Electrodes were implanted into the rat hippocampus in both hemispheres for increasing periods of up to 60 days, and the effects of trauma and electrical stimulation of enzymes controlling cell metabolism in the region of implantation were examined and assessed in relation to studies on humans. In the unstimulated hippocampus as a control, enzyme changes were mainly confined to a narrow area of tissue damage surrounding the electrode. The enzyme changes in response to trauma varied widely; some enzymes controlling tissue respiration showed early and rapid changes, increasing in hyperactive, swollen glial cells and vascular endothelium and decreasing in nerve cells and neuropile. Acid phosphatase activity also increased rapidly in glial cells; other phosphate-releasing enzymes increased more gradually with time. A turning point in these chages was apparent between 25 and 40 days, followed by a reversion to more normal levels at 60 days. Electrical stimulation of the hippocampus in the contralateral hemisphere produced no detectable enzyme changes from those of the unstimulated hippocampus.
Scrum of hypercholesterolemic rabbits, when pulsated for 72 hours at pressures of 300 mm. Hg/0 mm. Hg with a pulse rate of 80 produced a birefringent deposit in excised pieces of rabbit aortae. Scrum from normal rabbits did not produce this deposit. The active component or components responsible for this deposit are in the |8-lipoprotein fraction of serum. The birefringent material is detectable in serum by this method before lipoid degeneration of the arterial intima becomes apparent in the sacrificed animal.
Sz~mmasy.-A cross-validation of a standard method of measuring strivinginduced stress is described. The sensitivity of the previously reported stress measures, based on heart-rate elevation, is verified. The procedure is demonstrably applicable to more varied populations than those used in the original standardization. While a tendency toward higher over-all heart rates with increased age was observed, the principal specific finding was a positive association of basal serum cholesterol level with post-stress heart rate, independent of age. Individuals with higher serum cholesterol levels showed less complete recovery following stress and higher initial heart rates, but they did not necessarily show a stronger immediate response to the stressors. Psychosomatic implications are discussed.
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