Hydrogen physisorption on the (BeO)n, B2H4(Be,Ti), and B6Ti3 metal clusters: a computational study of energies and atomic charges.

The equilibrium structures of BeO clusters and Be,Ti-decorated boranes were computed with the ωB97X-D method and the 6-31G + (2d,2p) and aug-cc-pVTZ basis sets to study their intermolecular interactions with hydrogen molecules. Thermochemical and molecular properties such as the harmonic vibrational frequency, dipole and quadrupole moments, and atomic charges are employed to understand the attractive interactions that control the adsorption process. Comparison of molecular properties and atomic charges of the studied compounds before and after H2 molecule adsorption shows that most of the interactions among the BeO clusters and boranes with H2 molecules constitute a combination of dispersion, electrostatic, and weak charge transfer interactions. Calculated values of Hirschfeld atomic charges and ΔEe (in parenthesis) (BeO)4.8H2 (0.028 e and -2.0 kcal.mol-1), (BeO)2.12H2 (0.030 e and -2.8 kcal.mol-1), B6Ti3.10H2 (0.045 e and -15.4 kcal.mol-1), and B6Ti3+.10H2 (0.058 e and -15.3 kcal.mol-1) show qualitative correlation between hydrogen atomic charges and electronic energy of hydrogen interaction. The ωB97X-D/6-31 + G(2d,2p) values of Gibbs free energy at 298.15 K for (BeO)4.8H2 B2H4Ti.4H2 and B6Ti3.10H2 clusters are equal to -5.0, -4.9, and -5.1 kcal.mol-1, respectively, which are within the range of energy parameters of materials that could be employed in hydrogen storage tanks for light vehicles.

Effects of multidimensional tunneling in the kinetics of hydrogen abstraction reactions of O (3 P) with CH3 OCHO.

Quantum tunneling paths are important in reactions when there is a significant component of hydrogenic motion along the potential energy surface. In this study, variational transition state with multidimensional tunneling corrections are employed in the calculations of the thermal rate constants for hydrogen abstraction from the cis-CH3 OCHO by O (3 P) giving CH3 OCO + OH (R1) and CH2 OCHO + OH (R2). The structures and electronic energies are computed with the M06-2X method. Benchmark calculations with the CBSD-T approach give an enthalpy of reaction at 0 K for R1 (-2.8 kcal/mol) and R2 (-2.5 kcal/mol) which are in good agreement with the experiment, i.e. -2.61 and -1.81 kcal/mol. At the low and intermediate values of temperatures, small- and large-curvature tunneling dominate the kinetics of R1, which is the dominant path over the range of temperature from 250 to 1200 K. This study shows the importance of multidimensional tunneling corrections for both R1 and R2, for which the total rate constant at 298 K calculated with the CVT/µOMT method is 8.2 × 10-15 cm3 molecule-1 s-1 which agrees well with experiment value of 9.3 × 10-15 cm3 molecule-1 s-1 (Mori, Bull. Inst. Chem. Res. 1981, 59, 116). © 2018 Wiley Periodicals, Inc.

Arterial and interstitial remodelling processes in non-specific interstitial pneumonia: systemic sclerosis versus idiopathic.

AIMS: To compare septal and vascular matrix remodelling, vascular occlusion, pulmonary function tests and survival between two groups: one with idiopathic non-specific interstitial pneumonia (NSIP) and one with NSIP associated with systemic sclerosis (SSc). METHODS AND RESULTS: Pulmonary biopsy specimens were examined from 40 patients, 22 with NSIP and 18 with NSIP associated with SSc. The content of septal collagen and elastic fibres, as well as the elastic fibres in the vascular interstitium, were higher in the SSc group (P = 0.01, P = 0.001 and P < 0.0001, respectively). Among pulmonary function tests, the diffusing capacity for carbon monoxide/alveolar volume was affected to a greater extent in the SSc group (59% of the predicted value in SSc and 97% in the idiopathic group). There were no differences in collagen content of the vascular interstitium, arterial occlusion, or survival between the two groups. CONCLUSIONS: Although the fibrotic process is more intense in the SSc group, it does not affect the prognosis of these patients. Because the elastotic process is higher in the SSc group, this might suggest that autoimmune inflammatory mechanisms affecting the elastic fibre system play a greater role in the pathogenesis and pulmonary remodelling process of SSc NSIP than in idiopathic NSIP.

[Discourses and practices concerning the social participation process in health education activities: community mobilization in the PCDEN/PE. Programa de Controle das Doenças Endêmicas do Nordeste/Pernambuco]. / Discursos e práticas referentes ao processo de participação comunitária nas ações de educação em saúde: as ações de mobilização communitária do PCDEN/PE.

This study analyzes and compares several social participation concepts in health education processes to practical experiences with schistosomiasis prevention measures under the Northeast Endemic Disease Control Program (Brazilian Ministry of Health/World Bank, 1987). Using qualitative methods, institutional documents and discourses were interpreted (Sucam, FNS, and Ministry of Health). A field study was also performed (using interviews with community-based health agents and the general population) in the Zona da Mata region of Pernambuco (a historically endemic area for schistosomiasis), focused in the county of Amaraji. Comparing discourses and educational practices, we found factors that explain respective points of convergence and divergence, as well as elements linked to the social and historical process of the target population which systematically limit the efficacy of such educational measures.

Physiological aspects of Trypanosoma cruzi gene regulation during heat-shock.

Investigations on the conditions of heat-shock response in Trypanosoma cruzi, the agent of Chagas disease, showed that at 37 degrees C, one of the heat-shock temperatures employed, the parasites from 48 h culture do not display a classical response to the heat treatment, since a general increase in RNA and protein synthesis was detected. The classical heat-shock response was detected only at 40 degrees C. The data also suggest that the heat shock proteins (HSP) mRNA population is sufficient to maintain protein synthesis at a high rate for at least 1 h and, to maintain the same rate of response for a longer period, transcription is necessary. The half life of HSP 70 mRNA is less than 3 h at 37 degrees C. The protein synthesized during the first hour of the heat shock at 37 degrees C is stable for at least 24 h. The parasite seems to be able to reuse the stock of HSP mRNAs stored during the first thermal shock to respond to a second heat treatment. These data are discussed bearing in mind other cell types.

Protein antigens of Mycobacterium leprae.

Protein antigens of Mycobacterium leprae have been identified by screening the lambda gt11, pYA626 and pHC79::M. leprae genomic libraries with pooled sera from leprosy patients and with antiserum to M. leprae cell wall protein (CWP) aggregate. Immunological screening of the lambda gt11 library with pooled sera from 21 lepromatous (LL) leprosy patients resulted in the identification of 19 antigens that are apparently different from previously identified M. leprae antigens. Five additional antigens were identified by screening the lambda gt11 library with pooled sera from 30 borderline tuberculoid or tuberculoid patients. Four other antigens were identified by screening the lambda gt11 library with anti-CWP. Two groups of recombinant cosmids were identified by screening the pHC79 library with LL patients' sera: one group specified proteins that reacted with monoclonal antibodies (mAb) against the 65-kDa protein and against the 18-kDa protein; the other group specified a 15-kDa protein that did not react with any of the mAb that were tested. One pYA626 clone also specified a 15-kDa protein that reacted with LL patients' sera, but did not react with any mAb. Genes specifying several of these antigens have been subcloned into the Asd+ plasmid vector pYA292 and have been introduced into a delta cya delta crp delta asd Salmonella typhimurium strain to evaluate the ability of individual M. leprae proteins to elicit immune responses against M. leprae infection.

HSP 70 gene expression in Trypanosoma cruzi is regulated at different levels.

The level of HSP 70 mRNA is altered in Trypanosoma cruzi cells incubated at supra-optimal temperatures: the total amount of this RNA per cell is increased at 37 degrees C, and slightly decreased at 40 degrees C relative to its level at 29 degrees C. However, its amount is greater in the polysomes at either temperature. The relative increase of this RNA is larger in the polysomes fraction than it is in the total RNA. In addition the level of HSP 70 protein in heat-shocked cells is greater than would be expected from the recruitment of HSP 70 mRNA in the polysomal fraction. Taken together the data are interpreted as indicating that at 37 degrees C and 40 degrees C the HSP 70 gene regulation in T. cruzi involves both the selective accumulation of the HSP 70 mRNA in the polysomes and its preferential translation. At 37 degrees C, in addition, an increase in the total amount of this template is observed in the cells.

Alpha- and beta-tubulin mRNAs of Trypanosoma cruzi originate from a single multicistronic transcript.

The cluster of alternated alpha- and beta-tubulin genes in the genome of Trypanosoma cruzi was shown to be transcribed into a single RNA molecule which upon processing gives rise to the mature alpha- and beta-tubulin mRNAs. This conclusion was based on: (i) nuclear RNA species with the same molecular mass hybridize to both alpha- and beta-tubulin cDNA probes; (ii) S1 nuclease assay of the clustered tubulin genes has shown protected DNA fragments of the same size and of greater molecular mass than that corresponding to the mRNAs, hybridizable to both alpha- and beta-tubulin cDNA probes; (iii) beta-tubulin hybrid selected RNA is still able to hybridize to alpha-tubulin probe.

Trypanosoma cruzi: an in vitro cycle of cell differentiation in axenic culture.

The operation of an in vitro cycle of cell differentiation of Trypanosoma cruzi in axenic culture was obtained. When epimastigote forms, grown in LIT medium, were transferred to a modified LIT medium (E. Chiari, 1981, "Diferenciação do Trypanosoma cruzi em cultura." Ph.D. dissertation, Universidade Federal de Minas Gerais, Brazil), metacyclic trypomastigotes were generated. The latter, upon treatment with fresh human serum, and subsequent incubation in LIT medium gave origin to clusters of spheromastigote cells. The spheromastigotes were resistent to lysis mediated by the complement system and possess a morphology shown by optical and electron microscopy to be very similar to spheromastigotes derived from tissues of infected vertebrates. Blood-like trypomastigotes, or epimastigotes, could be obtained from spheromastigotes depending on the incubation conditions: at high serum concentration (55%) at 37 C, blood-like trypomastigotes were generated; by aging or heating (37 C), at low serum concentration (10%), epimastigotes were formed, closing the whole sequence of cell differentiation of T. cruzi. The molecular characterization of the different cell forms by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of metabolic pulse labeled proteins showed that the in vitro differentiated cells were distinct, not only by morphological criteria, but by differential gene expression as well. All the forms described could be obtained in large amounts (6 x 10(7) to 1 x 10(8)/ml), making it possible to perform preparative biochemical, molecular biological, and immunological experiments.

Protein biosynthesis changes in Trypanosoma cruzi induced by supra-optimal temperature.

Early during vertebrate infection, T. cruzi is exposed to the host blood at an elevated temperature. Bearing this in mind, the pattern of protein synthesis of two parasite forms was examined. SDS-PAGE of heated organisms showed an increase in at least four proteins (103, 92, 75 and 61 kD). The temperature effect is also manifested in cells whose RNA synthesis is reduced by actinomycin D treatment. The synthesis of the '29 degrees proteins' is inhibited at 40 degrees C in organisms growing in culture medium; when the organisms were maintained in serum, the inhibition was not observed. The inhibitory effect observed at 40 degrees C was reversed when the temperature was shifted to 29 degrees C. These proteins were synthesized for 180 min at 37 degrees C or 360 min at 40 degrees C. The increased protein synthesis manifested at 37 degrees C had decreased 45 min after the temperature was lowered to 29 degrees C. When the cells were pre-incubated at 40 degrees C and shifted to 29 degrees C, the synthesis of the heat-induced proteins proceeded for at least 180 min. This pattern of heat induction in epimastigotes and trypomastigotes is the same irrespective of whether the incubation medium is LIT (for epimastigotes), M-16 (for trypomastigotes), or when serum was used for both cell types.

Dynamic aspects of cytoplasmic poly(A)+ RNA of Tetrahymena pyriformis.

In the present work a study was made of the compartmentalization of the poly(A)+ RNA populations during the cultural development of cells of T. pyriformis that were pre-starved or derived from stationary cultures. It was found that the poly(A)+ RNA content increases when the cells change from stationary to lag phase. The increase in RNA poly(A)+ is manifested exclusively in the polysome compartment. The level of poly(A)+ RNA in the cytoplasmic non-polysomal compartment does not change. The increase in poly(A)+ RNA is concomitant with an expansion of the polysomes. Pre-starved cells initiate polysome formation soon after being transferred to a growing medium. During this time the poly(A)+ RNA content of the non-polysomal compartment decreases and that of polysomes increases in close proportion. Not only in the starved but also in stationary cells and in those that are beginning to grow, the proportion of poly(A)+ RNA in mRNP is higher than in the polysomes. These data are interpreted as indicating that cells of T. pyriformis, derived from stationary cultures are dependent on RNA synthesis for polysome formation; on the other hand, pre-starved cells use preformed non-polysomal poly(A)+ RNA for the same purpose, in the beginning of the cultural development.