Liquid preservation of highly purified human granulocytes

Highly purified human granulocytes isolated from continuous flow centrifugation leukapheresis concentrates by counterflow centrifugation-elutriation were stored at 4 °C in concentrations of 6 × 10⁶ to 1 × 10⁷ granulocytes per milliliter for up to 14 days. The in vitro physiological function assays of phagocytosis, oxygen consumption associated with phagocytosis, bacterial growth inhibition, chemotaxis, and five enzyme analyses indicated good storage survival for up to 4 days. Stored granulocytes separated from other blood cells have greater storage stability than granulocytes stored as leukapheresis concentrates. After 14 days of storage a small percentage of granulocytes still maintained all physiological functions, with the exception of chemotaxis. Of the five enzymes assayed, only the enzyme activity of leucine aminopeptidase decreased significantly by the 14th day of storage. The storage stability of each physiological function assayed decreased as follows: bacterial growth inhibition (most stable), phagocytosis, oxygen consumption, and chemotaxis (least stable).     

C-13 nuclear magnetic resonance spectroscopy of humic substances

Summary Evidence is presented from a preliminary study showing that C-13 N.M.R. spectroscopy is a useful new tool for the elucidation of the structure of soil organic matter.     

Interaction of methotrexate with polycationic carriers

Binding parameters were measured for the $\text{in vitro}$ interaction of methotrexate with poly-L-lysine and diethylaminoethyl dextran. The complexes were found to have apparent affinity constants of 2590 and 440 M^?1 respectively at 37°, ionic strength 0.02. For hypotonic solutions containing therapeutic concentrations of methotrexate, this results in 87% binding of the drug to poly-L-lysine and 74% to diethylaminoethyl dextran. While the binding decreased to about 50% upon increasing ionic strength to physiologic levels, sufficient drug-carrying capacity was retained at isotonicity to support the potential utility of such complexes as tissue-specific drug carriers.     

Positioning and maintenance of embryonic body wall muscle attachments in C. elegans requires the mup-1 gene

As part of a general study of genes specifying a pattern of muscle attachments, we identified and genetically characterised mutants in the mup-1 gene. The body wall muscles of early stage mup-1 embryos have a wild-type myofilament pattern but may extend ectopic processes. Later in embryogenesis, some body wall muscles detach from the hypodermis. Genetic analysis suggests that mup-1 has both a maternal and a zygotic component and is not required for postembryonic muscle growth and attachment. mup-1 mutants are suppressed by mutations in several genes that encode extracellular matrix components. We propose that mup-1 may encode a cell surface/extracellular matrix molecule required both for the positioning of body wall muscle attachments in early embryogenesis and the subsequent maintenance of these attachments to the hypodermis until after cuticle synthesis.     

Séquences tripeptidiques typiques du collagène: étude conformationnelle quantique

Theoretical and experimental investigations on the conformations of synthetic polytripeptides, with Gly-R₂-R₃ general repetitive sequence, are of great interest for the comprehension of the factors wich contribute to the triple helix stabilization.Using appropriate molecules as models, we have investigated by the PCILO method the intrinsic conformational possibilities of each « in situresidue for the following cases: Gly-imino-imino, Gly-amino-imino and Gly-imino-amino which represent the most important sequences occuring in the primary structure of collagen. The computations were carried out taking into account the two pyrrolidine ring puckerings and the preferential side-chains orientations.Extending our previous work concerning the isomeric polytripeptides Gly-X-Pro and Gly-Pro-X with X {Pro, Phe} we have studied the cases of X {Ala, Ser}. In this brief communication, we present a preliminary synthesis of these recent results.     

Nonvulnerability of ecosystems in unpredictable environments

One way to bracket the effects of a real environment on an ecosystem during a finite time interval is to use the concept of vulnerability. If a deterministic model ecosystem has a good Lyapunov function, it may be possible to derive simple and useful tests for the system to be nonvulnerable. For a subset of Lotka-Volterra models, the system is nonvulnerable if the smallest eigenvalue of a certain matrix is not only positive, but is greater than a positive number, which depends on a priori estimates for the bounds on the unpredictable forcing functions. The bounded but unknown functions which act on the Lotka-Volterra equations also can be interpreted as errors in the system's equations which can be tolerated without a qualitative change in the behaviour of its solutions.