Regulatory factors produced by lymphocytes. I. The occurrence of multiple alpha-lymphotoxins associated with ribonuclease activity.

Supernatant fluids of mitogen-activated human tonsil lymphocytes contain large amounts of a factor toxic to mouse L cells. This substance, with a m.w. of 80,000 +/- 5,000 daltons, is called alpha-lymphotoxin (alpha-LT), to differentiate it from another toxin elaborated by mitogen activated human blood lymphocytes, called beta-lymphotoxin (beta-LT), which differs from alpha-LT in size (45,000 +/- 5,000 daltons), antigenicity, and stability. Further purification of alpha-LT by sequential phosphocellulose and DEAE-cellulose chromatography and polyacrylamide gel electrophoresis (PAGE) identifies a series of cytotoxins differing in ion exchange characteristics and electrophoretic mobilities. The three PAGE fractions (PAGE Ia, Ib and II), recovered in 2, 4.6, and 21% yield from the starting serum-free culture supernatant, represent purifications of 24-, 24- and 1851-fold, respectively. Each cytotoxic fraction has a ribonuclease activity. Comparison of RNase and mouse L cell cytotoxic activities of the three alpha-LT fractions shows that both activities for all three fractions have a similar temperature stability pattern and that both are similarly inhibited by DNA, single strand forms better than double strands, by glycerol in 5 to 20% concentration, and by protein denaturing reagents. These observations suggest, but do not prove, that mouse L cell toxicity and RNase activity are mediated by the same substance, which appears to occur in multiple or isozymic forms.     

M?ssbauer effect studies on some bioinorganic complexes of europium.

The bioinorganic complexes of europium with N-acetyl-DL-alanine, N-acetyl-DL-valine, and DL-alanyl-DL-alanine have been synthesized and the M?ssbauer spectra at room temperature have been measured for these solid state complexes. The M?ssbauer parameters indicate that the water molecules in these complexes are not directly linked to the central europium ion and are outside the coordination sphere of europium and biological ligands, and that the chemical bond between the europium ion and the ligands may be predominantly ionic in character, with the possibility of partial covalent contribution.     

Absorption of x-radiation by single crystals of proteins containing labile metal components: the determination of the number of iron atoms within the central core of ferritin

The number of metal atoms contained within a displaceable inorganic component of a metalloprotein was determined by considering X-ray absorption by single crystal samples of holo- and apo-proteins. Since this method is non-destructive, it can be used to determine the number of metal atoms associated with the molecules forming the crystal actually used for X-ray diffraction data collection and subsequent structure solution. The method has been applied to the iron storage protein ferritin, isolated from horse spleen, to give a reliable estimate of the average iron content of the ferritin molecules within the crystal. This value, of around 2000 iron atoms per molecule is consistent with that found for a typical ferritin preparation in solution and suggests non-selectivity of the crystallisation process for ferritin in terms of molecular iron content.     

Diel and spatial drifting patterns of silver perch Bidyanus bidyanus eggs in an Australian lowland river

Densities of silver perch Bidyanus bidyanus eggs drifting in the Murray River, Australia, suggested a peak spawning time between 2100 and 0100 hours, and a propensity to drift in higher densities near shore and at the bottom of the water column. The results highlight the need to consider such spatial and temporal patterns when estimating species-specific drift abundances.