Virulence factors in Escherichia coli strains isolated from pigs in the Ribeirao Preto region, State of Sao Paulo, Brazil.

Three-hundred faecal swabs were obtained from pigs with diarrhoea in farms located in different areas of the Ribeirao Preto region in the State of Sao Paulo. One-hundred Escherichia coli strains were isolated and tested for production of thermolabile (TL) and thermostable (STRa and STb) enterotoxins, and for the presence of colonization factors F4, F5 and F6. The strains were also tested for sensitivity to 14 antibiotics and chemotherapeutic agents. Twenty-four Escherichia coli strains produced enterotoxin STb, 5 produced LT and 3 produced STa. In the mannose-resistant haemagglutination reaction, one strain reacted positively with sheep, chicken, horse and human red blood cells and another reacted positively with guinea pig, sheep, chicken, horse and human red cells. However, both strains were negative for colonization factors F4, F5 and F6 when submitted to the slide agglutination test. All Escherichia coli strains were resistant to at least one antibiotic, the highest percentages being obtained for resistance to penicillin, tetracycline and cephalotin. In addition to the importance of the virulence factors normally encountered in enterotoxigenic Escherichia coli strains from pigs, the present results show the possible existence of new colonization factors other than F4, F5 and F6 participating in E. coli-induced pigs colibacillosis in the Ribeirao Preto region.

Evaluation of the in vitro susceptibility and emergence of mutants resistant to ciprofloxacin among multidrug resistant clinical isolates.

Two hundred and seventy-seven multidrug resistant clinical isolates [K. pneumoniae, (N = 87); E coli, (N = 30); Salmonella typhimurium (N = 100); P. aeruginosa, (N = 30); S. aureus, (N = 30)] from hospitalized patients specimens, were tested in vitro for sensitivity to Ciprofloxacin. Application of the disk diffusion test and determination of the minimal inhibitory concentration by the microdilution method indicated that, almost all isolates were sensitive to the drug. Overall, S. aureus and P. aeruginosa were the less sensitive organisms. Ciprofloxacin-resistant mutants occurred at frequencies of > or = 10(-5)/CFU.

Influence of the estrous cycle on the sensitivity to catecholamines in right atria from rats submitted to foot-shock stress

We investigated the mechanisms of the alterations in sensitivity to catecholamines in right atria from female rats exhibiting regular 4-day estrous cycles after three foot-shock sessions at estrus, metestrus, and diestrus or at diestrus, proestrus, and estrus. Right atria from stressed rats sacrificed at diestrus showed subsensitivity to noradrenaline and adrenaline. After in vitro sympathetic denervation (38 μM 6-hydroxydopamine) plus inhibition of neuronal reuptake (0.1 μM desipramine) subsensitivity to noradrenaline was abolished, but it was again evident when extraneuronal uptake was also inhibited (10 μM phenoxybenzamine and 30 μM corticosterone). The same pretreatment abolished the subsensitivity to adrenaline. After addition of 1 μM butoxamine, a β2-adrenoceptor antagonist, the tissues from stressed rats were subsensitive to adrenaline. Right atria from stressed rats sacrificed at estrus did not show any alteration in sensitivity to catecholamines. We conclude that after foot-shock stress, right atria from female rats sacrificed at diestrus showed subsensitivity of the chronotropic response to catecholamines as a result of a conformational alteration of β1-adrenoceptors, simultaneously with an increase in β2-adrenoceptor-mediated response. The mechanisms seem to be similar to those which underlie stress-induced alterations in catecholamine sensitivity in right atria from male rats. However, during estrus there are some protective factors that prevent the effects of stress on right atria.

Antibiotic 26-deoxylaidlomycin isolated from Streptomyces sp. Ar386 from Brazilian soil

An actinomycete strain (Ar386) was isolated from the soil of the Araraquara regio, SP, Brazil. The strain, named Streptomyces jacareensis, formed irregular rayed, rugose, grayish-white mycelium with sinuous, branched hyphae carrying rare isolated spores; assimilated glucose, galactose, inositol, ribose, maltose, sucrose, melibiose and starch but not mannitol, rhamnose, arabinose, xylose, lactose and raffinose; and contained LL- diaminopimelic acid in its cell wall. An antibiotic active against Gram- positive bacteria, which was characterized as being 26-deoxylaidlomycin and which may have application against poultry coccidiosis, was isolated from cultures of the strain. This was the first isolation of this antibiotic from a microorganism of the genus Streptomyces and also the first isolation of this antibiotic in Brazil.

Sensitivity of mycobacteria to different species of eucalyptus l'herit

Sensitivity profile of 10 mycobacteria of clinical interest to eight different species of Eucalyptus L'Herit was studied. A Proportion Method Indirect Test was performed to detect resistant bacilli utilizing 5 and 10 mg/ml of essential oils incorporated to Lowestein-Jensen medium. Mycobaterium tuberculosis and other slow growing mycobacteria were more sensitive to essential oils than faster growing ones. The most effective essential oils, in decreasing order, were Eucalyptus citriodora, Eucalyptus maculata and Eucalyptus tereticornis.

The δ expansion and the principle of minimal sensitivity

The δ-expansion is a nonperturbative approach for field theoretic models which combines the techniques of perturbation theory and the variational principle. Different ways of implementing the principle of minimal sensitivity to the δ-expansion produce in general different results for observables. For illustration we use the Nambu-Jona-Lasinio model for chiral symmetry restoration at finite density and compare results with those obtained with the Hartree-Fock approximation.

Calcium hydroxide and a corticosteroid-antibiotic association as dressings in cases of biopulpectomy. A comparative study in dogs' teeth.

The subject of this paper was to study the behavior of the periapical tissues of dogs' teeth after biopulpectomy and dressing with calcium hydroxide or a corticosteroid-antibiotic association, before root canal filling with zinc oxide eugenol (ZOE) or Sealapex sealers. The teeth were overinstrumented and dressed for 7 days before the root canal filling. The animals were sacrificed 180 days after treatment and the specimens were prepared for morphological analysis. Specimens treated with Sealapex presented a higher number of cases with biological closure than ZOE. When the root canals were filled with ZOE, better results were observed with the use of the Ca(OH)2 dressing.

Re-evaluation of antibiotic and mercury resistance in Escherichia coli populations isolated in 1978 from Amazonian rubber tree tappers and Indians

A study was carried out to assess the stability of antimicrobial susceptibility of wild isolates upon long-term storage using fifty-three Escherichia coli strains isolated in 1978 from feces of healthy children from the Amazon region in Brazil, exposed to low levels of antimicrobial agents, and examined for resistance to mercury and four antibiotics. All of the strains were kept in Lignieres medium at room temperature and were transferred to fresh media four times during this period. Thirty-five out of the 53 strains analyzed in 1978 were viable. Upon recovery, antibiotic and mercury resistance was estimated. All of the 35 strains maintained their original phenotype in a stable fashion, except for one multiresistant strain which became susceptible to kanamycin. Fifty-four percent of the strains exhibited a resistance phenotype, among which 47% had conjugative plasmids.

Sensitivity of AMPA receptor channel to calcium oscillations: A computational study

We used a computational model of biochemical pathways that are involved in the phosphorylation/dephosphorylation of AMPA receptor to study the receptor responses to calcium oscillations. In the model, the biochemical pathways are assumed to be located immediately under the postsynaptic membrane and we included three states of AMPA receptor: dephosphorylated, and phosphorylated in one or in two sites. To characterize the effects of calcium oscillations on the AMPA receptor, we exposed the model to stimuli with three varying parameters, namely frequency, number of pulses and calcium spike duration. Our model showed sensitivity to all of these three parameters. © 2002 Elsevier Science B.V. All rights reserved.

Benomyl sensitivity of isolates of Colletotrichum acutatum and C. gloeosporioides from citrus

Postbloom fruit drop (PFD) of citrus, caused by Colletotrichum acutatum, produces orange-brown lesions on petals and results in premature fruit drop and the retention of calyces. C. gloeosporioides is common in groves and causes postharvest anthracnose on fruit. Both diseases are controlled effectively by the fungicide benomyl in research fields and commercial orchards. Highly sensitive and resistant isolates of C. gloeosporioides were found, whereas all isolates of C. acutatum tested were moderately resistant. In preliminary studies conducted in vitro with three isolates of each, mycelial growth of sensitive isolates of C. gloeosporioides was inhibited completely by benomyl (Benlate 50 WP) at 1.0 μg/ml, whereas resistant isolates grew well at 10 μg/ml. Growth of all isolates of C. acutatum was inhibited by about 55% at 0.1 μg/ml and by 80% at 1.0 μg/ml. Spore germination of C. acutatum was inhibited more at 0.1 μg/ml than at 1.0 μg/ml or higher concentrations. In all, 20 isolates of C. acutatum from 17 groves and 20 isolates of C. gloeosporioides from 7 groves were collected from locations with different histories of benomyl usage in São Paulo, Brazil, and Florida, United States. Benomyl at 1.0 μ.g/ml completely inhibited growth of 133 isolates of C. gloeosporioides, with the exception of 7 isolates that were highly resistant to the fungicide, whereas all isolates of C. acutatum were only partially inhibited at 0.1 and 1.0 μg/ml. Analysis of variance indicated that the sensitivity of the isolates of C. acutatum was not affected by benomyl usage or grove of origin, and country of origin had only minor effects. No highly resistant or sensitive isolate of C. acutatum was recovered. Partial sequencing of the β-tubulin gene did not reveal nucleotide substitutions in codons 198 or 200 in C. acutatum that usually are associated with benomyl resistance in other fungi.

Conformation and lytic activity of eumenine mastoparan: A new antimicrobial peptide from wasp venom

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

On designing linearly tunable high-Q OTA-C filters with low sensitivity

This paper discusses a design approach for a high-Q low-sensitivity OTA-C biquad bandpass section. An optimal relationship is established between transconductances defining the differenceβ - γ in the Q-factor denominator, setting the Q-sensitivity to tuning voltages around unity. A 30-MHz filter was designed based on a 0.35μn CMOS process and VDD=3.3V. A range of circuit simulation supports the theoretical analysis. Q-factor spans from 20.5 to 60, while ensuring filter stability along the tuning range. Although a Mode-operating OTA is used, the procedure can be extended to other types of transconductor.

A low-voltage low-sensitivity sinusoidal VCO for DPLL realizations

A quasi-sinusoidal linearly tunable OTA-C VCO built with triode-region transconductors is presented. Oscillation upon power-on is ensured by RHP poles associated with gate-drain capacitances of OTA input devices. Since the OTA nonlinearity stabilizes the amplitude, the oscillation frequency f0 is first-order independent of VDD, making the VCO adequate to mixed-mode designs. A range of simulations attests the theoretical analysis. As part of a DPLL, the VCO was prototyped on a 0.8μm CMOS process, occupying an area of 0.15mm2. Nominal f0 is 1MHz, with K VCo=8.4KHz/mV. Measured sensitivity to VDD is below 2.17, while phase noise is -86dBc at 100-KHz offset. The feasibility of the VCO for higher frequencies is verified by a redesign based on a 0.35μm CMOS process and VDD=3.3V, with a linear frequency-span of l3.2MHz - 61.5MHz.

High sensitivity low cost capacitive strain gage

This paper describes a high senstivity low cost capacitive strain gage sensor. The theory, design, and sensor construction details are presented. It consists of eight capacitive sensors connected in two full bridges. The capacitive strain gage sensor structure was designed in order to produce high sensitivity and low dependence with temperature. By using a simple signal conditioning circuit constituted by a differential amplifier, a band-pass filter, and a precision rectifier the device can measure forces with resolution of 0.009 N and precision of 98.7%. It is rugged, presents linear response, and good repeatability. It presents sensitivity of 8.7 V/N and fall time of 12 ms.