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Biomedical subjects

A Scipioni

Publications and source records attributed to A Scipioni.

14 recordsLinked to original sources
PubMed1995

[Pancreatic assessment by magnetic resonance imaging: an improvement in the diagnostic results with new study technics].

Magnetic resonance imaging of the pancreas has been, limited by a series of artifacts with a resulting poor contrast to noise ratio. Nevertheless, technological progress has allowed to reduce not only scanning time but also the number of artifacts, by increasing the number of excitations and matrix size. Moreover, tissue contrast can now be modified. In our study performed on 5 normal volunteers and 20 patients with different pancreatic diseases conditions, fast SE sequences with and without fat suppression were used, with an overall increase in contrast to noise ratio. In all patients MR images allowed the accurate definition of the lesions: in 8 adenocarcinoma patients the lesion could be depicted, including the 2 lesions CT had poorly demonstrated. Also in the 3 patients with endocrine tumors, MRI depicted small tumors which were later confirmed at surgery. This new protocol makes MRI a very sensitive and accurate tool in the study of neoplastic and inflammatory pancreatic diseases thus, MRI is not only a complementary tool to CT but an even better study technique. In particular, its higher contrast to noise ratio allows a dramatic improvement in the depiction of small solid lesions, especially those not altering pancreatic outline. This study proves that MRI, when adequately performed, is a very accurate tool to study, in a very short time, the pancreas and peripancreatic region, yielding much better results than all the other diagnostic imaging modalities.

Acute Disease↗
PubMed1995

[Assessment of renal function using low doses of paramagnetic contrast media].

Dynamic MR techniques with Gd-DTPA bolus administration can be used to study renal perfusion and function. In previous studies, the concentration of Gd-DTPA injected was never lower than 0.1 mmol/kg: as a result, depending on the magnetic susceptibility effect, renal signal intensity reduced in the early phases, right after contrast agent injection. To prevent signal intensity from reducing in the early phases, in our study we used a concentration of 0.05 mmol/kg. Qualitative and quantitative evaluations were performed. Seven healthy subjects and 14 patients with different degrees of renal insufficiency were enrolled in the study. All exams were performed using an 0.5-T magnet (Philips Gyroscan T5, II), with 15 mT/m gradient power. Signal intensity measurements at the cortical, external medullary and internal medullary levels, allowed the drawing of curves typical of each degree of renal insufficiency which correlated well with nuclear medicine (scintigraphy) findings. The qualitative evaluation provided results comparable with scintigraphic findings in all 7 normal subjects, in 3 of 4 cases of moderate renal insufficiency, in all 7 cases of moderate/severe renal insufficiency and in the only case of severe renal insufficiency. To conclude, this trial demonstrates the feasibility of MR studies of renal function, which provide morphological and functional pieces of information. Low concentration Gd-DTPA is decisive to avoid the magnetic susceptibility artifacts observed in previous studies.

Contrast Media↗
PubMed1994

The edentulous ridge expansion technique: a five-year study.

This study presents the clinical results of a surgical technique that expands a narrow ridge when its orofacial width precludes the placement of dental implants. In 170 people, 329 implants were placed in sites needing ridge enlargement using the endentulous ridge expansion procedure. This technique involves a partial-thickness flap, crestal and vertical intraosseous incisions into the ridge, and buccal displacement of the buccal cortical plate, including a portion of the underiying spongiosa. Implants were placed in the expanded ridge and allowed to heal for 4 to 5 months. When indicated, the implants were exposed during a second-stage surgery to allow visualization of the implant site. Occlusal loading was applied during the following 3 to 5 months by provisional prostheses. The final phase was the placement of the permanent prostheses. The results yielded a success rate of 98.8%.

Aluminum Oxide↗
PubMed1992

Theoretical prediction of the gel electrophoretic retardation changes due to point mutations in a tract of SV40 DNA.

The changes of gel electrophoretic retardation due to single base substitutions in a 173 bp fragment of Sv40 DNA were predicted by using a theoretical model based on conformational energy calculations. As described in previous papers, this model allows successful prediction of the gel electrophoretic retardation of synthetic as well as natural DNAs reported in literature. The experimental retardations related to 195 point-mutated DNAs were reproduced with a standard deviation of 0.05 comparable with the experimental one of 0.04. This result, which represents a very critical test for the proposed model, indicates that DNA superstructures can be satisfactorily predicted on the simple physical basis of the integration of the nearest-neighbour perturbations in the dinucleotide steps. Thus, cooperative effects appear, in the majority of cases investigated, to play a second order role.

Base Sequence↗
PubMed1991

[Use of the stereo-microscope in endodontic surgery].

The authors present several significant photographs of the apical anatomy of a tooth made using a stereo-microscope in the course of surgery. The authors generally use the stereo-microscope from the time of preparation of the apex to the retrograde filling. One of the changes which the authors have brought to traditional surgical procedures, the use of endodontic cement to improve the amalgam seal is illustrated. It consists of a modification which they introduced into their practice more than six years ago and even though it may be a simple clinical technique to use, it assured a significant long-term improvement in the cases treated.

Apicoectomy↗
PubMed1990

Validity of the nearest-neighbor approximation in the evaluation of the electrophoretic manifestations of DNA curvature.

The validity of a theoretical nearest-neighbor model based on conformational energy calculations, for translating the deterministic fluctuations of DNA base sequences in superstructural elements, is tested on the electrophoretic data of 450 multimeric, duplex oligonucleotides with different sequence, periodicity, and complexity, corresponding to all the experimental data so far published. An accurate semiempirical linear relation between the gel electrophoretic retardation and the dispersion of the theoretical curvature was found which allows a prediction of electrophoretic anomalies of DNA tracts, e.g., the cyclic permutation gel assays, with great confidence. Such a pattern of agreement allows the interpretation of the gel electrophoresis retardation as due to an increase of activation energy required in straightening the DNA axis.

DNA↗
PubMed1989

Structure and stability of the Boc(D-Pro-L-Pro)2OCH3 Na+ complex: a model of poly(D,L-proline), an alkali ion channel across membranes.

In order to elucidate the molecular mechanisms of alkali ions conduction of poly(D,L-proline), which shows the typical behavior of an ion channel across membranes, conformations of the tetrameric derivative Boc(D-Pro-L-Pro)2OCH3 in solution, in the presence of the Na+ ion, were investigated by CD and nmr spectroscopy. Both theoretical and experimental data indicate the formation in solution of a monomeric complex between the tetramer, in the all-trans conformation, and the cation. The results allow to confirm the channel model, previously proposed on the phenomenological behavior of poly(D,L-proline) in membranes.

Hydrogen-Ion Concentration↗
PubMed1988

A theoretical model of DNA curvature.

Distortions from the uniform idealized B-DNA structure are investigated in terms of differential interactions between adjacent nucleotide pairs on the basis of conformational energy calculations. A theoretical model of DNA curvature is proposed based on the evaluation of the curvature vector defined in the complex plane and the corresponding variance. The model appears to contain the basic physical features for translating the deterministic fluctuations of DNA sequences in superstructure elements. It allows the quantitative reproduction of all the available gel electrophoresis experiments on both periodical polynucleotides and tracts of DNAs as well as the theoretical prediction of the sequence dependent DNA writhing in good agreement with the experimental data. The general pattern of agreement between the theoretical and experimental data and the biological significance of the results obtained allow an extensive application of the model for the screening of DNA regions which are possible candidates for protein recognition.

DNA↗
PubMed1986

DNA topology in a chromatin model system.

The synthetic copolypeptide (Lys33, Leu67)100-Orn20, modeled on some general features of the histone sequences, has been found to supercoil the DNA double helix, wrapping it into a micelle, as a result of cohesive interactions between the polypeptide hydrophobic moieties. X-ray low-angle diffraction of complexes between the polypeptide and DNA is characterized by maxima at 50, 32, and 23 A, reminiscent of the chromatin pattern. The existence of a nucleosome-like structure along the DNA is suggested by gel electrophoresis analysis of DNA fragments after micrococcal nuclease digestion, showing the presence of a fragment of about 100 basepairs (bp) long. Topological experiments on the complexes with supercoiled as well as relaxed circular DNA by two-dimensional gel electrophoresis show the presence of left-handed superhelical turns. The results are in agreement with an intrinsic propensity of B-DNA to writhe into left-handed supercoils.

Animals↗
PubMed1985

Poly(DL-proline), a synthetic polypeptide behaving as an ion channel across bilayer membranes.

The synthesis and characterization of poly(DL-proline) are reported in relation with its predicted property of forming ion channels across membranes. The analysis of the conductance induced in synthetic bilayer membranes doped with poly(DL-proline) shows ionic permeoselectivity and the characteristic time course of fluctuations of ion channels, according to the similarity with the active structure of gramicidin A in membranes during the ion passage. An alternative mechanism of ion transport across bilayer membranes is also advanced.

Electric Conductivity↗
PubMedDate not supplied

[Phlebography with MR in the study of deep venous thrombosis].

MR phlebography was recently proposed as a possible alternative to contrast venography in the detection of deep venous thrombosis. We focused our work on the study of the pelvic veins since it is at this level that contrast venography and the other noninvasive techniques, i.e., phlebography, impedance plethysmography and US, exhibit their major limitations. Thirty patients underwent MR phlebography: 13 of them had a diagnosis of DVT of the pelvic venous district and the other 17 had negative results for this condition. All the patients were also examined with color-Doppler US at the pelvis and legs. In all the patients submitted to MR phlebography, thrombosis site and presence were demonstrated, with diagnostic information also on its extent and adhesion to vein wall. To conclude, MR phlebography can provide contrast venography-like images in a noninvasive way, with high accuracy (100% sensitivity and 90% specificity) especially in the pelvic district where the limitations of other techniques are more apparent. Larger series of patients must be studied to assess the actual role of MR phlebography in the patients with DVT or at high risk for this condition.

Femoral Vein↗