Although glucocorticoids slow the development of most cell types, they have been hypothesized to promote the differentiation of catecholaminergic cells. In the current study, pregnant rats were given dexamethasone on gestational days 17, 18 and 19, and the functional state of noradrenergic synaptic activity was assessed throughout postnatal development by measurements of transmitter levels and turnover, and receptor binding capabilities. Despite growth inhibition caused by dexamethasone, the steroid treatment had little or no effect on transmitter levels or receptor binding and accelerated the maturation of norepinephrine turnover in a regionally selective manner. Effects were most notable in the midbrain and brainstem, where turnover rose to maximum levels 1–2 weeks in advance of controls. Turnover also leveled off prematurely in the dexamethasone group, leading to deficits in the postweaning period and into young adulthood. Although similar patterns were obtained in other, later-developing regions, the effects were less consistent and robust; the smaller effects also extended to dopamine turnover. These results suggest that glucocorticoids have a specific promotional effect on the development of central catecholaminergic activity and that administration of exogenous steroids during critical periods of development can lead to lasting functional abnormalities.

The skeletal mechanics of Astenas forbesii are examined in order to erect a theoretical framework for the evaluation of starfish skeletal systems. Guided by engineering theory, the skeleton is dissected into its functional parts and an approximation made of the stresses sustained by each. All relevant mathematical operations are demonstrated. It is shown that the whole body acts as a unit sustaining compressive forces across its oral surface and tensile stresses across its aboral surface. Two points of maximum stress are identified: the aboral ridge of the ray close to the disk and the inferior transverse amhulacral muscle (ITAM). Structural stability is conferred upon the former by virtue of its position in the body and upon the latter by the inclusion of strong tensile fibres in parallel with the muscle.

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