PubMed Health⌕ Search

Biomedical subjects

M Di Girolamo

Publications and source records attributed to M Di Girolamo.

At least 19 recordsLinked to original sources
PubMed2001

[MR imaging in the follow-up of ACL reconstruction: retrospective analysis of 54 patients].

PURPOSE: The authors evaluated the possible presence of lesions, in patients treated for anterior cruciate ligament (ACL) reconstruction. MATERIAL AND METHODS: MR examinations of the knee were performed in 54 patients previously surgically treated for an ACL lesion, with a patellar tendon graft. MR was performed in a period of time ranging from 10 to 36 months after surgery. The authors studied the new ligament, transosseous tunnel location, the patellar tendon, other possible articular lesions and the extent and signal of possible synovial fibrotic reaction. RESULTS: Lesions of the new ligament were found in 21 patients with the following patterns: atrophic reabsorption of the new-ACL (6 patients), and diffuse or focal alterations in morfology and signal (15 patients). In 15 patients the new ACL lesions were associated with incorrect positioning of tibial tunnels. All of the new ligament lesions diagnosed with MR were arthroscopically confirmed. In 12 patients the patellar tendon in 12 patients was involved with inflammatory-degenerative alterations. Other associated lesions were found involving menisci (18 patients), medial collateral ligament (MCL) (8 patients), osteochondral surfaces (12 patients). In patients with an intact new ACL, instability was correlated with meniscal lesions associated with MCL irregularities. In 4 patients a diffuse fibrotic synovial tissue was responsible for limited articular excursion. CONCLUSIONS: MR in post-ACL substitution has to panoramically investigate all articular compartments, with a complete evaluation of all articular lesions that can contribute to articular symptomatology in order to choose the correct therapeutic strategy.

Anterior Cruciate Ligament↗
PubMed2000

Endogenous ADP-ribosylation of the G protein beta subunit prevents the inhibition of type 1 adenylyl cyclase.

Mono-ADP-ribosylation is a post-translational modification of cellular proteins that has been implicated in the regulation of signal transduction, muscle cell differentiation, protein trafficking, and secretion. In several cell systems we have observed that the major substrate of endogenous mono-ADP-ribosylation is a 36-kDa protein. This ADP-ribosylated protein was both recognized in Western blotting experiments and selectively immunoprecipitated by a G protein beta subunit-specific polyclonal antibody, indicating that this protein is the G protein beta subunit. The ADP-ribosylation of the beta subunit was due to a plasma membrane-associated enzyme, was sensitive to treatment with hydroxylamine, and was inhibited by meta-iodobenzylguanidine, indicating that the involved enzyme is an arginine-specific mono-ADP-ribosyltransferase. By mutational analysis, the target arginine was located in position 129. The ADP-ribosylated beta subunit was also deribosylated by a cytosolic hydrolase. This ADP-ribosylation/deribosylation cycle might be an in vivo modulator of the interaction of betagamma with specific effectors. Indeed, we found that the ADP-ribosylated betagamma subunit is unable to inhibit calmodulin-stimulated type 1 adenylyl cyclase in cell membranes and that the endogenous ADP-ribosylation of the beta subunit occurs in intact Chinese hamster ovary cells, where the NAD(+) pool was labeled with [(3)H]adenine. These results show that the ADP-ribosylation of the betagamma subunit could represent a novel cellular mechanism in the regulation of G protein-mediated signal transduction.

Adenosine Diphosphate Ribose↗
PubMed1999

Role of brefeldin A-dependent ADP-ribosylation in the control of intracellular membrane transport.

The fungal toxin brefeldin A (BFA) dissociates coat proteins from Golgi membranes, causes the rapid disassembly of the Golgi complex and potently stimulates the ADP-ribosylation of two cytosolic proteins of 38 and 50 kDa. These proteins have been identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a novel guanine nucleotide binding protein (BARS-50), respectively. The role of ADP-ribosylation in mediating the effects of BFA on the structure and function of the Golgi complex was analyzed by several approaches including the use of selective pharmacological blockers of the reaction and the use of ADP-ribosylated cytosol and/or enriched preparations of the BFA-induced ADP-ribosylation substrates, GAPDH and BARS-50. A series of blockers of the BFA-dependent ADP-ribosylation reaction identified in our laboratory inhibited the effects of BFA on Golgi morphology and, with similar potency, the ADP-ribosylation of BARS-50 and GAPDH. In permeabilized RBL cells, the BFA-dependent disassembly of the Golgi complex required NAD+ and cytosol. Cytosol that had been previously ADP-ribosylated (namely, it contained ADP-ribosylated GAPDH and BARS-50), was instead sufficient to sustain the Golgi disassembly induced by BFA. Taken together, these results indicate that an ADP-ribosylation reaction is part of the mechanism of action of BFA and it might intervene in the control of the structure and function of the Golgi complex.

Adenosine Diphosphate Ribose↗
PubMed1997

Characterization of chemical inhibitors of brefeldin A-activated mono-ADP-ribosylation.

Brefeldin A, a toxin inhibitor of vesicular traffic, induces the selective mono-ADP-ribosylation of two cytosolic proteins, glyceraldehyde-3-phosphate dehydrogenase and the novel GTP-binding protein BARS-50. Here, we have used a new quantitative assay for the characterization of this reaction and the development of specific pharmacological inhibitors. Mono-ADP-ribosylation is activated by brefeldin A with an EC50 of 17.0 +/- 3.1 microg/ml, but not by biologically inactive analogs including a brefeldin A stereoisomer. Brefeldin A acts by increasing the Vmax of the reaction, whereas it does not influence the Km of the enzyme for NAD+ (154 +/- 13 microM). The enzyme is an integral membrane protein present in most tissues and is modulated by Zn2+, Cu2+, ATP (but not by other nucleotides), pH, temperature, and ionic strength. To identify inhibitors of the reaction, a large number of drugs previously tested as blockers of bacterial ADP-ribosyltransferases were screened. Two classes of molecules, one belonging to the coumarin group (dicumarol, coumermycin A1, and novobiocin) and the other to the quinone group (ilimaquinone, benzoquinone, and naphthoquinone), rather potently and specifically inhibited brefeldin A-dependent mono-ADP-ribosylation. When tested in living cells, these molecules antagonized the tubular reticular redistribution of the Golgi complex caused by brefeldin A at concentrations similar to those active in the mono-ADP-ribosylation assay in vitro, suggesting a role for mono-ADP-ribosylation in the cellular actions of brefeldin A.

Adenosine Diphosphate↗
PubMed1997

Possible role of BARS-50, a substrate of brefeldin A-dependent mono-ADP-ribosylation, in intracellular transport.

Brefeldin A (BFA), a fungal metabolite that inhibits membrane transport, potently stimulates an endogenous ADP-ribosylation reaction that selectively modifies two cytosolic proteins of 38 and 50 kDa on an amino acid residue different from those used by all known mADPRTs. The 38-kDa substrate was identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), whereas the 50-kDa substrate (BARS-50) was characterized as a novel guanine nucleotide binding protein. Thus, BARS-50 is able to bind GTP and its ADP-ribosylation is inhibited by the beta gamma subunit of GTP-binding (G) proteins. Moreover, BARS-50 was demonstrated to be a group of closely related proteins that appear to be different from all the known G proteins. A partially purified BARS-50 was obtained from rat brain cytosol, which was then used for microsequencing and in functional studies. A similar procedure led to the purification of native (non-ADP-ribosylated) BARS-50. The possible role of the BFA-dependent ADP-ribosylation and of BARS-50 in the maintenance of Golgi structure and function was addressed by examining which of the effects of BFA may be modified by inhibiting this reaction. We find that the BFA-dependent transformation of the Golgi stacks into a tubular reticular network is prevented when the BFA-dependent ADP-ribosylation activity was blocked by specific inhibitors thus indicating that BFA-dependent ADP-ribosylation of cytosolic proteins participate in the dynamic regulation of intracellular transport.

Adenosine Diphosphate Ribose↗
PubMed1997

Brefeldin A-induced ADP-ribosylation in the structure and function of the Golgi complex.

Brefeldin A (BFA) is a fungal metabolite that exerts generally inhibitory actions on membrane transport and induces the disappearance of the Golgi complex. Previously we have shown that BFA stimulates the ADP-ribosylation of two cytosolic proteins of 38 and 50 KD. The BFA-binding components mediating the BFA-sensitive ADP-ribosylation (BAR) and the effect of BFA on ARF binding to Golgi membranes have similar specificities and affinities for BFA and its analogues, suggesting that BAR may have a role in the cellular effects of BFA. To investigate this we used the approach to impair BAR activity by the use of BAR inhibitors. A series of BAR inhibitors was developed and their effects were studied in RBL cells treated with BFA. In addition to the common ADP-ribosylation inhibitors (nicotinamide and aminobenzamide), compounds belonging to the cumarin (novobiocin, cumermycin, dicumarol) class were active BAR inhibitors. All BAR inhibitors were able to prevent the BFA-induced redistribution of a Golgi marker (Helix pomatia lectin) into the endoplasmic reticulum, as assessed in immunofluorescence experiments. At the ultrastructural level, BAR inhibitors prevented the tubular-vesicular transformation of the Golgi complex caused by BFA. The potencies of these compounds in preventing the BFA effects on the Golgi complex were similar to those at which they inhibited BAR. Altogether these data support the hypothesis that BAR mediates at least some of the effects of BFA on the Golgi structure and function.

Adenosine Diphosphate Ribose↗
PubMed1997

Modulatory role of GTP-binding proteins in the endogenous ADP-ribosylation of cytosolic proteins.

The endogenous ADP-ribosylation of cytosolic proteins and the pattern of NAD degradation were analyzed in subcellular fractions of rat liver in order to investigate the modulation of these reactions by GTP-binding (G) proteins. We could show that intracellular membranes from rat liver have a guanine nucleotide- and divalent cation-dependent pyrophosphatase activity able to rapidly degrade NAD to AMP. This enzymatic activity was investigated by two different approaches: the degradation of [32P]-NAD in the presence of intracellular membranes and the mono-ADP-ribosylation of cytosolic proteins. Divalent cations, preferentially Zn2+ and Mn2+, were required for the pyrophosphatase activity, since in the presence of the Zn2+ chelator TPEN (N,N,N',N'-tetrakis(2-pyridyl-methyl)ethylenediamine) or EDTA, the NAD degradation was inhibited by about 50%. Accordingly, in the presence of TPEN the endogenous ADP-ribosylation of cytosolic proteins was enhanced, whereas Zn2+ caused a significant inhibition of this reaction. GDP beta S was able to strongly activate the mono-ADP-ribosylation of cytosolic proteins. This effect was abolished by GTP gamma S, suggesting that a G protein, or rather one of the subunits of a heterotrimeric G protein, is involved in the modulation of the pyrophosphatase and consequently, of endogenous ADP-ribosylation. We propose that a regulatory pathway involving a heterotrimeric G protein modulates enzymes affecting the NAD turnover and availability of NAD for endogenous mADPRTs.

Adenosine Diphosphate Ribose↗
PubMed1997

The efflux of lysine from the basolateral membrane of human cultured intestinal cells (Caco-2) occurs by different mechanisms depending on the extracellular availability of amino acids.

The efflux of the nutritionally essential amino acid, L-lysine from the basolateral (BL) membrane was characterized in human cultured intestinal cells (Caco-2) grown and differentiated on permeable filter supports. Cells were loaded by incubating with 3H-lysine from the apical (AP) side in the absence of sodium (substituted with choline) in the BL medium; under these conditions, cells accumulated lysine in the intracellular soluble pool to 10- to 20-fold the extracellular concentration. L-Lysine efflux in the BL medium was then followed, and initial rates of efflux were calculated under different experimental conditions. L-Lysine efflux exhibited a strong energy dependence. The presence of an inwardly directed gradient of sodium or lithium stimulated lysine efflux; ouabain reduced efflux in both sodium- and lithium-containing medium. When zwitterionic or cationic amino acids were added to the BL medium, L-lysine efflux was strongly stimulated. The most efficient trans-stimulating amino acids were L-leucine > L-methionine = L-ornithine = L-arginine. In the presence of trans-stimulating amino acids in the BL medium, L-lysine efflux exhibited energy independence and was not affected by the presence of a sodium gradient. In addition, the sensitivity, of efflux to N-ethylmaleimide was different in the absence or in the presence of amino acids in the BL medium. These results suggest that different mechanisms may operate in the BL efflux of L-lysine from human intestinal epithelial cells, depending on the extracellular availability of other amino acids, to guarantee optimal bioavailability of this essential amino acid both in the postprandial absorptive period and between meals.

Amino Acids↗
PubMed1997

[The diagnostic accuracy and reproducibility of computed tomography with water distention and induced hypotonia in the preoperative staging of gastric tumors].

Thirty-five patients with gastric cancer were preoperatively examined with CT performed in the prone position. Patient preparation consisted in filling the stomach with tap water and i.v. glucagon administration. The CT images were independently reviewed by two radiologists, who staged each tumor according to the TNM classification. The results were compared with surgical and histological findings. The overall accuracy for T staging ranged 74-77%, overstaging 17-23%; understaging was 3%. Diagnostic sensitivity, specificity and accuracy for serosal invasion were 100%, 80%, 85% and 100%, 84% e 88%, respectively, for the two radiologists. The overall accuracy for N staging was 48% and 51% for the two observers, respectively. Considering N1 and N2 as a single group, accuracy ranged 68-77%. The interobserver agreement analyzed by the "K tests" was 80%, with a K index of 60%. CT performed with the patient in the prone position, after preparation with gastric wall hypotony and distension with water, is a valid technique permitting excellent depiction of the gastric wall and providing useful preoperative information to the surgeon.

Adult↗
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

[Lithiasis of the common bile duct: the role of cholangiography and magnetic resonance].

The aim of our study was to evaluate the sensitivity, specificity and diagnostic accuracy of Magnetic Resonance Cholangiography (MR-CP) in patients with suspected choledocholithiasis. Sixty-two patients (mean age: 56.3 years) previously submitted to US, were examined with MRCP. MR exams were performed with an 0.5 T superconductive magnet (Gyroscan T5-II; Philips, Medical System, Best, NL) and a body coil. 3D-TSE sequences (TR/TE/ETL = 5.000/244/45 ms) were acquired, with 14 min 10 sec acquisition time. In the last 21 patients, acquisition time was reduced down to 3 min, by optimizing the parameters as follows: TR/TE/ETL = 3.000/700/128 ms. The images, obtained on the coronal plane, were then reconstructed with the MIP algorithm. MRCP images were studied both as MIP reconstructions and as single slices. The diagnosis was always compared with endoscopic or percutaneous findings. MRCP images were of diagnostic quality in all cases, with 91.7% sensitivity, 100% specificity and 96.8% diagnostic accuracy. MRCP had 100% positive predictive value and 95% negative predictive value. In conclusion, this technique is extremely useful to examine the patients with obstructive jaundice secondary to lithiasis.

Adult↗
PubMed1996

[Computed tomography patterns in patients treated with laparoscopic Nissen fundoplication for gastroesophageal reflux].

This work was aimed at investigating the CT anatomy in patients submitted to Nissen's fundoplication. Forty patients (mean age: 61 years) with peptic esophagitis (9 patients), refractory gastroesophageal (GE) reflux (11 patients) and hiatal hernia (20 patients) were examined. CT studies were performed with a third generation unit (CT Pace, General Electric, USA) with the patients in the prone position, after Gastrovison (Schering) and barium paste administration. In 34 patients, CT demonstrated surgery-related anatomical changes, such as the presence of a soft tissue mass at the distal third of the esophagus. In 4 patients, functional incompetence of the fundoplication (3 patients) and a recurrent hyatal hernia (1 patient) were demonstrated. In conclusion, CT studies performed with a dedicated technique permitted the accurate assessment of the anatomy of the GE junction after Nissen's fundoplication. In our study, CT demonstrated the presence of postoperative fluid collections and specific signs related to fundoplication incompetence. Our results suggest a possible application of CT to the postoperative follow-up of the patients submitted to Nissen's fundoplication, with a complementary role that of to endoscopy and functional exams.

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

[Usefulness of the new sequences of magnetic resonance in the study of hepatic hydatidosis].

We investigated the role of new MR Imaging techniques for the diagnosis, characterization and staging of hepatic hydatid disease. We examined 21 patients (30 hydatid cysts), 7 men and 14 women, ranging in age 26 to 74 years, with known hydatid disease. MR examinations were carried out on a 0.5T superconductive magnet (Philips Gyroscan T5, Philips Medical System) with the following imaging protocol: T1w (TR/TE/NEX: 300/10/4) SE, T2w (TR/TE/NEX: 3000/120/6) TSE and fat suppressed (SPIR technique) T2w (TR/TE/NEX: 3000/120/6) sequences. MR Angiography examinations were performed with 2D Time of Flight sequences (TR = 33 ms; TE = 6.9 ms; flip angle = 60 degrees; slice thickness = 4.0 mm with 2.0 mm overlapping; matrix = 256 x 256; number of slices = 45-50; acquisition time = 4 min 19 s), while MR cholangiography was performed with 3D, fat suppressed (SPIR) Turbo Spin-echo (TSE) sequences (TR = 3000 ms, TE = 700 ms, ETL = 12, acq. time = 5 min 48 s). MRI correctly detected all the hydatid cysts on both T1- and T2-weighted images. Characterization was correct in all the cysts larger than 3 cm, where typical signs consistent with hydatid disease were detected. MRA images always showed the inferior vena cava and the splenoportal system. The portal vessels were demonstrated only up to the first branches. In 3 cases an extrinsic compression of the inferior vena cava was diagnosed. MRC, performed in 7 cases, showed normal main bile duct caliber in 6 cases, while in another case, where a cyst ruptured inside the bile ducts, the communication between the cyst and the bile ducts was clearly demonstrated. In conclusion, MR Imaging is a valuable tool in the study of liver hydatid disease. Moreover, the availability of such new MR techniques as MRC and MRA, greatly improves the diagnostic role of MR imaging, especially when studying complications and before surgery.

Adult↗
PubMed1996

[Urography with magnetic resonance: a new method for the study of the renal collecting system in patients without obstructive uropathy].

A new MR technique is proposed to study the renal collecting system and the proximal ureteral portion in patients without obstructive uropathy, using fat-suppressed Turbo Spin Echo sequences, after drug-induced distension of the urinary tract. Nine normal volunteers and 16 patients (11 with renal stones, 1 with bilateral pyeloureteral junction stenosis, 1 with renal ptosis, 1 with ureteral hyperkinesia, 1 with renal tumor and 1 with a symptomatic renal cyst) were submitted to MR-Urography, performed with a 3D non-breath-hold fat-suppressed Turbo SE sequence (TR = 3000 ms, TE = 800 ms, 6 acquisitions, Turbo Factor = 128, Matrix = 128 x 256 or 256 x 256, acquisition time = 5 min 15 sec or 10 min 36 sec) on the coronal plane. With these acquisition parameters, parenchymal signal can be completely suppressed while enhancing fluid signal. These acquisitions were post-processed with the MIP algorithm to obtain very similar images to those of conventional urography. The maximum filling of the renal collecting system was obtained with the i.v. administration of 250 ml saline solution within 2-3 minutes and then the i.v. injection of 20 mg furosemide. The renal collecting system was optimally depicted in all the volunteers and the patients, except for 2 cases because of malfunctioning respiratory gating. Anatomical detailing was really improved after the diuretic administration, especially in the study of the major caliceal systems. To conclude, MR-Urography permits accurate morphological detailing of the renal collecting system also in patients without obstructive uropathy.

Adult↗