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R Toffanin

Publications and source records attributed to R Toffanin.

At least 19 recordsLinked to original sources

Transverse relaxation mechanisms in articular cartilage.

Relaxation rates in the rotating frame (R1rho) and spin-spin relaxation rates (R2) were measured in articular cartilage at various orientations of cartilage layer to the static magnetic field (B0), at various spin locking field strengths and at two different static magnetic field strengths. It was found that R1rho in the deep radial zone depended on the orientation of specimens in the magnet and decreased with increasing the spin locking field strength. In contrast, R1rho values in the transitional zone were nearly independent of the specimen orientation and the spin locking field strength. Measurements of the same specimens at 2.95 and 7.05 T showed an increase of R1rho and most R2 values with increasing B0. The inverse B0 dependence of some R2 values was probably due to a multicomponent character of the transverse magnetization decay. The experiments revealed that the dominant T1rho and T2 relaxation mechanism at B0 < or = 3 T is a dipolar interaction due to slow anisotropic motion of water molecules in the collagen matrix. On average, the contribution of scalar relaxation due to rapid proton exchange in femoral head cartilage at 2.95 T is about 6% or less of the total R1rho at the spin locking field of 1000 Hz.

Cartilage, Articular↗

Are dyspepsia management guidelines coherent with primary care practice?

BACKGROUND: Spontaneous physician behaviour can affect guideline applicability, implementation strategies and application costs, particularly in relation to widespread pathologies chiefly managed by general practitioners (GPs). Of the array of dyspepsia management guidelines, the closest to general practice, partly owing to proposing committee composition, are the European Society for Primary Care Gastroenterology (ESPCG) guidelines. METHODS: To evaluate variability in dyspepsia management among GPs in Padua and divergence in spontaneous prescriptive behaviour from the ESPCG dyspepsia guideline, we prospectively studied the behaviour of 39 GPs over a 3-month period of outpatient activity, through questionnaires on each consultation. Test-group representativeness was preliminarily defined in terms of antisecretory drug expenditure. RESULTS: 1790 forms on dyspepsia-related consultations were studied in a population of 51,193 registered patients; 1264 patients with a history of dyspeptic pathology consulted their GP (19% duodenal ulcer (DU), 9% gastric ulcer (GU), 54% gastro-oesophageal reflux disease (GERD), 32% non-ulcer dyspepsia (NUD), 1% cholelithiasis), while 526 patients presented with symptoms of dyspepsia with no previous gastroscopy (EGDS) (42% were aged <45 years), of whom 42% had twice consulted their GP. Empirical management by prescription of symptomatic drugs was the most common procedure in DU (33%), GU (73%) and NUD (74%) relapses. Helicobacter pylori eradication therapy was prescribed in only 2% of patients with a history of organic or functional dyspepsia. 145 patients with uninvestigated dyspepsia were referred for second-level endoscopy and 43 for H. pylori testing. Forty-four percent of endoscopies prescribed for uninvestigated patients did not comply with the ESPCG guideline; full compliance would have determined a 105% rise in endoscopies. Prescriptive variability between GPs was high (based on the Goodman-Kruskal (0.41, P < 0.001) and Cramer tests (V = 0.51, P < 0.005)) and agreement between observed and expected prescriptions according to ESPCG criteria was as low as V = 0.11. On the basis of the most frequently observed behaviours, we developed three options of the ESPCG guideline and compared them to spontaneous prescriptions. CONCLUSIONS: Highest compliance emerged where the clinical approach for all patients with uninvestigated dyspepsia was symptomatic therapy at first presentation followed by a different attitude at second presentation, setting a higher cut-off age than in the guideline (which in our case proved, on mathematical calculation, to be 55 years).

Adult↗

Proteoglycan depletion and magnetic resonance parameters of articular cartilage.

Calcium ions and various amounts of proteoglycans were removed from porcine articular cartilage explants using ethylenediaminetetraacetic acid or guanidinium chloride solutions. The water proton magnetic parameters such as T(1) and T(2) relaxation times, diffusion (D), and magnetization transfer (M(S)/M(0)) were then measured by 1D MR microscopy on native specimens, after incubation in the extracting solutions and after final reconditioning in a physiological saline. While the replacement of the interstitial fluid by the treating solutions strongly affected the various MR parameters, calcium depletion did not show any influence on the MRI appearance of the chondral tissue. Interestingly, only the longitudinal relaxation time T(1) and the diffusion coefficient D were seen to be sensitive to an extensive proteoglycan depletion of the tissue. Our results indicate that a modest proteoglycan depletion, as it occurs in the early stage of a pathological cartilage degradation, has little relevance to the above MR parameters. Further MRI studies on the macromolecular components of cartilage are, therefore, necessary for a better understanding of the interaction mechanisms between water and extracellular matrix that might lead to the early diagnosis of the cartilage damage.

Animals↗

Collagen fibrils are differently organized in weight-bearing and not-weight-bearing regions of pig articular cartilage.

The magnetic resonance (MR) appearance of the weight-bearing ("loaded") and not-weight-bearing ("unloaded") regions in T(2)-weighted images of pig articular cartilage is different. On the hypothesis that this difference may be ascribed, at least in part, to a different collagen fibre organization in the two regions, this organization was studied using biochemical, histological, and X-ray diffraction methods. While the mean concentrations of collagen and of its cross-links were the same in the two regions, a regular small angle X-ray diffraction pattern was observed only for the habitually "loaded" tissue. It was also seen by light microscopy that the four typical functional zones were well displayed in the "loaded" cartilage whereas they were not clearly depicted in the "unloaded" tissue. Collagen presented a high concentration of fibrils forming an intricate and dense meshwork at the surface of both "loaded" and "unloaded" cartilage. A second zone of high collagen concentration was present at the upper layer of the deep zone of "loaded" cartilage. By contrast, this lamina of highly concentrated fibrils was lacking in "unloaded" cartilage and collagen fibrils appear thinner. Our study proves that the organization of collagen fibres is different for the "loaded" and "unloaded" regions of articular cartilage. It also suggests that this different organization may influence the MR appearance of the tissue. J. Exp. Zool. 287:346-352, 2000.

Animals↗

Inhomogeneous alginate gel spheres: an assessment of the polymer gradients by synchrotron radiation-induced X-ray emission, magnetic resonance microimaging, and mathematical modeling.

It has been previously demonstrated that calcium alginate gels prepared by dialysis often exhibit a concentration inhomogeneity being the polymer concentration considerably lower in the center of the gel than at the edges. Inhomogeneity may be a preferred structure in microcapsules due to low porosity and higher stability so that it is interesting to evaluate the polymer gradient in spherically symmetrical small alginate beads (1.0-0.7 mm diameter) obtained in different conditions. In this paper, two complementary techniques have been used to investigate this aspect. The concentration gradient of alginate has been analyzed by measuring both the spatial distribution of calcium ions in sections of alginate gel spheres, by means of x-ray fluorescence spectroscopy, and the T2 relaxation behavior on intact gel beads using magnetic resonance microimaging. The experimentally determined gradients from three-dimensional gels provide data to reevaluate the parameter estimates in the recently reported mathematical model for alginate gel formation (A. Mikkaelsen and A. Elgsaeter, Biopolymers, 1995, Vol. 36, pp. 17-41). The model may account for the gels being less inhomogeneous when nongelling sodium or magnesium ions are added during gelation.

Alginates↗

Short-TE projection reconstruction MR microscopy in the evaluation of articular cartilage thickness.

The aim of this study was to assess the potential of projection-reconstruction (PR) MR microscopy in the accurate measurement of cartilage thickness. Short-TE PR microimages were acquired at 7.05 T on bone-cartilage cylindrical plugs excised from four regions of two disarticulated femoral heads (i. e. superior, inferior, posterior and anterior), using an NMR instrument equipped with a microimaging accessory. The PR microimages were then correlated with conventional spin-echo (SE) microimages and with histology. On PR microimages, acquired with an echo time of 3.2 ms, the cartilage signal was increased, allowing an accurate delineation of the cartilage from the tidemark/cortical bone region. As a consequence, by the PR method a more precise measurement of cartilage thickness compared with that performed by the conventional SE approach was feasible. An excellent correlation between PR microimages and histology was also obtained (r = 0.90). By the proposed method it is possible to accurately determine the cartilage thickness better than with the conventional SE sequences.

Aged↗

Articular cartilage repair in rabbits by using suspensions of allogenic chondrocytes in alginate.

The feasibility of allogenic implants of chondrocytes in alginate gels was tested for the reconstruction in vivo of artificially full-thickness-damaged articular rabbit cartilage. The suspensions of chondrocytes in alginate were gelled by the addition of calcium chloride solution directly into the defects giving in situ a construct perfectly inserted and adherent to the subchondral bone and to the walls of intact cartilage. The tissue repair was controlled at 1, 2, 4 and 6 months after the implant by NMR microscopy, synchrotron radiation induced X-ray emission to map the sulfur of glycosaminoglycans and by histochemistry. Practically a complete repair of the defect was observed 4-6 months from the implant of the chondrocytes with the recovery of a normal tissue structure. Controls in which Ca-alginate alone was implanted developed only a fibrous cartilage.

Alginates↗

Structural determination of the acidic exopolysaccharide produced by a Pseudomonas sp. strain 1.15.

Pseudomonas strain 1.15 was isolated from a freshwater biofilm and shown to produce considerable amounts of an acidic polysaccharide which was investigated by methylation analysis, NMR spectroscopy and ionspray mass spectrometry (ISMS). The polysaccharide was depolymerised by a bacteriophage-associated endoglucosidase and by autohydrolysis, and the resulting oligosaccharides were investigated by NMR spectroscopy and mass spectrometry. The resulting data showed that the parent repeating unit of the 1.15 exopolysaccharide (EPS) is a branched hexasaccharide. The main chain is constituted of the trisaccharide -->4)-alpha-L-Fucp-(1-->4)-alpha-L-Fucp-(1-->3)-beta-D-Glcp- (1--> and the side chain alpha-D-Galp-(1-->4)-beta-D-GlcAp-(1-->3)-alpha-D-Galp-(1-->is linked to O-3 of the first Fuc residue. The terminal non-reducing Gal carries a 1-carboxyethylidene acetal in the R configuration at the positions 4 and 6. Of the four different O-acetyl groups present in non-stoichiometric amounts, two were established to be on O-2 of the 3-linked Gal and on O-2 of the 4-linked Fuc.

Carbohydrate Sequence↗

Sensitivity of chondrocytes of growing cartilage to reactive oxygen species.

Vascular invasion of calcified cartilage, during endochondral ossification, is initiated and sustained by invasive cells (endothelial cells and macrophages) which degrade the tissue by releasing lytic enzymes. Concurrently, reactive oxygen species (ROS) are also released by these cells and we hypothesize that ROS also contribute to the degradation of the tissue. As a preliminary approach to this problem, the antioxidant activities and the effect of ROS on hypertrophic cartilage and chondrocytes (HCs) were investigated. Compared to resting or articular chondrocytes, HCs exhibited higher catalase but lower SOD specific activities and lower PHGPx concentration, thus revealing a defence activity specific against H2O2. Moreover, dose-dependent depletion of ATP occurred after few minutes of exposure to ROS, and a long-term treatment (16 h incubation with ROS) promoted the release of LDH activity and a significant variation of the poly- to mono-unsaturated fatty acid ratio. Finally, the incubation of HCs with low ROS doses induced the release of sedimentable alkaline phosphatase activity (matrix vesicles). How the obtained results fit the in vivo occurring events is discussed.

Adenosine Triphosphate↗

Structural investigation of the exopolysaccharide produced by Pseudomonas flavescens strain B62--degradation by a fungal cellulase and isolation of the oligosaccharide repeating unit.

Pseudomonas flavescens strain B62 (NCPPB 3063) is a recently described bacterium isolated from walnut blight cankers. This strain has been designated as the type strain of a Pseudomonas rRNA group-I species. Strain B62 produced a mixture of two exopolysaccharides, differing in weight average relative molecular mass and composition. Only the most abundant exopolysaccharide (90% by mass), corresponding to the one with the lower molecular mass, was investigated by use of methylation analysis, partial acid hydrolysis, and NMR spectroscopy. The polysaccharide was depolymerised by the action of the cellulase produced by Penicillum funiculosum and the oligosaccharide obtained, corresponding to the repeating unit, was characterised by NMR spectroscopy and ion-spray mass spectrometry. The repeating unit of the B62 exopolysaccharide is [structure in text] where X is glucose (75%) or mannose (25%), and Lac is lactate. The O-acetyl groups are present only on 75% of the repeating units, and they are linked to the C6 of the hexose residues in non-stoichiometric amounts.

Carbohydrate Conformation↗

Magnetic resonance imaging of articular cartilage: ex vivo study on normal cartilage correlated with magnetic resonance microscopy.

The aims of this study were (a) to compare the MR appearance of normal articular cartilage in ex vivo MR imaging (MRI) and MR microscopy (MRM) images of disarticulated human femoral heads, (b) to evaluate by MRM the topographic variations in articular cartilage of disarticulated human femoral heads, and subsequently, (c) to compare MRM images with histology. Ten disarticulated femoral heads were examined. Magnetic resonance images were obtained using spin-echo (SE) and gradient-echo (GE) sequences. Microimages were acquired on cartilage-bone cylindrical plugs excised from four regions (superior, inferior, anterior, posterior) of one femoral head, using a modified SE sequence. Both MRI and MRM images were obtained before and after a 90 degrees rotation of the specimen, around the axis perpendicular to the examined cartilage surface. Finally, MRM images were correlated with histology. A trilaminar appearance of articular cartilage was observed with MRI and with a greater detail with MRM. A good correlation between MRI and MRM features was demonstrated. Both MRI and MRM showed a loss of the trilaminar cartilage appearance after specimen rotation, with greater evidence on MRM images. Cartilage excised from the four regions of the femoral head showed a different thickness, being thickest in the samples excised from the superior site. The MRM technique confirms the trilaminar MRI appearance of human articular cartilage, showing good correlation with histology. The loss of the trilaminar appearance of articular cartilage induced by specimen rotation suggests that this feature is partially related to the collagen-fiber orientation within the different layers. The MRM technique also shows topographic variations in thickness of human articular cartilage.

Aged↗

Correlation between biochemical composition and magnetic resonance appearance of articular cartilage.

OBJECTIVE: The objective of this study was to find a correlation between magnetic resonance (MR) appearance and biochemical composition of the normal articular cartilage by comparing the laminar aspects with the distribution of the two principal matrix components: proteoglycans and collagen. DESIGN: T2-weighted MR microimages of porcine cartilage-bone plugs, excised from both the habitually loaded and habitually unloaded regions of the proximal end of the humerus, were obtained using a spin-echo sequence. Proteoglycans (PGs) were monitored by histology and by measuring the uronate and the sulfur content of the tissue; a histologic method and the chemical determination of hydroxyproline were used for the evaluation of the collagen content. RESULTS: The 'loaded' cartilage exhibited the expected MR laminar appearance whereas the 'unloaded' tissue appeared to be more homogeneous. The PG content in the 'loaded' cartilage, was found to be 2.4 times higher than in the habitually unloaded tissue, exhibiting an increasing trend from the articular surface to the bone. In the 'unloaded' cartilage the uronate distribution was more uniform with a higher concentration in the intermediate zone. The mean collagen content of both cartilage regions was found to be about 39% of the tissue dry weight. Histology and hydroxyproline distribution pattern showed that collagen was particularly concentrated at the surface and in a central zone of the 'loaded' cartilage whereas in the 'unloaded' tissue collagen was evident only at the surface. In accordance with the collagen distribution, transverse relaxation (T2) times in 'loaded' cartilage showed a minimum value at the articular surface and another minimum in a central region. On the contrary, the average T2 value of the 'unloaded' tissue was high at the surface and decreased rapidly in the deeper zones. CONCLUSION: These results demonstrate that the MR appearance of articular cartilage correlates with the collagen content, but not with that of PGs, of the different zones. Other matrix components might, however, influence the MR appearance by contributing to the macromolecular organization of the tissue.

Animals↗

Organic solvent systems for 31P nuclear magnetic resonance analysis of lecithin phospholipids: applications to two-dimensional gradient-enhanced 1H-detected heteronuclear multiple quantum coherence experiments.

31P NMR of lipid extracts is a reproducible, rapid, and nondegradative method for qualitative and quantitative analyses of phospholipid mixtures. This analysis, however, is hampered by the instability of the solvent system commonly used for NMR spectroscopy (CHCl3/ CH3OH/H2O-EDTA). In this work we have investigated the effects of several monophasic solvent mixtures to overcome this disadvantage. Among these mixtures we have selected a solution of triethylamine, dimethylformamide, and guanidinium chloride (Et3N/DMF-GH+) as the most efficient system. In this solvent the chemical shift dispersion of the 31P signals is about four times the frequency range observed in the standard chloroform-methanol-water system. Moreover, the stability of this solvent, as a monophasic system, allows easy reproducibility of the analysis. The use of two-dimensional 1H-31P gradient-enhanced heteronuclear multiple quantum coherence experiments can further exploit the higher resolution of the signals obtained with this solvent system for the structure elucidation of known and unidentified phospholipids.

Acetamides↗

A method for generating magnetic resonance microimaging T2 maps with low sensitivity to diffusion.

Generating T2 maps in magnetic resonance microimaging is often complicated by the self-diffusion of water molecules. A modification of the standard spin-echo pulse sequence is proposed which minimizes this effect. Experiments with doped water confirmed that the T2 values obtained with the modified sequence were equal within the experimental error to the value obtained by the spectroscopic Carr-Purcell-Meiboom-Gill method. The applicability of the technique is demonstrated by generating T2 maps of porcine articular cartilage.

Animals↗

Investigation of laminar appearance of articular cartilage by means of magnetic resonance microscopy.

Magnetic resonance (MR) images and relaxation and diffusion maps of articular cartilage were obtained to explain discrepancies in its MR appearance. Porcine specimens were studied only by MR microscopy. For human specimens a combination of MR microscopy and large-scale MR imaging was used. Common features in the laminar structures of human and porcine samples are described. It was found that the decay of transverse magnetization was nonexponential with a rapidly decaying component which prevented construction of reliable proton-density maps. Dependence of T2 values on the orientation of specimens in the magnetic field as well as magnetization transfer experiments supported the previous suggestions about a significant role of dipolar interaction with protons of collagen in the laminar appearance of articular cartilage. The loss of the laminar structure induced by rotation of the human cartilage specimen around the axis normal to its surface demonstrated nonuniform angular distribution of the collagen fibers within the layer.

Animals↗

Detection and quantitation of phosphorus metabolites in crude tissue extracts by 1H and 31P NMR: use of gradient assisted 1H-31P HMQC experiments, with selective pulses, for the assignment of less abundant metabolites.

The analysis of crude tissue extracts by NMR has proven to be of use in the study of metabolism due to the non-destructive and non-selective character of the technique. Lists of 1H and 31P NMR assignments of phosphorus metabolites in water solution at specified pH and ionic composition are of large general value but their usefulness may be limited when analysing complex mixtures of metabolites at low concentrations. In this work we report on the use of gradient-assisted proton detected multiple quantum 1H and 31P coherence experiments with selective pulses for the rapid and unambiguous assignments of some crowded regions in 1H and 31P spectra of crude extracts from rat liver. The amplitudes of the gradient episodes were calibrated to optimize the coherence transfer pathway between proton and phosphorus, and the delay for the evolution of the long-range coupling was calculated from values of 3JPH and 4JPH ranging from 1.4 to 7.5 Hz. Moreover, a selective 90 degrees Gaussian pulse on the 31P channel was introduced to increase the resolution in the F1-domain and make the method even faster. The procedure was then applied to unambiguously assign the ID 31P and 1H spectra of perchloric acid extracts of rat livers that had been stimulated with phenylephrine, dBcAMP and glucagon and thus detect changes in the concentration of less abundant metabolites such as phosphoenolpyruvate, UDP-glucose and AMP. The fact that the quantification of these metabolites by either 31P and 1H methods lead to different results is discussed, and the use of 1H NMR spectroscopy for the quantification of phosphorus metabolites whose signal are too weak or poorly resolved in a 31P spectrum is proposed.

Adenosine Monophosphate↗

NMR analysis of succinoglycans from different microbial sources: partial assignment of their 1H and 13C NMR spectra and location of the succinate and the acetate groups.

In order to obtain information on the location of succinate and acetate groups, comparative NMR analyses were carried out on succinoglycans from different microbial sources by using conventional and advanced NMR techniques. In particular, one-dimensional, 1H and 13C NMR spectra were recorded for qualitative and quantitative analysis on native high-molecular-weight succinoglycans (both in the Na+ salt and free-acid forms) from Pseudomonas sp. NCIB 11592, Agrobacterium radiobacter A201-25, Rhizobium meliloti YE-2, and Rhizobium sp. isolated from Vicia faba and compared with those of the deacylated and deacylated-depyruvated, partially depolymerised exopolysaccharides from Rhizobium meliloti YE-2. Moreover, a series of two-dimensional experiments was performed on all the exopolysaccharides aiming at the partial assignment of the NMR spectra. The NMR data showed that succinate is located on O-6 of either one or both of the two side chain 3-linked beta-D-Glc residues, whereas the acetate (when it is present) is located on one of the O-6 of backbone 4-linked beta-D-Glc units, but the specific site could not be determined. In addition, the spectral features of the succinate substituent were found to be sensitive to pH changes.

Acetates↗