PubMed Health⌕ Search

Biomedical subjects

R Siciliano

Publications and source records attributed to R Siciliano.

At least 19 recordsLinked to original sources
PubMed2002

Electrical impedance tomography via filtered-back projection of fan current distribution: a numerical simulation.

An approach to electrical impedance tomography (EIT) data acquisition inspired by NMR-filtered back-projection imaging with fan isochromat distribution is proposed. A current projection is generated by injecting current at a certain point of the sample and simultaneously collecting the current itself at different points on the half space opposite the point of current injection. After that, the injection is shifted to another point and collected as above and so on. A very simple algebra and software support the numerical simulations. This method is expected to be more sensitive than the traditional method based on potential measurements. A preliminary low resolution experiment is presented.

Algorithms↗
PubMed2001

Involvement of bovine lactoferrin metal saturation, sialic acid and protein fragments in the inhibition of rotavirus infection.

Although the antiviral activity of lactoferrin is one of the major biological functions of this iron binding protein, the mechanism of action is still under debate. We have investigated the role of metal binding, of sialic acid and of tryptic fragments of bovine lactoferrin (bLf) in the activity towards rotavirus (intestinal pathogen naked virus) infecting enterocyte-like cells. The antiviral activity of bLf fully saturated with manganese or zinc was slightly decreased compared to that observed for apo- or iron-saturated bLf. The antiviral activity of differently metal-saturated bLf towards rotavirus was exerted during and after the virus attachment step. The removal of sialic acid enhanced the anti-rotavirus activity of bLf. Among all the peptidic fragments obtained by tryptic digestion of bLf and characterised by advanced mass spectrometric methodologies, a large fragment (86-258) and a small peptide (324-329: YLTTLK) were able to inhibit rotavirus even if at lower extent than undigested bLf.

Antiviral Agents↗
PubMed2000

Beta-casomorphins: substitution of phenylalanine with beta-homo phenylalanine increases the mu-type opioid receptor affinity.

Two analogues of bovine beta-casomorphin-7 and beta-casomorphin-5 containing a beta-homo phenylalanine in substitution of the phenylalanine in position 3 were synthesised and tested for their mu-opioid receptor affinity. The modification enhanced the mu receptor affinity 5-fold in the case of modified beta-CM-7 and 2-fold for modified beta-CM-5 when compared to the natural peptides.

Amino Acid Sequence↗
PubMed2000

Modern mass spectrometric methodologies in monitoring milk quality.

Structural modifications induced by industrial treatments on milk proteins have been investigated using a new analytical protocol based on mass spectrometric procedures (electrospray and matrix assisted laser desorption ionization mass spectrometry) providing a direct correlation between the severity of the treatment and the damages observed. The application of this procedure to the analysis of whey proteins from milk samples submitted to different thermal processes confirmed that under these conditions protein modification is essentially due to the nonenzymatic glycation of amino groups by lactose (Maillard reaction). A detailed structural investigation of the modification sites, carried out by the mass mapping strategy, revealed the occurrence of preferentially lactosylated sites in both alpha-lactalbumin and beta-lactoglobulin.

Animals↗
PubMed2000

N-Linked glycans of proteins from mitral valves of normal pigs and pigs affected by endocardiosis.

Endocardiosis, a degenerative and dystrophic process affecting cardiac valves and described in many mammalian species, is characterized by the accumulation of glycosaminoglycans, in particular hyaluronic acid, in the extracellular matrix. The glycoprotein patterns of pig mitral valves in normal animals and animals affected by endocardiosis were investigated. A different N-linked glycosylation pattern of glycoproteins was detected in affected valves compared with normal ones. In either normal or pathological species, the detected N-linked glycans were of the complex type. However, in samples from affected valves, sialic acid showed a prevalence of the alpha2,6 linkage to the galactosyl residue, whereas in normal samples the most frequent linkage was of the alpha2,3 type. In normal valves, the majority of complex oligosaccharides presented two outer branches with different degrees of fucosylation and sialylation, whereas in pathological samples we noted an increased number of glycans having up to four outer branches.

Animals↗
PubMed2000

Structural analysis of modified forms of recombinant IFN-beta produced under stress-simulating conditions.

The present study focused on the investigation of the chemical stability of recombinant human interferon-beta (rhIFN-beta) tested in vitro by chemical treatments that simulate stress-induced conditions that may occur during handling, storage or ageing of protein samples. Mild oxidation and/or alkylation of the recombinant protein showed that the four methionines occurring in the interferon displayed different chemical susceptibility in that Met36 and Met117 were fully modified, whereas Met1 showed only little modification and Met62 was completely resistant. Moreover, incubation of rhIFN-beta under alkaline conditions resulted in the formation of a covalent dimeric species stabilised by an intermolecular disulphide bridge involving the free SH group of Cys17 from each polypeptide chain. Analysis of biological activity of the different IFN-beta derivatives showed that rhIFN-beta fully retains its specific activity following mild oxidation treatments whereas reaction with a high concentration of alkylating agents or incubation under alkaline conditions strongly reduce its specific antiviral activity.

Antiviral Agents↗
PubMed1999

Bovine lactoferrin peptidic fragments involved in inhibition of herpes simplex virus type 1 infection.

Bovine lactoferrin (BLf) prevents the infection of some enveloped and naked viruses. To identify BLf sequences responsible for the antiviral activity, we tested 31 HPLC fractions, derived from tryptic digestion of BLf, toward herpes simplex virus type 1 (HSV-1). Only a few HPLC purified fragments were active against HSV-1, even if at lower extent than the native undigested BLf. Two large fragments, one corresponding to the C-lobe (amino acid sequence 345-689) and the other corresponding to a large portion of the N-lobe (1-280), were inhibitors of HSV-1 infection, while a smaller part of the N-lobe (86-258) was ineffective. Among the low-molecular-weight fragments, only two small peptides, which coeluted in a single chromatographic peak, were effective towards HSV-1. These peptides, both present in the N-lobe, were identified as peptides 222-230 (ADRDQYELL) and 264-269 (EDLIWK). The same peptides, chemically synthesised, were able to inhibit HSV-1 infection only when they were assayed in association.

Animals↗
PubMed1999

Long-term response to interferon alpha is unrelated to "interferon sensitivity determining region" variability in patients with chronic hepatitis C virus-1b infection.

BACKGROUND/AIMS: Contradictory data have been reported about the predictive value of the variability in interferon sensitivity determining region (ISDR) of hepatitis C virus (HCV) genotype-1b on response to interferon-alpha (IFN-alpha) therapy. The aim of this study was to examine this issue in a series of patients with long-term response to IFN treatment. METHODS: We retrospectively analyzed 24 patients with chronic HCV genotype-1b infection treated with IFN-alpha (total dose median 677, range 216-1350 MU) selected in 6 Italian Liver Units. These patients were defined as true long-term responders (LTR) since they showed persisting biochemical and virological responses to IFN treatment (mean follow-up 38 months). HCV genomes from pretreatment serum samples were amplified and directly sequenced. The ISDR amino-acid sequences obtained were aligned and compared with the published sequence of HCV-J. RESULTS: Amino-acid substitutions were found in 23 of the 24 patients, and 22 of them showed an H to R amino-acid change at codon 2218. Fourteen patients showed only one mutation (at codon 2218), two had 2, five had 3, one had 4 and one had 5 mutations. When we compared the ISDR sequences from the 24 LTR with those of non-responders (NR), we found no significant correlation between the number of mutations and the response to therapy. CONCLUSIONS: Our results demonstrate that the persisting efficacy of IFN treatment in patients with chronic HCV is not related to the number of ISDR amino acid substitutions of the infecting viruses. Further studies are needed to verify whether other NS5A sequences outside the ISDR might be involved in the mechanisms of IFN resistance.

Adult↗
PubMed1997

Tachykinins and other biologically active peptides from the skin of the Costa Rican phyllomedusid frog Agalychnis callidryas.

Peptides present in a methanol extract prepared from skin of the Costa Rican frog Agalychnis callidryas of the Phyllomedusinae subfamily were studied by sequence analysis and pharmacological tests. Members of five different peptide families-tachykinins, bradykinins, caerulein, opioid peptides and sauvagine-were found. In particular, the extract contained a number of tachykinins with the following sequences: Gly-Pro-Pro-Asp-Pro-Asn-Lys-Phe-Ile-Gly-Leu-Met-NH2, Gly-Pro-Pro-Asp-Pro-Asp-Arg(Lys)-Phe-Tyr-Pro-Gly-Met-NH2, pGlu-Pro-Asp-Pro-Asp-Arg-Phe-Tyr-Pro-Gly-Met-NH2, Gly-Pro-Pro-Asp-Pro-Asn-Lys-Phe-Tyr-Pro-Val-Met. The latter three peptides have the unusual C-terminal sequence Pro-Gly(or Val)-Met-NH2 rather than Gly-Leu-Met-NH2 found in many other members of the tachykinin family. The observed amino acid substitutions may be the reason for the marked decrease in the biological activity observed in all in vitro and in vivo tests, even through the spectrum of tachykinin activities was retained. A kassinin-like peptide, with the sequence Gly-Pro-Pro-Asp-Pro-Asn-Lys-Phe-Ile-Gly-Leu-Met-NH2, was also found in the A. callidryas skin. While kassinin has a much higher affinity for NK-3 than for NK-1 receptors, the opposite is true for this A. callidryas peptide. The extract from A. callidryas skin also contained a new caerulein (pGlu-Asp-Tyr(HSO3)-Lys-Gly-Trp-Met-Asp-Phe-NH2) and a phyllokinin (Arg-Pro-Hyp-Gly-Phe-Ser-Pro-Phe-Arg-Ile-Tyr), as well as the opioid peptides dermorphin and [Hyp6]dermorphin, both previously isolated from different Phyllomedusa species.

Animals↗
PubMed1996

Structural characterisation of human recombinant glycohormones follitropin, lutropin and choriogonadotropin expressed in Chinese hamster ovary cells.

The alpha and beta chains from human recombinant gonadotropins follitropin, lutropin and choriogonadotropin expressed in CHO cells have been structurally characterised both at the protein and at the carbohydrate level by using advanced mass spectrometric procedures. The three alpha chains share the same amino acid sequence while they display different glycosylation patterns. The oligosaccharide structures detected belong to the complex-type glycans with different degree of sialylation. Partial proteolytic processing occurred at the N-terminus of the follitropin beta chain and at the C-terminus of the lutropin beta chain. The N-linked glycans from the three beta chains were found to contain fucosylated and sialylated diantennary and triantennary complex-type structures. The follitropin beta chain showed the presence of N-acetyllactosamine repeats on the antennae. The overall structure of the recombinant glycohormones corresponds to their natural counterparts with the exception that sulphated terminal glycosylation is missing.

Amino Acid Sequence↗
PubMed1996

The gene, protein and glycan structures of laccase from Pleurotus ostreatus.

A member of the laccase multigene family in Pleurotus ostreatus has been cloned and sequenced. The gene structure has been determined by comparison with the corresponding cDNA, synthesized by reverse transcription/PCR amplification. The gene encode a laccase isoenzyme of 533 amino acids which has already been purified and characterized [Palmieri, G., Giardina, P., Marzullo, L., Desiderio, B., Nitti, G., Cannio, R. & Sannia, G.(1993) Appl. Microbiol. Biotechnol. 39, 632-636]. More than 92% of the protein sequence, including the N and C termini, has been verified by fast-atom-bombardment mass spectrometry, thus confirming the correspondence between the gene and its protein product. The protein was N-glycosylated Asn444. Glycan analysis showed the presence of only a high-mannose structure containing varying numbers of mannose residues. The presence of O-linked oligosaccharides as well as other post-translational modification could be ruled out by the mass analysis.

Amino Acid Sequence↗
PubMed1996

Mapped auditory evoked potentials before and after interferon treatment.

Neurotoxicity induced by interferon (IFN) is revealed by neurobehavioral changes, such as irritability, somnolence, lack of motivation, and delayed ideation. As these side effects persist throughout IFN-alpha treatment, we studied cerebral mapped auditory evoked potentials (MAEP) in 20 hepatitis C virus antibody (HCV Ab)-positive chronic active hepatitis patients before and after administration of leukocyte IFN-alpha (i.m. 3,000,000 IU). Some of the main components of MAEP, such as morphology, latency, and power spectra, were altered before IFN injection. These parameters changed 7 h after administration as revealed by increased quality and quantity of acoustic signal reaching the brain cortex and appearance of physiologic waves in patients with mild/intermediate liver disease. These effects revealed 48 h after IFN administration.

Adult↗
PubMed1995

Structural analysis of saposin C and B. Complete localization of disulfide bridges.

Saposins A, B, C, and D are a group of homologous glycoproteins derived from a single precursor, prosaposin, and apparently involved in the stimulation of the enzymatic degradation of sphingolipids in lysosomes. All saposins have six cysteine residues at similar positions. In the present study we have investigated the disulfide structure of saposins B and C using advanced mass spectrometric procedures. Electrospray analysis showed that deglycosylated saposins B and C are mainly present as 79- and 80-residue monomeric polypeptides, respectively. Fast atom bombardment mass analysis of peptide mixtures obtained by a combination of chemical and enzymatic cleavages demonstrated that the pairings of the three disulfide bridges present in each saposin are Cys4-Cys77, Cys7-Cys71, Cys36-Cys47 for saposin B and Cys5-Cys78, Cys8-Cys72, Cys36-Cys47 for saposin C. We have recently shown that saposin C interacts with phosphatidylserine-containing vesicles inducing destabilization of the lipid surface (Vaccaro, A. M., Tatti, M., Ciaffoni, F., Salvioli, R., Serafino, A., and Barca, A. (1994) FEBS Lett. 349, 181-186); this perturbation promotes the binding of the lysosomal enzyme glucosylceramidase to the vesicles and the reconstitution of its activity. It was presently found that the effects of saposin C on phosphatidylserine liposomes and on glucosylceramidase activity are markedly reduced when the three disulfide bonds are irreversibly disrupted. These results stress the importance of the disulfide structure for the functional properties of the saposin.

Amino Acid Sequence↗
PubMed1992

Parvalbumin immunoreactivity: a reliable marker for the effects of monocular deprivation in the rat visual cortex.

In mammals, monocular deprivation performed during the early stages of postnatal development (critical period) dramatically affects the functional organization of the visual cortex. Since the early work of Hubel and Wiesel, the effects of monocular deprivation are accounted for by the fibers driven by the two eyes competing for the control of cortical territories. In cat and monkey striking structural changes accompany the functional effects of monocular deprivation. Also, in the rat, monocular deprivation causes functional alteration at the level of visual cortex; no structural correlates of these effects, however, have so far been described. Parvalbumin is a calcium binding protein that in the neocortex colocalizes with a subpopulation of GABAergic neurons. Here we report that in the rat monocular deprivation results in a dramatic reduction of parvalbumin-like immunoreactivity in the visual cortex contralateral to the deprived eye. This effect is due to competitive phenomena and not to visual deprivation itself, it is restricted to the binocular portion of the visual cortex and neither binocular deprivation, nor dark rearing can induce it. We conclude that parvalbumin-like immunoreactivity is a useful immunohistochemical marker for the effects of monocular deprivation in the rat visual cortex.

Animals↗
PubMed1991

Human alpha-fetoprotein primary structure: a mass spectrometric study.

The amino acid sequence of human alpha-fetoprotein, a 67-kDa protein present in mammalian embryonic serum, was verified by fast atom bombardment mass spectrometric (FAB/MS) analyses of three different enzymatic digests of the protein. Human alpha-fetoprotein obtained from a large-scale cell culture was digested with trypsin and V-8 protease either separately on two different samples or combined on the same one. The V-8 protease digest of the protein was partially fractionated by HPLC; the other samples were directly analyzed by FAB/MS without previous purification steps. About 90% of the alpha-fetoprotein amino acid sequence was verified by mass spectrometric analysis; this also confirmed that the cell-derived protein is identical with the hepatoma-derived protein. FAB analysis revealed that the N terminus of the mature protein is arginine rather than threonine, with the threonine occupying the second position. Therefore, the processing site of the alpha-fetoprotein signal peptide during maturation of the protein occurs at the N-terminal side of the arginine residue formerly indicated as residue-1. Thus mature alpha-fetoprotein contains 591 amino acids rather than 590.

Amino Acid Sequence↗
PubMed1991

Mass spectrometric identification of the amino donor and acceptor sites in a transglutaminase protein substrate secreted from rat seminal vesicles.

Four different transglutaminase-modified forms of a protein secreted by the rat seminal vesicles (SV-IV) were synthesized in vitro and characterized. FAB maps of both the native protein and its derivatives, produced by the purified guinea pig liver enzyme in the presence or absence of the polyamine spermidine, were obtained by mass spectrometric analysis after proteolytic digestions. Two differently derivatized SV-IV molecular forms, both possessing only one glutamine residue out of two (Gln-86) cross-linked to endogenous lysine residues, were produced when spermidine was omitted from the reaction mixture: (i) an insoluble homopolymer in which Lys-2, -4, -59, -78, -79, and -80 were involved in the linkage; (ii) a soluble form of the protein with an intramolecular epsilon-(gamma-glutamyl)lysine isopeptide bond between Gln-86 and Lys-59. Two species of SV-IV-spermidine adducts were obtained when the protein was treated with transglutaminase in the presence of high concentrations of the polyamine. The first one was characterized by one spermidine molecule covalently bound to Gln-86 and the second one by two spermidine molecules respectively bound to Gln-9 and Gln-86.

Amino Acid Sequence↗
PubMed1991

Further analysis of the sequence of the S1 subunit of pertussis toxin.

The two published sequences of the pertussis toxin operon differ in 3 bp in the S1 subunit gene. In this report, we provide evidence that Bordetella pertussis strains are able to produce active pertussis toxin only when they contain one of the two possible nucleotide sequences.

Amino Acid Sequence↗