Study on cheliceral sensilla of the brown dog tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) involved in taste perception of phagostimulants

Phagostimulants are chemical compounds that stimulate feeding. Some tick species are known to have pores in their inner cheliceral digits, called pit sensillum (ps), which are involved in taste perception. This study investigated the existence of ps in chelicerae of Rhipicephalus sanguineus ticks by scanning electron microscopy (SEM) and their involvement in the perception of phagostimulatory substances, such as the salts potassium chloride and sodium chloride (KCl and NaCl), sugars (glucose, sucrose and fructose), purines (guanine and hypoxanthine), the nucleotide adenosine triphosphate (ATP) and the tripeptide reduced glutathione (GSH), as well as their combinations at different concentrations. By means of scanning electron microscopy, a ps was observed at the expected location. Using a single-sensillum recording technique, strong activity by R. sanguineus cheliceral sensilla in response to glucose, ATP, GSH and high concentrations of salts was recorded. The responses to ATP and to KCl at 1M were multicellular, while the responses to the other stimulant compounds were monocellular. Glucose and GSH stimulated different neurons. The taste response of R. sanguineus chelicerae seemed to be selective, given that substances that were not expected to participate in this tick's biology were not perceived.

Electrophysiological responses of the olfactory receptors of the tick Amblyomma cajennense (Acari: Ixodidae) to host-related and tick pheromone-related synthetic compounds

In the present study, host-related and tick pheromone-related chemical compounds were tested by means of the tip-recording technique in order to obtain electrophysiological responses in olfactory sensilla of non-fed Amblyomma cajennense ticks. The following chemicals were tested on the multiporose sensilla DI.1, located anterior to Haller's organ, and the sensillum DII.1, in the anterior pit of this organ: isobutyric acid, butyric acid, valeric acid, trans-2-heptenal, heptanal, benzaldehyde, salicylaldehyde, nonanal, m-, o- and p-tolualdehyde, 2-furaldehyde, 3-pentanone, γ-valerolactone and 1-octen-3-ol (which are all vertebrate-associated volatiles); and 2,6-dichlorophenol (2,6-DCP), 2-nitrophenol, methyl salicylate and nonanoic acid (tick pheromone components). These were used at 10(-3)M and 10(-2)M on at least 10 ticks per substance, and the chemicals that were found to be active at these concentrations were then tested as a series from 10(-6)M to 10(-2)M, in decadic steps, on at least 15 ticks per substance. 2,6-DCP was active on both sensilla, with detection thresholds of 10(-6)M on the DI.1 sensillum and 10(-4)M on the DII.1 sensillum. The olfactory neurons of this sensillum also responded to nonanal at the highest concentration used (10(-2)M), while those of DII.1 responded not only to 2.6 DCP but also to 2-nitrophenol (to the same extent as to 2,6-DCP) and to 1-octen-3-ol. These results confirm the importance of 2,6-DCP in the chemical ecology of A. cajennense and indicate other compounds that may interfere with the behavior of this tick and which should be investigated.

Differences in the behavior of Rhipicephalus sanguineus tested against resistant and susceptible dogs

To ascertain whether brown dog tick Rhipicephalus sp. infests resistant (beagle) and susceptible (English cocker spaniel) dogs differently, five animals of each breed were maintained in a kennel whose walls were infested with 7,000 larvae, 320 nymphs, 80 males and 80 females, in 3 infestations, at 10-day intervals. Five times more ticks were found on cocker spaniels (498) than on beagles (96). Substances were collected by rubbing pieces of clean flannel on the dogs for 15 min and these were tested for arrestment and attractiveness of ticks. Three choices were offered: cocker extract vs. control; beagle extract vs. control, and cocker extract vs. beagle extract. When allowed to choose between substances rubbed from dogs and a control, more ticks were arrested by extracts from the cockers than from beagles. In the arrestment tests with only a choice between substances from dogs of each breed, more ticks were arrested by cocker substances. To test for attraction, capsules containing adsorbent were used and the tests were carried out in a Y-olfactometer. Fifteen males and 15 females were tested, for each treatment. In the olfactometer, the ticks were not attracted to the odor of either breed, however the odor of the Beagle was apparently repellent. These results indicate that R. sanguineus can use substances from the dogs to differentiate susceptible English Cocker Spaniels from resistant Beagles.

Repellent activity of DEET against Amblyomma cajennense (Acari: Ixodidae) nymphs submitted to different laboratory bioassays

This study was developed to evaluate the repellent activity of N,N-diethyl-3-methylbenzamide (DEET) against Amblyomma cajennense nymphs. Two repellent bioassays were compared and the effective concentration and repellent time were calculated. The fingertip test was accomplished to evaluate in vivo four concentrations of the compound (0.200; 0.100; 0.050 and 0.025 mg.cm⁻²) and the filter-paper bioassay to evaluate in vitro the two highest concentrations.The compound provided repellence higher than 90% in all concentrations and at least 95% repellency in the highest concentration over 5 hours. The effective concentration against 50% of tested nymphs (EC50) was 0.006 mg.cm⁻² and the EC99 was 0.036 mg.cm⁻². Those concentrations were lower than the ones obtained against other tick species, denoting the effectiveness of DEET against A. cajennense. The repellency time against 50% of the ticks (RT50) was 4.8 hours and the RT90 was 2.7 hours. Both bioassays were adequate to evaluate A. cajennense repellency and provided similar results; however the in vivo test is more appropriate to estimate the effective concentration and repellency time.

Efficacy of 2,6-dichlorophenol lure to control Dermacentor nitens

This study was carried out with the objective of evaluating the efficacy of a 2,6-dichlorophenol (2,6-DCP) lure to control Dermacentor nitens (Acari: Ixodidae). Slow-release formulations of the pheromone formulated with and without cypermethrin were prepared. Olfactometer bioassays were used to define the best dose of the pheromone and to evaluate the effect of cypermethrin with 2,6-DCP attractiveness. Sexually active males were released 15 cm from 2 cmx1 cm pieces of polypropylene treated with different odors: 2,6-DCP in a liposphere system (1.5, 30 and 300 microg--without cypermethrin and 30 microg--with cypermethrin) and 2,6-DCP in hexane (30 microg). The tests were conducted 7 and 15 days after the preparation of the odor sources. The percentages of males that oriented, or showed directional movement toward the stimulus, and their tracks were recorded. Lures (10 cmx2 cm pieces of polypropylene) treated with the best dose of the liposphere formulation (30 microg) were prepared. The lures were evaluated in horses that had been artificially infested with D. nitens. The horses' ears were infested with 3000 D. nitens larvae per ear, once weekly for 4 weeks. The animals were divided into three groups: control, 2,6-DCP and 2,6-DCP+cypermethrin. On day 0, the lures of their respective treatments were attached to the horses' napes. From days 6 to 20 after attachment, female ticks of 4 mm or over in length were counted on the ears, every 2 or 3 days. Olfactometer analysis showed higher orientation to 30 microg dose and more prolonged release of the pheromone in the liposphere formulation than in hexane; cypermethrin did not interfere with the attractive effect of the pheromone. The lures were efficient in the first 10 days after attachment, when the mean number of females was higher in the control group (24.9) than in 2,6-DCP and cypermethrin (5.4), and 2,6-DCP (9.2) groups. After that period the number of females was similar in the control and treated groups. These results indicate that 2,6-DCP lures used in a liposphere formulation can control D. nitens for at least 10 days by preventing its copulation. However, further evaluation of longer-term pheromone release under natural conditions is needed in order to validate this kind of control. In addition, the use of extra lures on the horse's tail may help to control populations on the hindquarters.

Protective effect of an aqueous extract of Harpagophytum procumbens upon Escherichia coli strains submitted to the lethal action of stannous chloride

Regardless of its lethal effects upon Escherichia coli (E. coli) cultures trough the production of free radicals (FR), stannous chloride (SnCl2) remains to be the most used reducing agent on the production of technetium-99m radiopharmaceuticals, to obtain images on nuclear medicine. Moreover, authors have reported that vegetal extracts are able to protect Escherichia coli cultures against the cytotoxicity of this agent. Harpagophytum procumbens, also known as Devil's Claw, is a plant used in folk medicine, as an analgesic and anti-inflammatory in cases of joint and back pain, on the treatment of degenerative rheumatoid arthritis, osteoarthritis, kidney inflammation and heart diseases. The presence of this extract reduced the lesive effects of SnCl2 upon E. coli AB1157 (proficient in DNA repair), BW9091 (deficient in the xthA gene) and BH110 (deficient in the xthA, nfo and fpg genes) cultures, and the deficient strains (BW9091 e BH110) were more sensible to this SnCl2 action than the proficient one. The substances in the extract could be acting as: (i) chelator of the stannous ions, avoiding the generation of FR, (ii) FR scavenger, protecting the cells against the oxidation, and/or (iii) an oxidant compound acting upon the stannous ions, reducing the SnCl2 cytotoxicity.

Effect of the Cymbopogon citratus, Maytenus ilicifolia and Baccharis genistelloides extracts against the stannous chloride oxidative damage in Escherichia coli

Stannous ion has been used in different sectors of human interest, such as in food industry and in health sciences. Much is known about stannous chloride (SnCl(2)) toxicity, although, there is no general agreement regarding its genotoxicity. Cymbopogon citratus, Maytenus ilicifolia and Baccharis genistelloides extracts have been used in popular medicine. We evaluated the influence of these crude extracts on the survival of the Escherichia coli wild type (AB 1157) strain submitted to SnCl(2) treatment. Reactive oxygen species (ROS) can be generated by a Fenton like reaction induced by SnCl(2). E. coli culture was treated simultaneously with SnCl(2) and a specific extract. Our results showed a reduction of the SnCl(2) effect on the survival of the cultures in presence of the crude extracts. The extract of M. ilicifolia showed the highest level of protection action against the SnCl(2) effect in comparison with the other extracts. This protector effect could due to the redox properties of these crude extracts. The compounds in the crude extracts could (i) chelate stannous ions, protecting them against the oxidation and avoiding the generation of ROS, (ii) be a scavenger of the ROS generated by the SnCl(2) oxidation and/or (iii) have oxidant compounds that could oxidise the stannous ions, abolishing or reducing the SnCl(2) effect.

Float-polishing process and analysis of float-polished quartz

A fluid-mechanical model is developed for the float-polishing process. In this model laminar flow between the sample and the lap results in pressure gradients at the grooves that support the sample on a fluid layer. The laminar fluid motion also produces supersmooth, damage-free surfaces. Quartz substrates for applications in high-stress environments were float polished, and their surfaces were analyzed by optical scatterometry, photoacoustic spectroscopy, and atomic force microscopy. The removal of 100 µm of material by a lapping-polishing process, with final float polishing, left low levels of subsurface damage, with a surface roughness of approximately 0.2-nm rms.