Pyrethroid toxicity in silver catfish, Rhamdia quelen

This study aimed to determine both the lethal and sublethal concentrations of Cypermethrin in young Silver Catfish (Brazilian "Jundiá", Rhamdia quelen) on aquatic environment during 96 hours, as well as to determine the Cypermethrin and Deltamethrin sublethal concentrations during the initial embryonic development period of Rhamdia quelen, and to verify their respective rates of fertilization, hatching and survival. Pyrethroid nowadays is a widely used insecticide, which presents a high toxicity to fish. In order to determine lethal and sublethal concentrations, 120 silver catfish were used; each one had an average weight of 59.58±4.50g and an average size of 20.33±2.34cm. Concentrations used were 0, 1.0, 1.5, 2.0, 2.5, 3.0, 5.0, 10.0, 15.0 and 20.0mg of Cypermethrin per liter of water (mg/L). Fish were exposed to the product in 30-liter fish tanks. In each fish tank there were four fishes and the product was applied three times, i.e., a total of twelve fish were exposed to the product at each application, and a total of 120 fish during the entire experiment (n=120). In order to determine the Cypermethrin and Deltamethrin sublethal concentrations during the initial embryonic development, ovulation induction was performed on female fishes using hormones, and then and egg collection was performed. The eggs were then hydrated and fertilized in Cypermethrin and Deltamethrin in different concentrations: 0.001, 0.01, 0.1, 1.0 and 10.0mg/L of Cypermethrin and 0.001, 0.01, 0.1, 0.5 and 1.0mg/L of Deltamethrin, in addition to the control group (0mg/L). After fertilization, the eggs were kept in containers with the respective pesticides of Cypermethrin and Deltamethrin until hatching, when hatching rate was verified. Then the alevins, from the hatching, were kept on their respective concentrations of Cypermethrin and Deltamethrin so that the survival rate could be analyzed regarding the tested insecticides, during both 12-hour and 24-hour periods. Concerning the sublethal and lethal concentrations, Silver Catfish was sensitive to the tested concentrations of Cypermethrin, showing symptoms of poisoning, such as loss of balance, swimming alteration, dyspnea (they kept their mouths and opercula open), upright swimming and sudden spiral swimming movements. The intensity of such symptoms varied in proportion to the concentration used. The concentrations above 3.0mg/L were considered lethal to the species, since every animal exposed to concentrations between 3.0 and 20.0mg/L had died, while concentrations between 1.0 and 2.5mg/L were considered sublethal. Lethal concentration of Cypermethrin to Silver catfish, in 96 hours, was 1.71 milligram per liter of water. Concerning the sublethal concentration of Cypermethrin and Deltamethrin during the initial embryonic development, the results show that both pyrethroids had significantly decreased the analyzed parameters when comparing them with the control group. It was concluded that, even with the fish being more resistant to pyrethroids in comparison with other species, both the young animals and the ones in stage of embryonic development were susceptible to the effects of these pesticides.

Celioscopic liver biopsy in silver catfish (Rhamdia quelen)

Endosurgery has been used for assessment of fish celomatic cavity, as well as for obtaining biopsies for organic analysis. Such minimally invasive access may also be used for the analysis of environmental impact on biomarkers of pollution. In Brazil, studies and literature regarding the use of celioscopy in fish are sparse. The purpose of the current study was to develop a two-port celioscopy technique to obtain liver biopsy in silver catfish (Rhamdia quelen). Six adult female silver catfish were used. The animals were anesthetized and the inspection of the celomatic cavity were performed using a telescope and celioscopic-guided liver biopsy were taken using laparoscopic Kelly forceps. On the early postoperative period, the animals were released in a confined water reservoir where mortality could be checked. The liver samples were sent for histological assessment. There were no complications during surgery on early postoperative period. It was possible to visualize meticulously several organs (liver, spleen, stomach, pancreas, swim bladder, ovaries, bowel and transverse septum). In conclusion, the surgical technique and the anesthetic protocol proposed were suitable to perform liver biopsies in silver catfish and provided low morbidity.

Arc fusion of self-fluxed nickel alloys

Self-fluxed nickel alloys are usually flame fused after thermal spraying. However, due to the practical aspects of high temperatures reached during flame fusing, large structures such as the hydraulic turbines for power generation, can not be efficiently coated. An alternative is to fuse the sprayed coating with a gas tungsten electric arc. In this case, heating is much more intensive and substrate temperature during and after the fusing operation is much lower, thus reducing the possibility that any problem will occur. In this work, coatings of self-fluxed nickel alloy fused by flame and gas tungsten arc were evaluated as protection of hydraulic turbines against cavitational damage. Several tests were performed, including the ASTM ultrasonically vibration-induced cavitation, optical and scanning electronic microscopic metallography, and hardness tests. The results showed that the arc-fused coating presented better cavitation damage resistance, probably due to its finer microstructure. A field application of this new technique is also described. A self-fluxed Ni alloy was flame sprayed in critical regions of Francis-type hydraulic turbine blades and fused by a gas tungsten arc after spraying. The blades will be inspected during the next two years.

Noise and vibration damping of Fe-Cr-x alloys

The aim of the present work is to study the noise and vibration damping capacity of ferromagnetic Fe-16%Cr base alloys (before and after heat treatment) with different Al and Mo contents. The noise damping was evaluated by the level of sound emission after an impact. The vibration damping was studied using a cantilever device. In addition to these tests, the magnetic structure of the materials was also investigated by Kerr effect. It was verified that the materials can decrease noise level in the frequency range of human earring. The vibration damping is influenced by heat treatment and chemical composition of the alloy. The improvement of vibration damping after heat treatment is ascribed to the decrease of internal stresses in materials and changes in magnetic domain structures.

Assessment of silver-stained AFLP markers for studying DNA polymorphism in proso millet (Panicum miliaceum L.)

Proso millet (Panicum miliaceum L.) is a serious weed in North America. A high number of wild proso millet biotypes are known but the genetic basis of its phenotypic variation is poorly understood. In the present study, a non-radioactive silver staining method for PCR-Amplified Fragment Length Polymorphism (AFLP) was evaluated for studying genetic polymorphism in American proso millet biotypes. Twelve biotypes and eight primer combinations with two/three and three/three selective nucleotides were used. Pair of primers with two/three selective nucleotides produced the highest number of amplified DNA fragments, while pair of primers with three/three selective nucleotides were more effective for revealing more polymorphic DNA fragments. The two better primer combinations were EcoR-AAC/Mse-CTT and EcoR-ACT/Mse-CAA with seven and eleven polymorphic DNA fragments, respectively. In a total of 450 amplified fragments, at least 339 appeared well separated in a silver stained acrylamide gel and 39 polymorphic DNA bands were scored. The level of polymorphic DNA (11.5%) using only eight pairs of primers were effective for grouping proso millet biotypes in two clusters but insufficient for separating hybrid biotypes from wild and crop. Nevertheless, the present result indicates that silver stained AFLP markers could be a cheap and important tool for studying genetic relationships in proso millet.

Recuperation and improvement of chromosome preparations stained with silver nitrate

Both periodic acid and photographic reagents have been used to remove the silver nitrate residues from cytological preparations. We used potassium ferricyanide to remove AgNO3 salts in cases of excessive chromosome impregnation. This method produced partial decolorization, with contrast enhancement. Counterstaining with Giemsa also promoted a better contrast between chromosome arms and NORs, which were preserved and retained a dark color. Application of this procedure to chromosome preparations treated sequentially for CBG banding/AgNO3 staining promoted complete decolorization of C+ regions, leading to "reverse" C-banding, generally with high contrast.

TRAP-silver staining, a highly sensitive assay for measuring telomerase activity in tumor tissue and cell lines

Measurement of telomerase activity in clinically obtained tumor samples may provide important information for use as both a diagnostic marker and a prognostic indicator for patient outcome. In order to evaluate telomerase activity in tumor tissue without radiolabeling the product, we developed a simple telomeric repeat amplification protocol-silver-staining assay that is less time-consuming, is safe and requires minimal equipment. In addition, we determined the sensitivity of the silver-staining method by using extracts of telomerase-positive thyroid carcinoma cell lines which were serially diluted from 5,000 to 10 cells. Telomerase activity was also assayed in 19 thyroid tumors, 2 normal controls and 27 bone marrow aspirates. The results indicate that the technique permits the detection of telomerase activity from 5000 to as few as 10 cells. We propose that it could be immediately applicable in many laboratories due to the minimal amount of equipment required.

Medical applications of shape memory alloys

Shape memory alloys (SMA) are materials that have the ability to return to a former shape when subjected to an appropriate thermomechanical procedure. Pseudoelastic and shape memory effects are some of the behaviors presented by these alloys. The unique properties concerning these alloys have encouraged many investigators to look for applications of SMA in different fields of human knowledge. The purpose of this review article is to present a brief discussion of the thermomechanical behavior of SMA and to describe their most promising applications in the biomedical area. These include cardiovascular and orthopedic uses, and surgical instruments.

Sedative and anesthetic activities of the essential oils of Hyptis mutabilis (Rich.) Briq. and their isolated components in silver catfish (Rhamdia quelen)

This study evaluated the sedative and anesthetic effects of the essential oils (EO) of Hyptis mutabilis (Rich.) Briq. and their isolated components on silver catfish (Rhamdia quelen). Quantitative chemical differences between the EOs obtained from leaves and inflorescences were verified, and a new chemotype rich in globulol was described. Although there were no significant differences in the time of induction for sedation and anesthesia between the EOs, only the leaf EO at 344 mg/L anesthetized all fish without side effects. Fractionation of the leaf EO was carried out by column chromatography. The isolated compounds [(+)-1-terpinen-4-ol and (-)-globulol] showed different activity from that detected for the leaf EO in proportional concentrations and similar sedation to a eugenol control at 10 mg/L. However, fish exposed to 1-terpinen-4-ol (3 and 10 mg/L) did not remain sedated for 30 min. Anesthesia was obtained with 83-190 mg/L globulol, but animals showed loss of mucus during induction and mortality at these concentrations. Synergism of the depressor effects was detected with the association of globulol and benzodiazepine (BDZ), compared with either drug alone. Fish exposed to BDZ or globulol+BDZ association showed faster recovery from anesthesia in water containing flumazenil, but the same did not occur with globulol. In conclusion, the use of globulol in aquaculture procedures should be considered only at sedative concentrations of 10 and 20 mg/L, and its mechanism of action seems not to involve the GABAA-BDZ system.

Increased immunoglobulin production in silver catfish (Rhamdia quelen) exposed to agrichemicals

Fish vaccination has been increasingly exploited as a tool to control pathogen infection. The production of immunoglobulin following vaccination might be affected by several factors such as management procedures, water temperature, and the presence of xenobiotics. In the present study, we aimed to investigate the kinetics of immunoglobulin production in silver catfish (Rhamdia quelen) inoculated with inactivated Aeromonas hydrophila and kept at two different water temperatures (17.4±0.4° or 21.3±0.3°C). The effect of a second antigen inoculation and exposure of fish to sublethal concentrations of the herbicides atrazine and glyphosate at 10% of the lethal concentration (LC50-96h) on specific serum antibodies were also investigated. Antibodies to A. hydrophila were detected as early as 7 days post-inoculation and increased steadily up to 35 days. The kinetics of antibody production were similar in fish kept at 17.4±0.4° and 21.3±0.3°C, and reinoculation of antigen at 21 days after priming failed to increase specific antibody levels. Intriguingly, we found that, in fish exposed to atrazine and glyphosate, the secretion of specific antibodies was higher than in non-exposed inoculated fish. These findings are important for the design of vaccines and vaccination strategies in Neotropical fish species. However, because atrazine and glyphosate are widespread contaminants of soil and water, their immune-stimulating effect could be harmful, in that fish living in herbicide-contaminated water might have increased concentrations of nonspecific antibodies that could mediate tissue injury.