Locus of control differences in memory recall strategies when confronted with noise.

In some individuals, noise appears to have an adverse effect on memory recall. This decrement may result from a shift in the memory strategy being employed. Studies have shown memory strategies used by persons with an internal locus of control differ from those used by persons with an external locus of control. The present investigation asked subjects who were classified as either internal or external in locus of control to recall words presented under conditions of noise and of quiet. Word recall was aided by providing subjects with potential memory strategies. Each word list included words from meaningful content categories (which favor a semantic strategy) and word pairs that rhymed (which favor a perceptual strategy). Though internal and external subjects did not differ in total words recalled, they did differ in their use of strategies. Whereas internal subjects' strategies were unaffected by noise, external subjects decreased their use of the higher level semantic memory strategy (content categories) and increased their use of lower level perpetual (rhymes) strategy in the noise condition. The results are discussed in terms of a differential arousal hypothesis.

Subcellular localization of the alterations in phosphatidylinositol metabolism following glucose-induced insulin release from rat pancreatic islets.

The subcellular localization of the incorporation of 2-(3H)-myoinositol into lipids has been studied in isolated pancreatic islets of the rat. The recovery of lipid-bound myoinositol increased with time in the nuclear, mitochondrial, microsomal, and secretory granule fractions. The utilization of a filtration technique for the more complete separation of mitochondrial and secretory granule elements permitted us to show that the recovery of lipid-bound 2-(3H)-myoinositol increased most rapidly in the secretory granule fraction. A 30-minute exposure of prelabeled islets to a stimulatory concentration of D-glucose (3.0 mg./ml.) resulted in a statistically significant decrease in the amount of lipid-bound 2-(3H)-myoinositol that was recovered from the secretory granule fraction (p less than 0.001). In contrast, exposure of islets to the elevated glucose concentration had no statistically significant effect on the recovery of lipid-bound radioactivity from other subcellular fractions. Since the majority of lipid-bound radioactivity associated with the secretory granule fraction could be recovered with the presumptive secretory granule membranes, these data suggest that the hydrolysis of phosphatidylinositol that accompanies glucose-induced insulin secretion from the rat pancreatic islet may be localized to the beta granule and, in particular, to its limiting membrane.

Extraction and characterization of a thyrotropic material from the human placenta.

A material with thyrotropic activity was extracted from fresh human placentas. After chromatography of the extract on carboxymethyl cellulose, thyroid-stimulating activity ranged from 0.12 to 1.06 mU of thyroid-stimulating hormone (TSH) per mg of protein in bioassays of eight preparations. The amount of TSH per placenta varied from 113 to 2200 mU and approximated the content of the pituitary gland. Additional purification by gel filtration on Sephadex G-100 gave a maximum activity of 8 mU/mg. The most active portion was eluted in the same position as (125)I-labeled bovine or human TSH, a fact suggesting that the molecular size of this thyrotropic substance was similar to that of pituitary TSH. Another placental fraction with weaker activity was eluted earlier indicating that the placental material was heterogeneous. In the McKenzie mouse bioassy, the response of the placental thyrotropin paralleled that of the beef TSH standard. There was no long-acting thyroid stimulator effect. Antibodies to both human and bovine pituitary TSH neutralized the biologic activity of the placental TSH. Placental thyrotropin cross-reacted very weakly in a sensitive radioimmunoassay for human pituitary TSH; it cross-reacted completely in a radioimmunoassay for bovine pituitary TSH, and this assay was used for following the purification. The role of this thyrotropic material as a possible cause of thyroid hypertrophy and hyperfunction in pregnancy and in patients with trophoblastic tumors remains to be investigated.