Metabolic parameters after BioEnterics Intragastric Balloon placement in obese patients.

BACKGROUND: BioEnterics Intragastric Balloon (BIB) is a non-invasive, temporary and relatively safe procedure shown to be effective in the short-term treatment of obesity. Nowadays, BIB does not show convincing evidence of significant long-term weight loss, as compared with conventional management, and data regarding changes in metabolic and nutritional parameters are lacking. METHODS: Forty obese patients [11 males, 29 females, age 36.65+/-10.6 yr, body mass index (BMI) 44.9+/-8.9 kg/m2] were evaluated before and 3 and 6 months after BIB placement by assessment of anthropometric and biochemical parameters as well as nutritional habits. RESULTS: Patients showed a significant reduction in weight (-13.2+/-6.5%), BMI (-13.2%), waist circumference (-6.5 cm), and percentage of fat mass (-19.5%), but not fat-free mass. A significant improvement in insulin sensitivity but not in lipid pattern was seen. After BIB insertion, a significant reduction in caloric intake was paralleled by a redistribution of nutrients; in particular, increased lipid (12.8%) and decreased carbohydrate (-11.7%) percentage, but not absolute intake was observed. CONCLUSION: These data show that BIB improves anthropometric parameters, with reduction of fat mass and preservation of fat-free mass, as well as insulin resistance, but not other metabolic features. The observed change in dietary habits, with a relative increase in lipid intake, once BIB is removed, might favor body weight regain and impact negatively on body weight composition and the other traits of the metabolic syndrome.

Correlation MRI/ultrastructure in cerebral ischemic lesions: application to the interpretation of cortical layered areas.

The origin and fate of cortical ischemic lesions, showing a stratified appearance at in vivo MRI-examination, was studied on rats in which a focal brain ischemia was induced by occlusion of the middle cerebral artery. One week after ischemia induction, six rats were selected in which three layers of different intensity were visible in the lesioned cortex. Two animals were sacrificed and studied by histology and electron microscopy. The external hyperintense layer was composed of pial and lesioned nervous tissue, the intermediate of degenerating nervous tissue in which an accumulation of macrophages was found, the deepest of edematous nerve tissue without a marked accumulation of macrophages. The remaining rats underwent further MRI examinations showing that, in the lesioned areas, cerebral blood volume was 14-69% lower than the contralateral healthy cortex. At histological and ultrastructural examination, a large part of the lesion was occupied by enlarged pial tissue and marginal glia. A dilatation of the ventricular cavity and cystic structures were also visible. In three animals an increase of the transverse diameter of the caudo-putamen ipsilateral to the lesion was found. The study suggests that the layered appearance is mainly due to an accumulation of macrophages in the intermediate layer and that several processes contribute to the occlusion of the space created by the removal of the necrotic tissue in stratified ischemic lesions (i.e. expansion of the pial tissue, thickening of the marginal glia; expansion of the caudo-putamen, enlargement of the ventricular cavity and development of cystic structures).

Polyunsaturated fatty acids mapping by (1)H MR-chemical shift imaging.

Parametric mapping of polyunsaturated fatty acids (PUFA) distribution in adipose tissues was obtained by (1)H chemical shift imaging (CSI). A matrix of spectra, acquired with a CSI sequence having two spatial and one spectroscopic dimension, was processed with ad hoc algorithms. The protocol was applied to phantoms containing different lipids in which the degree of polyunsaturation was determined by high-resolution nuclear magnetic resonance (NMR). High correlation (R(2) = 0.998) between degrees of polyunsaturation given by our protocol and that measured by high-resolution NMR was found. The thoracic region of rats was also examined. Parametric maps of the polyunsaturation degree were obtained for the brown adipose tissue and the white axillary fat: the first deposit was found more polyunsaturated than the second. Finally, in vivo mapping of the inguinal region of the rat was produced that allowed us to individuate PUFA-rich areas in adipose tissue. This work demonstrates the feasibility of PUFA imaging in vivo.

Delayed muscle injuries in arterial insufficiency: contrast-enhanced MR imaging and 31P spectroscopy in rats.

PURPOSE: To evaluate whether the vascular system resulting from an arterial lesion shows differences in permeability to a tracer with respect to the normal vascular system and whether eventual differences are maintained for long periods. MATERIALS AND METHODS: Permanent ischemia was induced in rats with femoral arterial removal, and magnetic resonance (MR) imaging was performed after 1, 7, 14, and 90 days. Gadopentetate dimeglumine was injected, and the kinetics of its penetration in the leg were studied. Phosphorus 31 spectroscopy was performed to determine the bioenergetic characteristics of the gastrocnemius muscle at rest and stimulation. Ischemic muscles were then processed for electron microscopy. RESULTS: After ischemia induction, a hyperintense area that progressively decreased was present on T2-weighted images. Gadopentetate dimeglumine improved the signal intensity of the area. Three months after arterial occlusion, the contrast-enhanced images still showed microvessels highly permeable to the tracers. Spectroscopic data revealed that 3 months after arterial removal, the bioenergetic reserve of the gastrocnemius muscle was reduced, suggesting that the contrast-enhanced MR imaging-visible area is functionally relevant. Ultrastructural examination revealed persistent muscle damage and signs of chronic microangiopathy. CONCLUSION: After ischemia induction, the restitutio ad integrum is not complete, and delayed muscle injuries can result from arterial insufficiency.

In-vivo quantitative hydrolipidic map of perirenal adipose tissue by chemical shift imaging at 4.7 Tesla.

OBJECTIVE: In this work, chemical shift magnetic resonance imaging is used for in vivo quantitative evaluation of fat and water content in the perirenal white adipose tissue. DESIGN AND MEASUREMENTS: Experiments were carried out on female Sprague-Dawley rats with a 4.7 T magnet. Fat and water fractions were computed pixel-by-pixel from the chemical shift selective images with an algorithm of reconstruction that allowed parametric maps (called hydrolipidic maps) to be produced with a pixel size of 625 x 625 microm. RESULTS: Our findings indicate that, in the perirenal adipose tissue, the water content ranges between 15% and 20%, with slight differences between the ventral and dorsal portions, and between the left and right deposits. The mesenteric adipose tissue, observed for comparison, has a mean water content of 30%. CONCLUSION: The present work demonstrates that methods based on magnetic resonance imaging can be useful tools for non-invasive in vivo quantitative mapping of the hydrolipidic content of adipose tissues.

Regional cerebral blood volume mapping after ischemic lesions.

The possible persistence of a microvascular deficit at long time intervals after cerebral ischemia induction is not well established. In rats, we have generated in vivo maps of the regional cerebral blood volume (rCBV) at different time intervals after middle cerebral artery occlusion (MCAo) with the aim to evaluate the persistence of a rCBV deficit in the damaged area or in the surrounding regions. The rats were examined by magnetic resonance imaging (MRI) at different time intervals, starting from the first day until three months after ischemia and postmortem histological and ultrastructural correlation was obtained. All MRI experiments were carried out using an imager-spectrometer equipped with a 4.7 Tesla magnet. To produce the susceptibility-weighted rCBV images, a suspension of superparamagnetic iron oxide nanoparticles (AMI-25) was injected to the rat. In a control group (nonoperated or sham-operated rats), a symmetrical distribution of rCBV values was found between the two hemispheres (differences between left and right cortex below 8%). In the rats with MCAo an evident vascular asymmetry was found 24 h after ischemia (differences between left and right ranging from 22 and 77%) and reduced rCBV values were evident in the ischemic areas. In a time range following the 15th day most of the rats showed a complete recovery of the lesion while only four animals still had a small residual lesion, as probed by T2-weighted (T2W) images. In three of these four cases, the reduction of rCBV in the ipsilateral cortex with respect to the contralateral was greater than 20%. Correlation was found (Y > 0.8) between late rCBV measurement and the initial volume of the lesion (hyperintense region in T2W images). The postmortem measurements correlate much better with the rCBV data than with the T2W ones. In conclusion, the present work demonstrates that cortical lesions may result in a deficit of rCBV for long periods and that a mismatch between T2w and rCBV data can be present during the repair process.

New adiabatic inversion pulses for magnetic resonance imaging.

We present a comparison between our strategy of computing new adiabatic pulses and the best results given so far in the literature by Rosenfeld and co-workers. Our technique has been described elsewhere and is based upon a simple physical idea (the adiabatic factor is offset independent) and an evolution strategy algorithm which stochastically searches for a 'solution' with optimal inversion profile and power characteristics. As expected for all adiabatic pulses, the inversion profiles are similar for our solutions and those of the literature. On the other hand, some of our pulses offer a substantial reduction of peak and average power relative to the solutions of Rosenfeld. We discuss the properties of the families of analytical functions, where, in our opinion, it is convenient to search for a pulse shape with optimal inversion profile and power characteristics.

In vivo quantitative lipidic map of brown adipose tissue by chemical shift imaging at 4.7 Tesla.

In the present paper, chemical shift imaging techniques are applied to quantitative in vivo evaluation of fat and water content in interscapular brown adipose tissue (BAT). The experiments have been carried out on five female Sprague-Dawley rats after calibration and testing with suitable phantoms containing known amounts of water and oil. We found that, in the interscapular BAT, the fat is about 50% at the surface (mainly unilocular) region, but its percentage drops to 20;-30% in the deepest (mainly multilocular) portion. The perirenal deposits of white adipose tissue (WAT) contained significantly higher amount of fat with large areas ranging from 70 to 90%. Later the rats were killed and the same procedure was repeated with dead animals. Experiments performed in dead rats show a modification of the hydro-lipidic ratio more evident in the multilocular portions of the deposit. The present work demonstrates that MRI-based methods allow a non-invasive, in vivo quantitative mapping of the lipid content which can be applied to investigation of brown adipose tissue deposits in small experiment animals.

Evolution strategy optimization for adiabatic pulses in MRI.

We propose a new type of adiabatic pulses for uniform inversion of the magnetization in magnetic resonance imaging. We produced these pulses with an evolution strategy optimization, by which the search of the "best solution" has been made more efficient than by deterministic algorithms. The pulse parametrization takes into account an "offset-independent adiabaticity condition," which guarantees insensitivity to RF inhomogeneities. The RF pulse power (both peak and mean) contributes to the cost to be minimized, as well as the error function does: in this way we obtain solutions that require lower energy than the well-known hyperbolic-secant pulse, with no loss of quality in the response profile.

Evolution strategy optimization for selective pulses in NMR

We present a first set of improved selective pulses, obtained with a numerical technique similar to the one proposed by Geen and Freeman. The novelty is essentially a robust and efficient "evolution strategy" which consistently leads, in a matter of minutes, to "solutions" better than those published so far. The other two ingredients are a "cost function," which includes contributions from peak and average radiofrequency power, and some understanding of the peculiar requirements of each type of pulse. For example, good solutions for self-refocusing pulses and "negative phase excitation pulses" (which yield a maximum signal well after the end of the pulse) are found, as may have been predicted, among amplitude modulated pulses with 270 degrees tip angles. Emphasis is given to the search for solutions with low RF power for selective excitation, saturation, and inversion pulses. Experimental verification of accuracy and power requirements of the pulses has been performed with a 4.7 T Sisco imager. Copyright 1998 Academic Press.