ABSTRACT
CD7+CD3- cells purified (greater than 99.99%) by FACS from the peripheral blood of healthy adults include precursors for mature T cells that have the capacity to differentiate into TCR-1+ or TCR-2+ CD3+ cells. Extrathymic differentiation was demonstrable from all eight healthy donors in the presence of a high concentration of IL-2, mitogenic levels of PHA, and irradiated blood mononuclear feeder cells, after a lag of approximately 40 d in vitro. The extrathymic T (ET) cells were predominantly TCR-1+, although TCR-2+ cells were also derived. ET TCR-1+ cells were CD4-CD8-, CD4-CD8DIM+, and CD4+CD8-, and were distinguished from natural T TCR-2+ cells by a variety of cell surface markers. The ET cells had phenotypes generally displayed by normal mature T cells, although the CD5DIM+ on ET cells was more typical of thymocytes. Acquisition of CD3 on purified CD7+CD3- cells was not due to antigenic modulation or growth of contaminants, and ET cells could be demonstrated at the clonal level. Studies in athymic mice and bone marrow recipients support the view that extrathymic maturation does occur in vivo. Whether the CD7+CD3- cell population was unexposed to the thymus, or exposed but not processed, is unknown. In any case, unusual or "forbidden" autoreactive specificities are predicted since ET cells differentiate without thymic selection of the TCR.
Subject(s)
Antigens, Differentiation, T-Lymphocyte/analysis , Receptors, Antigen, T-Cell/analysis , T-Lymphocytes/classification , Antigens, CD7 , Antigens, Surface/analysis , CD3 Complex , Cell Differentiation , Cells, Cultured , Clone Cells , Flow Cytometry , Humans , Lymphocyte Activation , T-Lymphocytes/cytology , T-Lymphocytes/immunologyABSTRACT
After extraction with methylene chloride, isolation of the unsaponifiable lipid fraction and enrichment by two-step column chromatography, the oxycholesterols were gas chromatographically separated in the form of their trimethylsilyl ethers on a thin film capillary and identified by mass spectrometry. The three major products of cholesterol autoxidation were cholest-5-en-3 beta, 7 alpha-diol(I) its 7 beta-epimer(II) and 5,6-epoxy-cholestan-3 beta-ol(III). In addition, traces of cholestan-3 beta, 5 alpha, 6 beta-triol and cholest-5-en-3 beta,25-diol were detected in some samples. Quantitative analysis was performed with cholest-5-en-3 beta,19-diol as internal standard. The highest concentrations of I-III were found in spray dried egg powders (total amount 15-60 micrograms/g). Parmesan cheese, butter oil and sausages contained significantly lower levels of I-III (total amount 0.1-2.6 micrograms/g). The concentrations of I-III increased strongly when butter oil and beef tallow were heated at 170 degrees C in the presence of air for a longer period.
Subject(s)
Antioxidants/analysis , Cholesterol/analysis , Food Analysis , Animals , Butter/analysis , Cheese/analysis , Chromatography, Gas , Meat Products/analysisABSTRACT
One nonenzymic and two enzymic forms of ascorbate peroxidase were found in pea leaves, and designated A, B and C. Form A was due to a low molecular weight, heat-stable component, and could be separated from the enzymic forms by gel filtration. Forms B and C were soluble proteins with an apparent molecular weight of 57,000. These two forms could be separated by cation-exchange chromatography on CM-Sephadex C-50. This technique was incorporated into a procedure for their partial purification. Several properties of B and C were found to be similar: they were active over a wide pH range (5 to 8), they displayed very high affinities for H(2)O(2) (Km<5 µM), and Km values for ascorbate (6.5 mM and 2.9 mM, respectively) were comparable to physiological concentrations of this substrate. These properties are considered conducive to the proposed physiological role of ascorbate peroxidase, viz prevention of H(2)O(2) accumulation.
ABSTRACT
Lipoxygenase isoenzymes L-1 (optimum pH 9.0) and L-2 (pH 6.5) were incubated with linoleic acid. The extracted volatile compounds were separated by gas-chromatography and analysed by mass spectrometry. The relative amounts of volatile carbonyl compounds, which were formed during catalysis were determined (mole percent). L-1 yielded hexanal (greater than 90% at pH 7 and 70% at pH 8.5). L-2 at pH 7 yielded hexanal (31), two geometric isomers of 2,4-decadienal (40), 2-trans-heptenal (12) and 2-trans-octenal (10).
Subject(s)
Isoenzymes/metabolism , Lipoxygenase/metabolism , Plants/enzymology , Linoleic Acids , Glycine maxABSTRACT
Homogenates of apples and pears were incubated (25 degrees C, 20 min) with linoleic and linolenic acid. The major products were fatty acid hydroperoxides. The ratio of 13- to 9-hydroperoxides were at least 82:18 in favour of the 13-isomer for apples and 10:90 in favour of the 9-isomer for pears. The significance of the results for the formation of flavour compounds in apples and pears is discussed.
