Showing papers by "University of Milano-Bicocca published in 2001"

Dendritic cells express tight junction proteins and penetrate gut epithelial monolayers to sample bacteria.

Abstract: Penetration of the gut mucosa by pathogens expressing invasion genes is believed to occur mainly through specialized epithelial cells, called M cells, that are located in Peyer's patches. However, Salmonella typhimurium that are deficient in invasion genes encoded by Salmonella pathogenicity island 1 (SPI1) are still able to reach the spleen after oral administration. This suggests the existence of an alternative route for bacterial invasion, one that is independent of M cells. We report here a new mechanism for bacterial uptake in the mucosa tissues that is mediated by dendritic cells (DCs). DCs open the tight junctions between epithelial cells, send dendrites outside the epithelium and directly sample bacteria. In addition, because DCs express tight-junction proteins such as occludin, claudin 1 and zonula occludens 1, the integrity of the epithelial barrier is preserved.

Inducible IL-2 production by dendritic cells revealed by global gene expression analysis.

Abstract: Dendritic cells (DCs) are strong activators of primary T cell responses. Their priming ability is acquired upon encounter with maturation stimuli. To identify the genes that are differentially expressed upon maturation induced by exposure to Gram-negative bacteria, a kinetic study of DC gene expression was done with microarrays representing 11,000 genes and ESTs (expressed sequence tags). Approximately 3000 differentially expressed transcripts were identified. We found that functional interleukin 2 (IL-2) mRNA, which gave rise to IL-2 production, was transiently up-regulated at early time-points after bacterial encounter. In contrast, macrophages did not produce IL-2 upon bacterial stimulation. Thus, IL-2 is an additional key cytokine that confers unique T cell stimulatory capacity to DCs.

Behavior of borderline tumors with particular interest to persistence, recurrence, and progression to invasive carcinoma: a prospective study

Abstract: PURPOSE: Borderline tumors account for 10% to 20% of epithelial ovarian tumors, and their prognosis is outstanding; nevertheless, a mortality of up to 20% has been reported, particularly in earlier reports. There is a lack of information about the actual mortality and the rate of progression into invasive carcinoma in large and prospectively accrued populations. PATIENTS AND METHODS: All women with borderline ovarian tumors undergoing primary surgery in our department or referred within 3 months from surgery performed elsewhere from 1982 to 1997 were prospectively accrued and observed. RESULTS: We studied 339 women (83.4% stage I, 7.9% stage II, and 8.5% stage III). The median age at diagnosis was 39 years. A total of 150 women underwent radical surgery, and 189 underwent fertility-sparing surgery. After surgery, 13 women had macroscopic residual disease. With a median follow-up of 70 months, 317 women are alive with no clinical disease (eight with documented subclinical persistence of implants), three ar...

The Adenylate Cyclase Toxin of Bordetella pertussis Binds to Target Cells via the αMβ2 Integrin (Cd11b/Cd18)

Abstract: The adenylate cyclase toxin (CyaA) of Bordetella pertussis is a major virulence factor required for the early phases of lung colonization. It can invade eukaryotic cells where, upon activation by endogenous calmodulin, it catalyzes the formation of unregulated cAMP levels. CyaA intoxication leads to evident toxic effects on macrophages and neutrophils. Here, we demonstrate that CyaA uses the αMβ2 integrin (CD11b/CD18) as a cell receptor. Indeed, the saturable binding of CyaA to the surface of various hematopoietic cell lines correlated with the presence of the αMβ2 integrin on these cells. Moreover, binding of CyaA to various murine cell lines and human neutrophils was specifically blocked by anti-CD11b monoclonal antibodies. The increase of intracellular cAMP level and cell death triggered by CyaA intoxication was also specifically blocked by anti-CD11b monoclonal antibodies. In addition, CyaA bound efficiently and triggered intracellular cAMP increase and cell death in Chinese hamster ovary cells transfected with αMβ2 (CD11b/CD18) but not in cells transfected with the vector alone or with the αXβ2 (CD11c/CD18) integrin. Thus, the cellular distribution of CD11b, mostly on neutrophils, macrophages, and dendritic and natural killer cells, supports a role for CyaA in disrupting the early, innate antibacterial immune response.

Theta-Frequency Bursting and Resonance in Cerebellar Granule Cells: Experimental Evidence and Modeling of a Slow K+-Dependent Mechanism

Abstract: Neurons process information in a highly nonlinear manner, generating oscillations, bursting, and resonance, enhancing responsiveness at preferential frequencies. It has been proposed that slow repolarizing currents could be responsible for both oscillation/burst termination and for high-pass filtering that causes resonance (Hutcheon and Yarom, 2000). However, different mechanisms, including electrotonic effects (Mainen and Sejinowski, 1996), the expression of resurgent currents (Raman and Bean, 1997), and network feedback, may also be important. In this study we report theta-frequency (3‐12 Hz) bursting and resonance in rat cerebellar granule cells and show that these neurons express a previously unidentified slow repolarizing K 1 current (IK-slow). Our experimental and modeling results indicate that IK-slow was necessary for both bursting and resonance. A persistent (and potentially a resurgent) Na 1 current exerted complex amplifying actions on bursting and resonance, whereas electrotonic effects were excluded by the compact structure of the granule cell. Theta-frequency bursting and resonance in granule cells may play an important role in determining synchronization, rhythmicity, and learning in the cerebellum.

Reorganization of multivesicular bodies regulates MHC class II antigen presentation by dendritic cells

Abstract: Immature dendritic cells (DCs) sample their environment for antigens and after stimulation present peptide associated with major histocompatibility complex class II (MHC II) to naive T cells. We have studied the intracellular trafficking of MHC II in cultured DCs. In immature cells, the majority of MHC II was stored intracellularly at the internal vesicles of multivesicular bodies (MVBs). In contrast, DM, an accessory molecule required for peptide loading, was located predominantly at the limiting membrane of MVBs. After stimulation, the internal vesicles carrying MHC II were transferred to the limiting membrane of the MVB, bringing MHC II and DM to the same membrane domain. Concomitantly, the MVBs transformed into long tubular organelles that extended into the periphery of the cells. Vesicles that were formed at the tips of these tubules nonselectively incorporated MHC II and DM and presumably mediated transport to the plasma membrane. We propose that in maturing DCs, the reorganization of MVBs is fundamental for the timing of MHC II antigen loading and transport to the plasma membrane.

Classification and Identification of Enterococci: a Comparative Phenotypic, Genotypic, and Vibrational Spectroscopic Study

Abstract: Rapid and accurate identification of enterococci at the species level is an essential task in clinical microbiology since these organisms have emerged as one of the leading causes of nosocomial infections worldwide. Vibrational spectroscopic techniques (infrared [IR] and Raman) could provide potential alternatives to conventional typing methods, because they are fast, easy to perform, and economical. We present a comparative study using phenotypic, genotypic, and vibrational spectroscopic techniques for typing a collection of 18 Enterococcus strains comprising six different species. Classification of the bacteria by Fourier transform (FT)-IR spectroscopy in combination with hierarchical cluster analysis revealed discrepancies for certain strains when compared with results obtained from automated phenotypic systems, such as API and MicroScan. Further diagnostic evaluation using genotypic methods-i.e., PCR of the species-specific ligase and glycopeptide resistance genes, which is limited to the identification of only four Enterococcus species and 16S RNA sequencing, the "gold standard" for identification of enterococci-confirmed the results obtained by the FT-IR classification. These results were later reproduced by three different laboratories, using confocal Raman microspectroscopy, FT-IR attenuated total reflectance spectroscopy, and FT-IR microspectroscopy, demonstrating the discriminative capacity and the reproducibility of the technique. It is concluded that vibrational spectroscopic techniques have great potential as routine methods in clinical microbiology.

Infection of dendritic cells by murine cytomegalovirus induces functional paralysis.

Abstract: Cytomegalovirus (CMV), measles and HIV are the main human pathogens known to induce immunosuppression. Unlike measles and HIV, and despite the availability of a well studied animal model, little is known about the mechanisms that control CMV-induced immunosuppression. We hypothesized that dendritic cells (DCs), which are crucial in generating and maintaining immune responses, represent a target for CMV and that the transient, but profound, immunosuppression that accompanies CMV infection results from viral interference with DC functions. Here we show that DCs were permissive to murine CMV infection. In addition, DC infection prevented delivery of the signals required for T cell activation. Thus, CMV-mediated impairment of DC function may be crucial for virally induced immunosuppression and interleukin 2 is implicated as a key factor.

Investigating microbial (micro)colony heterogeneity by vibrational spectroscopy.

Abstract: Fourier transform infrared and Raman microspectroscopy are currently being developed as new methods for the rapid identification of clinically relevant microorganisms. These methods involve measuring spectra from microcolonies which have been cultured for as little as 6 h, followed by the nonsubjective identification of microorganisms through the use of multivariate statistical analyses. To examine the biological heterogeneity of microorganism growth which is reflected in the spectra, measurements were acquired from various positions within (micro)colonies cultured for 6, 12, and 24 h. The studies reveal that there is little spectral variance in 6-h microcolonies. In contrast, the 12- and 24-h cultures exhibited a significant amount of heterogeneity. Hierarchical cluster analysis of the spectra from the various positions and depths reveals the presence of different layers in the colonies. Further analysis indicates that spectra acquired from the surface of the colonies exhibit higher levels of glycogen than do the deeper layers of the colony. Additionally, the spectra from the deeper layers present with higher RNA levels than the surface layers. Therefore, the 6-h colonies with their limited heterogeneity are more suitable for inclusion in a spectral database to be used for classification purposes. These results also demonstrate that vibrational spectroscopic techniques can be useful tools for studying the nature of colony development and biofilm formation.

The acquisition of disjunction: Evidence for a grammatical view of scalar implicatures

Abstract: This paper investigates young children's knowledge of scalar implicatures and downward entailment. In previous experimental work, we have shown that young children access the full range of truth-conditions associated with logical words in classical logic, including the disjunction operator, as well as the indefinite article. The present study extends this research in three ways, taking disjunction as a case study. Experiment 1 draws upon the observation that scalar implicatures (SIs) are cancelled (or reversed) in downward entailing (DE) linguistic environments, e.g., in the scope of negation (Chierchia, 2000). Experiment 2 was designed to determine if scalar implicatures are used by children, like adults, to influence the interpretation of disjunction in non-DE contexts, yielding an implicature of exclusivity for disjunction. Whereas adult controls always rejected assertions of the form A or B in positive (non-DE) contexts in which assertions of the form A and B were also true, many children accepted assertions with disjunction in such contexts. To provide an interpretation to the findings from Experiment 2, a new experimental technique was devised and used in Experiment 3. The new technique presents pairs of assertions to children, who are asked to judge which assertion is a ‘better’ description of the context. The findings from Experiment 3 demonstrated children's awareness that A and B is more informative than A or B in positive contexts, where both statements are true. Taken together, the findings of Experiments 2 and 3 are compatible with the view that some children lack the computational resources to apply scalar implicatures when a single assertion is presented alone (see Reinhart, 1999).

Survival and Reproductive Function After Treatment of Malignant Germ Cell Ovarian Tumors

Abstract: PURPOSE: Germ cell ovarian tumors are curable. The possible sequelae of chemotherapy on long-term survivors are still unknown, but these patients may expect normal lives. The aim of this study was to evaluate the outcome and reproductive function in a population of women treated since 1982. MATERIALS AND METHODS: Between 1982 and 1996, 169 women with malignant germ cell ovarian tumors were seen (70 dysgerminomas, 28 endodermal sinus tumors, 24 mixed tumors, and 47 immature teratomas). Seventy-one had advanced or recurrent disease. Fertility-sparing surgery was performed in 138 (81%) women, 81 of whom received postoperative chemotherapy. RESULTS: With a median follow-up of 67 months, the survival rate was 94% for dysgerminoma, 89% for endodermal sinus tumors, 100% for mixed types, and 98% for immature teratoma. For women who were treated conservatively, the survival rate was 98%, 90%, 100%, and 100%, respectively. Two women had adnexal recurrences, and both received salvage treatment. After treatment, all ...

Transcriptional reprogramming of dendritic cells by differentiation stimuli.

Abstract: Immature and mature dendritic cells (DC) have been well characterized functionally and phenotypically. Microorganisms or bacterial products such as lipopolysaccharide (LPS) and inflammatory molecules, including tumor necrosis factor (TNF-α), are both believed to activate the DC maturation program which allows DC to initiate and amplify innate and adaptive immune responses. However, there is increasing evidence that the functional state of DC, induced by different stimuli, may be relevant for the immune response outcome. Thus, we compared the transcriptional program of mature, transitional and immature DC, after either LPS or TNF-α stimulation. GeneChip® oligonucleotide microarrays, representing approximately 6,500 murine genes and ESTs, were used for this analysis. A very diverse modulation of gene expression was observed with the two stimuli. Only LPS-treated cells showed a pattern of expression of genes compatible with a definitive growth arrest and with a suitable activation and control of the immune response.

Blood pressure variability

Abstract: This review deals with a number of issues related to blood pressure variability. These include: historical aspects, with reference to the first pioneering observations; methodological aspects, focusing on the different methods for quantifying blood pressure variability; description of the characteristics of blood pressure variability over the 24 hours; mechanisms involved in determining the different magnitude of this phenomenon in different subjects, such as behavioral factors, central and reflex neural influences, humoral and mechanical factors; blood pressure variability as a probe to assess spontaneous baroreflex sensitivity; effects of aging and hypertension on blood pressure variability, with a discussion of the clinical relevance of this phenomenon in the prognostic evaluation of patients; effects of drugs on blood pressure variability. Finally methodological aspects related to the use of noninvasive ambulatory blood pressure monitoring in the assessment of blood pressure variability are discussed.

Increased glutamate in CSF and plasma of patients with HIV dementia.

Abstract: Background: Experimental evidence suggests that excitotoxicity might play a major role in HIV-induced neurodegeneration. However, few studies have investigated the role of endogenous glutamate in patients with HIV dementia. Objective: To analyze CSF and plasma glutamate levels in 30 patients with AIDS with different dementia severity compared with 10 patients with other neurologic disorders, 11 healthy control subjects, and 10 patients with Alzheimer-type dementia. Methods: CSF and plasma glutamate levels were measured by reverse-phase high-performance liquid chromatography followed by fluorometric analysis. Results: Glutamate CSF levels were increased fivefold in the patients with HIV vs normal control subjects ( p = 0.001), patients with Alzheimer-type dementia ( p p p p p Conclusion: Increased CSF glutamate may originate within the CNS and may play a pathogenetic role in HIV dementia, thus supporting the treatment of these patients with glutamate receptor antagonists.

The HELLAS2XMM survey: I. The X-ray data and the Log(N)-Log(S)

Abstract: We present the first results from an XMM-Newton serendipitous medium-deep survey, which covers nearly three square degrees. We detect a total of 1022, 495 and 100 sources, down to minimum fluxes of about 5.9 x 10^-16, 2.8 x 10^-15 and 6.2 x 10^-15 erg cm^-2 s^-1, in the 0.5-2, 2-10 and 4.5-10 keV band, respectively. In the soft band this is one of the largest samples available to date and surely the largest in the 2-10 keV band at our limiting X-ray flux. The measured Log(N)-Log(S) are found to be in good agreement with previous determinations. In the 0.5-2 keV band we detect a break at fluxes around 5 x 10^-15 erg cm^-2 s^-1. In the harder bands, we fill in the gap at intermediate fluxes between deeper Chandra and XMM-Newton observations and shallower BeppoSAX and ASCA surveys.

Rate dependency of delayed rectifier currents during the guinea-pig ventricular action potential.

Abstract: 1. The action potential clamp technique was exploited to evaluate the rate dependency of delayed rectifier currents (I(Kr) and I(Ks)) during physiological electrical activity. I(Kr) and I(Ks) were measured in guinea-pig ventricular myocytes at pacing cycle lengths (CL) of 1000 and 250 ms. 2. A shorter CL, with the attendant changes in action potential shape, was associated with earlier activation and increased magnitude of both I(Kr) and I(Ks). Nonetheless, the relative contributions of I(Kr) and I(Ks) to total transmembrane current were independent of CL. 3. Shortening of diastolic interval only (constant action potential shape) enhanced I(Ks), but not I(Kr). 4. I(Kr) was increased by a change in the action potential shape only (constant diastolic interval). 5. In ramp clamp experiments, I(Kr) amplitude was directly proportional to repolarization rate at values within the low physiological range ( 1.0 V s(-1) were associated with a reduced effect of I(Kr) block on APD. The effect of changes in repolarization rate was independent of CL and occurred in the presence of I(Ks) blockade. 7. In spite of its complexity, the behaviour of I(Kr) was accurately predicted by a numerical model based entirely on known kinetic properties of the current. 8. Both I(Kr) and I(Ks) may be increased at fast heart rates, but this may occur through completely different mechanisms. The mechanisms identified are such as to contribute to abnormal rate dependency of repolarization in prolonged repolarization syndromes.

Efficient Homolactic Fermentation by Kluyveromyces lactis Strains Defective in Pyruvate Utilization and Transformed with the Heterologous LDH Gene

Abstract: A high yield of lactic acid per gram of glucose consumed and the absence of additional metabolites in the fermentation broth are two important goals of lactic acid production by microrganisms. Both purposes have been previously approached by using a Kluyveromyces lactis yeast strain lacking the single pyruvate decarboxylase gene (KlPDC1) and transformed with the heterologous lactate dehydrogenase gene (LDH). The LDH gene was placed under the control the KlPDC1 promoter, which has allowed very high levels of lactate dehydrogenase (LDH) activity, due to the absence of autoregulation by KlPdc1p. The maximal yield obtained was 0.58 g g−1, suggesting that a large fraction of the glucose consumed was not converted into pyruvate. In a different attempt to redirect pyruvate flux toward homolactic fermentation, we used K. lactis LDH transformant strains deleted of the pyruvate dehydrogenase (PDH) E1α subunit gene. A great process improvement was obtained by the use of producing strains lacking both PDH and pyruvate decarboxylase activities, which showed yield levels of as high as 0.85 g g−1 (maximum theoretical yield, 1 g g−1), and with high LDH activity.

Habitat suitability curves for brown trout (Salmo trutta fario L.) in the River Adda, Northern Italy: comparing univariate and multivariate approaches

Abstract: Habitat suitability of brown trout (Salmo trutta fario) was studied in the upper portion of the Adda River, Northern Italy. Measurements were made for 528 individuals distributed in two life-stage classes, adult and juvenile, based on body length. In order to provide basic biological information for the physical habitat simulation (PHABSIM) system of the instream flow incremental methodology (IFIM) in the Italian regulated rivers, habitat suitability curves (HSCs) have been developed with respect to several microhabitat riverine parameters. Initially, current velocity, water depth, substrate class size and cover were analysed with an univariate approach, then bivariate habitat suitability models were developed from depth and velocity data. The comparison of experimental univariate HSCs with those from the literature outlined some differences that can essentially be explained by characteristics of the investigated river, confirming the necessity of using site-specific curves in relation to each experimental study area. To compare the univariate and bivariate approaches, the weighted usable area (WUA)–discharge relationships were calculated using both types of HSCs. Response curves obtained from the two approaches turned out to be quite different. In PHABSIM habitat modelling, HSCs univariate functions need to be aggregated to produce the WUA–discharge relationship. A multiplicative criterion is generally used for the combined suitability factor; by means of this aggregation criterion all variables have equal weight. According to bivariate models, depth is much more important than velocity in defining habitat suitability requirements. Copyright © 2001 John Wiley & Sons, Ltd.

Development of lung edema: interstitial fluid dynamics and molecular structure.

Abstract: Pulmonary interstitium is maintained dehydrated at subatmospheric pressure (–10 cmH2O) through low capillary permeability, low tissue compliance, and an efficient lymphatic drainage. Enzymatic degr...

Gas-phase reaction of phenol with NO3

Abstract: The fast gas-phase reaction of NO3 radicals with phenol was found to yield 2-nitrophenol as the only relevant nitration product. The yield of this product was high and independent of the concentration of NO2 at the concentrations applied. In the presence of ozone, also significant amounts of 4-nitrophenol and p-benzoquinone were formed. The rate constant of the reaction between NO3 radicals and phenol was determined to be 5.8 x 10(-12) cm3 molecule-1 s-1. The selective formation of 2-nitrophenol (2) is suggested to derive from either the concerted keto-enol tautomerism in the reaction of a phenoxy radical with NO2 or the concerted elimination of nitric acid from a cyclohexa-3,5-diene intermediate.

Cellular automata: from a theoretical parallel computational model to its application to complex system

Abstract: This introductory paper gives a short survey of cellular automata (CAs), from different points of view. It starts with the main definitions and theoretical results about CAs as an abstract model of computation or as discrete dynamical systems. Then, the main applications of CAs in different fields (biology, physics, etc.) as a model of complex systems are illustrated. Finally, implementations of the CA model on parallel computing platforms are surveyed.

Molecular oxygen interaction with Bi2O3: a spectroscopic and spectromagnetic investigation

Abstract: The interaction of molecular oxygen with polycrystalline Bi2O3 was investigated by infrared (IR) and thermogravimetric (TGA) analyses, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The results indicate the formation of “end-on” and “bridging” superoxide species, which are trapped in the β-Bi2O3 vacant oxygen sites, Bi(IV) and Bi(V) centres also being produced. O2− interacts with Bi(IV) centres giving two superoxide adducts with temperature-dependent relative amounts, Bi(IV)–O2− and Bi(IV)–O2−–Bi(III), both having a triplet spin state.

General (Anti-)de Sitter black holes in five dimensions

Abstract: We find a general class of rotating charged black hole solutions to N = 2, D = 5 gauged supergravity coupled to vector supermultiplets. The supersymmetry properties of these solutions are studied, and their mass and angular momenta are obtained. We also compute the stress tensor of the dual D = 4, = 4 super Yang-Mills theory in the limit of strong `t Hooft coupling. It is shown that closed timelike curves occur outside the horizon, indicating loss of unitarity in the dual CFT. For imaginary coupling constant of the gravitini to the gauge fields, one can obtain multi-centered rotating charged de Sitter black holes. Some physical properties of these solutions are also discussed.