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S Leoni

Publications and source records attributed to S Leoni.

At least 19 recordsLinked to original sources
PubMed2001

Evidence for the wobbling mode in nuclei.

The nucleus (163)Lu has been populated through the fusion-evaporation reaction (139)La((29)Si,5n)(163)Lu with a beam energy of 152 MeV. The electromagnetic properties of several connecting transitions between two presumably triaxial, strongly deformed (TSD) bands have been studied. Evidence is presented for the assignment of the excited TSD band as a wobbling mode built on the yrast TSD band, based on comparisons to new calculations in which an aligned particle is coupled to a strongly deformed triaxial rotor. The wobbling mode is uniquely related to triaxiality in nuclei.

Journal Article↗
PubMed2000

Ce4

The yellow-orange oxonitridosilicate oxide Ce4[Si4O4N6]O was obtained by the reaction of cerium metal with Si(NH)2 and SiO2 in a radiofrequency furnace at 1560 degrees C. The crystal structure was determined by single-crystal X-ray diffraction (a = 1033.67(6) pm, P2,3, Z = 4, R1 = 0.0412, wR2 = 0.0678) and powder neutron diffraction. In the solid there are complex cations [Ce4O]10+ that are enveloped by a hyperbolical layer structure [Si4O4N6]10-. The layer is built up by corner-sharing SiON3 tetrahedra of Q3 type. The oxygen atoms of the SiON3 tetrahedra are terminally bound to Si, while all nitrogen atoms bridge two neighboring Si centres. The crystallographic differentiation of O and N was unequivocally possible by a careful evaluation of the single-crystal X-ray diffraction data combined with lattice-energy calculations by using the MAPLE concept (Madelung part of lattice energy). Furthermore the results were confirmed by the chemical analyses. Subsequently, the determined N/O distribution and their crystallographic ordering was proved by neutron powder diffraction. In accordance with the molar ratio Si:(O,N) = 2:5 the [Si4O4N6]10- network may be classified as a layer silicate. In this specific case a hyperbolically corrugated topology of the layers is observed; this is correlated to periodic nodal surface (PNS) representatives.

Journal Article↗
PubMed2000

Hydrogen interaction with dislocations in Si

An H plasma has a remarkable effect on dislocation mobility in silicon, reducing its activation energy to 1.2 eV. Applying density functional theory to the interactions of H and H2 with the core of the 90 degrees partial dislocation in Si, we have identified a path for motion involving kink formation and migration at hydrogenated core bonds which conforms exactly to the experimentally measured activation energy.

Journal Article↗
PubMed2000

Effect of different whole body hyperthermic sessions on the heat shock response in mice liver and brain.

We examined by Western blots the effect of variations of the heating sessions, such as duration and intensity on the following aspects: 70-kDa heat shock protein (HSP70) and HSP72 induction. Protein ubiquitination PLCgamma , PKCepsilon and PKCalpha levels in murine liver and brain were also studied. Results demonstrated that maximal induction of HSP72 was obtained after heat shock at 43.5 degrees C in both organs. Preconditioning at lower temperatures (either acclimation to 39 degrees C or induction of thermotolerance to 43.5 degrees C with a single exposure to 39 degrees C) attenuated the heat shock response. Hepatic HSP72 induction was elicited only as a consequence of hyperthermia since either fasting or restraint were unable to trigger its synthesis. On the contrary, a ubiquitination decrease of a 31 kDa protein was obtained both after hyperthermia and fasting This indicates that the latter is a more generic response of hepatic cells to noxious stimuli. Analysis of the above mentioned enzymes showed that in liver of naive mice PKCalpha is barely present while PKCepsilon is quite abundant. All hyperthermic treatments caused a general decrease of the latter, except for the heat shock at 43.5 degrees C that caused an increase. PLCgamma decreased after all heating sessions. It is known that hyperthermia in the range of 41-45 degrees C induces apoptotic death in many cell types. Therefore we analyzed the presence of the typical apoptotic DNA ladder. Our data strongly suggest that both hyperthermia and restraint induce necrosis in liver while apoptosis and necrosis become evident in brain. All these effects are still present 24 h from the last heating session: This indicates that in vivo, hyperthermia produces long term modifications of the hepatic cell.

Adaptation, Physiological↗
PubMed2000

Elucidation of simple pathways for reconstructive phase transitions using periodic equi-surface (PES) descriptors. The silica phase system. I. Quartz-tridymite

A method of estimating short topological pathways for solid-solid reconstructive phase transitions is proposed. To screen the simplest pathways out of the infinite manifold in configurational space, a Fourier function approach is used, based on periodic nodal (PNS) and periodic equi-surface (PES) descriptors. The simplicity of the chosen functions representing the structures in question and the linear transition approach provide for most simple relevant transition models. Here it is shown that the tetrahedral networks of quartz and tridymite are represented topologically and transformed into each other by this approach. A trigonal network related to alpha-ThSi2 and B2O3 appears as intermediate during the transition model of the periodic functions. The transition path found in this way seems to be of exciting directness and of fundamental topological interest. The presented approach is not restricted to this specific case and is expected to be applicable to a wide variety of reconstructive phase transitions of solids.

Journal Article↗
PubMed2000

Epidermal growth factor regulates amino acid transport in chick embryo hepatocytes via protein kinase C.

System A-mediated amino acid transport, activation of different steps of signal transduction and involvement of different isoforms of protein kinase C (PKC) have been investigated in chick embryo hepatocytes after epidermal growth factor (EGF) stimulation. EGF rapidly (10 min) increased the rate of aminoisobutyric acid (AIB) uptake in chick embryo hepatocytes freshly isolated on the 19th day of embryonic life, while no change was detectable at other embryonal stages. The growth factor stimulation was abolished by PKC and tyrosine kinase inhibitors and was mimicked by 4-phorbol-12-myristate-13-acetate, dimethyl-2 (PMA). EGF treatment did not modify the phosphorylation of the isoform of phospholipase C (PLC-), and inositol trisphosphate (IP3) and intracellular calcium levels, but it induced an increase in PKC activity. Our data show that EGF regulates amino acid uptake, via PKC and without PLC- activation, only in the last period of chick embryo hepatocyte development. The effects of growth factor on PKC activity suggest the involvement of PKC- and - isoforms in EGF modulation of amino acid transport.

Amino Acids↗
PubMed2000

[Comparative study of three feeding methods for draught horses of the Swiss army].

Three feeding methods were compared in 36 4- to 6-year-old Franche-Montagne horses during the military school of St-Luzisteig (GR) of Spring 1992. The horses were separated into 3 groups: a group with the traditional oats-hay ration (OH), a group with a pelleted feed and hay ration (PFH), and a group with the complete diet (CD). Feed analyses were performed and food consumption, eating behavior and digestibility were studied. The horses received their daily amount of feed in 3 portions covering the requirements for a medium work: OH = 8 kg hay and 3 kg oats, PFH = 8 kg hay and 3 kg pelleted feed and CD = 10 kg of the complete diet. For the 3 rations, the amount of digestible crude protein for horses was higher than the reference value for the requirement of a 600 kg horse with a medium work. In the 3 diets, the calcium content was higher than the required 32 g per day (g/d). Not enough sodium (OH: 1.2 g/d; PFH: 7.3 g/d; CD: 9.6 g/d) and too much potassium (OH: 140.3 g/d; PFH 153.0 g/d; CD: 167.5 g/d) were present in the diets, both without consequences for the blood parameters. In 3 meals of 60 minutes, the horses of the group OH, PFH and CD ingested 82%, 89% and 92%, respectively, of the daily ration. The complete diet was ingested more quickly than the hay. The number of mastications per minute was smaller for the complete diet than for the hay. Ingestion times were similar for oats and pelleted feed. However, the number of mastications per minute was smaller for the pelleted feed. The digestibility of nutrients was not influenced by the method of feeding. In conclusion, these results demonstrate that the 3 types of ration studied here are adequate for the swiss army horses if sodium is added to the diet. However, despite the fact that both PFH and CD correct excessive supply or deficiencies of nutrients and despite the fact that these two feeding methods offer nutrients in amounts that are closer to the requirements of the horse, the method PFH was introduced in 1994.

Animal Feed↗
PubMed1999

Abrasive esophageal cytology for the oncological follow-up of patients with head and neck cancer.

OBJECTIVES: The occurrence of a second primary cancer in the esophagus in patients with head and neck squamous cell carcinoma is frequent and is associated with a poor prognosis. The aim of this study was to evaluate the yield of abrasive esophageal cytology as a means of screening for metachronous cancer of the upper aerodigestive tract. STUDY DESIGN: We retrospectively reviewed the results of abrasive esophageal cytology performed twice yearly for the screening of patients with prior head and neck cancer. METHODS: From 1987 to 1996, 320 patients treated for head and neck cancer underwent 1,673 abrasive cytology examinations of the esophagus during a mean follow-up period of 4 years. Cytological results were classified as negative, suspect, or positive for malignancy. RESULTS: Twenty-five patients without symptoms had one or more suspect or positive cytologic findings, leading to 29 endoscopic examinations. These revealed 20 premalignant or early malignant lesions of the esophagus (2 dysplasias, 18 squamous cell carcinomas), 2 glandular carcinomas, and 10 clinically unsuspected oral or pharyngeal carcinomas. In seven patients, positive cytological results were associated with clinically visible head and neck cancer. Of the 34 patients with suspect cytological results for malignancy, 10 had no evidence of tumor at endoscopy and 24 had no endoscopic examination because of refusal or because suspected cells were not found in additional examinations. Negative results on cytological examination were found for 254 patients throughout their follow-up, and none of them developed esophageal cancer during a mean follow-up period of 3 years. CONCLUSIONS: For patients with head and neck cancer, abrasive sponge cytology is useful for detecting esophageal cancer at an early stage. In addition, it may reveal unsuspected second primaries or recurrences in the head and neck region.

Carcinoma, Squamous Cell↗
PubMed1998

Patterns of antimicrobial use and antimicrobial resistance among healthy children in Bolivia.

OBJECTIVE: To determine the incidence of antimicrobial-resistant, nonpathogenic Escherichia coli among healthy children aged 6-72 months in Camiri town and a rural village, Javillo, in south-eastern Bolivia. METHOD: A community-based survey: stool samples were obtained from 296 healthy children selected by modified cluster sampling in Camiri and all 25 eligible children in Javillo. E. coli isolates were tested for antimicrobial susceptibility according to the standard disc diffusion method. By a questionnaire survey of 12 pharmacies and by using simulated patients, we investigated the antimicrobial availability and the usage patterns in Camiri town. RESULTS: In Camiri, over 90%, and in Javillo over 70% of children carried E. coli resistant to ampicillin, trimethoprim-sulphamethoxazole (TMP/SMX) or tetracycline. Overall, 63% of children carried E. coli with multiple resistance to ampicillin, TMP/SMX, tetracycline and chloramphenicol. In the simulated patients study, antimicrobials were dispensed inappropriately for 92% of adults and 40% of children with watery diarrhoea, and were under-prescribed for males with urethral discharge (67%) or females with fever and dysuria (58%). The dose and/or duration of antimicrobials dispensed was almost always too low. CONCLUSION: Our study showed a disturbingly high prevalence of carriage of nonpathogenic E. coli resistant to antimicrobials. The prevalence of resistance to ampicillin and TMP/SMX was higher than that previously reported in developing countries. The existence of a large reservoir of resistance genes in healthy individuals in developing countries represents a threat to the success of antimicrobial therapy throughout the world. Programmes to improve rational and effective drug use in developing countries are urgently needed.

Adult↗
PubMed1996

Changes in the levels of glycerophosphoinositols during differentiation of hepatic and neuronal cells.

Glycerophosphoinositols are metabolites formed by a phosholipase A2 and a lysolipase specifically acting on membrane phosphoinositol lipids. High levels of these compounds characterize epithelial cells and fibroblasts transformed by ras and other cellular oncogenes. Here we have analyzed the glycerophosphoinositol levels in cells that are considered models of cell differentiation. Using rat hepatocytes at different stages of liver development we have shown that the glycerophosphoinositol basal levels of fetal cells were up to fourfold higher than in adult hepatocytes. No changes in glycerophosphoinositol were observed in regenerating rat liver, a model of differentiated cells proliferating in a synchronous manner, where only glycerophosphoinositol 4-phosphate increased by 80%. Similarly to fetal hepatocytes, a modest but significant increase (30%) in the levels of glycerophosphoinositols was observed in undifferentiated NG-108-15 cells as compared to the same cells induced to differentiate by cAMP. In a different neuronal cell line, PC12 cells, increased glycerophosphoinositol levels characterized the differentiated cells. Based on these observations we suggest that high glycerophosphoinositol levels characterize cellular phenomena associated with the activation of ras/mitogen-activated protein kinase pathways.

Animals↗
PubMed1996

EGF responsiveness of hepatocytes after partial hepatectomy.

We investigate the effect of EGF on IP3 production, PLC gamma phosphorylation, calcium transients in rat hepatocytes isolated in quiescent liver (G0 phase of cell cycle) and at 4 h (G1 phase of cell cycle) and 24 h (M phase of cell cycle) after partial hepatectomy. Our results show that EGF does not utilize IP3 and calcium as its signal transduction molecules when the hepatocytes are in vivo stimulated to entry in the cell cycle. In particular the growth factor does not phosphorylate PLC gamma and induces a decrease in IP3 content. These data suggest that EGF utilizes different signal transduction to send information from receptor to nucleus during PH with respect to the quiescent liver.

Animals↗
PubMed1996

EGF modulation of Na+/H+ antiport in rat hepatocytes: different sensitivity in adult and fetal cells.

The modulation by epidermal growth factor (EGF) of the Na+/H+ antiport in fetal and adult rat hepatocytes was studied in nominally HCO3- free solution. EGF (10 nM) activated the antiport in adult rat hepatocytes by 0.22 +/- 0.03 (mean +/- SD;n=10) pH units over basal value, measured with the fluorescent pH-sensitive intracellular probe, 2',7'-bis(carboxyethyl)-5(6)- carboxyfluorescein (BCECF). The effect of EGF was inhibited by amiloride analogue 5-(N-ethyl-N-isopropyl) amiloride (EIPA), by ouabain, inhibitor of the Na+ pump, and by erbstatin analogue, an inhibitor of the tyrosine kinase activity of the EGF receptor. The effect of EGF on Na+/H+ antiport in adult rat hepatocytes appeared to be mediated by both protein kinase C (PKC) and G protein system. No effect of EGF and phorbol 12-myristate 13-acetate, an activator of PKC, on the Na+/H+ antiport was observed in fetal hepatocytes of 20 and 22 days. A different sensitivity of the antiport to high concentrations of amiloride and EIPA suggests that altered amount of the Na+/H+ antiport units or different isoforms could be expressed in fetal compared with adult cells.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1996

[The evaluation of the physical characteristics of a volumetric computer tomograph].

Spiral or volumetric computed tomography (CT) is a new scanning technique which allows the scanning of body regions with a continuously rotating system based on the slip ring technology; the patient is also moved continuously, synchronously with data acquisition. The physical characteristics of spiral CT image acquisition were compared with those of conventional CT images. The modulation transfer function (MTF) has the same values for medium-resolution filters, but lower values for spiral CT for high-resolution and frequency-enhancement filters. The slice sensitivity profile (SSP) describes the longitudinal image resolution for multiplanar reconstructions and was measured in terms of FWHM of the SSP curve. We obtained, for 10-mm slice thickness, a FWHM = 10.4 mm (conventional CT), versus 10.7 mm (Spiral CT), while, for 5-mm slice thickness, the corresponding values were 5.2 mm (conventional CT) and 5.5 mm (spiral CT). Noise was evaluated simply by measuring the standard deviation of the CT numbers, in a region of interest, of a uniform image and with the power spectrum or Wiener spectrum of the same image. To assess overall image quality and yield, the noise equivalent quanta (NEQ) value was also calculated. The values were a little lower for the spiral technique, particularly with high-resolution and enhancement or convolution filters. Dosimetric evaluation of the computed tomography dose index (CTDI) and of the multiple scan average dose (MSAD) was done using an acquisition protocol for average lung dose, in an anthropomorphic phantom and with TL dosimeters. The MSAD was 6.17 +/- 0.20 cGy for conventional CT and 5.98 +/- 0.23 cGy for Spiral CT, while lung dose was 3.25 +/- 0.12 cGy and 3.01 +/- 0.16 cGy, respectively.

Artifacts↗