Developmental profiles of GFAP-positive astrocytes in sheep cerebellum

Astroglial account for the largest glial population in the brain and play a variety of vital functions in the development of the central nervous system (CNS). An immunohistochemical study was performed in 19 ovine foetuses ranging from 2 to 5 months of gestation, one newborn lamb and three adult sheep. Using the anit-glial fibrillary acidic protein (GFAP) marker, several variations were found in the degree of GFAP positive (GFAP+) astrocyte distribution between the different zones in the cerebellum of sheep during brain development. Our study indicates that the first appearance of astrocytes from restricted zones in the cerebellum occurs around the eighth week of gestation. Bergmann cells were found to be present from around the 15th week of gestation onwards. Our findings suggest that the maturation of astrocytes begins in the caudal parts of the cerebellum, developing from their initial ventral regions to spread first to dorsal regions radially within the white matter, then followed by the more rostral parts of the cerebellum. Astrocytes were also found to proliferate in the vermis before appearing in the cerebellar hemispheres.     

Rein tension acceptance in young horses in a voluntary test situation

Reasons for performing the study: During riding, horses are frequently exposed to pressure from the rider, e.g. through the bit and reins, but few studies have investigated at which point rein tension becomes uncomfortable for the horse. Objectives: To investigate how much rein tension young inexperienced horses are willing to accept in order to obtain a food reward; whether the tension acceptance changes during 3 consecutive test days; and whether rein tension correlates with the expression of conflict behaviour and heart rate. Hypotheses: Pressure‐naïve horses will apply only little rein tension in the first voluntary trial, but their acceptance will gradually increase. High levels of rein tension will lead to expression of conflict behaviour and increases in heart rate. Methods: Fifteen 2‐year‐old, bridle‐naïve mares were encouraged to stretch their head forward (across a 0.95 m high metal bar) to obtain a food reward in a voluntary test situation. On each test day, each horse was exposed to 2 control sessions (loose reins), an intermediate and a short rein session (1 min/session). Rein tension, heart rate and behaviour were recorded. Results: The horses applied significantly more tension on the first day (mean rein tension: 10.2 N), compared to the second and third test day (Day 2: 6.0 and Day 3: 5.7 N). The horses showed significantly more conflict behaviour in the short rein treatment. There was no treatment effect on heart rate. Conclusions and potential relevance: The horses applied the highest rein tension on the first day, and apparently learned to avoid the tension, rather than habituate to it. Rein tension correlated with expression of conflict behaviour, indicating that the horses found the tension aversive. Further studies should focus on the correlation between rein tension and conflict behaviour in ridden horses.     

Current status of medical and veterinary entomology in France: endangered discipline or promising science?

Following alarming statements (French Senate, Académie des Sciences) on the present situation concerning entomology and systematics in France, the Conseil Général Vétérinaire designated one of us (D.C.) to carry out a survey on the status of medical and veterinary entomology (MVE) with respect to research orientations and university curricula. Around 100 participants, including scientists, teachers and several directors of research and educational bodies, were interviewed and filled in questionnaires for this survey. On the basis of the results, it was concluded that the deterioration of MVE in France is associated with: (1) the hasty reorganisation of training and research in the life sciences, leading to the disappearance of several disciplines. Hence, the postgraduate DEA degree in entomology was eliminated, and even the name 'entomology' no longer appears in teaching programmes or on research contracts; (2) France's withdrawal from action research programmes in developing countries. Although these programmes were efficient in controlling outbreaks of major endemic diseases, integrated pest and vector management programmes have been replaced by basic health care ('Health for everyone in 2000') and vaccination programmes; (3) the general shift from field to laboratory research, focused mainly on molecular mechanisms. The survey results confirmed generally acknowledged trends concerning many points and highlighted several specific problems, such as the disappearance of systematics experts. Several potential solutions are proposed.     

Using ecological niche modelling to infer past, present and future environmental suitability for Leiopelma hochstetteri, an endangered New Zealand native frog

Leiopelma hochstetteri is an endangered New Zealand frog now confined to isolated populations scattered across the North Island. A better understanding of its past, current and predicted future environmental suitability will contribute to its conservation which is in jeopardy due to human activities, feral predators, disease and climate change. Here we use ecological niche modelling with all known occurrence data (N = 1708) and six determinant environmental variables to elucidate current, pre-human and future environmental suitability of this species. Comparison among independent runs, subfossil records and a clamping method allow validation of models. Many areas identified as currently suitable do not host any known populations. This apparent discrepancy could be explained by several non exclusive hypotheses: the areas have not been adequately surveyed and undiscovered populations still remain, the model is over simplistic; the species’ sensitivity to fragmentation and small population size; biotic interactions; historical events. An additional outcome is that apparently suitable, but frog-less areas could be targeted for future translocations. Surprisingly, pre-human conditions do not differ markedly highlighting the possibility that the range of the species was broadly fragmented before human arrival. Nevertheless, some populations, particularly on the west of the North Island may have disappeared as a result of human mediated habitat modification. Future conditions are marked with higher temperatures, which are predicted to be favourable to the species. However, such virtual gain in suitable range will probably not benefit the species given the highly fragmented nature of existing habitat and the low dispersal ability of this species.     

Pharmacokinetics of low-dose methotrexate in horses

This study aimed to investigate both the pharmacokinetic behavior and tolerance of methotrexate (MTX) in horses to design a specific dosing regimen as a new immunomodulatory drug for long-term treatment. To determine the primary plasma pharmacokinetic variables after single intravenous, subcutaneous or oral administration, six horses were administered 0.3 mg/kg MTX in a crossover design study. After a 10-week washout, MTX was administered subcutaneously to three of the six previously treated horses at a dose of 0.3 mg/kg once per week for 3 months. In both studies, MTX and metabolite concentrations were measured using LC-MS/MS. The absolute bioavailability of MTX was 73% following subcutaneous administration but less than 1% following oral administration. The plasma clearance was 1.54 ml min⁻¹ kg⁻¹ (extraction ratio = 2%). After 24 hr, plasma concentrations were below the LOQ. No adverse effects were noted except for a moderate reversible elevation in liver enzymes (GLDH). With regards to the main metabolites of MTX, very low concentrations of 7-hydroxy-MTX were found, whereas polyglutamated forms (mainly short chains) were found in red blood cells. A subcutaneous dose of 0.2 mg kg⁻¹ week⁻¹ may be safe and relevant in horses, although this has yet to be clinically confirmed.