Rapid mRNA degradation mediated by the c-fos 3' AU-rich element and that mediated by the granulocyte-macrophage colony-stimulating factor 3' AU-rich element occur through similar polysome-associated mechanisms.

The different 3' noncoding AU-rich elements (ARE) that mediate the degradation of many short-lived mRNAs may function through distinct decay pathways; translation-dependent and -independent mechanisms have been proposed. To investigate the cotranslational model, we designed an expression system that exploits the properties of the ferritin iron-responsive element to shuttle chimeric mRNAs from ribonucleoproteins to polyribosomes. The iron-responsive element was introduced in the 5' untranslated regions of alpha-globin mRNAs that harbored in their 3' untranslated regions either the c-fos ARE or the granulocyte-macrophage colony-stimulating factor ARE as prototypes of the different ARE subsets. The cytoplasmic location of the transcripts was controlled by intracellular iron availability and monitored by polysomal profile analysis. We report that these two mRNA subsets behaved identically in this system. Iron deprivation by desferrioxamine treatment stabilized both transcripts by sequestering them away from polyribosomes. Sequential treatments with desferrioxamine, followed by hemin to concentrate the mRNAs in the ribonucleoprotein pool prior to translation, showed that rapid degradation occurred only upon redistribution of the transcripts to polyribosomes. Deletion of a critical cytosine in the iron-responsive element abolished targeted sequestration and restored high-level constitutive mRNA instability. These observations demonstrate that the c-fos and granulocyte-macrophage colony-stimulating factor ARE subsets mediate selective mRNA degradation through similar polysome-associated mechanisms coupled with ongoing translation.

Atrial tachyarrhythmias after the maze procedure: incidence and prognosis.

BACKGROUND: The Maze procedure restores normal sinus rhythm in the majority of patients. However, atrial tachyarrhythmias (ATA) are a common early complication after the operation. The purpose of this study was to define the incidence and natural history of ATA after the Maze procedure. METHODS: Complete medical records from 200 patients who underwent the Maze procedures (I, II, and III) from 1987 to 2002 were examined for all episodes of early postoperative ATA that occurred during the first 30 days after the procedure. Two electrophysiologists independently reviewed all postoperative 12-lead electrocardiograms. RESULTS: ATA occurred in 86 patients (43%) after the Maze procedure. Of the patients with ATA, 59% had atrial fibrillation (AF), 14% had atrial flutter (AFL), and 27% had both AF and AFL. Of the patients with AF or AFL, 20% and 5%, respectively, also had episodes of atrial tachycardia and supraventricular tachyarrhythmia. The peak incidence of early postoperative ATA was on postoperative day 8. The average duration of ATA was 5.7+/-5.0 days. Late recurrence of AF (>1 year postoperatively) occurred in 7.0% of patients who had early postoperative ATA and 8.8% of patients without early postoperative ATA (P=0.8). CONCLUSIONS: ATA occurred in 43% of patients after the Maze procedure. The tachyarrhythmias occurred primarily within 8 days after surgery and resolved within 3 weeks in almost all patients. There was no relationship between the incidence of early postoperative ATA and the late recurrence of AF.

Therapeutic end points for the treatment of atrioventricular node reentrant tachycardia by catheter-guided radiofrequency current.

OBJECTIVES: The purpose of this prospective study was to test the hypothesis that the elimination of inducible repetitive atrioventricular (AV) node reentry despite the persistence of slow AV pathway conduction is a valid end point for radiofrequency catheter ablation procedures in patients with supraventricular tachycardia due to AV node reentry. BACKGROUND: Although modification of AV node physiology by radiofrequency current can eliminate AV node reentrant tachycardia, therapeutic end points that are definitive of a satisfactory result in patients undergoing modification of the slow AV pathway have not been established. Applications of radiofrequency current at selected sites may eliminate all evidence of slow pathway conduction or sufficiently modify the refractory properties of the slow pathway to preclude sustained arrhythmias. Accordingly, total abolition of dual AV node physiology may not be necessary to prevent arrhythmia recurrence. METHODS: Radiofrequency catheter ablation of the slow AV pathway was attempted in 59 patients with typical AV node reentry. Tissue ablation was performed with a continuous wave of 500-kHz radiofrequency current. Twenty-five to 35 W was applied for 60 s at the site selected for tissue destruction. RESULTS: Dual AV node physiology was eliminated completely in 35 patients (59%), persisted without inducible AV node reentry in 13 patients (22%) and persisted with inducible single AV reentrant beats in 11 patients (19%). In patients with persistent dual AV node physiology, the maximal difference between the effective refractory period of the fast and slow pathways was reduced from 104 +/- 62 ms before the procedure to 37 +/- 37 ms after AV conduction had been modified (p < 0.001). During a mean follow-up interval of 15 months (range 4 to 28), only one patient (2%) had a recurrence of the tachycardia. CONCLUSIONS: Results demonstrate that when complete elimination of dual AV node physiology is difficult, modification of slow pathway conduction to the extent that repetitive AV node reentry cannot be induced is a definitive end point that portends a good prognosis.

Contribution of the biliary pathway to the homeostasis of vitamin D3 and of 1,25-dihydroxyvitamin D3.

The role of the biliary pathway in the homeostasis of the vitamin D3 (D3) group of compounds is poorly understood. The purpose of the studies was to investigate the biliary excretion pattern of materials derived from the parent compound D3 and from the hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) during constant iv infusion, and to probe the influence of 1,25(OH)2D3 pretreatment on the excretion into the bile of D3-derived materials. Under anesthesia, the bile duct, duodenum (for bile replacement), and jugular veins were cannulated. The experiments were then carried out in fully awake rats with access to food and water ad libitum during a period of 6 h. Data indicate that before steady state was reached, biliary excretion of 1,25(OH)2[3H]D3 was much more important than that of [14C]D3 with bile/plasma concentration ratios above 1 in 1,25(OH)2[3H]D3-infused animals from the 15th-60th min of infusion compared to ratios between 0.12-0.40 in [14C]D3-infused rats (P less than 0.0001); this led to a cumulative excretion 6.3-fold higher after 1,25(OH)2[3H]D3 than after [14C]D3 administration, with 3.9 +/- 0.4% and 0.6 +/- 0.1% of the dose being recovered into the bile during the first hour of excretion. However, once stable plasma concentrations were reached, the rate of excretion of the two compounds became similar, with bile/plasma concentration ratios of 0.64 +/- 0.02 and 0.70 +/- 0.02 (P greater than 0.05), and plasma bile clearance of 26.4 +/- 1.0 and 25.7 +/- 1.7 microliters/min.kg for 1,25(OH)2[3H]D3 and [14C]D3, respectively (P greater than 0.05). During that period, the MCR of 1,25(OH)2D3 was estimated to be 118.3 +/- 10.5 microliters/min.kg. On the other hand, 1,25(OH)2D3 pretreatment as constant ip infusion (14 pmol/24 h for 6 days) significantly increased bile flow [1,25(OH)2D3 treated, 44.9 +/- 1.6 microliters/min.kg; untreated, 36.6 +/- 0.5 microliters/min.kg, P less than 0.01)], leading to significant increases in the plasma bile clearance of [14C]D3-derived compounds early in the course of the study (P less than 0.004) in the presence of similar bile/plasma concentration ratios in the two groups. During the steady state phase of investigation, however, bile/plasma concentration ratios became lower in 1,25(OH)2D3-than in placebo-treated animals (P less than 0.05), but due to the 1,25(OH)2D3-mediated increase in bile flow, similar plasma bile clearances were observed in both groups.(ABSTRACT TRUNCATED AT 400 WORDS)

P-selectin is upregulated early in the course of hyperoxic lung injury in mice.

While treatment with supplemental oxygen is often essential in patients with lung disease, prolonged therapy may cause lung injury by itself. Although the mechanisms responsible for initiating hyperoxic lung damage almost certainly involve primary oxidative transformations, the possible contributions of inflammation to the tissue injury have been attracting increasing research activity. Increases in intercellular adhesion molecule-1 (ICAM-1) coincide with the inflammation, but in other models of inflammation transient adhesion mediated by members of the Selectin gene family was found to be essential before ICAM-1/beta 2 interactions could occur. We, therefore, wondered whether a similar sequence of initial transient adhesion followed by subsequent responses would be observed in hyperoxic lung inflammation. We, therefore, determined the effects of hyperoxia exposure on lung mRNA for P- and E-Selectin in mouse lungs. We found that there was no detectable mRNA for E-Selectin through 72 h of hyperoxia exposure by Northern blotting, but that mRNA for P-Selectin was detectable as early as 48 h after initiation of hyperoxia. To determine the location of P-Selectin upregulation we examined hyperoxia-exposed mouse lungs by in situ hybridization and found that the upregulation of P-Selectin at 48 h was localized to large muscularized vessels, at 72 h expression was detected in some medium size muscularized vessels, and at 96 h abundant expression was observed also on nonmuscularized small vessels. In conclusion, increases in mRNA for P-Selectin early in the course of hyperoxia exposure suggest that P-Selectin expression in hyperoxic lungs increases in parallel with upregulation of ICAM-1, leading to the accumulation of neutrophils in hyperoxic lungs, and that interventions targeting these two adhesion molecules may lead to a diminution in hyperoxic lung inflammation and lung injury.

Interleukin-1 expression during hyperoxic lung injury in the mouse.

An important component of the pathophysiologic response to hyperoxia (O2) is pulmonary inflammation, although the roles of specific inflammatory mediators during pulmonary O2 toxicity are not completely known. Interleukin-1 (IL-1) is an early inflammatory mediator and is sufficient to elicit many of the responses associated with acute injury. The IL-1 family comprises two bioactive proteins, IL-1alpha and IL-1beta, and their natural antagonist IL-1ra. Here we report studies of IL-1 regulation during hyperoxic lung injury in the adult mouse. When assayed by Northern blot, increases in IL-1beta mRNA were seen after 2 days of hyperoxia. In contrast, IL-1alpha mRNA was barely detectable before 4 days of hyperoxia. To further understand the cellular origin of IL-1beta expression in lungs, in situ hybridization and immunohistochemical analyses were performed. IL-1beta mRNA or protein was not detected in the lungs of unexposed animals. At 3 days, we observed the accumulation of IL-1beta transcripts in pulmonary interstitial macrophages and in a subset of neutrophils, and immunodetectable IL-1beta protein was co-localized in adjacent sections. At 4 days of exposure, IL-1beta transcripts were widespread in lung tissue, but many areas rich in IL-1beta mRNA were devoid of immunodetectable IL-1beta. However, it is not known whether increased synthesis of IL-1beta or the uncoupling of IL-1beta protein and mRNA accumulation has a role in pathophysiology of pulmonary O2 toxicity.

The effects of tracheal occlusion and release on type II pneumocytes in fetal lambs.

UNLABELLED: Fetal tracheal occlusion (TO) has been shown to lead to lung hyperplasia in various animal models, and this procedure has already been carried out in human fetuses with congenital diaphragmatic hernia (CDH). However, the authors previously showed that TO caused a decrease in type II pneumocytes. PURPOSE: The aim of this study is to examine the effects of TO and release on type II pneumocytes. METHOD: To was carried out with a Swan Ganz or Fogarty catheter in fetal sheep at 116 to 118 days of gestation. TO was maintained for 2 weeks followed by deflation of the balloon for 1 week before delivery, in group 1; in group 2, TO was maintained for 19 days and released 2 days before delivery. Group 3 consisted of previously reported animals who had TO maintained until birth. Unoperated twins served as controls. All specimens were analyzed using the surfactant protein C (SP-C) mRNA as a specific marker for type II pneumocytes. We used Northern Blot and in situ hybridization techniques to quantify total SP-C and the density of type II cells. Electron microscopy (EM) was also used to evaluate and quantitate type II cells. RESULTS: TO resulted in significant lung growth in all groups. In situ hybridization and Northern Blot analysis showed that there was a complete recovery of type II cells in group 1 versus controls. Quantitative EM analysis confirmed these findings. In group 2 the number of type II cells was decreased but there was an increase in SP-C content per type II cell versus group 3. CONCLUSION: Lung growth after TO appears to occur at the expense of type II cell differentiation. This effect is reversible with the release of TO before birth in this animal model.

Radiologic appearance of implantable cardiac defibrillators.

Since the original descriptions of the radiologic appearance of implantable cardiac defibrillators by Lurie et al. [1] and Goodman et al. [2] in 1985, rapid growth has occurred in the complexity and variety of models available. Originally, all devices were surgically placed in or on the pericardium. Now, some devices are inserted by intravascular catheters with part of the device buried in the chest wall, avoiding the need for thoracotomy. Initially, these devices were used as defibrillators for treatment of tachyarrythmia and ventricular fibrillation. Now they serve as pacemakers for both tachy- and bradyarrhythmias and can act as cardioverters or defibrillators if required. Radiologists must be familiar with the appearances of these devices as their use becomes more widespread. In this article, the electrophysiology of these devices is briefly reviewed and the typical radiologic appearances are presented along with common radiologically recognizable complications.

Histopathological study following catheter guided radiofrequency current ablation of the slow pathway in a patient with atrioventricular nodal reentrant tachycardia.

The present study examined histological changes induced by catheter guided radiofrequency current in a patient with AV nodal reentrant tachycardia who underwent cardiac transplantation 1 week after ablation of the slow pathway. During the electrophysiology study AV nodal conduction curves were discontinuous and AV nodal reentry was induced. At the conclusion of the procedure there was no evidence of slow pathway function. Histological sections from the explanted heart demonstrated a sharply demarcated atrial lesion (5 x 5 x 4 mm) extending from the septal portion of the tricuspid annulus to the posterior border of the AV node. The lesion did not encompass the compact AV node. These observations support the hypothesis that the slow pathway is comprised of atrial approaches to the AV node and is distinct from the compact AV node.

Increased endothelial cell expression of platelet-endothelial cell adhesion molecule-1 during hyperoxic lung injury.

Lung injury is a frequent consequence of oxygen (O2) therapy administered to newborns and adults with respiratory distress. Acute exposure to hyperoxia results in a well-described pathophysiologic response in the lungs. Because inflammation is an important component of pulmonary O2 toxicity, we have an interest in identifying the inflammatory mediators that increase during hyperoxia. Platelet-endothelial cell adhesion molecule-1 (PECAM-1), a member of the immunoglobulin superfamily that is expressed at the junctions between endothelial cells, is essential to the transendothelial migration of leukocytes. We hypothesized that increased expression of PECAM-1 occurs in pulmonary endothelial cells during hyperoxic lung injury. Adult mice were exposed to 100% O2 for up to 96 h. We analyzed PECAM-1 expression by RNA blot hybridization, in situ hybridization, and immunohistochemistry. A increase in PECAM-1 mRNA was seen as soon as 2 d of hyperoxia relative to unexposed control mice. PECAM-1 mRNA and protein were found in endothelial cells of both large and small arteries. The expression of PECAM-1 in capillary vessels was further confirmed using in situ hybridization at the electron microscope level. This increase in PECAM-1 expression coincided with the appearance of leukocytes in lung tissue. These observations suggest that PECAM-1 expression is a relatively early step in the inflammation cascade, and intervention at this phase may be critical to the prevention of further damage.

Dexamethasone enhances P-selectin mRNA expression in hyperoxic rat lungs.

OBJECTIVE AND DESIGN: To test the hypothesis that glucocorticoid administration would diminish the lung expression of P-selectin mRNA in hyperoxia-exposed rats. ANIMALS: Adult male Sprague-Dawley rats were divided into 6 separate groups containing 10 to 13 animals per group. TREATMENT: Rats were dosed with 1 mg/kg of dexamethasone or vehicle only, ip. Immediately after dosing, animals were placed in > 95 % oxygen. Some animals were maintained in room air and are presented as 0 h of exposure to hyperoxia. Another group of animals was dosed with 10 mg/kg lipopolysaccharide (LPS) ip immediately after dosing with either dexamethasone or vehicle as above. METHODS: At 24 or 48 h, lung samples were obtained, and lung weight to body weight ratios calculated. In the LPS studies, samples were obtained 4 h after LPS dosing. In a subset of animals, lung sections were hybridized for P-selectin mRNA. All data except for hybridizations were analyzed with three-way ANOVA, with subsequent post-hoc testing. P-selectin hybridizations were quantified by counting the number of positive vessels per high-powered field, and subsequently analyzed by unpaired Student's t-test. Immunohistochemical analyses for P-selectin expression were also performed to determine whether changes in P-selectin mRNA were associated with differences in protein expression. All data are expressed as means +/- SEM. RESULTS: Rats dosed with dexamethasone had higher lung/body weight ratios after 24 and 48 h of exposure to hyperoxia than did similarly exposed rats dosed only with vehicle (at 48 h, 0.87 +/- 0.04 versus 0.65 +/- 0.06, respectively, P < 0.05). The higher ratios in hyperoxic animals dosed with dexamethasone were associated with much higher levels of lung expression for P-selectin mRNA than was observed in similarly exposed rats dosed with vehicle alone (at 48 h, 3.93 +/- 1.02, versus 0.20 +/- 0.06, respectively, P < 0.01). In contrast dexamethasone dosing lead to lower lung P-selectin mRNA expression in animals exposed to LPS (1.23 +/- 1.08 in dexamethasone dosed animals versus 6.80 +/- 0.92 in vehicle only dosed animals). Consistent with the mRNA data, P-selectin immunoreactivity increased as a function of hyperoxia-exposure time in animals dosed with dexamethasone, while immunoreactivity decreased as a function of hyperoxia-exposure time in animals dosed with vehicle only. CONCLUSIONS: Increased P-selectin mRNA combined with increased P-selectin protein expression in animals exposed to hyperoxia and dosed with dexamethasone suggests that enhanced expression of P-selectin may contribute to the greater lung injury and inflammation caused by hyperoxia in rats treated with dexamethasone.

Situational factors and behavioral self-predictions in the identification of clients at high risk to drop out of psychotherapy.

Two hundred and eight adults who requested outpatient treatment at a community mental health center were asked to complete brief questionnaires immediately prior to and after their first therapy session. Questionnaires contained items that pertained to self-predicted length of stay in psychotherapy, situational barriers to regular attendance, and past behavior in similar situations (e.g., appointment-keeping with other health care professionals). Therapists also were asked to make predictions with regard to client length of stay. Questionnaire data were analyzed via a series of double cross-validated multiple regression and discriminant function equations, and results indicated that client and therapist predictions of length of stay in therapy were the most stable and consistent correlates of attendance behavior.

Patients with rheumatoid arthritis at high risk for noncompliance with salicylate treatment regimens.

Recent studies indicate the adherence of many patients with rheumatoid arthritis (RA) to their treatment regimens is poor. Management of this problem depends on identification of noncompliant patients, followed by interventions to increase their level of adherence. In this study, 63 patients with RA receiving salicylate drugs completed a questionnaire during an outpatient visit. The questionnaire contained items believed to be predictive of future compliance, including patient self-predictions regarding future compliance, ratings of behavior in similar situations and barriers to compliance, such as ease of transportation to the clinic. Compliance was estimated via a salicylate assay that was taken during a subsequent outpatient appointment. Multivariate analyses of our data revealed that significant predictions could be made regarding future compliance, with 75% of the noncompliant patients correctly identified. Variables contributing significantly included behavioral self-predictions and a measure of current behavior in similar situations, as assessed by a salicylate assay that was collected during the 1st outpatient visit.

Deleterious effect of tracheal obstruction on type II pneumocytes in fetal sheep.

It was previously shown that tracheal obstruction accelerated fetal lung growth and eventually reversed the pulmonary hypoplasia in experimental diaphragmatic hernia. We have successfully developed a reversible tracheal obstruction technique in fetal sheep using balloon occlusion and showed that 3 wk of obstruction induced significant lung growth of the same magnitude as the tracheal ligation. The purpose of this study was to examine the effects of 1 and 3 wk of tracheal occlusion on the alveolar cell population with specific attention to the type II pneumocytes. We first showed that 1 wk of occlusion induced a significant increase in lung weight and in alveolar surface area. We then used the surfactant protein C (SP-C) mRNA as a specific marker of differentiated type II pneumocytes. Total RNA was isolated from fetal sheep lung with or without tracheal occlusion, and Northern blots were hybridized with a cDNA probe specific for the sheep SP-C. The results show a dramatic decrease in SP-C mRNA expression (8.8-fold, p < 0.01). In situ hybridization showed a marked decrease in the density of cells expressing SP-C, as well as the amount of SP-C mRNA expressed by the cells. The effect was present as early as 1 wk of occlusion. The sparseness of type II pneumocytes was further confirmed by electron microscopy. We thus conclude that tracheal obstruction causes a profound decrease in the number of type II pneumocytes in the lungs. Given the crucial role of type II pneumocytes in surfactant production, we could speculate that, if tracheal occlusion is able to accelerate lung growth, the final product is probably surfactant-deficient.