Cellular maintenance of nuclear protein homeostasis

The accumulation and aggregation of misfolded proteins is the primary hallmark for more than 45 human degenerative diseases. These devastating disorders include Alzheimer’s, Parkinson’s, Huntington’s, and amyotrophic lateral sclerosis. Over 15 degenerative diseases are associated with the aggregation of misfolded proteins specifically in the nucleus of cells. However, how the cell safeguards the nucleus from misfolded proteins is not entirely clear. In this review, we discuss what is currently known about the cellular mechanisms that maintain protein homeostasis in the nucleus and protect the nucleus from misfolded protein accumulation and aggregation. In particular, we focus on the chaperones found to localize to the nucleus during stress, the ubiquitin–proteasome components enriched in the nucleus, the signaling systems that might be present in the nucleus to coordinate folding and degradation, and the sites of misfolded protein deposition associated with the nucleus.     

Frescon: Neurophysiological action of a molluscicide

Summary The molluscicide N-trityl morpholine (Frescon) has an unusual effect on the central nervous system of a freshwater snail. Nerve impulses become grouped into spontaneous bursts, with many cells firing synchronously. This may result from interference with inhibitory processes.We thank Dr.C. B. C. Boyce of Shell Research for materials and information.     

A limit on spin-charge separation in high-Tc superconductors from the absence of a vortex-memory effect.

There is a long-standing debate about whether spin-charge separation is the root cause of the peculiar normal-state properties and high superconducting transition temperatures of the high-Tc materials. In the proposed state of matter, the elementary excitations are not electron-like, as in conventional metals, but rather the electron 'fractionalizes' to give excitations that are chargeless spin-1/2 fermions (spinons) and charge +e bosons (chargons). Although spin-charge separation has been well established in one dimension, the theoretical situation for two dimensions is controversial and experimental evidence for it in the high-Tc materials is indirect. A model with sharp experimental tests for a particular type of separation in two dimensions has recently been proposed. Here we report the results of those experimental tests, placing a conservative upper limit of 190 K on the energy of the proposed topological defects known as visons. There is still debate about the extent to which this experiment can settle the issue of spin-charge separation in the high-Tc copper oxides, because some forms of the separation are able to avoid the need for visons. But at least one class of theories that all predict a vortex-memory effect now are unlikely models for the copper oxides.     

A review of the electrophysiological,pharmacological and single channel properties of heart ventricle muscle cells in the snailLymnaea stagnalis

Although a considerable body of information has accumulated describing the pharmacological properties of a wide range of molluscan muscle types, the physiological bases underlying these properties have not been thoroughly investigated. At present, little is known about the types of ion channels and their regulation in molluscan muscle cell membranes. Voltage-clamp, and more recently, patch-clamp techniques have revealed molluscan muscles possess a complex array of channel types with various pharmacological and electrophysiological properties. The gating properties of these channels and their modulation by chemical agents, however, are still poorly understood. This review summarizes some aspects of molluscan muscle function with particular reference to the heart ventricle muscle of the pond snail,Lymnaea stagnalis.