Behavior of a dust grain in the double layer of an electric probe in a gas-discharge plasma

Equations for the motion of an individual dust grain in the double layer of a negatively charged cylindrical probe in a glow discharge plasma are derived and solved numerically. The distribution of the electric potential near the probe is determined, and the grain charge is calculated as a function of the distance from the probe for different probe potentials. The trajectories of grains with different initial energies are traced. An analysis of the grain trajectories shows that, at a certain distance from the probe, high-energy grains may be recharged; i.e., the grain charge may change sign. The grains are found to have no direct effect on the probe current in a dusty plasma of a glow discharge.     

Thaumamermis cosgrovei n. gen., n. sp. (Mermithidae: Nematoda) parasitizing terrestrial isopods (Isopoda: Oniscoidea)

Summary A new mermithid nematode, Thaumamermis cosgrovei n. gen., n. sp. (Mermithidae: Nematoda) was found parasitizing two terrestrial isopods (Isopoda: Oniscoidea) in California. The hosts, Armadillidium vulgare (Latr.) (a pillbug) and Porcellio scaber (Latr.) (a sowbug) represent the first cases of isopods attacked by mermithid nematodes. The genus Thaumamermis can be distinguished from all previously described mermithids by the extremely dimorphic spicules, one being short and broad and the other long and filiform. It has been discovered that the nematodes are infected with an iridiovirus which commonly destroys the isopod hosts. ac]19800917     

Rapid increases in the membrane expression of neutral endopeptidase (CD10), aminopeptidase N (CD13), tyrosine phosphatase (CD45), and Fc gamma-RIII (CD16) upon stimulation of human peripheral leukocytes with human C5a.

Rapid increases in the membrane expression of C3 receptors on granulocytes and monocytes in response to the anaphylatoxin C5a have previously been described. In this study we demonstrate increases in the membrane expression of neutral endopeptidase (NEP, CD10, CALLA), aminopeptidase N (APN, CD13), tyrosine phosphatase (CD45/CD45Ro) and the Fc R Fc gamma-RIII (CD16) on granulocytes within minutes of treatment with human C5a. Monocytes responded to C5a with increases in CD13 and CD45/CD45Ro. These membrane modulations could be prevented by preincubating the C5a preparations with anti-C5a mAb C17/5 but not by pretreating the cells with cycloheximide. Increases of CD10, CD13, and CD11b but not CD11a (LFA-1) were also observed in leukocytes from patients undergoing hemodialysis with cuprophan membranes. The increase of CD16 on granulocytes was dependent on the presence of plasma during in vitro activation with C5a indicating that plasma contains inhibitors which prevent the previously described loss of Fc gamma-RIII upon stimulation of the cells.     

Characterization of immunomodulatory properties and accessory cell function of small intestinal epithelial cells.

We have studied the immunomodulatory properties of epithelial cells from the small intestine on T cell immune function in vitro. Proliferation of lymph node cells stimulated either with antigen or with mitogen was inhibited by epithelial cells in a dose-dependent fashion. The epithelial cell-mediated suppression of lymphocyte proliferation was blocked by indomethacin, a cyclooxygenase pathway inhibitor, demonstrating that the suppressive effect of epithelial cells was related to prostaglandin secretion. Furthermore, the action of epithelial cell-secreted prostaglandin on lymphocytes was related to its effect on IL-2 as the suppressive effect of epithelial cells was abrogated by the addition of exogenous IL-2. As previously reported, epithelial cells constitutively express MHC class II and we found them able to present antigen in a class II-restricted fashion when their suppressive effects were blocked by indomethacin. Furthermore, epithelial cells activated by LPS secrete an IL-1 like molecule in a fashion analogous to other antigen-presenting cells. These results demonstrate that epithelial cells can both enhance and suppress in vitro T cell immune responses and further characterize the mechanisms by which intestinal epithelial cells may function in gut-associated immune responses.     

A new restriction fragment length polymorphism in the haptoglobin gene region

Summary Direct gene analysis of the haptoglobin gene region was carried out by Southern blotting using an Hp cDNA as probe. Two types of polymorphism were observed: one due to intragenic duplication, is characterized by a constant fragment length difference of 1700bp observed with several enzymes and by complete correspondence with the protein molecular weight polymorphism; the second type, due to point mutation, was represented by two additional restriction sites for Eco RI and Pst I, with a frequency comparable to that of other genes. These two mutations segregated together in families, suggesting that the recently described Hp related gene is closely linked to the Hp gene. Moreover, they were completely associated with each other. The evolutionary significance of this finding is discussed.     

Synthesis of N-carboxyalkyl and N-aminoalkyl functionalized dipeptide building units for the assembly of backbone cyclic peptides.

To improve the assembly of backbone cyclic peptides, N-functionalized dipeptide building units were synthesized. The corresponding N-aminoalkyl or N-carboxyalkyl amino acids were formed by alkylation or reductive alkylation of amino acid benzyl or tert-butyl esters. In the case of N-aminoalkyl amino acid derivatives the aldehydes for reductive alkylation were obtained from N,O-dimethyl hydroxamates of N-protected amino acids by reduction with LiAlH4. N-carboxymethyl amino acids were synthesized by alkylation using bromoacetic acid ester and the N-carboxyethyl amino acids via reductive alkylation using aldehydes derived from formyl Meldrums acid. Removal of the carboxy protecting group leads to free N-alkyl amino acids of very low solubility in organic solvents, allowing efficient purification by extraction of the crude product. These N-alkyl amino acids were converted to their tetramethylsilane-esters by silylation with N,O-bis-(trimethylsilyl)acetamide and could thus be used for the coupling with Fmoc-protected amino acid chlorides or fluorides. To avoid racemization the tert-butyl esters of N-alkyl amino acids were coupled with the Fmoc-amino acid halides in the presence of the weak base collidine. Both the N-aminoalkyl and N-carboxyalkyl functionalized dipeptide building units could be obtained in good yield and purity. For peptide assembly on the solid support, the allyl type protection of the branching moiety turned out to be most suitable. The Fmoc-protected N-functionalized dipeptide units can be used like any amino acid derivative under the standard conditions for Fmoc-solid phase synthesis.     

Effect of the cytoskeleton dynamic condition on the neuronal plasticity]

Infringement of the Lymnaea stagnalis cytoskeleton condition affected preservation and repeated development of plastic responses. Stabilising of the microtubules led to a dependence of the development and preservation dynamics of the plastic responses. Stabilising of the microfilaments transformed short-term plastic responses into long-term ones. The findings suggest a key role of reorganisation of the cytoskeleton in neuronal plasticity.     

Establishment and Characterization of Cell Lines from Homozygous Brachyury (T/T) Embryos of the Mouse

Lethal mutations in the T/t complex cause stage-specific morphologic abnormalities during early embryogenesis of mice. Although mutant embryos are lethal at the early stages of development, we have succeeded in establishing several cell lines from one of these mutants ( T/T ). Mutant-specific abnormality was not observed in gross morphology and growth patterns of cells. They, however, retained the characters of freshly dissociated embryonic cells to form smaller aggregates than the wild-type in rotation-mediated aggregation.
One of the T/T cell lines (T-1) formed tumors when injected into one-day-old syngeneic and allogeneic host, Expression of H-2 antigens was serologically studied with H-2 specificity 5 as a marker antigen. All lines except T-1 were shown to have this specificity.