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Biomedical subjects

F Franceschi

Publications and source records attributed to F Franceschi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Ribosomal crystallography: from poorly diffracting microcrystals to high-resolution structures.

The cellular organelles translating the genetic code into proteins, the ribosomes, are large, asymmetric, flexible, and unstable ribonucleoprotein assemblies, hence they are difficult to crystallize. Despite two decades of intensive effort and thorough searches for suitable sources, so far only three crystal types have yielded high-resolution structures: two large subunits (from an archaean and from a mesophilic eubacterium) and one thermophilic small subunit. These structures have added to our understanding of decoding, have revealed dynamic aspects of the biosynthetic process, and have indicated the strategies adopted by ribosomes for interacting between themselves as well as with inhibitors, factors and substrates.

Archaea↗
PubMed2001

Comparison of morphine and ropivacaine following knee arthroscopy.

PURPOSE: The purpose of this study was to compare the effectiveness of ropivacaine, a new local amidic anesthetic, compared with morphine as an intra-articular drug in controlling pain in patients after arthroscopic knee surgery. TYPE OF STUDY: Randomized trial. METHODS: We enrolled 90 patients scheduled to undergo elective knee arthroscopy. Patients were homogenous regarding demographic data and ASA physical status. Procedures included were diagnostic arthroscopies, lateral and medial meniscectomies, meniscal repair, and removal of loose bodies. All cases were treated by the same surgeon, under general anesthesia, using the same procedure. Patients were randomly divided into 3 groups. The first group received ropivacaine 75 mg in 20 mL of saline solution, the second group received 2 mg morphine in 20 mL of saline solution, and the third group received 20 mL of saline solution. No other oral or injectable analgesic administration was allowed. A blind observer assessed the patients' postoperative pain using a 10-cm visual analogue scale (VAS), ranging from no pain (0) to unbearable pain (10). Scores were taken at 0, 1, 4, 6, 12, and 24 hours after drug injection. VAS scores were analyzed using analysis of variance; significance was set at P <.005. RESULTS: None of the patients treated with ropivacaine or morphine needed administration of any other oral or injectable analgesic. No adverse reaction was noted in ropivacaine group. VAS score analysis in the first 4 postoperative hours showed greater effectiveness for ropivacaine versus morphine or placebo with highly significant results (P <.001). In the first 24 postoperative hours, the ropivacaine group versus the morphine group showed no significant differences (P =.207). CONCLUSIONS: Although its cost is very high compared with morphine, ropivacaine is a safe, site-specific, and long lasting anesthetic drug with an earlier onset than morphine and almost the same duration, covering the whole postoperative period (24 hours).

Adult↗
PubMed2001

Prevalence of and risk factors for Helicobacter pylori infection among healthcare workers at a teaching hospital in Rome: the Catholic University Epidemiological Study.

OBJECTIVES: To evaluate the prevalence of and the risk factors for Helicobacter pylori in a population of medical and non-medical workers at a teaching hospital in Rome, Italy. DESIGN: A cross-sectional study. METHODS: From January to October 1998, 655 subjects (65% of the total population) underwent a 13C-urea breath test to assess H. pylori infection. Subjects completed a questionnaire concerning sociodemographic characteristics, work departments and history of some gastrointestinal symptoms. Differences in means and proportions were evaluated and independent predictors of H. pylori infection status were assessed by multiple logistic regression analysis. RESULTS: Forty percent of the subjects were found to be H. pylori infected. The mean age of positive subjects was significantly higher than that of negative ones (38 +/- 14 versus 34 +/- 12 years; P < 0.01). No significant difference was found between males and females concerning the infection status (40.2% males versus 39.9% females). Lower years of father's education [odds ratio (OR), 3.1; 95% confidence interval (CI), 1.9-5.1] and age older than 35 years (OR, 2.0; 95% CI, 1.3-3.1) were the only independent predictors of the likelihood of H. pylori positivity. Prevalence of gastrointestinal symptoms was similar in infected and uninfected subjects. Physicians were significantly less infected than nurses and auxiliary personnel (26% versus 47% versus 55%, respectively); however, a loss of association was observed after adjustment by multiple logistic regression (OR, 1.8; 95% CI, 0.9-3.7). In all groups, some specific departments appear to be associated with a higher infection status. CONCLUSIONS: Among healthcare workers, H. pylori infection was associated with specific sociodemographic characteristics, such as age and level of father's education. The prevalence of H. pylori infection was not associated with different professional categories. However, some specific departments seem to increase infection risk.

Adult↗
PubMed2001

Helicobacter pylori infection affects eosinophilic cationic protein in the gastric juice of patients with idiopathic chronic urticaria.

BACKGROUND: Helicobacter pylori, the main cause of gastritis and peptic ulcer, has been associated with idiopathic chronic urticaria (ICU), an immunological skin disorder of unknown origin. Eosinophilic cationic protein (ECP) is a cytotoxic molecule secreted by the activated eosinophils involved in the pathogenesis of ICU. We assessed serum/gastric juice ECP levels and gastric mucosal eosinophil infiltration in ICU patients infected or not with H. pylori and evaluated the modification after bacterium eradication. METHODS: 33 patients with ICU and 25 dyspeptic controls underwent upper gastrointestinal endoscopy for histological evaluation and assessment of H. pylori infection. One-week triple therapy was given to H. pylori-positive patients. Serum and gastric juice ECP levels, eosinophil infiltration from gastric mucosal sections and urticaria symptoms were evaluated in all patients at enrollment and 8 weeks after eradication. RESULTS: 19 of 33 (57%) ICU patients and 16 of 25 (64%) controls were found to be infected with H. pylori. Serum ECP was significantly higher in ICU patients compared to controls, regardless of infectious status. Gastric juice ECP and gastric eosinophil infiltration were significantly higher in infected ICU patients when compared both to uninfected ICU patients and controls. H. pylori eradication determined a significant decrease in gastric juice ECP and gastric eosinophil infiltration only in ICU patients. Moreover, a total or partial remission of urticaria symptoms was observed only in ICU patients in whom the bacterium was eradicated. CONCLUSIONS: Although H. pylori infection affects gastric juice ECP and eosinophil infiltration of ICU patients, the role of the bacterium in the pathogenesis of this skin disorder still remains uncertain.

Adult↗
PubMed2000

Structure of functionally activated small ribosomal subunit at 3.3 angstroms resolution.

The small ribosomal subunit performs the decoding of genetic information during translation. The structure of that from Thermus thermophilus shows that the decoding center, which positions mRNA and three tRNAs, is constructed entirely of RNA. The entrance to the mRNA channel will encircle the message when a latch-like contact closes and contributes to processivity and fidelity. Extended RNA helical elements that run longitudinally through the body transmit structural changes, correlating events at the particle's far end with the cycle of mRNA translocation at the decoding region. 96% of the nucleotides were traced and the main fold of all proteins was determined. The latter are either peripheral or appear to serve as linkers. Some may assist the directionality of translocation.

Base Pairing↗
PubMed2000

Adduct formation between alkali metal ions and divalent metal salicylaldimine complexes having methoxy substituents. A structural investigation.

Sodium, potassium, and cesium salts (iodides, nitrates, acetates, and tetraphenylborates) form 1/1, 1/2 and 2/3 adducts with MLn [M = Co, Ni, Cu, and Zn; n = 1-4; H2L1 = N,N'-(3-methoxysalicyliden)ethane-1,2-diamine; H2L2, H2L3, and H2L4 are the -propane-1,2-diamine, -o-phenylenediamine, and -propane-1,3-diamine analogues of H2L1). Metal salicyladimine, alkali metal, and anion all exert influence on stoichiometry and reactivity. Sodium ions tend to reside within the planes of the salicylaldimine oxygens, as in Na(NO3)(MeOH).NiL4 (1), Na(NO3)(MeOH).CuL1 (2; both with unusual seven-coordinated sodium), and Na.(NiL4)2I.EtOH.H2O (3; with dodecahedral sodium coordination geometry). Potassium and cesium tend to locate between salicylaldimine ligands as in KI.NiL4 (4) and [Cs(NO3).NiL4]3.MeOH (5; structures with infinite sandwich assemblies), CsI.(NiL2)2.H2O (6), CsI3.(NiL4)2 (7; simple sandwich structures), and [K(MeCN)]2.(NiL4)3 (8; a triple-decker sandwich structure). Crystal data for 1 are the following: triclinic, P1, a = 7.3554(6) A, b = 11.2778(10) A, c = 13.562(2) A, alpha = 96.364(10) degrees, beta = 101.924(9) degrees, gamma = 96.809(10) degrees, Z = 2. For 2, triclinic, P1, a = 7.2247(7) A, b = 11.0427(6) A, c = 13.5610(12) A, alpha = 94.804(5) degrees, beta = 98.669(7) degrees, gamma = 99.26(6) Z = 2. For 3, orthorhombic, Pbca, a = 14.4648(19) A, b = 20.968(3) A, c = 28.404(3) A, Z = 8. For 4, triclinic, P1, a = 12.4904(17) A, b = 13.9363(13) A, c = 14.1060(12) A, alpha = 61.033(7) degrees, beta = 89.567(9) degrees, gamma = 71.579(10) degrees, Z = 2. For 5, monoclinic. P2(1)/n, a = 12.5910(2) A, b = 23.4880(2) A, c = 22.6660(2) A, beta = 99.3500(1) degree, Z = 4. For 6, orthorhombic, Pbca, a = 15.752(3) A, b = 23.276(8) A, c = 25.206(6) A, Z = 8. For 7, triclinic, P1, a = 9.6809(11) A, b = 10.0015(13) A, c = 11.2686(13) A, alpha = 101.03 degrees, beta = 90.97 degrees, gamma = 100.55 degrees, Z = 2. For 8, monoclinic, C2/c, a = 29.573(5) A, b = 18.047(3) A, c = 23.184(3) A, beta = 122.860(10) degrees, Z = 8.

Journal Article↗
PubMed2000

Association between Helicobacter pylori cytotoxic type I CagA-positive strains and migraine with aura.

Recent studies have suggested an association between Helicobacter pylori infection and migraine. However, various strains of the bacterium are present, some endowed with greater pathogenicity. In particular, H. pylori type I CagA-positive strains induce a higher release of proinflammatory substances by the gastric mucosa that could trigger systemic vasospasms. The aim of the present study was to assess the prevalence of H. pylori CagA-positive strains in subjects with migraine. One hundred and seventy-five patients affected by migraine (49 with aura, 126 without aura) were consecutively enrolled and matched for sex, age, social background and geographical origin with 152 controls. Helicobacter pylori infection was assessed through 13C-urea breath test. Specific serological IgG against CagA were detected through ELISA. The prevalence of H. pylori infection was similar in migraine patients and in controls (40% vs. 39%, respectively). Among migraine patients, prevalence of infection was not related to presence or absence of aura (45% vs. 37%, respectively). However, among infected subjects, a significantly higher prevalence of CagA-positive strains was observed in patients affected by migraine with aura when compared with those affected by migraine without aura (41% vs. 19%, P < 0.01) and with controls (41% vs. 17%, P < 0.01). CagA-positive H. pylori strains were found to be strongly associated with migraine with aura. A higher inflammatory response of the gastric mucosa to more virulent strains could release substances that may act as triggers of vasospasm in peculiar cerebral arterial districts, probably implicated in the 'aura' phenomenon.

Adult↗
PubMed2000

Genetic and biochemical manipulations of the small ribosomal subunit from Thermus thermophilus HB8.

Crystals of the small ribosomal subunit from Thermus thermophilus diffract to 3A and exhibit reasonable isomorphism and moderate resistance to irradiation. A 5A MIR map of this particle shows a similar shape to the part assigned to this particle within the cryo-EM reconstructions of the whole ribosome and contains regions interpretable either as RNA chains or as protein motifs. To assist phasing at higher resolution we introduced recombinant methods aimed at extensive selenation for MAD phasing. We are focusing on several ribosomal proteins that can be quantitatively detached by chemical means. These proteins can be modified and subsequently reconstituted into depleted ribosomal cores. They also can be used for binding heavy atoms, by incorporating chemically reactive binding sites, such as -SH groups, into them. In parallel we are co-crystallizing the ribosomal particles with tailor made ligands, such as antibiotics or cDNA to which heavy-atoms have been attached or diffuse the latter compounds into already formed crystals.

Bacterial Proteins↗
PubMed2000

Targeting exposed RNA regions in crystals of the small ribosomal subunits at medium resolution.

Within the framework of ribosomal crystallography, the small subunits are being analyzed, using crystals diffracting to 3 A resolution. The medium resolution electron density map of this subunit, obtained by multiple isomorphous replacement, show recognizable morphologies, strikingly similar to the functional active conformer of the small ribosomal subunit. It contains elongated dense features, traceable as RNA chains as well as globular regions into which the structures determined for isolated ribosomal proteins, or other known structural motifs were fitted. To facilitate unbiased map interpretation, metal clusters are being covalently attached either to the surface of the subunits or to DNA oligomers complementary to exposed ribosomal RNA. Two surface cysteines and the 3' end of the 16S ribosomal RNA have been localized. Targeting several additional RNA regions shed light on their relative exposure and confirmed previous studies concerning their functional relevance.

Crystallography, X-Ray↗
PubMed1999

The small ribosomal subunit from Thermus thermophilus at 4.5 A resolution: pattern fittings and the identification of a functional site.

The electron density map of the small ribosomal subunit from Thermus thermophilus, constructed at 4.5 A resolution, shows the recognizable morphology of this particle, as well as structural features that were interpreted as ribosomal RNA and proteins. Unbiased assignments, carried out by quantitative covalent binding of heavy atom compounds at predetermined sites, led to the localization of the surface of the ribosomal protein S13 at a position compatible with previous assignments, whereas the surface of S11 was localized at a distance of about twice its diameter from the site suggested for its center by neutron scattering. Proteins S5 and S7, whose structures have been determined crystallographically, were visually placed in the map with no alterations in their conformations. Regions suitable to host the fold of protein S15 were detected in several positions, all at a significant distance from the location of this protein in the neutron scattering map. Targeting the 16S RNA region, where mRNA docks to allow the formation of the initiation complex by a mercurated mRNA analog, led to the characterization of its vicinity.

Base Sequence↗
PubMed1999

Hera from Thermus thermophilus: the first thermostable DEAD-box helicase with an RNase P protein motif.

DEAD-box proteins have been implicated in a wide array of cellular processes ranging from initiation of protein synthesis and ribosome biogenesis to mRNA splicing. Here, we report the isolation, biochemical characterization and crystallization of the first thermophilic DEAD box protein, Hera (heat-resistant RNA-dependent ATPase) from Thermus thermophilus HB8. The molecular mass of the deduced Hera protein sequence (510 amino acid residues) is 55.95 kDa. Hera possesses all of the conserved motifs found among the, DEAD-box RNA helicases. In addition, it also has a motif characteristic of the protein component of ribonuclease P at its C-terminal region (residues 372-386). Hera appears to be non-specific with respect to the RNA species that triggers ATPase activity. Nevertheless, at high temperature, ATPase activity is at a maximum when bacterial 16 S rRNA or 23 S rRNA are used as the substrates. Moreover, a deletion of the RNase P protein motif significantly reduces the ability of Hera to hydrolyze ATP in the presence of RNase P RNA. Hera has a specific ATPase activity of 480 units/microg and therefore, displays the highest ATPase specific activity reported for a protein of the RNA helicase family. We determined that Hera shows helix-destabilizing activity, and that the RNA-unwinding or helix-destabilizing activity of Hera is coupled to ATP hydrolysis. Since Hera is a stable thermophilic protein and we have obtained crystals of it diffracting beyond 2.6 A, the possibilities for structure determination of a full-length RNA-helicase are open.

Adenosine Triphosphatases↗
PubMed1999

Elucidating the medium-resolution structure of ribosomal particles: an interplay between electron cryo-microscopy and X-ray crystallograhy.

BACKGROUND: Ribosomes are the universal cellular organelles that accomplish the translation of the genetic code into proteins. Electron cryo-microscopy (cryo-EM) has yielded fairly detailed three-dimensional reconstructions of ribosomes. These were used to assist in the determination of higher resolution structures by X-ray crystallography. RESULTS: Molecular replacement studies using cryo-EM reconstructions provided feasible packing schemes for crystals of ribosomes and their two subunits from Thermus thermophilus, and of the large subunits from Haloarcula marismortui. For the large subunits, these studies also confirmed the major heavy-atom sites obtained by single isomorphous replacement combined with anomalous diffraction (SIRAS) and by multiple isomorphous replacement combined with anomalous diffraction (MIRAS) at approximately 10 A. Although adequate starting phases could not be obtained for the small subunits, the crystals of which diffract to 3.0 A, cryo-EM reconstructions were indispensable for analyzing their 7.2 A multiple isomorphous replacement (MIR) map. This work indicated that the conformation of the crystallized small subunits resembles that seen within the 70S ribosomes. Subsequently, crystals of particles trapped in their functionally active state were grown. CONCLUSIONS: Single-particle cryo-EM can contribute to the progress of crystallography of non-symmetrical, large and flexible macromolecular assemblies. Besides confirming heavy-atom sites, obtained from flat or overcrowded difference Patterson maps, the cryo-EM reconstructions assisted in elucidating packing arrangements. They also provided tools for the identification of the conformation within the crystals and for the estimation of the level of inherent non-isomorphism.

Crystallography, X-Ray↗
PubMed1999

Metal compounds as tools for the construction and the interpretation of medium-resolution maps of ribosomal particles.

Procedures were developed exploiting organometallic clusters and coordination compounds in combination with heavy metal salts for derivatization of ribosomal crystals. These enabled the construction of multiple isomorphous replacement (MIR) and multiple isomorphous replacement combined with anomalous scattering medium-resolution electron density maps for the ribosomal particles that yield the crystals diffracting to the highest resolution, 3 A, of the large subunit from Haloarcula marismortui and the small subunit from Thermus thermophilus. The first steps in the interpretation of the 7. 3-A MIR map of the small subunit were made with the aid of a tetrairidium cluster that was covalently attached to exposed sulfhydryls on the particle's surface prior to crystallization. The positions of these sulfhydryls were localized in difference Fourier maps that were constructed with the MIR phases.

Animals↗
PubMed1999

Body-fat distribution and responsiveness of the pituitary-adrenal axis to corticotropin-releasing-hormone stimulation in sedentary and exercising women.

Excess upper-body (android) fat is considered an health hazard. Exercise training is known to have the potential to modify body composition and to induce a preferential loss of abdominal fat. We studied and compared the composition of whole body and major body regions using dual-energy X-ray absorptiometry (DEXA) in 21 exercising (3-4 hours of intense physical activity/day) and 21 sedentary eumenorrhoic women of similar ages, body mass index (BMI), waist-to-hip ratio (WHR) and age of menarche. In a small number of women in each group (6 out of 21), the ACTH and cortisol response to CRH test and the 24-h urinary cortisol excretion was evaluated. Exercising women had 10% higher total and leg lean mass (p<0.05), and 38% lower total fat mass (p<0.01) than sedentary women. Furthermore, the proportion of android fat was 22% lower in exercising than sedentary women (p<0.01), while the proportion of lower-body (gynoid fat) was unchanged. BMI and WHR were not different between the two groups, while the android/gynoid fat ratios were 16% lower in exercising than in sedentary women (p<0.01). In the exercising women, ACTH and cortisol plasma levels, as well as the 24-h urinary cortisol excretion, were significantly (p<0.01) higher than in the sedentary women studied. In these subjects, a direct relationship between the peak delta percentage increases of ACTH and cortisol after the CRH test and the proportion of android fat was found (r=0.60, p<0.05 and r=0.69, p<0.02, respectively). These results demonstrate that in women who practise intense exercise there are significant differences in body fat distribution in comparison to sedentary women, with a marked less amount of android fat, and suggest that this difference may be related to a reduced response of the pituitary-adrenal axis to CRH.

Absorptiometry, Photon↗
PubMed1999

Autoimmune diseases and Helicobacter pylori infection.

In the last few years several studies have been performed on the association between H. pylori infection and a miscellany of extragastric disorders which also include autoimmune diseases. In particular, emerging evidence seems to give a potential role for H. pylori in ischaemic heart disease via a cross mimicry between antibodies against heat shock protein 65 which are produced in the consequence of infection, but which are also expressed in atherosclerotic lesions. In cases of healing of Sjogren syndrome and Schonlein-Henoch, purpura have also been reported. A recent study, moreover, showed that eradication of H. pylori infection may be effective in the disappearance of autoimmune thrombocytopenia. Finally, a role for H. pylori has also been postulated in other autoimmune diseases such as membranous nephropathy and some acute immune polyneuropathies. The mechanisms behind these clinical observations still remain unclear. However, if confirmed, these findings could revise the diagnostic and therapeutic approach to diseases previously considered as idiopathics.

Animals↗