Effects of weight loss on myocardial energetics and diastolic function in obesity

A reduced myocardial phosphocreatine/adenosine triphosphate (PCr/ATP) ratio is linked to both diastolic dysfunction and heart failure. Although obesity is well known to cause diastolic dysfunction a link to impaired cardiac energetics has only recently been established. We assessed whether or not long-term weight loss in obesity, which is known to reduce mortality, is accompanied by both improved cardiac energetics and diastolic function. Normal weight (BMI 22 ± 2; n = 18) and obese subjects (BMI 34 ± 4; n = 13) underwent cine-MRI (1.5 Tesla) to determine left ventricular diastolic function using volume-time curve analysis, and (31)P-MR spectroscopy (3 Tesla) to assess cardiac energetics (PCr/ATP ratio). Obese subjects (n = 13) underwent repeat assessment after 1 year of supervised weight loss. Obesity, in the absence of identifiable cardiovascular risk factors, was associated with significantly impaired myocardial high energy phosphate metabolism (PCr/ATP ratio, normal; 2.03 ± 0.27 vs. obese; 1.58 ± 0.47, p = 0.002) and significantly lower peak diastolic filling rate (normal; 4.8 ± 0.8 vs. obese; 3.8 ± 0.7 EDV/s, p = 0.01). Weight loss (on average 9 kg, 55% excess weight) over 1 year resulted in a 24% increase in PCr/ATP ratio (p = 0.01) and an 18% improvement in peak diastolic filling rate (p = 0.01). Myocardial PCr/ATP ratio remained positively correlated with peak diastolic filling rate after weight loss (r = 0.63, p = 0.02). In obesity, weight loss improves impaired cardiac energetics and myocardial relaxation. Improved myocardial energetics appear to play a key role in diastolic functional recovery accompanying weight loss.

7 Tesla (T) human cardiovascular magnetic resonance imaging using FLASH and SSFP to assess cardiac function: validation against 1.5 T and 3 T

We report the first comparison of cardiovascular magnetic resonance imaging (CMR) at 1.5 T, 3 T and 7 T field strengths using steady state free precession (SSFP) and fast low angle shot (FLASH) cine sequences. Cardiac volumes and mass measurements were assessed for feasibility, reproducibility and validity at each given field strength using FLASH and SSFP sequences. Ten healthy volunteers underwent retrospectively electrocardiogram (ECG) gated CMR at 1.5 T, 3 T and 7 T using FLASH and SSFP sequences. B1 and B0 shimming and frequency scouts were used to optimise image quality. Cardiac volume and mass measurements were not significantly affected by field strength when using the same imaging sequence (P > 0.05 for all parameters at 1.5 T, 3 T and 7 T). SSFP imaging returned larger end diastolic and end systolic volumes and smaller left ventricular masses than FLASH imaging at 7 T, and at the lower field strengths (P < 0.05 for each parameter). However, univariate general linear model analysis with fixed effects for sequence and field strengths found an interaction between imaging sequence and field strength (P = 0.03), with a smaller difference in volumes and mass measurements between SSFP and FLASH imaging at 7 T than 1.5 T and 3 T. SSFP and FLASH cine imaging at 7 T is technically feasible and provides valid assessment of cardiac volumes and mass compared with CMR imaging at 1.5 T and 3 T field strengths.

Assessment of left atrial volumes at 1.5 Tesla and 3 Tesla using FLASH and SSFP cine imaging

PURPOSE

To investigate left atrial volumes and function and their variability in healthy volunteers using steady state free precession (SSFP) and fast low angle shot (FLASH) sequences at both 1.5 and 3 T using both the short-axis and biplane area-length methods.

MATERIALS AND METHODS

Ten healthy volunteers underwent CMR at both 1.5 and 3 Tesla. The biplane area-length method utilized volumes from the horizontal and vertical long axis images.

RESULTS

There were no significant differences between left atrial short-axis volumes or function between 1.5 and 3 T assessed using either FLASH or SSFP sequences. The biplane area-length method underestimated maximal left atrial volume using FLASH by 12 mL at 3 T (18%) and by 10 mL (14%) at 1.5 T (p = 0.003 and p = 0.05 respectively). Variability was larger for left atrial measurements using the biplane area-length method.

CONCLUSION

Field strength had no effect on left atrial volume and function assessment using either FLASH or SSFP. The use of the short-axis method for the acquisition of left atrial parameters is more reproducible than the biplane area-length for serial measurements.

Magnetic resonance imaging of facial muscles

Facial and tongue muscles are commonly involved in patients with neuromuscular disorders. However, these muscles are not as easily accessible for biopsy and pathological examination as limb muscles. We have previously investigated myasthenia gravis patients with MuSK antibodies for facial and tongue muscle atrophy using different magnetic resonance imaging sequences, including ultrashort echo time techniques and image analysis tools that allowed us to obtain quantitative assessments of facial muscles. This imaging study had shown that facial muscle measurement is possible and that useful information can be obtained using a quantitative approach. In this paper we aim to review in detail the methods that we applied to our study, to enable clinicians to study these muscles within the domain of neuromuscular disease, oncological or head and neck specialties. Quantitative assessment of the facial musculature may be of value in improving the understanding of pathological processes occurring within facial muscles in certain neuromuscular disorders.

Evolution of the diffusion-weighted signal and the apparent diffusion coefficient in the late phase after minor stroke: a follow-up study

INTRODUCTION

Diffusion-weighted imaging (DWI) is mainly used in acute stroke, and signal evolution in the acute phase has been studied extensively. However, patients with a minor stroke frequently present late. Recent studies suggest that DWI may be helpful at this stage, but only very few published data exist on the evolution of the DW-signal in the weeks and months after a stroke. We performed a follow-up study of DWI in the late stages after a minor stroke.

METHODS

28 patients who presented 48 hours to 14 days after a minor stroke underwent serial MRI at baseline, 4 weeks, 8 weeks, 12 weeks, 6 months and>or=9 months after their event. Signal intensity within the lesion was determined on T2-weighted images, DW-images and the Apparent Diffusion Coefficient (ADC) map at each time-point, and ratios were calculated with contralateral normal values (T2r, DWIr, ADCr).

RESULTS

T2r was increased in all patients from the beginning, and showed no clear temporal evolution. ADCr normalized within 8 weeks in 83% of patients, but still continued to increase for up to 6 months after the event. The DW-signal decreased over time, but was still elevated in 6 patients after>or=6 months. The evolution of ADCr and DWIr showed statistically highly significant inter-individual variation (p<0.0001), which was not accounted for by age, sex, infarct size or infarct location.

CONCLUSION

The ADC and the DW-signal may continue to evolve for several months after a minor ischaemic stroke. Signal evolution is highly variable between individuals. Further studies are required to determine which factors influence the evolution of the ADC and the DW-signal.

Cardiovascular Magnetic Resonance Imaging for Non-Invasive Assessment of Vascular Function: Validation against Ultrasound

Ultrasound is an established modality for quantification of vascular function in clinical studies of cardiovascular disease. We determined whether cardiovascular magnetic resonance imaging (CMR) can provide a comparable assessment of vascular function. In seventeen control subjects, we used CMR to quantify endothelium-dependent (flow mediated dilatation, FMD) and endothelium-independent dilatation of the brachial artery, brachial and carotid distensibility, aortic compliance, and pulse wave velocity. These were compared to brachial and carotid measurements obtained by established ultrasound protocols. Twelve of the volunteers then underwent repeated measurements with both modalities. There was good agreement between imaging modalities for measures of endothelial function and arterial structure in the same subjects (difference between CMR and ultrasound for FMD = 0.14 +/- 6.8%, and brachial artery area = - 0.7 +/- 2.2 mm2, correlation between modalities for FMD = 0.62, p = 0.01 and for area = 0.87, p = < 0.0001). Inter-study reproducibility was also similar (coefficient of variation (CV) for FMD: CMR = 0.3, ultrasound = 0.3, CV for brachial artery area: CMR = 0.1, ultrasound = 0.1). Comparability and reproducibility were not as strong for functional measures if repeated studies were several days apart (CV for FMD by ultrasound on the same day = 0.1 and several days apart = 0.4). CMR and ultrasound show good agreement for quantitative measures of vascular structure and function with good reproducibility for both modalities. The major advantage of CMR is that it allows one-stop integrated assessment of both peripheral and central measures of vascular function.

Improved cine cardiovascular magnetic resonance using Clariscan (NC100150 injection)

We evaluated the use of Clariscan 0.75, 2, and 5 mg Fe/kg body weight in six patients to determine optimal dosing for short repetition time cine imaging. Breathhold cine images were acquired in the vertical and horizontal long axes and the short axis. Blood-pool signal-to-noise ratio increased significantly in all planes (p < 0.01) but was least marked in the short axis. Myocardial signal-to-noise ratio increased by a lesser amount (p < 0.05). Myocardial to blood-pool signal-difference-to-noise ratio improved significantly in the long axes (p < 0.05) and was greatest at 2 mg Fe/kg body weight, but changes in the short axis were minor. With the 5-mg Fe/kg body weight dose, the response was reduced or reversed due to T2* effects. Visual assessment improved in all planes (p < 0.05) and was optimal at 2 mg Fe/kg body weight. In conclusion, Clariscan improves short repetition time cardiac breathhold cine imaging, particularly in the long axis planes, with an optimal dose of 2 mg Fe/kg body weight.

Multiple behavioral effects of cocaine- and amphetamine-regulated transcript (CART) peptides in mice: CART 42-89 and CART 49-89 differ in potency and activity

Cocaine- and amphetamine-regulated transcript (CART) encodes a neuropeptide precursor protein that is highly abundant in cells of the hypothalamus. To date, the major research focus into the function of CART peptides has been feeding behavior. However, CART mRNA is found in other areas of the brain as well as some peripheral tissues, suggesting possible broader functions of this peptide. In this study, we investigated the effects of two CART peptides, CART 42-89 and CART 49-89, in several behavioral assays. Peptides were administered by i.c.v. route of administration. Both CART 42-89 and CART 49-89 inhibited food intake with the minimally effective dose of CART 42-89 (0.5 microg) being 5-fold greater than that of CART 49-89 (0.1 microg). Both peptides also produced significant antinociceptive effects in the hot-plate assay with similar potency differences. CART 42-89 significantly inhibited the acoustic startle response (ASR) of pulse alone trials at doses of 0.1 and 0.5 microg. In contrast, CART 49-89 did not affect ASR of pulse alone trials at doses of 0.05 and 0.1 (microg). For prepulse inhibition (PPI) trials, in general, both peptides appeared to enhance the magnitude of PPI and CART 42-89 was less potent than CART 49-89. Overall, these data suggest CART peptides may have multiple roles in central nervous system function and there may be biological differences between two processed forms of CART peptide.

Establishment and performance of a magnetic resonance cardiac function clinic

Our objective was to establish a cardiovascular magnetic resonance (CMR) cardiac function clinic to provide an assessment of cardiac volume, mass, and function in patients with heart failure on the same day as their cardiology outpatient clinic appointment. Sixty-four patients attended the CMR function clinic. The reproducibility, patient acceptability, and time efficiency of the CMR clinic were assessed and compared with radionuclide ventriculography (RNV) and echocardiography (echo). Reports were available in the cardiology outpatient clinic within 2 hr of the CMR appointment time. The reproducibility of volumes, ejection fraction, and mass in this heart failure population was good and comparable with CMR studies in the normal population. CMR was more acceptable to the patients than both RNV and echo (p < 0.05). The total time for CMR was less than that of RNV (42 +/- 4 and 61 +/- 4 min, respectively; p < 0.001) but more than that of echo (echo, 23 +/- 2 min; p < 0.001). Comparison of ejection fractions revealed a correlation between CMR and RNV of 0.7, but Bland-Altman limits of agreement were wide (-10.5% to 18.9%). For CMR versus echo, the correlation was 0.6, and the limits of agreement were wider (-29.9% to 23.3%). The correlation between RNV and echo was 0.2 with wider limits of agreement (-29.8% to 24. 9%). In conclusion, CMR can provide a rapid, reproducible, and patient acceptable assessment of cardiac function in heart failure patients, whereas other methods appear to have a wider variance. The high reproducibility of CMR lends itself to the follow-up of clinical progression and the effect of treatment in patients with heart failure.

Treatment of claustrophobia for cardiovascular magnetic resonance: use and effectiveness of mild sedation

Claustrophobia is associated with cardiovascular magnetic resonance (CMR) due to the nature of the technique and lengthy examination times. We report the incidence and treatment of claustrophobia in a prospective study on the use of intravenous (IV) and oral diazepam for CMR from August 1997 to June 1999 in 1754 adult patients referred for clinical (1226) and research (528) purposes. Patients under 16 yr of age and adults with learning difficulties were excluded. The initial refusal rate of clinical and research patients was 4.2% (54 clinical and 19 research). Because ethical approval to administer diazepam to research patients had not been granted at the beginning of this study, further analysis of the results excludes the 19 research patients. Of the 54 clinical patients, 31 were given IV diazepam (mean dose, 7.5 mg; range, 2.5-20 mg) with successful scanning in 30 (97%). Eight patients refused sedation, and scanning was not possible. The examination was attempted without sedation by five patients in the claustrophobic group and was terminated early; however, sufficient diagnostic information had been acquired in all cases. A further four patients took oral diazepam up to 1 hr before their appointment, with a 100% success rate. Three patients refused to attend the department due to known severe claustrophobia (2) and concerns over gradient noise (1), and three had medical contraindications to diazepam. Therefore, after the administration of diazepam to alleviate claustrophobia, the failure rate decreased to from 54 (4.4% of clinical patients) to 20 (1.6%) patients, a reduction of 63%. When it is possible to give diazepam to patients with claustrophobia at the time of CMR, it is a safe, predictable, and highly effective method of obtaining a successful result. A protocolfor the use of diazepam has been developed and is now also approved by our institutional ethics committee for use in research patients.

Use of the intravascular contrast agent NC100150 injection in spin-echo and gradient-echo imaging of the heart

This is the first study of the intravascular iron oxide particle contrast agent, NC100150 Injection (Nycomed Imaging AS, Oslo, Norway, a part of Nycomed Amersham) in magnetic resonance imaging of the human heart. Eighteen healthy male volunteers were studied at both 0.5 and 1.5 T before and after the administration of NC100150 Injection. Transaxial spin-echo images were acquired at both field strengths, conventional gradient-echo cine images at 0.5 T, and breathhold Turbo-FLASH cine images at 1.5 T. Optimized cine imaging sequences were used postcontrast, with a high flip angle of 60-70 degrees. In the spin-echo images there was a significant reduction in the blood pool flow artifact at the level of the right atrium (0.5 T, 57%, p < 0.01; 1.5 T, 41%, p = 0.01) and the left ventricle (LV) (0.5 T, 45%, p = 0.01; 1.5 T, 45%, p < 0.01). In the conventional gradient-echo cines at 0.5 T, there was a significant increase in the LV blood pool and myocardial signal difference-to-noise ratio (SDNR) in the diastolic (56%, p = 0.01) and systolic (141%, p < 0.001) frames. There was also a significant increase in the signal intensity (SI) gradient at the LV blood pool-myocardial border in the diastolic and systolic frames (both p < 0.001). At higher doses of NC100150 Injection (3 and 4 mg/kg), a rim of signal void around the LV blood pool was observed, perfectly defining the LV blood pool-myocardial border. In the Turbo-FLASH breathhold cines at 1.5 T, there was a significant increase in the LV blood pool-myocardial SDNR in the diastolic (221%, p < 0.001) and systolic (916%, p < 0.001) frames. Again, there was also a significant increase in the SI gradient at the LV blood pool-myocardial border in the diastolic and systolic frames (both p = 0.003). In conclusion, NC100150 Injection was given safely to 18 healthy subjects. Image quality and LV blood pool-myocardial definition were improved after the administration of NC100150 Injection. These improvements enable better spin-echo anatomical definition, better definition of myocardial wall motion, and should improve the capability of automated edge detection algorithms.

Reduction in sample size for studies of remodeling in heart failure by the use of cardiovascular magnetic resonance

Fast breathhold cardiovascular magnetic resonance (CMR) has become a reference standard for the measurement of cardiac volumes, function, and mass. The implications of this for sample sizes for remodeling studies in heart failure (HF) have not been elucidated. We determined the reproducibility of CMR in HF and calculated the sample size requirements and compared them with published values for echocardiography. Breathhold gradient echo cines of the left ventricle were acquired in 20 patients with HF and 20 normal subjects. Sample size values were calculated from the interstudy standard deviation of the difference. The percentage variability of the measured parameters in our HF group of intraobserver (2.0-7.4%), interobserver (3.3-7.7%), and interstudy (2.5-4.8%) measurements was slightly larger than for our normal group (1.6-6.6%, 1.6-7.3%, and 2.0-7.3%, respectively) but remained comparable with previous studies in normal subjects. The calculated sample sizes in patients with HF for CMR to detect a 10-ml change in end-diastolic volume (n = 12) and end-systolic volume (n = 10), a 3% change in ejection fraction (n = 15), and a 10-g change in mass was (n = 9) were substantially smaller than recently published values for two-dimensional echocardiography (reduction of 81-97%). Breathhold CMR is a fast comprehensive technique for the assessment of cardiac volumes, function, and mass in HF that is accurate but also highly reproducible. This allows a considerable reduction in the patient numbers required to prove a hypothesis in research studies, which suggests a potential for important research cost savings.

The analgesic potential of intraventricular polymer-encapsulated adrenal chromaffin cells in a rodent model of chronic neuropathic pain

Adrenal chromaffin cells reportedly produce analgesic effects when implanted in the periaqueductal gray and the intrathecal space near the spinal cord. Chromaffin cells implanted in the cerebral ventricles may also produce analgesic effects, and the availability of the cerebral ventricles as a potential implant site could be advantageous for some patients. In fact, some of the first patients were implanted in the intraventricular site, even though the analgesic potential of that site had never been demonstrated. The present study was conducted to assess the analgesic potential of intraventricular, polymer-encapsulated calf adrenal chromaffin cells in the Bennett model. Sciatic nerve ligations produced substantial, long-lasting pain-related behaviors. However, there was no evidence that polymer-encapsulated adrenal chromaffin cells implanted in the cerebral ventricles produce analgesic effects in this model of chronic neuropathic pain.

Transforming growth factor-beta 1 induces apoptosis independently of p53 and selectively reduces expression of Bcl-2 in multipotent hematopoietic cells

Transforming growth factor-beta1 (TGF-beta1) can inhibit cell proliferation or induce apoptosis in multipotent hematopoietic cells. To study the mechanisms of TGF-beta1 action on primitive hematopoietic cells, we used the interleukin-3 (IL-3)-dependent, multipotent FDCP-Mix cell line. TGF-beta1-mediated growth inhibition was observed in high concentrations of IL-3, while at lower IL-3 concentrations TGF-beta1 induced apoptosis. The proapoptotic effects of TGF-beta1 occur via a p53-independent pathway, since p53(null) FDCP-Mix demonstrated the same responses to TGF-beta1. IL-3 has been suggested to enhance survival via an increase in (antiapoptotic) Bcl-x(L) expression. In FDCP-Mix cells, neither IL-3 nor TGF-beta1 induced any change in Bcl-x(L) protein levels or the proapoptotic proteins Bad or Bax. However, TGF-beta1 had a major effect on Bcl-2 levels, reducing them in the presence of high and low concentrations of IL-3. Overexpression of Bcl-2 in FDCP-Mix cells rescued them from TGF-beta1-induced apoptosis but was incapable of inhibiting TGF-beta1-mediated growth arrest. We conclude that TGF-beta1-induced cell death is independent of p53 and inhibited by Bcl-2, with no effect on Bcl-x(L). The significance of these results for stem cell survival in bone marrow are discussed.

Bcr-Abl protein tyrosine kinase activity induces a loss of p53 protein that mediates a delay in myeloid differentiation

Chronic myeloid leukaemia is a haemopoietic stem cell disorder, the hallmark of which is the expression of the Bcr-Abl Protein Tyrosine Kinase (PTK). We have previously reported that activation of a temperature sensitive Bcr-Abl PTK in the multipotent haemopoietic cell line FDCP-Mix for short periods resulted in subtle changes including, a transient suppression of apoptosis and no inhibition of differentiation. In contrast, activation of the Bcr-Abl PTK for 12 weeks results in cells that display a delay in differentiation at the early granulocyte stage. Flow cytometric analysis also indicates that the expression of cell surface differentiation markers and nuclear morphology are uncoupled. Furthermore, a significant number of the mature neutrophils display abnormal morphological features. Prolonged exposure to Bcr-Abl PTK results in interleukin-3 independent growth and decreased p53 protein levels. FDCP-Mix cells expressing a dominant negative p53 and p53null FDCP-Mix cells demonstrate that the reduction in p53 is causally related to the delay in development. Returning the cells to the restrictive temperature restores the p53 protein levels, the growth factor dependence and largely relieves the effects on development. We conclude that prolonged Bcr-Abl PTK activity within multipotent cells results in a reduction of p53 that drives a delayed and abnormal differentiation.

Intrathecal polymer-encapsulated bovine adrenal chromaffin cells fail to produce analgesic effects in the hotplate and formalin test

Numerous publications have reported that adrenal chromaffin cells implanted in the lumbar intrathecal space produce analgesic effects in rodent models of pain. The present study was intended to replicate and extend on the results of those previous publications. This study was conducted to determine: (1) if analgesic effects of polymer-encapsulated intrathecal adrenal chromaffin cells could be detected in the more sensitive low temperature hot-plate test without using nicotine to stimulate chromaffin cell output, (2) if a dose-response curve can be produced in the hot-plate and formalin tests with different numbers of adrenal chromaffin cells (0K, 120K, or 330K), (3) if cell viability and/or the magnitude of analgesic effects are affected by differences in implant site (i.e. thoracic versus lumbar implant site), and (4) the magnitude of the analgesic effects of adrenal chromaffin cells relative to doses of systemic morphine. No analgesic effects related to chromaffin cells were detected in the present study in the formalin test or in the hot-plate test, even with nicotine stimulation, regardless of the number of cells implanted or the intrathecal implant site. The reliability and sensitivity of the behavioral measures to the effects of mild analgesics are supported by the fact that consistent differences in performance between individual rats could be detected, the effects of fairly modest doses of nicotine and morphine were detectable, and consistent dose-response curves were evident with respect to both nicotine and morphine. Device performance appeared to be within the range of previous studies that reported analgesic effects of encapsulated adrenal chromaffin cells. It is unclear why analgesic effects of adrenal chromaffin cells were not detected in the present study.