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Accuracy on quantitative PET image analysis relies on the correct application of attenuation correction which is one of the major challenges for PET/MRI that remains to be solved. The purpose of this study is to evaluate the effect of MRI-based attenuation maps and the use of flexible coils on the quantitative accuracy of PET images with a special focus on large arteries.

The functionalization of iron oxide superparamagnetic nanoparticles (NP) is one of the most active research fields due to the necessity of robust and, particularly, reproducible methods for the attachment of new biomolecules on the surface. Olefin metathesis offers many of these features, thanks to the new family of catalysts, especially Hoveyda-Grubbs second generation. Iron oxide NP were synthesized by the decomposition of organic precursors obtaining hydrophobic Fe3O4NP with oleic acid as surfactant. These NP have been functionalized by the use of olefin metathesis reaction with different ligands. The metathesis was performed between the double bond in oleic acid structure and four different molecules with a terminal olefin, methyl acrylate, 6-hexenenitrile, allyltrifluoroacetate and 3-allyloxy-1,2-propandiol, in presence of the catalyst. These new NPs were fully characterized showing the success of the functionalization, small hydrodynamic size, narrow size distribution, and stability in water. This proof of concept opens a new way for the formation of carbon–carbon bonds on the surface of NP for biomedical applications.

Magnetic resonance imaging (MRI) is studied under an online strategy. Axial FLASH images (780 ms acquisition time) have been analyzed to identify seed‐containing oranges conveyed at 50 and 100 mm/s through a 4.7 Tesla spectrometer. Developed algorithms enable an automated identification of oranges with more than one seed, though axial images under motion conditions suffer from significant blurring artifacts. To overcome this hindrance, coronal FLASH images have been acquired (279 ms acquisition time), developing devoted algorithms for motion correction with encouraging results for quality improvement of dynamic images. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 26B: 81–92, 2005.

Freeware called MRS_Controller and written for Windows is described. It may be used to control magnetic resonance spectrometers or postprocess data, and is composed of four modules that may carry out field stabilization, graphical pulse sequence edition, experiment planning, and spectral data postprocessing. The control of a commercial Tesla BS587A spectrometer was performed with this software through an independent dynamic link library. It may easily be rewritten to allow the control of other types of spectrometers. This software can also be used for spectral data postprocessing and for planning or preparing experiments offline because hardware access is disabled when an instrument is not detected at startup. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 16B: 1–14, 2003

ObjectiveThe progressive early changes in cartilage and subchondral bone in an experimental model of osteoarthritis (OA) were investigated with high-resolution magnetic resonance imaging (MRI) and microradiography.

The mechanism of tumor necrosis factor alpha (TNFalpha)-induced cytotoxicity in metabolically inhibited cells is unclear, although some studies have suggested that mitochondrial dysfunction and generation of reactive oxygen species may be involved. Here we studied the effect of TNFalpha on the redox state of mitochondrial cytochromes and its involvement in the generation of reactive oxygen species in metabolically inhibited L929 cells. Treatment with TNFalpha and cycloheximide (TNFalpha/CHX) induced mitochondrial cytochrome c release, increased the steady-state reduction of cytochrome b, and decreased the steady-state reduction of cytochromes cc(1) and aa(3). TNFalpha/CHX treatment also induced lipid peroxidation, intracellular generation of reactive oxygen species, and cell death. Furthermore, as the cells died mitochondrial morphology changed from an orthodox to a hyperdense and condensed and finally to a swollen conformation. Antimycin A, a mitochondrial respiratory chain complex III inhibitor that binds to cytochrome b, blocked the formation of reactive oxygen species, suggesting that the free radicals are generated at the level of cytochrome b. Moreover, antimycin A, when added after 3 h of TNFalpha/CHX treatment, arrested the further release of cytochrome c and the cytotoxic response. We propose that the reduced cytochrome b promotes the formation of reactive oxygen species, lipid peroxidation of the cell membrane, and cell death.

An intact, viable epidermal preparation was perfused and phosphoenergetic and phospholipid metabolite levels were measured by31P NMR. The preparation was stable in the NMR perfusion apparatus for 24 h. The effects of inclusion of ethanolamine and dexamethasone-21-acetate in the perfusion media on phosphorus-containing metabolites was assessed by examination of serial31P NMR spectra. Phospho-monoesters increased significantly during the fourth hour of perfusion with ethanolamine (3 mM) and remained elevated. A corresponding decrease in nucleotide triphosphates was noted, but phosphocreatine (PCr) remained unchanged. Dexamethasone perfusion resulted in a biphasic effect on phosphomonoester metabolism and a dose-dependent decrease in PCr and nucleotide triphosphate levels. A log-linear relationship was observed between dexamethasone dose in the 1–100-nM range and a decrease in PCr. These techniques with an isolated intact epidermal preparation are useful for elucidating mechanisms of corticosteroid action on the skin and serve as a basis for developing a mechanistically relevant topical corticosteroid bioequivalence technique.

The thermal behaviour of bovine-brain myelin membrane has been studied by high-sensitivity differential scanning calorimetry, Fourier-transform infrared spectroscopy and thermal gel analysis. Spectroscopic results indicate that protein transitions take place between 60°C and 90°C, while thermal gel analysis has provided the thermal denaturation profiles of myelin proteolipid, DM-20 protein and the Wolfgram Fraction. An irreversible calorimetric transition centred at 80.3 ± 0.2°C with a specific enthalpy of 4.7 ± 0.6 J/g of total protein has been assigned to the thermal denaturation of myelin proteolipid and DM-20 protein. The effects of the myelin storage conditions, scan rate, ionic strength and pH on this calorimetric transition have also been investigated. The thermal transition of the proteolipid practically disappears after treatment of the myelin with different amounts of chloroform-methanol 2:1 (v/v), a treatment which is generally used in proteolipid purification. On the other hand, the addition of several detergents to myelin only causes minor modifications to this transition, which then occurs at about 70°C, with a specific enthalpy of between 2.5 and 3.6 J/g of total protein. These results appear to show that detergents preserve the native conformation of the proteolipid far more than do organic solvents. Hence the use of detergents would seem to be the appropriate method for proteolipid purification.

Myelin proteolipid has been isolated from bovine brain and purified using organic solvents according to conventional procedures. The protein content of the purified sample, or crude proteolipid, contains a minimum of 75% w/w of proteolipid, with DM-20, a proteolipid molecule with an internal deletion of 35 out of 276 amino acid residues, as the only other component. Biochemical analysis has shown the differences in lipid composition between brain white matter, myelin and crude proteolipid preparations. The latter contained practically no cholesterol, while the other two samples had about 22-23% w/w. High-sensitivity differential scanning calorimetry experiments with both crude proteolipid and its extracted pool of lipids have shown similar reversible thermal transitions at 52°C and 48°C. The effect of increasing amounts of cholesterol on the two calorimetric transitions led in both cases to a continuous decrease in the melting temperature and in the transition enthalpy. Parallel Fourier-transform infrared spectroscopy studies of crude proteolipid have detected a reversible, co-operative lipid transition centred at 49 °C, with no detectable change in the amide region between 20°C and 60°C. Once more an increase in cholesterol content led to a decrease in the sharpness of this transition. It is concluded that the thermal transition detected in crude proteolipid, which has in the past been attributed to proteolipid thermal denaturation (Mateo et al. 1986), actually corresponds to a thermotropic phase transition of the lipids included in the crude proteolipid sample.

The interaction of myelin basic protein with cholesterol and the conformational changes occurring in the protein upon interaction with the lipid were investigated. The myelin basic protein (MBP) plays an important role in stabilizing the multilamellar structure of the myelin membrane. MBP interacts in a specific way with the lipids components of the membrane. The major lipid component is the cholesterol which comprises 40–44 mol% of the lipids. In order to understand the effect of the lipids in the protein conformation we have studied the interaction between MBP and cholesterol. The conformational changes induced in the protein upon interaction with different concentrations of cholesterol were characterized by transmission electron microscopy (TEM) and monolayer studies. Aqueous solution of MBP from bovine brain (obtained by the method of Cheifetz and Moscarello) exhibited a circular dichroism (CD) spectrum characteristic of random coil protein molecules. Upon addition of cholesterol, MBP–cholesterol complexes were observed by TEM. The monolayer compression experiments show plateaus in their surface pressure–area isotherms. The presence of these plateaus has previously been interpreted as α-helix conformation. By seeding the MBP onto the aqueous support, we have determined the compression work for the protein on the surface. Experimental areas of the mixtures MBP–cholesterol are smaller than the area calculated by adding the areas of the pure components, indicating that there are attractive forces between both components. The calculated entropy of compression indicates that the highest organization is reached when lipid and protein are almost in the same proportion.