 570  543. The present findings make it clear that imipramine does in fact favorably influence the activity of the brain system associated with reward, as we expected an antidepressant would. However, it seems to act in some indirect augmenting capacity (since amphetamine is required for the action) rather than through direct simulation. This accords with the suggestion of Sigg (2) that imipramine exerts a «sensitizing» influence on central adrener-gic synapses. All our data can be viewed as supporting this notion. 544. It thus seems likely for man and smaller mammals that exercise is not a good source of metabolic heat for maintaining body temperature because of the great increase in heat loss (largely convective loss) involved in the exercise. Shivering is more efficient because heat loss can be minimized by decreasing surface area (curling up) and maintaining the isulation due to fur and visoconstriction. Specific dynamic action of foods should also be a good source of heat, providing it is not associated with a marked cutaneous vasodilatation and thus an excessive increase in heat loss. 545. Radio-command midcourse guidance is regarded as having great potential for future lunar and interplanetary missions. It is suitable for ensuring impact on a small preselected area of the surface of the Moon, for guidance prior to the creation of a lunar satellite and for sending a recoverable space probe round the Moon and back to Earth. Furthermore, provided the measure of the Astronomical Unit is improved, such quidance will ensure approaches of 10.000 to 20.000 miles of the planets Mars and Venus. 546. For reasons discussed in the text, this «free» ferritin, seen only at very long intervals after ferritin administration, is thought to be a newly synthesized or endogenous protein rather than the exogenous tracer. Magnification 80,000. 547. Rabbits made granulocytopenic with nitrogen mustard have been shown to generate serum endogenous pyrogen when given a fever-producing dose of bacterial endotoxin. This finding is in accord with the hypothesis that endogenous pyrogen plays a central role in the pathogenesis of endotoxin fever. 548. In the work now to be described, it was observed that a single dose of 7,12-dimethylbenz (a) anthracene caused extraordinary changes in the rat consisting of adrenal apoplexy and massive necrosis in the two inner zones of the cortex while other regions of the adrenal glands were uninjured. In addition to the selectivity of the anatomic site of damage, there is high specificity of the molecular structure of the polynuclear aromatic hydrocarbon exerting this adrenocorticolytic effect. 570 |
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