Chemical excitability of axons: excitatory and inhibititory effects of putative neurotransmitters and modulators on frog sciatic nerves.

The microiontophoretic administration of putative neuromodulators (acetylcholine, norepinephrine, dopamine, 2-phenylethylamine, tryptamine, histamine) triggered firing or inhibited on-going activity in isolated frog sciatic nerves.     

Electrophoretic analysis of clinical dextrans

Résumé On démontre que l'électrophorèse de dextrans cliniques peut être employée pour la détermination de leur poids moléculaire et de la polydispersité.     

Herd immunity to helminth infection and implications for parasite control

Despite much research on immunological responses to helminth parasites, knowledge of the dynamic interplay between levels of herd immunity in humans and the rates of exposure, establishment and mortality of parasites remains limited. We describe here a simple mathematical model for the population dynamics of helminth infections which mirrors the development of a degree of acquired immunity within populations which are genetically heterogeneous with respect to immunological responsiveness. We interpret observed patterns in the age-specific intensity of infection and attempt to understand the possible effects of control measures based on chemotherapy and vaccination. Mass chemotherapy can, in some circumstances, reduce the level of herd immunity such that average worm burdens in the adult age classes rise above their precontrol levels. When certain individuals or groups are predisposed to heavy infection, selective or targeted drug treatment can have significantly greater impact than mass or random application. Conversely, model predictions suggest that effective parasite control by vaccination (if and when vaccines become available) is difficult to achieve in communities that are genetically heterogeneous in their ability to mount protective responses to infection.     

Trace metal requirements in total parenteral nutrition: A theoretical approach by mathematical modeling

Summary A new computer-based approach has been developed to assess the optimal doses of essential trace metal ions which should be included in nutritive mixtures, used in human total parenteral nutrition, to compensate for the ligand-induced losses of these metal ions. An example of application is given for zinc, copper and manganese.     

Molecular mechanisms of lipoprotein receptor signalling

The low-density lipoprotein (LDL) receptor is the prototype of a classical endocytosis receptor that mediates the uptake of extracellular ligands. Other members of the LDL receptor gene family, on the other hand, have been shown to regulate intracellular signalling cascades. Among these are the LDL receptor-related protein 1, LRP1, a promiscuous and ubiquitously expressed receptor which is critically involved in a multitude of diverse physiological processes; the Reelin receptors ApoER2 and VLDL receptor, which participate in neuronal development; and megalin, a multifunctional receptor expressed in various epithelia. In this review, we focus on recent developments that highlight similarities and differences between these related receptors and their biological function, and discuss open questions as to the underlying molecular mechanisms.     

The biosynthesis of diterpenoid alkaloids

Zusammenfassung Die diterpenoiden Alkaloide Browniin und Lycoctonin wurdenin vivo aus Mevalonsäure-2-¹⁴C hergestellt. Sie zeigten, aus Acetat-1-¹⁴C und -2-¹⁴C gewonnen, eine geringere Wirksamkeit. Die Biosynthese dieser Alkaloide scheint somit der der anderen Terpene analog.