Pilot investigation into osteotome hard surface coating and cutting-edge degradation.

BACKGROUND: Osteotomes are bone cutting tools commonly reused in orthopedic surgical procedures. Despite undergoing rigorous cleaning, visual inspection, and sterilization procedures between every use, the condition of the cutting blade edge is commonly not qualitatively assessed. Subjective feedback from surgeons suggests a large variation in osteotome cutting-edge sharpness is found during use. This study seeks to investigate the retention of osteotome cutting-edge sharpness by comparing the wear resistance of as-supplied, electroless nickel, and titanium nitride coated osteotomes following a series of bone cutting tests. METHODS: Changes in edge sharpness were assessed using visual inspection, depth penetration testing that quantified change in the blade sharpness index, and scanning electron microscopy visual analysis. Visual inspection of each osteotome blade edge was then compared to qualitative blade sharpness index measurement. RESULTS: After use, no cutting-edge damage or change in blade sharpness was detected by visual examination of all three osteotomes; however, the as-supplied osteotome demonstrated 50% loss of blade sharpness index compared to 30% and 15% reduction for the electroless nickel and titanium nitride coated osteotomes, respectively. This finding was supported by scanning electron microscopy evaluation that found greater mechanical damage had occurred along the cutting edge of the as-supplied osteotome compared to the two coated with wear resistant materials. CONCLUSIONS: The rapid loss of blade sharpness found in the as-supplied osteotome supports the degradation in cutting performance frequently reported by surgeons. The findings from this study demonstrate blade sharpness index better detects cutting-edge wear compared to visual inspection. Results from this pilot study also suggest the coating of osteotomes in hard-wearing biocompatible materials assists in retaining cutting-edge sharpness over multiple uses. Further study using a larger sample size is required to validate these findings.

Activity and shelter-related behavior in Rhodnius prolixus: The role of host odours.

Triatomine bugs are considered nocturnal insects that feed on the blood of vertebrates and remain hidden inside narrow shelters during daylight hours. Nevertheless, it is not clear whether these insects become active and leave their shelters on a daily basis, less frequently or, even fortnightly. Activity patterns were studied in Rhodnius prolixus Stål, 1859 (Hemiptera: Triatominae) associated with shelters to evaluate whether the decision to leave a shelter depends on bug starvation and the presence of host odours. Experiments were conducted with groups of 5th instar nymphs released in an experimental arena offering an artificial shelter consisting of a piece of corrugated cardboard positioned in its centre. Results indicate that host odours promoted a significant increase in shelter related activity, i.e. shelter-leaving or entering movements, and also in bug locomotion. This increase could only be observed with bugs starved for 30 or 60 days, but not for 21 days. Most R. prolixus nymphs that left shelters and engaged in locomotory activity were starved and in the presence of host odours. Even though R. prolixus is mostly considered a very active and "aggressive" triatomine, our results contradict this perspective and suggest that its main strategy regarding hosts is to wait and carefully evaluate feeding chances before becoming exposed. This behavioural strategy might have arisen through their evolution in palm trees in association with a diverse fauna that may impose predation risks.

Female odours promote the activation of sheltered kissing bug Rhodnius prolixus males and modulate their orientation.

The existence of a pheromone emitted during copulation has been reported for Rhodnius prolixus (Hemiptera: Reduviidae) Stål. Adults possess one pair of metasternal glands (MGs) from which female R. prolixus release volatiles mainly at night. We investigated whether these volatiles emitted by adult R. prolixus can modulate sexual-related behaviours of opposite and/or same sex individuals. We first used a shelter bioassay to test if adult activity patterns can be affected by chemical signals emitted by opposite sex conspecifics. We observed that males left the shelter more frequently in the presence of females, showing higher activity and an increase of intrasexual copulation attempts. Females showed no shelter-related activation in the presence of male odours. Second, we used a locomotion compensator device to investigate whether females or males show oriented responses to odours emitted by adults. We found that males oriented towards air currents carrying female odours but females did not orient towards odours emitted by adults. Finally, we observed that males oriented towards the female MG compounds. Thus, a volatile chemical signal emitted by females from their MGs promoted the activation of sheltered males and modulated orientation to air currents.

Female metasternal gland odours mediate male aggregation in Rhodnius prolixus, a triatomid bug.

We investigated whether metasternal gland (MG) products mediate male aggregation during mating in Rhodnius prolixus (Heteroptera: Reduviidae) Stål, 1859, through selective occlusion of female MGs. Pairs of insects presenting intact MGs mated and other males aggregated around them confirming conclusions from previous studies. However, when female MGs were occluded, males did not aggregate. Conversely, the occlusion of male MGs did not affect aggregation of males. The present experiments demonstrated that the products emitted by the MGs of a mating R. prolixus female induce other males to aggregate around the mating pair. Aggregation behaviour of males probably results from the eventual release of volatiles from the female's MGs. We reinforce the hypothesis suggesting that the compounds produced by the MGs of R. prolixus act as sexual communication signals for this species.

Structure elucidation and synthesis of dioxolanes emitted by two Triatoma species (Hemiptera: Reduviidae).

Volatiles from the metasternal glands of two species of true bugs of the Triatominae subfamily, Triatoma brasiliensis and Triatoma infestans, were analyzed by SPME-GC/MS. Two sets of new natural products were found: (4S,5S)- and (4R,5R)-2,2,4-triethyl-5-methyl-1,3-dioxolane (1) (major component) and (4S*,5S*)-2,4-diethyl-2,5-dimethyl-1,3-dioxolane (2) (trace component), (2R/S,4S,5S)- as well as (2R/S,4R,5R)-4-ethyl-5-methyl-2-(1-methylethyl)-1,3-dioxolane (3) (minor component), (2R/S,4S*,5S*)-4-ethyl-5-methyl-2-(1-methylpropyl)-1,3-dioxolane (4) (trace component), and (2R/S,4S*,5S*)-4-ethyl-5-methyl-2-(2-methylpropyl)-1,3-dioxolane (5) (trace component). Syntheses of optically active 1 and 3 were carried out by reacting pure enantiomers of 2,3-pentanediol with 3-pentanone or 2-methylpropanal. The preparation of pure stereoisomers of 2,3-pentanediol involved a novel key step for the synthesis of secondary alcohols: the reduction of a carboxylic ester by means of DIBAH and in situ alkylation of the intermediate by Grignard reaction at low temperature. Starting from the pure enantiomers of methyl lactate, all four stereoisomers of 2,3-pentanediol were synthesized and transformed to the corresponding isomers of 1 and 2. Relative configurations of the natural products and enantiomeric compositions of naturally occurring 1 and 2 were determined by comparison of their mass spectra and gas chromatographic retention times (co-injection) with those of authentic reference samples.

Behavioral evidence of an ectoparasitic interaction between Triatoma pseudomaculata Corrêa e Espínola (Heteroptera: Reduviidae) and Periplaneta americana (L.) (Blattodea: Blattidae).

The present work tested whether Triatoma pseudomaculata Corrêa & Espínola shows behavioral traits indicating that it is capable of feeding on arthropods. We consistently observed nymphs extending their proboscis in the direction of cockroaches and attempting to bite. Insects presented a preference for biting specific cockroach body parts. Our results suggest that arthropod hemolymph represents an alternative source of food that increases the survival of T. pseudomaculata individuals undergoing long starvation.

(4S,5S)-2,2,4-Triethyl-5-methyl-1,3-dioxolane: a new volatile released by a triatomine bug.

Adults of the triatomine bug Triatoma brasiliensis release 2,2,4-triethyl-5-methyl-1,3-dioxolane (1) as a mixture of the (4S,5S)- and (4R,5R)-enantiomers in a ratio of 4:1. Among the volatile acetals identified from insects so far, this is the first example resulting from an intermolecular condensation of a carbonyl moiety and a diol substructure.

The use of aggregation signals by Triatoma brasiliensis (Heteroptera: Reduviidae).

Triatoma brasiliensis is considered the main vector of Chagas disease in the semiarid zones of North-eastern Brazil. In this work, we describe the spatial pattern of defecation in T. brasiliensis and the spatial relationship of faeces with the shelters of these bugs. Afterwards, we analyse the attraction response of T. brasiliensis larvae to potential odour cues present in their dry faeces, to substances present in their cuticule (footprints) and to the dry faeces of Triatoma pseudomaculata. We show that faecal spots are deposited in a larger density inside the shelter than in the remaining area available for the bugs. T. brasiliensis larvae were significantly attracted towards their own faeces, and also to those of T. pseudomaculata. In contrast to other triatomine species, footprints did not promote attraction in T. brasiliensis. The potential use of communication signals of T. brasiliensis as tools for helping control this species is discussed.

Dynamics of thermopreference in the Chagas disease vector Panstrongylus megistus (Hemiptera: Reduviidae).

The thermopreference of resting P. megistus (Burmeister, 1834) adults was studied in a temperature gradient. We also determined the thermopreference for oviposition and ecdysis. Thermopreference of resting individuals depended on the feeding state of the insects. Results demonstrated an initial resting preference of approximately 290 degrees C, which gradually changed to 26-27 degrees C with increasing starvation. A daily variation in thermopreference was also observed with this species. The insects showed a daily maximum preference at the beginning of the dark phase, and a minimum preference during the first half of the light phase. Ecdysis took place all along the gradient, but exhibited a maximum frequency at 30 degrees C. Most eggs were found between 25 and 29 degrees C. Results are discussed in relation to the ecology of P. megistus as compared with other related species, and the existence of mechanisms of behavioral thermoregulation in the group.

Aggregation behaviour in Panstrongylus megistus and Triatoma infestans: inter and intraspecific responses.

We tested the aggregation response to inter and intraspecific chemical signals in Panstrongylus megistus and Triatoma infestans. As previously described for T. infestans, larvae of P. megistus significantly aggregated on papers impregnated with their own excrement and on papers marked with cuticular substances deposited on surfaces on which these insects had walked. T. infestans bugs also aggregated on papers impregnated by faeces or by cuticular substances of P. megistus, and P. megistus aggregated on papers contaminated by faeces or by cuticular substances of T. infestans. The response of P. megistus to its cuticular substances was significantly stronger than that to its faeces. The non-specificity of the two signals is discussed in the context of the ecological relationship between both species.

[Microclimatic properties of the Triatoma brasiliensis habitat]. / Aspectos microclimáticos del hábitat de Triatoma brasiliensis.

Vector-borne transmission of Chagas disease in Northeast Brazil is basically by Triatoma brasiliensis. It is thus crucial to determine this species' microclimatic preferences as limiting factors for its distribution and ability to infest domestic environments. We analyze the microclimatic properties of the shelters in which these insects are found in wild, domestic, and peridomiciliary environments in the State of Ceará, at Brazil. We measure temperature and relative humidity (RH) every 15 minutes for 3 days. Thermal variation was greatly dampened inside both domiciliary refuges and the more protected internal places in wild stony sites. For RH, we observed a similar dampening pattern, but mean RH was lower in both domiciliary refuges and wild ones inside stony sites as compared to reference levels in the surrounding environment. The results are discussed with regard to this species' microclimatic preferences in the laboratory and its potential as determinants of its geographical distribution.

Performance of yeast-baited traps with Triatoma sordida, Triatoma brasiliensis, Triatoma pseudomaculata, and Panstrongylus megistus in laboratory assays.

The effectiveness of a trap for triatomines baited with yeast cultures has been previously demonstrated for Triatoma infestans in laboratory assays. We report here results from laboratory assays testing yeast traps for Triatoma sordida, Triatoma brasiliensis, Triatoma pseudomaculata, and Panstrongylus megistus. All assays were conducted in an open experimental arena 100 cm x 100 cm, with two traps placed at opposite sides of the arena. One of the traps contained a yeast culture, and the other trap contained a saccharose solution as a control. Two series of experiments were done, one without a refuge for the insects and one with a refuge. The results obtained clearly demonstrated that the yeast-baited traps were effective in the laboratory in capturing both T. sordida and P. megistus. For T. sordida, yeast-baited traps captured significantly more bugs than did the control traps (t test P value = 0.03). For P. megistus, when a refuge was provided during the assay, yeast-baited traps also captured significantly more bugs than did the control traps (t test P value = 0.006). In the experiments with T. brasiliensis and T. pseudomaculata, both traps captured some insects, but the yeast traps captured many fewer bugs than was true with the T. sordida and P. megistus bugs. These results indicate that, in the laboratory, yeast traps can capture considerable numbers of T. sordida and P. megistus in one night. We discuss the potential use of yeast traps for detecting and capturing both triatomine species.

Three-dimensional cryo-electron microscopy localization of EF2 in the Saccharomyces cerevisiae 80S ribosome at 17.5 A resolution.

Using a sordarin derivative, an antifungal drug, it was possible to determine the structure of a eukaryotic ribosome small middle dotEF2 complex at 17.5 A resolution by three-dimensional (3D) cryo-electron microscopy. EF2 is directly visible in the 3D map and the overall arrangement of the complex from Saccharomyces cerevisiae corresponds to that previously seen in Escherichia coli. However, pronounced differences were found in two prominent regions. First, in the yeast system the interaction between the elongation factor and the stalk region of the large subunit is much more extensive. Secondly, domain IV of EF2 contains additional mass that appears to interact with the head of the 40S subunit and the region of the main bridge of the 60S subunit. The shape and position of domain IV of EF2 suggest that it might interact directly with P-site-bound tRNA.

Sordarin inhibits fungal protein synthesis by blocking translocation differently to fusidic acid.

Sordarin derivatives are selective inhibitors of fungal protein synthesis, which specifically impair elongation factor 2 (EF-2) function. We have studied the effect of sordarin on the ribosome-dependent GTPase activity of EF-2 from Candida albicans in the absence of any other component of the translation system. The effect of sordarin turned out to be dependent both on the ratio of ribosomes to EF-2 and on the nature of the ribosomes. When the amount of EF-2 exceeded that of ribosomes sordarin inhibited the GTPase activity following an inverted bell-shaped dose-response curve, whereas when EF-2 and ribosomes were in equimolar concentrations sordarin yielded a typical sigmoidal dose-dependent inhibition. However, when ricin-treated ribosomes were used, sordarin stimulated the hydrolysis of GTP. These results were compared with those obtained with fusidic acid, showing that both drugs act in a different manner. All these data are consistent with sordarin blocking the elongation cycle at the initial steps of translocation, prior to GTP hydrolysis. In agreement with this conclusion, sordarin prevented the formation of peptidyl-[(3)H]puromycin on polysomes from Candida albicans.

Temperature and relative humidity affect the selection of shelters by Triatoma infestans, vector of Chagas disease.

The preference of Triatoma infestans for shelters at different temperatures or relative humidities (RH) was tested in laboratory assays. The insects preferred refuges at a temperature of 34 degrees C rather than 26 degrees C, and chose to stay in refuges with an RH of 20% rather than 80%. Temperature and RH records made inside and outside experimental chicken-houses under natural climatic conditions showed that such habitats tend to maintain an inner climate favourable to T. infestans. Typical refuges in adobe walls showed strongly damped fluctuations in minimum and maximum temperatures, and delayed changes in these parameters when compared with an external reference. Similarly, the jarilla (Larrea sp.), a plant used for constructing roofing, damps fluctuations in minimum and maximum RH and delays these RH fluctuations when compared to an external reference. We discuss possible effects of environmental factors on the distribution of insects in human dwellings, and analyse the environmental characteristics of normally available refuges in materials used for house building in endemic zones.

Yeast culture volatiles as attractants for Rhodnius prolixus: electroantennogram responses and captures in yeast-baited traps.

Responses to air currents carrying volatiles from yeast cultures were measured by means of electroantennograms (EAGs) in the haematophagous bug Rhodnius prolixus and we tested yeast-baited traps in the laboratory. The volatiles liberated by yeast cultures generated a clear electrophysiological response, much higher than that obtained during stimulation with clean air. The addition of yeast cultures to the traps dramatically increased overnight capture. A modification performed on the traps was effective for this species, as the bugs were immobilised once they fell into the device. Our results demonstrate that yeast culture volatiles are attractive for R. prolixus. The results obtained by means of electroantennogram techniques represent the first electrophysiological evidence of the perception of yeast volatiles by the antennae of a triatomine bug. We discuss the relevance of our results in view of currently used sampling techniques and control strategies.

Triatoma infestans can be captured under natural climatic conditions using yeast-baited traps.

The effectiveness of a trap for triatomines baited with yeast cultures has been previously demonstrated in laboratory assays. We report results from assays testing yeast-traps for Triatoma infestans performed under natural climatic conditions. All assays were conducted at experimental chicken-coops colonised by bugs, situated at an endemic area for Chagas disease in Argentina. Two different models of traps were tested, for use either on the floor, or attached to walls. The results obtained clearly demonstrate that yeast-baited traps are effective for capturing triatomine bugs. Floor traps, when baited, captured significantly more bugs than their controls (t-test, P = 0.0008, k = 10). In addition, wall traps were also more effective, when compared to their controls (t-test, P = 0.011, k = 10). The maximum capture by a single yeast-trap was 39 bugs in one night, while for the same period the maximum capture by a control-trap was two bugs. Traps captured significantly more bugs at nights when maximum temperature was above 18 degrees C (t-test, P = 0.0002). Results indicate that yeast traps are capable of capturing significant numbers of free insects in one night. The potential use of yeast- traps for the detection of triatomine bugs is discussed.

Ribosomal P-protein stalk function is targeted by sordarin antifungals.

Sordarin derivatives are remarkably selective inhibitors of fungal protein synthesis. Available evidence points to a binding site for these inhibitors on elongation factor 2, but high affinity binding requires the presence of ribosomes. The gene mutated in one of the two isolated complementation groups of Saccharomyces cerevisiae mutants resistant to the sordarin derivative GM193663 has now been identified. It is RPP0, encoding the essential protein of the large ribosomal subunit stalk rpP0. Resistant mutants are found to retain most of the binding capacity for the drug, indicating that mutations in rpP0 endow the ribosome with the capacity to perform translation elongation in the presence of the inhibitor. Other proteins of the ribosomal stalk influence the expression of resistance, pointing to a wealth of interactions between stalk components and elongation factors. The involvement of multiple elements of the translation machinery in the mode of action of sordarin antifungals may explain the large selectivity of these compounds, even though the individual target components are highly conserved proteins.

Activity pattern in relation to refuge exploitation and feeding in Triatoma infestans (Hemiptera: Reduviidae).

The pattern of locomotion activity was studied in Triatoma infestans, in relation to the use of an artificial refuge offered to the bugs in an experimental arena. In assays performed with insects that had a post-ecdysis starvation period of 1 week, the activity was low and mainly related to refuge leaving or entering. Insects that had gone through a longer period of starvation (6 weeks) exhibited a high locomotory activity throughout the night. Specific temporal windows were detected for refuge leaving and entering after dusk and before dawn, which were not modified by different levels of starvation of the insects. T. infestans exhibits a higher motivation for feeding during the first night hours, in comparison to that observed at the end of the scotophase. The activity peaks previously reported for T. infestans are therefore related to host and refuge search.

Baker's yeast, an attractant for baiting traps for Chagas' disease vectors.

We tested the attraction of volatile compounds, produced by the aerobic growth of Saccharomyces cerevisiae on saccharose for Triatoma infestans. For these tests, we exploited the behavioural characteristic of these haematophagous insects of dropping when searching for food. In olfactometer assays, yeast cultures activated and attracted bugs as effectively as a mouse. The attraction of the cultures was significantly reduced when the carbon dioxide released was partially eliminated using potassium hydroxide. Yeast cultures were also tested as lures in a novel trap device. A baited device for trapping Chagas' disease vectors using the behavioural peculiarities of T. infestans and this simple attractant is described.