Propagating chemoattractant waves coordinate periodic cell movement in Dictyostelium slugs.

Migration and behaviour of Dictyostelium slugs results from coordinated movement of its constituent cells. It has been proposed that cell movement is controlled by propagating waves of cAMP as during aggregation and in the mound. We report the existence of optical density waves in slugs; they are initiated in the tip and propagate backwards.

A Dictyostelium nuclear phosphatidylinositol phosphate kinase required for developmental gene expression.

The generation of diacylglycerol (DAG) in response to receptor stimulation is a well-documented signalling mechanism that leads to activation of protein kinase C (PKC). Putative alternative effectors contain sequences that interact with DAGs, but the mechanisms of signal transduction are unknown. We have identified a Dictyostelium gene encoding a novel protein which contains a domain with high identity to the DAG-binding domain of PKC.

cAMP receptor affinity controls wave dynamics, geometry and morphogenesis in Dictyostelium.

Serpentine G-protein-coupled cAMP receptors are key components in the detection and relay of the extracellular cAMP waves that control chemotactic cell movement during Dictyostelium development. During development the cells sequentially express four closely related cAMP receptors of decreasing affinity. In this study, we investigated the effect of cAMP receptor type and affinity on the dynamics of cell-cell signalling in vivo, by measuring the dynamics of wave initiation and propagation in a variety of cAMP receptor mutants.

The ethics wars. Disputes over international research.

The effort to revise the Declaration of Helsinki and the CIOMS Guidelines has sparked a sometimes vitriolic debate centering on the use of placebo controls.

Inducible nuclear translocation of a STAT protein in Dictyostelium prespore cells: implications for morphogenesis and cell-type regulation.

Dd-STATa, the Dictyostelium STAT (signal transducer and activator of transcription) protein, is selectively localised in the nuclei of a small subset of prestalk cells located in the slug tip. Injection of cAMP into the extracellular spaces in the rear of the slug induces rapid nuclear translocation of a Dd-GFP:STATa fusion protein in prespore cells surrounding the site of injection. This suggests that cAMP signals that emanate from the tip direct the localised nuclear accumulation of Dd-STATa.

Hospital policy on appropriate use of life-sustaining treatment. University of Toronto Joint Centre for Bioethics/Critical Care Medicine Program Task Force.

Objective: To describe the issues faced, and how they were addressed, by the University of Toronto Critical Care Medicine Program/Joint Centre for Bioethics Task Force on Appropriate Use of Life-Sustaining Treatment. The clinical problem addressed by the Task Force was dealing with requests by patients or substitute decision makers for life-sustaining treatment that their healthcare providers believe is inappropriate.

Design: Case study.

The control of chemotactic cell movement during Dictyostelium morphogenesis.

Differential cell movement is an important mechanism in the development and morphogenesis of many organisms. In many cases there are indications that chemotaxis is a key mechanism controlling differential cell movement. This can be particularly well studied in the starvation-induced multicellular development of the social amoeba Dictyostelium discoideum.

Reporting the study populations of clinical trials. Clear transmission or static on the line?

In contrast to attempts that have been made to measure the clarity of reporting of the methods of clinical trials in journal articles, we report here an attempt to measure the accuracy of methods reporting. We focus in this article on eligibility criteria as a test case for the reporting of clinical trial methods. We examined the reporting of eligibility criteria in the protocol, methods paper (if applicable), journal article, and Clinical Alert for articles appearing in print between January 1988 and September 1994 for which a Clinical Alert had been issued.

Ethics. Protecting communities in biomedical research.

Although for the last 50 years, ethicists dealing with human experimentation have focused primarily on the need to protect individual research subjects and vulnerable groups, biomedical research, especially in genetics, now requires the establishment of standards for the protection of communities. We have developed such a strategy, based on five steps. (i) Identification of community characteristics relevant to the biomedical research setting, (ii) delineation of a typology of different types of communities using these characteristics, (iii) determination of the range of possible community protections, (iv) creation of connections between particular protections and one or more community characteristics necessary for its implementation, and (v) synthesis of community characteristics and possible protections to define protections appropriate for each type of community.