Showing papers by "University of São Paulo published in 1989"

Global patterns of tectonic stress

Abstract: Regional patterns of present-day tectonic stress can be used to evaluate the forces acting on the lithosphere and to investigate intraplate seismicity. Most intraplate regions are characterized by a compressional stress regime; extension is limited almost entirely to thermally uplifted regions. In several plates the maximum horizontal stress is subparallel to the direction of absolute plate motion, suggesting that the forces driving the plates also dominate the stress distribution in the plate interior.

An invariance principle for reversible Markov processes. Applications to random motions in random environments

Abstract: We present an invariance principle for antisymmetric functions of a reversible Markov process which immediately implies convergence to Brownian motion for a wide class of random motions in random environments. We apply it to establish convergence to Brownian motion (i) for a walker moving in the infinite cluster of the two-dimensional bond percolation model, (ii) for ad-dimensional walker moving in a symmetric random environment under very mild assumptions on the distribution of the environment, (iii) for a tagged particle in ad-dimensional symmetric lattice gas which allows interchanges, (iv) for a tagged particle in ad-dimensional system of interacting Brownian particles. Our formulation also leads naturally to bounds on the diffusion constant.

A cutting plane algorithm for a clustering problem

Abstract: In this paper we consider a clustering problem that arises in qualitative data analysis. This problem can be transformed to a combinatorial optimization problem, the clique partitioning problem. We have studied the latter problem from a polyhedral point of view and determined large classes of facets of the associated polytope. These theoretical results are utilized in this paper. We describe a cutting plane algorithm that is based on the simplex method and uses exact and heuristic separation routines for some of the classes of facets mentioned before. We discuss some details of the implementation of our code and present our computational results. We mention applications from, e.g., zoology, economics, and the political sciences.

Potent and prolonged acting cyclic lactam analogues of alpha-melanotropin: design based on molecular dynamics.

Abstract: Utilizing results from previous structure-activity relationships and theoretical studies of alpha-melanotropin (alpha-MSH, Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2) and its related superpotent analogues, Ac-[Nle4,D-Phe7]-alpha-MSH and Ac-[Cys4,Cys10]-alpha-MSH, we have designed a new class of alpha-MSH4-13 and alpha-MSH4-10 cyclic lactam fragment analogues of alpha-melanotropin. The cyclic peptides have the following general structures: Ac-[Nle4,Xxx5,D-Phe7,Yyy10,Gly11]-alpha-MSH4-13- NH2 and Ac-[Nle4,Xxx5,D-Phe7,Yyy10]-alpha-MSH4-10-NH2, where Xxx = Glu or Asp and Yyy = Lys, Orn, Dab, or Dpr. Formation of the lactam bridge between the side-chain groups Xxx and Yyy was performed either in solution or on a solid-phase support. Seven cyclic peptides were prepared and bioassayed for their melanotropic potency by using standard frog (Rana pipiens) and lizard (Anolis carolinensis) skin bioassays. Relative to alpha-MSH (relative potency = 1), the potencies of the cyclic peptides in the lizard skin bioassay were as follows: alpha-MSH (1); Ac-[Nle4,Glu5,D-Phe7,Lys10,Gly11]-alpha-MSH4-13- NH2 (6); Ac-[Nle4,Asp5,D-Phe7,Lys10,Gly11]-alpha-MSH4-13- NH2 (100); Ac-[Nle4,Glu5,D-Phe7,Lys10]-alpha-MSH4-10-NH2 (9); Ac-[Nle4,Asp5,D-Phe7,Lys10]-alpha-MSH4-10-NH2 (90); Ac-[Nle4,Asp5,D-Phe7,Orn10]-alpha-MSH4-10-NH2 (20); Ac-[Nle4,Asp5,D-Phe7,Dab10]-alpha-MSH4-10-NH2 (5); Ac-[Nle4,Asp5,D-Phe7,Dpr10]-alpha-MSH4-10-NH2 (5). Similar results were obtained in the frog skin bioassay, but the analogues were much less potent. Cyclic melanotropins with 23-membered rings exhibited 100-fold higher melanotropic potency than alpha-MSH with selectivity for the lizard melanocyte receptors over the frog melanocyte receptors. Increasing or decreasing the ring size of these cyclic melanotropins from 23 diminishes the biological potency of the resulting cyclic peptide. The 23- and 24-membered ring analogues showed prolonged (residual) biological activities in both biological assays, but the smaller ring systems (20, 21, 22) did not. These results provide new insights into the structural and conformational requirements of alpha-MSH and its analogues at two different types of pigment cell (melanocyte) receptors.

The pathogenic effect of IgG4 autoantibodies in endemic pemphigus foliaceus (fogo selvagem).

Abstract: Endemic pemphigus foliaceus, or fogo selvagem, is an autoimmune blistering skin disease caused by IgG autoantibodies to a desmosome-associated glycoprotein We studied the IgG subclasses with autoantibody activity in serum from 29 patients with active disease and in the skin lesions of 18 patients by immunofluorescence, using IgG-subclass-specific monoclonal antibodies The predominant disease autoantibodies present in all patients were of the IgG4 subclass IgG1 and IgG2 autoantibodies were detected in low titer in the 29 patients: IgG1 in 23 patients and IgG2 in 9 IgG3 autoantibodies were not detected in the serum of any patient Direct immunofluorescence testing of skin lesions showed a preferential deposition of IgG4 on the keratinocyte surface The pathogenic effect of IgG4 was demonstrated by the passive transfer of fractions containing IgG4 autoantibodies from the patients to neonatal BALB/c mice The disease of the patients was reproduced clinically, histologically, and immunologically in these animals Only IgG4 autoantibodies were detected by direct immunofluorescence, bound to the epidermis in the lesions of the mice, and by immunoelectron microscopy at the keratinocyte surface IgG4 has previously been reported to be a blocking or protective antibody because it has poor effector functions in vitro, as compared with the other IgG subclasses The finding that it is the pathogenic autoantibody in fogo selvagem raises the possibility that it may also be important in other autoimmune disease

Efficient ethanol production from glucose, lactose, and xylose by recombinant Escherichia coli.

Abstract: Lactose and all of the major sugars (glucose, xylose, arabinose, galactose, and mannose) present in cellulose and hemicellulose were converted to ethanol by recombinant Escherichia coli containing plasmid-borne genes encoding the enzymes for the ethanol pathway from Zymomonas mobilis. Environmental tolerances, plasmid stability, expression of Z. mobilis pyruvate decarboxylase, substrate range, and ethanol production (from glucose, lactose, and xylose) were compared among eight American Type Culture Collection strains. E. coli ATCC 9637(pLO1297), ATCC 11303(pLO1297), and ATCC 15224(pLO1297) were selected for further development on the basis of environmental hardiness and ethanol production. Volumetric ethanol productivities per hour in batch culture were 1.4 g/liter for glucose (12%), 1.3 g/liter for lactose (12%), and 0.64 g/liter for xylose (8%). Ethanol productivities per hour ranged from 2.1 g/g of cell dry weight with 12% glucose to 1.3 g/g of cell dry weight with 8% xylose. The ethanol yield per gram of xylose was higher for recombinant E. coli than commonly reported for Saccharomyces cerevisiae with glucose. Glucose (12%), lactose (12%), and xylose (8%) were converted to (by volume) 7.2% ethanol, 6.5% ethanol, and 5.2% ethanol, respectively.

Mechanism by which cellulose triggers cellobiohydrolase I gene expression in Trichoderma reesei.

Abstract: The expression of cellobiohydrolase I mRNA from Trichoderma reesei, measured by Northern blot hybridization, is controlled by the nature of carbon sources used in the culture medium. Cellulose and the soluble disaccharide sophorose, but not glycerol or glucose, act as inducers. Cellobiohydrolase I mRNA was undetectable when antibodies to the major members of the cellulolytic system were present in the culture medium prior to the addition of cellulose. These antibodies had no repressive effect if sophorose was used as an inducer. The results strongly suggest that a low constitutive cellulolytic system catalyzes the formation of a soluble inducer from cellulose and that this inducer triggers the expression of the cellobiohydrolase I gene transcript, most probably at the transcription level.

Complications and hazards of gastrointestinal endoscopy

Abstract: The diagnostic and therapeutic contribution of fiberoptic endoscopy to the advancement of the knowledge of gastrointestinal disease and to its proper management is already established. Technical refinements in the new instruments and extensive acceptance of the advantages of the method makes fiberendoscopy a procedure widely used throughout the world. Therefore, the appreciation of its potential risk of complications and hazards is justified. This review summarizes the complications and hazards of fiberoptic gastrointestinal endoscopy gleaned from reports of endoscopic surveys and individual experiences. Causes and means whereby complications related to upper intestinal and colonic endoscopy can be prevented or treated are discussed.

Hypertonic and hyperoncotic resuscitation from severe hemorrhagic shock in dogs: a comparative study.

Abstract: Single bolus injections of hypertonic (7.5%) NaCl (H), hyperoncotic (6%) dextran-70 (D), or of their combination (HD) were given to severely bled (54.2 +/- 1.3 ml/kg) anesthetized dogs. Two shock procedures (30 or 60 min at 35 mm Hg) were tested. Survival was highest (11/12) after HD, lower (9/12) after H, and lowest (7/12) after D; it was higher (15/18 vs. 12/18) after the shorter vs. longer shock procedure. Cardiac index (CI) was restored to 83%-104% of prehemorrhage levels immediately after HD or H; 3 h later it was down to 67%-71% of control; after D, CI was stable at 41% to 50% of control; no differences in the relative performances of the agents tested in the 30 or 60-min shock durations. Arterial pressure recovered to near control levels in all groups; consequently, systemic vascular resistance was reduced after H and HD, but increased after D. Plasma volume recovered to 95% of control after H, 105% of control after HD, but only to 80% after D; however, the response to H was transient. Metabolic acidosis was partially reverted by all solutions. Plasma Na+ was transiently raised by H and HD. Overall differences detected between H vs. HD tend to favor HD as a resuscitative solution.

Additional ferromagnetic phases in the FeNdB system and the effect of a 600°C annealing

Abstract: In the FeNd system an additional ferromagnetic phase with Tc = 245 ± 10 °C is found. In the ternary FeNdB system, magnetic analysis shows two ferromagnetic phases with Tc = 245 and 285 °C in as-cast alloys, in addition to Fe14Nd2B. Those phases are formed through the eutectic solidification of a neodymium-rich liquid at the boron-poor side of the system, suppressing the formation of Fe14Nd2B. An annealing at 600 °C dissolves the phase with Tc = 245 °C and develops Fe14Nd2B. This results in an Hci increase from 3.9 kOe in the as-cast to 14.1 kOe in the annealed condition for an Fe-80at.%Nd-5at.%B alloy. This suggests that the dissolution of additional ferromagnetic phases in the intergranular regions of sintered FeNdB magnets might be the positive effect of the 600 °C annealing.

Life Cycle and Culturing of Phytomonas serpens (Gibbs), a Trypanosomatid Parasite of Tomatoes

Abstract: Pure cultures of a trypanosomatid isolated from tomato fruits infected laboratory-raised tomatoes and nymphs of the hemipieran coreid Phthia picta. The flagellate could be transmitted back and forth from tomatoes to insects. Light and electron microscopy studies were done on culture, tomato and insect forms. Examination of enzymes of the ornithine-arginine metabolism revealed absence of arginase and presence of arginine deiminase and citrulline hydrolase. Monoclonal antibodies specific for Phytomonas spp. reacted positively with tomato and insect forms. Endonuclease digestion of the k-DNA of various Phytomonas spp. revealed a unique, distinctive pattern for the tomato flagellate. This flagellate thus seems to constitute a separate species of Phytomonas which we now call Phytomonas serpens (Gibbs).

Superoxide-independent hydrogen peroxide release by activated macrophages.

Abstract: The present data show that freshly explanted BCG-activated mouse peritoneal macrophages release large quantities of hydrogen peroxide upon initial contact with a foreign substratum, without the requirement for other membrane stimuli such as phorbol diesters. The hydrogen peroxide detected under these conditions does not originate from extracellularly released superoxide, since 2 x 10(5) BCG-activated macrophages spontaneously released 1.6 nmol hydrogen peroxide but only 0.2 nmol superoxide. Thus, more than 90% of the hydrogen peroxide detected was not derived from extracellular superoxide dismutation. The dissociation between hydrogen peroxide and superoxide release was further demonstrated in cytochalasin B- or lidocaine-treated cells or in the absence of glucose. Under these conditions, hydrogen peroxide release was markedly inhibited while superoxide release was unaffected. These observations provide evidence that another metabolic pathway is involved in the generation and release of hydrogen peroxide during adherence and spreading of freshly explanted activated macrophages onto a substratum.

Projections of Gibbs measures may be non-Gibbsian

Abstract: Consider the + phase of the two dimensional nearest neighbor ferromagnetic Ising model at a temperature belowT c . Let ν+ be the restriction of this measure to a coordinate axis. We prove that there is no one dimensional translation invariant summable interaction for which ν+ is a Gibbs measure. This is proven by showing that if such an interaction existed, ν+ would have large deviation properties different from those it actually has. Percolation methods are used in the proof.

Electron tunneling pathways in proteins: influences on the transfer rate.

Abstract: A strategy for calculating the tunneling matrix element dependence on the medium intervening between donor and acceptor in specific proteins is described. The scheme is based on prior studies of small molecules and is general enough to allow inclusion of through bond and through space contributions to the electronic tunneling interaction. This strategy should allow the prediction of relative electron transfer rates in a number of proteins. It will therefore serve as a design tool and will be explicitly testable, in contrast with calculations on single molecules. As an example, the method is applied to ruthenated myoglobin and the tunneling matrix elements are estimated. Quantitative improvements of the model are described and effects due to motion of the bridging protein are discussed. The method should be of use for designing target proteins having tailored electron transfer rates for production with site directed mutagenesis. The relevance of the technique to understanding certain photosynthetic reaction center electron transfer rates is discussed.

Dihexadecyl phosphate monolayers: Intralayer and interlayer interactions

Abstract: Etude de la stabilite des couches monomoleculaires de bromure de dioctadecyldimethylammonium et de dihexadecyl phosphate deposees sur du mica

Electrochemical Behavior of Copper in 0.5 M H2SO4 Solutions in the Absence and Presence of Fe(III) and Benzotriazole

Abstract: The electrochemical behavior of copper in 0.5 M deaerated sulfuric acid in the absence and presence of benzotriazole (BTAH) and ferric ions has been investigated with rotating disk electrodes. The BTAH inhibitive effect initiates at concentrations as low as 10−7 M. The mechanism of Cu/Cu(II) reaction is the same in the absence and presence of low BTAH concentrations (<10−5 M). For higher inhibitor concentrations, different processes must be considered to understand the interface metal-solution behavior: the formation of a Cu(I)BTA film, the presence of disproportionation reaction Cu + Cu(II) → 2Cu(I) and the complexation of Cu(II) ions by BTAH. The presence of Fe(III) ions in 0.5 M H2SO4 does not affect the anodic dissolution of copper. However, in the presence of BTAH, the addition of Fe(III) makes the inhibitor less effective. From anodic polarization measurements at constant potential the film adsorption has been evaluated by using the Langmuir adsorption isotherm.