Mogens Bildsøe

Development of Type 1 Diabetes in Wild Bank Voles Associated With Islet Autoantibodies and the Novel Ljungan Virus

Wild bank voles (Clethrionomys glareolus) may develop diabetes in laboratory captivity. The aim of this study was to test whether bank voles develop type 1 diabetes in association with Ljungan virus. Two groups of bank voles were analyzed for diabetes, pancreas histology, autoantibodies to glutamic acid decarboxylase (GAD65), IA-2, and insulin by standardized radioligand-binding assays as well as antibodies to in vitro transcribed and translated Ljungan virus antigens. Group A represented 101 trapped bank voles, which were screened for diabetes when euthanized within 24 hours of capture. Group B represented 67 bank voles, which were trapped and kept in the laboratory for 1 month before being euthanized. Group A bank voles did not have diabetes. Bank voles in group B (22/67; 33%) developed diabetes due to specific lysis of pancreatic islet beta cells. Compared to nondiabetic group B bank voles, diabetic animals had increased levels of GAD65 (P < .0001), IA-2 (P < .0001), and insulin (P = .03) autoantibodies. Affected islets stained positive for Ljungan virus, a novel picorna virus isolated from bank voles. Ljungan virus inoculation of nondiabetic wild bank voles induced beta-cell lysis. Compared to group A bank voles, Ljungan virus antibodies were increased in both nondiabetic (P < .0001) and diabetic (P = .0015) group B bank voles. Levels of Ljungan virus antibodies were also increased in young age at onset of newly diagnosed type 1 diabetes in children (P < .01). These findings support the hypothesis that the development of type 1 diabetes in captured wild bank voles is associated with Ljungan virus. It is speculated that bank voles may have a possible zoonotic role as a reservoir and vector for virus that may contribute to the incidence of type 1 diabetes in humans.

Effects of immobility stress and food restriction on stereotypies in low and high stereotyping female ranch mink.

Two experiments were conducted to examine the effects of repeated immobilisations and food restriction on normal activity and stereotypies in low and high stereotyping female ranch mink. Repeated immobilisations had immediate inhibitory effects on normal activity and stereotypies in both groups, whereas food restriction had the opposite immediate effects. Subsequent to both immobilisations and food restriction, stereotypies were increased, whereas normal activities returned to pre-experimental levels. Repeated immobilisations were followed by increases in cortisol levels in both low and high stereotyping females. High stereotyping females had lower baseline cortisol levels than low stereotypers but tended to show higher cortisol responses to immobilisations. These results indicate that stressful experiences may affect stereotypies, but that the direction of the changes depends on type of stressor as well as the duration of exposure to the stressor. It is moreover suggested that stereotypies can be emancipated.

Effects of postnatal stress on the development of type 1 diabetes in bank voles (Clethrionomys glareolus).

Wild bank voles (Clethrionomys glareolus) kept in the laboratory under barren housing conditions develop high incidences of type 1 diabetes mellitus due to beta cell– specific lysis in association with the appearance of GAD65, IA-2, and insulin autoantibodies. Wild-caught and immediately analyzed voles show no histological signs of diabetes, and the disease may therefore be induced by circumstances related to the housing of the animals in captivity. We tested the possibility that postnatal stress by either maternal separation or water immersion at different intervals would induce diabetes in adult bank voles. We found that low-frequent stress during the first 21 days of life increases, whereas high-frequent stress markedly reduces, the incidence of type 1 diabetes in adulthood. These results differentiate the role of early-experienced stress on subsequent type 1 diabetes development and emphasize that the bank vole may serve as a useful new animal model for the disease.

Foraging behaviour of cormorants Phalacrocorax carbo in pound nets in Denmark: the use of barrel nets to reduce predation

Yields in pound nets are in particular damaged or reduced by cormorant Phalacrocorax carbo predation. In this study we examined the effect on predation in pound nets by mounting barrel nets vertically under the water in the pot in order to obstruct cormorants during their hunt. To keep control of the content of fish we used an experimental pot with a closed throat. The pot was stocked repeatedly with rainbow trout Oncorhyncus mykiss and its content of fish was thereby maintained at between 10 and 100 individuals during all periods of data collection. Video recordings, both above and under water, were carried out during May - August 1995 under various experimental conditions. We tested five different barrel net arrangements including a control situation without barrel net. Two bird categories were defined a posteriori: those that caught one or more fish during their visit to the pot (successful birds) and those that failed to catch a fish (unsuccessful birds). Successful and unsuccessful birds differed in a number of ways. Successful cormorants stayed longer in the pot, performed more dives, and spent more time diving and shorter time on the surface. When barrel nets were present, fewer cormorants of both categories visited the pot. Furthermore, the barrel nets affected successful birds by increasing the number of dives required to catch their first fish, reduced the time that both successful and unsuccessful birds remained in the pot, and reduced the number of dives performed by unsuccessful birds. Therefore, it seems that barrel nets may have a potential as a predation reducing device in pound net fishery. Introducing the use of barrel nets in pound net fisheries may force cormorants to hunt in free waters, possibly with reduced foraging success. This may eventually lead to a reduction in the cormorant population which will make it better fit the natural carrying capacity of the environment.