Natural IgM Blockade Limits Infarct Expansion and Left Ventricular Dysfunction in a Swine Myocardial Infarct Model

BACKGROUND

Acute coronary syndrome is the leading cause of mortality worldwide. However, treatment of acute coronary occlusion inevitably results in ischemia-reperfusion injury. Circulating natural IgM has been shown to play a significant role in mouse models of ischemia-reperfusion injury. A highly conserved self-antigen, nonmuscle myosin heavy chain II, has been identified as a target of pathogenic IgM. We hypothesized that a monoclonal antibody (m21G6) directed against nonmuscle myosin heavy chain II may inhibit IgM binding and reduce injury in a preclinical model of myocardial infarction. Thus, our objective was to evaluate the efficacy of intravenous m21G6 treatment in limiting infarct expansion, troponin release, and left ventricular dysfunction in a swine myocardial infarction model.

METHODS AND RESULTS

Massachusetts General Hospital miniature swine underwent occlusion of the midleft anterior descending coronary artery for 60 minutes, followed by 1 hour, 5-day, or 21-day reperfusion. Specificity and localization of m21G6 to injured myocardium were confirmed using fluorescently labeled m21G6. Treatment with m21G6 before reperfusion resulted in a 49% reduction in infarct size (P<0.005) and a 61% reduction in troponin-T levels (P<0.05) in comparison with saline controls at 5-day reperfusion. Furthermore, m21G6-treated animals recovered 85.4% of their baseline left ventricular function as measured by 2-dimensional transthoracic echocardiography in contrast to 67.1% in controls at 21-day reperfusion (P<0.05).

CONCLUSIONS

Treatment with m21G6 significantly reduced infarct size and troponin-T release, and led to marked preservation of cardiac function in our study. Overall, these findings suggest that pathogenic IgM blockade represents a valid therapeutic strategy in mitigating myocardial ischemia-reperfusion injury.

Mitral valve disease--morphology and mechanisms

Mitral valve disease is a frequent cause of heart failure and death. Emerging evidence indicates that the mitral valve is not a passive structure, but--even in adult life--remains dynamic and accessible for treatment. This concept motivates efforts to reduce the clinical progression of mitral valve disease through early detection and modification of underlying mechanisms. Discoveries of genetic mutations causing mitral valve elongation and prolapse have revealed that growth factor signalling and cell migration pathways are regulated by structural molecules in ways that can be modified to limit progression from developmental defects to valve degeneration with clinical complications. Mitral valve enlargement can determine left ventricular outflow tract obstruction in hypertrophic cardiomyopathy, and might be stimulated by potentially modifiable biological valvular-ventricular interactions. Mitral valve plasticity also allows adaptive growth in response to ventricular remodelling. However, adverse cellular and mechanobiological processes create relative leaflet deficiency in the ischaemic setting, leading to mitral regurgitation with increased heart failure and mortality. Our approach, which bridges clinicians and basic scientists, enables the correlation of observed disease with cellular and molecular mechanisms, leading to the discovery of new opportunities for improving the natural history of mitral valve disease.

Leaflet area as a determinant of tricuspid regurgitation severity in patients with pulmonary hypertension

BACKGROUND

Tricuspid regurgitation (TR) is a risk factor for mortality in pulmonary hypertension (PH). TR severity varies among patients with comparable degrees of PH and right ventricular remodeling. The contribution of leaflet adaptation to the pathophysiology of TR has yet to be examined. We hypothesized that tricuspid leaflet area (TLA) is increased in PH, and that the adequacy of this increase relative to right ventricular remodeling determines TR severity.

METHODS AND RESULTS

A prospective cohort of 255 patients with PH from pre and postcapillary pathogeneses was assembled from 2 centers. Patients underwent a 3-dimensional echocardiogram focused on the tricuspid apparatus. TLA was measured with the Omni 4D software package. Compared with normal controls, patients with PH had a 2-fold increase in right ventricular volumes, 62% increase in annular area, and 49% increase in TLA. Those with severe TR demonstrated inadequate increase in TLA relative to the closure area, such that the ratio of TLA:closure area <1.78 was highly predictive of severe TR (odds ratio, 68.7; 95% confidence interval, 16.2-292.7). The median vena contracta width was 8.5 mm in the group with small TLA and large closure area as opposed to 4.8 mm in the group with large TLA and large closure area.

CONCLUSIONS

TLA plays a significant role in determining which patients with PH develop severe functional TR. The ratio of TLA:closure area, reflecting the balance between leaflet adaptation versus annular dilation and tethering forces, is an indicator of TR severity that may identify which patients stand to benefit from leaflet augmentation during tricuspid valve repair.

Leaflet Area as a Determinant of Tricuspid Regurgitation Severity in Patients With Pulmonary Hypertension

Background—

Tricuspid regurgitation (TR) is a risk factor for mortality in pulmonary hypertension (PH). TR severity varies among patients with comparable degrees of PH and right ventricular remodeling. The contribution of leaflet adaptation to the pathophysiology of TR has yet to be examined. We hypothesized that tricuspid leaflet area (TLA) is increased in PH, and that the adequacy of this increase relative to right ventricular remodeling determines TR severity.

Methods and Results—

A prospective cohort of 255 patients with PH from pre and postcapillary pathogeneses was assembled from 2 centers. Patients underwent a 3-dimensional echocardiogram focused on the tricuspid apparatus. TLA was measured with the Omni 4D software package. Compared with normal controls, patients with PH had a 2-fold increase in right ventricular volumes, 62% increase in annular area, and 49% increase in TLA. Those with severe TR demonstrated inadequate increase in TLA relative to the closure area, such that the ratio of TLA:closure area <1.78 was highly predictive of severe TR (odds ratio, 68.7; 95% confidence interval, 16.2–292.7). The median vena contracta width was 8.5 mm in the group with small TLA and large closure area as opposed to 4.8 mm in the group with large TLA and large closure area.

Conclusions—

TLA plays a significant role in determining which patients with PH develop severe functional TR. The ratio of TLA:closure area, reflecting the balance between leaflet adaptation versus annular dilation and tethering forces, is an indicator of TR severity that may identify which patients stand to benefit from leaflet augmentation during tricuspid valve repair.

Myocardial scar imaging by standard single-energy and dual-energy late enhancement CT: Comparison with pathology and electroanatomic map in an experimental chronic infarct porcine model

BACKGROUND

Myocardial scar is a substrate for ventricular tachycardia and sudden cardiac death. Late enhancement CT imaging can detect scar, but it remains unclear whether newer late enhancement dual-energy (LE-DECT) acquisition has benefit over standard single-energy late enhancement (LE-CT).

OBJECTIVE

We aim to compare late enhancement CT using newer LE-DECT acquisition and single-energy LE-CT acquisitions with pathology and electroanatomic map (EAM) in an experimental chronic myocardial infarction (MI) porcine study.

METHODS

In 8 pigs with chronic myocardial infarction (59 ± 5 kg), we performed dual-source CT, EAM, and pathology. For CT imaging, we performed 3 acquisitions at 10 minutes after contrast administration: LE-CT 80 kV, LE-CT 100 kV, and LE-DECT with 2 postprocessing software settings.

RESULTS

Of the sequences, LE-CT 100 kV provided the best contrast-to-noise ratio (all P ≤ .03) and correlation to pathology for scar (ρ = 0.88). LE-DECT overestimated scar (both P = .02), whereas LE-CT images did not (both P = .08). On a segment basis (n = 136), all CT sequences had high specificity (87%-93%) and modest sensitivity (50%-67%), with LE-CT 100 kV having the highest specificity of 93% for scar detection compared to pathology and agreement with EAM (κ = 0.69).

CONCLUSIONS

Standard single-energy LE-CT, particularly 100 kV, matched better to pathology and EAM than dual-energy LE-DECT for scar detection. Larger human trials as well as more technical studies that optimize varying different energies with newer hardware and software are warranted.

Basic mechanisms of mitral regurgitation

Any structural or functional impairment of the mitral valve (MV) apparatus that exhausts MV tissue redundancy available for leaflet coaptation will result in mitral regurgitation (MR). The mechanism responsible for MV malcoaptation and MR can be dysfunction or structural change of the left ventricle, the papillary muscles, the chordae tendineae, the mitral annulus, and the MV leaflets. The rationale for MV treatment depends on the MR mechanism and therefore it is essential to identify and understand normal and abnormal MV and MV apparatus function.

Significant mitral regurgitation left untreated at the time of aortic valve replacement: a comprehensive review of a frequent entity in the transcatheter aortic valve replacement era

Significant mitral regurgitation (MR) is frequent in patients with severe aortic stenosis (AS). In these cases, concomitant mitral valve repair or replacement is usually performed at the time of surgical aortic valve replacement (SAVR). Transcatheter aortic valve replacement (TAVR) has recently been considered as an alternative for patients at high or prohibitive surgical risk. However, concomitant significant MR in this setting is typically left untreated. Moderate to severe MR after aortic valve replacement is therefore a relevant entity in the TAVR era. The purpose of this review is to present the current knowledge on the clinical impact and post-procedural evolution of concomitant significant MR in patients with severe AS who have undergone aortic valve replacement (SAVR and TAVR). This information could contribute to improving both the clinical decision-making process in and management of this challenging group of patients.

Late repair of ischemic mitral regurgitation does not prevent left ventricular remodeling: importance of timing for beneficial repair

BACKGROUND

Ischemic mitral regurgitation (MR) is a frequent complication of myocardial infarction associated with left ventricular (LV) dilatation and dysfunction, which doubles mortality. At the molecular level, moderate ischemic MR is characterized by a biphasic response, with initial compensatory rise in prohypertrophic and antiapoptotic signals, followed by their exhaustion. We have shown that early MR repair 30 days after myocardial infarction is associated with LV reverse remodeling. It is not known whether MR repair performed after the exhaustion of compensatory mechanisms is also beneficial. We hypothesized that late repair will not result in LV reverse remodeling.

METHODS AND RESULTS

Twelve sheep underwent distal left anterior descending coronary artery ligation to create apical myocardial infarction and implantation of an LV-to-left atrium shunt to create standardized moderate volume overload. At 90 days, animals were randomized to shunt closure (late repair) versus sham (no repair). LV remodeling was assessed by 3-dimensional echocardiography, dP/dt, preload-recruitable stroke work, and myocardial biopsies. At 90 days, animals had moderate volume overload, LV dilatation, and reduced ejection fraction (all P<0.01 versus baseline, P=NS between groups). Shunt closure at 90 days corrected the volume overload (regurgitant fraction 6 ± 5% versus 27 ± 16% for late repair versus sham, P<0.01) but was not associated with changes in LV volumes (end-diastolic volume 106 ± 15 versus 110 ± 22 mL; end-systolic volume 35 ± 6 versus 36 ± 6 mL) or increases in preload-recruitable stroke work (41 ± 7 versus 39 ± 13 mL mm Hg) or dP/dt (803 ± 210 versus 732 ± 194 mm Hg/s) at 135 days (all P=NS). Activated Akt, central in the hypertrophic process, and signal transducer and activator of transcription 3 (STAT3), a critical node in the hypertrophic stimulus by cytokines, were equally depressed in both groups.

CONCLUSIONS

Late correction of moderate volume overload after myocardial infarction did not improve LV volume or contractility. Upregulation of prohypertrophic intracellular pathways was not observed. This contrasts with previously reported study in which early repair (30 days) reversed LV remodeling. This suggests a window of opportunity to repair ischemic MR after which no beneficial effect on LV is observed, despite successful repair.

Assessment of mitral valve adaptation with gated cardiac computed tomography: validation with three-dimensional echocardiography and mechanistic insight to functional mitral regurgitation

BACKGROUND

Mitral valve (MV) enlargement is a compensatory mechanism capable of preventing functional mitral regurgitation (FMR) in dilated ventricles. Total leaflet area and its relation with closure area measured by 3-dimensional (3D) echocardiography have been related to FMR. Whether these parameters can be assessed with other imaging modalities is not known. Our objectives are to compare cardiac computed tomography (CT)-based measurements of MV leaflets with 3D echocardiography and determine the relationship of these metrics to the presence of FMR.

METHODS AND RESULTS

We used 2 cohorts of patients who had cardiac CT to measure MV total leaflet, closure, and annulus areas. In cohort 1 (26 patients), we validated these CT metrics to 3D echocardiography. In cohort 2 (66 patients), we assessed the relation of MV size with the presence of FMR in 3 populations: heart failure with FMR, heart failure without FMR, and normal controls. Cardiac CT and 3D echocardiography produced similar results for total leaflet (R(2)=0.97), closure (R(2)=0.89), and annulus areas (R(2)=0.84). MV size was the largest in heart failure without FMR compared with controls and patients with FMR (9.1 ± 1.7 versus 7.5 ± 1.0 versus 8.1 ± 0.9 cm(2)/m(2); P<0.01). Patients with FMR had reduced ratios of total leaflet to closure areas and total leaflet to annulus areas when compared with patients without FMR (P<0.01).

CONCLUSIONS

MV size measured by CT is comparable with 3D echocardiography. MV enlargement in cardiomyopathy suggests leaflet adaptation. Patients with FMR have inadequate adaptation as reflected by decreased ratios of leaflet area and areas determined by ventricle size (annulus and closure areas). These measurements provide additional insight into the mechanism of FMR.

Feasibility of aortic valve assessment with low dose prospectively triggered adaptive systolic (PTAS) cardiac computed tomography angiography

BACKGROUND

Cardiac computed tomography angiography (CTA) is feasible for aortic valve evaluation, but retrospective gated protocols required high radiation doses for aortic valve assessment. A prospectively triggered adaptive systolic (PTAS) cardiac CT protocol was recently described in arrhythmia using second-generation dual-source CT. In this study, we sought to evaluate the feasibility of PTAS CTA to assess the aortic valve at a low radiation dose.

FINDINGS

A retrospective cohort of 29 consecutive patients whom underwent PTAS protocols for clinical indications other than aortic valve assessment and whom also received echocardiography within 2 months of CT, was identified. Images were reviewed for aortic valve morphology (tricuspid/bicuspid/prosthetic) and stenosis (AS) by experienced blinded readers. Accuracy versus echocardiography and radiation doses were assessed.

CONCLUSIONS

PTAS CTA protocols using second-generation dual-source CT for aortic valve evaluation are feasible at low doses. This protocol should be investigated further in larger cohorts.

Mitral valve enlargement in chronic aortic regurgitation as a compensatory mechanism to prevent functional mitral regurgitation in the dilated left ventricle

OBJECTIVES

The aim of this study was to test the hypothesis that mitral valve (MV) enlargement occurring in chronic aortic regurgitation (AR) prevents functional mitral regurgitation (FMR).

BACKGROUND

Chronic AR causes left ventricular (LV) dilation, creating the potential for FMR. However, FMR is typically absent during compensated AR despite substantial LV enlargement. Increased mitral leaflet area has been identified in AR, but it is unknown whether increased MV size can represent a compensatory mechanism capable of preventing FMR.

METHODS

Database review of 816 patients with at least moderate AR evaluated the prevalence of FMR. A total of 90 patients were enrolled prospectively for 3-dimensional echocardiography (30 AR, 30 FMR, and 30 controls) to assess MV geometry including total leaflet area.

RESULTS

FMR was present in 5.6% of AR patients by database review. Prospectively, only 1 AR patient had more than mild FMR despite increased LV end-diastolic volume (82 ± 22, 86 ± 23, and 51 ± 12 cm(3)/m(2), respectively, for AR, FMR vs. control patients; p < 0.01) and similar sphericity index, annular area, and tethering distances compared with FMR. Total MV area was largest in AR (31.3% greater than normal), increasing significantly more than in FMR. The ratio of valve size to closure area was maintained in AR, whereas decreases in this ratio and LV ejection fraction independently predicted FMR.

CONCLUSIONS

FMR prevalence is low in chronic AR. MV leaflet area is significantly increased compared with control and FMR patients, preserving a normal relationship to the area needed for closure in the dilated LV. Understanding the mechanisms underlying this adaptation could lead to new therapeutic interventions to prevent FMR.

Gene profiling of left ventricle eccentric hypertrophy in aortic regurgitation in rats: rationale for targeting the β-adrenergic and renin-angiotensin systems

Aortic valve regurgitation (AR) imposes a severe volume overload to the left ventricle (LV), which results in dilation, eccentric hypertrophy, and eventually loss of function. Little is known about the impact of AR on LV gene expression. We, therefore, conducted a gene expression profiling study in the LV of rats with acute and severe AR. We identified 64 genes that were specifically upregulated and 29 that were downregulated out of 21,910 genes after 2 wk. Of the upregulated genes, a good proportion was related to the extracellular matrix. We subsequently studied a subset of 19 genes by quantitative RT-PCR (qRT-PCR) to see if the modulation seen in the LV after 2 wk persisted in the chronic phase (after 6 and 12 mo) and found that it did persist. Knowing that the adrenergic and renin-angiotensin systems are overactivated in our animal model, we were interested to see if blocking those systems using metoprolol (25 mg·kg−1·day−1) and captopril (100 mg·kg−1·day−1) would alter the expression of some upregulated LV genes in AR rats after 6 mo. By qRT-PCR, we observed that upregulations of LV mRNA levels encoding for procollagens type I and III, fibronectin, atrial natriuretic peptide, transforming growth factor-β2, and connective tissue growth factor were totally or partially reversed by this treatment. These observations provide a molecular rationale for a medical strategy aiming these systems in the medical treatment of AR and expand the paradigm in the study of this form of LV volume overload.

Comparative Study of Vasodilators in an Animal Model of Chronic Volume Overload Caused by Severe Aortic Regurgitation

Background— Aortic regurgitation (AR) is a disease of chronic left ventricular (LV) volume overload. Over time, AR will lead to LV dilatation, hypertrophy, and loss of function. There is currently no medical treatment proven effective to slow the evolution of this cardiomyopathy. Vasodilators were once thought to have protective effects, but recent publications have cast some doubts about their effectiveness. We hypothesized that drugs targeting the renin-angiotensin system should be more effective than those having no direct effect on the renin-angiotensin system.

Methods and Results— We designed a protocol comparing the effects of 3 vasodilators in a rat AR model (n=9 to 11 animals per group). The effects of a 6-month treatment of (1) nifedipine, (2) captopril, or (3) losartan were compared in male AR rats. Sham-operated and untreated AR animals were used as controls. Nifedipine-treated animals displayed hemodynamics, LV dilatation, hypertrophy, and loss of function similar to those of the untreated group. Both captopril and losartan were effective in improving hemodynamics, slow LV dilatation, hypertrophy, and dysfunction. Gene expression analysis confirmed the lack of effects of the nifedipine treatment at the molecular level.

Conclusions— Using an animal model of severe AR, we found that vasodilators targeting the renin-angiotensin system were effective to slow the development of LV remodeling and to preserve LV function. As recently shown in the most recent human clinical trial, nifedipine was totally ineffective. Targeting the renin-angiotensin system seems a promising avenue in the treatment of this disease, and clinical trials should be carefully designed to re-evaluate the effectiveness of angiotensin I–converting enzyme inhibitors or angiotensin II receptor blockers in AR.

ECG-guided immediate intervention at the time of primary PCI to reduce door-to-balloon time in ST-elevation myocardial infarction patients

BACKGROUND

In ST-segment elevation acute myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI), all efforts must be made to improve door-to-balloon (DTB) times. This study was designed to assess the impact of electrocardiographic-guided immediate intervention (EGII) without performing a complete coronary evaluation on DTB times and clinical outcomes of STEMI patients treated with primary PCI.

METHODS

Consecutive STEMI patients undergoing primary PCI at Laval Hospital between May 2006 and August 2007 were considered for inclusion. Patients with thrombolysis in myocardial infarction (TIMI) 2-3 flow in the culprit vessel on initial angiography and patients with previous coronary bypass surgery were excluded from the analysis. The primary evaluation was DTB time. Clinical outcomes consisted of cardiac death, reinfarction, revascularization or stroke.

RESULTS

Two hundred seventy-nine (279) patients were included in the present analysis. Eighty-seven (87) patients underwent EGII (Group 1) and 192 underwent PCI after a complete angiographic diagnostic evaluation (Group 2). Median catheterization laboratory DTB was 21 minutes in Group 1 and 25.5 minutes in Group 2 (p < 0.0001). The median DTB time was 80 minutes for patients in Group 1, compared to 90 minutes for patients in Group 2 (p = 0.01). More patients in Group 1 received timely reperfusion (DTB < 90 min) than patients in Group 2 (63% vs. 49%; p = 0.04). There was a trend towards reduced mortality in Group 1 compared to Group 2 (p = 0.11, unadjusted).

CONCLUSION

A strategy of EGII reduces DTB times with a possible impact on clinical outcomes in STEMI patients undergoing primary PCI.

A novel copper-regulated promoter system for expression of heterologous proteins in Schizosaccharomyces pombe

The increasing use of the fission yeast Schizosaccharomyces pombe as a model organism for elucidating the mechanisms of critical biological processes such as cell-cycle control, DNA replication, and stress-mediated signal transduction has fostered the development and utilization of expression systems for gene function analysis. Using the promoter of the ctr4(+) copper transporter gene from S. pombe, we created a series of vectors, named pctr4(+)-X, which regulate the expression of heterologous genes as a function of copper availability. In this system, the addition of copper ions at levels that are non-toxic to yeast cells represses gene expression, while copper deprivation strongly induces gene expression. Conveniently, changes of growth medium or carbon sources are not required to shut down or induce gene expression. The Cu-starvation-mediated inducible expression system is rapid, producing heterologous proteins within 3 h, with sustained expression of proteins that persists for several hours. The pctr4(+)-X expression vectors harbor unique restriction sites constructed in-frame to DNA sequences encoding for epitope tags, which facilitate the detection or purification of the heterologous proteins using commercially available antibodies and affinity columns. Furthermore, the pctr4(+)-X copper-regulatable protein expression vectors have been constructed with three different selectable markers, offering more versatility for studying gene function in fission yeast.

The fission yeast copper-sensing transcription factor Cuf1 regulates the copper transporter gene expression through an Ace1/Amt1-like recognition sequence

Transcriptional regulation of genes encoding critical components of copper transport is essential for copper homeostasis and growth in yeast. Analysis of regulatory regions in the promoter of the ctr4(+) copper transporter gene in fission yeast Schizosaccharomyces pombe reveals the identity of a conserved copper-signaling element (CuSE), which is recognized by the transcription factor Cuf1. We demonstrate that CuSE is necessary for transcriptional activation in response to copper deprivation conditions. Interestingly, the CuSE element bears a strong sequence similarity to the recognition site, denoted MRE (metal regulatory element), which is recognized by a distinct class of copper sensors required for copper detoxification, including Ace1 from Saccharomyces cerevisiae and Amt1 from Candida glabrata. When a consensus MRE from S. cerevisiae is introduced into S. pombe, transcription is induced by copper deprivation in a Cuf1-dependent manner, similar to regulation by Mac1, the nuclear sensor for regulating the expression of genes encoding components involved in copper transport in S. cerevisiae. UV-cross-linking experiments show that the Cuf1 protein directly binds the CuSE. These results demonstrate that the Cuf1 nutritional copper-sensing factor possesses a module that functions similarly to domains found in the Ace1/Amt1 class of metalloregulatory factors, which allows the protein to act through a closely related MRE-like sequence to regulate copper transport gene expression in S. pombe.

Species-specific regulation of alternative splicing in the C-terminal region of the p53 tumor suppressor gene

Alternative splicing occurs in the C-terminal region of the p53 tumor suppressor gene between two alternative 3' splice sites in intron 10. This alternative splicing event has been detected in murine cells, but not in rat or human tissues. In this paper, we have characterized the pattern of p53 alternative splicing in cell lines from five different species. Our results confirm that p53 alternative splicing is species-specific, being detected only in cell lines of rodent origin. Using transient transfection assays, we have established that the rat p53 gene undergoes efficient alternative splicing in both mouse and rat cell lines, thus demonstrating that it has all the necessary cis -acting sequences to be alternatively spliced. In contrast, we were unable to detect any usage of the human alternative 3' splice site under the same experimental conditions. Thus, the low levels or absence of alternatively spliced p53 mRNA in rat and human cell lines seems to be the result of different mechanisms. Our results support the hypothesis that there are species-specific mechanisms implicated in the regulation of p53 activity.

Establishment and immunocharacterization of an immortalized pancreatic cell line derived from the H-2Kb-tsA58 transgenic mouse

This study describes the establishment and characterization of an immortalized cell line derived from the pancreas of an adult H-2Kb-tsA58 transgenic mouse. These cells, designated IMPAN for IMmortalized PANcreatic cells, displayed a cobblestone appearance typical of confluent epithelial cells and a distinct polarity in the organization of their cytoplasmic organelles. Immunocytochemical studies revealed that all IMPAN cells stained positively for a wide range of markers characteristic of pancreatic acinar cells, namely the secretory products alpha-amylase, chymotrypsinogen, DNAse, the lectinlike secretory protein PAP (pancreatitis associated protein), and the zymogen granule membrane proteins GP-2 and gp300. They also stained positively for carbonic anhydrase II and cytokeratin 19, two proteins characteristic of pancreatic duct cells, as well as for rab3A, a small GTP-binding protein specifically localized in pancreatic islet cells. No reactivity was ever obtained with insulin antibodies. Taken together, these results show that the IMPAN cells exhibit a phenotype comparable to exocrine pancreatic acinar cells. However the expression of some proteins more specific to duct and islet cells make them similar to in vivo or in vitro growing acinar cells. The cell line should be a valuable model to study the mechanisms of growth, differentiation, and transformation of the exocrine pancreatic acinar cell.

Cell-specific expression of the ZPK gene in adult mouse tissues

ZPK is a recently identified human putative protein kinase gene that encodes an unusual serine/threonine kinase containing two potential leucine zipper motifs similar to those found in transcription factors as well as in members of the newly discovered mixed-lineage family of protein kinases. To study the normal biological function of ZPK, we have isolated a mouse ZPK cDNA and examined the pattern of ZPK mRNA expression in adult mouse tissues by Northern blot and in situ hybridization analyses. The predicted open reading frame of this cDNA encodes an 888-amino-acid protein that shares 95% overall identity with its human counterpart. By Northern blot analysis, we detected expression of ZPK mRNA in the brain of adult mice, but not in any other tissue tested. In situ hybridization analysis of mouse brain sections revealed specific association of ZPK mRNA with neuronal cell populations, primarily in the hippocampus, the cerebral cortex, and the Purkinje cell layer of the cerebellum. Interestingly, a remarkable pattern of cell-type-specific expression was also found in the epithelial compartment of various organ systems, including stomach, small intestine, liver, and pancreas, as well as in the seminiferous tubules of mature testes. Taken together, these observations suggest that ZPK could play a role in development, function, and maintenance of a variety of specialized cells.

The U1 small nuclear ribonucleoprotein/5' splice site interaction affects U2AF65 binding to the downstream 3' splice site

In the gene of the neural cell adhesion molecule, the 5' splice site of the alternate exon 18 plays an important role in establishing regulated splicing profiles. To understand how the 5' splice site of exon 18 contributes to splicing regulation, we have investigated the interaction of the U2AF65 splicing factor to pre-mRNAs that contained portions of the constitutive exon 17 or the alternate exon 18 fused to exon 19 and separated by a shortened intron. Despite sharing an identical 3' splice site, only the pre-mRNA that contained a portion of exon 17 and its associated 5' splice site displayed efficient U2AF65 cross-linking. Strikingly, a G-->U mutation at position +6 of the intron, converting the 5' splice site of exon 18 into that of exon 17, stimulated U2AF65 crosslinking. The improved cross-linking efficiency of U2AF65 to a pre-mRNA carrying the 5' splice site of exon 17 required the integrity of the 5' end of U1 but not of U2 small nuclear RNA. Our results indicate that neural cell adhesion molecule 5' splice site sequences influence U2AF65 binding through a U1 small nuclear ribonucleoprotein/U2AF interaction that occurs at the commitment stage of spliceosome assembly, before stable binding of the U2 small nuclear ribonucleoprotein. Thus, the 5' splice sites of exons 17 and 18 differentially affect U2AF65 binding to the 3' splice site of exon 19. Factors that modulate U1 small nuclear ribonucleoprotein binding to these 5' splice sites may play a critical role in regulating exon 18 skipping.

Quantitative analysis of T and B cell subsets in healthy and sick premature infants

This work proposes a serial quantitative analysis of the numbers and percentages of B and T cell subsets in 104 consecutive premature infants (PI) between birth and six months of age as compared with 21 normal term infants. First, in order to ascertain the effects of perinatal distress at birth (respiratory distress, neonatal asphyxia) on certain parameters of the immune system, the PI were divided into two groups. One comprised 36 healthy preterms, the other, 68 preterms with perinatal distress. It was then shown that healthy PI differed from full-term infants by their higher absolute numbers of T cells (CD2-positive) and helper T cell subset (CD4-positive). These increases in CD2- and CD4-positive cells correlated with gestational age (GA). An increase in B lymphocytes (CD20-positive cells) was also documented but no correlation with GA could be seen. Secondly, perinatal distress was found to be concomitant with transient decrease in percentages and absolute numbers of CD2- and CD4-positive cells, particularly in PI of less than 28 weeks of gestation. The B cells (CD20- and CD21-positive cells) were not different in absolute numbers. Respiratory distress had a more discernable effect than fetal asphyxia on the immune system. Finally, no immunological parameters tested could at any time predict the occurrence of infection in PI during the first 6 months of life.

Modulation of the immunosuppressive activities by blastocoelic fluid during rabbit pregnancy

Temporal variation in immunosuppressive activity was determined in biological samples such as embryo-foetal fluids (blastocoelic- or amino-allantoic fluid) and blood collected from pregnant and pseudopregnant rabbits. Each of the fluids to be analyzed was pre-incubated with mitogen stimulated human lymphocytes for 48 h and then inhibition of [3H]thymidine incorporation or IL-2 receptor expression was estimated. Both means of assessing immunosuppression indicated variations in the suppressive activity throughout pregnancy. This was observed in embryo-foetal fluids but not in autologous peripheral blood nor in homologous pseudopregnant blood. At days 9-13 of pregnancy, the immunosuppressive effects of blastocoelic fluids were higher than that of the autologous sera, reached a peak at days 12 and 13 and declined thereafter, to reach the lowest levels. In order to further characterize the biological activity of day-12 blastocoelic fluid and autologous serum, they were submitted to ultracentrifugation. No suppressive activity could be demonstrated in the lipoprotein fractions. But all the activity was found in the protein fraction. Precipitation with cold ethanol confirmed that the biologically active compound was a protein. Furthermore, results obtained after ultrafiltration suggest biologically active compounds of high mol. wt (greater than 300 kDa). From the above findings, we can suggest that in the rabbit, there is no pregnancy specific systemic immunosuppression. We can also infer that (1) the immuno-tolerance of the mother towards the embryo is more due to a localized effect; (2) this effect decreases with the progression of gestation and (3) a high mol. wt factor is responsible for the immunosuppression.

Phosphorylation of purified insulin receptor by cAMP kinase

Highly purified insulin receptor was shown to be a substrate for cAMP kinase. Approximately 1 phosphate was incorporated per molecule of receptor, and the cAMP kinase's affinity for the receptor was at least as high as its affinity for histone. The sites phosphorylated by cAMP kinase seemed distinct from those phosphorylated by the protein kinase C. Phosphorylation by cAMP kinase had no effect on the ability of several monoclonal antibodies to recognize the receptor or on the insulin-binding activity of the receptor. However, cAMP phosphorylation partially inhibited the tyrosine kinase activity of the receptor (approximately 25%). These results suggest that catecholamine-induced resistance to insulin may be partly due to a direct phosphorylation of the receptor by cAMP kinase and a subsequent inhibition of the ability of the receptor kinase to be activated by insulin.

A solid-phase competitive radioimmunoassay for the insulin receptor

A radioimmunoassay for the insulin receptor has been developed. In this assay, unlabeled receptor competes with 125I-labeled receptor for binding to monoclonal anti-receptor antibodies immobilized on microtiter wells coated with affinity-purified anti-mouse immunoglobulin G. This assay was highly reproducible and could detect 7 ng (14 fmol) of insulin receptor. By utilizing monoclonal antibodies to various antigenic regions of the receptor, different parts of the receptor molecule could be examined. By utilizing antibodies to the cytoplasmic domain of the receptor, an assay was developed which was not influenced by the presence of insulin and could equally detect the insulin receptor from different species (rat and human) and different tissues (placenta and brain). By utilizing antibodies to an autophosphorylation site of the receptor, the assay was shown capable of detecting the extent of phosphorylation of the receptor. Finally, this assay was utilized to monitor the decrease in insulin receptors in lysates of insulin-treated human lymphocytes. This radioimmunoassay should be useful for monitoring both the number and status of the insulin receptor under a variety of physiological conditions.

Protein kinase C directly phosphorylates the insulin receptor in vitro and reduces its protein-tyrosine kinase activity

The beta subunit of purified insulin receptor is phosphorylated on a serine residue by purified preparations of protein kinase C (ATP: protein phosphotransferase, EC 2.7.1.37). This phosphorylation is inhibited by antibodies to protein kinase C and stimulated by phospholipids, diacylglycerol, and Ca2+. The phosphorylation of the receptor by protein kinase C does not affect its insulin-binding activity but does inhibit by 65% the receptor's intrinsic tyrosine-specific protein kinase activity (ATP: protein-tyrosine O-phosphotransferase, EC 2.7.1.112). These results indicate that activators of protein kinase C, such as phorbol esters, desensitize cells to insulin by direct protein kinase C action on the insulin receptor.

Purification and characterization of the human brain insulin receptor

The insulin receptor from human brain cortex was purified by a combination monoclonal antibody affinity column and a wheat germ agglutinin column. This purified receptor preparation exhibited major protein bands of apparent Mr = 135,000 and 95,000, molecular weights comparable to those for the alpha and beta subunits of the purified human placental and rat liver receptors. A minor protein band of apparent Mr = 120,000 was also observed in the brain receptor preparation. Crosslinking of 125I-insulin to all three receptor preparations was found to preferentially label a protein of apparent Mr = 135,000. In contrast, cross-linking of 125I-labeled insulin-like growth factor I to the brain preparation preferentially labeled the protein of apparent Mr = 120,000. The purified brain insulin receptor was found to be identical with the placental insulin receptor in the amount of neuraminidase-sensitive sialic acid and reaction with three monoclonal antibodies to the beta subunit of the placental receptor. In contrast, a monoclonal antibody to the insulin binding site recognized the placental receptor approximately 300 times better than the brain receptor. These results indicate that the brain insulin receptor differs from the receptor in other tissues and suggests that this difference is not simply due to the amount of sialic acid on the receptor.

Development of a reverse enzymoallergosorbent test (REAST) to detect timothy-specific IgE antibodies. Comparison with RAST

Radioallergosorbent test (RAST) for the measurement of IgE antibodies has been introduced more than 15 years ago and a number of technical modifications have since improved its sensitivity and reproducibility. The test has been applied to the diagnosis of allergy and to determine changes in the levels of IgE antibodies following immunotherapy. However, specific IgG antibodies are raised during such a therapy and can interfere with the RAST. We have developed a reverse enzymoallergosorbent test (REAST) where microtiter plates are first coated with a purified polyclonal anti-IgE antibody, then with the serum to test and finally with peroxidase-labeled antigen. This assay is antigen specific as shown by the significant inhibition of binding of the labeled antigen in presence of unlabeled specific antigen (greater than 95%) and the absence of inhibition in presence of irrelevant antigens. The values found in atopic patients (85 subjects) were significantly higher than in the non-atopic donors (35 subjects) (1.14 U +/- 1.20 vs. 0.01 U +/- 0.02, P less than 0.0005) and there was a good correlation with the Pharmacia RAST (P less than 0.0005). The levels of specific IgE by both REAST and RAST correlated well with the clinical symptomatology.

Effects of H1 and H2 receptor agonists on nonspecific proliferative response of human peripheral blood lymphocytes

Histamine is known to modulate immune responses through the induction of suppressor cell subsets. The inhibition studies with antagonists suggest that the H2 agonist accounts for most of the suppression. This work studies the effects of various concentrations of 3-methyl histamine (as negative control), histamine, and pure H1 (2-methyl histamine, 2-pyridyl ethylamine) and H2 (4-methyl histamine, dimaprit) receptor agonists on the mitogenic (phytohemagglutinin A) proliferative response of normal human lymphocytes. At high concentrations of agonists (10(-3), 10(-4) M) the suppression induced by the two types of agonists is comparable to that of histamine. At lower concentrations (10(-6) M) the suppression is seen only in the presence of the H2 agonist. The suppression induced by the two agonists is generally reversed in the presence of an H2 receptor antagonist. The H1 receptor antagonist did not abolish and even increased the suppression induced by histamine and the two agonists.

Expression of a functional human insulin receptor from a cloned cDNA in Chinese hamster ovary cells

We have placed human insulin receptor cDNA into a vector under the control of the simian virus 40 (SV40) early promoter and tested its function by transient expression in microinjected Xenopus oocytes and by expression in stably transformed CHO cells. The precursor and the alpha and beta subunits of the receptor were detected by immunoprecipitation from extracts of these cells. The human insulin receptor expressed in CHO cells specifically binds 125I-labeled insulin but not insulin-like growth factor I, displays insulin-stimulated autophosphorylation of the beta subunit, and mediates insulin-stimulated 2-deoxyglucose uptake. We conclude that the human insulin receptor is synthesized, processed normally, and functional in this heterologous cell system.

Absence of correlation between the degree of alveolitis and antibody levels to Micropolysporum faeni

Specific IgG antibody (Ab) levels to Micropolysporum faeni (MF) antigen were measured in three study groups: 29 farmers of whom one had acute, two chronic and 26 with a past history of Farmer's lung disease (FLD), 91 clinically asymptomatic but exposed farmers and 23 unexposed donors. This study confirms the greater sensitivity of enzyme linked immunosorbent assay (ELISA) over double immunodiffusion (DID): 34 (37%) sera negative by DID were positive by ELISA and only two (4%) were positive by DID and negative by ELISA. Antibody levels to MF were higher in the serum of farmers whether symptomatic (113.2 +/- 196.1 u) or not (25.2 +/- 64.7 u) than in that of unexposed donors (1.05 +/- 1.46 u), (P less than 0.001). In a subgroup of farmers, antibody levels were compared in the serum and bronchoalveolar lavage (BAL) fluid; the levels were higher in the serum than in BAL fluids in all farmers except the only patient with acute FLD. A significant correlation was seen between Ab levels of the serum and BAL fluids. Finally, no correlation was seen between the serum antibody levels and the total number of cells or the percentage of lymphocytes found in BAL fluids, either in the subjects with a history of FLD or the asymptomatic group.

A rubella outbreak among dental students: description of the outbreak and analysis of control measures

From February to April 1982, rubella was diagnosed in 17 Washington University dental students. The affected students represented 4.8% of all dental students and 21% of susceptible students. Because a high likelihood of rubella transmission was perceived, three adjacent university hospitals undertook an emergency program to ensure immunity to rubella in all personnel. The program reached 84.6% of all target personnel, but only 36% of physicians (p less than 0.001). We estimated that the program increased the level of rubella immunity from 92.2% to 98.1%, at a total cost of $140,274 of which $29,990 was in excess of ordinary expenditures. Our experience indicates that schools training health professionals face the possibility of rubella outbreaks unless they ensure rubella immunity in all students. The experience also supports the value of ongoing programs to ensure rubella immunity in hospital personnel. Without such programs, hospitals may be forced to undertake emergency programs that are likely to be disruptive and expensive and may have relatively little immediate measurable impact.

Abnormal bronchoalveolar lavage in asymptomatic dairy farmers. Study of lymphocytes

Bronchoalveolar lavage (BAL) was performed on 24 asymptomatic dairy farmers. Thirteen had serum precipitins to Micropolyspora faeni (MF) antigens (Group 1), and 11 were seronegative control subjects (Group 2). All were nonsmokers and had no history of previous lung disease. Thirteen of 24 subjects (9 in Group 1 and 4 in Group 2) had a high percentage of lymphocytes (greater than or equal to 20%) in their BAL. The T-lymphocyte subpopulations as estimated by OKT3, OKT4, and OKT8 monoclonal antibody reactivity were measured in peripheral blood lymphocytes; OKT3 = 58.5 +/- 15.6% for Group 1, and 58.5 +/- 8.7% for Group 2; OKT4 = 40.6 +/- 10.7% and 39.9 +/- 10.0%; OKT8 = 21.5 +/- 10.6% and 22.4 +/- 8.0%, respectively (p = NS). These lymphocyte characteristics were also similar when subjects with a high percentage of lymphocytes in BAL were compared to those with a normal percentage. Specific (MF-coated) chicken erythrocyte lymphocytotoxicity (Group 1, 45.2 +/- 29.5%, Group 2, 49.2 +/- 23.4%), and nonspecific lymphocytotoxicity (Group 1, 43.9 +/- 28.6%, Group 2, 37.9 +/- 18.0%) were also similar. We conclude that a large number of asymptomatic dairy farmers have an increased percentage of lymphocytes in their BAL ("alveolitis") and that peripheral blood lymphocytes in these subjects have normal subpopulations, as assessed by monoclonal antibodies, and normal lymphocytotoxicity.

Production of HMG-3 by limited trypsin digestion of purified high-mobility-group nonhistone chromatin proteins

Three isolated nonhistone proteins (HMG-1, HMG-2 and HMG-E) have been purified from chicken erythrocyte chromatin without exposure to overt denaturing conditions, and subjected to limited proteolysis. When treated with trypsin, the three proteins exhibited similar patterns of degradation, as judged by SDS and acid/urea gel electrophoresis. In particular, the first product, P1 (a relatively stable intermediate in each digestion), was a protein analogous to HMG-3, a principal degradation product in preparations of calf thymus high-mobility-group proteins. At least in the case of HMG-E, the products formed by tryptic attack on P1 are the two individual DNA binding domains of HMG-E. P1 derived from HMG-E and one of the individual DNA binding domains of HMG-E were purified by chromatography on columns containing DNA-cellulose or phosphocellulose. The properties of these two portions of HMG-E are consistent with our recently postulated three-domain structure for HMG-1 and its homologs (Reeck, G.R., Isackson, P.J. and Teller, D.C. (1982) Nature 300, 76-78). Thus, P1 consists of two DNA-binding domains of approximately equal molecular weight covalently linked together. From chromatography on DNA-cellulose columns, it is clear that P1 binds to DNA more tightly than does HMG-E. The highly acidic C-terminal domain of HMG-E (which is removed by trypsin in generating P1) thus counteracts the DNA binding of the two other domains of HMG-E (at least in the protein's interaction with purified DNA).

Purification of single- and double-length M13 virions by polyacrylamide gel electrophoresis

Complete separation of single- and double-length M13 virions from each other and from still-longer phage particles was achieved by electrophoresis of phage stocks through 2.5% polyacrylamide gels.