Quantitative assessment of magnetic resonance derived myocardial perfusion measurements using advanced techniques: microsphere validation in an explanted pig heart system

Background

Cardiovascular Magnetic Resonance (CMR) myocardial perfusion imaging has the potential to evolve into a method allowing full quantification of myocardial blood flow (MBF) in clinical routine. Multiple quantification pathways have been proposed. However at present it remains unclear which algorithm is the most accurate. An isolated perfused, magnetic resonance (MR) compatible pig heart model allows very accurate titration of MBF and in combination with high-resolution assessment of fluorescently-labeled microspheres represents a near optimal platform for validation. We sought to investigate which algorithm is most suited to quantify myocardial perfusion by CMR at 1.5 and 3 Tesla using state of the art CMR perfusion techniques and quantification algorithms.

Methods

First-pass perfusion CMR was performed in an MR compatible blood perfused pig heart model. We acquired perfusion images at physiological flow (“rest”), reduced flow (“ischaemia”) and during adenosine-induced hyperaemia (“hyperaemia”) as well as during coronary occlusion. Perfusion CMR was performed at 1.5 Tesla (n = 4 animals) and at 3 Tesla (n = 4 animals). Fluorescently-labeled microspheres and externally controlled coronary blood flow served as reference standards for comparison of different quantification strategies, namely Fermi function deconvolution (Fermi), autoregressive moving average modelling (ARMA), exponential basis deconvolution (Exponential) and B-spline basis deconvolution (B-spline).

Results

All CMR derived MBF estimates significantly correlated with microsphere results. The best correlation was achieved with Fermi function deconvolution both at 1.5 Tesla (r = 0.93, p < 0.001) and at 3 Tesla (r = 0.9, p < 0.001). Fermi correlated significantly better with the microspheres than all other methods at 3 Tesla (p < 0.002). B-spline performed worse than Fermi and Exponential at 1.5 Tesla and showed the weakest correlation to microspheres (r = 0.74, p < 0.001). All other comparisons were not significant. At 3 Tesla exponential deconvolution performed worst (r = 0.49, p < 0.001).

Conclusions

CMR derived quantitative blood flow estimates correlate with true myocardial blood flow in a controlled animal model. Amongst the different techniques, Fermi function deconvolution was the most accurate technique at both field strengths. Perfusion CMR based on Fermi function deconvolution may therefore emerge as a useful clinical tool providing accurate quantitative blood flow assessment.     

Identification of mycobacteria and other acid fast organisms associated with pulmonary disease

ObjectiveTo identify Mycobacterium tuberculosis (M. tuberculosis) and other acid fast organisms isolated from sputum of HIV positive adult patients with pulmonary disease in Jos, Nigeria.MethodsAcid fast organisms isolated from 80 acid fast bacilli (AFB) positive sputa of HIV positive adult patients suspected for tuberculosis in Jos, Nigeria were identified for members of M. tuberculosis complex (M. tuberculosis, Mycobacterium bovis, Mycobacterium africanum, Mycobacterium canetti, Mycobacterium microti and Mycobacterium caprae) by use of spoligootyping, Multiplex Gen Probe, Hain genotype assay and gene sequencing for spoligotype negative isolates.ResultsSeven different spoligotypes of M. tuberculosis complex were identified from 70/80 (87.5%) total number of isolates. Mycobacterium kansasii (1), Mycobacterium dulvalii (1) Nocardia species (1) and Tsukamurella species (2) were detected from 5/10 spoligotype negative isolates.ConclusionsAlthough M. tuberculosis is the dominant AFB associated with chronic pulmonary disease in Jos, Nigeria, other clinically relevant mycobacteria were also observed in the study. This suggests that other AFB positive microorganisms associated with tuberculosis-like symptoms might be misdiagnosed and incorrectly treated as M. tuberculosis. It is therefore necessary for laboratories in tuberculosis high burden countries to step up diagnostic procedures beyond routine smear microscopy.     

Human T-lymphotropic virus (HTLV) types I and II infection in sexual contacts and family members of blood donors who are seropositive for HTLV type I or II. American Red Cross HTLV-I/II Collaborative Study Group

Interviews and laboratory testing were conducted for 168 contacts referred by former blood donors identified as seropositive for antibody to human T-lymphotropic virus type I (HTLV-I) or type II (HTLV-II). Thirty-two (28%) of 114 heterosexual contacts of seropositive donors, including 12 women and 20 men, were found to be antibody positive. None of 40 offspring (except one adult man who reported sexual contact in Puerto Rico) or 14 other (nonspousal) family members were seropositive. Thirty-one of the seropositive contacts were typeable as having either HTLV-I (52%) or HTLV-II (48%). Assessment of couples found that the median duration of the sexual relationship was significantly longer (p = 0.03) for those in which both partners were infected than in discordant pairs. Analysis of risk history data for 22 infected couples revealed that, in three cases, risk factors (Japanese ancestry or sexual contact with an injecting drug user) could be identified in the women, but not in their male partners. Among couples in which the male had the greater risk history, the risk factor was either a history of transfusion, birth or sexual exposure in an endemic area, or injected drug use. Counseling strategies for individuals with HTLV-I or HTLV-II infection should take into account the relatively high seroprevalence in their partners and should address the potential for sexual transmission in both directions.     

Anesthesia systems. Part II: Operating principles of fundamental components

This second article in a 2-part series on the operation of principal components within Narkomed anesthesia systems describes the function and compensation mechanisms of the Dräger 19.n vaporizer, the operating principles of the anesthesia ventilator-electronic, the structure and mechanics of the pressure limit control, and the 3 basic monitoring systems built into the anesthesia system. Part II of this series builds on the data published in part I (J Clin Monit 1992;8:295–307).     

Rh E/e genotyping by allele-specific primer amplification

It has been shown that the Rhesus (Rh) blood group antigens are encoded by two homologous genes: the Rh D gene and the Rh CcEe gene. The Rh CcEe gene encodes different peptides: the Rh C, c, E, and e polypeptides. Only one nucleotide difference has been found between the alleles encoding the Rh E and the Rh e antigen polypeptides. It is a C-- >G transition at nucleotide position 676, which leads to an amino acid substitution from proline to alanine in the Rh e-carrying polypeptide. Here we present an allele-specific primer amplification (ASPA) method to determine the Rh E and Rh e genotypes. In one polymerase chain reaction, the sense primer had a 3'-end nucleotide specific for the cytosine at position 676 of the Rh E allele. In another reaction, a sense primer was used with a 3'-end nucleotide specific for the guanine at position 676 of the Rh e allele and the Rh D gene, whereas the antisense primer had a 3'-end nucleotide specific for the adenine at position 787 of the Rh CcEe gene. We tested DNA samples from 158 normal donors (including non-Caucasian donors and donors with rare Rh phenotypes) in these assays. There was full concordance with the results of serologic Rh E/e phenotyping. Thus, we may conclude that the ASPA approach leads to a simple and reliable method to determine the Rh E/e genotype. This can be useful in Rh E/e genotyping of fetuses and/or in cases in which no red blood cells are available for serotyping. Moreover, our results confirm the proposed association between the cytosine/guanine polymorphism at position 676 and the Rh E/e phenotype.     

Analysis of hematopoietic stem and progenitor cell populations in cytomegalovirus-infected mice

We have studied the effects of murine cytomegalovirus (MCMV) infection on bone marrow stem and progenitor cell populations to find an explanation for the defects in hematopoiesis that accompany CMV infections in patients. Sublethal MCMV infection of BALB/c mice resulted in a 5- to 10-fold decrease in the numbers of myeloid (colony- forming unit-granulocyte-macrophage [CFU-GM]) and erythroid (burst- forming unit-erythroid [BFU-E]) progenitor cells in the marrow, but not in primitive myeloerythroid progenitor cell (colony-forming unit-spleen [CFU-S]) numbers. In contrast, we observed a 10- to 20-fold reduction in CFU-S as well as CFU-GM and BFU-E in lethally infected mice. Depletion of marrow CFU-GM was less severe in C57BL/10 and C3H/HeJ mice, which are more resistant to the effects of MCMV infection. Treatment of bone marrow cells with MCMV preparations in vitro did not reduce the numbers of CFU-GM, although up to 10% of the cells were productively infected. This finding suggests that CFU-GM were not susceptible to lytic MCMV infection in vitro and are probably not eliminated by lytic infection in vivo. Increases in the frequencies of Sca-1+Lin- marrow cells, a population that includes cells with the characteristics of pluripotential stem cells, were observed in MCMV- infected BALB/c, C57BL/10, and DBA/2J mice. Increases in the frequencies of c-kit+Lin- marrow cells were only seen in DBA/2J mice. MCMV infection did not impair the function of pluripotential stem cells because transplantation of marrow from MCMV-infected donors into irradiated recipient mice resulted in successful reconstitution of the T, B, and myeloid cell lineages.     

Comparison of 3‐Year Clinical Outcomes Between Resolute™ Zotarolimus‐ and Sirolimus‐Eluting Stents for Long Coronary Artery Stenosis

Objectives

Long‐term clinical outcomes were evaluated in long coronary artery stenosis treated with different types of drug‐eluting stents.

Background

Long‐term follow‐up data to compare clinical outcomes between Resolute? zotarolimus‐eluting stent (R‐ZES) versus sirolimus‐eluting stent (SES) implantation for long coronary artery stenosis is insufficient.

Methods

A total of 254 patients (307 lesions) treated with R‐ZES and 265 patients (303 lesions) treated with SES for long coronary lesions (total stent length ≥30 mm) were enrolled, and long‐term (3 years) clinical outcomes were compared between the 2 groups. Efficacy (target lesion revascularization [TLR]) and safety (the composite occurrence of cardiovascular death, target lesion–related myocardial infarction, or target lesion–related definite stent thrombosis) were assessed.

Results

The 2 groups had similar baseline characteristics except for the duration of dual antiplatelet therapy (23.4 ± 11.2 months in R‐ZES‐treated patients vs. 27.4 ± 13.9 months in SES‐treated patients, P < 0.001). Total stent length was similar in R‐ZES‐treated patients (45.0 ± 19.0 mm) and SES‐treated patients (45.4 ± 18.6 mm) (P = 0.464). The cumulative TLR rate was 4.6% in R‐ZES‐treated patients versus 4.6% in SES‐treated patients (P = 0.911). For safety parameters, R‐ZES‐treated patients showed a significantly lower rate of the composite occurrence of cardiovascular death, target lesion–related myocardial infarction, or target lesion–related definite stent thrombosis than SES‐treated patients (0.4% vs. 2.4%, P = 0.042). Particularly, the occurrence of target lesion–related definite stent thrombosis was significantly lower in R‐ZES‐treated patients than in SES‐treated patients (0.0% vs. 2.0%, P = 0.028).

Conclusions

R‐ZES stents showed superior long‐term safety than SES for treating long coronary lesions, while maintaining a similar clinical efficacy.

     

Alpha 4 beta 1 and alpha 5 beta 1 are differentially expressed during myelopoiesis and mediate the adherence of human CD34+ cells to fibronectin in an activation-dependent way

To study the receptors involved in the interaction between extracellular matrix proteins and hematopoietic progenitor cells, we analyzed the expression of beta 1 integrins on CD34+ bone marrow cells by means of immunoflowcytometry. Alpha 4 beta 1 and alpha 5 beta 1 were expressed, whereas alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 1, and alpha v beta 1 were virtually absent. Furthermore, we assessed the alpha 4 and alpha 5 expression on committed myeloid progenitor cells. These colony-forming cells were detected in the alpha 4 dull fraction and the alpha 5 dull fraction. During myeloid differentiation, both in vivo and in vitro, a differential expression of alpha 4 beta 1 and alpha 5 beta 1 was observed. alpha 5 beta 1 was found to be lost at the myelocytic-metamyelocytic stage, before the loss of alpha 4 beta 1, at the band stage. Functional studies showed no binding of erythroid progenitor-depleted, CD34+ bone marrow cells to fibronectin. However, protein kinase C activation strongly induced fibronectin binding (68% of the cells). Inhibition experiments with specific antibodies and peptides showed the binding to be mediated by both alpha 4 beta 1 and alpha 5 beta 1. Also, colony-forming cells of granulocytes and macrophages were demonstrated to adhere to fibronectin in an activation-dependent way. During granulocyte colony-stimulating factor-induced in vitro maturation, the activation-dependent fibronectin binding capacity is gradually lost. We conclude that: (1) CD34+ bone marrow cells express alpha 4 beta 1 and alpha 5 beta 1; (2) the expression of alpha 4 beta 1 and alpha 5 beta 1 is differentially expressed during myeloid differentiation; and (3) binding of CD34+ bone marrow cells to fibronectin is activation dependent.     

Fragility and structure of hemoglobin S fibers and gels and their consequences for gelation kinetics and rheology

Pathogenesis in sickle cell disease depends on whether red blood cells can pass the microvasculature during the delay time before hemoglobin S gelation and cell rigidification occur. Here we observe individual hemoglobin S fibers by differential interference contrast (DIC) microscopy and show that hemoglobin S gels and fibers are fragile and easily broken by mechanical perturbation, and that breakage results in vast acceleration of gelation kinetics due to the creation of new, growing fiber-ends. Hence, in vivo this may be an important factor, in addition to hemoglobin concentration and degree of deoxygenation, that governs delay time and pathogenesis. Pathogenesis also depends on gel rheology and cell rigidification, which depend on fiber cross-linking. We show different mechanisms by which X-shaped, Y-shaped, and "zippering" cross-links form. Finally, we estimate the "on" rate constant for fiber growth to be about 200 mmol/(L.s) and obtain a value for the heterogeneous nucleation rate at 13.5 mmol/L heme.     

Abnormal neutrophil phenotype and neutrophil FcRIII deficiency corrected by bone marrow transplantation

BACKGROUND : Neutrophils from a patient in first remission of acute myeloid leukemia were found to lack NA1 and NA2 alloantigens. This NA null phenotype was converted to the normal phenotype of NA1, NB2 by the transplantation of bone marrow from an HLA-identical sibling. To investigate the inherited or acquired nature of this rare phenotype, a combination of conventional neutrophil serology and recently developed restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR) assays was used. STUDY DESIGN AND METHODS : Diagnosis, remission, and posttransplant patient peripheral blood samples were used for neutrophil phenotyping by granulocyte agglutination and immunofluorescence tests. The presence and dose of the gene for neutrophil Fc gamma RIIIb (Fc gamma RIIIB) were tested for with RFLP and Southern analysis and PCR-based RFLP tests. Plasma levels of circulating soluble Fc gamma RIII (sFc gamma RIII) were measured with radioimmunoassay. The sibling bone marrow donor and the patient's parents were also studied. RESULTS : RFLP analysis of DNA obtained from the patient at the time of diagnosis showed that she lacked the Fc gamma RIIIB gene for neutrophil Fc gamma RIII (i.e., Fc gamma RIIIb), but that, in DNA prepared from posttransplant samples, the Fc gamma RIIIB gene was present. Quantitation of plasma levels of soluble FcRIII (sFcRIII) demonstrated a complete absence of sFcRIII in the patient's pretransplant plasma. However, 20 units of sFcRIII were detected in the patient's plasma by 160 days after graft. Hair samples from the patient provided sufficient nonhematopoietic, genomic DNA to confirm that her genotype was NA0NA0. DNA prepared from lymphocytes of both parents and the sibling marrow donor was used to quantitate their Fc gamma RIIIB gene dose. The mother and brother had only one Fc gamma RIIIB gene each, while the father apparently had a normal complement of two Fc gamma RIIIB genes. CONCLUSION : In this case, an inherited absence of Fc gamma RIIIB gene in a patient with acute myeloid leukemia was unintentionally corrected by the transplantation of bone marrow from a sibling donor who himself carried only one Fc gamma RIIIB gene.