Showing papers by "Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto published in 1997"

Trehalases and trehalose hydrolysis in fungi

Abstract: The simultaneous presence of two different trehalose-hydrolysing activities has been recognised in several fungal species. While these enzymes, known as acid and neutral trehalases, share a strict specificity for trehalose, they are nevertheless rather different in subcellular localisation and in several biochemical and regulatory properties. The function of these apparently redundant activities in the same cell was not completely understood until recently. Biochemical and genetic studies now suggest that these enzymes may have specialised and exclusive roles in fungal cells. It is thought that neutral trehalases mobilise cytosolic trehalose, under the control of developmental programs, chemical and nutrient signals, or stress responses. On the other hand, acid trehalases appear not to mobilise cytosolic trehalose, but to act as ‘carbon scavenger’ hydrolases enabling cells to utilise exogenous trehalose as a carbon source, under the control of carbon catabolic regulatory circuits. Although much needs to be learned about the molecular identity of trehalases, it seems that in fungi at least one class of acid trehalases evolved independently from the other trehalases.

Response threshold to aversive stimuli in stimulated early protein- malnourished rats

Abstract: Two animal models of pain were used to study the effects of short-term protein malnutrition and environmental stimulation on the response threshold to aversive stimuli. Eighty male Wistar rats were used. Half of the pups were submitted to malnutrition by feeding their mothers a 6% protein diet from 0 to 21 days of age while the mothers of the other half (controls) were well nourished, receiving 16% protein. From 22 to 70 days all rats were fed commercial lab chow. Half of the animals in the malnourished and control groups were maintained under stimulating conditions, including a 3-min daily handling from 0 to 70 days and an enriched living cage after weaning. The other half was reared in a standard living cage. At 70 days, independent groups of rats were exposed to the shock threshold or to the tail-flick test. The results showed lower body and brain weights in malnourished rats when compared with controls at weaning and testing. In the shock threshold test the malnourished animals were more sensitive to electric shock and environmental stimulation increased the shock threshold. No differences due to diet or environmental stimulation were found in the tail-flick procedure. These results demonstrate that protein malnutrition imposed only during the lactation period is efficient in inducing hyperreactivity to electric shock and that environmental stimulation attenuates the differences in shock threshold produced by protein malnutrition.

A highly thermostable β-glucosidase activity from the thermophilic fungus Humicola grisea var. thermoidea: purification and biochemical characterization

Abstract: Humicola grisea var. thermoidea grown in sugar cane bagasse produced and secreted two major protein components exhibiting β-d-glycosidase activities (forms I and II). Form I was purified to apparent homogeneity (PAGE and SDS-PAGE) by a three-step procedure involving acetone precipitation, DEAE-cellulose chromatography and filtration in Bio-Gel P-100. The purified enzyme was a glycoprotein of 35% carbohydrate content and apparent molecular mass of 55 kDa (SDS-PAGE and gel filtration), Optima of temperature and pH were 50–60°C and 6.0, respectively. The enzyme activity was stable at 60°C and exhibited a half-life of 30 min at 70°C. The enzyme hydrolyzed p-nitrophenyl β-d-glucopyranoside, cellobiose, xylobiose, p-nitrophenyl β-d-xylopyranoside and CM-cellulose. Kinetic studies indicated that these substrates were hydrolyzed at the same catalytic site.

Manganese(III) porphyrins: catalytic activity and intermediate studies in homogeneous systems

Abstract: We studied how solvent, stirring method, PhIO/MnP molar ratio, presence of water and axial ligand affect the catalytic activities of Mn(TPP)Cl, Mn(MNPP)Cl, Mn(TDCPP)Cl and Mn(TFPP)Cl in the oxidation of cyclohexane by PhIO. A study of the catalytic intermediates in the reaction between Mn(TPP)Cl or Mn(TDCPP)Cl and PhIO was also carried out by UV–Vis and EPR spectroscopies. The reaction of Mn(TPP)Cl with PhIO showed the formation of a mixture of species MnIV(O)P·+ and MnV(O)P as intermediates, which were confirmed by the deconvolution of the UV–Vis spectra. Addition of imidazole as cocatalyst favoured the formation of the intermediate species MnV(O)P, evidenced by the UV–Vis band at 408 nm. The corresponding EPR spectra gave evidence that in the presence of imidazole, MnIV(O)P·+ species are formed only in very low amounts. For Mn(TDCPP)Cl the dominating intermediate species is MnIV(O)P·+. Addition of imidazole to halogen-substituted MnP systems does not result in increase of the C-ol yields because very stable bis-imidazole-MnP complexes are formed. Anchoring of such MnP on imidazole propyl gel (IPG) results in better catalytic activity because in this case, the catalyst is mono-coordinated to the support and imidazole favours the formation of the intermediate species MnV(O)P.

Effects of substitution for hydroxyl in the B-ring of the flavylium cation

Abstract: The electronic structure of mono, bis and trihydroxylated derivatives in the B-ring of the flavylium cation was studied The AM1 semiempirical method of molecular orbital calculations was used Data showed that substitution in the B-ring causes resonance increase between this ring and the C-ring, except for substitution on C(3′) Bond orders were interpreted through the variation in the contribution of resonance structures and they helped to explain the relative stability of the several dissubstituted isomers Another factor that contributes to this stability is the formation of a hydrogen bond in the B-ring and between the B-and C-rings The rotation enthalpies in the B-ring were calculated and they confirm that the rotation on the C(2)-C(1′) bond is free in the compounds with substitution on position 3′ The molecule planarity can be attributed to the interaction between the oxygen atom in the C-ring and the hydrogen atoms in the B-ring, or between the hydrogen atoms in these rings The charge variations are in agreement with the proposed resonance structures Substitution in the B-ring does not affect the sites of basic and nucleophilic attack

Condições adversas na vida de crianças com atraso no desenvolvimento

Abstract: The objective of the present study was to identify the risk factors to which children with delayed development referred to the Center of Applied Psychology of FFCLRP-USP over the last five years had been exposed. The group consisted of 12 boys and 10 girls ranging in age from 1 month to 8 years. The data were extracted from the interviews held with the mothers as the time of child enrollment in the service. The problems reported by de mothers on the occasion of the complaint and the adverse events and circumstances that ocurred in the child’s life were classified according to the Category System elaborated by the authors of the present study. The results showed that, in addition to retardation, the most frequent problems reported on the occasion of the complaint were speech, motor coordination, learning and agitation/restlessness problems. Analysis of the adverse circumstances in the life history of this group of children demonstrated that all of them had been exposed to one or more biological risk conditions, the most frequent being congenital problems, mother’s physical health problems during pregnancy, child’s physical health problems, convulsive seizures, complications of delivery, and hospitalization. Furthermore, 36% of the children had been exposed to environmental risk factors, especially those linked to inadequate attitudes and practices of care and education. On the basis of the results obtained, we discuss the implications of the presence of biological risks as an important condition for access to specialized services on the part of the children and their families.

Simulation study of the role and structure of monatomic ions multiple hydration shells

Abstract: The hydration structures of five monatomic cations and two monatomic anions are studied by Monte Carlo NpT simulations conducted on infinite dilute aqueous electrolyte solutions. The complete first and second hydration shells are defined by the successive minima of the radial distribution functions’ ion–water oxygen atoms. The first shell structure is determined essentially by the electrostatic charge of the ion and by the short-range ion–water molecule interactions so that it is always constituted by six molecules located at the vertices of regular octahedra unless if the distance between the charge of the ion and the opposite charge in the water molecule is large enough to allow the presence of more than six water molecules. This is the case of the K+ which presents eight molecules in its first shell. The pairs of hydrogen atoms are, in the first shell, preferentially perpendicular. The structure of the second shell is defined by the bulk tetrahedral structure induced by the water molecules so that they are similar for cations and anions. The resulting second shell densities are very close to the pure water density. Both complete hydration shells are maintained stable by means of a compromise between the strong attraction that the ion carry out on the water molecules and by the resulting repulsion between these molecules which are forced to get too close to one another.

Foraging behavior on carcasses in the necrophagic bee Trigona hypogea (Hymenoptera: Apidae)

Abstract: necrophagy; foraging behavior; Meliponinae; Apidae; stingless bees. INTRODUCTION Insects Collectively exploit a wide range of food sources, but the diets arc limited to one or a few kinds of food in different lineages. They generally encompass carbohydrates, proteins or amino acids, and salts (Roubik, 1989). In bees (Apoi- dea), for example, floral products, nectar (carbohydrates), pollen (proteins), and oils, arc their principal food components (reviewed by Wcislo and Cane, 1996). However, they can also collect urine, feces, and animal carcasses searching for mineral salts, water, and organic compounds (Baumgartner and Roubik, 1989). In stingless bees (Meliponinae), some variations occur. Besides those cited by Schwarz (1948) we have sugars from fruit pulp collection by Trigona spp. (Baumgartner and Roubik, 1989), membracid honeydew by Trigona, Oxytri- gona, Apis, etc. (Larcoa and Sakakibara, 1976; Cortopassi-Laurino, 1977; Cas- tro, 1975; Mariconi, 1963), and extrafloral nectaries (Slansky and Rodriguez, 1987; Roubik, 1989; Roubik et al., 1995; Noll et al., 1996); proteins from soybean bran by Geotrigona inusitata and fungi spores by Apis (Kerr, personal observation); and salts from blood and carcasses by Apis (Chance, 1983; Crcwe, 1985). Knowledge about such habits is limited, and the cases listed above prob- ably include some sporadic events, in which honey and pollen restriction involves temporary exploitation of uncommon sources. Thus, the only group which dis- plays fixed unusual feeding habits is the obligate necrophages [Trigona hypogea group (Camargo and Roubik, 1991)]. They have completely replaced pollen by animal flesh as a protein source (Roubik, 1982; Camargo and Roubik, 1991; I Departamento de Biologia, Faculdade de Filosofia CiSncias e Letras de Ribeir~o Preto, Univer- sidade de Silo Paulo, 14040-901 Ribeir~o Preto--SP, Brazil.

Photosubstitution Reactions of Trans-Chloro(Azine)(1,4,8,11-Tetraazacyclotetradecane)Ruthenium(II) Complexes

Abstract: Visible range photolyses of trans-[RuCl(cyclam)L]+ (cyclam = 1,4,8,11-tetraazacyclotetradecane; L = pyridine (py), 4-picoline (4-pic), isonicotinamide (isn), or 4-acetylpyridine (4-acpy)) were studied in acidic aqueous solution, and lead to exclusive azine photoaquation. The py and 4-pic complexes have a relatively high, and irradiation wavelength independent, quantum yield (0.020 < Φ < 0.025), while the isn and 4-acpy complexes have lower quantum yields (Φisn ≈ 0.006; Φ4-acpy < 0.001). The relative Φs show patterns consistent with the excited-state tuning model proposed to explain the photochemistry of other related ruthenium(II) ammines. The results indicate that the excited-state precursor of the photochemistry should be a LF* and has a strong contribution from the dz2 orbital, which should lie lower in energy than the dx2-y2. Accordingly, considering an approximate C4v symmetry for the complexes, this LF* should be a 3E. The results also suggest that the intramolecular hydrogen bonds to the chloride t...

A comunicação do enfermeiro cirúrgico na orientação do paciente: a influência cultural

Abstract: Este estudo teve como objetivo descrever a influencia da cultura na interacao verbal do enfermeiro cirurgico, na orientacao do paciente. Sob o enfoque metodologico da etnografia, os autores descrevem as caracteristicas da interacao verbal relacionadas com o conhecimento, as crencas, os valores, os padroes e a organizacao do trabalho, no contexto cultural.

Study of the catalytical intermediates of metalloporphyrins supported on imidazole propyl gel

Abstract: In this work, the catalytic intermediates for Fe(TPP) + , Fe(TDCPP) + , Fe(TFPP) + , Mn(TPP) + and Mn(TDCPP) + supported on imidazole propyl gel with PhIO were studied by UV-Vis spectrophotometry For Fe(TPP) + and Fe(TFPP) + , the study was also monitored by EPR spectroscopy The active catalytic intermediate observed for FeP-IPG is the oxo-iron (IV) porphyrin π cation radical Fe IV (O)P ·+ , which is evidenced by a decrease in the intensity of the Soret band The total re-establishment of the initial Soret band intensity for Fe(TDCPP)IPG and Fe(TFPP)IPG at the end of the reaction shows that they were completely recovered There are advantages in following the reactions of PhIO with unsubstituted Fe(TPP) + and Mn(TPP) + on IPG by UV-Vis, since they were slower and allowed to ‘see’ the intermediate species without spectral interference from the recovered catalyst, since they are only partially recovered With Fe(TPP)IPG, a band at 580 nm was detected at the beginning of the reaction, indicating the possible formation of a Fe-OIPh intermediate Supporting Mn(TPP) + on IPG leads to a shift of band V from 478 nm to 488 nm In the reaction of MnP-IPG with PhIO, we observed the disappearance of the band in 488 nm and the appearance of a band in 412 nm, which corresponds to the active catalytic intermediate Mn V (O)P as the main component, as is expected for a more efficient system The recovery of supported catalysts observed in these experiments was further proved with the possibility of their successive recyclings in cyclohexane oxidation reactions by PhIO

Function and regulation of the acid and neutral trehalases of Mucor rouxii

Abstract: Two different trehalose-hydrolysing activities, known as acid or non-regulatory trehalases, and neutral or regulatory trehalases, have been recognised in a number of fungal species. The true role of these apparently redundant hydrolases remained obscure for many years. However, recent evidence suggests that neutral trehalases would be specialised in the mobilisation of cytosolic trehalose, while acid trehalases would only hydrolyse extracellular trehalose. Results obtained with Mucor rouxii, a Zygomycete initially thought to posses only neutral trehalase activity, reinforced this hypothesis. M. rouxii grows efficiently in trehalose as the sole carbon source. Trehalose-grown or carbon-starved cells exhibit a high trehalase activity of optimum pH 4.5, bound to the external surface of the cell wall, in contrast with the neutral (pH 6.5) trehalase, which occurs in the cytosol. Other differences between the neutral and the acid trehalases are the temperature optimum (35°C and 45°C, respectively) and thermal stability (half-life of 2.5 min and 12 min at 45°C, respectively). The neutral trehalase, but not the acid trehalase, is activated in vitro by cAMP-dependent phosphorylation, stimulated by Ca2+, and inhibited by EDTA. It shows maximal activity at germination and decreases as growth proceeds. In contrast the activity of the acid trehalase is totally repressed in glucose-grown cultures and increases upon exhaustion of the carbon source, and is strongly induced by extracellular trehalose.

Universidades públicas e sociedade: uma parceria necessária

Abstract: The present article discusses the role of public universities in the Brazilian society. It occurs within the context of accelerated globalization, in the scenario of 'market', with fundamental differences between 'advanced countries' and 'less advanced countries', in relation to the privileges in the world economic market. It is proposed the adoption of the alternative scenarios (Guadilla, 1994) to superate this dichotomy, coordinating the local necessities with the world economic globalization. The role of public universities is emphasized, mainly, in the formation of critical professionals. The study indicates the necessity of integrated projects of research and education, with social and economical relevance.

The sensitization of the ligand-field state of the hexaammineruthenium(II) complex ion by organic compounds

Abstract: The sensitilized photolysis of [Ru(NH3)6]2+ by the organic dye rhodamine B and biacetyl was studied under conditions in which only the sensitizer absorbs. The reaction products resulting from ammonia aquation and Ru(II) to Ru(III) oxidation are the same for direct and sensitized photolysis. The energy transfer rate constant, calculated from te fluorescence quenching of rhodamine B, is similar to the estimated from the limiting quantum yield of the photosensitized photoaquation of the complex. Both reactions originate from a common reactive low-lying ligand-field (LF) state, which is also responsible for the direct photolysis reactions. This state, which leads directly to photoaquation, seems to have a certain charge transfer to solvent (CTTS) character, which is responsible for the photo-oxidation products. Sensitization is effective with rhodamine B (17 450 cm−1) and biacetyl (19 000 cm−1), whereas no reaction is observed with neutral red (16 900 cm−1). These results show that the excited state responsible for the photochemical reactions lies in the energy range between 16 900 cm−1 and 17 700 cm−1 and possesses spin-orbit character.

O metodo de datacao arqueologica por ressonancia paramagnetica eletronica

Abstract: The physical principles of archeological dating with the spectroscopic technique of electron paramagnetic resonance are presented. This spectroscopic technique allows the determination of the stable free radical concentration present in a sample that was produced by the environmental radiation. Using this result it is possible to determine the radiation dose, known as the archeological dose, that was necessary to produce this free radical concentration. Knowing the dose rate at the site where the sample was buried it is possible to convert the archeological dose in the age of the sample. This is a non destructive method that can be applied to bones, carbonates, paper and other electrical insulating materials and about 0.1 grams of sample are necessary