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Biomedical subjects

C Fiorentini

Publications and source records attributed to C Fiorentini.

At least 55 records · Page 3Linked to original sources
PubMed1999

N-acetylcysteine protects epithelial cells against the oxidative imbalance due to Clostridium difficile toxins.

Toxins A and B from the anaerobic bacterium Clostridium difficile are the causative agents of the antibiotic-associated pseudomembraneous colitis. At the subcellular level, they inhibit the Rho family GTPases, thus causing alterations of the actin cytoskeleton. The cytoskeletal integrity is also controlled by the redox state of cells. Therefore, we have evaluated whether an oxidative imbalance could be involved in the toxin-induced cytopathic effects. Our results indicate that both toxins induce oxidative stress with a significant depletion of protein SH-groups. These responses and the cytoskeleton-dependent cell retraction and rounding are significantly counteracted by N-acetylcysteine but not by alpha-tocopherol. Our study provides the first evidence that the thiol supplier N-acetylcysteine impairs the cellular intoxication by acting on the cytoskeleton integrity. This also suggests a possible beneficial role for this drug during therapeutic intervention.

Acetylcysteine↗
PubMed1999

Atrial fibrillation after operation for lung cancer: clinical and prognostic significance.

BACKGROUND: Atrial fibrillation is a common complication of early postoperative period in lung cancer thoracotomy. Its clinical incidence and short- and long-term impact on overall mortality has never been definitely assessed; moreover, it is unclear whether the arrhythmia represents an independent cardiac risk factor. METHODS: We prospectively studied 233 consecutive patients undergoing operation for lung cancer (170 with non-small-cell lung cancer). Postoperative atrial fibrillation incidence was related to different clinical factors possibly involved in its occurrence and to both short- and long-term survival. RESULTS: Atrial fibrillation occurred in 28 patients (12%) (same percentage in non-small-cell lung cancer); a strong relationship was observed between arrhythmia and age, history of hypertension and associated lymph node resection. The mean hospitalization time was 14 +/- 4 days in patients developing atrial fibrillation and 13 +/- 4 days in those who did not (p = not significant). No difference was observed between the two groups with regard to short- or long-term mortality or to long-term atrial fibrillation recurrences, also when considering the entire population and only non-small-cell lung cancer, separately. CONCLUSIONS: At our institution, early atrial fibrillation occurrence after operation for lung cancer does not show any negative impact on short- and long-term mortality or on recurrence rate.

Adult↗
PubMed1999

Growth factors in pituitary tumors.

Prolactin-secreting tumors are the most frequently occurring neoplasms in the human pituitary. Although the clinical syndrome associated with prolactinomas is well recognized the molecular and cellular mechanisms leading to cell transformation and development of these tumors remain elusive. In this paper we summarize recent evidence suggesting that both hypothalamic and intrapituitary defects can be involved in the development of prolactinomas. In particular alterations of the hypothalamo-pituitary dopaminergic transmission result in the dysregulation of the proliferative activity of lactotrope cells leading to tumor development. Similarly changes in the expression and activity of resident growth factors also play a role in pituitary tumorigenesis. In particular both overexpression of TGF alpha and loss of NGF production appear to be involved in the development and progression of prolactin-secreting tumors.

Adenoma↗
PubMed1999

Rho-dependent regulation of cell spreading by the tetraspan membrane protein Gas3/PMP22.

Gas3/PMP22 plays a crucial role in regulating myelin formation and maintenance, and different genetic alterations in gas3/PMP22 are responsible for a set of human peripheral neuropathies. We have previously demonstrated that Gas3/PMP22 could regulate susceptibility to apoptosis in NIH3T3 cells but not in REF 52 cells. In this report we demonstrate that when the apoptotic response triggered by gas3/PMP22 was counteracted by Bcl-2 coexpression, morphological changes were observed. Time-lapse analysis confirmed that Gas3/PMP22 can modulate cell spreading, and this effect was strengthened after inhibition of phosphoinositide 3-kinase. Using the active form of the small GTPase RhoA, we have been able to dissect the different Gas3/PMP22 biological activities. RhoA counteracted the Gas3/PMP22-dependent morphological response but was unable to neutralize the apoptotic response. Treatment of NIH3T3 cells with cytotoxic necrotizing factor 1, which activates endogenous Rho, also counteracted Gas3/PMP22-mediated cell shape and spreading changes. Treatment of REF 52 cells, which are unresponsive to Gas3/PMP22 overexpression, with the C3 exoenzyme, inhibiting Rho activity, renders REF 52 cells responsive to Gas3/PMP22 overexpression for cell shape and spreading changes. Finally, assembly of stress fibers and focal adhesions complexes, in response to lysophosphatidic acid-induced endogenous Rho activation, was impaired in Gas3/PMP22-overexpressing cells. We hypothesize that cell shape and spreading regulated by Gas3/PMP22 through the Rho GTPase might have an important role during Schwann cells differentiation and myelinization.

3T3 Cells↗
PubMed1999

Occurrence, diversity, and pathogenicity of halophilic Vibrio spp. and non-O1 Vibrio cholerae from estuarine waters along the Italian Adriatic coast.

The occurrence, diversity, and pathogenicity of Vibrio spp. were investigated in two estuaries along the Italian Adriatic coast. Vibrio alginolyticus was the predominant species, followed by Vibrio parahaemolyticus, non-O1 Vibrio cholerae, and Vibrio vulnificus. By using a biochemical fingerprinting method, all isolates were grouped into nine phenotypes with similarity levels of 75 to 97.5%. The production of toxins capable of causing cytoskeleton-dependent changes was detected in a large number of Vibrio strains. These findings indicate a significant presence of potentially pathogenic Vibrio strains along the Adriatic coast.

Animals↗
PubMed1999

Vibrio parahaemolyticus thermostable direct hemolysin modulates cytoskeletal organization and calcium homeostasis in intestinal cultured cells.

Vibrio parahaemolyticus is a marine bacterium known to be the leading cause of seafood gastroenteritis worldwide. A 46-kDa homodimer protein secreted by this microorganism, the thermostable direct hemolysin (TDH), is considered a major virulence factor involved in bacterial pathogenesis since a high percentage of strains of clinical origin are positive for TDH production. TDH is a pore-forming toxin, and its most extensively studied effect is the ability to cause hemolysis of erythrocytes from different mammalian species. Moreover, TDH induces in a variety of cells cytotoxic effects consisting mainly of cell degeneration which often leads to loss of viability. In this work, we examined the cellular changes induced by TDH in monolayers of IEC-6 cells (derived from the rat crypt small intestine), which represent a useful cell model for studying toxins from enteric bacteria. In experimental conditions allowing cell survival, TDH induces a rapid transient increase in intracellular calcium as well as a significant though reversible decreased rate of progression through the cell cycle. The morphological changes seem to be dependent on the organization of the microtubular network, which appears to be the preferential cytoskeletal element involved in the cellular response to the toxin.

Animals↗
PubMed1999

Detection of Toscana virus-specific immunoglobulins G and M by an enzyme-linked immunosorbent assay based on recombinant viral nucleoprotein.

An enzyme-linked immunosorbent assay (ELISA) based on the recombinant Toscana virus nucleoprotein (rN) has been developed. Its sensitivity and specificity for the detection of virus-specific immunoglobulins G and M in human sera were similar to those of the ELISA that is based on an antigen extracted from infected mouse brain and that is routinely used for serodiagnosis.

Animals↗
PubMed1999

[Myocardial scintigraphy by the gated SPECT method in coronary disease patients with postischemic stunning].

UNLABELLED: Gated SPECT using Tc-99m-labeled flow tracers provides simultaneous assessment of global and regional myocardial perfusion and function. The aim of this study was to evaluate whether regional wall thickening (WT) obtained after stress and at rest makes it possible to identify and analyze a subgroup of post-ischemic stunned patients. METHODS: We studied 20 patients (18 males) who underwent conventional diagnostic dual-day stress/rest Gated SPECT following injection of 925 MBq of 99mTc-tetrofosmin using a dual-head SPECT camera (Vertex ADAC). The mean age of these patients was 59 years (38-71) and 10 of them had a history of previous acute myocardial infarction (AMI). Perfusion was analyzed on ungated images using 20 segments scored on a 5-point scale (0 = normal, 4 = no uptake), while WT and motion were assessed visually on stress/rest end-systolic images using a 4-point score (0 = normal, 3 = absence of WT/motion). Left ventricular ejection fraction (LVEF) and volumes were calculated. All patients underwent coronary angiography. RESULTS: All patients showed at least one reversible defect with post-stress WT reduction and normal rest WT. The stunned group showed a significant post-stress reduction of LVEF and a statistically non-significant increase of end systolic volume (ESV). A good correlation was observed between global perfusion and WT score both at stress and rest conditions; LVEF showed a significant inverse correlation with global post-stress and rest perfusion and WT score. ESV and the global perfusion stress/rest score showed a good correlation, while end-diastolic volume did not correlate. In 44% of the segments with fixed defects, there was a normal WT and normal coronary-related vessel (false positives); 28% of reversible segments showed a post-stress pathological WT and five of them a rest pathological WT. CONCLUSIONS: The gated SPECT myocardial perfusion evaluation allowed us to analyze a subgroup of post-stress stunned coronary artery disease patients. The post-stress LVEF reduction in this population seems to be due to the increase of end-systolic volume caused by endocardial ischemia. The stunned segments showed severe perfusion defects.

Adult↗
PubMed1999

[A comparison between attenuation-corrected and -uncorrected transmission-emission SPECT images obtained with Tl-201 in CAD patients].

BACKGROUND: The aim of this study was to evaluate the impact of attenuation correction (AC) on the diagnostic accuracy of conventional stress/red thallium SPECT studies. METHODS: We studied 60 consecutive patients (36 males) who underwent conventional diagnostic stress/red study with and without AC (NAC) using a dual-head SPECT camera (Vertex ADAC) with a 153Gd source. The mean age of these patients was 60 years (30-80) and 29 of the subjects had a history of MI. Reconstructed images were visually analyzed using 20 segments scored on a 5-point scale (0 = normal, 4 = no uptake). Diagnostic accuracy was evaluated in 24 consecutive patients who underwent coronary angiography. Polar plots from each of the four reconstructed data sets per patient were normalized on the maximum and quantified using a nine segment model. RESULTS: The comparison between the segmental stress score obtained with and without AC showed agreement in 1057 out of 1200 (88%) segments analyzed, K statistic value = 0.67. The number of fixed defects was significantly lower after AC. The diagnostic accuracy, evaluated in 24 patients (480 segs), was not significantly different between AC and NAC analysis (80 vs 84% respectively). CONCLUSIONS: AC seems to reduce the number of fixed defects due to attenuation artefacts without improving diagnostic accuracy, probably because of the low number of subjects submitted to angiography and of the interpreting bias due to the expertise of the operators. In fact, in the rather small group of patients evaluated, no improvement in diagnostic accuracy was observed, probably because several attenuation defects were not considered pathological due to operator expertise.

Adult↗
PubMed1999

Left ventricular opacification by intravenous contrast echocardiography.

BACKGROUND: The present study was undertaken in order to evaluate the efficacy of the intravenous administration of Albunex in obtaining left ventricular opacification and the relationship between left ventricular opacification and pulmonary pressures and cardiac function. METHODS: Fifty-two adult patients, mostly affected by ischemic heart disease, were enrolled in the study. In 37 of these patients, a complete right heart hemodynamic study was performed after Swan-Ganz catheterization. Albunex was administered in three randomized doses (0.10, 0.15 and 0.20 ml/kg) to all the patients. Left ventricular opacification was assessed both visually and using videodensitometric analysis. RESULTS: Left ventricular opacification was obtained in 93% of all the injections and an intermediate or strong opacification was obtained in 68%, while absent opacification was observed in 6% of the injections, irrespective of the contrast dose. An incremental opacification efficacy trend was observed from the lower to the higher dose, with an intermediate or strong opacification in 58 and in 77% of 0.10 and 0.20 ml/kg injections, respectively. Irrespective of the contrast dose, an enhancement of the endocardial borders was observed in 61% of the wall segments suboptimally visualized in basal conditions. The endocardial borders enhancement was obtained in 39 and in 79% of segments using the 0.10 and the 0.20 ml/kg doses, respectively. No statistically significant differences were observed between the videodensitometric parameters obtained using the three contrast doses. Finally, a significant relationship was observed between left ventricular opacification parameters and pulmonary pressures and left ventricular functional parameters, irrespective of the contrast doses considered. CONCLUSIONS: The results we obtained demonstrate the good overall efficacy of Albunex administered intravenously in order to obtain left ventricular opacification in a clinical population of cardiac patients. Moreover, they suggest that the dosage to be used clinically should preferably be at least 0.20 ml/kg, although no significant influence of contrast dosage on videodensitometric parameters has been observed. Finally, irrespective of the contrast dosage, the magnitude of left ventricular opacification appears to be influenced by the hemodynamic status of the patient.

Adult↗
PubMed1999

Myocardial viability assessment after acute myocardial infarction: low-dose dobutamine echocardiography versus rest-redistribution thallium-201 SPECT.

BACKGROUND: The presence of tissue viability is of great importance in the prognostic work-up of patients recovering from acute myocardial infarction. However, uncertainty still exists concerning the optimal tool for its assessment. The present study was undertaken in order to compare low-dose dobutamine echocardiography and rest-redistribution thallium SPECT for predicting late improvement of regional left ventricular function after acute myocardial infarction. METHODS: Fifteen patients undergoing coronary angiography, low-dose dobutamine echocardiography and rest-redistribution thallium SPECT after thrombolyzed anterior acute myocardial infarction were studied. A 3 month follow-up echocardiogram was performed in all patients and 9 underwent coronary revascularization. RESULTS: A significant (> or = 70%) residual stenosis of the infarct-related artery was present in 14 patients, whilst a total occlusion was observed in 1. At 3 month follow-up, 41% of the dyssynergic segments improved. The sensitivity, specificity and accuracy for late wall motion improvement was 61, 89 and 77% for low-dose dobutamine echocardiography and, respectively, 76, 45 and 58% for rest-redistribution thallium SPECT. Tissue viability was detected in 65 and 31% of dyssynergic segments by rest-redistribution thallium SPECT and low-dose dobutamine echocardiography, respectively (p < 0.001). The agreement between the two techniques was 48%. CONCLUSIONS: Low-dose dobutamine echocardiography is more accurate than rest-redistribution thallium SPECT for predicting 3 month wall motion improvement in patients with acute anterior myocardial infarction, mainly due to its significantly better specificity.

Adult↗
PubMed1999

Short-term neurobehavioural effects in anaesthetists with low exposure to nitrous oxide.

The aim of this study was to assess whether a sample of 37 anaesthetists occupationally exposed only to N2O showed any deterioration in vigilance and/or mood. The anaesthetists were examined with three neurobehavioural tests (Simple Reaction Time and Colour Word Vigilance to measure the vigilance and Mood Rating Scale to evaluate the level of stress and arousal) and underwent N2O biological monitoring (to correlate the test results with the N2O exposure) on the first and on the last day of the work week, before and after work in the operating room. No significant relationship was found between the biological monitoring and the test results. The only significant statistical difference was found between the beginning and the end of each workday in the arousal level, regardless of the result of the biological monitoring.

Adult↗
PubMed1998

The effect of oxygen on the growth and cell morphology of Helicobacter pylori.

The in vitro effect of progressive oxygen decrease on the growth and morphology of Helicobacter pylori was studied. H. pylori ATCC 43,504 was used for the experiments. The strain inoculated in Brucella broth plus fetal calf serum was incubated under a controlled atmosphere with oxygen concentration from 5 to 0%. CFU ml-1 and bacterial morphology were detected at the time of spreading and at 24 h, 72 h, 7 days and 14 days. A detailed ultrastructural investigation of the bacterial cells, grown in different experimental conditions, was performed by scanning electron microscopy. Oxygen deprivation produced a rapid reduction of CFU ml-1. In particular, a significant reduction of viable bacteria was recorded at 72 h of incubation in the presence of 1% oxygen and anaerobiosis, and 0 CFU ml-1 was found after 7 days of incubation at the above mentioned oxygen concentrations. The coccoid phenotype was already prevalent after 24 h of incubation with a progressive tendency to aggregate in clusters. These clusters were progressively larger, depending on the reduction of oxygen concentration, since the aggregation phenomenon can be the expression of a hypothesized mechanism of protection among bacterial cells.

Aerobiosis↗
PubMed1998

Toxin-induced activation of Rho GTP-binding protein increases Bcl-2 expression and influences mitochondrial homeostasis.

It is now well established that apoptosis plays a pivotal role in several physiological and pathological situations. Consequently, the mechanisms controlling the cell fate are currently the subject of intense investigation. In this work, we report that an Escherichia coli protein toxin (Cytotoxic Necrotizing Factor 1, CNF1) which activates the Rho GTP-binding protein and prevent apoptosis in epithelial cells was able to: (i) influence the mitochondrial homeostasis and (ii) modulate the expression of proteins belonging to the Bcl-2 family. In particular, the content of the antiapoptotic products Bcl-2 and Bcl-XL resulted to be increased in treated cells, whereas the expression of the proapoptotic protein Bax remained unaltered. CNF1 induces cell spreading via activation of Rho and cell spreading has been reported to promote cell survival. Cytochalasin B, which provokes most of the morphological changes typical of CNF1, including cell spreading, but without the involvement of Rho, was unable to counteract apoptosis. Altogether our results suggest a link between the Rho GTP-binding protein and the regulation of the mitochondrial homeostasis via an effect on the antiapoptotic proteins of the Bcl-2 family.

Apoptosis↗
PubMed1998

Different clinical and prognostic significance of painful and silent myocardial ischemia detected by exercise electrocardiography and dobutamine stress echocardiography after uncomplicated myocardial infarction.

Prevalence and prognostic significance of painful and silent ischemia detected by exercise electrocardiography (ECG) and dobutamine stress echocardiography (DSE) were evaluated in 407 consecutive patients recovering from acute myocardial infarction. Painful ischemia assessed by both tests was not associated with different clinical characteristics of patients; on the other hand, it identified a higher risk subgroup compared with silent ischemia during exercise ECG but not during DSE.

Aged↗
PubMed1998

Toscana virus infections of the central nervous system in children: a report of 14 cases.

OBJECTIVE: To evaluate the pathogenicity of a recently discovered arthropod-transmitted bunyavirus (Toscana virus) on the CNS in children and to provide information on the epidemiologic and clinical aspects of Toscana virus infection. STUDY DESIGN: Case-series analysis of children hospitalized with clinical and cerebrospinal fluid examination compatible with a CNS disease of viral origin. METHODS: Cerebrospinal fluid, acute, and convalescent sera were investigated for conventional neurotropic viruses and for Toscana and tickborne encephalitis viruses. A clinical-epidemiologic analysis was carried out on confirmed Toscana virus cases to clarify the profile of Toscana virus infection in children. RESULTS: The study indicates that (1) Toscana virus has been endemic in the Siena province for at least 15 years; (2) the virus is responsible for at least 80% of acute viral infections of the CNS in children throughout the summertime; (3) the clinical signs and symptoms range from aseptic meningitis to meningoencephalitis; (4) infected children resided habitually or temporarily in rural or suburban areas of the Siena province, where ecological characteristics allow arthropods to be peridomestic in human settlements. CONCLUSIONS: Toscana virus is the most common viral agent involved in acute infections of CNS in children in central Italy.

Acute Disease↗
PubMed1998

Toxins from anaerobic bacteria: specificity and molecular mechanisms of action.

Major advances have been made in the past five years in the identification of cellular targets of toxins produced by anaerobic bacteria. These targets include the vesicular membrane docking and fusion apparatus, the actin cytoskeleton, the signal transduction machinery and the cell membrane. The recent discovery that large clostridial toxins (Clostridium difficile A and B toxins, C. sordellii lethal and hemorrhagic toxins, and alpha C. novyi toxin) are monoglucosyltransferases, together with the establishment of the perfringolysin crystal structure, has led to new insights in the field of toxins from anaerobic bacteria.

Bacterial Toxins↗