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Biomedical subjects

A Riccio

Publications and source records attributed to A Riccio.

At least 19 recordsLinked to original sources
PubMed2006

HCV infection and chronic arthritis: Does viral replication matter?

BACKGROUND: HCV infection beside chronic hepatitis can induce immunological disorders with different clinical expressions such as chronic arthritis. AIM: To study the prevalence of arthritis in HCV-Ab positive patients and verify possible correlation with viral replication, hepatic damage and autoimmunity imbalance. STUDY DESIGN: Three hundred and eighty patients (196 M and 184 F) affected by HCV infection were examined and 38 (10%) were selected according to the presence of arthritis. Eight of them were excluded because arthritis raised before HCV infection. Each patient, once undergone liver biopsy, was evaluated for: clinical examination (articular evolution), Rx examination, serum expression of hepatic damage (mainly ALT), viral replication, and involvement of autoimmunity (ANA, RF, crioglobulins, AKA, CCP). RESULTS: Data from patients [Lamprecht P, Gause A, Gross WL. Cryoglobulinemic vasculitis. Arthritis Rheum 1999; 42:2507-16.] with AKA and CCP positivity were not considered for statistical examination because the clear correlation between rheumatoid arthritis and these parameters. The remaining 20 patients showed hepatic damage 47%, viral replication in 74%, RF 42%, ANA 16%, crioglobulins 42% (RF positive). No correlation was evident between ANA serum concentrations and viral replication; furthermore a significant negative correlation between RF positivity and viral replication only in a subgroup of patients with serologic expression of hepatic damage was found. CONCLUSIONS: These data support hypothesis that the onset of arthritis and presence of autoimmunity parameters ANA, RF are not related to the viral replication but others mechanism immunological induced by HCV might be considered.

Journal Article↗
PubMed2001

Liganded and unliganded forms of Antarctic fish haemoglobins in polyethylene glycol: crystallization of an R-state haemichrome intermediate.

Liganded and unliganded forms of two Antarctic fish haemoglobins, from Trematomus newnesi and T. bernacchii, have been crystallized in low-salt media using polyethylene glycol as precipitant. In particular, crystals of air-exposed T. newnesi carbomonoxy haemoglobin were found to be isomorphous to the crystals grown in high-salt media. Preliminary X-ray analysis of the diffraction data revealed that the beta-haem iron of this haemoglobin is in the haemichrome state, with both the proximal and distal histidyl residues linked to the iron. This is the first crystallization of a haemichrome intermediate of a vertebrate haemoglobin.

Animals↗
PubMed2001

Functional characterization of an ammonium transporter gene from Lotus japonicus.

NH(4)(+) is the main product of symbiotic nitrogen fixation and the external concentration of combined nitrogen plays a key regulatory role in all the different step of plant-rhizobia interaction. We report the cloning and characterization of the first member of the ammonium transporter family, LjAMT1;1 from a leguminous plant, Lotus japonicus. Sequence analysis reveals a close relationship to plant transporters of the AMT1 family. The wild type and two mutated versions of LjAMT1;1 were expressed and functionally characterized in yeast. LjAMT1;1 is transcribed in roots, leaves and nodules of L. japonicus plants grown under low nitrogen conditions, consistent with a role in uptake of NH(4)(+) by the plant cells.

Amino Acid Sequence↗
PubMed2001

Anticardiolipin antibodies in patients with primary antiphospholipid syndrome: a correlation between IgG titre and antibody-induced cell dysfunctions in neuronal cell cultures.

Anticardiolipin antibodies (aCL) of the immunoglobulin (Ig) G isotype have been significantly associated with neurological manifestations of antiphospholipid syndrome (APS). In a previous study we described the direct pathogenic effects of IgG aCL on living neurons in culture. Therefore, we studied the IgG aCL titre as a factor influencing the extent of this effect. Seventeen patients with a history of primary antiphospholipid syndrome were grouped according to their IgG aCL titre into low positive (GPL < or = 40), high positive (40< GPL <100) and very high positive (GPL >100). IgG from these patients were incubated with cerebellar neurons in primary culture for 24h and the effect was evaluated by using the tetrazolium salt (MTT) assay. We found that almost all patients' IgGs reduced cell viability in vitro, but the differences in the extent of the effect were statistically significant only for patients with >40 GPL. Our results reinforce the causal association between increasing level of IgG aCL and clinical features of aPS.

Adult↗
PubMed2001

Molecular dynamics analysis of a second phosphate site in the hemoglobins of the seabird, south polar skua. Is there a site-site migratory mechanism along the central cavity?

Hemoglobin function is modulated by several non-heme ligands; among these effectors, organic phosphates generally bind to heterotropic sites with a one-to-one stoichiometry. The phosphate binding site of human hemoglobin is located at the interface between the two beta chains. An additional binding site for polyanions has been studied at the molecular level (Tamburrini, M., A. Riccio, M. Romano, B. Giardina, and G. di Prisco. 2000. Eur. J. Biochem. 267:6089-6098) in the hemoglobins of the south polar skua (Catharacta maccormicki). It is formed by a cluster of six positive charges of both alpha chains (Val-1, Lys-99, Arg-141); the two Lys-99alpha have an essential role in the site structure. The present investigation, carried out on skua deoxyhemoglobins by using a molecular dynamics approach, confirms the structural feasibility of the additional site, possibly having the role of an entry-leaving site, and leads to the proposal of a novel migration pathway for phosphate along the central cavity of hemoglobin from one binding site to the other, occurring according to the hypothesis of a site-site migratory mechanism, which may assign a functional role to the central cavity. The role of Lys-99alpha was further confirmed by molecular dynamics experiments on the mutant Lys-99alpha-->Ala in which, at the end of the simulation, the phosphate was external to the additional site.

Animals↗
PubMed2001

The Rhizobium etli argC gene is essential for Arginine biosynthesis and nodulation of Phaseolus vulgaris.

A Tn5-induced mutant strain (CTNUX5) of Rhizobium etli unable to grow with ammonium as the sole nitrogen source was isolated and characterized. Sequence analysis showed that Tn5 is inserted into an argC-homologous gene. Unlike its wild-type parent (strain CE3), the mutant strain CTNUX5 had an absolute dependency on arginine to grow. The argC gene was cloned from the wild-type strain CE3, and the resulting plasmid, pAR207, after transformation was shown to relieve the arginine auxotrophy of strain CTNUX5. Unlike strain CE3 or CTNUX5-pAR207, strain CTNUX5 showed undetectable levels of N-acetyl-gamma-glutamylphosphate reductase activity. Unless arginine was added to the growth medium, strain CTNUX5 was unable to produce flavonoid-inducible lipo-chitin oligosaccharides (nodulation factors) and to induce nodules or nodulelike structures on the roots of Phaseolus vulgaris.

Aldehyde Oxidoreductases↗
PubMed2001

The Rhizobium GstI protein reduces the NH4+ assimilation capacity of Rhizobium leguminosarum.

We show that the protein encoded by the glutamine synthetase translational inhibitor (gstI) gene reduces the NH4+ assimilation capacity of Rhizobium leguminosarum. In this organism, gstI expression is regulated by the ntr system, including the PII protein, as a function of the nitrogen (N) status of the cells. The GstI protein, when expressed from an inducible promoter, inhibits glutamine synthetase II (glnII) expression under all N conditions tested. The induction of gstI affects the growth of a glutamine synthetase I (glnA-) strain and a single amino acid substitution (W48D) results in the complete loss of GstI function. During symbiosis, gstI is expressed in young differentiating symbiosomes (SBs) but not in differentiated N2-fixing SBs. In young SBs, the PII protein modulates the transcription of NtrC-regulated genes such as gstI and glnII. The evidence presented herein strengthens the idea that the endocytosis of bacteria inside the cytoplasm of the host cells is a key step in the regulation of NH4+ metabolism.

Bacterial Proteins↗
PubMed2001

Inflammatory and mechanical factors of allergen-induced bronchoconstriction in mild asthma and rhinitis.

We studied whether different bronchial responses to allergen in asthma and rhinitis are associated with different bronchial inflammation and remodeling or airway mechanics. Nine subjects with mild asthma and eight with rhinitis alone underwent methacholine and allergen inhalation challenges. The latter was preceded and followed by bronchoalveolar lavage and bronchial biopsy. The response to methacholine was positive in all asthmatic but in only two rhinitic subjects. The response to allergen was positive in all asthmatic and most, i.e., five, rhinitic subjects. No significant differences between groups were found in airway inflammatory cells or basement membrane thickness either at baseline or after allergen. The ability of deep inhalation to dilate methacholine-constricted airways was greater in rhinitis than in asthma, but it was progressively reduced in rhinitis during allergen challenge. We conclude that 1) rhinitic subjects may develop similar airway inflammation and remodeling as the asthmatic subjects do and 2) the difference in bronchial response to allergen between asthma and rhinitis is associated with different airway mechanics.

Adult↗
PubMed2001

On the functional consequences of bronchial basement membrane thickening.

Reticular basement membrane (RBM) thickness and airway responses to inhaled methacholine (MCh) were studied in perennial allergic asthma (n = 11), perennial allergic rhinitis (n = 8), seasonal allergic rhinitis (n = 5), and chronic obstructive pulmonary disease (COPD, n = 9). RBM was significantly thicker in asthma (10.1 +/- 3.7 microm) and perennial rhinitis (11.2 +/- 4.2 microm) than in seasonal rhinitis (4.7 +/- 0.7 microm) and COPD (5.2 +/- 0.7 microm). The dose (geometric mean) of MCh causing a 20% decrease of 1-s forced expiratory volume (FEV(1)) was significantly higher in perennial rhinitis (1,073 microg) than in asthma (106 microg). In COPD, the slope of the linear regression of all values of forced vital capacity plotted against FEV(1) during the challenge was higher, and the intercept less, than in other groups, suggesting enhanced airway closure. In asthma, RBM thickness was positively correlated (r = 0.77) with the dose (geometric mean) of MCh causing a 20% decrease of FEV(1) and negatively correlated (r = -0.73) with the forced vital capacity vs. FEV(1) slope. We conclude that 1) RBM thickening is not unique to bronchial asthma, and 2) when present, it may protect against airway narrowing and air trapping. These findings support the opinion that RBM thickening represents an additional load on airway smooth muscle.

Adult↗
PubMed2000

The H19 endodermal enhancer is required for Igf2 activation and tumor formation in experimental liver carcinogenesis.

The expression of the linked but reciprocally imprinted Igf2 and H19 genes is activated in adult liver in the course of tumor development. By in situ hybridization analysis we have shown that both the Igf2 and H19 RNAs are expressed in the majority of the neoplastic nodules, and that hepatocellular carcinomas are developed in an experimental model of liver carcinogenesis. H19 is also highly activated in smaller and less distinct hyperplastic regions. The few neoplastic areas showing Igf2 but no H19 RNA display loss of the maternally inherited allele at the Igf2/H19 locus. These data are compatible with the existence of a common activation mechanism of these two genes during liver carcinogenesis and with a stronger H19 induction in the pre-neoplastic lesions. By using mice carrying a deletion of the H19 endodermal enhancer, we show that this regulatory element is necessary for the activation of the Igf2 and H19 genes upon induction of liver carcinogenesis. Furthermore, multiple sites of the H19 endodermal enhancer region become hypersensitive to DNase I when the carcinogenesis process is induced. Lastly, liver tumors developed in mice paternally inheriting the H19 enhancer deletion are found to have marked growth delays, increased frequency of apoptotic nuclei, and lack of Igf2 mRNA expression, thus indicating that this regulatory element plays a major role in the progression of liver carcinogenesis, since it is required for the activation of the anti-apoptotic Igf2 gene.

Animals↗
PubMed2000

Biphasic kinetics of the human DNA repair protein MED1 (MBD4), a mismatch-specific DNA N-glycosylase.

The human protein MED1 (also known as MBD4) was previously isolated in a two-hybrid screening using the mismatch repair protein MLH1 as a bait, and shown to have homology to bacterial base excision repair DNA N-glycosylases/lyases. To define the mechanisms of action of MED1, we implemented a sensitive glycosylase assay amenable to kinetic analysis. We show that MED1 functions as a mismatch-specific DNA N-glycosylase active on thymine, uracil, and 5-fluorouracil when these bases are opposite to guanine. MED1 lacks uracil glycosylase activity on single-strand DNA and abasic site lyase activity. The glycosylase activity of MED1 prefers substrates containing a G:T mismatch within methylated or unmethylated CpG sites; since G:T mismatches can originate via deamination of 5-methylcytosine to thymine, MED1 may act as a caretaker of genomic fidelity at CpG sites. A kinetic analysis revealed that MED1 displays a fast first cleavage reaction followed by slower subsequent reactions, resulting in biphasic time course; this is due to the tight binding of MED1 to the abasic site reaction product rather than a consequence of enzyme inactivation. Comparison of kinetic profiles revealed that the MED1 5-methylcytosine binding domain and methylation of the mismatched CpG site are not required for efficient catalysis.

Base Pair Mismatch↗
PubMed2000

Investigation of the substrate spectrum of the human mismatch-specific DNA N-glycosylase MED1 (MBD4): fundamental role of the catalytic domain.

The human DNA repair protein MED1 (also known as MBD4) was isolated as an interactor of the mismatch repair protein MLH1 in a yeast two-hybrid screening. MED1 has a tripartite structure with an N-terminal 5-methylcytosine binding domain (MBD), a central region, and a C-terminal catalytic domain with homology to bacterial DNA damage-specific glycosylases/lyases. Indeed, MED1 acts as a mismatch-specific DNA N-glycosylase active on thymine, uracil, and 5-fluorouracil paired with guanine. The glycosylase activity of MED1 preferentially targets G:T mismatches in the context of CpG sites; this indicates that MED1 is involved in the repair of deaminated 5-methylcytosine. Interestingly, frameshift mutations of the MED1 gene have been reported in human colorectal, endometrial, and pancreatic cancers. For its putative role in maintaining genomic fidelity at CpG sites, it is important to characterize the biochemical properties and the substrate spectrum of MED1. Here we show that MED1 works under a wide range of temperature and pH, and has a limited optimum range of ionic strength. MED1 has a weak glycosylase activity on the mutagenic adduct 3,N(4)-ethenocytosine, a metabolite of vinyl chloride and ethyl carbamate. The differences in glycosylase activity on G:U and G:T substrates are not related to differences in substrate binding and likely result from intrinsic differences in the chemical step. Finally, the isolated catalytic domain of MED1 retains the preference for G:T and G:U substrates in the context of methylated or unmethylated CpG sites. This suggests that the catalytic domain is fundamental, and the 5-methylcytosine binding domain dispensable, in determining the substrate spectrum of MED1.

Base Pair Mismatch↗
PubMed2000

Inhibition of glutamine synthetase II expression by the product of the gstI gene.

We report the identification of a previously unrecognized gene that is involved in the regulation of the Rhizobium leguminosarum glnII (glutamine synthetase II) gene. This gene, which is situated immediately upstream of glnII, was identified by means of a deletion/complementation analysis performed in the heterologous background of Klebsiella pneumoniae. It has been designated gstI (glutamine synthetase translational Inhibitor) because, when a complete version of gstI is present, it is possible to detect glnII-specific mRNA, but neither GSII activity nor GSII protein. The gstI gene encodes a small (63 amino acids) protein, which acts in cis or in trans with respect to glnII and is transcribed divergently with respect to glnII from a promoter that was found to be strongly repressed by the nitrogen transcriptional regulator NtrC. A mutated version of GstI lacking the last 14 amino acids completely lost its capacity to repress glnII expression. Our results indicate that gstI mediates the translation inhibition of glnII mRNA and, based on in silico analyses, a mechanism for GstI action is proposed.

Amino Acid Sequence↗
PubMed2000

Structural and functional analysis of the two haemoglobins of the antarctic seabird Catharacta maccormicki characterization of an additional phosphate binding site by molecular modelling.

The amino-acid sequence and the oxygen-binding properties of the two haemoglobins of the Antarctic seabird south polar skua have been investigated. The two haemoglobins showed peculiar functional features, which were probably acquired to meet special needs in relation to the extreme environmental conditions. Both haemoglobins showed a weak alkaline Bohr effect which, during prolonged flight, may protect against sudden and uncontrolled stripping of oxygen in response to acidosis. We suggest that a weak Bohr effect in birds may reflect adaptation to extreme life conditions. The values of heat of oxygenation suggest different functional roles of the two haemoglobins. The experimental evidence suggests that both haemoglobins may bind phosphate at two distinct binding sites. In fact, analysis of the molecular models revealed that an additional phosphate binding site, formed by residues NA1alpha, G6alpha and HC3alpha, is located between the two alpha chains. This additional site may act as an entry/leaving site, thus increasing the probability of capturing phosphate and transferring it to the main binding site located between the two beta chains by means of a site-site migratory mechanism, thereby favouring the release of oxygen. It is suggested that most haemoglobins possess an additional phosphate binding site, having such a role in oxygen transport.

Adaptation, Physiological↗
PubMed2000

Relaxation of insulin-like growth factor 2 imprinting and discordant methylation at KvDMR1 in two first cousins affected by Beckwith-Wiedemann and Klippel-Trenaunay-Weber syndromes.

Beckwith-Wiedeman syndrome (BWS) and Klippel-Trenaunay-Weber syndrome (KTWS) are different human disorders characterized, among other features, by tissue overgrowth. Deregulation of one or more imprinted genes located at chromosome 11p15.5, of which insulin-like growth factor 2 (IGF2) is the most likely candidate, is believed to cause BWS, whereas the etiology of KTWS is completely obscure. We report a case of BWS and a case of KTWS in a single family. The probands, sons of two sisters, showed relaxation of the maternal IGF2 imprinting, although they inherited different 11p15.5 alleles from their mothers and did not show any chromosome rearrangement. The patient with BWS also displayed hypomethylation at KvDMR1, a maternally methylated CpG island within an intron of the KvLQT1 gene. The unaffected brother of the BWS proband shared the same maternal and paternal 11p15.5 haplotype with his brother, but the KvDMR1 locus was normally methylated. Methylation of the H19 gene was normal in both the BWS and KTWS probands. Linkage between the insulin-like growth factor 2 receptor (IGF2R) gene and the tissue overgrowth was also excluded. These results raise the possibility that a defective modifier or regulatory gene unlinked to 11p15.5 caused a spectrum of epigenetic alterations in the germ line or early development of both cousins, ranging from the relaxation of IGF2 imprinting in the KTWS proband to disruption of both the imprinted expression of IGF2 and the imprinted methylation of KvDMR1 in the BWS proband. Analysis of these data also indicates that loss of IGF2 imprinting is not necessarily linked to alteration of methylation at the KvDMR1 or H19 loci and supports the notion that IGF2 overexpression is involved in the etiology of the tissue hypertrophy observed in different overgrowth disorders, including KTWS.

3' Untranslated Regions↗
PubMed2000

Nodule invasion and symbiosome differentiation during Rhizobium etli-Phaseolus vulgaris symbiosis.

By means of a detailed ultrastructural analysis of nodules induced by Rhizobium etli on the roots of Phaseolus vulgaris, we observe that the development of host-invaded cells is not synchronous. An accumulation of mitochondria was found in freshly invaded host cells, containing only a few symbiosomes (SBs) that are released from highly branched intracellular ramification of the infection threads. Moreover, besides the fusion between the SB membrane with host secretory vesicles, we observe also a great number of fusions between the outer leaflets of adjoining SB membranes, thus resulting in structures that resemble the tight junction network (zona occludens with a five-layered structure) of epithelian cells. This process was found to be induced strongly and earlier both in the invaded host cells of ineffective nodules (elicited by Fix- mutant strains of R. etli) and in the older (senescence) invaded cells of effective nodules, whereas bacteroid division is seldom if ever observed. Our observations strongly suggest that multiple-occupancy SBs also arise by fusion of single-occupancy SBs and the physiological consequence of this process is discussed.

Cell Differentiation↗
PubMed2000

Spatial considerations for stimulus-dependent transcription in neurons.

Most neurons have elaborate dendrites as well as an axon emanating from the cell body that form synaptic connections with one or many target cells, which may be located a considerable distance from the cell body. Such complex and impressive morphologies allow some types of neurons to integrate inputs from one to many thousands of pre-synaptic partners and to rapidly propagate electrical signals, often over long distances, to post-synaptic target cells. Much slower, non-electrical signals also propagate from dendrites and distal axons to neuronal nuclei that influence survival, growth, and plasticity. The distances between distal dendrites and/or distal axons and cell bodies of neurons can be hundreds of microns to more than one meter. This long-range biochemical signal propagation from distal dendrites and distal axons to neuronal nuclei is entirely unique to neurons. This review is focused on excitatory neurotransmitter signaling from dendritic synapses to neuronal nuclei as well as on retrograde growth factor signaling from distal axons to neuronal nuclei.

Animals↗