Publications by authors named "Eric A Swanson"

16 Publications

  • Page 1 of 1

Epithelial Inclusions in Gallbladder May Mimic Parasite Infection.

Am J Clin Pathol 2019 08;152(3):399-402

University of Utah, Salt Lake City.

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http://dx.doi.org/10.1093/ajcp/aqz054DOI Listing
August 2019

Epithelial Inclusions in Gallbladder Specimens Mimic Parasite Infection: Histologic and Molecular Examination of Reported Cystoisospora belli Infection in Gallbladders of Immunocompetent Patients.

Am J Surg Pathol 2018 10;42(10):1346-1352

Department of Pathology.

Recent publications have described epithelial cytoplasmic vacuoles and inclusions incidentally noted within gallbladder epithelium and concluded that they represent coccidian parasite infection, in particular, Cystoisospora belli. We identified 8 gallbladder specimens from our institution in the past 3 years in which this diagnosis was suggested or in which similar epithelial alterations were prominent. Molecular analysis was performed on the 8 gallbladder specimens and on 3 positive control specimens: small bowel biopsies from acquired immunodeficiency syndrome patients with diarrhea. Polymerase chain reaction using primers designed to amplify an internal transcribed spacer (ITS2) in the C. belli ribosomal gene cluster was performed on the DNA samples. All 8 gallbladder specimens were negative for amplification, while a product consistent with C. belli was amplified from all 3 positive controls. Histologically, the gallbladder cytoplasmic inclusions stained diffusely positive for Grocott-Gomori's methenamine silver and Periodic acid-Schiff with diastase. In contrast, sections from a positive control small bowel biopsy demonstrated organisms that were negative for Grocott-Gomori's methenamine silver and showed a distinct capsular and punctate internal staining on Periodic acid-Schiff with diastase in various parasite forms. Together, the lack of molecular evidence of C. belli and the distinct morphologic and special staining patterns in these gallbladders compared with positive control small bowel suggest that these epithelial changes do not represent true C. belli infection. Our results suggest that gallbladders of immunocompetent patients may occasionally show epithelial changes that can morphologically mimic C. belli infection. Pathologists should be aware of this histologic variant to minimize unnecessary treatment, testing, and patient anxiety.
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http://dx.doi.org/10.1097/PAS.0000000000001094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6133732PMC
October 2018

Estimating Medicare and Patient Savings From the Use of Bevacizumab for the Treatment of Exudative Age-related Macular Degeneration.

Am J Ophthalmol 2018 07 12;191:135-139. Epub 2018 Apr 12.

Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA.

Purpose: The Medicare cost savings from the use of bevacizumab in the United States for the treatment of exudative age-related macular degeneration (AMD) were estimated by replacing the use of bevacizumab with ranibizumab and aflibercept.

Design: Retrospective trend study.

Methods: Main outcome measures were spending by Medicare as tracked by Current Procedural Terminology (CPT) codes for intravitreal injections (67028) and treatment-specific J-codes (J0178, J2778, J9035, J3490, and J3590) for inhibitors of vascular endothelial growth factor. These claims were identified from the Medicare Provider Utilization and Payment Data from the Centers for Medicare and Medicaid Services among fee-for-service (FFS) Medicare beneficiaries from 2012 to 2015. The 2008 claims were acquired from the 100% fee-for-service (FFS) Part B Medicare Claims File.

Results: The use of bevacizumab from 2008 to 2015 resulted in an estimated savings of $17.3 billion, which corresponded to a $13.8 billion savings to Medicare and a $3.5 billion savings to patients. This amount underestimated the actual cost savings to Medicare providers, since approximately 30% of Medicare-eligible recipients received care within Medicare Advantage plans and were not included in this analysis.

Conclusions: The cost savings from the use of bevacizumab from 2008 to 2015 for Medicare fee-for-service patients undergoing treatment for exudative AMD was estimated at $17.3 billion. Additional savings over the $17.3 billion would have accrued from the use of bevacizumab if diagnostic categories such as diabetic macular edema and retinal vein occlusion were included in this study.
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http://dx.doi.org/10.1016/j.ajo.2018.04.008DOI Listing
July 2018

Estimating Public and Patient Savings From Basic Research-A Study of Optical Coherence Tomography in Managing Antiangiogenic Therapy.

Am J Ophthalmol 2018 Jan 7;185:115-122. Epub 2017 Dec 7.

Casey Eye Institute, Oregon Health & Science University, Portland, Oregon. Electronic address:

Purpose: To compare patient and Medicare savings from the use of optical coherence tomography (OCT) in guiding therapy for neovascular age-related macular degeneration (nvAMD) to the research investments made in developing OCT by the National Institutes of Health (NIH) and the National Science Foundation (NSF).

Design: Observational cohort study.

Methods: Main outcome measures were spending by Medicare as tracked by Current Procedural Terminology codes on intravitreal injections (67028), retinal OCT imaging (92134), and anti-vascular endothelial growth factor (anti-VEGF) treatment-specific J-codes (J0178, J2778, J9035, J3490, and J3590). These claims were identified from the Medicare Provider Utilization and Payment Data from the Centers for Medicare and Medicaid Services among fee-for-service (FFS) Medicare beneficiaries from 2012 to 2015; 2008 claims were acquired from the 100% FFS Part B Medicare Claims File. OCT research costs were determined by searching for grants awarded by NIH and NSF from inception to 2015. All costs and savings were discounted by 3% annually and adjusted for inflation to 2015 dollars.

Results: From 2008 to 2015, the United States government and nvAMD patients have accrued an estimated savings of $9.0 billion and $2.2 billion, respectively, from the use of OCT to guide personalized anti-VEGF treatment. The $9.0 billion represents a 21-fold return on government investment into developing the technology through NIH and NSF grants.

Conclusions: Although an overall cost-benefit ratio of government-sponsored research is difficult to estimate because the benefit may be diffuse and delayed, the investment in OCT over 2 decades has been recouped many times over in just a few years through better personalized therapy.
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http://dx.doi.org/10.1016/j.ajo.2017.09.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5732022PMC
January 2018

The ecosystem that powered the translation of OCT from fundamental research to clinical and commercial impact [Invited].

Biomed Opt Express 2017 Mar 21;8(3):1638-1664. Epub 2017 Feb 21.

Department of Electrical Engineering & Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA.

25 years is a relatively short period of time for a medical technology to become a standard of care impacting the treatment of millions of people every year. Yet 25 years ago there were no OCT companies, no OCT products, no OCT markets, and only one journal article published using the term OCT (optical coherence tomography). OCT has had a tremendous scientific, clinical, and economic impact on society. Today, it is estimated that there are ~30 Million OCT imaging procedures performed worldwide every year and the OCT system market is approaching $1B per year. OCT has helped diagnose patients with retinal disease at early treatable stages, preventing or greatly reducing irreversible vision loss. The technology has facilitated pharmaceutical development and contributed to fundamental understanding of disease mechanisms in multiple fields. The invention and translation of OCT from fundamental research to daily clinical practice would not have been possible without a complex ecosystem involving interaction among physics, engineering, and clinical medicine; government funding of fundamental and clinical research; collaborative and competitive research in the academic sector; entrepreneurship and industry; addressing real clinical needs; harnessing the innovation that occurs at the boundaries of disciplines; and economic and societal impact. This invited review paper discusses the translation of OCT from fundamental research to clinical practice and commercial impact, as well as describes the ecosystem that helped power OCT to where it is today and will continue to drive future advances. While OCT is an example of a technology that has had a powerful impact, there are many biomedical technologies which are poised for translation to clinical practice, and it is our hope that highlighting this ecosystem will help accelerate their translation and clinical impact.
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http://dx.doi.org/10.1364/BOE.8.001638DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480569PMC
March 2017

Massive gastric juvenile-type polyposis: a clinicopathological analysis of 22 cases.

Histopathology 2017 May 16;70(6):918-928. Epub 2017 Feb 16.

Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA, USA.

Aims: Massive gastric polyposis is a rare entity that is often associated with juvenile polyposis syndrome (JPS). The aim of this study was to evaluate the clinicopathological features of 22 patients with abundant gastric juvenile-type or hyperplastic-like polyps.

Methods And Results: The study included 12 males and 10 females with a median age of 48 years (range: 13-79 years). Fourteen (64%) patients carried a diagnosis of JPS, and three had prior gastrointestinal adenocarcinomas. Patients without known JPS presented at an older median age (60 years versus 40 years; P = 0.0068). Clinical symptoms included nausea, vomiting, and abdominal pain; 23% of patients were asymptomatic. Eighteen cases showed complete or near-complete carpeting of the gastric mucosa by innumerable polyps, ranging from a few millimetres to ~100 mm. Most polyps formed long, bulbous projections and had characteristic histological features, including a smooth outer contour, prominent stromal oedema, and widely spaced, often cystically dilated glands lined by foveolar epithelium; some polyps had less stroma and more hyperplastic foveolar epithelium. All had normal underlying or adjacent mucosa. Four (18%) cases harboured adenocarcinoma, and seven (32%) others showed dysplasia. SMAD4 immunohistochemical staining showed patchy loss in polyps from 19 of 20 cases tested. Five of six (84%) patients tested had a germline SMAD4 mutation.

Conclusions: Massive gastric juvenile-type polyposis can occur in patients with and without known JPS, and may mimic different conditions, such as other polyposis syndromes and Ménétrier disease. Pathologists play an important role in disease classification, as some patients lack a family or personal history of JPS, have few if any colonic polyps, and may not harbour diagnostic germline mutations.
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http://dx.doi.org/10.1111/his.13149DOI Listing
May 2017

Association of Histopathologic Phenotype of Periampullary Adenocarcinomas With Survival.

JAMA Surg 2017 01;152(1):82-88

Department of Surgery, David Geffen School of Medicine, University of California, Los Angeles6Department of Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles.

Importance: Patients with periampullary adenocarcinomas have widely variable survival. These cancers are traditionally categorized by their anatomic location of origin, namely, the duodenum, ampulla, distal common bile duct (CBD), or head of the pancreas. However, they can be alternatively subdivided histopathologically into intestinal or pancreaticobiliary (PB) types, which may more accurately estimate prognosis.

Objectives: To identify factors associated with survival in patients with periampullary adenocarcinomas and to compare survival between those having intestinal-type or PB-type cancers originating from the duodenum, ampulla, or distal CBD with those having pancreatic ductal adenocarcinoma (PDAC).

Design, Setting, And Participants: This study was a retrospective analysis of medical records in a prospectively maintained database. Three pathologists separately evaluated histopathologic phenotypes at a university-based tertiary referral center. Study participants were all patients (N = 510) who underwent pancreatoduodenectomy for adenocarcinoma between January 1995 and December 2014.

Main Outcome And Measure: Overall survival.

Results: This study identified 510 patients (mean [SD] age, 66.1 [10.9] years; 245 female [48%]) who underwent pancreatoduodenectomy for adenocarcinomas: 13 duodenal, 110 ampullary, 43 distal CBD, and 344 PDAC. The median overall survival was 61.2 (interquartile range [IQR], 22.0-111.0), 70.4 (IQR, 26.7-147.7), 40.6 (IQR, 15.2-59.6), and 31.4 (IQR, 17.3-86.3) months for patients with cancers of the duodenum, ampulla, distal CBD, or pancreas, respectively (P = .01), indicating a significant difference between the 4 tumor anatomic locations. Most duodenal (61.5% [8 of 13]) and ampullary (51.8% [57 of 110]) cancers were intestinal type, and most distal CBD tumors were PB type (86.0% [37 of 43]). Those with intestinal-type duodenal, ampullary, or distal CBD adenocarcinomas had longer median overall survival than those with PB type (71.7 vs 33.3 months, P = .02) or PDAC (31.4 months, P = .003). There was no survival difference between PB-type cancers and PDAC (33.3 vs 31.4 months, P = .66). On multivariable analysis, histologic grade (hazard ratio [HR], 1.98; 95% CI, 1.56-2.52; P < .001), histopathologic phenotype (HR, 1.75; 95% CI, 1.16-2.64; P = .008), and nodal status (HR, 1.45; 95% CI, 1.12-1.87; P = .05) were significantly associated with survival, while anatomic location was not.

Conclusions And Relevance: Histopathologic phenotype is a better prognosticator of survival in patients with periampullary adenocarcinomas than tumor anatomic location. Those with PB-type duodenal, ampullary, or distal CBD adenocarcinomas have survival similar to those with PDAC.
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http://dx.doi.org/10.1001/jamasurg.2016.3466DOI Listing
January 2017

Severe enterocolitis associated with antiepileptic-induced drug reaction with eosinophilia and systemic symptoms.

Hum Pathol 2014 Sep 15;45(9):1973-7. Epub 2014 May 15.

Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA 90095.

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a rare but serious drug-induced reaction with cutaneous, hematologic, and solid-organ injury. Antiepileptic drugs are one of the most common classes of drugs implicated in DRESS. A high morbidity and mortality may result, especially if the offending drug is not withdrawn promptly. Although DRESS may involve many organs, severe involvement of the gastrointestinal tract in DRESS and/or in association with antiepileptic drugs has rarely been reported. We report detailed clinical and histopathologic findings of a fatal case of DRESS syndrome resulting from antiepileptic drug treatment that was accompanied by severe enterocolitis, malabsorption, and cachexia.
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http://dx.doi.org/10.1016/j.humpath.2014.04.019DOI Listing
September 2014

Extracting and compensating dispersion mismatch in ultrahigh-resolution Fourier domain OCT imaging of the retina.

Opt Express 2012 Nov;20(23):25357-68

Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

We present a numerical approach to extract the dispersion mismatch in ultrahigh-resolution Fourier domain optical coherence tomography (OCT) imaging of the retina. The method draws upon an analogy with a Shack-Hartmann wavefront sensor. By exploiting mathematical similarities between the expressions for aberration in optical imaging and dispersion mismatch in spectral / Fourier domain OCT, Shack-Hartmann principles can be extended from the two-dimensional paraxial wavevector space (or the x-y plane in the spatial domain) to the one-dimensional wavenumber space (or the z-axis in the spatial domain). For OCT imaging of the retina, different retinal layers, such as the retinal nerve fiber layer (RNFL), the photoreceptor inner and outer segment junction (IS/OS), or all the retinal layers near the retinal pigment epithelium (RPE) can be used as point source beacons in the axial direction, analogous to point source beacons used in conventional two-dimensional Shack-Hartman wavefront sensors for aberration characterization. Subtleties regarding speckle phenomena in optical imaging, which affect the Shack-Hartmann wavefront sensor used in adaptive optics, also occur analogously in this application. Using this approach and carefully suppressing speckle, the dispersion mismatch in spectral / Fourier domain OCT retinal imaging can be successfully extracted numerically and used for numerical dispersion compensation to generate sharper, ultrahigh-resolution OCT images.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601734PMC
http://dx.doi.org/10.1364/OE.20.025357DOI Listing
November 2012

Mapping of deletion and translocation breakpoints in 1q44 implicates the serine/threonine kinase AKT3 in postnatal microcephaly and agenesis of the corpus callosum.

Am J Hum Genet 2007 Aug 13;81(2):292-303. Epub 2007 Jun 13.

Academic Unit of Medical Genetics and Regional Genetic Service, St. Mary's Hospital, and Centre for Molecular Medicine, The University of Manchester, M13 0JH, UK.

Deletions of chromosome 1q42-q44 have been reported in a variety of developmental abnormalities of the brain, including microcephaly (MIC) and agenesis of the corpus callosum (ACC). Here, we describe detailed mapping studies of patients with unbalanced structural rearrangements of distal 1q4. These define a 3.5-Mb critical region extending from RP11-80B9 to RP11-241M7 that we hypothesize contains one or more genes that lead to MIC and ACC when present in only one functional copy. Next, mapping of a balanced reciprocal t(1;13)(q44;q32) translocation in a patient with postnatal MIC and ACC demonstrated a breakpoint within this region that is situated 20 kb upstream of AKT3, a serine-threonine kinase. The murine orthologue Akt3 is required for the developmental regulation of normal brain size and callosal development. Whereas sequencing of AKT3 in a panel of 45 patients with ACC did not demonstrate any pathogenic variations, whole-mount in situ hybridization confirmed expression of Akt3 in the developing central nervous system during mouse embryogenesis. AKT3 represents an excellent candidate for developmental human MIC and ACC, and we suggest that haploinsufficiency causes both postnatal MIC and ACC.
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http://dx.doi.org/10.1086/519999DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1950798PMC
August 2007

Adeno-associated virus-mediated expression of thyroid hormone receptor isoforms-alpha1 and -beta1 improves contractile function in pressure overload-induced cardiac hypertrophy.

Endocrinology 2007 Jun 22;148(6):2870-7. Epub 2007 Feb 22.

Department of Medicine, 5063 Basic Sciences Building, University of California-San Diego, La Jolla, CA 92093-0618, USA.

Pressure overload-induced cardiac hypertrophy leads to decreased contractile performance, frequently progressing to heart failure. Cardiac hypertrophy and heart failure can be accompanied by the so-called sick thyroid syndrome, resulting in decreased serum T(3) levels along with decreased expression of thyroid hormone receptors (TRalpha1 and TRbeta1) and sarco(endo)plasmic reticulum Ca-ATPase (SERCA). Because the binding of T(3) occupied receptors to the thyroid response elements in the SERCA promotor can increase gene expression, we wanted to determine whether increasing TR expression in the hypertrophied heart could also improve SERCA expression and cardiac function. Mice subjected to aortic constriction to generate pressure overload-induced hypertrophy were also subjected to gene therapy using adeno-associated virus (AAV) expressing either TRalpha1 or TRbeta1, with LacZ expressing AAV serving as control. After 8 wk of aortic constriction, a similar degree of hypertrophy was observed in all three groups; however, mice treated with TRalpha1 or TRbeta1 showed improved contractile function. Administration of a physiological dose of T(3) increased serum T(3) levels only into the lower range of normal. This T(3) dose, with or without AAV TR treatment, did not result in any significant increase in contractile performance. Calcium transients measured in isolated myocytes also exhibited an enhanced rate of decay associated with TRalpha1 or TRbeta1 treatment. Western blot analysis showed increased SERCA expression in the TRalpha1- or TRbeta1-treated groups relative to the LacZ-treated control group. These results demonstrate that increasing TR expression in the hypertrophied heart is associated with an improvement in contractile function and increased SERCA expression.
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http://dx.doi.org/10.1210/en.2007-0009DOI Listing
June 2007

In vivo gene delivery of HSP70i by adenovirus and adeno-associated virus preserves contractile function in mouse heart following ischemia-reperfusion.

Am J Physiol Heart Circ Physiol 2006 Dec 18;291(6):H2905-10. Epub 2006 Aug 18.

Dept. of Medicine, University of California, San Diego, La Jolla, CA 92093-0618, USA.

Inducible heat shock protein 70 (HSP70i) has been shown to exert a protective effect in hearts subjected to ischemia-reperfusion. Although studied in heat-shocked animals and in transgenic mice that constitutively overexpress the protein, the therapeutic application of the protein in the form of a viral vector-mediated HSP70i expression has not been widely examined. Accordingly, we have examined the effects of HSP70i delivered in vivo to the left ventricular free wall of the heart via viral gene therapy in mice. The affect of virally mediated HSP70i expression in preserving cardiac function following ischemia-reperfusion was examined after short-term expression (5-day adenovirus mediated) and long-term expression (8-mo adeno-associated virus mediated) in mice by subjecting ex vivo Langendorff perfused hearts to a regime of ischemia-reperfusion. Both vectors were capable of increasing HSP70i expression in the heart, and neither vector had any effect on cardiac function during aerobic (preischemic) perfusion when compared with corresponding controls. In contrast, both adenovirus-mediated and adeno-associated virus-mediated expression of HSP70i improved the contractile recovery of the heart after 120 min of reperfusion following ischemia. This study demonstrates the feasibility of using both short- and long-term expression of virally mediated HSP70i as a therapeutic intervention against cardiac ischemia-reperfusion injury.
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http://dx.doi.org/10.1152/ajpheart.00323.2006DOI Listing
December 2006

Different configurations of specific thyroid hormone response elements mediate opposite effects of thyroid hormone and GC-1 on gene expression.

Endocrinology 2005 Nov 4;146(11):4926-33. Epub 2005 Aug 4.

Division of Endocrinology and Metabolism, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0618, USA.

T3 regulates transcription of the rat sarcoendoplasmic reticulum calcium ATPase in the heart. The T3 effect is mediated by three differently configured T3 response elements (TREs). Here we report the mutation of each individual TRE in the promoter and the contribution of each TRE on gene expression. Mutation of TRE1, a direct repeat element, exerted the strongest T3 response, compared with TRE2 and TRE3, which are inverted palindromes. The isolated TRE2 and TRE3, which showed no response (TRE2) or were weakly positive with T3 (TRE3), became strong negative regulatory elements with the T3 analog GC-1. We found that TRE1 recruits corepressor complexes containing nuclear receptor corepressor and histone deacetylase 3 in the absence of ligand, and steroid receptor coactivator-1-containing coactivator complexes with both T3 and GC-1. TRE3 bound the same corepressor complexes without ligand but showed only a weak association with steroid receptor coactivator-1 with T3 and a strong association with corepressor complexes with GC-1. Thus, GC-1 appears to control cofactor association differentially on these two sarcoendoplasmic reticulum calcium ATPase TREs, which could be the mechanism of ligand-dependent transcriptional activation and repression observed with the isolated TRE1 and TRE3 elements. Because the x-ray crystal structures of GC-1 and T3 complexed with the TR ligand binding domain are superimposable, the results imply that GC-1 and T3 induce differential effects on the receptor that are not evident in the static structures but must occur in the dynamic setting of receptor function. These results have implications for selective modulation of receptor function by agonist ligands.
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http://dx.doi.org/10.1210/en.2005-0631DOI Listing
November 2005

Decreased sarcoplasmic reticulum activity and contractility in diabetic db/db mouse heart.

Diabetes 2004 Dec;53(12):3201-8

Department of Medicine, University of California, San Diego, CA 92092-0618, USA.

Although it is known that insulin-dependent (type 1) diabetes results in depressed contractile performance associated with diminished sarcoendoplasmic reticular Ca2+-ATPase (SERCA2a) activity, findings in insulin-resistant (type 2) diabetes suggest a less clear association. The db/db insulin-resistant mouse model exhibits decreased cardiac performance both in situ and in isolated ex vivo working hearts. In this study, contractile performance and calcium transients were measured in Langendorff-perfused hearts and isolated cardiac myocytes. Diabetic (db/db) mouse hearts demonstrated decreased rates of contraction, relaxation, and pressure development. Calcium transients from isolated myocytes revealed significantly lower diastolic and systolic levels of calcium in diabetic hearts. Furthermore, the decay rate of the calcium transient was significantly reduced in diabetic myocytes, suggesting a diminished capacity for cytosolic calcium removal not associated with a change in sodium-calcium exchanger activity. Calcium leakage from the sarcoplasmic reticulum (SR) measured using tetracaine was significantly increased in diabetic myocytes. Western blot analysis indicated only a small decrease in SERCA2a expression in diabetic mice, but a large increase in phospholamban expression. Expression of the ryanodine receptor did not differ between groups. In conclusion, the decreased contractile function observed in the db/db diabetic mouse model appears to be related to decreased calcium handling by the SR.
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http://dx.doi.org/10.2337/diabetes.53.12.3201DOI Listing
December 2004

Cardiac expression and function of thyroid hormone receptor beta and its PV mutant.

Endocrinology 2003 Nov 7;144(11):4820-5. Epub 2003 Aug 7.

Division of Endocrinology and Metabolism, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0618, USA.

Thyroid hormone (T3) influences cardiac function, and mice with deletion of thyroid hormone receptor (TR)alpha have diminished cardiac function. TR alpha 1 represents 70% and TR beta 1 represents the remaining 30% of TR in ventricular myocytes, and its role in cardiac function is not well established. To determine the role of TR beta 1 in detail, we compared contractility in isolated perfused hearts from wild-type (WT) and TR beta knockout mice under normal and increased work load. TR beta knockout hearts showed contractile function similar to WT hearts at baseline and under conditions of enhanced demand. To gain insight into the role of TR beta, we used mice with a homozygous mutation in exon 10 of TR beta encoding the dominant negative PV mutant (TR beta PV) expressed from the endogenous TR beta promoter. TR beta PV mice treated with 6-propyl-2-thiouracil and supplemented with T3 to make them euthyroid have decreased contractility with negative and positive rates of relaxation and contraction as well as peak systolic pressure diminished by 35 +/- 5, 34 +/- 6, and 35 +/- 6% in comparison with WT mice. Heart rate is diminished by 36 +/- 7%, which is accompanied by decreased expression of the pacemaker-related gene hyperpolarization-activated cyclic nucleotide-gated 4 (HCN4). The expression of TR beta 1 in the pacemaker myocytes of the sinoatrial node was confirmed by quantitation of TR alpha 1 and TR beta 1 mRNA in sinoatrial node, which showed that TR beta 1 mRNA represents 27.5 +/- 1.6% of the ligand-binding isoforms of the TR. In summary, although TR beta is expressed at much lower levels in all regions of the heart than TR alpha 1, expression of the strong dominant negative TR beta PV mutant results in decreased contractile function and heart rate.
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http://dx.doi.org/10.1210/en.2003-0522DOI Listing
November 2003