The effects of diltiazem onPeriplaneta americana

Summary The effects of the calcium antagonist diltiazem on nerve and muscle in the cockroachPeriplaneta americana were examined. Diltiazem was observed to inhibit myogenic and glutamate-induced contractions of the visceral muscle while having either a potentiating, an inhibiting or a biphasic effect against proctolin-induced contractions. Against the isolated nervous system, diltiazem induced an increase in spontaneous discharge activity, followed by nerve block. Injection of diltiazem into cockroaches produced behavioral and toxic effects.Acknowledgments. The expert technical assistance of Miss Susan Auffarth is gratefully acknowledged. Bioresmethrin was provided by Dr. G.J.P. Singh. We would like to thank Nordic Laboratories for the gift of diltiazem.     

Genetic control of rye endosperm proteins

Résumé En comparant les diagrammes d'électrophorèse en gels d'amidon de gliadine obtenus à partir d'un blé hexaploïde, d'un seigle diploïde et de blé + seigle amphiploïdes avec les lignes d'additionnement des chromosomes blé-seigle on constata qu'un chromosome de seigle contrôle toutes les gliadines du seigle.     

Chromosomal landscape of nucleosome-dependent gene expression and silencing in yeast

Eukaryotic genomes are packaged into nucleosomes, which are thought to repress gene expression generally. Repression is particularly evident at yeast telomeres, where genes within the telomeric heterochromatin appear to be silenced by the histone-binding silent information regulator (SIR) complex (Sir2, Sir3, Sir4) and Rap1 (refs 4-10). Here, to investigate how nucleosomes and silencing factors influence global gene expression, we use high-density arrays to study the effects of depleting nucleosomal histones and silencing factors in yeast. Reducing nucleosome content by depleting histone H4 caused increased expression of 15% of genes and reduced expression of 10% of genes, but it had little effect on expression of the majority (75%) of yeast genes. Telomere-proximal genes were found to be de-repressed over regions extending 20 kilobases from the telomeres, well beyond the extent of Sir protein binding and the effects of loss of Sir function. These results indicate that histones make Sir-independent contributions to telomeric silencing, and that the role of histones located elsewhere in chromosomes is gene specific rather than generally repressive.     

Structural basis for vinculin activation at sites of cell adhesion

Vinculin is a highly conserved intracellular protein with a crucial role in the maintenance and regulation of cell adhesion and migration. In the cytosol, vinculin adopts a default autoinhibited conformation. On recruitment to cell-cell and cell-matrix adherens-type junctions, vinculin becomes activated and mediates various protein-protein interactions that regulate the links between F-actin and the cadherin and integrin families of cell-adhesion molecules. Here we describe the crystal structure of the full-length vinculin molecule (1,066 amino acids), which shows a five-domain autoinhibited conformation in which the carboxy-terminal tail domain is held pincer-like by the vinculin head, and ligand binding is regulated both sterically and allosterically. We show that conformational changes in the head, tail and proline-rich domains are linked structurally and thermodynamically, and propose a combinatorial pathway to activation that ensures that vinculin is activated only at sites of cell adhesion when two or more of its binding partners are brought into apposition.