Common Response Mechanism Research Articles

Yeast peptide pheromones, a-factor and α-factor, activate a common response mechanism in their target cells

We show that in yeast the cell type specificity of pheromone response is determined solely by the species of receptor that a cell synthesizes. The two receptor-pheromone interactions are functionally interchangeable and involve the creation of a common intracellular signal. In particular, we find that provision of a-factor receptor or α-factor receptor in matα1 mutants, which normally do not express either receptor or any other a- or α-specific products, allows response to the appropriate pheromone. Moreover, provision of a-factor receptor in a cells lacking α-factor receptor restores mating competence to those cells. Finally, an aspect of pheromone response that is normally unique to a-factor action on α cells — increased transcription from the α-specific STE3 gene — can also be observed following α-factor treatment of pseudo-a cells (matα2 ste3 ste13), special mutants that respond to α-factor and also have an active STE3 promoter.

Changes in Somatostatin Concentration in Pancreas and Other Tissues of Streptozotocin Diabetic Rats*

Changes in immunoreactive somatostatin were examined in islets, whole pancreas, stomach, and hypothalamus of streptozotocin-diabetic rats. There was no change in islet somatostatin content at 2 days after the administration of streptozotocin, but thereafter, somatostatin progressively increased in the diabetic animals by 45% at 2 weeks, 230% at 6 weeks, and 500% by 6 months. By contrast, islet glucagon rose acutely and maintained a constant 2-fold elevation irrespective of the duration of the diabetes. Morphometric analysis of the somatostatin- and glucagon-producing cells in the islets revealed an apparent augmentation of both cell types. The concentration of somatostatin per total pancreas was also increased in the diabetic animals, suggesting that the islet increase was part of a true increase in pancreatic somatostatin. Pancreatic glucagon was unchanged despite the islet increase. The increase in pancreatic somatostatin was paralleled by an elevation in gastric somatostatin concentration, implying a common mechanism in response to streptozotocin for the somatostatin cells in these two sites. There was no change in hypothalamic somatostatin concentration. Islet somatostatin was also increased in alloxan-diabetic rats. suggesting that streptozotocin does not stimulate the D cells directly.

The patient with recurrent aphthous ulcers and the patient with recurrent herpes labialis: a study of two population samples

Persons who suffer recurrent canker sores and fever blisters seem to have a common response mechanism to both syndromes. Although similarities may be only characteristics common to both diseases, there is more than a superficial similarity between persons who suffer from recurrent canker sores and persons who suffer from recurrent fever blisters.