obtained when TWA and LP were combined. CONCLUSIONS: The combined assessment of TWA and LP was associated with a high positive predictive value for an arrhythmic event after acute MI. Therefore, it could be a useful index to identify patients at high risk of arrhythmic events.