Photosystem I from the unusual cyanobacterium Gloeobacter violaceus.

Photosystem I (PS I) from the primitive cyanobacterium Gloeobacter violaceus has been purified and characterised. Despite the fact that the isolated complexes have the same subunit composition as complexes from other cyanobacteria, the amplitude of flash-induced absorption difference spectra indicates a much bigger antenna size with about 150 chlorophylls per P700 as opposed to the usual 90. Image analysis of the PS I preparation from Gloeobacter reveals that the PS I particles exist both in a trimeric and in a monomeric form and that their size and shape closely resembles other cyanobacterial PS I particles. However, the complexes exhibit a higher molecular weight as could be shown by gel filtration. The preparation contains novel polypeptides not related to known Photosystem I subunits. The N-terminal sequence of one of those polypeptides has been determined and reveals no homology to known or hypothetical proteins. Immunoblotting shows a cross-reaction of three of the polypeptide bands with an antibody raised against the major LHC from the diatom Cyclotella cryptica. Electron microscopy reveals a novel T-shaped complex which has never been observed in any other cyanobacterial PS I preparation. 77 K spectra of purified PS I show an extreme blue-shift of the fluorescence emission, indicating an unusual organisation of the PS I antenna system in Gloeobacter.

Localized arteriovenous malformation of the jejunum.

Arteriovenous malformations of the small intestine are a vanishingly rare cause of hemorrhage from the gastrointestinal tract. To our knowledge, only one previous case has been reported. We describe a 41-year-old man with massive gastrointestinal bleeding as the result of a jejunal arteriovenous malformation. We discuss the histologic differentiation from angiodysplasia.

Enhancement of macrophage and monocyte cytotoxicity by the surface active material of lung lining fluid.

The surface active material (SAM) of alveolar lining fluid has been shown to have immunologic activity. We studied the effect of SAM on monocyte-macrophage cytotoxicity against a tumor cell line. Alveolar macrophages were studied from 15 subjects without cancer. Tumor growth, as assessed by tritiated thymidine incorporation, was significantly inhibited by the macrophages alone (tumor alone median 39,401 cpm, macrophages plus tumor median 12,153 cpm, P less than 0.01). Tumor cytotoxicity was enhanced by preincubating the macrophages with lipopolysaccharide (median 37 cpm, P less than 0.01) or coincubating the tumor cells and macrophages with SAM (median 5474 cpm, P less than 0.01). Similar results were seen when using blood adherent mononuclear cells. There was increasing cytotoxicity for the adherent mononuclear cells with increasing amounts of SAM. When the various phospholipids of SAM were studied, it was found that phosphatidylcholine, sphingomyelin, and phosphatidyl glycerol all enhanced adherent mononuclear cell cytotoxicity, whereas phosphatidylinositol inhibited adherent mononuclear cell cytotoxicity. These studies suggest that SAM may have important immunoregulatory function for the alveolar macrophage.