Cost-effectiveness of catheter ablation in patients with ventricular tachycardia

BACKGROUND

This study evaluated the cost-effectiveness of catheter ablation therapy versus amiodarone for treating ventricular tachycardia (VT) in patients with structural heart disease. The analysis used a societal perspective for a hypothetical cohort of VT patients with implantable cardioverter-defibrillators, who were experiencing frequent shocks.

METHODS AND RESULTS

We calculated incremental cost-effectiveness of ablation relative to amiodarone over 5 years after treatment initiation. Event probabilities were from the Chilli randomized clinical trial (Chilli Cooled Ablation System, Cardiac Pathways Corporation, Sunnyvale, Calif), the literature, and a consensus panel. Costs were from 1998 national Medicare reimbursement schedules. Quality-of-life weights (utilities) were estimated using an established preference measurement technique. In a hypothetical cohort of 10 000 patients, 5-year costs were higher for patients undergoing ablation compared with amiodarone therapy ($21 795 versus $19 075). Ablation also produced a greater increase in quality of life (2.78 versus 2.65 quality-adjusted life-years [QALYs]). This yielded a cost-effectiveness ratio of $20 923 per QALY gained for ablation compared with amiodarone. Results were relatively insensitive to assumptions about ablation success and durability. In less severe patients with good ejection fractions who suffer their first VT episode, the incremental cost-effectiveness ratio was $6028 per QALY gained. These cost-effectiveness ratios are within the range generally thought to warrant technology adoption.

CONCLUSIONS

This study demonstrates that, from a societal perspective, catheter ablation appears to be a cost-effective alternative to amiodarone for treating VT patients.

Use of the TAT in the assessment of DSM-IV cluster B personality disorders

The Social Cognition and Object Relations Scale (SCORS), developed by Western, Lohr, Silk, Kerber, and Goodrich (1985), is a diagnostic instrument used to assess an array of psychological functioning by using clinical narratives such as the Thematic Apperception Test (TAT; Murray, 1943) stories. This study investigated the utility of the SCORS to differentiate between Diagnostic and Statistical Manual of Mental Disorders (4th ed. [DSM-IV]; American Psychiatric Association, 1994) antisocial personality disorder (ANPD), borderline personality disorder (BPD), narcissistic personality disorder (NPD), and Cluster C personality disorder (CPD). A sample of 58 patients was separated into four groups: ANPD (n = 9), BPD (n = 21; 18 with a primary BPD diagnosis and 3 with prominent borderline traits who met 4 of the 5 DSM-IV criteria necessary for a BPD diagnosis), NPD (n = 16; 8 with a primary NPD diagnosis and 8 with prominent narcissistic traits who met 4 of the 5 DSM-IV criteria necessary for a NPD diagnosis), and CPD (n = 12). These groups were then compared on the 8 SCORS variables by using 5 TAT cards (1, 2, 3BM, 4, and 13MF). Spearman-Brown correction for 2-way mixed effects model of reliability for the 8 SCORS variables ranged from .70 to .95. The results of categorical and dimensional analyses indicate that (a) SCORS variables can be used to differentiate ANPD, BPD, and NPD; (b) the BPD group scored significantly lower (greater maladjustment) than did the CPD group on certain variables; (c) the BPD group scored significantly lower (greater maladjustment) than did the NPD group on all 8 SCORS variables; (d) the ANPD group scored significantly lower than did the NPD group on certain variables; (e) certain variables were found to be empirically related to the total number of DSM-IV ANPD, BPD, and NPD criteria; and (f) certain variables were found to be empirically related to Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989) Personality disorder scales. The results of this study are discussed in terms of clinical utility, conceptual, and theoretical implications.

Selective recognition of mannose by the human eosinophil Charcot-Leyden crystal protein (galectin-10): a crystallographic study at 1.8 A resolution

The role(s) of the eosinophil Charcot-Leyden crystal (CLC) protein in eosinophil or basophil function or associated inflammatory processes is yet to be established. Although the CLC protein has been reported to exhibit weak lysophospholipase activity, it shows virtually no sequence homology to any known member of this family of enzymes. The X-ray crystal structure of the CLC protein is very similar to the structure of the galectins, members of a beta-galactoside-specific animal lectin family, including a partially conserved galectin carbohydrate recognition domain (CRD). In the absence of any known natural carbohydrate ligand for this protein, the functional role of the CLC protein (galectin-10) has remained speculative. Here we describe structural studies on the carbohydrate binding properties of the CLC protein and report the first structure of a carbohydrate in complex with the protein. Interestingly, the CLC protein demonstrates no affinity for beta-galactosides and binds mannose in a manner very different from those of other related galectins that have been shown to bind lactosamine. The partial conservation of residues involved in carbohydrate binding led to significant changes in the topology and chemical nature of the CRD, and has implications for carbohydrate recognition by the CLC protein in vivo and its functional role in the biology of inflammation.

C/EBPbeta and GATA-1 synergistically regulate activity of the eosinophil granule major basic protein promoter: implication for C/EBPbeta activity in eosinophil gene expression

Eosinophil granule major basic protein (MBP) is expressed exclusively in eosinophils and basophils in hematopoietic cells. In our previous study, we demonstrated a major positive regulatory role for GATA-1 and a negative regulatory role for GATA-2 in MBP gene transcription. Further analysis of the MBP promoter region identified a C/EBP (CCAAT/enhancer-binding protein) consensus binding site 6 bp upstream of the functional GATA-binding site in the MBP gene. In the cell line HT93A, which is capable of differentiating towards both the eosinophil and neutrophil lineages in response to retinoic acid (RA), C/EBPalpha mRNA expression decreased significantly concomitant with eosinophilic and neutrophilic differentiation, whereas C/EBPbeta expression was markedly increased. Electrophoretic mobility shift assays (EMSAs) showed that recombinant C/EBPbeta protein could bind to the potential C/EBP-binding site (bp -90 to -82) in the MBP promoter. Furthermore, we have demonstrated that both C/EBPbeta and GATA-1 can bind simultaneously to the C/EBP- and GATA-binding sites in the MBP promoter. To determine the functionality of both the C/EBP- and GATA-binding sites, we analyzed whether C/EBPbeta and GATA-1 can stimulate the MBP promoter in the C/EBPbeta and GATA-1 negative Jurkat T-cell line. Cotransfection with C/EBPbeta and GATA-1 expression vectors produced a 5-fold increase compared with cotransfection with the C/EBPbeta or GATA-1 expression vectors individually. In addition, GST pull-down experiments demonstrated a physical interaction between human GATA-1 and C/EBPbeta. Expression of FOG (riend ATA), which binds to GATA-1 and acts as a cofactor for GATA-binding proteins, decreased transactivation activity of GATA-1 for the MBP promoter in a dose-dependent manner. Our results provide the first evidence that both GATA-1 and C/EBPbeta synergistically transactivate the promoter of an eosinophil-specific granule protein gene and that FOG may act as a negative cofactor for the eosinophil lineage, unlike its positively regulatory function for the erythroid and megakaryocyte lineages.

Clinical consequences of alterations in platelet transfusion dose: a prospective, randomized, double-blind trial

BACKGROUND

The dose-response relationship for platelet transfusion has become increasingly important as the use of platelet transfusion has grown.

STUDY DESIGN AND METHODS

One hundred fifty-eight prophylactic apheresis platelet transfusions were administered to 46 patients undergoing high-dose therapy followed by hematopoietic progenitor cell transplantation in a prospective, randomized, double-blind, multiple-crossover study. Transfusions were administered in pairs, differing only in platelet content. Each pair consisted of a lower-dose platelet component (LDP) and a higher-dose platelet component (HDP) administered in random order to the same patient. LDPs contained a mean of 3.1 x 10(11) platelets (range, 2.3-3.5 x 10(11)), and HDPs contained a mean of 5.0 x 10(11) platelets (range, 4.5-6.1 x 10(11)). Patients with active bleeding and those who were refractory to platelet transfusions were excluded.

RESULTS

The mean posttransfusion platelet count increment with LDP was 17,010 per microL, and that with HDP was 31,057 per microL (p<0.0001). Only 37 percent of LDPs resulted in platelet count increments of at least 20,000 per microL, whereas 81 percent of HDPs resulted in increments above this level (p<0.0001). The mean transfusion-free interval with LDP was 2.16 days, whereas that with HDP was 3.03 days (p<0.01). Administration of LDPs was associated with a 39 to 82 percent increase in the relative risk (per day) of requiring subsequent platelet transfusions (p<0.0001).

CONCLUSION

As compared to the administration of HDPs, the administration of LDPs for prophylactic transfusion in hematopoietic progenitor cell transplant patients results in a lower platelet count increment, a lower likelihood of obtaining a posttransfusion platelet increment >20,000 per microL, a shorter transfusion-free interval, and a greater relative risk per day of requiring additional transfusions.

Cost effectiveness of recombinant human insulin-like growth factor I therapy in patients with ALS

OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a fatal, degenerative neuromuscular disease characterised by a progressive loss of voluntary motor activity. Recombinant human insulin-like growth factor I (rhIGF-I) has been shown to be useful in treating ALS. The purpose of this study was to examine the cost effectiveness of rhIGF-I therapy in patients who have ALS.

DESIGN

We performed a cost-effectiveness analysis from the societal perspective on 177 patients who received treatment with rhIGF-I or placebo in a North American randomised clinical trial. We estimated the incremental cost-effectiveness ratio of rhIGF-I using resource utilisation and functional status measurements from the clinical trial. Costs were estimated from 1996 US Medicare reimbursement schedules. Utility weights were elicited from ALS healthcare providers using the standard gamble technique.

MAIN OUTCOME MEASURES AND RESULTS

The overall cost per quality-adjusted life-year (QALY) gained for rhIGF-I therapy compared with placebo was $US67,440. For the subgroups of patients who were progressing rapidly or were in earlier stages of disease at enrolment, rhIGF-I cost $US52,823 and $US43,197 per QALY gained, respectively.

CONCLUSIONS

Treatment with rhIGF-I is most cost effective in ALS patients who are either in earlier stages of the disease or progressing rapidly. The cost effectiveness of rhIGF-I therapy compares favourably with treatments for other chronic progressive diseases.

Models of lineage switching in hematopoietic development: a new myeloid-committed eosinophil cell line (YJ) demonstrates trilineage potential

A new human leukemia cell line with an eosinophilic phenotype, designated YJ, was established from the peripheral blood cells of a patient with chronic myelomonocytic leukemia (CMMoL) with eosinophilia. When cultured in RPMI 1640 medium containing 10% fetal bovine serum, most YJ cells were myeloblastoid with a small number of the cells having eosinophilic granules. Cell surface markers in the YJ cells were positive for CD33 and were negative for CD34, CD16 and CD23. The eosinophilic characteristics of YJ cells were confirmed by histochemical staining with Fast-Green/Neutral-Red and by the expression of mRNAs for eosinophil-associated granule proteins, eosinophil cationic protein (ECP), eosinophil-derived neurotoxin (EDN), eosinophil peroxidase (EPO), and major basic protein (MBP), and for the Charcot-Leyden crystal (CLC) protein. The YJ cells could be induced towards monocytic differentiation by stimulation with phorbol 12-myristate 13-acetate (PMA). The monocytic characteristics of YJ cells treated with PMA were confirmed by morphological analysis with alpha-naphthyl butyrate esterase staining, by CD14 expression, and by increased expression of Egr-1 mRNA. Furthermore, YJ cells could be differentiated towards the neutrophil lineage by stimulation with all-trans retinoic acid (RA). YJ cells treated in vitro with 2 microM RA differentiated into metamyelocytes and band neutrophils, and increased the number of nitroblue tetrazolium (NBT)-positive cells and increased gp91phox mRNA expression. Thus, the YJ cell line exhibited eosinophilic characteristics, but was able to differentiate to the monocytic or neutrophilic lineages in response to PMA or RA, respectively. The expression of genes for transcription factors involved in myeloid differentiation was evaluated by Northern blot analysis. Increased expression of Egr-1 was observed with macrophage differentiation. In contrast, increased expressions of C/EBPbeta and MZF-1 mRNA occurred with neutrophilic differentiation. The YJ cell line should be useful for elucidating the molecular mechanisms governing lineage switching from the eosinophil to monocytic or neutrophil lineages.

Stem cell factor influences mast cell mediator release in response to eosinophil-derived granule major basic protein

Stem cell factor (SCF) is an important mast cell growth, differentiation, and survival factor. We investigated whether SCF influenced the response of mouse mast cells to an IgE-independent stimulus, eosinophil-derived granule major basic protein (MBP). Mouse bone marrow cultured mast cells (BMCMC) were derived in either concanavalin-stimulated mouse spleen conditioned medium (CM) or SCF. The cloned growth, factor-independent mast cell line Cl.MC/C57.1 was also studied. BMCMC in SCF exhibited cytochemical staining properties, protease and histamine content, and increased serotonin uptake consistent with more mature differentiated mast cells as compared with BMCMC in CM or Cl.MC/ C57.1 cells. BMCMC in SCF released serotonin, 14C-labeled arachidonic acid metabolites and tumor necrosis factor-alpha (TNF-alpha) on stimulation with MBP, while no response was seen from either BMCMC in CM or Cl.MC/C57.1 cells. All three mast cell populations released mediators on stimulation with the cationic MBP analog, poly-L-arginine, indicating that the cationic charge did not explain the selective response of BMCMC in SCF to eosinophil-derived granule MBP. These findings show that SCF significantly influences mast cell differentiation and the responsiveness of mast cells to eosinophil-derived granule MBP.

Mechanisms of transcription in eosinophils: GATA-1, but not GATA-2, transactivates the promoter of the eosinophil granule major basic protein gene

Granule major basic protein (MBP) is expressed exclusively in eosinophils, basophils, and placental trophoblasts. To identify the cis-elements and transcription factors involved in regulating MBP expression, we subcloned 3.2 kb of sequence upstream of the exon 9 transcriptional start site (P2 promoter) and serial 5' deletions into the pXP2 luciferase reporter vector. An 80% decrement in promoter activity was obtained when MBP sequences between bp -117 to -67 were deleted. To identify transcription factors that bind to and transactivate through the bp -117 to -67 region, we first compared the upstream genomic sequences of human and murine MBP; a potential GATA binding consensus site was conserved in the 50-bp region between the two genes. To determine which GATA proteins bind this consensus site, we performed electrophoretic mobility shift assays (EMSAs), which showed that both GATA-1 and GATA-2 can bind to this consensus site. To determine the functionality of this site, we tested whether GATA-1 and GATA-2, either individually or in combination, can transactivate the MBP promoter in the Jurkat T cell line. Cotransfection with a GATA-1 expression vector produced 20-fold augmentation of MBP promoter activity, whereas GATA-2 had no activity. In contrast, combined cotransfection of GATA-1 and GATA-2 decreased the ability of GATA-1 to transactivate the MBP promoter by approximately 50%. Our results provide the first evidence for a GATA-1 target gene in eosinophils, a negative regulatory role for GATA-2 in MBP expression, and possibly eosinophil gene transcription in general during myelopoiesis.

Forced GATA-1 expression in the murine myeloid cell line M1: induction of c-Mpl expression and megakaryocytic/erythroid differentiation

The "zinc-finger" transcription factor GATA-1 was first shown in cells of erythroid lineage. It is also expressed in cells of other hematopoietic lineages including megakaryocytes, mast cells, and eosinophils. GATA-1 is now considered to be one of the central regulators in hematopoietic cell differentiation. To further analyze the role of GATA-1 in controlling differentiation from hematopoietic stem cells, we investigated the phenotypic changes induced by the overexpression of murine GATA-1 in the murine myeloid leukemic cell line, M1. Forced expression of GATA-1 induced the appearance of erythroid cells and megakaryocytes as assessed by cellular morphology, acetylcholinesterase activity, and expression of platelet factor 4 and beta-globin mRNA synthesis. Because the c-mpl ligand, thrombopoietin, plays an important role in megakaryopoiesis, the expression of c-mpl and c-mpl ligand (thrombopoietin) mRNA was analyzed by Northern blot and reverse transcription-polymerase chain reaction (RT-PCR) in M1 cells overexpressing GATA-1. The c-mpl ligand mRNA was equally expressed both in parental M1 cells and in those transfected with the GATA-1 expression vector. In contrast, the mRNA expression of c-mpl was increased only in GATA-1 expressing M1 cells differentiated towards erythroid and megakaryocyte lineages. The increased expression of c-mpl mRNA induced by GATA-1 raised the question as to whether or not GATA-1 transactivated the c-mpl promoter. The activity of the c-mpl promoter in the presence of cotransfected GATA-1 was significantly increased compared with that of the control. A plasmid with the mutated GATA-binding site did not show transactivation ability in the cotransfection with a GATA expression vector. These findings suggest that the upregulation of c-mpl induced by GATA-1 expression in M1 cells is closely associated with erythroid and megakaryocytic differentiation.

Vesicular transport of Charcot-Leyden crystal protein in f-Met peptide-stimulated human basophils

The ultrastructural localization of Charcot-Leyden crystal (CLC) protein during f-Met-peptide-induced degranulation of human basophils was analyzed at multiple times after stimulation. In this secretion model, piecemeal and anaphylactic degranulation occurred sequentially in stimulated cells and were followed by reconstitution of granule contents. This analysis showed that granule number and alteration and location of gold-labeled, formed CLCs changed over time. CLCs were extruded from granules and remained attached to plasma membranes early after stimulation. At later times, similar structures reappeared in granules in quantity. Smooth-membrane-bound vesicles, analyzed by number, by visible particle contents (or lack of contents) and by gold labeling for CLC protein, showed that empty vesicles increased at the earliest time sampled (0 time) and plunged thereafter in actively extruding and completely degranulated cells. Vesicles containing granule particles were elevated initially at 10 s and at later times. Gold-labeled CLC-protein-containing vesicles were of either empty or particle-filled varieties, and both types were involved with CLC protein transport out of cells at early times and into cells at later times as basophils recovered. Thus, vesicle transport of CLC protein is a mechanism for producing piecemeal degranulation and endocytotic recovery of released CLC protein from human basophils. This vesicular shuttle may be an effector mechanism for widespread piecemeal losses from granules in basophils in inflammatory sites in vivo in human disease.

Patient characteristics associated with diagnostic imaging evaluation of persistent low back problems

STUDY DESIGN

Post hoc analysis of data from the National Low Back Pain Study, a prospective observational multicenter study of patients referred for the evaluation and treatment of persistent low back problems.

OBJECTIVE

To identify patient characteristics associated with use of particular diagnostic imaging examinations in patients with persistent low back problems.

SUMMARY OF BACKGROUND DATA

The Agency for Health Care Policy and Research clinical practice guidelines on low back problems suggest that the use of particular diagnostic imaging tests for a given patient should be based on specific characteristics of that patient.

METHODS

Use of diagnostic imaging examinations in 2,374 patients with persistent low back problems who were enrolled in the National Low Back Pain Study from 1986 to 1991 was analyzed. Stepwise logistic regression was used to identify patient characteristics that distinguish between enrollees who underwent particular imaging studies.

RESULTS

Characteristics that distinguished patients who had undergone magnetic resonance imaging from those who had received only lumbo-sacral spine radiographs included higher socioeconomic status, greater resource use in the preceding 12 months, more functional impairment, presence of sciatica, and presence of neurologic signs/symptoms suggestive of nerve root compromise. Suspected soft tissue involvement was characteristic of enrollees who had undergone magnetic resonance imaging, whereas suspected structural involvement characterized patients who received noncontrast computed tomography. Only nonclinical factors, such as higher annual household income, disability compensation, and male gender distinguished enrollees who had undergone both magnetic resonance imaging and computed tomography-myelography from those who received only computed tomography-myelography.

CONCLUSION

Particular patient socioeconomic and clinical characteristics are associated with receipt of specific imaging studies in evaluation of persistent low back problems.

Persistent low back pain in patients suspected of having herniated nucleus pulposus: radiologic predictors of functional outcome--implications for treatment selection

PURPOSE

To assess the relationship between imaging findings, therapy, and functional outcome in patients with persistent low back pain who are suspected of having herniated nucleus pulposus.

MATERIALS AND METHODS

Data collected during a multicenter, longitudinal study were retrospectively analyzed (n = 1,084). Multivariate regression was used to determine the association between imaging findings, therapy, and functional outcome. The patient outcome measure was disability days: the number of days the patient was unable to perform work-related activities.

RESULTS

In patients with at least one normal advanced (imaging other than plain radiography) diagnostic study or with an unconfirmed diagnosis of herniated nucleus pulposus, outcome at 2-year follow-up was no better in patients who were treated than in those who were not. In patients with only abnormal advanced imaging results or with a concordant diagnosis based on clinical and imaging findings, outcome was better in patients who underwent surgery than in those treated nonsurgically. Patients with a free fragment, protrusion, or extrusion that was treated surgically had fewer disability days than patients treated nonsurgically.

CONCLUSION

Advanced diagnostic imaging studies can play an important role in treatment selection in patients with persistent low back pain who are suspected of having herniated nucleus pulposus.

Trends in diagnostic imaging for low back pain: has MR imaging been a substitute or add-on?

PURPOSE

To assess whether magnetic resonance (MR) imaging has replaced other diagnostic imaging modalities in the evaluation of persistent low back pain.

MATERIALS AND METHODS

Data on diagnostic imaging use in 2,374 adult patients with persistent low back pain in 1987-1990 were analyzed. Multiple logistic regression was used to estimate the annual adjusted odds of lumbosacral spine radiography, MR imaging, unenhanced computed tomography (CT), or CT myelography use. The national cost of diagnostic imaging for persistent low back pain in 1990 relative to 1987 was estimated.

RESULTS

The adjusted odds of performing MR imaging in 1990 relative to 1987 was 3.44 (95% confidence interval, 2.63, 4.51), which reflects an estimated increase from 22 studies per 100 enrollees in 1987 to 75 studies per 100 enrollees in 1990. Use of MR imaging in combination with radiography, unenhanced CT, or CT myelography increased. The additional national cost of diagnostic imaging for persistent low back pain in 1990 relative to 1987 was estimated at $70-$176 million.

CONCLUSION

MR imaging was used primarily as an add-on rather than a substitute for other imaging modalities in the evaluation of persistent low back pain. Thus, the volume and cost of diagnostic imaging for persistent low back pain have increased.

Localization of Charcot-Leyden crystal protein in individual morphological phenotypes of human basophils stimulated by f-Met peptide

BACKGROUND

Human basophils undergo anaphylactic degranulation, characterized by extrusion of membrane-free granules, and piecemeal degranulation, characterized by progressive removal of granule contents in the absence of granule extrusion. F-Met peptide stimulates a degranulation continuum in human basophils that includes both forms of secretion. Charcot-Leyden crystal protein is stored in the granules of unstimulated human basophils.

OBJECTIVE

The objective of this study was to determine the subcellular localization of the Charcot-Leyden crystal protein in individual morphological basophil phenotypes that are stimulated by f-Met peptide and are associated with secretion.

METHODS

A post-embedding immunogold analysis was used to detect changes in the subcellular sites of Charcot-Leyden crystal protein in human basophils stimulated with f-Met peptide. Human basophils from normal donors were purified by countercurrent centrifugal elutriation and Percoll density gradients, stimulated to degranulate with 1 micron f-Met peptide (or incubated in buffer controls), and recovered for histamine assay, electron microscopy and immunogold labelling. Specificity controls included omission of the primary antibody and substitution of the primary antibody with non-immune normal rabbit IgG or with Charcot-Leyden crystal protein-Sepharose-absorbed primary antibody.

RESULTS

The results showed new sites of labelling and different densities of labelling for Charcot-Leyden crystal protein in distinctive basophil phenotypes stimulated by f-Met peptide. New sites for Charcot-Leyden crystal protein included nucleus, cytoplasm, degranulation channel, degranulation channel membrane, plasma membrane, and a newly recognized granule population similar to primary granules in eosinophils. These new sites, as well as previously documented sites of Charcot-Leyden crystal protein (granules, intragranular Charcot-Leyden crystals, cytoplasmic vesicles) showed variable labelling when analysed by phenotype. Other sites (besides intragranular Charcot-Leyden crystals) of formed Charcot-Leyden crystals included cytoplasm, degranulation channel, extracellular space and, rarely, nucleus. Analysis of cytoplasmic vesicles, total granules and altered granules, and gold particles in subcellular compartments in seven identifiable phenotypes revealed that f-Met peptide stimulated human basophils to empty their granules by transporting Charcot-Leyden crystal protein in vesicles to the plasma membrane in the absence of granule extrusion in cells exhibiting piecemeal degranulation. In cells exhibiting anaphylactic degranulation, gold-labelled Charcot-Leyden crystals were extruded to the cells' exterior in concert with granule particles and concentric dense membranes contained within granules. Completely degranulated cells had a high density of plasma membrane gold label that was associated with numerous gold-laden endocytotic cytoplasmic vesicles. Basophils reconstituted their main granule population, within which Charcot-Leyden crystals resided, in part by endocytosis of previously released plasma membrane-bound Charcot-Leyden crystal protein. Completely recovered cells displayed decreased Charcot-Leyden crystal protein labelling of the plasma membrane and vesicle compartments, the presence of a highly labelled new granule subset that resembled Charcot-Leyden crystal protein-containing primary granules in eosinophils, and the highest density of granule and intragranular Charcot-Leyden crystal gold labelling of all phenotypes that developed after stimulation.

CONCLUSION

Seven individual f-Met peptide-activated human basophil phenotypes labelled by an ultrastructural immunogold method to detect subcellular sites of Charcot-Leyden crystal protein showed changing distributions of this protein which document the capability of human basophils to undergo complex release and recovery reactions that may be pertinent to the functions of Charcot-Leyden crystal protein and the capabilit

Anion, cation, and zwitterion selectivity of phospholemman channel molecules

Phospholemman (PLM), a 72-amino acid membrane protein with a single transmembrane domain, forms taurine-selective ion channels in lipid bilayers. Because taurine forms zwitterions, a taurine-selective channel might have binding sites for both anions and cations. Here we show that PLM channels indeed allow fluxes of both cations and anions, making instantaneous and voltage-dependent transitions among conformations with drastically different ion selectivity characteristics. This surprising and novel ion channel behavior offers a molecular explanation for selective taurine flux across cell membranes and may explain why molecules in the phospholemman family can induce cation- or anion-selective conductances when expressed in Xenopus oocytes.

Atrial rhythm after atrioventricular junctional ablation

Atrioventricular (AV) junctional ablation followed by pacemaker implantation is an established treatment for patients with refractory paroxysmal atrial arrhythmias. The stability of the underlying atrial rhythm after AV junctional ablation is unknown. This study evaluates the atrial rhythm after AV junctional ablation in 49 patients with medically refractory atrial arrhythmias. The group included 25 men and 24 women, of whom 36 had known structural heart disease. Paroxysmal atrial fibrillation was the primary rhythm disturbance in 41 patients, whereas 8 manifested either atrial tachycardias or atrial flutter. All patients had failed therapy with > or = 1 antiarrhythmic drug. Chronic pacing modes were DDIR or DDDR, with mode switching in 15 patients and VVIR in 34 patients. After AV junctional ablation, chronic antiarrhythmic drug therapy was prescribed in only 4 patients (8%). Routine electrocardiograms (ECGs; 6.5 +/- 6.1/patient) during long-term follow-up (18.6 +/- 15.6 months) showed that 7 patients (14%) had an atrial arrhythmia detected on all ECGs, 30 patients (61%) had sinus or atrial-paced rhythms on all recordings, and 12 patients (25%) had both atrial arrhythmias and sinus rhythm documented. Sinus or an atrial-paced rhythm was present on the last available ECG in 33 of 49 patients (67%). Pacing mode was not a predictor of continued sinus rhythm. In conclusion, most patients with a history of paroxysmal atrial tachyarrhythmias will not convert to chronic atrial arrhythmias after AV junctional ablation, even in the absence of antiarrhythmic drug therapy. Use of dual-chamber pacing modes will allow maintenance of at least intermittent atrial function in these patients.

Eosinophil-fibroblast interactions. Granule major basic protein interacts with IL-1 and transforming growth factor-beta in the stimulation of lung fibroblast IL-6-type cytokine production

To test the hypothesis that eosinophil major basic protein (MBP) is an important regulator of fibroblast effector function, we characterized the effects of MBP on human lung fibroblast production of the IL-6-type cytokines, IL-6, IL-11, and leukemia inhibitory factor. Unstimulated fibroblasts did not produce substantial quantities of these cytokines, while IL-1 and TGF-beta(1) stimulated these cytokines in a potent fashion. MBP at doses &lt; or = 44 micrograms/ml did not stimulate IL-6-type cytokine production. It did, however, interact in a synergistic, dose- and time-dependent fashion with rIL-1-alpha and TGF-beta(1) to further increase IL-6-type cytokine elaboration. These MBP-induced increases in cytokine production were associated with proportionate alterations in mRNA accumulation. In contrast, eosinophil-derived neurotoxin did not regulate fibroblast cytokine production, and MBP did not augment fibroblast granulocyte-macrophage-CSF, or type I collagen production, or fibroblast proliferation in this culture system. The effects of MBP could not be attributed to cell cytotoxicity or contaminants in the MBP preparations. They were, however, at least partially charge mediated, since heparin abolished the effects of MBP on IL-1-stimulated cells, and the surrogate cationic molecule poly-L-arginine mimicked the stimulatory effects of MBP on fibroblast IL-6-type cytokine elaboration. These studies demonstrate that MBP interacts in a synergistic fashion with rIL-1-alpha or TGF-beta(1) to further augment fibroblast IL-6-type cytokine production. They also demonstrate that this stimulation is pretranslationally mediated and due, in part, to the cationic nature of the MBP molecule. MBP regulation of fibroblast cytokine production may play an important role in the pathogenesis of eosinophilic disorders of the airway or other organs.

Eosinophil-fibroblast interactions. Granule major basic protein interacts with IL-1 and transforming growth factor-beta in the stimulation of lung fibroblast IL-6-type cytokine production

To test the hypothesis that eosinophil major basic protein (MBP) is an important regulator of fibroblast effector function, we characterized the effects of MBP on human lung fibroblast production of the IL-6-type cytokines, IL-6, IL-11, and leukemia inhibitory factor. Unstimulated fibroblasts did not produce substantial quantities of these cytokines, while IL-1 and TGF-beta(1) stimulated these cytokines in a potent fashion. MBP at doses < or = 44 micrograms/ml did not stimulate IL-6-type cytokine production. It did, however, interact in a synergistic, dose- and time-dependent fashion with rIL-1-alpha and TGF-beta(1) to further increase IL-6-type cytokine elaboration. These MBP-induced increases in cytokine production were associated with proportionate alterations in mRNA accumulation. In contrast, eosinophil-derived neurotoxin did not regulate fibroblast cytokine production, and MBP did not augment fibroblast granulocyte-macrophage-CSF, or type I collagen production, or fibroblast proliferation in this culture system. The effects of MBP could not be attributed to cell cytotoxicity or contaminants in the MBP preparations. They were, however, at least partially charge mediated, since heparin abolished the effects of MBP on IL-1-stimulated cells, and the surrogate cationic molecule poly-L-arginine mimicked the stimulatory effects of MBP on fibroblast IL-6-type cytokine elaboration. These studies demonstrate that MBP interacts in a synergistic fashion with rIL-1-alpha or TGF-beta(1) to further augment fibroblast IL-6-type cytokine production. They also demonstrate that this stimulation is pretranslationally mediated and due, in part, to the cationic nature of the MBP molecule. MBP regulation of fibroblast cytokine production may play an important role in the pathogenesis of eosinophilic disorders of the airway or other organs.

Vesicular transport of Charcot-Leyden crystal protein in tumor-promoting phorbol diester-stimulated human basophils

Secretion from human basophils (HB) that are stimulated with a phorbol ester takes place with slower kinetics than typically regulated secretion, which is stimulated by the IgE-mediated mechanism associated with classical granule exocytosis. Phorbol ester stimulation of HB induces emptying of granule contents (with retention of granule containers) and increases the number of cytoplasmic vesicles, an anatomic process similar to one termed piecemeal degranulation (PMD), which is a secretory process originally described in HB that migrate from the blood in vivo into contact allergy skin lesions. Charcot-Leyden crystal (CLC) protein is a basophil granule-associated protein that is readily imaged by using a postembedding immunogold procedure. This method was used to localize this granule protein in phorbol ester-stimulated, isolated human peripheral blood basophil cytoplasmic vesicles in samples collected within a time frame for which histamine was secreted. The results of this study showed that the proportion of cytoplasmic vesicles that were gold-labeled in stimulated HB, which indicated the presence of CLC protein, increased significantly over unstimulated cells at 2, 5, and 10 minutes after stimulation. Additionally, CLC protein-labeled vesicles in the cells that were stimulated for 10 minutes significantly exceeded the number in stimulated cells at 0, 30, and 45 minutes after exposure to phorbol ester. Thus, transport vesicles carrying a granule-associated protein (CLC protein) were increased in phorbol ester-stimulated HB in the time frame for histamine secretion and the anatomic development of PMD. These findings support vesicular transport as a major mechanism for effecting PMD, which is morphologically the most frequent activation anatomy displayed by HB in human disease in vivo.

Interleukin-5 receptor alpha subunit gene regulation in human eosinophil development: identification of a unique cis-element that acts lie an enhancer in regulating activity of the IL-5R alpha promoter

Further functional and biochemical characterization of the nuclear factor(s) which interacts with the EOS1 enhancer-like element in the IL-5R alpha promoter is currently in progress. Since different transcription factors recognize and interact with DNA in distinct fashions and with distinct structural motifs, we have modeled potential binding of the EOS1 factor to its cis-element based upon its methylation interference pattern (Fig. 2), using a cylindrical DNA helical projection (Fig. 6). Over a length of two helical turns, all nuclear protein contacts indicated by methylation interference map to one side of the DNA helix, suggesting that EOS1 binds in the major groove, across the minor groove, and on only one side of the helix. Further review of the model also reveals a potential diad symmetry for the binding site, suggestive of binding by a homodimer and consistent with the formation of the two DNA-protein complexes in our electrophoretic mobility shift experiments that could represent interactions with monomer versus dimer. Comparison of the EOS1 binding motif to similar models for the binding of other transcription factor families for which structural crystallographic and/or binding data is available suggests a similarity of the EOS1 complex to that of the bacterial helix-turn-helix phage lambda and 434 repressor-operator complexes, and the Cys4 zinc finger glucocorticoid response element (GRE) DNA-binding motifs, all of which show similar diad symmetry and binding in the major groove on one side of the DNA. The possibility that EOS1 functions as a GRE is being investigated, especially since there is a consensus AP-1 site at bp -440 to -432 of the IL-5R alpha promoter, immediately adjacent to the EOS1 binding site (see Fig. 5 in reference [36]) and AP-1/GRE interactions have been identified for composite response elements in the regulation of a number of different genes. The identification or cloning of EOS1, a potentially novel and eosinophil lineage-active transcription factor, should enhance our understanding of the processes involved in eosinophil development in particular and myeloid lineage commitment and differentiation in general.

Crystal structure of human Charcot-Leyden crystal protein, an eosinophil lysophospholipase, identifies it as a new member of the carbohydrate-binding family of galectins

BACKGROUND

The Charcot-Leyden crystal (CLC) protein is a major autocrystallizing constituent of human eosinophils and basophils, comprising approximately 10% of the total cellular protein in these granulocytes. Identification of the distinctive hexagonal bipyramidal crystals of CLC protein in body fluids and secretions has long been considered a hallmark of eosinophil-associated allergic inflammation. Although CLC protein possesses lysophospholipase activity, its role(s) in eosinophil or basophil function or associated inflammatory responses has remained speculative.

RESULTS

The crystal structure of the CLC protein has been determined at 1.8 A resolution using X-ray crystallography. The overall structural fold of CLC protein is highly similar to that of galectins -1 and -2, members of an animal lectin family formerly classified as S-type or S-Lac (soluble lactose-binding) lectins. This is the first structure of an eosinophil protein to be determined and the highest resolution structure so far determined for any member of the galectin family.

CONCLUSIONS

The CLC protein structure possesses a carbohydrate-recognition domain comprising most, but not all, of the carbohydrate-binding residues that are conserved among the galectins. The protein exhibits specific (albeit weak) carbohydrate-binding activity for simple saccharides including N-acetyl-D-glucosamine and lactose. Despite CLC protein having no significant sequence or structural similarities to other lysophospholipase catalytic triad has also been identified within the CLC structure, making it a unique dual-function polypeptide. These structural findings suggest a potential intracellular and/or extracellular role(s) for the galectin-associated activities of CLC protein in eosinophil and basophil function in allergic diseases and inflammation.

Changing the differentiation program of hematopoietic cells: retinoic acid-induced shift of eosinophil-committed cells to neutrophils

The mechanisms by which hematopoietic progenitor cells become lineage-committed remain poorly understood. A cloned subline of the AML14 cell line (AML14.3D10) that spontaneously differentiates to eosinophilic myelocytes in the absence of cytokine stimulation was obtained by limiting dilution. This subline exhibits augmented expression of interleukin-5 (IL-5) receptor alpha subunit mRNA and synthesizes all major eosinophil granule proteins. Exposure of this cell line to all-trans retinoic acid (ATRA) causes loss of eosinophilic granules and fast green staining within 48 hours, without cell death. In addition, mRNA for the IL-5 receptor alpha subunit becomes undetectable by 48 hours and the cells lose responsiveness to IL-5. Major basic protein, measured as a marker of eosinophilic granule content, decreases from more than 16 pg/cell to undetectable levels by 5 days after ATRA. Concomitant with the loss of major basic protein and fast green staining, surface expression of CD16 becomes detectable and is maximum by 10 days after ATRA. mRNA for the granulocyte colony-stimulating factor (G-CSF) receptor becomes detectable by day 5, and the cells become responsive to G-CSF. At this time, the cells appear morphologically as mature neutrophils and can reduce nitroblue tetrazolium. With continued culture, the neutrophilic cells die and the culture becomes repopulated with eosinophilic myelocytes. These findings show that it is possible to change the differentiation program of hematopoietic cells even after they show evidence of advanced lineage commitment. The AML14.3D10 subclone of AML14 will be a valuable model for study of the transcriptional regulation of the eosinophil and neutrophil differentiation programs and lineage-specific gene expression.