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Biomedical subjects

A Scipioni

Publications and source records attributed to A Scipioni.

At least 19 recordsLinked to original sources
PubMed2005

Proteomic analysis of human thyroid cell lines reveals reduced nuclear localization of Mn-SOD in poorly differentiated thyroid cancer cells.

Differential protein arrays between nuclear extracts of human thyroid cell lines obtained from tumors with different degree of differentiation were exploited to define molecular alterations occurring during thyroid tumor progression. Nuclear extracts from the well differentiated TPC-1 (from papillary carcinoma) and the poorly differentiated ARO (from anaplastic carcinoma) cells showed an overall similar pattern of protein expression as revealed by two-dimensional gel electrophoresis analysis. However, manganese-superoxide dismutase (Mn-SOD) was clearly identified by mass spectrometry procedures as significantly less expressed in ARO compared to TPC-1 cells. A reduced expression of Mn-SOD in the nuclear compartment was confirmed by Western blot and immunofluorescence analysis. A similar expression pattern of nuclear Mn-SOD was detected by immunohistochemistry in human thyroid tumors, with the lowest or absent detection in anaplastic carcinomas. Moreover, the levels of nuclear Mn-SOD in tumor cells were lower than in the normal thyrocytes. These data indicate that an altered nuclear expression of Mn-SOD parallels, together with changes in other elements of the antioxidant protective system, the loss of differentiation occurring during the progression of thyroid tumors.

Adenocarcinoma, Follicular↗
PubMed2002

From the sequence to the superstructural properties of DNAs.

A theoretical model for predicting intrinsic and induced DNA superstructures as well as their thermodynamic properties is presented. Intrinsic sequence-dependent superstructures are evaluated by integrating local deviations from the canonical B-DNA of the different dinucleotide steps. Induced superstructures are obtained by adopting the principle of minimum deformation free energy, evaluated in the Fourier space, in the framework of first-order elasticity. Finally dinucleotide stacking energies and melting temperatures are considered to account for local flexibility. In fact the two scales are strongly correlated. The model works very satisfactorily in predicting the sequence-dependent effects on the DNA experimental behavior, such as the gel electrophoresis retardation, the writhe transitions in topologically constrained domains, the thermodynamic constants of circularization reactions as well as the nucleosome thermodynamic stability constants.

Algorithms↗
PubMed2001

Mapping the intrinsic curvature and flexibility along the DNA chain.

The energy of DNA deformation plays a crucial and active role in its packaging and its function in the cell. Considerable effort has gone into developing methodologies capable of evaluating the local sequence-directed curvature and flexibility of a DNA chain. These studies thus far have focused on DNA constructs expressly tailored either with anomalous flexibility or curvature tracts. Here we demonstrate that these two structural properties can be mapped also along the chain of a "natural" DNA with any sequence on the basis of its scanning force microscope (SFM) images. To know the orientation of the sequence of the investigated DNA molecules in their SFM images, we prepared a palindromic dimer of the long DNA molecule under study. The palindromic symmetry also acted as an internal gauge of the statistical significance of the analysis carried out on the SFM images of the dimer molecules. It was found that although the curvature modulus is not efficient in separating static and dynamic contributions to the curvature of the population of molecules, the curvature taken with its direction (its sign in two dimensions) permits the direct separation of the intrinsic curvature from the flexibility contributions. The sequence-dependent flexibility seems to vary monotonically with the chain's intrinsic curvature; the chain rigidity was found to modulate as its local thermodynamic stability and does not correlate with the dinucleotide chain rigidities evaluation made from x-ray data by other authors.

DNA, Bacterial↗
PubMed2001

Identification of protein domains on topological basis.

A theoretical method is proposed to identify structural domains in proteins of known structures. It is based on the distribution of the local axes of the polypeptide chain. In particular, a statistical analysis is applied to the contributions of the local axes to the absolute writhing number, a topological property of a space curve resulting from the number of self-crossings in the curve projections onto a unit sphere. This finding supports the hypothesis that topological requirements should be satisfied in the process of protein folding and in the final organization of the tertiary structures.

Databases, Factual↗
PubMed2000

A theoretical model for the prediction of sequence-dependent nucleosome thermodynamic stability.

A theoretical model for predicting nucleosome thermodynamic stability in terms of DNA sequence is advanced. The model is based on a statistical mechanical approach, which allows the calculation of the canonical ensemble free energy involved in the competitive nucleosome reconstitution. It is based on the hypothesis that nucleosome stability mainly depends on the bending and twisting elastic energy to transform the DNA intrinsic superstructure into the nucleosomal structure. The ensemble average free energy is calculated starting from the intrinsic curvature, obtained by integrating the dinucleotide step deviations from the canonical B-DNA and expressed in terms of a Fourier series, in the framework of first-order elasticity. The sequence-dependent DNA flexibility is evaluated from the differential double helix thermodynamic stability. A large number of free-energy experimental data, obtained in different laboratories by competitive nucleosome reconstitution assays, are successfully compared to the theoretical results. They support the hypothesis that the stacking energies are the major factor in DNA rigidity and could be a measure of DNA stiffness. A dual role of DNA intrinsic curvature and flexibility emerges in the determination of nucleosome stability. The difference between the experimental and theoretical (elastic) nucleosome-reconstitution free energy for the whole pool of investigated DNAs suggests a significant role for the curvature-dependent DNA hydration and counterion interactions, which appear to destabilize nucleosomes in highly curved DNAs. This model represents an attempt to clarify the main features of the nucleosome thermodynamic stability in terms of physical-chemical parameters and suggests that in molecular systems with a large degree of complexity, the average molecular properties dominate over the local features, as in a statistical ensemble.

Base Sequence↗
PubMed2000

Peripheral arterial embolism. Report of hospitalized cases.

OBJECTIVE: We analyzed the frequency of peripheral embolisms, the underlying heart disease,triggering factors, the sites of the emboli, and evolution of the patients. METHODS: We analyzed 29 cases of peripheral arterial embolism out of a total of 20,211 hospitalizations in a cardiology center in the city of São Paulo. The age was 51.89+/-18.66 years, and 15 were males. RESULTS: Embolism in the right lower limb occurred in 18 patients (62.0%),in the left lower 11(37.9%) and right upper 3 (10.3%) limbs, and in the left arm (1). Four patients had embolism in two limbs. The heart disease, mitral valvar heart disease (9 patients - 31.0%); infective endocarditis (7- 24.1%); dilated cardiomyopathy (6 - 20.6%); ischemic coronary heart disease (6 patients - 20.6%); and one patient with cor pulmonale. Atrial fibrillation was observed in 20 patients (68.9%), chronic in 12 patients (41.3% ) and acute in 8 (27. 5%). All patients with mitral valvar heart disease had atrial fibrillation, chronic in 8 patients (88.8%); patients with cardiomyopathy and coronary heart disease, 4 in each group had atrial fibrillation, acute in 60% of the patients. Patients with infective endocarditis, 3 had staphylococcus and 2 Gram-negative bacteria. In the follow-up, 2 patients (6.8%) required limbs amputation, and 5 (17.2%) died due to embolism. CONCLUSION: Most of the time, embolism does not cause permanent complications. Our data highlight the importance of anticoagulation for patients acute atrial fibrillation in myocardial dysfunction and for patients with chronic atrial fibrillation in cases of mitral valvar heart disease to prevent peripheral embolism.

Adolescent↗
PubMed1999

Dual role of DNA intrinsic curvature and flexibility in determining nucleosome stability.

A statistical mechanistic approach to evaluate the sequence-dependent thermodynamic stability of nucleosomes is proposed. The model is based on the calculation of the DNA intrinsic curvature, obtained by integrating the nucleotide step deviations from the canonical B-DNA structure, and on the evaluation of the first order elastic distortion energy to reach the nucleosomal superstructure. Literature data on the free energy of nucleosome formation as obtained by competitive nucleosome reconstitution of a significant pool of different DNA sequences were compared with the theoretical results, and a satisfactorily good correlation was found. A striking result of the comparison is the emergence of two opposite roles of the DNA intrinsic curvature and flexibility in determining nucleosome stability. Finally, the obtained results suggest that the curvature-dependent DNA hydration should play a relevant role in the sequence-dependent nucleosome stability.

Base Sequence↗
PubMed1999

MR pyelography and conventional MR imaging in urinary tract obstruction.

PURPOSE: To evaluate the possible role of MR imaging in the assessment of patients with urinary tract obstruction by combining conventional MR imaging and MR pyelography (MRP). MATERIAL AND METHODS: Forty-three patients with dilated upper urinary tract were studied with a high gradient strength 0.5 T magnet. Respiratory compensated T1-weighted, SE and T2-weighted TSE sequences were acquired in all patients. MRP images were obtained by using a respiratory compensated 3D T2-weighted TSE sequence. MRP images were reconstructed with a MIP algorithm. In all cases, urography and/or ascending pyelography were also performed. Images were independently evaluated by two radiologists. RESULTS: The dilated tract ureter and the level of the obstruction could be correctly demonstrated in all cases. The cause of the obstruction was correctly demonstrated by examiner 1 in 90% and by examiner 2 in 88%. The interobserver agreement was high with a kappa-value of 0.96. CONCLUSION: In cases of obstructive hydroureteronephrosis MR imaging, combining MRP and conventional sequences, can be proposed as an accurate technique in the assessment of level and cause of obstruction.

Aged↗
PubMed1999

Bone regeneration in the edentulous ridge expansion technique: histologic and ultrastructural study of 20 clinical cases.

The edentulous ridge expansion (ERE) technique is a partial-thickness flap procedure for implant surgery that was developed in 1986. The ERE technique permits the use of osseointegrated implants at sites whose minimal orofacial dimensions are insufficient for traditional implant surgery. The present work is a histologic and ultrastructural study of hard tissue repair modalities at edentulous sites that were treated with the ERE technique in 20 humans. Biopsies were obtained from the tissue regenerating within the surgically created bone gap between the mobile buccal and nonmobile lingual or palatal bone-periosteum plates ("bone flaps") on days 40, 90, 120, 150, and 480 (day 0 = day of implant insertion). The results suggest that osteoblasts differentiate from preexisting mesenchymal cells located on the original fissure walls, with consequent deposition of new bone in the surgically created intrabony defect.

Adult↗
PubMed1998

Pancreatic adenocarcinoma: combination of MR imaging, MR angiography and MR cholangiopancreatography for the diagnosis and assessment of resectability.

The purpose of this study was to determine the possibility of integrating MR cholangiopancreatography (MRCP) and MR angiography (MRA) to conventional MR images in the diagnosis and assessment of resectability of pancreatic adenocarcinoma. Twenty-three patients with pancreatic adenocarcinoma were prospectively examined with MR. Conventional MR images were acquired in all patients. Three-dimensional MRCP and MRA images were acquired in all patients with suspected biliary and vascular involvement. Acquisition time was less than 45 min in all cases. Images were independently evaluated by two radiologists, with final reading decided by consensus among readers. Diagnosis was confirmed with surgery in 16 patients and with percutaneous biopsy in 7. Concordance among readers was high with a kappa value of 0.83. Pancreatic adenocarcinoma was observed in all patients. Correct assessment of unresectability due to vascular involvement was found in 22 of 23 patients. Biliary obstruction was evident in 13 patients, involving the biliary and pancreatic ducts in 9 and the biliary ducts only in 4. Technical advances permit extensive use of MRI in the evaluation of abdominal pathologies. The combination of MR imaging, MRCP, and MRA can provide sufficient information for the diagnosis and assessment of resectability of pancreatic adenocarcinoma, which otherwise would require three different exams.

Adenocarcinoma↗
PubMed1997

Role of MR venography in the evaluation of deep venous thrombosis.

PURPOSE: MR venography has been recommended for the evaluation of deep venous thrombosis. The purpose of our study was to determine the role of MR venography, in particular at the level of the pelvis where other diagnostic modalities show major limitations. MATERIALS AND METHODS: Forty-three patients with clinical suspicion of deep venous thrombosis were examined by means of pelvic MR venography. In all cases, a 2D-TOF sequence was used with cranial arterial presaturation. In selected cases, i.e. when a small intraluminal filling defect was present, a cine-PC sequence was used in addition in order to exclude the presence of a pulsatility artifact as causing the filling defect. In all cases, contrast venography was also performed and considered to be the standard of reference. RESULTS: MR venography showed 26 patients to be positive for deep venous thrombosis at the pelvic level. These positive results were correct in 25 cases. The analysis of the results provided values of sensitivity and specificity of respectively 100% and 94%, with an overall accuracy of 97.6%. CONCLUSIONS: Our results indicate that MR can provide highly accurate images, similar to those of contrast venography, in a noninvasive fashion. It is particularly useful in the pelvic region where the limitations of other imaging modalities are more evident.

Contrast Media↗
PubMed1997

Healing at implants with and without primary bone contact. An experimental study in dogs.

The aim of the present investigation in the dog was to study: (i) if it was possible by the use of EREt to predictably expand the compromised alveolar ridge; (ii) if proper osseointegration also occurred at sites where the implant following installation was devoid of direct bone contact. 5 beagle dogs, about 1-year old, were included in the study. During a preparatory period, the mandibular premolars were extracted and the ridge in the edentulous regions markedly reduced. After 3 months of healing, ridge expansion surgery was performed. A partial thickness flap was raised on the buccal and lingual surfaces for the soft tissue preparation. The buccal part of the ridge was mobilised and the bone plate with its periosteum displaced in the buccal direction. In each quadrant, 2 fixture sites were prepared in the mandibular bone apical of the displaced bone plate. 2 unthreaded titanium plasma sprayed fixtures were installed in such a way that the coronal border of the fixture was flush with the level of the lingual and buccal bone plate. The "internal" distance between the mobile buccal and the non-mobile lingual bone plates was identical to the diameter of the fixtures, i.e., 3.3 mm, while the distance between the mesial and distal borders of the 2 implants and the mesial or distal bone was > 5 mm. In each quadrant, 1 additional fixture was installed in the non- reduced mesial part of the alveolar ridge (control site). 3 months after fixture installation, abutment connection was performed. Following abutment connection, a plaque control program was initiated and maintained for 4 months, at which time, the dogs were re-examined and biopsies obtained for histological examination. It was observed that bone regeneration and osseointegration may occur to titanium fixtures placed in surgically-created bone defects. The amount of bone that was in intimate contact with the fixture surface was similar in test and control sites. In addition, the periimplant mucosa at test and control implants had similar dimensions and composition in terms of junctional epithelium and connective tissue.

Alveolar Ridge Augmentation↗
PubMed1997

[Combined conventional magnetic resonance, magnetic resonance angiography, and magnetic resonance cholangiopancreatography in the diagnosis and staging of pancreatic carcinoma].

PURPOSE: This study was aimed to integrating MR CholangioPancreatography (MRCP) and MR Angiography (MRA) to conventional MR images in the diagnosis and resectability assessment of pancreatic adenocarcinoma. MATERIAL AND METHODS: Twenty-three consecutive patients with pancreatic adenocarcinoma (16 in the head and 7 in the body-tail region) were examined with MR. Conventional MR, 3D MRCP and venous and arterial MRA images were acquired to assess biliary and vascular involvement. Acquisition time never exceeded 40-45 minutes. The images were independently studied by two radiologists and the final reading was decided upon consensus among readers. Sixteen patients underwent surgery. RESULTS: The diagnosis was confirmed at surgery in 16 patients and at percutaneous biopsy in 7. Interreader agreement was considered high, with .83 interobserver variability. Pancreatic adenocarcinoma was found in all patients examined. Unresectability because of vascular involvement was correctly assessed in all patients but 1. Biliary obstruction was demonstrated in 13 patients, involving the biliary and pancreatic ducts in 9 and the biliary ducts only in 4. CONCLUSION: Technical advances now permit the extensive application of MRI to the study of abdominal conditions. The combination of MRI, MRCP and MRA can provide most of the information needed for the diagnosis and resectability assessment of pancreatic adenocarcinoma, which can otherwise be obtained only performing three different exams.

Adenocarcinoma↗
PubMed1996

MR cholangiopancreatography (MRCP) at 0.5 T: technique optimisation and preliminary results.

The aim of our study was to evaluate the feasibility of MR cholangiopancreatography (MRCP) at 0.5 T. To our knowledge no previous studies of MRCP have been performed at mid-field strength. Thirty-one patients with dilated biliary systems were examined with three-dimensional MRCP. All patients were studied with a 0.5 T superconducting magnet. A three-dimensional turbo spin-echo (TSE) sequence was acquired (TR = 5000 ms, TE = 244 ms, echo train length = 45; acquisition time = 14 min 10 s). Coronal images were post-processed with the MIP algorithm. Recently, the parameters have been optimised (TR = 3000 ms, TE = 700 ms, echo train length = 128), reducing the acquisition time to 3 min. Endoscopic retrograde cholangiopancreatography (ERCP) was performed in 26 cases; 5 patients underwent percutaneous transhepatic cholangiography PTC. MRCP and ERCP images were evaluated by an experienced radiologist and an endoscopist. MRCP of diagnostic quality was acquired in all patients. Choledocholithiasis was correctly evaluated by MRCP in 12 of 12 patients, compared with 11 correct diagnoses by ERCP. The presence and the level of the stricture were accurately shown in 16 of 16 patients with MRCP and in 13 of 16 patients with ERCP. The peripheral biliary tree above the obstruction and pancreatic duct were better evaluated by MRCP in all cases. In 3 of 3 patients who had undergone bilio-enteric surgery, a correct evaluation of the site of the anastomosis was possible with MRCP. It is concluded that MRCP performed at mid-field strength allows good visualisation of the dilated biliary system. Excellent results have been obtained on comparison with ERCP. MRCP performed at mid-field strength could have the same clinical value as high field strength MRCP.

Adult↗
PubMed1996

[Magnetic resonance pyelography: optimization of the technic and the preliminary results].

Magnetic resonance pyelography (MRP) is a new noninvasive method which demonstrates dilated urinary tracts with no need of contrast agent injection. This study was aimed at technique optimization, using new fast sequences with high intrinsic contrast, to demonstrate the urinary tract in obstructive uropathy patients. Twelve consecutive patients and 4 healthy volunteers were included in this prospective study; all the exams were performed with a high gradient power 0.5-T unit using T2- weighted turbo SE sequences, acquired three-dimensionally on the coronal plane. Obstructive uropathy was caused in 9 patients by neoplastic lesions, in 2 by postoperative strictures and in 1 by inflammatory tissue. In all patients MRP depicted the dilated urinary tract optimally, with good morphological detailing and the accurate assessment of both level and cause of obstruction. In the healthy volunteers, the absence of dilatation did not permit the complete visualization of the urinary tract. To conclude, MRP is a new technique which permits high-quality imaging of the urinary tract. Further studies are needed to assess its actual potentials and clinical role.

Adult↗
PubMed1996

[Flow quantification with magnetic resonance: preliminary results with phase contrast technique].

This study investigated the accuracy of phase contrast MRI in blood flow measurements; both in vitro and in vivo studies were carried out. Five normal volunteers (3 women and 2 men, age range: 24 to 30 years) were examined with MR angiography (MRA) and a flow measurement sequence. A 2D phase contrast sequence, with retrospective cardiac gating was also acquired with the following imaging parameters: TR/TE/FA (26/9.3/20 degrees ), field of view 150 mm, matrix 96 x 128; 4 averages. VENC value (cm/s) was chosen according to the examined region. The total acquisition time ranged 3 min 25 sec to 4 min 38 sec. The sequences were acquired on a plane perpendicular to the vessel direction, using MIP-reconstructed MRA images as a scout view. The results are the same as those obtained with other techniques, in the common carotid artery (Vmax = 70.7 cm/s; Vmin = 18.8 cm/sec; flow = 348 ml/min), internal carotid artery (Vmax -54.4 cm/sec; Vmin = 18 cm/sec; flow = 236 ml/min) and vertebral artery (Vmax = 51.7 cm/sec; Vmin = 17.5 cm/sec). The resistance index could always be calculated and exceeded 0.7 in all cases. In conclusion, MRA is an accurate technique for blood flow measurements, in particular with cardiac gating, which permits measurement optimization according to the different cardiac cycles.

Adult↗
PubMed1996

[Biliary-enteric anastomosis: role of cholangiography with magnetic resonance].

Our study was aimed at investigating the role of MR-cholangiography (MRC) in the examination of patients treated with biliary-enteric anastomosis. MRC was performed in 15 patients (8 men and 7 women, mean age: 64.7 years) operated on for biliary-enteric anastomoses (13 hepaticojejunostomies and 2 choledochoduodenostomies) whose symptoms were as follows: persistent jaundice in 4 patients; cholangitis and abnormal liver function tests in 2 patients; associated transient jaundice, epigastric pain, abnormal liver function tests in 2 patients. The remaining 7 patients were asymptomatic and examined during their follow-up. MRC was performed with a non-breath-hold, fat-suppressed 3D turbo spin echo sequence (TR = 3000 msec, TE = 700 msec, ETL = 128) with an acquisition time ranging 4 min 24 sec to 5 min 48 sec. Six patients were subsequently submitted to Percutaneous Transhepatic Cholangiography (PTC) to confirm the diagnosis and to perform a therapeutical procedure. Two patients, submitted to choledochoduodenostomy were examined with ERCP. The remaining seven patients, examined during their surgical follow-up and who presented no major symptoms or dilation of the bile ducts, were not submitted to any invasive procedure. Image quality was graded as good to fair in 12/15 cases (80%) and poor in 3/15 cases (20%). The degree of bile ducts dilation was correctly assessed with complete inter observer agreement in 8/8 patients. MRCP correctly showed: bile ducts irregularities in 2 of 4 patients with cholangitis (k = 0.59), anastomosis stenosis in 8 of 8 patients (k = 0.86), and 5-15 mm stones in 5 of 5 patients (k = 0.95). In conclusion, MRCP is a safe, noninvasive technique in the study of biliary-enteric anastomoses with high accuracy in assessing the cause of jaundice. MRCP images can be used as a guide for subsequent interventional procedures. Its main disadvantages are the lack of functional information and the high cost which limits its its use to the screening of symptomatic patients.

Aged↗