Endotoxin modulation of hepatocyte secretory and cellular protein synthesis is mediated by Kupffer cells.

We hypothesize that alterations of hepatocyte function in sepsis are modulated by endotoxin (lipopolysaccharide)-triggered Kupffer cells. In the present experiments the effect of lipopolysaccharide on secreted and cellular proteins synthesized by hepatocytes cultured alone or cocultured with Kupffer cells was investigated using polyacrylamide gel electrophoresis. Lipopolysaccharide had no direct effect on the types or amounts of secreted proteins synthesized by hepatocytes alone. Kupffer cells coculturing resulted in increased synthesis of some hepatocyte proteins (68k and 23k) whose production was not altered by lipopolysaccharide. In contrast, addition of lipopolysaccharide to the hepatocyte-Kupffer cell coculture substantially decreased synthesis of several proteins (73k, 66k, and 35k). Despite an overall decrease in protein synthesis of hepatocytes cocultured with Kupffer cells after the addition of lipopolysaccharide, there was increased synthesis of several individual proteins (58k and 44k). Similar effects were seen in synthesis of cellular protein. The addition of recombinant interleukin 1 to hepatocytes alone or in coculture had no effect on the amount or type of protein synthesized. We conclude that Kupffer cells regulate the types and amounts of individual proteins synthesized by hepatocytes via mediators other than interleukin 1.

Mars: Mariner 9 Spectroscopic Evidence for H2O Ice Clouds.

Spectral features observed with the Mariner 9 interferometer spectrometer are identified as those of H(2)O ice. The measured spectra are compared with theoretical calculations for the transfer of radiation through clouds of ice particles with variations in size distribution and integrated cloud mass. Comparisons with an observed spectrum from the Tharsis Ridge region indicate H(2)O ice clouds composed of particles with a mean radius of 2.0 micrometers and an integrated cloud mass of 5 x 10(-5) grain per square centimeter.

Ocean color determination through a scattering atmosphere.

Measurements made of the surface level albedo for ocean water containing various concentrations of phytoplankton indicate a strong correlation between wavelength dependent albedo ratios and phytoplankton chlorophyll concentration. To sense surface level albedo ratios from space platforms it is necessary to correct for the scattering and absorption properties of the atmosphere for the wavelengths in question. Atmospheric scattering models were constructed to calculate corrections at two wavelengths, 0.46 mum and 0.54 mum. The relationship between albedo ratios at the top of the atmosphere and at surface level was made for several different aerosol optical depths. Assuming a natural background uncertainty in the aerosol optical depth of 0.1 it is found that the chlorophyll concentration may be determined to within one standard deviation of from 0.5 mg to 2.5 mg/m(3), depending upon the solar zenith angle at the time of measurement. By remotely sensing the aerosol optical depth to a greater accuracy it appears feasible to detect chlorophyll concentrations to an uncertainty approaching 0.1 mg/m(3).