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991.
de Azevedo WF Canduri F dos Santos DM Pereira JH Bertacine Dias MV Silva RG Mendes MA Basso LA Palma MS Santos DS 《Biochemical and biophysical research communications》2003,312(3):767-772
Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. PNP is a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. More recently, the 3-D structure of human PNP has been refined to 2.3A resolution, which allowed a redefinition of the residues involved in the substrate-binding sites and provided a more reliable model for structure-based design of inhibitors. This work reports crystallographic study of the complex of Human PNP:guanine (HsPNP:Gua) solved at 2.7A resolution using synchrotron radiation. Analysis of the structural differences among the HsPNP:Gua complex, PNP apoenzyme, and HsPNP:immucillin-H provides explanation for inhibitor binding, refines the purine-binding site, and can be used for future inhibitor design. 相似文献
992.
dos Reis-Costa L Soares AM França SC Trevisan HC Roberts TJ 《Protein and peptide letters》2003,10(6):619-628
Lipases are versatile enzymes regarding the range of reactions they catalyse and substrates on which they act. They are as well important as catalyst in organic synthesis. Their immobilization on appropriate supports confer them greater stability besides the possibility of operating in continuous reactors. In order to explore these abilities, the reactions involving hydrolysis of p-nitrophenyl acetate (PNPA) and transesterification of PNPA with n-butanol were chosen. Lipases from two different sources were assayed, namely: microbial (Candida rugosa, CRL, Sigma Type VII) and pancreatic (PPL, Sigma, Type II). Two immobilization methods were also used, namely: 1). adsorption, using as support the following silica derivatives (150-300 microm e 450micro): phenyl, epoxy, amino and without derivation, and 2). covalent binding, using glutaraldehyde as binding agent and silica amino as support. This later method led to better results. Hydrolytic activity was 6.1 U/g(support) for CRL and 0.97 U/g(support) for PPL, and of transesterification, 2,8 U/g(support) for CRL and 1,9 U/g(support) for PPL. Stability of the immobilized enzyme as a function of temperature was evaluated for CRL at 40 degrees C and 50 degrees C and for PPL at 32 degrees C and 40 degrees C. The assays were initially carried out batchwise, both for soluble and immobilized enzymes, aiming to the obtention of parameters for the continuous reactor. Lipases immobilized by covalent binding were used in the assays of operational stability in continuous reactors. For PPL in aqueous medium, at 32 degrees C, and CRL in organic medium at 40 degrees C, both operating continuously, no significant loss of activity was detected along the analysis period of 17 days. In the case of CRL in aqueous medium at 40 degrees C there was a loss of activity around 40% after 18 days. For PPL in organic medium at 40 degrees C the loss was 33% after 20 days. Comparing both sources with each other, very different results were obtained. Higher activity was found for CRL, both for hydrolysis and for transesterification reactions, with higher stability in organic medium. PPL showed lower activity as well as higher stability in aqueous medium. The immobilization method by covalent binding showed to be the most appropriate. Immobilized lipases are therefore relatively stable both in aqueous and organic medium. 相似文献
993.
Da Silva CH Cunha RL Tonaco RB Cunha TM Diniz AC Domingos GG Silva JD Santos MV Antoun MG de Paula RL 《Bioethics》2003,17(5-6):417-424
The presence of truth and honesty is a permanent demand, and becomes vital the more committed and intimate a relationship is. Medical practice is relevant to this discussion when one questions whether or not a physician should always tell their patient the truth in the face of a progressive or potentially fatal disease, regarding their diagnosis, outcome, therapy and evolution of the specific disease. From this discussion we aim, with the present report, to look at the truth applicable to the patient-physician relationship, and its ethical and moral implications; and also to look at where the Brazilian Code of Medical Ethics (BCME) and the medical literature stand regarding this issue. One concludes that there are only two moments not to tell a patient the truth: when the patient does not want to be informed, and when the truth could be iatrogenic. The question now is, when would the truth be iatrogenic? Physicians, in our opinion, would not be able to judge solitarily when the truth might be deleterious to their patient. Alternatively, we proposed the appointment of a multidisciplinary commission to help the doctor with such a decision. 相似文献
994.
Kawakami Y Rodríguez-León J Koth CM Büscher D Itoh T Raya A Ng JK Esteban CR Takahashi S Henrique D Schwarz MF Asahara H Izpisúa Belmonte JC 《Nature cell biology》2003,5(6):513-519
The mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and phosphatidylinositol-3-OH kinase (PI3K)/Akt pathways are involved in the regulatory mechanisms of several cellular processes including proliferation, differentiation and apoptosis. Here we show that during chick, mouse and zebrafish limb/fin development, a known MAPK/ERK regulator, Mkp3, is induced in the mesenchyme by fibroblast growth factor 8 (FGF8) signalling, through the PI3K/Akt pathway. This correlates with a high level of phosphorylated ERK in the apical ectodermal ridge (AER), where Mkp3 expression is excluded. Conversely, phosphorylated Akt is detected only in the mesenchyme. Constitutively active Mek1, as well as the downregulation of Mkp3 by small interfering RNA (siRNA), induced apoptosis in the mesenchyme. This suggests that MKP3 has a key role in mediating the proliferative, anti-apoptotic signalling of AER-derived FGF8. 相似文献
995.
996.
Gomez S Mateus AC Hernandez J Zimmermann BH 《Biochemical and biophysical research communications》2000,279(2):653-656
The Andean potato weevil, Premnotrypes vorax, an insect of the order Coleoptera, is a major cause of damage to potato crops in the Andean regions of South America. The insecticidal Cry proteins from Bacillus thuringiensis are useful biological pesticides, and some are toxic to Coleopteran insects. We overexpressed recombinant, histidine-tagged Cry3Aa protein in Escherichia coli host cells. The recombinant protein was solubilized at high pH with urea, purified using Ni(2+)-nitrilo-triacetic acid affinity resin, and dialysed to lower pH and remove urea. Bioassays were performed with an insect media whose surface was spread with 70 microgram/mL purified native or recombinant toxins. First instar larvae exposed to toxin treated media for 5 days exhibited mortalities from 57% (native Cry3Aa) to 52% (recombinant Cry3Aa). Purified native and recombinant Cry3Aa proteins appeared to be equally toxic to the Andean potato weevil. 相似文献
997.
In the health care setting, drugs added to large volume parenteral solutions (LVPS) are routinely administered to improve therapeutic effects and provide a faster clinical response. The development of analytical techniques that permit the detection of incompatibilities between drugs and parenteral solutions is necessary to guarantee their correct association with minimum adverse effects. Green fluorescent protein (GFP) has been used as a biological indicator of sterilization and disinfection processes because it exhibits a high thermal stability and is easily detected using UV light and spectrofluorometry. The response of GFP structure and/or protonation state to physicochemical changes in the solution favors its potential use as a biosensor for drug stability in parenteral solutions. The stability of the diuretic drugs furosemide and aminophylline, individually or combined, added to parenteral solutions of 20% mannitol and 0.9% NaCl was monitored by absorbance and RP-HPLC immediately and after 20 h of storage at room temperature, with and without 1 h exposure to a strong oxidant, H2O2. Changes in GFP fluorescence intensity were evaluated under the same conditions for purified GFP added to aliquots of the drug/LVPS solutions. Results show that GFP fluorescence intensity was proportional to the loss in drug stability over time and thus may potentially be added to a lot sample of a drug/parenteral solution as an immediate on-site test for defective product. 相似文献
998.
Testing theories of dispersal is challenging in highly migratory species. In sea turtles, population size, geographic distance, natal homing, and ocean currents are hypothesized to affect dispersal. Little is known, however, about these mechanisms in sea turtles foraging along the South American coast. Green sea turtles feeding at Ubatuba (UB, n = 114) and Almofala (AF, n = 117), Brazil, were sequenced at the mitochondrial DNA (mtDNA) control region (486 bp) and genotyped at 7 microsatellite loci to test dispersal hypotheses. Fifteen mtDNA haplotypes were revealed, including a previously undescribed sequence, and the average observed heterozygosity (H(o)) was 76.4%. Overall short-term temporal differences were not detected, and differentiation was less pronounced in microsatellite than in mtDNA analyses. Mitochondrial results reveal significant differentiation between the Brazilian feeding grounds and most other Atlantic groups, whereas microsatellites uncover similarities to some of the geographically closest populations. Ubatuba and Almofala are mixed stocks, drawn primarily from Ascension, with lesser contributions from Surinam/Aves and Trindade. Costa Rica is also a significant source of individuals feeding at AF. The results are consistent with a model of juvenile natal homing impacted by other factors. Effective protection of turtles foraging along the extensive Brazilian coast may enhance breeding populations thousands of kilometers away. 相似文献
999.
This paper describes the application of a methodology designed to analyse the relationship between climatic conditions and
the perception of bioclimatic comfort. The experiment consisted of conducting simultaneous questionnaire surveys and weather
measurements during 2 sunny spring days in an open urban area in Lisbon. The results showed that under outdoor conditions,
thermal comfort can be maintained with temperatures well above the standard values defined for indoor conditions. There seems
to be a spontaneous adaptation in terms of clothing whenever the physiological equivalent temperature threshold of 31°C is
surpassed. The perception of air temperature is difficult to separate from the perception of the thermal environment and is
modified by other parameters, particularly wind. The perception of solar radiation is related to the intensity of fluxes from
various directions (i.e. falling upon both vertical and horizontal surfaces), weighted by the coefficients of incidence upon
the human body. Wind was found to be the most intensely perceived variable, usually negatively. Wind perception depends largely
on the extreme values of wind speed and wind variability. Women showed a stronger negative reaction to high wind speed than
men. The experiment proved that this methodology is well-suited to achieving the proposed objectives and that it may be applied
in other areas and in other seasons. 相似文献
1000.
Selma Kückelhaus José Roberto S. A. Leite Mateus P. Neves Karla S. Frota Lídia F. Abdala Maria Imaculada Muniz-Junqueira Carlos BlochJr Carlos Eduardo Tosta 《International journal of peptide research and therapeutics》2007,13(3):423-429
The growing resistance of microorganisms to antibiotics has been considered as a global public health problem. Therefore,
the search for novel antimicrobial drugs, chemically unrelated to the presently used antibiotics, is urgently needed. Our
group has recently characterized a new family of antimicrobial peptides – phylloseptins – isolated from the skin secretion
of the South American amphibian Phyllomedusa hypochondrialis, which showed a strong antimicrobial effect against Gram-positive and Gram-negative bacteria. We now investigate the in vivo toxicity of synthetic phylloseptin-1 (PS-1) toward bone marrow, liver, spleen, kidney and lung after endovenous administration
to Swiss mice of a bolus dose of 4 mg/kg. Genotoxicity was evaluated by quantifying erythrocyte micronuclei. PS-1-treated
mice showed no alteration in the histology of liver, spleen, kidney and lung, as well as of blood biochemistry, as compared
to normal controls. Cytotoxicity tests, evaluated either by blood cytometry or bone marrow polychromatophilic erythrocyte
index, revealed no deleterious effect of PS-1. Moreover, the peptide showed no toxicity towards bone marrow erythrocytes.
We concluded that, in a concentration ten times over that providing antimicrobial effect, synthetic PS-1 showed no in vivo toxicity. 相似文献