Knud Erik Heller

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.

Intermittent stress in pigs : Effects on behavior, pituitary-adrenocortical axis, growth, and gastric ulceration

Ninety-six pigs, half females and half castrated males from 12 litters, were housed in 24 groups of four litter mates. From an age of 115 days half of the groups were subjected to chronic stress for 33 days consisting of a schedule of unpredictable, inescapable electroshocks, and half served as controls. Behavior and performance were measured on all animals in the group, hormone data on one female in each group, and data on ulceration on the castrates. Behaviorally, the pigs did not habituate to 31 days of stress treatment. One to 2 days of stress treatment produced a behavioral activation that after 9 to 10 days was restricted to the time period of potential stress treatment. After 30 to 31 days it was replaced by passive behavior. In the beginning as well as after 30 to 31 days of intermittent stress, time spent sitting was increased. In addition, 6 days of intermittent stress reduced the baseline mean of plasma ACTH. After 33 days of stress the baseline mean of plasma ACTH was normalized, but the time course of diurnal secretion of ACTH was shifted. No effects of the chronic intermittent stress on basic levels of plasma cortisol, performance, or gastric ulceration were evident. In conclusion, the effect of intermittent stress depends on the number of days of intermittent stress treatment and it does not inevitably include changes in the basic levels of cortisol. Thus, assessment of stress must be based on a wide range of variables describing the process.

Indication of a genetic basis of stereotypies in laboratory-bred bank voles (Clethrionomys glareolus).

The development of stereotypies was studied in two successive laboratory-bred generations of bank voles representing F1 (n=248) and F2 (n=270) of an originally wild caught stock. It was shown that the propensity to develop stereotypies under barren housing conditions strongly relates to the same propensity of the parents. Stereotypies were approximately seven times more frequent in the offspring of stereotyping parents than in the offspring of permanent non-stereotypers. This held true even when only one of the parents was stereotyper. The paternal and maternal contributions to stereotypies in the offspring appeared to be equal. Males showing stereotypies but prevented from any physical contact with the offspring were as potent as stereotyping females in producing stereotyping offspring. Moreover, the specific type of stereotypy appearing in the offspring after isolation was very much related to the type of stereotypy developed in the mothers. We found no support for the possible importance of social facilitation from littermates, in that the development of stereotypies was independent of the length of time the voles were kept socially with littermates before isolation. We suggest that the possible genetic basis of individual differences in the propensity to develop stereotypies in captivity may result from differences in genetic predispositions and their interactions with discrete frustrating stimuli early in life and/or to genetically different predispositions to cope with frustrating experiences later in life.

Development of stereotypies and polydipsia in wild caught bank voles (Clethrionomys glareolus) and their laboratory-bred offspring.: Is polydipsia a symptom of diabetes mellitus?

The development of stereotypies and polydipsia was studied in wild caught bank voles (P: n=92) and their laboratory-bred offspring (F1: n=248). All animals were kept isolated in barren cages in the laboratory. In the P generation, no individuals developed stereotypies, but 22% developed polydipsia (>21 ml/day water intake against normally 10 ml/day). Polydipsia was more frequent among males (34%) than females (13%). In F1, 30% developed locomotor stereotypies alone, 21% showed polydipsia alone, and, additionally, 7% developed both stereotypies and polydipsia. Fewer males than females developed stereotypies (23% vs. 38%), whereas polydipsia was more frequent in males than in females (30% vs. 11%). The occurrence and distribution of polydipsia among sexes were the same in F1 and P. The distribution of different types of stereotypies in stereotyping voles were backward somersaulting (BS, 80%), high-speed jumping (JUMP, 29%), pacing following a fixed route (PF, 12%) and windscreen wiper movement (WIN, 5%). Some individuals (10%) showed two or more different types of stereotypies. The average age for developing stereotypies was 96 days while polydipsia was registered at the age of 63 days in both sexes. Voles showing both polydipsia and stereotypies developed polydipsia later (79 days) than polydipsic voles not showing stereotypies. This difference was especially pronounced in stereotyping females in which the occurrence of polydipsia was postponed to the age of 114 days. Polydipsic voles were tested positive for glucosuria indicating that polydipsia could be a symptom of diabetes mellitus. It is suggested that the development of stereotypies and polydipsia among bank voles in the laboratory are the results of frustration and prolonged stress. Stereotypies seem to depend on frustrative experiences early in life, while polydipsia may be related to diabetes mellitus caused by the experience of prolonged stress. Moreover, circumstances related to the development of stereotypies may be adaptive by reducing the risks of prolonged stress, including the development of fatal polydipsia.

Effect of subordinance, lack of social hierarchy, and restricted feeding on murine survival and virus leukemia

When caged in groups of three and fed ad libitum, dominant male mice survived longer than subordinate group members which again lived longer than males caged in groups of nine, among whom no rank order was established. In groups of nine the social structure was not affected when the food supply was reduced to the lowest level not affecting survival, but in groups of three, food reduction made the survival of both dominant and subordinate animals drop to a level matching that of groups of nine. After challenge with a small dose of Moloney virus, leukemia developed among ad libitum fed subordinate mice in groups of three and members of groups of nine, but not among the dominant animals. Food restriction enhanced the leukemia incidence, but dominant animals continued to go free. We conclude that subordinance and also lack of social hierarchy result in a higher incidence of virus induced leukemia, that severe food restriction does the same, and that the effect of social order on leukemia development prevails even under feeding conditions that nearly abolish group-related differences in survival.

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.

The involvement of dopamine (DA) and serotonin (5-HT) in stress-induced stereotypies in bank voles (Clethrionomys glareolus).

In order to clarify the dependency of stress-induced stereotypies on dopamine (DA) and serotonin (5-HT) functioning, undisturbed and acutely stressed stereotyping bank voles were treated during 3 weeks with the commonly used human atypical neurolepticum clozapine and the SSRI antidepressant citalopram. Clozapine blocks DA receptors (D sub (4)) and acts as a partial 5-HT antagonist (5-HT sub (2) receptors), while citalopram increases 5-HT transmitter activity. Levels of stereotypies were quantified under undisturbed conditions during the treatment period and immediately after the acute stress of handling and injections. It was demonstrated that stereotypies are markedly increased after acute stress and that citalopram effectively mitigates this stress effect. Stereotypies under undisturbed conditions were left unaffected by both clozapine and citalopram treatments.It is suggested that stress-induced increases in stereotypies are more dependent on 5-HT than DA functioning.

Stimulation of serotonin (5-HT) activity reduces spontaneous stereotypies in female but not in male bank voles (Clethrionomys glareolus) Stereotyping female voles as a new animal model for human anxiety and mood disorders?

Abstract Spontaneously stereotyping female and male bank voles were injected daily (except on days assigned for monitoring behaviour) during 3 weeks with placebo, the neurolepticum clozapine or the SSRI antidepressant citalopram. Clozapine blocks dopamine (DA) receptors and acts as a partial serotonin (5-HT) antagonist, while citalopram is a specific 5-HT agonist. Stereotypies in both sexes were left unaffected by clozapine treatment, but citalopram markedly reduced stereotypy levels in females. Animal stereotypies have been widely used in models to provide insight into the underlying pathophysiological processes in human mental disturbances. The present findings highlight the importance of examining sex as a significant variable in evaluating responses to pharmacotherapy, and the demonstrated effect of citalopram indicates that stereotyping female bank voles may be useful in new animal models for human anxiety and mood disorders.

Intermittent Stress in Pigs: Behavioural and Pituitary-Adrenocortical Reactivity

Abstract Ninetysix pigs, half females and half castrated males from 12 litters, were housed in 24 groups of 4 litter mates (2 females, 2 castrates). The pigs were weaned at 4 weeks of age and from the age of 115 days half of the groups were subjected to a schedule of unpredictable, inescapable electroshocks for 33 days, and half served as control. The adrenocortical reactivity to ACTH stimulation and to an emotional stressor (the procedure associated with initiation of blood collection) was measured in females, whereas the behavioural and pituitary-adrenocortical reactivity to an open field test was measured in castrates, as was the behavioural reactivity in a social test. Intermittent stress increased adrenocortical reactivity to ACTH stimulation significantly. This effect was present within the first week of intermittent stress (p < 0.06), but no difference was found after 4–5 weeks of stress. In contrast, the adrenocortical reactivity to additional emotional stressors was unaffected by stress after one...