Production of inositol-phospholipid-derived second messengers in a rat natural killer cell line exposed to susceptible tumor targets

It is currently believed that natural killer (NK) cells kill bound target cells by exocytosis of cytotoxic granules via a calcium-dependent process. After confirming that NK-mediated killing was indeed dependent upon extracellular calcium, we investigated the production of inositol-phospholipid-derived second messengers in a rat NK cell line, RNK, upon exposure to susceptible target cells. These messengers, inositol trisphosphate (IP3) and diacylglycerol (DAG), are associated with calcium-dependent secretory processes in a number of cell types. When RNK cells were exposed to susceptible YAC-1 tumor targets significant amounts of both IP3 and DAG were produced. The levels of the membrane phospholipid parent molecules of these second messengers declined in similarly stimulated RNK cells over a comparable time period. Using three different target cell lines, it was found that the levels of DAG that RNK produced in response to the different targets followed the same rank order as their susceptibility to RNK-mediated lysis. These data suggest that IP3 and DAG are produced in NK cells in response to tumor target cells, and these second messengers may have a functional role in NK-mediated killing.     

IL-4 and granulocyte-macrophage colony-stimulating factor selectively increase HLA-DR and HLA-DP antigens but not HLA-DQ antigens on human monocytes

A number of cytokines were tested for their ability to modulate HLA-DR Ag expression on normal human monocytes. IL-4, granulocyte-macrophage (GM)-CSF as well as IFN-gamma were able to increase HLA-DR Ag expression on monocytes. IFN-alpha was also able to augment HLA-DR Ag expression, but to a lesser degree. Macrophage-CSF, granulocyte-CSF, TNF-alpha, TNF-beta, and IL-6 were not able to augment HLA-DR Ag expression. There were distinct patterns in the ability of different cytokines to augment class II histocompatibility Ag expression. IL-4 and GM-CSF selectively increased only HLA-DR and HLA-DP, but did not increase HLA-DQ antigens on monocytes. IFN-gamma, however, was able to augment the expression of HLA-DR, HLA-DP, and HLA-DQ Ag. Combinations of IFN-gamma with either IL-4 or GM-CSF did not show any synergy for the augmentation of any of the class II antigens on monocytes.     

Six medical students in a community hospital

This paper describes part of an education experiment at the University of British Columbia at Vancouver.Six final-year medical students spent approximately 12 weeks in a community. Their time was divided between the hospital and various doctors'' offices. They answered a simple questionnaire to describe their experiences and commented favourably upon the opportunities for direct patient contact, learning basic skills, informal teaching by both family physicians and consultants, and the variety of work available.They had the opportunity to follow up the progress of the patient and learn the natural history of common illnesses. They achieved their basic objectives. We conclude from their reports and informal conversation that the experiment was successful and recommend other institutions to try similar programs.     

Allopurinol can act as an electron transfer agent. Is this relevant during reperfusion injury?

The xanthine oxidase inhibitor allopurinol markedly enhances myocardial function and decreases ventricular irritability during myocardial reperfusion. In the present report, we have evaluated the molecular mechanism of allopurinol action. First, allopurinol was shown to be a weak radical scavenger. Second, allopurinol was found to act as an electron transfer agent from ferrous iron to ferric cytochrome c. The results suggest that the beneficial effect of allopurinol might partially result from its facilitated electron transport during reperfusion when the lipid components of the chain can be expected to be disordered.     

An enzyme-linked immunosorbent assay for 6-keto PGF

An enzyme-linked immunosorbent assay for 6-keto prostaglandin F_1α, a stable metabolite of prostacyclin, has been developed. The assay allows quantitation of 6-keto PGF_1α in the range 1–200 pg/0.1 ml and shows very low cross reactivity to nine other prostaglandins. Dose dependent stimulation by thrombin of 6-keto PGF_1α formation in human endothelial cells in culture has been used to verify the assay. Quantitation by the enzyme linked immunosorbent assay agrees closely with determination by radioimmunoassay.     

Human alveolar macrophage fibronectin: synthesis, secretion, and ultrastructural localization during gelatin-coated latex particle binding

Human pulmonary alveolar macrophages synthesized and secreted several characteristic high molecular weight proteins for at least 7 d in vitro. Immunoprecipitates of medium and cell lysates from metabolically labeled cultures with specific anti-human plasma fibronectin IgG contained one major labeled polypeptide of molecular weight 440,000 (unreduced) or 220,000 (reduced). An identical polypeptide in conditioned medium from radiolabeled macrophages bound specifically to gelatin-Sepharose, demonstrating that alveolar macrophages synthesized and secreted a molecule immunologically and functionally similar to fibronectin. Fibronectin was the major newly synthesized and secreted polypeptide of freshly harvested alveolar macrophages. Pulse-chase experiments revealed that newly synthesized fibronectin was rapidly secreted into medium, approximately 50 percent appearing by 1 h and 80 percent by 8 h. Immunoperoxidase staining using antifibronectin F(ab’)(2)-peroxidase conjugates revealed the majority of immunoreactive fibronectin to be intracellular, localized to endoplasmic reticulum and Golgi apparatus. No extracellular matrix fibronectin was visualized, and cell surface staining was rarely seen, usually appearing only at sites where cells were closely apposed and not at sites of macrophage-substrate attachment. Similar immunostaining of fibroblast cultures revealed cell surface-associated fibrillar fibronectin. Ultrastructural localization of fibronectin during binding and phagocytosis of gelatin-coated and plain latex particles revealed fibronectin only on gelatin-latex beads and at their cell binding sites. Neigher plain latex beads nor their cell membrane binding sites stained for fibronectin. These results demonstrate that fibronectin is a major product of human alveolar macrophages, is rapidly secreted, and is localized at cell membrane binding sites for gelatin-coated particles. In view of the known binding properties of fibronectin, it may serve as an endogenous opsonic factor promoting the binding of staphylococcus, denatured collagen, fibrin, or other macromolecules to macrophages in the lower respiratory tract.