Manipulation of fire ant density, Solenopsis spp., for short-term reduction of Diatraea saccharalis larval densities in Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of activation on the multipoint immobilization of penicillin G acylase on macroporous silica

Penicillin G acylase is the second most important enzyme used by industry in an immobilized form. Penicillin hydrolysis is its main application. This reaction is used to produce 6-aminopenicillanic acid (6-APA), an intermediate in the synthesis of semisynthetic antibiotics. This work aims to compare catalytic properties of different penicillin G acylase (PGA) derivatives obtained by multipoint immobilization of the enzyme on macroporous silica. Enzyme amino groups react with different aldehyde groups produced in the support using either glutaraldehyde or glyoxyl activation. In the former method, silica reacts with g-aminopropyltriethoxysilane (g-APTS) and glutaraldehyde; in the latter, a reaction with glycidoxypropyltrimethoxysilane (GPTMS) is followed by acid hydrolysis and oxidation using sodium periodate. This work determines the influence of degree of activation, using glutaraldehyde, on immobilization parameters. PGA was immobilized on these two different supports. Maximum enzyme load, immobilized enzyme activity (derivative activity), rate of immobilization and thermal stability were checked for both cases. For glutaraldehyde activation, the results showed that 0.5% of the g-APTS is sufficient for all the hydroxyl groups in the silica to react. They also showed that degree of activation only affects immobilization yield and reaction velocity and that reduction of the glutaraldehyde derivatives with sodium borohydride does not affect their thermal stability. In comparing the derivatives obtained using glyoxyl and glutaraldehyde activation, it was observed that the glyoxyl derivatives presented better immobilization parameters, with a maximum enzyme load of 264 IU/g silica and a half-life of 20 minutes at 60 °C.

Evaluation of shot peening on the fatigue strength of anodized Ti-6Al-4V alloy

The increasingly design requirements for modern engineering applications resulted in the development of new materials with improved mechanical properties. Low density, combined with excellent weight/strength ratio as well as corrosion resistance, make the titanium attractive for application in landing gears. Fatigue control is a fundamental parameter to be considered in the development of mechanical components. The aim of this research is to analyze the fatigue behavior of anodized Ti-6Al-4V alloy and the influence of shot peening pre treatment on the experimental data. Axial fatigue tests (R = 0.1) were performed, and a significant reduction in the fatigue strength of anodized Ti-6Al-4V was observed. The shot peening superficial treatment, which objective is to create a compressive residual stress field in the surface layers, showed efficiency to increase the fatigue life of anodized material. Experimental data were represented by S-N curves. Scanning electron microscopy technique (SEM) was used to observe crack origin sites.

Determination of the probable ontogenic time of action of lethal factors on the second chromosome of Drosophila melanogaster derived from a natural population

From the study of the genetic load of second chromosome factors in a natural population of Drosophila melanogaster, 15 lethal-bearing strains were recovered and maintained in the laboratory balanced against Ins (2L + 2R), Cy, L-4. For each lethal factor, the probable time of action during development was determined by the appearance of a sharp reduction, at any given stage, in the frequency of individuals compared to that expected in the absence of the lethal factor. Carried out in this way, the analysis suggested that seven were embryonic lethals, two larval lethals and three pupal lethals. Additionally, three gave no evidence of affecting any of the above-mentioned stages; these are interpreted as gametic lethals.

Behavioural and neurochemical effects of phosphatidylserine in MPTP lesion of the substantia nigra of rats

The present study investigated the effects of intranigral MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) infusion on rats treated with phosphatidylserine and evaluated in two memory tasks and on striatal dopamine levels. The results indicated that MPTP produced a significant decrease in the avoidance number in comparison to sham-operated and non-operated rats submitted to a two-way avoidance task. MPTP-lesioned rats exhibited an increase in the latencies to find the platform in cued version of the water maze in comparison to sham-operated and non-operated animals. The tested toxin reduced striatal dopamine levels in comparison to sham-operated and non-operated groups. A final surprising result was that phosphatidylserine was unable to reverse the cognitive deficits produced by MPTP or the reduction of striatal dopamine levels. In conclusion, the data suggest that MPTP is a good model to study the early impairment associated with Parkinson's disease and phosphatidylserine did not improve the memory impairment induced by MPTP. (C) 2003 Elsevier B.V. All rights reserved.

POSSIBLE MECHANISMS FOR REDUCTION OF CIRCULATING CONCENTRATIONS OF PROGESTERONE BY INTERFERON-ALPHA IN COWS - EFFECTS ON HYPERTHERMIA, LUTEAL CELLS, METABOLISM OF PROGESTERONE AND SECRETION OF LH

Experiments were performed to determine the mechanism by which recombinant bovine interferon-alpha(I)1 (rbIFN-alpha) causes an acute reduction in plasma concentrations of progesterone. In experiment 1, administration of a prostaglandin synthesis inhibitor blocked rbIFN-alpha-induced hyperthermia but did not prevent the decline in plasma concentrations of progesterone. The decline in progesterone concentrations caused by rbIFN-alpha was, therefore, not a direct consequence of the associated hyperthermia or of pathways mediated through prostaglandin synthesis. It is also unlikely that rbIFN-alpha acts to increase the clearance of progesterone since injection of rbIFN-alpha did not decrease plasma concentrations of progesterone in ovariectomized cows given an intravaginal implant of progesterone (experiment 2). In experiment 3, rbIFN-alpha did not affect basal and LH-induced release of progesterone from cultured luteal slices, indicating that rbIFN-alpha is unlikely to affect luteal function directly. Injection of rbIFN-alpha did, however, cause a decrease in plasma concentrations of LH in ovariectomized cows (experiment 4) that coincided temporally with the decrease in progesterone concentrations seen in cows having a functional corpus luteum. The present results strongly suggest that rbIFN-alpha acts to reduce secretion of progesterone by interfering with pituitary support for luteal synthesis of progesterone. The finding that rbIFN-alpha can inhibit LH secretion implies that interferon-alpha molecules should be considered among the cytokines that can regulate hypothalamic or pituitary function.