A quantitative pixel-wise measurement of myocardial blood flow by contrast-enhanced first-pass CMR perfusion imaging: microsphere validation in dogs and feasibility study in humans

OBJECTIVES

The aim of this study was to evaluate fully quantitative myocardial blood flow (MBF) at a pixel level based on contrast-enhanced first-pass cardiac magnetic resonance (CMR) imaging in dogs and in patients.

BACKGROUND

Microspheres can quantify MBF in subgram regions of interest, but CMR perfusion imaging may be able to quantify MBF and differentiate blood flow at a much higher resolution.

METHODS

First-pass CMR perfusion imaging was performed in a dog model with local hyperemia induced by intracoronary adenosine. Fluorescent microspheres were the reference standard for MBF validation. CMR perfusion imaging was also performed on patients with significant coronary artery disease (CAD) by invasive coronary angiography. Myocardial time-signal intensity curves of the images were quantified on a pixel-by-pixel basis using a model-constrained deconvolution analysis.

RESULTS

Qualitatively, color CMR perfusion pixel maps were comparable to microsphere MBF bull's-eye plots in all animals. Pixel-wise CMR MBF estimates correlated well against subgram (0.49 ± 0.14 g) microsphere measurements (r = 0.87 to 0.90) but showed minor underestimation of MBF. To reduce bias due to misregistration and minimize issues related to repeated measures, 1 hyperemic and 1 remote sector per animal were compared with the microsphere MBF, which improved the correlation (r = 0.97 to 0.98), and the bias was close to zero. Sector-wise and pixel-wise CMR MBF estimates also correlated well (r = 0.97). In patients, color CMR stress perfusion pixel maps showed regional blood flow decreases and transmural perfusion gradients in territories served by stenotic coronary arteries. MBF estimates in endocardial versus epicardial subsectors, and ischemic versus remote sectors, were all significantly different (p < 0.001 and p < 0.01, respectively).

CONCLUSIONS

Myocardial blood flow can be quantified at the pixel level (∼32 μl of myocardium) on CMR perfusion images, and results compared well with microsphere measurements. High-resolution pixel-wise CMR perfusion maps can quantify transmural perfusion gradients in patients with CAD.

The accuracy of clinical findings and laparoscopy in pelvic inflammatory disease

The accuracy of clinical diagnosis for pelvic inflammatory disease was determined in 95 women who presented with pelvic pain to primary care physicians and then were referred to gynecologists. Laparoscopy or laparotomy with endometrial biopsy and fimbrial minibiopsy revealed that prevalence of pelvic inflammatory was 46% (44/95) and positive and negative predictive values of gynecologists were 74% (23/31) and 67% (43/64) (p = 0.0002). If histopathologic diagnosis was the standard, clinical accuracies of the gynecologists were no better than chance (p = 0.43), suggesting an expectation bias for visual diagnosis. Laparoscopy had a sensitivity of 50% (12/24) and a specificity of 80% (40/50) for salpingitis if the standard was fimbrial histopathologic diagnosis (p = 0.01). These results support the routine use of laparoscopy, supplemented when negative by endometrial and fimbrial minibiopsy, to accurately diagnose pelvic inflammatory disease.

Asian bull elephants: Flehmen-like responses to extractable components in female elephant estrous urine

Flehmen-like responses (urine tests) are one of the characteristic behavioral reactions of male Asian elephants (Elephants maximus) to cow elephants in estrus. Components of the urine of estrous cow elephants were extracted with organic solvents and partially purified by chromatography and shown to evoke Flehmen-like responses when they were presented to adult bulls.

Radiation dose and prognosis of ultra-low-dose stress-first myocardial perfusion SPECT in patients with chest pain using a high-efficiency camera

Although SPECT myocardial perfusion imaging (MPI) provides valuable information about patients with chest pain, there is growing concern regarding its radiation burden and lengthy duration. New high-efficiency (HE) cameras and stress-first protocols both offer the potential to markedly reduce radiation. No previous study has assessed outcomes and radiation doses of patients undergoing MPI on an HE-SPECT camera using an ultra-low-dose stress-first protocol.

METHODS

One hundred patients presenting to the emergency department with chest pain who were candidates for stress-first MPI underwent injection of approximately 185 MBq (5 mCi) of (99m)Tc-tetrofosmin at peak stress, followed by supine and prone imaging on an HE-SPECT camera. Same-day rest imaging was performed on patients with any abnormality on imaging after stress. Radiation effective dose was calculated from administered and residual activities. Patients were contacted 3 mo after discharge, and electronic records were accessed to evaluate the need for reevaluation for chest pain, additional imaging, or cardiac events.

RESULTS

Stress-only imaging was performed in 69 patients, for whom radiation effective dose averaged 0.99 mSv and study duration, 117 min. Radiation dose averaged 2.22 mSv over all patients. At 3 mo, 96 patients were free of major adverse cardiac events, repeat hospital chest pain evaluation, and repeat imaging or stress testing. One year after MPI and hospital discharge, all patients were living and without acute coronary syndrome.

CONCLUSION

HE-SPECT stress-only imaging can be performed in more than two thirds of chest pain patients without a high pretest probability of a stress perfusion defect, with excellent prognosis, a radiation dose averaging 1 mSv, and a test duration of less than 2 h.

Health related quality of life of patients with refractory angina before and one year after enrolment onto a refractory angina program

OBJECTIVE

This study was designed to assess the impact of a refractory angina programme on the health related quality of life for patients with chronic refractory angina (CRA) one year following enrolment.

DESIGN

A one year prospective audit.

SETTING

Specialist refractory angina clinic at a tertiary cardiac referral centre.

PATIENTS

69 consecutive refractory angina patients referred to a regional refractory angina centre from 1/03/2001 to 1/09/2002.

INTERVENTIONS

Pain treatment algorithm in accordance with the recommendations of the national refractory angina guideline committee.

MAIN OUTCOME MEASURES

Improvements in quality of life indices were assessed using Seattle angina questionnaire (SAQ), and short form-12 (SF-12) with changes in mood determined using the hospital anxiety and depression (HAD) questionnaire.

RESULTS

All dimensions of the SF-12 and SAQ were superior at one year with significant improvement seen with the mental component of SF-12 (p = 0.023), and four of the five SAQ domains, angina stability (p = 0.028), angina frequency (p=0.02), treatment satisfaction (p=0.001) and quality of life (p < 0.001). All the significant changes within the SAQ domains were large enough to be considered clinically relevant. At one year the anxiety and depression domains were significantly improved from baseline (p = 0.015, 0.018) with clinical anxiety levels falling significantly from 55% to 40%, a relative reduction of 28% (p = 0.008).

CONCLUSIONS

Implementation of the national refractory angina guidelines in a prospective study of 69 consecutive CRA patients significantly improved health related quality of life status at one year.

Ischemic Heart Disease: Noninvasive Imaging Techniques and Findings

Ischemic heart disease is a leading cause of death worldwide and comprises a large proportion of annual health care expenditure. Management of ischemic heart disease is now best guided by the physiologic significance of coronary artery stenosis. Invasive coronary angiography is the standard for diagnosing coronary artery stenosis. However, it is expensive and has risks including vascular access site complications and contrast material–induced nephropathy. Invasive coronary angiography requires fractional flow reserve (FFR) measurement to determine the physiologic significance of a coronary artery stenosis. Multiple noninvasive cardiac imaging modalities can also anatomically delineate or functionally assess for significant coronary artery stenosis, as well as detect the presence of myocardial infarction (MI). While coronary CT angiography can help assess the degree of anatomic stenosis, its inability to assess the physiologic significance of lesions limits its specificity. Physiologic significance of coronary artery stenosis can be determined by cardiac MR vasodilator or dobutamine stress imaging, CT stress perfusion imaging, FFR CT, PET myocardial perfusion imaging (MPI), SPECT MPI, and stress echocardiography. Clinically unrecognized MI, another clear indicator of physiologically significant coronary artery disease, is relatively common and is best evaluated with cardiac MRI. The authors illustrate the spectrum of imaging findings of ischemic heart disease (coronary artery disease, myocardial ischemia, and MI); highlight the advantages and disadvantages of the various noninvasive imaging methods used to assess ischemic heart disease, as illustrated by recent clinical trials; and summarize current indications and contraindications for noninvasive imaging techniques for detection of ischemic heart disease.

Online supplemental material is available for this article.

Published under a CC BY 4.0 license.

Screening urine with a leukocyte esterase strip and subsequent chlamydial testing of asymptomatic men attending primary care practitioners

BACKGROUND AND OBJECTIVES

The detection of asymptomatic urethritis using a leukocyte esterase (LE) strip may have a role in primary care screening to select men who need diagnostic testing for Chlamydia trachomatis and Neisseria gonorrhoeae.

STUDY DESIGN

Eight-hundred and eighty-two men, 16 to 35 years of age were studied when they attended their family physician or university health clinic for nongenitourinary complaints. First void urine (FVU) was tested by an LE strip (Chemstrip 2 LN, Boehringer Mannheim Corp., Indianapolis, IN), Chlamydiazyme (Abbott Laboratories, N. Chicago, IL) enzyme immunoassay with confirmatory blocking and polymerase chain reaction (PCR) with chlamydial plasmid primers.

RESULTS

Forty-five men (5.1%) were positive (> trace) by LE strip. Of the LE-positive urines, 9 (20.0%) were positive by EIA or PCR, and none of the LE-negatives were positive by EIA or PCR. Twenty-three LE positives (5 EIA/PCR-positive; 1 PCR-positive; 17 EIA/PCR-negative) were able to be followed with a second urine and 2 urethral swabs. All of the 6 chlamydia-positives who had follow-up tests were positive by both immunoassay and PCR on urine. Based on the FVU results, the prevalence of asymptomatic chlamydial infection was 1.0% (9/88) (95% CL, 0.5 to 1.9) for which the LE urine strip was 100% (9/9) sensitive and 95.9% (837/873) specific. Analyses based on screening 1,000 men, 16 to 25 years of age, showed that the cost per case detected was $192.00 using the LE strip (> 1+) to select urine specimens for EIA testing, compared to $1,326.00 using the EIA to test all urine specimens.

CONCLUSION

In this low prevalence, primary care setting, the LE urine strip was an accurate screening test, which if used to preselect urine specimens for subsequent chlamydial testing, would be less costly per case detected than assaying each specimen for chlamydia.

Direct detection of vanA and vanB genes in clinical specimens for rapid identification of vancomycin resistant enterococci (VRE) using multiplex PCR

Surveillance for vancomycin resistant enterococci (VRE) by culture can be labour intensive and time consuming. We have developed a multiplex polymerase chain reaction (MPCR) which can be performed directly on the clinical specimen. The assay allows sensitive detection of enterococci with vanA - and vanB -mediated resistance to vancomycin. DNA was purified from stool and rectal specimens using the XTRAX(TM)DNA Extraction Kit (Gull Labs). Multiplex PCR amplified vanA and vanB targets were detected using a microtiter plate EIA. Two-hundred specimens were tested by routine culture and MPCR. Culture identified 44 VRE isolates and MPCR detected 38 of the 44 culture positives. Multiplex PCR detected three additional positive VRE specimens missed by culture for a sensitivity and specificity of 86.4 and 98.1%, respectively. When the presence of PCR inhibitors was addressed in the six culture positive/MPCR negative specimens, four additional VRE positive specimens were detected. Performing MPCR on the original specimens and on a 1:10 dilution of all specimens to minimize the effect of inhibitors gave a sensitivity and specificity of 95.5 and 98.1%, respectively. Multiplex PCR with confirmation by microtiter plate hybridization could be completed in 8 h compared with 24-48 h required for culture.

Effect of bismuth breast shielding on radiation dose and image quality in coronary CT angiography

BACKGROUND

Coronary computed tomographic angiography (CCTA) is associated with high radiation dose to the female breasts. Bismuth breast shielding offers the potential to significantly reduce dose to the breasts and nearby organs, but the magnitude of this reduction and its impact on image quality and radiation dose have not been evaluated.

METHODS

Radiation doses from CCTA to critical organs were determined using metal-oxide-semiconductor field-effect transistors positioned in a customized anthropomorphic whole-body dosimetry verification phantom. Image noise and signal were measured in regions of interest (ROIs) including the coronary arteries.

RESULTS

With bismuth shielding, breast radiation dose was reduced 46%-57% depending on breast size and scanning technique, with more moderate dose reduction to the heart, lungs, and esophagus. However, shielding significantly decreased image signal (by 14.6 HU) and contrast (by 28.4 HU), modestly but significantly increased image noise in ROIs in locations of coronary arteries, and decreased contrast-to-noise ratio by 20.9%.

CONCLUSIONS

While bismuth breast shielding can significantly decrease radiation dose to critical organs, it is associated with an increase in image noise, decrease in contrast-to-noise, and changes tissue attenuation characteristics in the location of the coronary arteries.

Feasibility of low radiation dose retrospectively-gated cardiac CT for functional analysis in adult congenital heart disease

Background:

The use of cardiac computed tomography (CT) in the evaluation of adult congenital heart disease patients is limited due to concerns of high radiation doses. The purpose of this study was to prospectively assess whether low radiation dose cardiac CT is feasible to evaluate ventricular systolic function in adults with congenital heart disease.

Methods:

The study group included 30 consecutive patients with significant congenital heart disease who underwent a total of 35 ECG-gated cardiac CT scans utilizing a 320-detector row CT scanner. Each study included a non-contrast scan and subsequent contrast-enhanced retrospectively-gated acquisition. Effective radiation dose was estimated by multiplying the dose length product by a k-factor of 0.014 mSv/mGy cm.

Results:

The mean age of the patients was 34.4 ± 8.9 years, 60% were men, and mean body mass index was 24.2 ± 4.3 kg/m². A majority of patients (n = 28, 93.3%) had contraindications to cardiac MRI. A tube potential of 80 kV was used in 27 (77.1%) of the contrast-enhanced scans. The mean signal-to-noise and contrast-to-noise ratios were 11.5 ± 3.9 and 10.3 ± 3.7, respectively. The median radiation dose for non-contrast and contrast-enhanced images were 0.1 mSv (0.07–0.2 mSv) and 0.94 mSv (0.5–2.1 mSv), respectively. All 35 CT scans were successfully analyzed for ventricular systolic function.

Conclusions:

A low radiation contrast-enhanced, retrospectively-gated cardiac CT with a median radiation dose of less than 1 mSv was successful in evaluating ventricular systolic function in 30 consecutive adult congenital heart disease patients who underwent a total of 35 scans.

Gas-liquid chromatographic analysis of cellular fatty acids for identification of gram-negative anaerobic bacilli

A commercially available, computer-assisted microbial identification system (MIS) employs gas-liquid chromatographic analysis of cellular fatty acids for bacterial identification. MIS was compared with conventional identification systems. Of 225 gram-negative anaerobes tested, MIS identified 72.4% of the strains to the species level, 88.9% to the appropriate group, and 93.3% to the correct genus.

Guidelines for the Evaluation of Prosthetic Valve Function With Cardiovascular Imaging: A Report From the American Society of Echocardiography Developed in Collaboration With the Society for Cardiovascular Magnetic Resonance and the Society of Cardiovascular Computed Tomography

In patients with significant cardiac valvular disease, intervention with either valve repair or valve replacement may be inevitable. Although valve repair is frequently performed, especially for mitral and tricuspid regurgitation, valve replacement remains common, particularly in adults. Diagnostic methods are often needed to assess the function of the prosthesis. Echocardiography is the first-line method for noninvasive evaluation of prosthetic valve function. The transthoracic approach is complemented with two-dimensional and three-dimensional transesophageal echocardiography for further refinement of valve morphology and function when needed. More recently, advances in computed tomography and cardiac magnetic resonance have enhanced their roles in evaluating valvular heart disease. This document offers a review of the echocardiographic techniques used and provides recommendations and general guidelines for evaluation of prosthetic valve function on the basis of the scientific literature and consensus of a panel of experts. This guideline discusses the role of advanced imaging with transesophageal echocardiography, cardiac computed tomography, and cardiac magnetic resonance in evaluating prosthetic valve structure, function, and regurgitation. It replaces the 2009 American Society of Echocardiography guideline on prosthetic valves and complements the 2019 guideline on the evaluation of valvular regurgitation after percutaneous valve repair or replacement.

Comparison of Frequency and Duration of Periodontal Disease With Progression of Coronary Artery Calcium in Patients With and Without Type 1 Diabetes Mellitus

People with type 1 diabetes mellitus manifest a greater burden of both periodontal disease and coronary artery disease (CAD); however, little is known about their interrelation. Coronary artery calcium (CAC) measures subclinical atherosclerosis and predicts major adverse coronary events. The relation between periodontal disease and CAC progression in individuals with type 1 diabetes has not been previously described. We determined the prevalence and progression of CAC in relation to self-reported periodontal disease. Multivariate logistic and tobit regression models were used to examine the relation between periodontal disease duration and CAC progression and whether this relation differs by diabetes status after controlling for age, gender, total and high-density lipoprotein cholesterol, hypertension, smoking, body mass index (BMI), duration of diabetes, and baseline CAC. A total of 473 patients with type 1 diabetes and 548 without diabetes were followed for a mean of 6.1 years. At baseline, the prevalence and duration of periodontal disease did not differ between subjects with and without diabetes (14.5% vs 13.4%, p = 0.60; 6 vs 9 years, p = 0.18). Duration of periodontal disease was not significantly associated with baseline CAC prevalence. In patients with type 1 diabetes, periodontal disease duration was significantly related to CAC progression (p = 0.004) but not in subjects without diabetes (p = 0.63). In conclusion, this study suggests that periodontal disease is an independent predictor of long-term progression of CAC in patients with type 1 diabetes.

A novel method for evaluating regional RV function in the adult congenital heart with low-dose CT and SQUEEZ processing

BACKGROUND

Measuring local RV function in adult congenital heart disease (ACHD) with echocardiography or MRI is challenging because of the complex geometry and existing pacing devices. Visual assessment of ventricular function via low-dose cardiac CT has been recently performed. This pilot study assessed whether low-dose 4D cine CT combined with automatic measurement of regional shortening could quantify right-ventricular function in ACHD patients.

METHODS

Seven patients with Tetralogy of Fallot either contraindicated for MRI or assessed for coronary artery disease and seven non-congenital patients were imaged with ECG-gated cardiac CT utilizing a 320-detector row scanner. Right ventricular global function and regional shortening were quantified.

RESULTS

Non-congenital patients were imaged with 2.9±2.1mSv and 395±359 HU blood-myocardium contrast. The ACHD patients were imaged with 2.1±1.3mSv and 726±296 HU contrast. Right ventricles of the ACHD patients had higher end-diastolic volume (297±107mL vs 123±34mL, p=0.001), lower ejection fraction (32.0±4.9% vs 45.0±6.0%, p=0.001), and higher dyskinetic fraction (10.9±3.7% vs 2.6±2.8%, p<0.001) relative to the non-congenital controls.

CONCLUSIONS

In this initial pilot study, right ventricular global and regional systolic function were measured using low-dose cine CT with SQUEEZ quantification in non-congenital patients as well as ACHD patients with Tetralogy of Fallot. Unique regional features of RV dyskinesia were identified in the ACHD patients which could yield a more precise quantification of RV function.

Laser techniques for the evaluation of wear in Class II restorations

A technique for the quantitative determination of the changes in surface topography of restorations during wear has been developed. This involves the optical contouring of the surface using a laser, and the generation of contour maps. Several different methods for interpreting these maps are discussed. A computer-aided method is the most consistently accurate and measures wear volume to an accuracy of 2--5%.

Coronary artery bypass graft imaging using ECG-gated multislice computed tomography: Comparison with catheter angiography

AIM

To compare the value of multislice computerized tomography (MSCT) in imaging coronary artery bypass grafts (CABGs) by direct quantitative comparison with standard invasive angiography.

METHODS

Using MSCT, 50 consecutive patients who had previously undergone CABG surgery and had recently undergone invasive angiography for recurrent angina pectoris, were studied further using MSCT after intravenous injection of non-ionic contrast agent; cardiac imaging was performed during a single breath-hold. Graft anatomy was quantified, using both quantitative coronary angiography (QCA) and MSCT, by different investigators blinded to each other. Reproducibility was quantified using the standard error of the measurement expressed as a percentage in log-transformed values (CV%) and intraclass correlation (ICC).

RESULTS

All 150 grafts were imaged using MSCT; only 4 patent grafts were not imaged using selective angiography. Good agreement was achieved between MSCT and QCA on assessment of proximal anastomoses (CV% 25.2, ICC 0.84), mid-vessel luminal diameter (CV% 15.5, ICC 0.91) and aneurysmal dilations (CV% 14.3). Reasonable agreement was reached on assessment of distal anastomoses (CV% 26.7, ICC 0.66) and categorization of distal run-off (ICC 0.73). Good agreement was observed for stenoses of over 50% luminal loss (CV% 8.7, ICC 0.97) but agreement on assessment of less severe lesions was poor (CV% 208.7, ICC 0.51).

CONCLUSION

This study demonstrates that CABGs can be quantitatively evaluated using MSCT, and that significant lesions present in all CABG segments can be reliably identified. Agreement between MSCT and QCA for lesions of less than 50% luminal loss was poor.

Effect of routine use of a multiplex PCR for detection of vanA- and vanB- mediated enterococcal resistance on accuracy, costs and earlier reporting

A multiplex PCR (MPCR) for detection of vanA-and vanB-mediated resistance to vancomycin was optimized and adapted for use in the routine microbiology laboratory. Consecutive specimens (1196) submitted for vancomycin resistant Enterococci (VRE) surveillance were processed by clinical technologists on Bile Esculin Azide Agar containing 6 mg/L vancomycin (BEAA/Vanco6) plates and 466 showing black colony growth were processed by conventional biochemical testing (CBT) and by MPCR. CBT identified 208 VRE positives. MPCR detected 205 of the CBT- positives plus an additional 10. Analysis of the discordant specimens determined that 5 CBT- negative/MPCR-positive specimens also contained Enterococci with vanC resistance, 3 CBT-positive/MPCR-negative specimens were true positives, and 5 CBT-negative/MPCR-positive specimens occurred due to technical error. The sensitivity and specificity of MPCR were 98.4% and 96.1%. MPCR identifications of VRE were achieved approximately 48 h earlier than CBT and at 60% of the costs.

Accuracy and reproducibility of the MicroScan rapid anaerobe identification system with an automated reader

Rapid anaerobe identification (MicroScan) panels (4 h) were evaluated both visually and by the AutoScan-4, a computer-controlled microplate reader. The results of both reading methods were compared with identifications obtained by the conventional (Virginia Polytechnic Institute) method. In total, 237 anaerobes were tested. Correct identifications were obtained for 166 strains (70%) by visual reading and 157 strains (66.2%) by the AutoScan-4. Supplementary tests resulted in 80.1 and 76.7% total correct identifications, respectively. Comparison of the two reading methods revealed complete agreement for 169 strains. Differences between the two reading methods were due to difficulties in reading specific reactions. This was especially true with the clostridial species. The performance of the MicroScan system in the identification of anaerobic bacteria appears comparable to that of other 4-h identification systems for anaerobes, but this system shows significant variance from the conventional system. Improvements in the trays and data base are required before the system can be recommended for routine use.

Comparison of RapID-ANA and Minitek with a conventional method for biochemical identification of anaerobes

Two micromethods for the identification of anaerobes, one requiring growth (Minitek) and one nongrowth dependent (RapID-ANA), were compared with a conventional identification culture system. For 222 clinical isolates, RapID-ANA agreed with PRAS in 187 (84%) and Minitek agreed for only 170 strains (76%). Both systems identified common isolates well, but encountered some difficulty in identifying less common clostridia and Gram-negative bacilli. Although adequate for most strains, the results from both systems should be interpreted with caution, particularly for less frequently isolated species.

Acute ascorbic acid infusion increases left ventricular diastolic function in postmenopausal women

OBJECTIVES

We tested the hypothesis that oxidative stress contributes to reductions in left ventricular diastolic (LV) function in estrogen-deficient postmenopausal women, related in part to reduced nitric oxide (NO) bioavailability.

STUDY DESIGN

LV diastolic function - recorded using transthoracic echocardiography and determined as the peak early (E) to late (A) mitral inflow velocity ratio and the E to peak early (e') mitral annular velocity ratio - and brachial artery flow mediated dilation (FMD), a biomarker of NO bioavailability, were measured during acute systemic infusions of saline (control) and ascorbic acid (experimental model to decrease oxidative stress) in healthy premenopausal women (N=14, 18-40 years) and postmenopausal women (N=23, 45-75 years).

RESULTS

The E/A ratio was lower (1.16[1.06-1.33] vs 1.65[1.5-2.3]; median[interquartile range]) and the E/e' ratio was elevated (8.8[7.6-9.9] vs. 6.6[5.5-7.3]) in postmenopausal compared with premenopausal women, indicating reduced LV diastolic function. E/A and E/e' were correlated with FMD (r=0.54 and r=-0.59, respectively, both P<0.01). Ascorbic acid infusion improved both FMD (5.4±2.0% to 7.8±2.6%) and E/e' (to 8.1[7.2-9.7], P=0.01) in postmenopausal women but not in premenopausal women. Ascorbic acid did not change E/A in either group.

CONCLUSION

The current study provides evidence that oxidative stress contributes to reduced LV diastolic function in estrogen-deficient postmenopausal women, possibly by reducing the availability of NO.

Microtubule Severing Enzymes Oligomerization and Allostery: A Tale of Two Domains

Severing proteins are nanomachines from the AAA+ (ATPases associated with various cellular activities) superfamily whose function is to remodel the largest cellular filaments, microtubules. The standard AAA+ machines adopt hexameric ring structures for functional reasons, while being primarily monomeric in the absence of the nucleotide. Both major severing proteins, katanin and spastin, are believed to follow this trend. However, studies proposed that they populate lower-order oligomers in the presence of cofactors, which are functionally relevant. Our simulations show that the preferred oligomeric assembly is dependent on the binding partners and on the type of severing protein. Essential dynamics analysis predicts that the stability of an oligomer is dependent on the strength of the interface between the helical bundle domain (HBD) of a monomer and the convex face of the nucleotide binding domain (NBD) of a neighboring monomer. Hot spots analysis found that the region consisting of the HBD tip and the C-terminal (CT) helix is the only common element between the allosteric networks responding to nucleotide, substrate, and intermonomer binding. Clustering analysis indicates the existence of multiple pathways for the transition between the secondary structure of the HBD tip in monomers and the structure(s) it adopts in oligomers.