Search PubMed⌕ Search

Biomedical subjects

G De Simone

Publications and source records attributed to G De Simone.

At least 19 recordsLinked to original sources
PubMed2006

Effects of various antireabsorptive treatments on bone mineral density in hypogonadal young women after allogeneic stem cell transplantation.

Ovarian failure after allogeneic stem cell transplant (allo-SCT) is an important risk factor for development of osteoporosis. We investigated the effects of various antiresorptive treatments in long-term surviving females with ovarian failure after allo-SCT. A total of 60 women with osteoporosis or osteopenia were divided randomly into four groups of 15 women each. Group 1 was treated with calcium and vitamin D alone, group 2 received the same treatment in combination with hormone replacement therapy (HRT), group 3 received risedronate (35 mg weekly, orally for 1 year) and group 4 zoledronic acid (3 monthly doses of 4 mg (intravenous)). All groups were similar for age, body mass index, underlying disease and time elapsed from transplant. Lumbar and femoral bone mineral density (BMD) were measured at baseline and after 12 months, together with serum osteocalcin and urinary hydroxyproline. At 12 months, a significant decrease in lumbar and femoral BMD was observed in group 1 and a milder decrease in group 2. Risedronate treatment increased significantly lumbar BMD and prevented bone loss at the femoral neck. Zoledronic acid increased significantly both lumbar and femoral BMD. In groups 3 and 4 the hydroxyproline excretion was significantly reduced, while osteocalcin mildly increased only in group 4. In conclusion, bisphosphonate administration is useful to prevent and treat bone demineralization in young adult women after allo-SCT.

Adolescent↗
PubMed2006

[Gallstone ileus: diagnosis and treatment. Case report].

The authors present a case of gallstone intermittent ileus caused by the passage of a big gallstone (about 4 cm in diameter) in the intestinal lumen, through a cholecystoduodenal fistula. They emphasize the peculiarity of the case for the characteristics of symptoms and for casual diagnostic check-up with a ultrasonography. The disease is not frequently diagnosed; today it has a safe recognition by modern imaging. The symptoms can be intermittent and, even when there are the classic signs of intestinal occlusion, the site of the occlusion is various. With a timely endoscopical or surgical approach (open or laparoscopic) it is possible to reduce mortality of patients treated in emergency.

Aged↗
PubMed2002

Modification of respiratory function parameters in patients with severe Parkinson's disease.

Respiratory dysfunction remains one of the most common causes of death in patients with complicated Parkinson's disease (PD). The aim of this study was to investigate pulmonary function in fluctuating PD patients during "on" and "off" states of the disease. We studied 12 fluctuating, non-smoking PD patients (H&Y stages 3-5) without a history of lung or cardiovascular disease; all patients underwent Hoehn and Yahr scale (H&Y) and Unified Parkinson Disease Rating Scale (UPDRS items 18-31) to evaluate extrapyramidal impairment, as well as pulmonary function tests (PFT) and arterial blood gas analyses to assess respiratory function. All evaluations were performed during a stable on state of disease and in an off state produced by 12 hours of therapy withdrawal. A restrictive pattern of flow-volume loop was observed both in on and off states of disease. In the off state, we found a significant worsening in both FEV1 and FVC; the FEV1/FVC ratio was unmodified. These results suggest a restrictive pattern of flow-volume loop in these patients.

Aged↗
PubMed2002

Efficacy of very low dose perindopril 2 mg/indapamide 0.625 mg combination on left ventricular hypertrophy in hypertensive patients: the P.I.C.X.E.L. study rationale and design.

The PICXEL study is designed to evaluate the effects of long-term administration of very low-dose combination perindopril 2 mg/indapamide 0.625 mg (Per/Ind) vs enalapril in reducing left ventricular hypertrophy (LVH) in hypertensive patients. This multicentre, controlled, randomised, double-blind, parallel group study is carried-out to assess the variation of left ventricular mass index (LVMI) after treatment, using a centralised control of M-mode echocardiography determinations, and a dedicated software for semi-automatic measurement. Following a 4-week placebo run-in period, hypertensive outpatients aged >/=18 years, with LVH (LVMI >120 and 100 g/m(2) for men and women, respectively), are randomised to receive once daily, over 52 weeks, either Per/Ind or enalapril. According to blood pressure levels, the dose may be adjusted. In addition to clinical examinations, ECG, blood pressure, heart rate and laboratory assessments echocardiographic determinations are performed for selection, at baseline, after 24 weeks and at the end of the study. The main outcome criteria is the change from baseline in LVMI which is considered the primary efficacy criterion; changes in blood pressure and echo-Doppler parameters constitute secondary criteria. Two-sided Student's t-test for independent samples will be used to differentiate the effects of the treatment between groups with alpha = 5%, and the inter-group difference of LVMI variation will be analysed with a power of 90%. A sample size of 500 patients is required making it necessary to randomise at least 550 patients, based on a 10% proportion of potentially non-assessable patients. The results of this study, obtained after applying strict methodological procedures and requirements, are expected to provide valuable and reliable information on the effects of long-term administration of Per/Ind on LVH, and on its potential superiority over enalapril.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

The crystal structure of a hyper-thermophilic carboxylesterase from the archaeon Archaeoglobus fulgidus.

The crystal structure of AFEST, a novel hyper-thermophilic carboxylesterase from the archaeon Archaeoglobus fulgidus, complexed with a sulphonyl derivative, has been determined and refined to 2.2 A resolution. This enzyme, which has recently been classified as a member of the hormone- sensitive-lipase (H) group of the esterase/lipase superfamily, presents a canonical alpha/beta hydrolase core, shielded on the C-terminal side by a cap region composed of five alpha-helices. It contains the catalytic triad Ser160, His285 and Asp255, whereby the nucleophile is covalently modified and the oxyanion hole formed by Gly88, Gly89 and Ala161. A structural comparison of AFEST with its mesophilic and thermophilic homologues, Brefeldin A esterase from Bacillus subtilis (BFAE) and EST2 from Alicyclobacillus acidocaldarius, reveals an increase in the number of intramolecular ion pairs and secondary structure content, as well as a significant reduction in loop extensions and ratio of hydrophobic to charged surface area. The variety of structural differences suggests possible strategies for thermostabilization of lipases and esterases with potential industrial applications.

Amino Acid Sequence↗
PubMed2000

A snapshot of a transition state analogue of a novel thermophilic esterase belonging to the subfamily of mammalian hormone-sensitive lipase.

EST2 is a novel thermophilic carboxylesterase, isolated and cloned from Alicyclobacillus (formerly Bacillus) acidocaldarius, which optimally hydrolyses esters with acyl chain lengths of six to eight carbon atoms at 70 degrees C. On the basis of the amino acid sequence homology, it has been classified as a member of the mammalian hormone-sensitive lipase (HSL) subfamily. The crystal structure of EST2, complexed with a sulphonyl derivative, has been determined at 2.6 A resolution by a multiple wavelength anomalous diffraction experiment on a seleno-methionine derivative. EST2 presents a canonical alpha/beta hydrolase core, shielded at the C-terminal side by a cap region built up of five helices. It contains the lipase-like catalytic triad, Ser155, His282 and Asp252, whereby the nucleophile is covalently modified. This allows an unambiguous view of the putative active site of EST2, detecting the oxyanion hole, in whose formation the amino acid sequence motif His81-Gly82-Gly83-Gly84 is involved, and the hydrophobic binding pocket for the acyl chain. The structural model here reported provides the first example of a transition state analogue of an esterase/lipase belonging to the HSL group, thus affording useful information for the design of medical inhibitors. Moreover, as the first X-ray structure of a thermophilic carboxylesterase, the comparison with its mesophilic homologue, the Brefeldin A esterase (BFAE) from Bacillus subtilis, allows the identification of putative determinants of thermal stability.

Amino Acid Sequence↗
PubMed2000

The crystal structure of Afc-containing peptides.

A systematic structural analysis of Afc (9-amino-fluorene-9-carboxylic acid) containing peptides is here reported. The crystal structures of four fully protected tripeptides containing the Afc residue in position 2: Z-X(1)-Afc(2)-Y(3)-OMe (peptide a: X = Y = Gly; peptide b: X = Aib, C(alpha, alpha)-dimethylglycine, Y = Gly; peptide c: X = Gly, Y = Aib; peptide d: X = Y = Aib) have been solved by x-ray crystallography. All the results suggest that the Afc residue has a high propensity to assume an extended conformation. In fact, the Afc residue adopts an extended conformation in three peptides examined in this paper (peptides a-c). In contrast, Afc was found in a folded conformation, in the 3(10)-helical region, only in the peptide d, in which it is both preceded and followed by the strong helix promoting Aib.

Amino Acids↗
PubMed2000

Conformational behavior of C alpha,alpha-diphenyl glycine: extended conformation in tripeptides containing consecutive D phi G residues.

Recent studies on the conformational preferences of the Dphig (C(alpha,alpha)-diphenylglycine) residue showed that this C(alpha,alpha)-disubstituted glycine has a structural versatility. In fact, depending on the nature of the following or preceding residue, Dphig can assume either folded or extended conformations. We have carried out the analysis of the conformational preferences of the Dphig residue in tripeptides containing consecutive Dphig residues. The crystal structures of Z-Dphig-Dphig -Dphig-OMe (a; Z = benzyloxycarbonyl; OMe = methyl ester), Z-Aib-Dphig-Dphig-OMe (b; Aib = alpha-aminoisobutyric acid), and Z-Ac(3)c-Dphig-Dphig-OMe (c; Ac(3)c = alpha-amino-cyclopropan carboxylic acid), are here reported. The Dphig residues adopt the fully extended conformation in the three tripeptides examined. Together with our previous findings on Dphig containing peptides, the structures of the peptides here examined, indicate that the presence of adjacent Dphig residue in the sequence further stabilizes the extended conformation.

Crystallography, X-Ray↗
PubMed2000

The crystal structure of a Dcp-containing peptide.

We have investigated the conformational preferences of a newly synthesized C(alpha,alpha) symmetrically disubstituted glycine, namely alpha,alpha-dicyclopropylglycine (Dcp). We report here the crystal structure of a fully protected dipeptide containing Dcp, namely Z-Dcp(1)-Dcp(2)-OCH(3). Both Dcp residues are in a folded conformation. The overall peptide structural organization corresponds to an alpha-pleated sheet conformation, similar to that observed in linear peptides made up of alternating D- and L-residues and in Z-Aib-Aib-OCH(3) (Aib: alpha,alpha-dimethylglycine). These preliminary data suggest that the Dcp could represent an alternative as molecular tool to stabilize folded conformations.

Crystallography, X-Ray↗
PubMed2000

Comparative efficacy study of atorvastatin vs simvastatin, pravastatin, lovastatin and placebo in type 2 diabetic patients with hypercholesterolaemia.

Although there is little information from primary or secondary prevention trials on cholesterol-lowering medication in diabetic patients, the reduction of elevated cholesterol is widely recommended for this group. The American Diabetes Association (ADA) recommends drug therapy in diabetic patients if low density lipoprotein (LDL)-cholesterol remains at > 130 mg/dl, or > 100 mg/dl in patients with macroangiopathy, after dietary intervention. When cholesterollowering medication is indicated, the choice of the drug must take into account the other lipid abnormalities that are often present and the need to maintain optimal glycaemic control. In the present study we compared the efficacy and safety of the novel HMG-CoA reductase inhibitor atorvastatin at the dose of 10 mg/day with simvastatin , lovastatin and pravastatin at doses of 10, 20 and 20 mg/day, respectively, and placebo, in type 2 diabetic patients with moderate elevation of LDL-cholesterol with or without elevation of triglycerides. All the quoted agents are enzyme inhibitors effective in lowering LDL-cholesterol in humans. The efficacy endpoints were the mean per cent changes in plasma LDL-cholesterol (primary), total cholesterol, triglycerides, and high-density lipoprotein (HDL)-cholesterol concentrations from baseline to the end of treatment (24 weeks). Atorvastatin at a dose of 10 mg/day produced: (1) a significant reduction in LDL-cholesterol (-37%) in comparison with equivalent doses of simvastatin (-26%), pravastatin (-23%), lovastatin (-21%), and placebo (-1%); (2) HDL-cholesterol increases (7.4%) comparable to or greater than those obtained with simvastatin (7.1%), pravastatin (3.2%), lovastatin (7.21%), and placebo (-0.5%); (3) a significantly greater reduction in total cholesterol (- 29%) than that obtained with simvastatin (-21%), pravastain (-16%), lovastatin (-18%), and placebo (1%); and (4) a significantly greater reduction in triglycerides than that obtained with all the other drugs and placebo. In all treatment groups no significant variation in fibrinogen concentration was observed. All reductase inhibitors studied had similar levels of tolerance. There were no incidents of persistent elevations of serum aminotransferases or myositis.

Aged↗
PubMed2000

[Myocardial metabolism of calcium in heart failure: from physiology to new therapeutic perspectives].

Development of heart failure is associated with an impairment of intracellular calcium handling. The precise mechanisms involved are still obscure. When membrane depolarization occurs, a small amount of extracellular calcium enters the intracellular milieu through the L-type channels. Such "trigger" calcium acts on specific receptors of the sarcoplasmic reticulum, that, in turn, according to the so-called calcium entry-calcium release mechanism, allows the release of a larger amount of calcium from the sarcoplasmic reticulum. Removal of calcium from the cytosol is the key event of the diastolic phase. Calcium removal from cytosol occurs through specific membrane pumps. Recent therapeutic approaches involving gene targeting of calcium pumps have yielded promising results. Specifically, increased levels of SERCA 2 in the myocardium have shown to enhance cardiac contractility under normal circumstances and in experimental heart failure. Future research is needed to confirm these findings in human heart failure.

Calcium↗
PubMed1999

Probing the reactivity of nucleophile residues in human 2,3-diphosphoglycerate/deoxy-hemoglobin complex by aspecific chemical modifications.

The use of aspecific methylation reaction in combination with MS procedures has been employed for the characterization of the nucleophilic residues present on the molecular surface of the human 2,3-diphosphoglycerate/deoxy-hemoglobin complex. In particular, direct molecular weight determinations by ESMS allowed to control the reaction conditions, limiting the number of methyl groups introduced in the modified globin chains. A combined LCESMS-Edman degradation approach for the analysis of the tryptic peptide mixtures yielded to the exact identification of methylation sites together with the quantitative estimation of their degree of modification. The reactivities observed were directly correlated with the pKa and the relative surface accessibility of the nucleophilic residues, calculated from the X-ray crystallographic structure of the protein. The results here described indicate that this methodology can be efficiently used in aspecific modification experiments directed to the molecular characterization of the surface topology in proteins and protein complexes.

2,3-Diphosphoglycerate↗
PubMed1999

From natural to synthetic multisite thrombin inhibitors.

A large number of potent and selective therapeutic agents, useful for the treatment of several diseases, have been isolated from natural sources. For example, the most active thrombin inhibitors are those secreted by the salivary glands of leeches. One peculiar feature of these agents is the lack of any significant inhibitory cross-reaction with other serine proteinases. Hence, the knowledge of the exact mechanism of action of these molecules provides the basis for the development of new and efficient synthetic drugs. For this reason, many studies have been undertaken on the structure-activity relationships of natural thrombin inhibitors, and a large amount of detailed information has been obtained by the crystal structures of these inhibitors when complexed with thrombin. In this paper, we review natural and synthetic multisite thrombin inhibitors, whose structural aspects have been determined in detail. We also report here the approach used by us to develop a new class of synthetic, multisite directed thrombin inhibitors, named hirunorms, designed to mimic the distinctive binding mode of hirudin.

Amino Acid Sequence↗
PubMed1999

Crystallization and preliminary X-ray diffraction studies of the carboxylesterase EST2 from Alicyclobacillus acidocaldarius.

EST2, a thermophilic carboxylesterase from Alicyclobacillus acidocaldarius, belonging to the HSL group of the esterase/lipase superfamily, has been crystallized for the first time. Ammonium sulfate was used as a precipitant and the crystallization proceeded at pH 7.8. The crystals belong to space group P41212 or its enantiomorph P43212, with unit-cell parameters a = b = 78.8, c = 106. 4 A. A complete data set has been collected at the synchrotron source Elettra in Trieste to 2.4 A resolution, using a single frozen crystal.

Bacillaceae↗
PubMed1999

The crystal structure of alpha-thrombin-hirunorm IV complex reveals a novel specificity site recognition mode.

The X-ray crystal structure of the human alpha-thrombin-hirunorm IV complex has been determined at 2.5 A resolution, and refined to an R-factor of 0.173. The structure reveals an inhibitor binding mode distinctive of a true hirudin mimetic, which justifies the high inhibitory potency and the selectivity of hirunorm IV. This novel inhibitor, composed of 26 amino acids, interacts through the N-terminal end with the alpha-thrombin active site in a nonsubstrate mode, and binds specifically to the fibrinogen recognition exosite through the C-terminal end. The backbone of the N-terminal tripeptide Chg1"-Arg2"-2Na13" (Chg, cyclohexyl-glycine; 2Na1, beta-(2-naphthyl)-alanine) forms a parallel beta-strand to the thrombin main-chain segment Ser214-Gly216. The Chg1" side chain occupies the S2 site, Arg2" penetrates into the S1 specificity site, while the 2Na13" side chain occupies the aryl binding site. The Arg2" side chain enters the S1 specificity pocket from a position quite apart from the canonical P1 site. This notwithstanding, the Arg2" side chain establishes the typical ion pair with the carboxylate group of Asp189.

Amino Acid Sequence↗
PubMed1998

Hirunorms are true hirudin mimetics. The crystal structure of human alpha-thrombin-hirunorm V complex.

A novel class of synthetic, multisite-directed thrombin inhibitors, known as hirunorms, has been described recently. These compounds were designed to mimic the binding mode of hirudin, and they have been proven to be very strong and selective thrombin inhibitors. Here we report the crystal structure of the complex formed by human alpha-thrombin and hirunorm V, a 26-residue polypeptide containing non-natural amino acids, determined at 2.1 A resolution and refined to an R-factor of 0.176. The structure reveals that the inhibitor binding mode is distinctive of a true hirudin mimetic, and it highlights the molecular basis of the high inhibitory potency (Ki is in the picomolar range) and the strong selectivity of hirunorm V. Hirunorm V interacts through the N-terminal tetrapeptide with the thrombin active site in a nonsubstrate mode; at the same time, this inhibitor specifically binds through the C-terminal segment to the fibrinogen recognition exosite. The backbone of the N-terminal tetrapeptide Chg1"-Val2"-2-Nal3"-Thr4" (Chg, cyclohexyl-glycine; 2-Nal, beta-(2-naphthyl)-alanine) forms a short beta-strand parallel to thrombin main-chain residues Ser214-Gly219. The Chg1" side chain fills the S2 subsite, Val2" is located at the entrance of S1, whereas 2-Nal3" side chain occupies the aryl-binding site. Such backbone orientation is very close to that observed for the N-terminal residues of hirudin, and it is similar to that of the synthetic retro-binding peptide BMS-183507, but it is opposite to the proposed binding mode of fibrinogen and of small synthetic substrates. Hirunorm V C-terminal segment binds to the fibrinogen recognition exosite, similarly to what observed for hirudin C-termninal tail and related compounds. The linker polypeptide segment connecting hirunorm V N-and C-terminal regions is not observable in the electron density maps. The crystallographic analysis proves the correctness of the design and it provides a compelling proof on the interaction mechanism for this novel class of high potency multisite-directed synthetic thrombin inhibitors.

Antithrombins↗
PubMed1997

Pitfalls in echocardiographic-based repair of aortic coarctation.

The knowledge of echocardiographic pitfalls, which may impair the correct indication for surgery of aortic coarctation, is of great importance to pediatric cardiologists. We believe that only the suspicion of coronary artery anomalies is a clear indication to perform a cardiac catherization.

Adolescent↗