Interactions of HSP22 (HSPB8) with HSP20, alphaB-crystallin, and HSPB3

Seven of the 10 mammalian small heat shock proteins (sHSP) are expressed in muscle where they constitute 3% or more of total protein. sHSPs interact with one another, and these interactions are believed to be important for their functions. In cell types expressing multiple sHSPs, it is of interest to know which sHSPs interact with one another. We have previously shown that HSP22 interacts with itself as well as with HSP27, MKBP, and cvHSP. Using yeast two-hybrid assays and F?rster resonance energy transfer microscopy, we now show that HSP22 also can interact with two additional members of the sHSP family, alphaB-crystallin and HSP20. We also show that HSP22 is found in HPLC fractions of primate cardiac muscle containing high molecular weight complexes that include alphaB-crystallin and HSP20. Our results suggest that a variety of oligomers composed of different proportions of different sHSPs may form in cell types expressing multiple sHSPs.     

Carbon input to soil may decrease soil carbon content

It is commonly predicted that the intensity of primary production and soil carbon (C) content are positively linked. Paradoxically, many long‐term field observations show that although plant litter is incorporated to soil in large quantities, soil C content does not necessarily increase. These results suggest that a negative relationship between C input and soil C conservation exists. Here, we demonstrate in controlled conditions that the supply of fresh C may accelerate the decomposition of soil C and induce a negative C balance. We show that soil C losses increase when soil microbes are nutrient limited. Results highlight the need for a better understanding of microbial mechanisms involved in the complex relationship between C input and soil C sequestration. We conclude that energy available to soil microbes and microbial competition are important determinants of soil C decomposition.     

Marmoset red blood cell receptor for membrane-associated complement components is not related to human CR1: partial characterization of the C3-binding proteins responsible for the spontaneous rosette formation between marmoset red blood cells and human leukocytes

Cells from all the human B-lymphoblastoid cell lines tested and most human monocytes form rosettes with marmoset red blood cells (MaRBC). Because previous reports suggested the involvement of complement components in this phenomenon, the mechanism of rosette formation and the eventual similarities between the MaRBC receptor and the CR1 receptor present on human erythrocytes have been analyzed herein. The binding of MaRBC to human leukocytes strongly differs from the immune adherence phenomenon: rabbit anti-human CR1 did not react with MaRBC and the MaRBC receptor-binding activity is Ca2+-dependent. Rosette formation required intact energy metabolism and cytoskeleton integrity of leukocytes. Our attempts to purify the receptor from MaRBC membranes revealed the absence of CR1. Nevertheless, C3-binding proteins were isolated by selective desorption by Sepharose iC3 column chromatography. A three-band pattern was observed under reduced conditions with 74,000, 70,000, and 53,000 molecular weights. It was not possible to further separate these components. This protein complex inhibited the rosette phenomenon between MaRBC and both Raji and U-937 cells, exhibited a very poor cofactor activity, and had no decay-accelerating activity toward the classical C3 convertase. This material did not cross-react with antibodies directed to human proteins. These results showed that erythrocytes from new world monkeys do not express a receptor analogous to the human CR1, but expressed C3-binding protein with low cofactor activity that could recognize membrane-associated complement components.     

Strong increase in hepatic and blood histamine levels after partial hepatectomy in rats]

The histamine rates, when established by fluorometry, according to the method of Shore, in the residual liver and in the whole blood of Wistar-Commentry male rats, quickly increase after partial hepatectomy carried out as described by Higgins and Anderson. The levels reach a peak 24 h after hepatectomy, then progressively lower, and on the 4th day are almost equal to the rates of control or sham operated animals.     

Fluctuations of Feulgen- and diphenylamine-DNA in peripheral leukocytes

The circulating leukocyte is usually considered a mature, differentiated cell which does not normally divide. Cytophotometry of human and mouse leukocyte nuclei, however, reveals significant fluctuations in amounts of Feulgen-DNA in all leukocytes at various times of the day. When analyzed for DNA content by the diphenylamine method, the same samples demonstrate variations closely correlated with those obtained by cytophotometry. Although these data may be interpreted as suggesting, among other things, the presence of metabolic DNA, a preliminary radioautographic study of the uptake of tritiated thymidine in mouse leukocytes failed to demonstrate evidence of DNA synthesis in the entire population of cells. In this study only 6–7% of the total leukocyte population was labelled over a 24-hour period. This discrepancy, when considered in light of other uncertainties concerning the Feulgen and diphenylamine reactions, has led to reservations over the ability of either reaction to reflect the true amount of DNA in cells at all times. Rather, we consider it more likely that both procedures reveal similar incomplete fractions of leukocyte DNA at various times of the day, and that the magnitude of this fraction is, perhaps, determined by cyclic influences acting on such parameters as nuclear volume and degree of packing of the nucleohistones.