Handheld computers in veterinary medical education: a view from human medical education

Handheld computers are widely used in clinical practice, and their use in both human medical education and veterinary medical education is increasing, especially, for the former, in activities involving point-of-care access. This article references the insights that can be obtained from the usage and activities that are gaining a strong foothold in human medical education. Handheld computer technology gives students access to a large and changing knowledge base for clinical practice, especially when they are geographically dispersed. Differences in use between education and practice largely relate to the importance clinicians place on patient information. Student use focuses on progress mapping and ready access to clinical reference material. Suggestions are made for future use in medical education.     

Transstadial and intrastadial experimental transmission of Ehrlichia canis by male Rhipicephalus sanguineus

The acquisition and transmission of rickettsial pathogens by different tick developmental stages has important epidemiological implications. The purpose of this study was to determine if male Rhipicephalus sanguineus can experimentally acquire and transmit Ehrlichia canis in the absence of female ticks. Two trials were performed where nymphal and male R. sanguineus were simultaneously acquisition fed on the same infected donor hosts, and transstadially or intrastadially exposed male ticks were fed on separate pathogen-free dogs as a test for transmission. A single-step p30-based PCR assay was used to test canine and tick hosts for E. canis infections before and after tick feeding. E. canis was detected after either intrastadial or transstadial passage in male ticks, the organism remained detectable in both tick groups after transmission feeding, and both tick groups transmitted the rickettsia to susceptible dogs. Infection of dogs via tick feeding resulted in milder clinical signs and lower antibody titers than intravenous inoculation of carrier blood, but further investigation is needed to understand the mechanisms responsible for this observation. These results demonstrate that male R. sanguineus can take multiple feedings, and that they can both acquire and transmit E. canis in the absence of female ticks. This tick development stage could be important in transmission of E. canis, and perhaps related pathogens, between vertebrate hosts under natural and experimental conditions.     

Dermatophilus congolensis bovine dermatophilosis in the French West Indies. III. A comparison between infected and non-infected cattle

The determination of the distinctive features between infected and uninfected cattle by Dermatophilus has been performed among 93 bovine stock in La Martinique, and 120 in La Guadeloupe and Saint-Martin Islands. Nearly half of the herds had been or were infected. Morbidity rates reach 33 per cent in La Martinique and 29 per cent in La Guadeloupe with a mortality ratio of 15 per cent and 5 per cent respectively. No frequency difference could be observed with respect to the season or the geographical area. Similarly, differences are little or nil as regards animal exposure toward aggressive factors such as sun, soil moisture, thorns, etc. On the other hand, the presence of Amblyomma variegatum is a determining factor considering the prevailing situation in La Martinique, where all breeds of cattle are sensitive to the disease. In this case, 63 per cent of the tick infested cattle develops dermatophilosis versus 2.5 per cent for the still uninfected animals. Conversely, in La Guadeloupe were Creole zebus are highly resistant (as a consequence of their natural selection), only 27 per cent of the infected stock suffers from this illness. In these two islands, regular dipping measures have proved to be beneficial in that it reduces the disease frequency. The study also reveals an underlying typology of the various rearing systems, thus allowing their classification as for their behaviour and response when meeting illness. In La Martinique, whatever they may be, quite none of them is infected in the tick free area. In the tick infested zones, the traditional small breeders rearing a sensitive cattle and who do not care with prophylactic rules, are mostly stricken, while more structured ones have succeeded in controlling the disease, owning to some appropriate measures together with a fair animal management. On the other hand, in La Guadeloupe where this tick is cosmopolitan, the small breeders who run a resistant Creole cattle, are not concerned, despite a rudimentary prophylactic behaviour. Conversely, the intensive rearing system, based upon improved imported breeds, meets great difficulties to master the infection.     

Prediction of field atrazine persistence in an allophanic soil with Opus2

A modified version of the model Opus was applied to measurements of soil water dynamics and atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) persistence in a Bruntwood silt loam soil (Haplic Andosol, FAO system) in Hamilton, New Zealand. The modified model, Opus2, is briefly described and parameter estimation for the simulations is discussed. Soil water dynamics were more accurately described by applying measured soil hydraulic properties than by estimating them using pedotransfer functions. A parameter sensitivity analysis revealed that degradation was the most relevant process in simulating pesticide behaviour by Opus2. The Arrhenius equation incorporated in Opus2 did not correctly describe the effect of temperature on degradation rates obtained at 10, 20 and 30 degrees C. However, as the Arrhenius coefficient is a very sensitive parameter and soil temperature variation was relatively narrow in the field, the Arrhenius coefficient was approximated from the laboratory study. The simulation results obtained were superior to modelling at constant temperature. Field measured persistence of atrazine in the topsoil was underpredicted using the half-life determined in the laboratory at 10 degrees C. Modelling with a lag phase followed by accelerated degradation by use of a sigmoidal degradation equation in Opus2 significantly improved the modelling results. Nevertheless, degradation processes in the laboratory under controlled conditions did not accurately represent field dissipation, however well the laboratory degradation data could be described by simple kinetic equations. The study indicates the importance of improving field techniques for measuring degradation, and developing laboratory protocols that yield degradation data that are more representative of pesticide dynamics in field soils.     

Ischemia opens neuronal gap junction hemichannels

Neuronal excitotoxicity during stroke is caused by activation of unidentified large-conductance channels, leading to swelling and calcium dysregulation. We show that ischemic-like conditions [O(2)/glucose deprivation (OGD)] open hemichannels, or half gap junctions, in neurons. Hemichannel opening was indicated by a large linear current and flux across the membrane of small fluorescent molecules. Single-channel openings of hemichannels (530 picosiemens) were observed in OGD. Both the current and dye flux were blocked by inhibitors of hemichannels. Therefore, hemichannel opening contributes to the profound ionic dysregulation during stroke and may be a ubiquitous component of ischemic neuronal death.     

A cortical region consisting entirely of face-selective cells

Face perception is a skill crucial to primates. In both humans and macaque monkeys, functional magnetic resonance imaging (fMRI) reveals a system of cortical regions that show increased blood flow when the subject views images of faces, compared with images of objects. However, the stimulus selectivity of single neurons within these fMRI-identified regions has not been studied. We used fMRI to identify and target the largest face-selective region in two macaques for single-unit recording. Almost all (97%) of the visually responsive neurons in this region were strongly face selective, indicating that a dedicated cortical area exists to support face processing in the macaque.