Theoretical study of mechanisms for the hydrolytic deamination of cytosine via steered molecular dynamic simulations.

Gibbs free energy profiles of the cytosine deamination assisted by a water molecule in a discrete aqueous medium were obtained by the application of Steered Molecular Dynamic (SMD) simulations. Two pathways were considered to explain the mechanism of this process, where the water molecule attacks the C-N bond to give an intermediate (an amino-hydroxy-oxo structure in the A-path, and a hydroxy-oxo in the B-path) as the determinant step of reaction. Stationary structures along both energy profiles were analyzed at molecular dynamics level, obtaining states with higher free energies than those from electronic calculations in the gas phase and in solution described as a continuous medium. From the results obtained, the more complex A-pathway, with five steps, was kinetically the most favorable (with an endergonic reaction energy of 7.41 kcal mol-1, a high barrier of 67.53 kcal mol-1, and a small velocity constant k 2 = 1.80 × 10-37 s-1), concluding that the uracil base can participate in a spontaneous genetic mutation since the uracil-ammonia complex has a long lifetime of 6.10 × 1027 s. This process turns out exergonic and faster when carried out in gas phase simulation or electronic calculation with a continuous medium, due to the disappearance of explicit water molecules that can compete with the assistant molecule.

[Congenital intrahepatic portacaval anastomosis: analysis of manifested glucose abnormalities]. / Anastomose congénitale porto-cave intra-hépatique; analyse des anomalies glucidiques révélatrices.

The authors report a case of a high-flow intrahepatic portacaval shunt due to a congenital venous abnormality. Suspected by digestive echography, the abnormality was confirmed by angiography. A precise analysis of glycoregulation showed an "impaired glucose tolerance", followed by post-stimulative hypoglycemia with persistant hyperinsulinemia and lowering of the C peptide/insulin ratio. These abnormalities seem to be related to the shunt only. This observation appears as an experimental model permitting the appreciation of the disturbances in glucose metabolism related to an intrahepatic shunt without any hepatic cell disorder.

[The ductus bump. Transient dilatation of the ductus arteriosus (author's transl)]. / Le ductus bump. Dilatation transitoire du canal artériel.

Transient, physiologic and rare, dilatation of the ductus arteriosus in asymptomatic neonates, shown by left superior mediastinal mass. It appears only on the PA chest roentgenogram, with vascular characteristics. It disappears after three or four days of regular checking and the diagnosis is thus confirmed, cutting out any other mediastinal pathology. There is no need to use more stressing or ruder technics.

[Sinusitis of the middle turbinate. Descriptive study and treatment]. / Sinusites du cornet moyen. Etude descriptive et traitement.

The middle turbinate inflammatory disease is a well a clinical as a radiological reality which is often unknown because of the rich sinusal surrounding diseases. This pathology represents less than 2% of the total sinusal pathologies we meet daily, and it always occurs on a concha bullosa: the middle turbinate becomes a real sinusal cavity with its own diseases. The new methods of diagnosis, nasal endoscopy and CT scanning, let identifie this turbinal own pathology better than ever. The authors emphasize a surgical treatment.

[Giant cementifying fibroma of the maxillary sinus. Apropos of a case]. / Fibrome cémentifiant géant du sinus maxillaire. A propos d'un cas.

The case of a patient presenting with a gigantiform fibrous cementoma of the maxillary sinus is described. The diagnostic, the treatment and the histologic classification of the cementifying tumours is reviewed in light of the present literature.

[Hazards and complications of ethmoidal surgery]. / Dangers et complications de la chirurgie éthmoïdale.

The most important publications concerning the complications following transnasal ethmoid surgery are reviewed by the authors who underline the dangers in this type of surgery: meninges, the orbit and orbital elements especially the muscles, the extra-orbital portion of the optic nerve and the internal carotid artery. A great prudence during surgical procedure is emphasized as well as the necessity of a perfect knowledge in scannographic and endoscopic anatomy of ethmoid to avoid the inflation of these complications.

[Evaluation of cochleovestibular sequelae of craniocervical injuries]. / Evaluation des séquelles cochléo-vestibulaires des traumatismes cranio-cervicaux.

After reviewing the elements of cochleovestibular assessment designed to demonstrate objective disorders, the authors try to evaluate the principal sequelae of cranio-cervical trauma.

Quasi-classical trajectory calculations analyzing the role of bending mode excitations of methane in the Cl + CH4 reaction.

The effects of the methane torsional (nu(2)), umbrella (nu(4)), and the combination nu(2)+nu(4) bending mode excitations on the reactivity and dynamics of the gas-phase Cl + CH(4) --> HCl + CH(3) reaction were analyzed. Quasi-classical trajectory (QCT) calculations, including corrections to avoid zero-point energy leakage along the trajectories, were used on an analytical potential energy surface previously developed by our group. With respect to the reactivity, we found that excitation of either bending mode independently gave similar increases in the reactivity, while the increase observed upon excitation of both modes was larger than the sum of the effect of exciting them independently. Both results agree with recent experimental measures. With respect to the dynamics (rotovibrational and angular distributions of the products), the two bending modes and their combination gave very similar pictures, reproducing the experimental behavior. The satisfactory agreement obtained with a great variety of experimental data (always qualitatively acceptable and sometimes even quantitatively) of the present QCT study lends confidence to the potential energy surface constructed by our group.

Quasiclassical trajectory calculations comparing the reactivity and dynamics of symmetric and asymmetric stretch and the role of the bending mode excitations of methane in the Cl + CH4 reaction.

To analyze the effects of the symmetric (nu(1)) and asymmetric (nu(3)) stretch mode excitations and the role played by the "umbrella" bending (nu(4)) mode excitation in the reactivity and the dynamics of the gas-phase Cl+CH(4) reaction, an exhaustive dynamics study was performed. Quasiclassical trajectory (QCT) calculations, including corrections to avoid zero-point energy leakage along the trajectories, were used in this work on an analytical potential energy surface previously developed by Espinosa-Garcia et al. [J. Chem. Phys. (to be published)]. First, with respect to the reactivity, we found that the nu(1) mode excitation is more reactive than the nu(3) mode by a factor of 1.20, in agreement with the experimental tendency between these modes. The inclusion of the nu(4) bending mode practically does not affect this relative reactivity, (nu(1+)nu(4))(nu(3+)nu(4)) = 1.16. Second, with respect to the dynamics (rotovibrational and angular distributions of the products), the two stretch modes, nu(1) and nu(3), give very similar pictures, reproducing the experimental behavior, and the nu(4) "umbrella" mode does not affect the dynamics. The satisfactory reproduction (always qualitatively acceptable and sometimes even quantitatively) of a great variety of experimental data by the QCT study presented here lends confidence to the potential energy surface constructed by Espinosa-Garcia et al. [J. Chem. Phys. (to be published)].

Product angular distribution for the H + CD4 --> HD + CD3 reaction.

Using an analytical potential energy surface previously developed by our group, namely PES-2002, we analyzed the gas-phase reaction between a hydrogen atom and perdeuterated methane. We studied the effect of quasiclassical trajectory (QCT) and reduced dimensionality quantum-scattering (QM) calculations, with their respective limitations, on CD3 product angular distributions in the collision energy range 16.1-46.1 kcal x mol(-1). It was found that at low collision energy, 16.1 kcal x mol(-1), both the QCT and QM calculations yielded forward scattered CD3 products, i.e., a rebound mechanism. However, at high energies only the QM calculations on the PES-2002 surface reproduced the angular scattering found experimentally.

[Meningeal injury during surgery of the ethmoid sinus: endoscopic treatment using surgical glue]. / Plaie méningée au cours de la chirurgie ethmoïdale: traitement endoscopique par colle chirurgicale.

A case of a meningeal injury with CSF leak due to intranasal ethmoidal surgery is reported. Fibrinogen glue was used for the endoscopic repair. The importance of the immediate follow-up is stressed. The literature is revised.

[A simple evaluation of osteoporosis: study of the architecture of the upper extremity of the femur by pelvic radiography]. / Une évaluation simple de l'ostéoporose: étude de l'architecture de l'extrémité supérieure du fémur sur la radiographie du bassin.

From the study of the architectural features of the system connecting the neck to the femoral diaphysis on pelvic radio-grams, osteoporosis can be classified into seven stages (7 to 1) of increasing severity. It is thus possible to estimate the risk of fracture, the latter being over 50 per cent from stage 4 onward. The cortex-diaphysis relationship (RCD) follows a parallel course but is less reliable. The investigation of a control group of 20 subjects and 37 patients with osteoporosis, aged 50 to over 80, shows the value of this method, with which it is moreover possible to check the evolution of the disease and the effects of treatment.

Comparison of the cryoprotectant properties of glycerol and ethylene glycol for early (day 6) equine embryos.

Early (day 6) equine embryos (n=23) were assigned to four treatment groups to assess the cryoprotectant properties of glycerol and ethylene glycol and the effect of adding sucrose during removal of the cryoprotectant: (i) group GG (n=5) embryos were frozen and thawed using 1.5 mol glycerol l(-1) as the cryoprotectant, which was added at 22 degrees C in four steps (0.375, 0.75, 1.125 and 1.5 mol glycerol l(-1)), and removed after thawing in five steps (1.5, 1.125, 0.75, 0.375 and 0.0 mol glycerol l(-1)); (ii) group GS (n=6) embryos were frozen and thawed using 1.5 mol glycerol l(-1) as for group GG, except that 0.25 mol sucrose l(-1) was added during removal of the glycerol; (iii) group EE (n = 6) embryos were frozen and thawed using 1.5 mol ethylene glycol l(-1) as the cryoprotectant, which was added in three steps (0.5, 1.0 and 1.5 mol ethylene glycol l(-1)) and removed after thawing in four steps (1.5, 1.0, 0.5, 0.0 mol ethylene glycol l(-1)); and (iv) group ES (n = 6) embryos were frozen and thawed using 1.5 mol ethylene glycol l(-1) as for group EE, except that 0.25 mol sucrose l(-1) was added during removal of the ethylene glycol. After thawing, the embryos were incubated at 37 degrees C in Ham's F10 medium supplemented with 10% (v/v) fetal calf serum and antibiotics, in 5% CO2 in air for 6 h. The embryos were fixed in glutaraldehyde, serially sectioned and observed using light microscopy. None of the frozen-thawed embryos treated with ethylene glycol (groups EE and ES) had any viable cells. There were no lysed cells in the frozen-thawed embryos treated with glycerol (groups GG and GS) and the proportion of cells with pyknotic nuclei was low (group GG = 1.1 +/- 0.8% and group GS = 2.5 +/- 1.5%). There were no differences between embryos treated with cyroprotectant diluted with or without sucrose. The embryos were morulae or early blastocysts and either did not have a capsule or had a very thin capsule. The results of the present study confirm that ethylene glycol is a poor cryoprotectant for early equine embryos and that the use of sucrose during dilution of the cryoprotectant after thawing does not improve the morphology of the embryos. The results of this study also indicate that glycerol is an effective cryoprotectant for freezing equine embryos with intact zonae pellucidae and with either very thin or no capsules.