Mechanisms of survival of protozoan parasites in mononuclear phagocytes

The understanding of the mechanisms whereby intracellular parasites counteract the microbicidal processes of macrophages has progressed considerably in recent years. Various factors contribute to intracellular parasite destruction; from a biochemical standpoint, particularly important is the oxidative burst triggered by phagocytosis and by macrophage ‘activation', that leads to the generation of toxic metabolites of oxygen. At the ultrastructural level, fusion of the parasitophorous vacuole with surrounding lysosomes appears to be a pre-requisite for the final digestion and elimination of the infecting microorganisms. The counter-measures evolved by microorganisms to escape intracellular destruction are best illustrated by studies in vitro on the interaction of parasites of the Leishmania, Toxoplasma and Trypanosoma spp. with mononuclear phagocytes. Some microbes are able to inhibit the fusion of phagosomes with lysosomes, thus avoiding the potentially harmful action of lysosomal hydrolases. Other microorganisms are able to resist the effects of such enzymes, perhaps by secreting inhibitory substances. Others still avoid lysosomes by leaving the phagocytic vacuole, to reach the cytoplasmic matrix where their development is unhindered. Particularly critical is the capacity of certain parasites to subvert the lethal effects of the oxidative burst. This can be achieved either by failing to evoke this metabolic response, or by producing scavengers that can detoxify harmful oxygen metabolites. Intracellular death or survival will thus depend on a delicate balance between the potency of macrophage cidal mechanisms, and the efficacy of the protective measures evolved by the infecting agent

INFECTION AND TRANSFORMATION OF MOUSE PERITONEAL MACROPHAGES BY SIMIAN VIRUS 40

The stimulation of DNA synthesis in mouse (C57BL) macrophages explanted in vitro was demonstrated after treatment with conditioned medium or infection with SV40. In the latter case, induction of SV40 T antigen was detected before TdR-3H incorporation. Even though all macrophages were infected (T antigen-positive), they exhibited considerable pleomorphism, accompanied by functional differences. Permanent lines of SV40-transformed macrophages were eventually established, and one clone was isolated which replicates indefinitely and has many properties of primary macrophages: high acid phosphatase and phagocytic activity, lysozyme production, and specific antigenic determinants. These cells differ from normal macrophages in that they contain the SV40 genome, can be trypsinized, and do not require conditioned medium for continued replication

Constance mirror program: Progress and plans

The current state of the mechanics of the Constance II experiment, the physics results gathered, the motivation background, and future plans for the Constance II experiment are reviewed. Several improvements have been made and several experimental investigations have been completed. These include the construction/installation/testing of: (1) liquid-nitrogen cooled, Ioffe bars installed, (2) a diverter coil (3) the 100 kW ICRF generator, (4) the data acquisition system, and (5) the optimum hot-iron operation of the machine with Titanium and pulsed-gas plasma guns. Measurements were made of the density, temperature, and radius of the plasma. Ion-cyclotron fluctuations were observed, their bandwidth measured, and data collected demonstrating resonance heating. New X-ray diagnostics were designed and purchased, and progress on the Thomson scattering was made. Finally, a new hot cathode gun was designed and constructed

Preface to the Special Issue: Strategic Opportunities for Fusion Energy

The Journal of Fusion Energy provides a forum for discussion of broader policy and planning issues that play a crucial role in energy fusion programs. In keeping with this purpose and in response to several recent strategic planning efforts worldwide, this Special Issue on Strategic Opportunities was launched with the goal to invite fusion scientists and engineers to record viewpoints of the scientific opportunities and policy issues that can drive continued advancements in fusion energy research