Fluorinated porous organic frameworks for improved CO2 and CH4 capture.

A porous 3D selectively fluorinated framework (F-PAF1), robust yet flexible and with a surface area of 2050 m2 g-1, was synthesised by condensation of an ad hoc prepared fluorinated tetraphenylmethane (TPM) monomer to ensure homogenously distributed C-F dipoles in the swellable architecture. Tetradentate TPM was also the comonomer for the reaction with fluorinated difunctional monomers to obtain frameworks (FMFs) with a controlled amount of regularly spaced reorientable C-F dipoles. The isosteric heat of adsorption of CO2 was increased by 53% by even moderate C-F dipole insertion, with respect to the non-fluorinated frameworks. CO2/N2 selectivity was also increased up to a value of 50 for the difluoro-containing comonomer. Moreover, methane shows optimal interaction energies of 24 kJ mol-1.

Porous dipeptide crystals as volatile-drug vessels.

Porous crystalline dipeptides absorb, reversibly from the gas phase, a series of volatile fluorinated ethers in use as anesthetics. Their vapor pressure was considerably reduced, with favorable guest capture and release. Variable channel sizes were customized for selective sorption and pressure thresholds were observed in the narrowest pores. 1H, 13C and 19F MAS NMR coupled with ab initio conformational analysis and grand canonical Monte Carlo simulations highlight the guest loading and arrangement adopted in the congruent nanochannels, suggesting how the anesthetics can accommodate in biochemical receptors.

Variations of the cerebral arterial circle: morphological and clinical analysis / Variaciones del círculo arterial cerebral: análisis morfológico y clínico

SUMMARY: The variations knowledge of the cerebral arterial circle (CAC) is relevant due to its influence on the development of ischemic encephalic disorders. Among these variations, when the external diameter of the posterior communicating artery exceeds the posterior cerebral artery caliber, we have a fetal conformation of this circle. The aim of this study was to describe the variations of the CAC in Chilean individuals and to know the type of arterial conformation. Thirty adult brains were used to measure lengths and caliber of the pre-communicating segments of the anterior (A1) and posterior (P1) cerebral arteries, and the anterior (ACoA) and posterior (PCoA) communicating arteries. The arterial conformation type was established, and the length and caliber of these vessels were compared according to the right or left side. It was observed that 76.6 % of the CACs presented aplasia and / or hypoplasia. Of its components, PCoA was hypoplasic in 53.3 %, appearing bilaterally in 40 % of the subjects. The comparison according to the side, indicated that the mean length of A1 and PCoA on the right side was slightly higher. In the case of caliber, the mean of A1, P1 and PCoA was higher on the left side. Regarding P1 and PcoA caliber, 33 % of the CACs presented unilateral fetal conformation. Regardless of the variability presented by the CAC, there is consensus that PCoA exhibits the greatest variability. The understanding of this variability requires an analysis of the embryonic aspects that can explain the fetal conformation of the CAC in the adult.

RESUMEN: El conocimiento de las variaciones del círculo arterial cerebral (CAC) resultan relevantes por su influencia en el desarrollo de trastornos isquémicos encefálicos. De estas variaciones, los cambios del calibre de la arteria comunicante posterior (ACoP) determinan una conformación fetal de este círculo. El objetivo de este estudio fue describir las variaciones del CAC en individuos chilenos y conocer el tipo de conformación arterial. Se utilizaron 30 encéfalos adultos a los que se midieron las longitudes y calibres de los segmentos precomunicante de las arterias cerebrales anteriores (A1) y posteriores (P1), y de las arterias comunicante anterior (ACoA) y ACoP. Se estableció el tipo de conformación arterial y se comparó la longitud y calibre de estos vasos según lateralidad. Se observó que el 76,6 % de los CAC presentaron agenesias y/o hipoplasias. De sus componentes, la ACoP fue hipoplásica en el 53,3 %, presentándose bilateral en el 40 %. La comparación según lateralidad indicó que la longitud media de A1 y ACoP del lado derecho fueron levemente superiores. En el caso de los calibres, la media de A1, P1 y ACoP fue superior en el lado izquierdo. Respecto de los calibres de P1 y ACoP, el 33 % de los CAC presentaron conformación fetal unilateral. Independientemente de la variabilidad que presenta el CAC, existe consenso de que la ACoP exhibe la mayor variabilidad. La comprensión de esta variabilidad requiere un análisis de los aspectos embrionarios que pueden explicar la conformación fetal de esté círculo arterial en el adulto.

CO2 regulates molecular rotor dynamics in porous materials.

A crystalline hydrogen-bonded framework with permanent porosity, built by rod-like struts and engineered to bear ultra-fast molecular rotors between two triple bonds, offers the possibility of controlling the rotational rates upon CO2 adsorption. CO2 enters the pores from the gas phase and reduces the rotational rates from the extremely fast regime of 107 Hz at 216 K to 105 Hz. The CO2-rotor interaction was evident from the 2H NMR response to the dynamics of the rotors in contact with CO2 in the crystal structure.

The HIV-1 repeated sequence R as a robust hot-spot for copy-choice recombination.

Template switching during reverse transcription is crucial for retroviral replication. While strand transfer on the terminal repeated sequence R is essential to achieve reverse transcription, template switching from internal regions of the genome (copy choice) leads to genetic recombination. We have developed an experimental system to study copy-choice recombination in vitro along the HIV-1 genome. We identify here several genomic regions, including the R sequence, where copy choice occurred at high rates. The frequency of copy choice occurring in a given region of template was strongly influenced by the surrounding sequences, an observation that suggests a pivotal role of the folding of template RNA in the process. The sequence R, instead, constituted an exception to this rule since it was a strong hot-spot for copy choice in the different sequence contexts tested. We suggest therefore that the structure of this region has been optimised during viral evolution to ensure efficient template switching independently from the sequences that might surround it.

[The mechanisms of recombination in human immunodeficiency virus]. / Caractéristiques mécanistiques de la recombinaison chez le virus de l'immunodéficience humaine.

The importance of recombination in retroviral evolution has been acknowledged for several decades. After the identification of HIV as the etiological agent of AIDS, it was suspected that recombination could also play a central role in the evolution of this virus. However, only recently extensive epidemiological studies of HIV infections worldwide have provided an estimate for the occurrence of recombination in vivo, unveiling recombination frequencies that dwarf those initially expected. Nowadays, recombination is regarded as an integral part of the infectious cycle of this retrovirus, demonstrating its major role in HIV evolution. Retroviral recombination can occur when two genetically divergent genomic RNA molecules are present in the same viral particle, and arises during reverse transcription. Here we focuse on the mechanisms that have been proposed to account for the occurrence of recombination in retroviruses, from the strand displacement model, according to which recombination occurs during second DNA strand synthesis; to the description of the factors responsible for copy-choice recombination during first DNA strand synthesis, such as the presence of breaks, pause sites, or secondary structures in the genomic RNA. Most of these models have been supported by experimental data obtained from in vitro reconstituted systems or from cell infection studies using academic model sequences. The situation in vivo must be more complex, since several factors come into play when recombination involves relatively distant isolates, as in the case of inter-subtype recombination. At present, it is clear that further studies are needed in order to evaluate whether a prevailing mechanism exists for in vivo recombination, and will also be essential for understanding how the underlying mechanisms of recombination contribute to the evolution of HIV.

Differential expression and stability of poly(ADP-ribose)polymerase mRNA in human cells.

The regulation of the expression of the poly(ADP-ribose)polymerase gene was studied in HeLa cells and in quiescent and mitogen-stimulated human lymphocytes by quantitating the mRNA molecules with a new technique based on the polymerase chain reaction. Using plasmid constructs containing defined sequences of the poly(ADP-ribose)polymerase cDNA as internal standards in a competitive PCR reaction, precise measurements of reverse transcribed mRNA copies per microgram of total RNA were obtained. The value found for asynchronously growing HeLa cells (8.6 x 10(5) copies) was very close to that observed for proliferating lymphocytes (8.7 x 10(5)) whereas a 20-fold lower value (0.4 x 10(5)) was obtained for quiescent lymphocytes. The determination of the stability of the mRNA of the enzyme in G0 and stimulated lymphocytes, and in HeLa cells was performed by devising a new PCR amplification system, using non-competitive conditions and plasmid target sequences as internal standards. The half-life of mRNA for poly(ADP-ribose)polymerase was approx. 1 h in G0 lymphocytes and 4-5 h in stimulated lymphocytes and in HeLa cells. This observed difference in stability of the transcripts can partially account for the observed difference in mRNA levels between G0 and stimulated human lymphocytes.

Recombination during reverse transcription: an evaluation of the role of the nucleocapsid protein.

The human immuno deficiency virus type 1 nucleocapsid protein 7 (HIV-1 NCp7) is a major component of the reverse transcription complex. Its effect on reverse transcription and homologous recombination has been studied in vitro under strictly identical experimental conditions. For high enzyme concentrations, NCp7 did not stimulate DNA synthesis. The time-course for completion of reverse transcription as well as the processivity and the pattern of pausing were similar in the presence or absence of NCp7. However, the addition of NCp7 significantly affected the yield of the reaction, a decrease exacerbated as the length of the copied RNA increased. We attribute this phenomenon to a destabilization of the RNA/DNA duplex at intermediate stages of reverse transcription.In contrast, NCp7 enhanced homologous recombination during synthesis mediated by HIV-1 RT (reverse transcriptase), as it did for Moloney murine leukemia virus RT. On naked RNA the process of recombination was dependent on the concentration of RT, suggesting that binding of RT to an intermediate of strand transfer was the limiting step. This dependence was relieved in the presence of NCp7. This effect does not imply a direct interaction between RT and NCp7, since similar results were obtained when NCp7 was substituted by the bacterial RNA chaperon StpA. The dominant effect of NCp7 is therefore most probably exerted at the level of condensation of the RNA templates, leading to the formation of productive interactions between the nascent DNA and the acceptor template.

Direct detection of HIV-1 RNA in epidermal Langerhans cells of HIV-infected patients.

Human Langerhans cells (LC) are bone marrow-derived, HLA-DR+, CD1a+, and CD4+ dendritic antigen-presenting cells found in stratified squamous epithelia. As other members of the dendritic leukocyte family, to which they belong, LC have been reported as targets for HIV-1 infection. The aim of the present study was to investigate whether HIV-1 RNA is expressed in epidermal LC of HIV-1-infected patients. Bulk epidermal cell (EC) suspensions were prepared from skin of nine recently deceased AIDS patients and 11 seronegative controls. Purified LC (94 +/- 4% HLA-DR+ cells with no CD3+ cells, as assessed by flow microfluorimetry analysis) and LC-depleted EC were obtained by immunomagnetic separation using an anti-CD1a monoclonal antibody. Samples were analyzed for the presence of HIV-1 RNA by reverse transcription of a spliced mRNA region of the tat gene, followed by polymerase chain reaction amplification. HIV-1-spliced RNA was detected in LC from 6 of 9 patients examined, whereas LC-depleted EC fractions from the same patients were all negative. The results indicate that epidermal LC from HIV-seropositive patients actively transcribe HIV-1 proviral DNA, further supporting the hypothesis that HIV productively infected LC could serve as a reservoir of the virus in the epidermis and as a source for the infection of T lymphocytes.

Dispersion of ventricular repolarization in the long QT syndrome.

To identify markers of dispersion of the ventricular repolarization in the idiopathic long QT syndrome, body surface potential maps were analyzed in 40 such patients (mean age +/- standard deviation 21 +/- 11 years) and in 30 healthy control subjects (mean age 24 +/- 7 years). In each subject, 117 chest leads were recorded and maps of the integral values of the QRST interval were calculated. A multipolar distribution of the values, a marker of gross electrical inequalities of repolarization, was found only in 4 patients. To detect minor regional disparities of ventricular recovery, all the ST-T waveforms were analyzed in each subject. The ST-T waves were represented by a discrete series of potential values. The "similarity index" was computed by applying a principal component analysis, which represents (in percent) to what extent 1 fundamental pattern of ST-T reproduces all the recorded waveforms. The mean value of the similarity index was significantly lower in patients with long QT syndrome than in control subjects (49 +/- 10 vs 77 +/- 8%, p less than 0.0001). A value less than 61% (corresponding to 2 standard deviations below the mean value for controls) was found in 35 of 40 patients and in only 1 control subject (sensitivity 87%, specificity 96%). Thus, the similarity index is a more sensitive marker than the multipolar distribution of QRST integral maps in revealing electrical disparities of the ventricular recovery times.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoantibodies to poly(ADP-ribose)polymerase in autoimmune diseases.

Antibodies to various nuclear proteins are frequently found in sera of patients affected by connective tissue diseases and other autoimmune diseases. We investigated the specificity of circulating autoantibodies to poly(ADP-ribose)polymerase (pADPRP) in different autoimmune and connective tissue diseases: Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA), Progressive Systemic Sclerosis (PSS), Sjogren's Syndrome (SS), Undifferentiated Connective Tissue Disease (UCTD), Cryptogenic Fibrosing Alveolitis (CFA) and Sarcoidosis. pADPRP was purified from calf thymus. Antibody specificity was detected by ELISA, western blot and enzyme activity precipitation. Positive values (mean O.D. values + 3 S.D. of 36 normal controls) were obtained in 7/15 SLE patients, 1/18 RA patients, 1/30 PSS, 3/14 SS, 0/5 UCTD, 5/21 CFA and 4/25 Sarcoidosis. The positive sera also recognized the pADPRP protein when tested by western blot. Furthermore the enzyme activity was inhibited after immunoprecipitation by some highly positive sera.

Autoxidation in xylose/lysine model systems.

The volatiles produced in xylose/lysine model systems added with an antioxidant (alpha-tocopherol, 2,6-di-tert-butyl-4-methylphenol, or rosemary extract) or a free radical initiator (alpha, alpha'-azobis(isobutyronitrile), AIBN) were analyzed to investigate the effects of the presence of free radicals on the Maillard reaction. The pH was maintained constant at 4 or 6, by adding a base, and the data were compared by principal component analysis (PCA). The additives were more effective at pH 4 than pH 6. At pH 4, the model system added with AIBN is very well-discriminated by PCA from the models with the antioxidants and the reference model system, indicating that the volatiles are sensitive to compounds that can interfere in an opposite way with free radical formation.

Effects of olive, canola, and sunflower oils on the formation of volatiles from the Maillard reaction of lysine with xylose and glucose.

Some important edible oils (extra virgin olive oil, canola oil, and sunflower oil) were added to aqueous glucose-lysine or xylose-lysine model systems to investigate their effect on the formation of volatiles from the Maillard reaction (MR). The volatile compounds were extracted by a Likens-Nickerson apparatus and quantified. Pyrazines, Maillard reaction products with an important impact on food flavor, appeared to be particularly sensitive to the presence of the oils in both the xylose-lysine and glucose-lysine model systems. The unsubstituted pyrazine was formed more with olive oil, less with canola oil, and even less with sunflower oil, whereas 2-methylpyrazine, 2,5-methylpyrazine, and 2,3-dimethylpyrazine were formed less with olive oil, more with canola oil, and even more with sunflower. The oxidative states of the oils and their fatty acid fingerprints were determined: the results indicated that the relative amounts of the pyrazines are sensitive to the degree of unsaturation of the oil. The autoxidation of the volatile compounds generated from the MR, investigated by the addition of free radical modulators (antioxidants alpha-tocopherol, 2,6-di-tert-butyl-4-methylphenol, and rosemary extract; or pro-oxidant alpha,alpha'-azobis-isobutyronitrile, a free radical initiator), was limited in respect to aqueous model systems.

[Oral glucose tolerance and HbA1c in the diagnosis of pregnancy in diabetes]. / Carico orale di glucosio ed HbA1c nella diagnosi di diabete gestazionle.

This study was undertaken in order to evaluate the plasma glucose response to oral glucose tolerance test (OGTT, 100 g) and the HbA1c values in pregnant women at different gestational ages. One-hundred twenty-nine OGTTs have been performed in 75 pregnancies. The results obtained show a decrease in glucose tolerance during pregnancy. Mean HbA1c value was significantly higher in women with gestational diabetes mellitus, but values of subjects with gestational diabetes and normal glucose tolerance overlapped widely. In conclusion, HbA1c is not a sensitive parameter in the diagnosis of gestational diabetes mellitus. Further studies are necessary to evaluate its specificity and prognostic significance.

Oral microbiota and implant type membranes.

Candida albicans (Ca), Staphylococcus aureus (Sa), Streptococcus sanguis (Ss), Actinomyces naeslundii (An), Actinomyces odontolyticus (Ao), Porphyromona spp (P spp), Candida glabrata (Cg), Candida krusei (Ck), and Rhodotorula spp (R spp) were tested with equal pieces of biodegradable membranes. Membranes pretreated with saliva or clorhexidine and nontreated control membranes were tested in three different culture media containing 0.1 mL homologous suspension for each strain under study. Incubation was performed at 37 degrees C for 48 hours for aerobiosis and for five days for anaerobiosis. Macroscopy and microscopy were carried out. Membranes were removed, washed, and resuspended. Samples were sonicated, and the supernatant was disseminated on brain heart infusion broth or blood agar. Incubation was repeated, colony-forming unit counts were performed, and statistical analysis was carried out using analysis of variance transforming results to Log10 (x + 1), the highest interaction level was used to calculate standard error. Orthogonal contrast was used to compare the different microorganisms under study. Highest adhesion was found with Ca, Cg, Ck, Sa, and Ss. A sufficient quantity of Actinomyces could not be recovered from the membranes. Results with P spp were poor, confirming lower gram-negative adhesion. Replicate flasks with Ss and Ca were cultivated. Membranes were removed after washing and subjected to scanning electron microscopy, as were untreated control pieces. A cavelike surface was observed. Streptococcus sanguis adhering to the membranes showed extracellular projections. Candida and gram-positive cocci showed great recovery capacity.

[Candida carriage in the oral mucosa of a student population: adhesiveness of the strains and predisposing factors]. / Portación de Candida en mucosa oral de una población estudiantil: adherencia de las cepas y factores predisponentes.

The aim of this study was to establish oral carriage of Candida and possible factors associated to their virulence in young adults and their relation with local and general situations considered as predisposing factors. Samples were obtained from dorsum tongue in 70 students attending the Faculty of Dentistry (University of Buenos Aires) average age: 23, all in healthy oral conditions. Of these, 21.42% were Candida positive. These samples were seeded in CHROMagar. Candida identification was completed in milk agar and Fungichrom 1. The following species were identified: 11 Candida albicans (C.a), 2 Candida parapsilosis (C.p) and 1 Candida glabrata (C.g). In one case, 2 species (C.a and C.g) were isolated in the same sample. Virulence was determined as adherence capacity by biofilm or in vitro plaque formation and hydrophobicity. Different host factors were analyzed statistically to establish their importance as predisposing factors to allow Candida colonization. Adherence of C.a. was found to be similar in all C.a. strains, whereas significant differences were found between C.a. and C.p. and between C.a. and C.g. Only the antiseptic mouthrinse and the diet were significant among the considered factors.

[Comparative study of the Candida albicans genotypes isolated from immunocompromised patients and health carriers]. / Estudio comparativo de los genotipos de Candida albicans aislados de pacientes inmunocomprometidos y portadores sanos.

The aim of this study is to compare Candida albicans strain genotype isolates from oral cavity of immunocompromised patients due to different immunologic impairments with apparently normal carriers. Four populations were studied: 1) HIV positive hospitalized patients, 2) HIV negative immunocompromised patients (leukemia, lymphoma, organ transplant recipients), 3) drug addicts prior to AIDS pandemia in Argentina, 4) apparently normal carriers. DNA extracted was digested with the enzyme Eco RI, electrophoresed, transferred to nitrocellulose membrane and hybridized with the 27A probe labelled with 32P. The comparison between the profiles obtained permitted the differentiation of 16 genotypes. The distribution of the strains led to the conclusion that: a) all the isolated strains from AIDS patients were closely related and distributed in only three genotypes (1, 3, 11); b) a major genetic relationship between the isolates from AIDS patients and HIV negative immunocompromised patients was observed; c) strains from carriers showed a minor genetic similarity with those obtained from AIDS patients; d) characteristic profiles belonging to any of the studied groups were not found; e) significant genomic changes have not been observed during the last twenty years.

Antimicrobial power of composite resin adhesion systems.

The adherence of microorganisms to dentin that had been contaminated and then treated with conditioning substances was evaluated. The germicide effect of those products and their possible substantivity was also evaluated. Dentin slices were contaminated with Candida albicans, Streptococcus mutans and Actinomyces naeslundii and then treated with the following substances: 1. Experimental Blue Solution A, 2. Experimental Red Solution B; 3 Tubulicid Blue Label; 4. Tubulicid Red Label; 5 Scotchprep Dentin Primer; 6 ventura Dentin Bond Cleaner; 7 ventura Dentin Bond Primer, 8. Gluma dentin Bond; 9 Tenure Conditioner; 10. All Bond Dentin Conditioner; 11 Syntac Primer; 12. Clearfil New Bond acid + adhesive; 13 Prisma Universal Bond 3 Primer; 14. Denthesive Cleaner; 15. Control (Distilled water). Adherence was evaluated using scanning electron microscopy and viability tests were performed. Substances 1, 2, 3, 4, 5, 7, 8, and 11 impair adherence; the control and substances 6 and 9 produced no afforded intermediate results effect while substances 10, 12, 13 and 14. Viability tests afforded results similar to those obtained for adherence. Several substances that are used for dentin treatment or for dentin priming for adhesion could be useful in preventing microorganism viability and so contribute to the protection of pulp vitality.

Bacterial inhibition produced by substances for dentin pretreatment.

Dentin treatment before adhesion of composites is performed both to enhance adhesion and to remove the microbial contents of the smear layer. The purpose of these experiments was to evaluate the germicide potential of several dentin treatments used in adhesive systems and of some cleansing solutions. Different germs involved in caries processes were used (Candida Albicans, Streptococcus mutans and Actinomyces naeslundii) to prepare suspensions. Half a milliliter of each of the suspensions was transferred to test tubes and an equal volume of the following substances was added: Scotch Prep Dentin Primer (P), Gluma Cleanser (G), Cleaner Sol. (C), Tubulicid Blue (TB) and Red Label (TR), Blue Experimental Solution (SB) and Red Experimental Solution (SR) and sterile distilled water (control). The preparation was incubated at 37 degrees C for seven days to test viability. P, TR, TB and SB produced complete inhibition of germs tested. The results reveal that, "in vitro", not all the substances tested exert a germicide effect on the microorganisms analyzed.

Germicide effect of several glass ionomer cements.

One the most significant characteristics of glass ionomer cements is their ability to release fluoride compounds. This study was carried out to try establish relationships between this property and the possible effect on the growth of microorganisms that are found in carious lesions, Agar BHI medium containing Petri dishes were flooded with strains of Actinomyces naeslundii, Actinomyces israelii and Actinomyces odontolyticus. Cavities were then prepared in the agar and filled with mixtures of several glass ionomer cements. Some of them were polymerizable resin containing products. A zinc phosphate and a zinc oxide-eugenol cement were used as controls. After a seven day incubation at 37 degrees C under anaerobic conditions the inhibition halos around the specimens were measured in a way similar to that used for antibiograms. The statistical analysis of the results showed no significant differences among Actinomyces strains but a significant difference one among cements. Even when no definitive conclusions could be drawn it is worth taking into consideration the effect of glass ionomer cements on microorganisms such as the Actinomyces and continuing studies to establish more clearly what is required from the material to produce a clinically significant outcome.