Methods of heavy metal electron microscopic histochemistry applied to frog lung surfactant.

Four heavy metal staining methods have been applied to frog lung surfactant. Among them, the iodoplatinate method is the only one that almost exclusively visualizes the phospholipid moiety being produced in the lamellated bodies of the pulmonary epithelial cells and forming the backbone of organized structures within the extracellular lining layer. The other three techniques-ruthenium red-osmium tetroxide, osmium tetroxide-ferrocyanide, acidic phosphotungstic acid in chromatic (Rambourg technique)--more or less give electron contrast to glycoproteins and to a lesser extent to the hydrophilic parts of phospholipids. They all show the extracellular lining layer to be a two component system: the content of the lamellar bodies form--when released--membranous configurations, similar to those observed in mammalian lungs; they unfold in an amorphous hypophase, which is apparently secreted by goblet cells of the pulmonary epithelium.     

On the electronic structure and odours of esters of the isothiocyanic acid

The electronic structure of the esters of the isothiocyanic acid is calculated in an iterative extended Hückel method. Contour diagrams of the valence electron density are given. The odour character of these molecules is discussed in terms of the electronic structure obtained and the theories of smell put forward by Amoore and Wright respectively.     

Distribution and synonymy of Plagiochila punctata (Taylor) Taylor, with hypotheses on the evolutionary history of Plagiochila sect. Arrectae (Plagiochilaceae, Hepaticae)

For a long time, Plagiochila (sect. Arrectae) punctata (Taylor) Taylor has been treated as an endemic of Atlantic Europe. Studies of larger specimen sets demonstrated that the species is widespread in mountainous regions of the Neotropics where it is known under several names including P. stolonifera Lindenb. & Gottsche, P. choachina Gottsche and P. patzschkei Steph. In tropical Africa P. punctata is established as Plagiochila subalpina Steph., nom. illeg. The sporophyte of P. punctata is described for the first time, based on material from Costa Rica. A maximum likelihood analysis of a nrITS sequence alignment with sequences of P. sects. Fuscoluteae (outgroup), Arrectae, and Rutilantes as well as of P. rubescens (Lehm. & Lindenb.) Lindenb. results in a tree with well bootstrap supported Arrectae and Rutilantes clades. ITS sequences of Plagiochila punctata from the Comoros and Zaire are placed in an unsupported monophyletic lineage together with P. punctata sequences from the British Isles and Ecuador. The species is nested in a robust clade with P. spinulosa (Dicks.) Dumort. and P. stricta Lindenb. The weak genetic separation of these three species indicates a recent diversification; the disjunct ranges may be the result of long range dispersal events. Plagiochila rubescens from southern South America is placed sister to P. sect. Arrectae. The latter section possibly originated from southern South American ancestors, diversified in tropical America after the uplift of the Andes and reached the Holarctics and tropical Africa by long range dispersal of diaspores.We are grateful to the curators and owners of the herbaria cited in the text for the loan of specimens, especially to Tamás Pócs, Volker Buchbender and Eberhard Fischer for their continuous support with recent collections from tropical Africa. David Rycroft kindly sent a duplicate of P. rubescens. Financial support of the Deutsche Forschungsgemeinschaft (grant HE 3584/1) is gratefully acknowledged.     

Effect of T-activin on thymocyte reproduction and migration

Forty seven F1 (CBA X C57Bl) mice were used for quantitative morphologic examination of the thymus on 1, 5, 10 and 15 days after a single injection of 0.5 microgram T-activin, and injections of 0.1 microgram of T-activin once a day during 5 days. The number of transformed thymocytes and mitoses figures in cortex was found to be increased reaching a maximum at the 5th day as regards the magnitude and spreading. By the end of the research the number of transformed thymocytes and mitoses returned to initial values. There was a periodical (at the 5th and 10th days) 1 mm2 reduction in the number of thymocytes, an increase in the proportion of medullary thymocytes, reaching maximum at the 5th day, and a tendency towards the reduction of a relative area of the parenchyma. These indicators did not return to the initial values by the 15th days. However there was a tendency towards normalization. The conclusion is made about the stimulatory effect of T-activin on reproduction and migration of thymocytes.     

Biophysical characterization of the interaction of high-density lipoprotein (HDL) with endotoxins.

The interaction of bacterial endotoxins [lipopolysaccharide (LPS) and the 'endotoxic principle' lipid A], with high-density lipoprotein (HDL) from serum was investigated with a variety of physical techniques and biological assays. HDL exhibited an increase in the gel to liquid crystalline phase transition temperature Tc and a rigidification of the acyl chains of the endotoxins as measured by Fourier-transform infrared spectroscopy and differential scanning calorimetry. The functional groups of the endotoxins interacting with HDL are the phosphates and the diglucosamine backbone. The finding of phosphates as target groups is in accordance to measurements of the electrophoretic mobility showing that the zeta potential decreases from -50 to -60 mV to -20 mV at binding saturation. The importance of the sugar backbone as further target structure is in accordance with the remaining negative potential and competition experiments with polymyxin B (PMB) and phase transition data of the system PMB/dephosphorylated LPS. Furthermore, endotoxin binding to HDL influences the secondary structure of the latter manifesting in a change from a mixed alpha-helical/beta-sheet structure to a predominantly alpha-helical structure. The aggregate structure of the lipid A moiety of the endotoxins as determined by small-angle X-ray scattering shows a change of a unilamellar/inverted cubic into a multilamellar structure in the presence of HDL. Fluorescence resonance energy transfer data indicate an intercalation of pure HDL, and of [LPS]-[HDL] complexes into phospholipid liposomes. Furthermore, HDL may enhance the lipopolysaccharide-binding protein-induced intercalation of LPS into phospholipid liposomes. Parallel to these observations, the LPS-induced cytokine production of human mononuclear cells and the reactivity in the Limulus test are strongly reduced by the addition of HDL. These data allow to develop a model of the [endotoxin]/[HDL] interaction.