Biomedical subjects

Paolo Visca

Publications and source records attributed to Paolo Visca.

48 records · Page 3Linked to original sources

PubMed2002

Nitric oxide and Mycobacterium leprae pathogenicity.

Leprosy is an old, still dreaded infectious disease caused by the obligate intracellular bacterium Mycobacterium leprae. During the infectious process, M. leprae is faced with the host macrophagic environment, where the oxidative stress and NO release, combined with low pH, low pO2, and high pCO2, contribute to limit the growth of the bacilli. Comparative genomics has unraveled massive gene decay in M. leprae, linking the strictly parasitic lifestyle with the reductive genome evolution. Compared with Mycobacterium tuberculosis and Mycobacterium bovis, the leprosy bacillus has lost most of the genes involved in the detoxification of reactive oxygen and nitrogen species. The very low reactivity of the unique truncated hemoglobin retained by M. leprae could account for the susceptibility of this exceptionally slow-growing microbe to NO.

Mycobacterium leprae↗

PubMed2002

Composite integron array generated by insertion of an ORF341-type integron within a Tn21-like element.

Two class 1 integrons, In-t1 and In-t2, were previously identified in IncFI plasmids of Salmonella enterica serotype Typhimurium. Molecular analysis revealed a close physical link between the two integrons. In-t1 is preceded by the transposase genes of Tn21, whereas In-t2 is located downstream the 3'-conserved segment (3'-CS) of In-t1, in a head-to-tail configuration. In-t1 shows a peculiar sequence downstream the 3'-CS, containing an extended version of the open reading frame known as ORF341 (referred to as ORF341E) and a novel trimethoprim resistance gene, designated dfrA18. Retrospective analysis provided evidence for In-t1 insertion within Tn1935, a Tn21-related transposon identified in IncFI plasmids circulating among epidemic clones of multidrug-resistant S. enterica during the 1970s. Structural comparison between Tn21 derivatives from recent and ancestor IncFI plasmids showed that In-t2 has been conserved by these replicons. In-t1 belongs to a novel family of class 1 integrons containing the ORF341E sequence, and appears to have been acquired by IncFI plasmids after the assembly of Tn1935. In-t1 insertion occurred within the 5'-conserved segment (5'-CS) proximal region of the resident In-t2.

Amino Acid Sequence↗

PubMed2002

Different responses of pyoverdine genes to autoinduction in Pseudomonas aeruginosa and the group Pseudomonas fluorescens-Pseudomonas putida.

We investigated the regulation of the psbA and pvdA pyoverdine biosynthesis genes, which encode the L-ornithine N(5)-oxygenase homologues in Pseudomonas strain B10 and Pseudomonas aeruginosa PAO1, respectively. We demonstrate that pyoverdine(B10), as the end product of its biosynthetic pathway, is a key participant of the control circuit regulating its own production in Pseudomonas strain B10. In P. aeruginosa PAO1, however, pyoverdine(PAO1) has no apparent role in the positive regulation of the pvdA gene.

Bacterial Proteins↗

PubMed2002

Antibodies to 60-kilodalton heat shock protein and outer membrane protein 2 of Chlamydia pneumoniae in patients with coronary heart disease.

Evidence linking Chlamydia pneumoniae infection to atherosclerosis and to atherothrombotic events has recently emerged. A primary candidate implicated in these pathogenetic events is the 60-kDa chlamydial heat shock protein (HSP60). Another putative candidate to activate a potential proinflammatory mechanism is the chlamydial outer membrane protein 2 (OMP2). We have generated both HSP60 and OMP2 recombinant antigens in a nondenatured form and shown that (i) the two antigens were highly immunogenic in mice and (ii) murine antisera thus generated recognized the native C. pneumoniae proteins. We measured by enzyme linked immunosorbent assay (ELISA) and immunoblot assay antibody titers to the recombinant antigens in samples from 219 patients with coronary heart disease (CHD), 179 patients with unstable angina (UA), 40 patients with acute myocardial infarction (AMI), and 100 age-, sex-, and risk factor-matched healthy controls. We also examined whether anti-HSP60 and/or anti-OMP2 antibodies correlated with anti-C. pneumoniae antibodies assessed by a commercial microimmunofluorescence (MIF) assay. Immunoglobulin G (IgG), but neither IgA nor IgM, antibodies against the two recombinant proteins were detected by ELISA. In particular, anti-HSP60 antibodies were detected in >99% of CHD patients versus 0% of the controls, whereas the proportions of anti-OMP2 positive subjects were >70 and 27%, respectively. Nonetheless, among CHD patients, similar frequencies of positive subjects and titers of anti-HSP60 or anti-OMP2 antibodies were present in UA and AMI subjects. The anti-OMP2, but not the anti-HSP60, antibodies showed high specificity. Consistently, high serological correlation was observed between IgG MIF titers and IgG ELISA reactivity to OMP2 but not to HSP60. Overall, the results of this study demonstrate a strong correlation between CHD and anti-HSP60 IgG levels, as measured by our in-house ELISA. They also suggest that recombinant OMP2 ELISA, because of its high specificity and strong correlation with MIF assay, could be a candidate diagnostic marker for C. pneumoniae infection, which would be of potential usefulness for its specificity and nonsubjective nature.

Adult↗

PubMed2002

Effect of acid adaptation on the fate of Listeria monocytogenes in THP-1 human macrophages activated by gamma interferon.

In Listeria monocytogenes the acid tolerance response (ATR) takes place through a programmed molecular response which ensures cell survival under unfavorable conditions. Much evidence links ATR with virulence, but the molecular determinants involved in the reactivity to low pHs and the behavior of acid-exposed bacteria within host cells are still poorly understood. We have investigated the effect of acid adaptation on the fate of L. monocytogenes in human macrophages. Expression of genes encoding determinants for cell invasion and intracellular survival was tested for acid-exposed bacteria, and invasive behavior in the human myelomonocytic cell line THP-1 activated with gamma interferon was assessed. Functional approaches demonstrated that preexposure to an acidic pH enhances the survival of L. monocytogenes in activated human macrophages and that this effect is associated with an altered pattern of expression of genes involved in acid resistance and cell invasion. Significantly decreased transcription of the plcA gene, encoding a phospholipase C involved in vacuolar escape and cell-to-cell spread, was observed in acid-adapted bacteria. This effect was due to a reduction in the quantity of the bicistronic plcA-prfA transcript, concomitant with an increase in the level(s) of the monocistronic prfA mRNA(s). The transcriptional shift from distal to proximal prfA promoters resulted in equal levels of the prfA transcript (and, as a consequence, of the inlA, hly, and actA transcripts) under neutral and acidic conditions. In contrast, the sodC and gad genes, encoding a cytoplasmic superoxide dismutase and the glutamate-based acid resistance system, respectively, were positively regulated at a low pH. Morphological approaches confirmed the increased intracellular survival and growth of acid-adapted L. monocytogenes cells both in vacuoles and in the cytoplasm of interferon gamma-activated THP-1 macrophages. Our data indicate that preexposure to a low pH has a positive impact on subsequent challenge of L. monocytogenes with macrophagic cells.

Adaptation, Physiological↗

PubMed2002

Functional characterization and regulation of gadX, a gene encoding an AraC/XylS-like transcriptional activator of the Escherichia coli glutamic acid decarboxylase system.

The Escherichia coli chromosome contains two distantly located genes, gadA and gadB, which encode biochemically undistinguishable isoforms of glutamic acid decarboxylase (Gad). The Gad reaction contributes to pH homeostasis by consuming intracellular H(+) and producing gamma-aminobutyric acid. This compound is exported via the protein product of the gadC gene, which is cotranscribed with gadB. Here we demonstrate that transcription of both gadA and gadBC is positively controlled by gadX, a gene downstream of gadA, encoding a transcriptional regulator belonging to the AraC/XylS family. The gadX promoter encompasses the 67-bp region preceding the gadX transcription start site and contains both RpoD and RpoS putative recognition sites. Transcription of gadX occurs in neutral rich medium upon entry into the stationary phase and is increased at acidic pH, paralleling the expression profile of the gad structural genes. However, P(T5)lacO-controlled gadX expression in neutral rich medium results in upregulation of target genes even in exponential phase, i.e., when the gad system is normally repressed. Autoregulation of the whole gad system is inferred by the positive effect of GadX on the gadA promoter and gadAX cotranscription. Transcription of gadX is derepressed in an hns mutant and strongly reduced in both rpoS and hns rpoS mutants, consistent with the expression profile of gad structural genes in these genetic backgrounds. Gel shift and DNase I footprinting analyses with a MalE-GadX fusion protein demonstrate that GadX binds gadA and gadBC promoters at different sites and with different binding affinities.

ATP-Binding Cassette Transporters↗

PubMed2002

Sicca syndrome associated with Tropheryma whipplei intestinal infection.

The case of a 61-year-old woman with Whipple's disease-associated sicca complex is reported. Tropheryma whipplei infection was diagnosed by histological and ultrastructural examination of the jejunal mucosa and sequence analysis of the bacterial 16S ribosomal DNA. The role of vitamin A malabsorption in sicca complex secondary to Whipple's disease is discussed.

Actinobacteria↗

PubMedDate not supplied

An improved PCR-based method for detection and differentiation of Entamoeba histolytica and Entamoeba dispar in formalin-fixed stools.

Detection of infectious agents in faecal samples by polymerase chain reaction (PCR) can be limited by the presence of substances which inhibit DNA amplification. Here, an improved protocol is reported for directly isolating DNA from fresh and aged formalin-fixed stools, after concentration by formalin-ethyl acetate (FEA). The protocol was successfully applied to detect DNA of Entamoeba histolytica/Entamoeba dispar complex in stools by nested PCR, showing high specificity and low detection limit. Extended time of specimen storage in formalin had no influence on PCR yields. This PCR-based method offers technical advantages for routine detection and discrimination of invasive E. histolytica and non-invasive E. dispar.

Animals↗

PubMedDate not supplied

Role and prognostic significance of CD44s expression in colorectal cancer.

UNLABELLED: The purpose of this study was to clarify the role and the predictive strength of the adhesion molecule CD44s (standard isoform) in colorectal carcinogenesis. MATERIALS AND METHODS: CD44s immunohistochemical expression was evaluated in 100 patients with colon adenoma and 100 patients with colon adenocarcinoma and adjacent non-neoplastic mucosa (ANNM). The patients were followed-up for five years. RESULTS: CD44s immunoreactivity was expressed in low-moderate-high-grade dysplasia adenomas and associated with adenocarcinoma (p = 0.01), ANNM (p = 0.05) and pTNM stage (p = 0.00001). Univariate analysis revealed that CD44s expression was associated with overall survival (OS) in carcinomas (p = 0.01) and ANNM (p = 0.05). Bivariate analysis revealed that CD44s was associated with OS in stages I and II patients (p = 0.03). Multivariate analysis revealed that stage (p = 0.0001) and CD44s expression (p = 0.05) were independent predictors of OS. CONCLUSION: CD44s is involved in colon carcinogenesis and is associated with aggressive carcinomas. The immunohistochemical expression of CD44s may reveal cells that have lost their adhesion ability and therefore detect carcinomas with high metastatic power.

Adenocarcinoma↗

PubMedDate not supplied

Immunohistochemical expression and prognostic significance of FAS and GLUT1 in bladder carcinoma.

BACKGROUND: Fatty Acid Synthase (FAS) and Human Erythrocyte Glucose Transporter 1 (GLUT1) are new markers involved in the biological activities of cancer cells. FAS is a multifunctional enzyme that synthesizes palmitate from acetyl-CoA and malonyl-CoA. GLUT1 is a transmembrane protein normally expressed in perineurium and erythrocytes. FAS and GLUT1 expression have been recently described in many aggressive tumors. We explored the immunohistochemical expression of FAS and GLUT1 in bladder carcinomas to reveal statistical associations with clinico-pathological features and recurrence. MATERIALS AND METHODS: Thirty-one node- and distant metastasis-negative transitional cell carcinomas from patients with a five-year follow-up were evaluated for FAS and GLUT1 expression. RESULTS: Univariate analysis showed that low-grade, pTa stage and FAS-negative expression were associated with indolent tumors. Multivariate analysis showed that FAS expression (p = 0.006) and pT1-2 stage tumors (p = 0.001) were independent predictors of recurrence. CONCLUSION: Endogenous fatty acids are an exploitable storage of energy for aggressive human bladder carcinomas. Glucose uptake is not required by bladder tumors.

Analysis of Variance↗

PubMedDate not supplied

Fatty acid synthase (FAS) is a marker of increased risk of recurrence in lung carcinoma.

BACKGROUND: We explored the expression of Fatty Acid Synthase (FAS) in lung carcinomas and its association with clinico-pathological features and prognosis. FAS is a recently discovered molecule involved in the energy supply of normal cells. FAS is also overexpressed in neoplastic tissues because of their increased necessity for energy. PATIENTS AND METHODS: One hundred and six patients with non-small cell lung carcinoma were followed-up for an average period of 5 years. FAS expression was detected immunohistochemically. RESULTS: FAS staining was observed in 61 out of 106 cases (57.54%). Statistical analysis revealed that FAS had an overall low prognostic value (p = 0.14), while FAS-negative expression in stage I patients showed a trend for better survival (p = 0.10). PTNM stage (p < 0.0001) was the only significant prognostic marker for overall survival. CONCLUSION: FAS is a reliable marker of low-stage clinically aggressive lung carcinomas. The determination of FAS expression in lung carcinomas may stratify patients and determine therapeutic approaches for their care.

Aged↗

PubMedDate not supplied

Tissue microarray analysis of FAS, Bcl-2, Bcl-x, ER, PgR, Hsp60, p53 and Her2-neu in breast carcinoma.

BACKGROUND: The aim of this study was to detect immunohistochemical markers in breast carcinoma by means of tissue microarray analysis (TMA) and to associate their expressions with clinicopathological features and prognosis. Fatty acid synthase, bcl-2, bcl-x, p53, estrogen and progesterone receptors, heat shock protein 60 and Her2-neu (c-erbB-2) were evaluated in a group of 149 breast carcinoma patients with a 5-year follow-up period. MATERIALS AND METHODS: TMA blocks were made by using duplicate 0.6-mm diameter tissue cores from each paraffin block. RESULTS: Statistical analysis revealed that tumor stage (p=0.003) and node status (p=0.001) were the only two prognostic markers of disease-free survival. Moreover, FAS and bcl-x showed an independent effect on recurrence (p=0.005). The node status was the only marker of overall survival (p=0.05). CONCLUSION: Our data confirmed recent reports associating the stage of disease, FAS and Bcl-x expressions with recurrence and outcome. These data demonstrated that TMA is an effective substitute for conventional histochemical-immunohistochemical techniques.

Breast Neoplasms↗