DFT Study of the Reaction Mechanisms of Carbon Dioxide and its Isoelectronic Molecules CS2 and OCS Dissolved in Pyrrolidinium and Imidazolium Acetate Ionic Liquids

The reaction mechanisms of CO2 and its isoelectronic molecules OCS and CS2 dissolved in N-butyl-N-methylpyrrolidinium acetate and in 1-butyl-3-methylimidazolium acetate were investigated by DFT calculations in "gas phase". The analysis of predicted multistep pathways allowed calculating energies of reaction and energy barriers of the processes. The major role played by the acetate anion in the degradation of the solutes CS2 and OCS as well as in the capture of OCS and CO2 by the imidazolium ring is highlighted. In both ionic liquids, this anion governs the conversion of CS2 into OCS and of OCS into CO2 through interatomic S-O exchanges between the anion and the solutes with formation of thioacetate anions. In imidazolium acetate, the selective capture of CS2 and OCS by the imidazolium ring competes with the S-O exchanges. From the calculated values of the energy barriers a basicity scale of the anions is proposed. The (13)C NMR chemical shifts of the predicted adducts were calculated and agree well with the experimental observations. It is argued that the scenario issued from the calculated pathways is shown qualitatively to be independent from the functionals and basis set used, constitute a valuable tool in the understanding of chemical reactions taking place in liquid phase.

[Very preterm births in French Polynesia: update and proposal for follow-up]

INTRODUCTION

The care of premature infants in French Polynesia is complicated by this country's geographic isolation. We undertook an evaluation of the medical care of very premature infants (VPIs) to find local solutions to this problem.

OBJECTIVES

The objectives were to determine the incidence, mortality, and the short- and long-term outcome of very preterm infants in French Polynesia.

METHODS

We retrospectively reviewed the medical charts of all infants born alive at<32 gestational age (GA) and>24 GA from January 2007 to December 2011. Perinatal characteristics and outcomes were examined by univariate and multivariate analysis.

RESULTS

In total, 204 VPIs were born during the 5-year study period, comprising 0.9% of all births. Infants less than 28 GA comprised 0.1% of all births. Sixty-two percent of mothers were of extreme age including 43% less than 25 years old. Prematurity was attributed to spontaneous preterm labor in 63% of cases and preeclampsia in 29%. Spontaneous multiple pregnancies comprised 15% of the cases. Alcohol and tobacco consumption were frequently noted (>8% and 26% mothers, respectively). Seventy-eight percent of VPIs had received prenatal steroids. Intrauterine growth was normal in 89%. Mortality occurred in 9.3% (19 patients). Mortality was higher with lower gestational age (P<0.05) and absence of prenatal steroids (P<0.05) in univariate and multivariate analysis. The primary cause of death was sepsis. Hyaline membrane disease occurred in 44% of patients, 80% of whom received surfactant therapy. In total, 16.2% newborns developed bronchodysplasia, 3.4% necrotizing enterocolitis, 3% cerebral hemorrhage, and 1.5% leukomalacia. Long-term outcome was marked by 52% of the patients lost to follow-up by 2 years of age, mostly because of geographic isolation. For the 72 patients followed-up, four developed asthma and three cerebral palsy; 70% were attending school by 3 years of age.

CONCLUSIONS

The incidence, mortality, and morbidity of very preterm birth in French Polynesia are comparable to reports from metropolitan centers in France. Conversely, nearly one-half of the patients were lost to follow-up, precluding meaningful information on intellectual development and other outcomes. We recommend organizing a long-term follow-up network to detect cognitive sequelae and adapting such a system to the geographical residence of French Polynesian families.

Evidence of perinatal transmission of Zika virus, French Polynesia, December 2013 and February 2014

Binary file ES_Abstracts_Final_ECDC.txt matches

Assessing the non-ideality of the CO2-CS2 system at molecular level: a Raman scattering study

The dense phase of CO2-CS2 mixtures has been analysed by Raman spectroscopy as a function of the CO2 concentration (0.02-0.95 mole fractions) by varying the pressure (0.5 MPa up to 7.7 MPa) at constant temperature (313 K). The polarised and depolarised spectra of the induced (ν2, ν3) modes of CS2 and of the ν1-2ν2 Fermi resonance dyad of both CO2 and CS2 have been measured. Upon dilution with CO2, the evolution of the spectroscopic observables of all these modes displays a "plateau-like" region in the CO2 mole fraction 0.3-0.7 never previously observed in CO2-organic liquids mixtures. The bandshape and intensity of the induced modes of CS2 are similar to those of pure CS2 up to equimolar concentration, after which variations occur. The preservation of the local ordering from pure CS2 to equimolar concentration together with the non-linear evolution of the spectroscopic observables allows inferring that two solvation regimes exist with a transition occurring in the plateau domain. In the first regime, corresponding to CS2 concentrated mixtures, the liquid phase is segregated with dominant CS2 clusters, whereas, in the second one, CO2 monomers and dimers and CO2-CS2 hetero-dimers coexist dynamically on a picosecond time-scale. It is demonstrated that the subtle interplay between attractive and repulsive interactions which provides a molecular interpretation of the non-ideality of the CO2-CS2 mixture allows rationalizing the volume expansion and the existence of the plateau-like region observed in the pressure-composition diagram previously ascribed to the proximity of an upper critical solution temperature at lower temperatures.

[Capsule endoscopy in children: which are the best indications?]

BACKGROUND AND STUDY AIMS

Capsule endoscopy (CE) is a novel and noninvasive means of investigating the small bowel. In children, the best CE indications have not yet been fully appraised. The aim of this study was to evaluate the diagnostic yield of CE in different pediatric pathologies.

PATIENTS AND METHODS

We retrospectively reviewed every CE performed in children in two French pediatric hospitals between March 2002 and June 2009. Seventy-nine CEs were performed on 70 children (mean age, 10.6 years; range, 2.2-18.0); 52 boys and 18 girls. The indications were iron deficiency anemia (24%), obscure gastrointestinal bleeding (14%), polyposis syndromes (16%), suspected Crohn disease (15%), unresponsive Crohn disease (10%), graft-versus-host disease (10%), and other (10%).

RESULTS

Of the 79 CEs, 69 reached the cecum (87%). Only one occlusion occurred in a case of stenosing Crohn disease, requiring surgical removal. In addition, technical difficulties led to an incomplete small bowel study in 12 cases (16%). The CE showed small bowel lesions in 42 cases (53%). The diagnostic yield was 27% in obscure gastrointestinal bleeding, 37% in iron-deficiency anemia, 42% in suspected Crohn disease, 88% in unresponsive Crohn disease, 62% in polyposis syndromes, and 88% in graft-versus-host disease.

CONCLUSION

In children, CE is well tolerated and can be performed in children as young as 2.2 years of age. Its diagnostic yield is highest in polyposis syndromes, unresponsive Crohn disease, and graft-versus-host disease.

Toxicity and antioxidant activity in vitro and in vivo of two Fucus vesiculosus extracts

The consumption of seaweeds has increased in recent years. However, their adverse and beneficial effects have scarcely been studied. Two extracts from the brown seaweed Fucus vesiculosus containing 28.8% polyphenols or 18% polyphenols plus 0.0012% fucoxanthin have been obtained and studied to determine their toxicity in mice and rats and also their antioxidant activity. Both extracts were shown to lack any relevant toxic effects in an acute toxicity test following a 4 week daily treatment in rats. The extracts exhibited antioxidant activity in noncellular systems and in activated RAW 264.7 macrophages, as well as in ex vivo assays in plasma and erythrocytes, after the 4 week treatment in rats. Our ex vivo results indicated that compounds from extract 2 may be more easily absorbed and that the antioxidants in their parent or metabolized form are more active. These findings support the view that the daily consumption of F. vesiculosus extract 2 (Healsea) would have potential benefits to humans.

Transient dimer formation in supercritical carbon dioxide as seen from Raman scattering

The polarized and depolarized Raman profiles of supercritical CO(2) have been measured in the region of the nu(2) bending mode (forbidden transition at about 668 cm(-1)) and for the Fermi dyad (1285 and 1388 cm(-1)) along the isotherms 307, 309, 313, and 323 K in a reduced density domain 0.04<rho*=rhorho(C)<2.04 (rho(C) approximately 467.6 kg m(-3), rho(C) is the critical density). The spectral features associated with the nu(2) mode (degeneracy removal of the mode and Raman intensity activation) are found to be due to the formation of transient complexes. This is supported by the spectral signatures predicted for parallel slipped dimer and trimers (cyclic and noncyclic) from ab initio calculations taking into account the frequency anharmonicity. The band-shape analysis of the Fermi doublet (observed in the spectral range of 1260-1400 cm(-1)) shows that on the subpicosecond time scale of the Raman spectroscopy, a tagged CO(2) molecule probed two kinds of environment in its first shell of neighbors independent of local density enhancement phenomenon. The first one involves interactions of CO(2) with surrounding molecules in the first shell whereas the latter is associated with a transient dimer formation. Finally, a broad band observed between the Fermi dyad (at about 1335 cm(-1)) is assessed from symmetry considerations and from its depolarization ratio as a further evidence of transient complex formation in supercritical CO(2).

Liposomal formulation of a glycerolipidic prodrug for lymphatic delivery of didanosine via oral route

Didanosine is a polar drug with poor membrane absorption and high hepatic first pass metabolism. This study aimed at developing a lipidic formulation of a glycerolipidic prodrug of didanosine in order to improve its bioavailability. In the course of a preformulation study, the glycerolipidic prodrug of didanosine was characterized by microscopy, DSC and XRDT. In anhydrous conditions, the prodrug displayed a polymorphic behaviour similar to that of triglycerides. Then, we evaluated three types of lipidic formulations (emulsions, mixed micelles and liposomes) in order to encapsulate the prodrug. Solubilities in water - even in the presence of taurocholate micelles - but also in some oils were very low (max 244 microg/mL) as the prodrug was found to be amphiphilic (log P=2). On the contrary, the prodrug was found to be perfectly incorporated in dipalmitoylphosphatidylcholine (DPPC) multilamellar liposomes up to a ratio of 1:5 (mol:mol) prodrug:DPPC as suggested by HPLC-UV and DSC experiments. Moreover, these liposomes could be freeze-dried whereas the chemical integrity of the prodrug was preserved. Then, the freeze-dried liposomal preparation could be formulated as gastro-resistant capsules to prevent didanosine from acidic degradation. Further experiments are on the way to evaluate in vitro the absorption of prodrug incorporated in liposomes by enterocytes.

Water-carbon dioxide mixtures at high temperatures and pressures: local order in the water rich phase investigated by vibrational spectroscopy

Raman scattering combined with near- and mid-infrared absorption spectroscopies was used to investigate the evolution of the local order in the water rich phase of water-CO(2) mixtures under isobaric heating (T=40-360 degrees C, P=250 bars). The quantitative analysis of the spectra shows that tetramers and larger oligomers are the main constituents of water at moderate temperatures below 80 degrees C. As the temperature increases, the dimer and trimer concentrations considerably increase at the expense of larger oligomers. Finally, water dimers are predominant at the highest temperature investigated close to the temperature of total miscibility of the mixture (T=366 degrees C, P=250 bars). This result is consistent with our previous investigation [R. Oparin T. Tassaing, Y. Danten, and M. Besnard, J. Chem. Phys. 120, 10691 (2004)] on water dissolved in the CO(2) rich phase where we found that close to the temperature of total miscibility water also exists mainly under dimeric form. The current study combined with that mentioned above provides a model investigation of the evolution of the state of aggregation of water molecules in binary mixture involving a hydrophobic solvent in a wide range of temperature.

Hydrogen bonding in liquid and supercritical 1-octanol and 2-octanol assessed by near and midinfrared spectroscopy

The near and midinfrared spectra of 1-octanol (and 2-octanol) have been measured along the liquid-gas coexistence curve from room temperature up to the critical point and in the supercritical domain along the isotherm T=385 degrees C (and T=365 degrees C) above the critical point of both 1-octanol and 2-octanol for pressure ranging from 0.5 up to 15 MPa. The density values of SC 1- and 2-octanol have been estimated by analysing the near infrared (NIR) spectra in the 3nu(a)(CH) region. A quantitative analysis of the absorption band associated with the OH stretching vibration [nu(OH)] and its first and second overtones [2nu(OH) and 3nu(OH)] was carried out in order to estimate the percentage of "free" OH groups in both alcohols in the whole thermodynamic domain investigated here. Very consistent results have been obtained from the independent analysis of these three different absorption bands which gave us a good confidence in the degree of hydrogen bonding reported here for 1- and 2-octanol. Thus, the percentage of free OH groups which is around 5% in liquid 1-octanol under ambient conditions strongly increase up to 70%-80% at a temperature of about 340 degrees C. Then, in the supercritical domain, upon a decrease of the density from 0.4 to 0.1 g cm(-3), the fraction of free hydroxyl groups is nearly constant presenting a plateaulike regime around 80%. As the density decreases again, this plateau regime is followed by a further increase of X(nb) which reaches a value of 96% for the system in the gaseous phase (0.01 g cm(-3); P=0.45 MPa). Finally, it comes out from this study that the percentage of free OH groups is always greater in 2-octanol than in 1-octanol at the same density.

Encapsulation of antiviral nucleotide analogues azidothymidine-triphosphate and cidofovir in poly(iso-butylcyanoacrylate) nanocapsules

Nucleoside analogues are widely used in the treatment of various viral infections. However, the poor in vivo conversion of the nucleoside analogues like azidothymidine (AZT) into their active triphosphate nucleotide counterpart limits their pharmacological efficacy. This could be overcome by the direct administration of azidothymidine triphosphate (AZT-TP), but it requires an appropriate drug delivery approach. Besides nucleoside analogues, nucleotide analogues like cidofovir (CDV) are also used in the treatment of viral infections. CDV has raised recent interest because of its promising activity against smallpox, but its use is limited by its poor bioavailability and nephrotoxicity. Here again, a proper drug delivery system should address these issues. In this study, we investigated the encapsulation of the nucleotide analogues AZT-TP and CDV into poly(iso-butylcyanoacrylate) aqueous core nanocapsules, known to efficiently entrap oligonucleotides. We show here that the encapsulation of these mono-nucleotides is less efficient than with oligonucleotides and that a rapid release of AZT-TP from the nanocapsules occurred in vitro. This highlights the importance of the molecular weight of the entrapped molecules which, if they are too small, are diffusing through the thin polymer membrane of the nanocapsules. On the other hand, a good protection of the encapsulated AZT-TP was observed.

Density Functional Theory (DFT) Calculations of the Infrared Absorption Spectra of Acetaminophen Complexes Formed with Ethanol and Acetone Species

We have investigated the infrared (IR) vibrational spectra of acetaminophen (N(4-hydroxyphenyl) acetamide or paracetamol) complexes formed with ethanol and acetone in relation to the nature of the specific intermolecular interactions involved in the stabilization of the complexes. The structures and binding energies of the complexes have been determined using Hartree-Fock (HF) and DFT-B3PW91 procedures and different Pople's basis sets as well. The main results are presented and discussed by considering the hydroxyl (OH), amino (NH), and carbonyl (CO) chemical groups of acetaminophen interacting with the acetone or ethanol molecules either separately or in conjunction in the complex formation. The frequency shifts and IR intensity variations associated with the internal modes of acetaminophen (namely nu(OH), nu(NH), and nu(CO)) as well as the most pertinent vibrational probes of ethanol (nu(OH)) and acetone (symmetric nu(CO) and nu(CCC) stretching modes) interacting with acetaminophen have been analyzed. The predicted spectral changes have been critically discussed in comparison with IR absorption measurements of acetaminophen dissolved as a solute in ethanol or acetone CO2 expanded solutions. It is argued that the exchange-correlation contribution taken into account in DFT calculations is likely significant in determining the main IR spectral features of acetaminophen complexes formed with acetone or involving hydrogen-bonded as with ethanol.

Infrared and molecular-dynamics studies of the rotational dynamics of water highly diluted in supercritical CO2

Far-infrared (FIR) and mid-infrared (MIR) profiles of D2O infinitely dilute in supercritical CO2 have been studied using molecular-dynamics simulations. For this purpose, we have proposed an intermolecular potential model taking implicitly into account electron donor-acceptor (EDA) interactions between water and CO2 evaluated from ab initio calculations of the intermolecular potential-energy surface (IPS). Interaction-induced dipole mechanisms have been also taken into account in addition to the water permanent dipole to evaluate the simulated FIR profiles of water and CO2 polarizable molecules. They were found to play a minor role in the genesis of the FIR profiles of water/CO2 under supercritical conditions. The analysis of the reorientational dynamics of D2O shows that the rotational dynamics of water is weakly anisotropic due to the EDA interactions which affect more specifically the reorientational motions of the C2 symmetry axis of solute. These results have been used to assess the contribution of the vibrational relaxation in the experimental mid-infrared profiles associated with the nu1 symmetric and nu3 antisymmetric stretching and nu2 bending modes of D2O. It was found that the rotational dynamics mainly contribute to the broadening of the infrared (IR) profiles. Nevertheless, the vibrational processes play a role in the frequency shifts of the band centers and the relative intensity enhancements of the nu1 and nu3 modes of D2O. In particular, the EDA interactions between water and CO2 lead to the appearance of a well-defined IR band of the nu1 mode of D2O. Finally, a comparison with another model taking only into account dipole-quadrupole electrostatic interactions between water and CO2 molecules clearly reveals that EDA interactions have to be considered to reproduce both MIR and FIR measurements. From this point of view CO2 can be classified on a hydrophilic solvent scale based upon the solubility criterion as an intermediate solvent between "inert" xenon and carbon tetrachloride.

Hydrogen bonding in supercritical tert-butanol assessed by vibrational spectroscopies and molecular-dynamics simulations

We have investigated the state of aggregation in supercritical tert-butanol (T = 523 K,0.05 < rho < 0.4 g cm(-3)) by means of vibrational spectroscopies (infrared and Raman) and molecular-dynamics (MD) simulations. A quantitative band shape analysis of the spectra associated with the OH stretching mode of tert-butanol has been done using activities computed by ab initio calculations on small clusters. This allows us to determine the degree of hydrogen bonding and populations of oligomers. These latter quantities have been derived from MD simulations and very consistent results are found with experiments. These results show that hydrogen bond still exist in supercritical tert-butanol and that the fluid mainly consists of oligomers smaller than tetramers.

Ab Initio Investigation of Vibrational Spectra of Water−(CO2)n Complexes (n = 1, 2)

In this paper, we have calculated using the ab initio method the IR vibrational spectra of complexes of CO2 formed with water (sp3 O-donating atom). Binding energies and structures of the CO2-H2O and water-(CO2)2 complexes have been determined at the second-order level of the Moller-Plesset perturbation theory (MP2) using Dunning's basis sets. The results are presented and critically discussed in terms of the nature of the water-CO2 interactions, electron donor acceptor (EDA) and weak O...H-O interactions. For water-(CO2)2 trimer, it is also shown that the contribution to the interaction energy of the irreducible three-bodies remains relatively negligible. We have analyzed the frequency shifts and the IR and Raman intensity variations under the complex formation. We have particularly emphasized the splitting of the 2 bending mode of CO2 and stretching modes of water, which have been revealed as the most pertinent probes to assess the nature of the forces involved in the different complexes. Finally, because water can play the role of Lewis base and acid as well, we found that weak O...H-O interactions can cooperate with EDA interactions in trimer, leading to very specific spectral signatures that are further discussed.

Compaction of crystallographic forms of pharmaceutical granular lactoses. I. Compressibility

Physico-chemical properties of a substance including the compaction behaviour are directly connected with the crystalline structure. The aim of this work is to compare the compaction behaviour in a group of excipient and in this first part, to display the influence of lactose structures on the compressibility. alpha-Lactose monohydrate (LalphaM), anhydrous beta-lactose (LbetaA), anhydrous alpha-lactose (LalphaA) and partly amorphous lactose (FF) were compressed using instrumented presses to investigate the densification behaviour under pressure. Force-displacement curves were associated to two energy parameters, specific cycle energy and specific expansion energy. This approach was used to class the four lactose species. It is possible to differentiate three groups with the specific energy cycle, FF, LalphaA/LbetaA and LalphaM in decreasing order of this energy. At the same time, the values of specific expansion energy are relatively low for FF and LalphaA contrary to LalphaM and LbetaA. Then, Heckel's plots were obtained with two compact geometries and the mean yield pressure was calculated from the in-die-method and the out-of-die-method. Two lactoses seem to differ, LalphaM appears to be the most ductile whereas LalphaA is more brittle than the others. Finally, it is concluded, that in the case of lactoses, pseudopolymorphism seems to affect the compressibility more than anomerisation or partial amorphisation.

Structural evolution of aqueous NaCl solutions dissolved in supercritical carbon dioxide under isobaric heating by mid and near infrared spectroscopy

The local order in aqueous NaCl solutions diluted in supercritical carbon dioxide at constant pressure as a function of NaCl concentration and temperature has been investigated using near and mid infrared absorption spectroscopy. The near IR results have allowed us to estimate the water concentration in CO(2) rich phase, whereas the state of water aggregation in CO(2) phase was investigated using mid IR spectroscopy. The analysis of the band shape variations of the OD stretching mode of HOD led us to conclude that below 100 degrees C, water molecules dissolved in CO(2) exist only under their monomeric form, whatever the salt concentration is, whereas hydrogen-bonded species, namely, dimers start to appear at higher temperatures. Larger aggregates have a negligible concentration in the range of temperature-pressure investigated. Using near and mid infrared data, we have calculated the concentrations of water species in the CO(2) phase. Upon heating, it was found that the concentration of dimers considerably increases at the expense of the monomers and only dimers are detected in carbon dioxide at highest temperatures. Changing the salt concentration affects significantly the concentration of monomers and decreases strongly the dimers population as the solution becomes progressively saturated in salt. In the saturated solution, at 340 degrees C, the dimer concentration is at least two times smaller than in the binary water-CO(2) mixture. These findings are in qualitative agreement with existing thermodynamics data showing that addition of NaCl to the binary H(2)O-CO(2) system shifts the range of partial miscibility of water and CO(2) towards higher pressure and temperature.

A vibrational spectroscopic study of structure evolution of water dissolved in supercritical carbon dioxide under isobaric heating

A combination of Raman scattering spectroscopy and infrared absorption was applied to investigate the structural evolution of water dissolved in supercritical carbon dioxide under isobaric heating (T=40-340 degrees C, P=250 bar). Quantitative analysis of experimental spectra allowed us to determine that at relatively moderate temperatures water dissolved in CO(2)-rich phase exists only under monomeric form (solitary water surrounding by CO(2) molecules), but hydrogen-bonded species, namely, dimers, begin to appear upon heating. At the same time, the ratio of dimers to monomers concentration increases with further temperature increase and at temperatures close to the temperature of total miscibility of the mixture (T=366 degrees C, P=250 bar), water dimers only are present in the CO(2)-rich phase.

[Failure to thrive and intestinal diseases in congenital disorders of glycosylation]

Congenital disorders of glycosylation type I (GDG-I) is a class of genetic multisystem disorders characterised by defective glycosylation of glycoproteins. The characteristics and mechanisms of failure to thrive and intestinal diseases present in CDG-I are anectodal.

PATIENTS AND METHODS

The aim of this study was to analyse 7 CDG-I (4 CDG-Ia, 2 CDG-Ib and 1 CDG-Ix) with important digestive symptoms and failure to thrive in order to characterise the mechanisms implied.

RESULTS

Four children had no skin abnormality or dysmorphia (1 CDG-Ia, 2 CDG-Ib, 1 CDG-Ix). An encephalopathy with cerebellar hypoplasia was present only in the 4 CDG-Ia. Failure to thrive and diarrhea were present during the first month of life in 6 and appeared at 5 years in one CDG-Ia associated to mild or severe hepatopathy in all patients. One CDG-Ia, 1 CDG-Ib, 1 CDG-Ix had an exsudative enteropathy. A positive steatorrhea was present in 3 patients. Five patients had an abnormal small bowel biopsy. Abnormalities were variable: moderate inflammation of the chorion without villous atrophy in 2, intra-enterocyte fat accumulation without villous atrophy in 2, and partial villous atrophy with lymphangectasia in 1. In 2 CDG-Ia the intestinal biopsy was normal. Enteral nutrition in 4 and parenteral nutrition in 2 were effective in 4 patients and 1 patient with an exsudative enteropathy respond to a free fat diet (CDG-Ix).

CONCLUSION

The digestive symptoms with failure to thrive is a common feature of CDG-I and could be the first symptoms. The diagnostic should be suspected if no other cause is found. Mechanisms of the intestinal symptoms appear to be multiple such as inflammation, abnormal enterocyte lipid transport or intestinal permeability related to the abnormal glycosylation of intestinal mucosa glycoproteins.

Biodegradable microparticles for the controlled delivery of oligonucleotides

Microspheres allowing the controlled release of the model oligonucleotide pdT16 were designed. The oligonucleotide, alone or associated with polyethylenimine (PEI) at different nitrogen/phosphate ratios, was encapsulated within poly(lactide-co-glycolide) microspheres prepared by the multiple emulsion-solvent evaporation technique. The introduction of PEI in the internal aqueous phase resulted in a strong increase of the oligonucleotide encapsulation efficiency. PEI affected also microsphere morphology inducing the formation of very porous particles and yielding to an accelerated release of pdT16. However, when incubated with HeLa cells, microspheres encapsulating pdT16/PEI complexes allowed an improvement of the intracellular penetration of the released oligonucleotide. The developed strategy appears to be a very interesting tool to obtain a sustained release system for oligonucleotides with an efficient cellular delivery.

[Long-term followup of primary intestinal lymphangiectasia in the child. Six case reports]

Primary intestinal lymphangiectasia induce symptoms of protein-losing gastroenteropathy. Only very few studies evaluate the long term follow up of such patients. We reviewed six children diagnosed at 17 +/- 12 months and followed for 11 +/- 4.9 years.

CASE REPORTS

As soon as the diagnosis was made the patients were submitted to a strict low fat diet with added medium chain triglycerides and intermittent liposoluble vitamins perfusions. The diet allowed the disappearance of symptoms for all the patients but laboratory findings indicated continuing chyle leak for most of the children. Only one child who had normal biological parameters tolerates a normal diet since four years. Relaxation of the diet by two patients who had moderate hypoalbuminemia and lymphopenia led to severe clinical relapses 14 and 17 years after the diagnosis period with therapeutic difficulties. Three patients with long term strict low fat diet remain asymptomatic.

CONCLUSION

In most asymptomatic patients, the underlying lymphatic defect remains with permanent biological abnormalities. Clinical relapses may be severe and difficult to treat; thus the need for dietary treatment appears to be permanent.

Long-term results of cryopreserved arterial allograft reconstruction in infected prosthetic grafts and mycotic aneurysms of the abdominal aorta

PURPOSE

This prospective, observational study determined the long-term outcome in patients with abdominal aortic infection (primary or prosthetic graft) who were treated with simultaneous aortic/graft excision and cryopreserved arterial allograft reconstruction.

METHODS

From April 1992 to March 2000, patients with abdominal aortic infection underwent complete or partial excision of the infected aorta/prosthetic graft and cryopreserved arterial allograft reconstruction. Arterial allografts were harvested from multiple organ donors and cryopreserved at -80 degrees C without rate-controlled freezing. The patients were observed for survival, limb salvage, persistence and/or recurrence of infection, and allograft patency. The results were calculated with life-table methods.

RESULTS

During the 8-year study period, 28 consecutive patients (27 men, 1 woman; mean age, 64 years) underwent treatment for abdominal aortic infection (23 graft infections, including 7 graft-enteric fistulas and 5 primary aortic infections). Allograft reconstruction was performed as an emergency procedure in 13 patients (46%). The mean follow-up period was 35.4 months (range, 6-101 months). The overall treatment-related mortality rate was 17.8% (17% for graft infection, 20% for primary aortic infection). The overall 3-year survival was 67%. There was no early or late amputation. There was no persistent or recurrent infection, and none of the patients received long-term (> 3 months) antibiotic therapy. Reoperation for allograft revision, excision, or replacement was necessary in four patients (17%) who were available for examination, with no reoperative perioperative death. The 3-year primary and secondary allograft patency rates were 81% and 96%, respectively.

CONCLUSION

Our experience with cryopreserved arterial allograft in the management of abdominal aortic infection suggests that this technique seems to be a useful option for treating one of the most dreaded vascular complications.

Tamoxifen encapsulation within polyethylene glycol-coated nanospheres. A new antiestrogen formulation

When dealing with solid tumors in vivo, pegylated long-circulating carrier systems show, after intravenous administration, an attractive extravasation profile with an enhanced localization in the tumoral interstitium. These systems could be of help for the delivery of cancer fighting drugs, such as Tamoxifen, a well known antiestrogen used in breast cancer therapy that possesses an extended biodistribution in vivo. This work aimed at encapsulating Tamoxifen in long-circulating poly(MePEGcyanoacrylate-co-hexadecylcyanoacrylate) 1:4 nanospheres. Tamoxifen-loaded poly(MePEGcyanoacrylate-co-hexadecylcyanoacrylate) nanospheres were successfully synthesized and characterized in terms of hydrophilicity/hydrophobicity by a model made up from near infrared spectra using principal component analysis. Zeta potential, drug loading, encapsulation efficiency, as well as biological effect, in vitro release and nanospheres integrity were also investigated. Even though near infrared spectroscopy could not detect Tamoxifen, it revealed that Pluronic F68 was associated with the pegylated nanospheres. HPLC measurements demonstrated that Tamoxifen was encapsulated in the pegylated nanospheres following a partition equilibrium between the polymeric and the aqueous phases. The Tamoxifen encapsulated in the nanospheres still showed a transcription inhibitory activity in ex vivo experiments. However, zeta potential and in vitro release suggested that Tamoxifen was essentially localized at the nanoparticles surface, resulting in an important and immediate drug release.

Contributions of the different extramembranous domains of the mechanosensitive ion channel MscL to its response to membrane tension

MscL is a mechanosensitive channel that is gated by tension in the membrane bilayer alone. It is a homo-oligomer of a protein comprising two transmembrane segments connected by an external loop, with the NH(2) and COOH termini located in the cytoplasm. The contributions of the extramembranous domains of the channel to its activity were investigated by specific proteolysis during patch-clamp experiments. Limited proteolysis of the COOH terminus or the NH(2) terminus increased the mechanosensitivity of the channel without changing its conductance. Strikingly, after cleavage of the external loop of each monomer, the channel was still functional, and its mechanosensitivity was increased dramatically, indicating that the loop acts as a spring that resists the opening of the channel and promotes its closure when it is open. These results indicate that the integrity of most of the extramembranous domains is not essential for mechanosensitivity. They suggest that these domains counteract the movement of the transmembrane helices to which they are connected, thus setting the level of sensitivity of the channel to tension.

Intestinal pseudo-obstruction and acute pandysautonomia associated with Epstein-Barr virus infection

We report the association of neurological and intestinal disorders with the reactivation of Epstein-Barr virus (EBV) in a child. This previously healthy 13-yr-old boy presented with pharyngitis and acute abdominal ileus. Laparotomy excluded a mechanical obstruction. Postoperatively, he suffered from prolonged intestinal obstruction, pandysautonomia, and encephalomyelitis. Histological examination of the appendix and a rectal biopsy taken 3 months after the onset showed an absence of ganglion cells (appendix) and hypoganglionosis (rectum), with a mononucleate inflammatory infiltrate in close contact with the myenteric neural plexuses. EBV-PCR was positive in the blood and cerebrospinal fluid, and in situ hybridization with the Epstein-Barr virus encoded RNA probe showed positive cells throughout the appendix wall including the myenteric area, in a mesenteric lymph node, and in the gastric biopsies. EBV spontaneous lymphocytic proliferation was noted in the blood. The serology for EBV showed previous infection but anti-early antigen antibodies were present. No immunodeficiency was found. Neurological and GI recovery occurred after 6 months of parenteral nutrition and bethanechol. The omnipresence of EBV associated with the neurointestinal symptoms suggest that the virus was the causal agent. This is the first documented case of acquired hypoganglionnosis due to EBV reactivation.

Stealth PEGylated polycyanoacrylate nanoparticles for intravenous administration and splenic targeting

The aim of the present work was to investigate the biodistribution characteristics of PEG-coated polycyanoacrylate nanoparticles prepared by the nanoprecipitation/solvent diffusion method using the previously synthesized poly(MePEGcyanoacrylate-hexadecylcyanoacrylate) copolymer. It was observed that [14C]-radiolabeled PEGylated nanoparticles remained for a longer time in the blood circulation after intravenous administration to mice, compared to the non-PEGylated poly(hexadecylcyanoacrylate) (PHDCA) nanoparticles. Furthermore, hepatic accumulation was dramatically reduced, whereas a highly increased spleen uptake was shown. The PEGylation degree of the polymer seemed not to affect the in vivo behavior of the nanoparticles, whereas previously obtained in vitro data have shown a modification of plasma protein adsorption depending on the density of PEG at the surface of the particles. Moreover, the study of the in vitro cytotoxicity of the nanoparticles revealed that the PEGylation of the cyanoacrylate polymer reduced its toxicity. These results open up interesting perspectives for the targeting of drugs to other tissues than the liver.