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Biomedical subjects

D M Stoddart

Publications and source records attributed to D M Stoddart.

7 recordsLinked to original sources
PubMed1995

Towards a sociobiological model of depression. A marsupial model (Petaurus breviceps).

BACKGROUND: This is a sociobiological approach to depression using hierarchy and its hypothesised relevance to self-esteem in the marsupial sugar glider (Petaurus breviceps). METHOD: Differential access to resources between the dominant and submissive animal is measured by observation in four stable colonies. The dominant animals from two of these colonies are then introduced into the other two, resulting in the transferred former dominants becoming subordinate. Behavioural and biochemical measures relevant to depression and involving access to resources are then repeated. These measures include eating, drinking, social and sexual access, motility, grooming and biochemical estimates of cortisol and testosterone. RESULTS: Subordinate animals have significantly less access to resources, both in the stable colony and when the formerly dominant animals become subordinate. CONCLUSIONS: A sociobiological approach using a hierarchy model equating resource-holding potential with self-esteem, exemplified by this study, may provide new concepts and insights into the phenomenology and pathophysiology of depression. It allows comparisons to be made between animal behaviour and cognition: the lack of such has been a major difficulty in animal studies hitherto. The findings are possibly more relevant to dysthymia than to affective disorder and imply a relationship between low resource-holding potential in sub-human animals as a phylogenetic antecedent of some of the cognitive and affective aspects of depression in man.

Animals↗
PubMed1994

Behavioral and endocrinological correlates of social status in the male sugar glider (Petaurus breviceps Marsupialia: Petauridae).

Socially dominant male sugar gliders are heavier than socially subordinate males, have higher plasma testosterone and lower cortisol concentrations, win more social encounters, scan the arena more, scent-mark more, and are more active and move more quickly, even though they spend more time in the colony nesting box. When they are transferred into a foreign stable colony there is an impressive reversal of behavioral measures and a concomitant decrease in concentration of plasma testosterone and rise in cortisol that is apparent over the first 3 weeks of observation.

Animals↗
PubMed1992

Seasonal changes in plasma androgens, glucocorticoids and glucocorticoid-binding proteins in the marsupial sugar glider Petaurus breviceps.

An investigation spanning two breeding seasons was carried out to examine endocrine changes associated with reproduction in a wild population of the marsupial sugar glider Petaurus breviceps, a small arboreal gliding possum. Using techniques of equilibrium dialysis and polyacrylamide gel electrophoresis at steady-state conditions, a high-affinity, low-capacity glucocorticoid-binding protein was demonstrated in the plasma of Petaurus breviceps. Equilibrium dialysis at 36 degrees C using cortisol gave a high-affinity binding constant of 95 +/- 5.2 litres/mumol for a presumed corticosteroid-binding globulin (CBG) while the binding constant for the cortisol-albumin interaction was 3.5 +/- 0.4 litres/mmol. There was no difference between the sexes in the affinity of binding of cortisol to CBG; however, the cortisol-binding capacity underwent seasonal variation in both sexes. Progesterone was bound strongly to the presumed CBG while neither oestradiol nor aldosterone appeared to be bound with high affinity to P. breviceps plasma. In the males, peaks in the plasma concentration of testosterone coincided with the July-September breeding season in both years. A significant inverse relationship was shown to exist between the plasma testosterone concentration and the CBG-binding capacity. In both sexes an increase occurred in the plasma concentration of free cortisol during the first breeding season, a pattern which was not repeated in the subsequent breeding season, possibly due to a lower population density in that year.

Androgens↗
PubMed1990

Metabolic effects of cortisol, ACTH, adrenalin and insulin in the marsupial sugar glider, Petaurus breviceps.

The effects of cortisol, ACTH, adrenalin and insulin on indices of carbohydrate, fat and protein metabolism were investigated in the conscious marsupial sugar glider Petaurus breviceps. Short-term i.v. infusion of cortisol at dose rates of 0.02, 0.2 and 1.0 mg/kg per h caused the plasma glucose concentration to rise sharply from the normal range of 3.3-4.4 to 8.1-8.7 mmol/l at the end of the infusion period without significant alteration in plasma free fatty acid (FFA), amino acid or urea concentrations. Infusions of ACTH at dose rates of 0.02, 0.06 and 0.45 IU/kg per h caused a similar rise in plasma glucose concentration; however, this was now accompanied by an elevation in plasma FFA concentration, but again without significant changes in either plasma amino acid or urea concentrations. Infusion of adrenalin at 10 micrograms/kg per h caused an increase in the plasma concentrations of both glucose and FFA. Intravenous injections of 0.15 IU insulin/kg caused a rapid and marked decrease in the plasma glucose concentration within 30 min and an increase in the plasma free cortisol concentration. Associated with this change was a marked rise in the plasma concentration of both FFA and free cortisol. The rise in free cortisol was, however, significantly reduced by infusion of glucose. Pretreatment with five daily i.m. injections of 1 mg cortisol acetate/kg, which produced an increase in plasma free cortisol concentration to near the maximum of the physiological range, caused a marked reduction in insulin sensitivity. Cortisol pretreatment caused an increase in the plasma FFA and amino acid concentrations. Petaurus breviceps is highly sensitive to the metabolic effects of glucocorticoids and is similar in this respect to the brush-tailed possum Trichosurus vulpecula. The interactive effects between insulin and glucocorticoids on carbohydrate, fat and protein metabolism in Petaurus breviceps are similar to those shown by Trichosurus vulpecula and some eutherian mammals but contrast with the pattern described for two macropodid marsupials, the red kangaroo Macropus rufus and the quokka Setonix brachyurus.

Adrenocorticotropic Hormone↗
PubMed1979

External nares and olfactory perception.

Lower vertebrates have more widely separated external nares than higher forms and are thus better adapted to utilize olfactory tropotaxis, or stereolfaction, than higher vertebrates which, on account of their flexible necks, must utilize klinotaxis. Snakes and tubenosed bats break the rule on account of their specialized life styles.

Animals↗