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Biomedical subjects

M Simonetti

Publications and source records attributed to M Simonetti.

At least 19 recordsLinked to original sources
PubMed2006

Endothelial cell function on 2D and 3D micro-fabricated polymer scaffolds: applications in cardiovascular tissue engineering.

Polymeric structures of a polylactide-polycaprolactone blend were micro-fabricated using the Pressure Assisted Microsyringe (PAM) system. Human umbilical vein endothelial cells were cultured on the scaffolds, and apoptosis, cell adhesion, proliferation and metabolism were evaluated. In addition, more specific indicators of endothelial cell function, namely nitric oxide and endothelin production, were also assessed. Thin films of the blend, as well as gelatine-coated glass slides (as controls) were used. The results show that as far as adhesion, apoptosis and metabolism are concerned, the scaffolds do not interfere with cell function compared with gelatin controls. However, the nitric oxide/endothelin ratio was higher than that observed on the gelatin films, suggesting that the scaffolds could be used for engineering small diameter blood vessels without risk of occlusion.

Cardiovascular System↗
PubMed2001

New Fourier transform infrared based computational method for peptide secondary structure determination. I. Description of method.

Fourier transform infrared (FTIR) experiments in dimethylsulfoxide, a solvent incapable of H donation, demonstrate that H --> D isotopic replacement on the amide side of peptide bonds involves modifications of both the position and intensity of the amide I band. The effect of the isotopic substitution is particularly significant in the 1710-1670 and 1670-1650 cm(-1) regions, which are generally associated with beta-turns and alpha-helices. This behavior, attributed to the existence of intramolecular H-bonds in the polypeptide chain, is directly correlated to the presence of different secondary structures. Utilizing the effects induced by isotopic substitution, a method for the quantitative determination of the percentage of intramolecular H-bonds and the correlated secondary structures is proposed. The method consists of three principal steps: resolution of the fine structure of the amide I band with the determination of the number and position of the different components; reconstruction of the experimentally measured amide I band as a combination of Gaussian and Lorentzian functions, centered on the wave numbers set by band-narrowing methods, through a curve-fitting program; and quantitative determination of the population of the H-bonded carbonyls and the correlated secondary structures by comparison of the integrated intensities pertaining to the components with homologous wave numbers before and after isotopic exchange. The method is tested on a synthetic fragment of proocytocin that was previously analyzed by NMR techniques using the same solvent systems.

Deuterium↗
PubMed2001

New Fourier transform infrared based computational method for peptide secondary structure determination. II. Application to study of peptide fragments reproducing processing site of ocytocin-neurophysin precursor.

A new method for the quantitative determination of the percentage of intramolecular H-bonds, based on Fourier transform infrared techniques, is applied to the conformational analysis of a series of synthetic peptides spanning the processing site of the ocytocin and neurophysin precursor. Even though the method uses traditional tools such as Fourier self-deconvolution, the Nth derivative, and curve-fitting procedures for the analysis of the spectra, the assignment of the absorptions due to peptide groups participating into secondary structures is based on the direct observation and quantification of the isotopic effect induced on the groups participating in intramolecular H-bonds in the presence of organic solvents. This permits the quantification of the different populations of molecules containing intramolecular H-bonds involved in beta-turns and alpha-helices. The results are consistent with those previously obtained by NMR techniques in the same solvent systems.

Animals↗
PubMed2000

Favourable side-chain orientation of cleavage site dibasic residues of prohormone in proteolytic processing by prohormone convertase 1/3.

Previous studies using selectively modified pro-ocytocin/neurophysin substrate analogues and the purified metalloprotease, pro-ocytocin/neurophysin convertase (magnolysin; EC 3.4 24.62), have shown that dibasic cleavage site processing is associated with a prohormone sequence organized in a beta-turn structure. We have used various peptide analogues of the pro-ocytocin-neurophysin processing domain, and recombinant prohormone convertase 1/3, to test the validity of this property towards this member of the family of prohormone convertases (PCs). The enzymatic cleavage analysis and kinetics showed that: (a) with methyl amide (N-Met) modification, a secondary structure beta-turn breaker, the enzyme substrate interaction was abolished; (b) cleavage was favoured when the dibasic substrate side-chains were oriented in opposite directions; (c) the amino acid present at the P'1 position is important in the enzyme-substrate interaction; (d) the flexibility of the peptide substrate is necessary for the interaction; (e) Addition of dimethylsulfoxide to the cleavage assay favoured the cleavage of the pro-ocytocin/neurophysin large substrate over that of the smaller one pGlu-Arg-Thr-Lys-Arg-methyl coumarin amide. These data allowed us to conclude that proteolytic processing of pro-ocytocin-related peptide substrates by PC1/3 as well as by the metalloenzyme, magnolysin, involves selective recognition of precise cleavage site local secondary structure by the processing enzyme. It is hypothesized that this may represent a general property of peptide precursor proteolytic processing systems.

Amino Acid Sequence↗
PubMed2000

Aldicarb poisoning.

Aldicarb (2-methyl-2(methylthio) propanal o-[(methylamino)-carbonyl] oxime) is a pesticide manufactured since 1965. This carbamate ester is sold under the tradename, Temik, and is used as insecticide and nematicide. The Environmental Protection Agency has classified aldicarb in the highest toxicity category and has defined a strict control for its delivery and use. In Brazil and the Caribbean island, aldicarb is illegally used as a household rodenticide with a widespread risk of poisoning. Our study presents the first review of aldicarb poisoning circumstances associated with clinical and analytical findings. Moreover, the oxime treatment is discussed. Eighteen patients with cholinergic symptoms admitted to the Emergency Unit and two deceased with a history of aldicarb poisoning were included in the study. As agricultural workers, only two of them could legally use Temik. Seventy percent of the patients was managed by the Emergency Mobil Unit. Serum cholinesterase activity was always lower than 30% of the normal range and aldicarb was identified by UV spectra and retention time after liquid chromatography separation. The most common muscarinic effect was diarrhea, the main nicotinic sign fasciculation and almost half of the poisoned patients had central nervous system (CNS) depression (Glasgow Coma Score lower than 8). Four patients had serious conduction abnormalities and two of them died. These results suggest that aldicarb intoxication is always severe. Oxime treatment did not produce side effects and should be recommended whenever the pesticide involved is unknown. Effective measures should be implemented to stamp out the illicit use of aldicarb.

Adolescent↗
PubMed1998

A conformational study in solution of pro-somatostatin fragments by NMR and computational methods.

The results of a conformational study by nuclear magnetic spectroscopy and computational methods on a series of point-mutated synthetic peptides, containing 14 amino acid residues and mimicking the region containing the Arg-Lys dibasic cleavage site of pro-somatostatin, have confirmed the possible role of a well defined secondary structure in the recognition phenomenon by processing enzymes. The importance of the residues located near the Arg-Lys dibasic site in the C-terminal region of the pro-hormone for the cleavage of the precursor into somatostatin-14 has been confirmed. The present structural analysis indicates the occurrence of two beta-turns in the 4-7 and 11-14 regions, flanking the cleavage site, for all the peptides recognized as substrates by the processing enzyme. Interestingly, in the point-mutated analogue not processed by the enzyme and containing the replacement of proline by alanine in position 5 the first -turn is displaced by one residue and involves the Ala5-Arg8 segment. This observation may explain the lack of recognition by the maturation enzyme.

Amino Acid Sequence↗
PubMed1998

[Home oxygen therapy in children with chronic respiratory failure].

BACKGROUND: Home oxygen therapy improves survival and quality of life in adults with chronic obstructive airways disease. The few studies about home oxygen therapy in children show improvements in weight gain, school performance and decreases in hospitalization expenses. AIM: To report our experience in home oxygen therapy in children followed for six months to four years. PATIENTS AND METHODS: Fifty five children, less than 15 years old, discharged from a University hospital with the diagnosis of chronic respiratory failure, were followed up at their homes. RESULTS: Discharge diagnoses were bronchopulmonary dysplasia in 36% of children, postinfectious pulmonary damage in 22%, neonatal distress in 13%, chronic aspiration in 9%, cystic fibrosis in 7% and miscellaneous in 13%. Forty six completed at least 6 months of follow up, five moved to other hospitals, three required ventilatory support and one died. Oxygen was discontinued in 33 patients, and this occurred before the ninth month of follow up in 88% of those children. Neonatal distress and bronchopulmonary dysplasia had the best prognoses, and oxygen was discontinued at 4 +/- 1 and 5.7 +/- 3 months respectively. Patients with postinfectious pulmonary disease had a higher incidence of bronchoneumoniae, and those with bronchopulmonary dysplasia a higher incidence of acute bronchiolitis, that motivated hospital admissions. Expenses due to home oxygen were lower than hospitalization costs. No adverse effects were detected. CONCLUSIONS: Infants and newborns on home oxygen therapy have a good prognosis, specially those with reversible diseases. This type of therapy allows an earlier hospital discharge with considerable cost reductions.

Child↗
PubMed1997

CD conformational studies on synthetic peptides encompassing the processing domain of the ocytocin/neurophysin precursor.

Synthetic peptides of different size, reproducing the proteolytic processing site of proocytocin, were studied by CD under several experimental conditions in order to ascertain the ability of different solvents to stabilize secondary structural motifs, such as alpha-helix tracts and beta-turns. A combination of deconvolution methods and empirical calculations subtracting the contributions due to unordered structures from the spectra suggests that in solution (a) mainly two distinct families of ordered conformers containing structurally different beta-turns are present, (b) the relative stability of the different conformers depends from the nature of the solvent, and (c) in the case of the larger peptides, a population containing an alpha-helical conformation is also present. From the biological point of view the presence of at least two families of ordered conformers could be in line with current theories assuming that the catalytic effect of the receptor microenvironment may be determinant in shifting the equilibrium toward the active conformation.

Amino Acid Sequence↗
PubMed1996

NMR conformational studies on a synthetic peptide reproducing the [1-20] processing domain of the pro-ocytocin-neurophysin precursor.

The combined use of several nuclear magnetic resonance and restrained molecular dynamics techniques allowed the formulation of a molecular model for the preferred solution conformation of a synthetic peptide reproducing the [1-20] processing domain of the pro-ocytocin-neurophysin precursor. In the model, the conformation of the 20-membered tocin ring, with the two Cys1 and Cys6 residues bridged by a disulphide bond, is very close to that observed for isolated ocytocin in the solid state; in addition, a type II beta-turn is postulated for the 7-10 segment of the acyclic tail containing the Lys11-Arg12 processing site, and connecting ocytocin to the neurophysin domain, while the C-terminal 13-20 segment of the molecule is believed to assume a helical structure. This particular structural organization could be important in participating as the favorable conformation for optimal substrate-enzyme active site recognition and processing by specific endoproteases.

Amino Acid Sequence↗
PubMed1996

[Incidentally discovered masses: diagnostic and therapeutic features].

The term "incidentaloma", which was first used to indicate a mass discovered by chance at an adrenal level, is currently used to indicate any lesion identified accidentally, namely in the absence of specific symptomatology, during echographic or tomographic examination. The authors report their experience of just over one year and, through a review of the literature, draw attention to the fact that these incidentalomas raise unresolved problems both from a diagnostic and therapeutic point of view. They hope that routine abdominal echography will be extended at least to a selected hospital population given that these lesions, diagnosed by chance, may be malignant or even if benign may have a potential evolution. Obviously surgery in these cases would lead to a marked prognostic improvement.

Abdominal Neoplasms↗
PubMed1994

Study on the thermal stability of alpha-amylase modified by maleic anhydride copolymer.

The thermal inactivation of mesophilic Bacillus subtilis alpha-amylase modified by maleic anhydride/vinyl acetate copolymer has been studied at different polymer/enzyme ratios in the pH range of relevance to enzymatic catalysis. Enzymatic activity measurements combined with circular dichroism measurements were used to determine the enzyme thermostability. The apparent first-order rate constants and activation energies of thermo-inactivation affected by addition of Ca2+ ions as well as by modification have been calculated. The modified alpha-amylase exhibited sufficiently high catalytic activity with enhanced resistance to the thermal unfolding process.

Bacillus subtilis↗
PubMed1993

[The rational use of drains in surgery].

The authors report their clinical experience in 100 cases in which various kinds of drainage were used. They outline the best present techniques, when it is wished to apply this free drainage in the abdominal cavity, at the end of the operation.

Adult↗
PubMed1993

Prosomatostatin processing in Neuro2A cells. Role of beta-turn structure in the vicinity of the Arg-Lys cleavage site.

Proline residues located near the processing sites of human prosomatostatin were previously shown to be important for cleavage of the precursor into somatostatin 28 and somatostatin 14 [Gomez, S., Boileau, G., Zollinger, L., Nault, C., Rholam, M. & Cohen, P. (1989) EMBO J. 8, 2911-2916]. In this study, site-directed and regional mutagenesis of the human prosomatostatin cDNA coupled with analysis by circular-dichroism and Fourier-transform-infrared spectroscopies of the native and mutated peptide sequences were used to elucidate the role of proline in proteolytic processing. Glycine was substituted for proline a position -5 and the beta-turn-promoting sequence Pro-Arg-Glu-Arg, located near the somatostatin-14 cleavage site and predicted to form a beta-turn structure, was replaced by Ser-Ser-Asn-Arg or Tyr-Lys-Gly-Arg, which have been shown by X-ray diffraction to form beta turns in other proteins. Analysis of the prosomatostatin-derived peptides produced by expression of the mutated cDNA species in Neuro2A cells indicated that while Pro-5-->Ala abolished cleavage at the dibasic site, the formation of mutants [Gly-5] prosomatostatin, [Ser-5, Ser-4, Arg-3] prosomatostatin and [Tyr-5, Lys-4, Gly-3] prosomatostatin did not affect cleavage at the dibasic site but produced modifications in both the relative proportions of the generated hormones and in precursor processing efficiency. Moreover, spectroscopical analysis showed that whereas these substitutions did not modify the presence of a beta turn structure in the corresponding peptide sequences, replacement of Pro-5-->Ala resulted in a dramatic increase in alpha-helix accompanied by the significant decrease of other structures including beta turn. The data support the hypothesis that the proline residue near the processing site for somatostatin-14 production is an important structural feature for conferring on the cleavage domain the adequate conformation for accessibility to processing enzymes and permitting production of equivalent amounts of both hormones.

Amino Acid Sequence↗
PubMed1992

Evidence for the presence of a secondary structure at the dibasic processing site of prohormone: the pro-ocytocin model.

Bioactivation of pro-proteins by limited proteolysis is a general mechanism in the biosynthesis of hormones, receptors and viral protein precursors. This proceeds by cleavage of peptide bonds at the level of single or pairs of basic residues in the proforms. Examination of a number of cleavage loci in various precursors failed to reveal any consensus primary sequence around the dibasic cleavage sites. Thus it has been proposed, on the basis of secondary structure predictions [Rholam, M., Nicolas, P. and Cohen, P. (1986) FEBS Lett., 207, 1-6], that those basic residues which operate as signal loci for the proteolytic enzyme machinery are situated in, or next to, privileged precursor regions most often constituted by flexible and exposed motifs, e.g. beta-turns and/or loops. Peptides reproducing the N-terminal processing domain of the hormone precursor, pro-ocytocin-neurophysin, were examined by a combination of spectroscopical techniques including circular dichroism, infrared Fourier transform and one- and two-dimensional proton NMR. The results indicate that: (i) the region situated on the N terminus of the Lys-Arg doublet is organized as a beta-turn in solution; (ii) the sequential organization of the residues participating in the beta-turn determines the privileged relative orientation of the basic amino acid side chains and the subtype of turn; (iii) the peptide segment situated on the C-terminal side of the dibasic, corresponding to the N-terminal octapeptide of neurophysin, is organized as an alpha-helix.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Immunogenicity of tetravalent rhesus rotavirus vaccine administered with buffer and oral polio vaccine.

Between January and November 1989, we studied 174 infants aged 6 to 16 weeks in a randomized clinical trial to (1) determine the immunogenicity of a single dose of tetravalent rhesus rotavirus vaccine (RRV-TV) when administered with three different buffer regimens: no antacid buffer and small-volume (2.5-mL) and large-volume (30-mL) antacid buffer; and (2) examine the potential interference of RRV-TV on the immune response to oral polio vaccine. Immunogenicity of RRV-TV, measured as a fourfold rise in antibody titers to rotavirus, was similar in the groups receiving small- and large-dose buffer (45% and 49%, respectively) and significantly less in the group that received RRV-TV alone (23%). Administration of RRV-TV with oral polio vaccine did not significantly interfere with the neutralization response of oral polio vaccine poliovirus serotypes 1, 2, or 3, and overall, 29%, 87%, and 24% of the infants had a fourfold rise in titer to each serotype, respectively.

Antibodies, Viral↗
PubMed1990

[Double hydatid cyst of the liver, one of them with a fistula and causing stenosis of the pyloric canal associated with calculous cholecystitis].

A case of double hydatid cyst of the liver (one fistulised into the pyloric canal where it had caused stenosis) and its association with calculous cholecystitis is reported. The therapy chosen to treat this rare phenomenon had a very satisfactory outcome in view of the complexity of the case given the need to perform several operations in contemporary (enucleation of the cyst, gastric resection and cholecystectomy) and the age of the patient.

Aged↗
PubMed1990

[Diverticulitis of the right colon. Description of our experience].

Two cases of diverticultis of the right colon are described which received surgical treatment. These lesions often simulate acute appendicitis and thus represent a intraoperative surprise Differential diagnosis using a neoblastic mass is often impossible. The paper stresses the importance of surgical treatment which in general terms is the same as the treatment of the diverticular mass of the left colon. In cases where it is difficult to decide between a phlogostic and neoblastic pathology, it is advised that a right hemicolectomy should be performed in line with criteria for oncological requirements.

Adult↗