Biomedical subjects
Publications and source records attributed to B Maraviglia.
Perdeuterated palmitic acid was intercalated into the human erythrocyte membrane and its motion studied by dueterium nuclear magnetic resonance (2H-NMR). From analysis of temperature dependent changes in the 2H-NMR spectra and from an analysis of derived moments we conclude that the acyl chains of the erythrocyte lipids do not exhibit a detectable phase transition.
The membrane fluidity of erythrocytes from patients with Lecithin: cholesterol acyltransferase (LCAT) deficiency was studied by means of electron spin resonance. The temperature dependence of the separation of the outer extrema of the spectra of 2-(3-carboxy-propyl)-4,4-dimethyl, 2-tridecyl-3-oxazolidinyloxyl spin probe was monitored for normal, presumed carrier and clinically affected subjects. The temperature profile of controls was significantly different from that of the presumed carriers and the clinically affected individuals. The results show that the compositional abnormalities previously noted in erythrocyte membranes from patients with LCAT deficiency are associated with alterations in the physiocochemical state of the membrane. An investigation of the spectral lineshapes below 10 degrees C allowed a distinction to be made at the membrane level between clinically affected subjects and clinically normal heterozygous carriers. Alterations in the temperature dependence of elec-ron spin resonance parameters may provide a sensitive index of red cell membrane alterations in pathological states of generalized membrane involvement.
In this paper we discuss the possibility of modifying the multiple spin echoes existing theory, developed for a homogeneous system, to describe also an inhomogeneous system such as a porous medium. We report here the first experimental application of MSE methods to materials like travertine. The ratio A(2)/A(1) from water in travertine presents minima for characteristic values of the delay time tau, like what was previously observed in the trabecular bone. By a judicious choice of the delay time tau and of the G gradient strength, the MSE sequence can be made sensitive to a specific length-scale of the sample heterogeneity. Furthermore the MSE image shows a particular new contrast that makes the non linear NMR method very attractive for the assessment of variations of the porous structure in porous systems.
In heterogeneous systems the amplitude of the intermolecular double-quantum (DQ) signal depends on sample heterogeneity over a correlation distance dc=pi/(gammaGct). In this paper two different CRAZED-type sequences were applied in a porous medium phantom. One of these sequences gives rise to a DQ-T2 weighted signal, while the other one gives rise to a DQ-T2* weighted signal. Experimental results indicate that tuning of the correlation distance dc in a porous medium can alter the DQ signal in a manner which depends on the microstructure. This is evident only using the CRAZED-type sequence which gives rise to a DQ-T2* weighted signal.
Nuclear Magnetic Resonance was employed to obtain information on the pore filling during the absorption process. A porous carbonate stone, largely employed for buildings and mainly outdoor decorations was studied during water absorption by capillary rise, and filled pores radii were evaluated by comparison between experimental and theoretical parametric magnetization decay curves. Non mono-exponential T2 allowed spin populations to be split among the associated different relaxation times.