CD4-CD8- splenic T cells from Lewis rats recovered from experimental autoimmune encephalomyelitis respond to encephalitogenic T cells that mediate this disorder

We previously demonstrated that encephalitogenic CD4+ T lymphocytes from the long-term cultured line S1, specific for myelin basic protein, induce a CD8+ T cell population in vivo that protects naive Lewis rats against experimental autoimmune encephalomyelitis caused by S1 cells. In order to determine the contribution of individual T cell population in the development of induced resistance, we have analyzed the in vitro proliferative capacity of phenotypically distinct T cell populations isolated from S1-immunized rats. We found that both CD8+ and CD8-CD4- T cells show striking proliferative responses when stimulated with S1 cells, whereas CD4+ T cells show only minimal responses. In addition, a significant proportion of the CD8-CD4- cells, after stimulated by S1 cells, became CD8+ and had a strong cytolytic activity toward S1 cells. These results suggest a contribution of double-negative splenic T cells in the regulatory circuit associated with autoimmune encephalomyelitis.     

Relationship of trace metals to the alcohol-effect in citric acid synthesis by Aspergillus fonsecaeus

Summary Synthesis of citric acid by Aspergillus fonsecaeus in a basal medium supplemented with trace metals (iron, zinc, copper, and manganese) and methanol has been investigated. Methanol was found to be stimulatory to acid synthesis when manganese or manganese and iron were present. No other mineral tested could be substituted for manganese in the presence of the alcohol. However, comparable yields of citric acid could be obtained if methanol were deleted, the concentration of iron increased and zinc substituted for manganese.This investigation was conducted under a contract with the United States Department of Agriculture, authorized by the Research and Marketing Act, and administered through the Northern Regional Research Laboratory.     

Growth cone behavior on gradients of substratum bound laminin

We have tested the ability of a gentle gradient of neurite-promoting activity to orient the extension of embryonic growth cones. Gradients of neurite-promoting activity were made with biologically active, tritium-labeled laminin. The distributions of laminin bound to glass substrata were visualized by autoradiography and quantified with an image processing system. Embryonic chick sympathetic ganglia were explanted onto laminin gradients and cultured. No tendency for neurites to be oriented up-gradient was detected by examining the morphology of explants. Time-lapse studies of individual growth cones detected no up- or down-gradient bias in growth cone motility. These results suggest that growth cone orientation is relatively insensitive to a graded distribution of a naturally occurring neurite-promoting molecule.     

Complex binding interactions between multicomponent mixtures and odorant receptors in the olfactory organ of the Caribbean spiny lobster Panulirus argus

Our study was designed to examine how components of complex mixtures can inhibit the binding of other components to receptor sites in the olfactory system of the spiny lobster Panulirus argus. Biochemical binding assays were used to study how two- to six-component mixtures inhibit binding of the radiolabeled odorants taurine, L-glutamate and adenosine-5'-monophosphate to a tissue fraction rich in dendritic membrane of olfactory receptor neurons. Our results indicate that binding inhibition by mixtures can be large and is dependent on the nature of the odorant ligand and on the concentration and composition of the mixture. The binding inhibition by mixtures of structurally related components was generally predicted using a competitive binding model and binding inhibition data for the individual components. This was not the case for binding inhibition by most mixtures of structurally unrelated odorants. The binding inhibition for these mixtures was generally smaller than that for one or more of their components, indicating that complex binding interactions between components can reduce their ability to inhibit binding. The magnitude of binding inhibition was influenced more by the mixture's precise composition than by the number of components in it, since mixtures with few components were sometimes more inhibitory than mixtures with more components. These findings raise the possibility that complex binding interactions between components of a mixture and their receptors may shape the output of olfactory receptor neurons to complex mixtures.