T Cell Factor-1 Controls the Lifetime of CD4+ CD8+ Thymocytes In Vivo and Distal T Cell Receptor α-Chain Rearrangement Required for NKT Cell Development

Natural killer T (NKT) cells are a component of innate and adaptive immune systems implicated in immune, autoimmune responses and in the control of obesity and cancer. NKT cells develop from common CD4+ CD8+ double positive (DP) thymocyte precursors after the rearrangement and expression of T cell receptor (TCR) Vα14-Jα18 gene. Temporal regulation and late appearance of Vα14-Jα18 rearrangement in immature DP thymocytes has been demonstrated. However, the precise control of lifetime of DP thymocytes in vivo that enables distal rearrangements remains incompletely defined. Here we demonstrate that T cell factor (TCF)-1, encoded by the Tcf7 gene, is critical for the extended lifetime of DP thymocytes. TCF-1-deficient DP thymocytes fail to undergo TCR Vα14-Jα18 rearrangement and produce significantly fewer NKT cells. Ectopic expression of Bcl-x_L permits Vα14-Jα18 rearrangement and rescues NKT cell development. We report that TCF-1 regulates expression of RORγt, which regulates DP thymocyte survival by controlling expression of Bcl-x_L. We posit that TCF-1 along with its cofactors controls the lifetime of DP thymocytes in vivo.     

Liver fatty acid-binding protein in two cases of human lipid storage

Summary FABPs in the various tissues play an important role in the intracellular fatty acid transport and metabolism. Reye's syndrome (RS) and multisystemic lipid storage (MLS) are human disorders characterized by a disturbance of lipid metabolism of unknown etiology. We investigated for the first time L-FABP in these two conditions. Affinity purified antibodies against chicken L-FABP were raised in rabbits, and found to cross-react specifically with partially purified human L-FABP. L-FABP content in liver samples of two patients with RS and MLS was investigated by immuno-histochemistry, SDS-PAGE and ELISA. L-FABP immuno-histochemistry showed increased reactivity in the liver of RS patient and normal reactivity in MLS liver. L-FABP increase in RS liver was confirmed by densitometry of SDS-PAGE and ELISA method. By these two methods the increase amounted to 180% and 199% (p < 0.02), respectively, as compared to controls. A possible role of L-FABP in the pathogenesis of RS is discussed.     

Identification and purification of overlapping cosmid clones of the region Xq24-qter of human X chromosome using HPLC.

The assembly of a large physical map of genomes requires simultaneous analysis of many cosmid clones for overlapping regions. The search for overlapping regions may be achieved by various means. High-performance liquid chromatography (HPLC) provides an alternative to gel electrophoresis since microgram amounts of each DNA fragment may be collected into individual test tubes for further analysis. HPLC has been used to identify overlapping cosmid clones from a pool of cosmid DNA containing the terminal portion of the long arm of the human X chromosome (Xq24-qter). Among 400 cosmids analyzed, 3 were shown to overlap.     

Affinity chromatography of Ankistrodesmus braunii nitrate reductase using blue dextran-sepharose (author's transl)

Blue Dextran has been coupled covalently to Sepharose-4B to purify the enzymatic complex NAD(P)H-nitrate reductase (EC 1.6.6.2) from the green alga Ankistrodesmus braunii by affinity chromatography. The optimum conditions for the accomplishment of the chromatographic process have been determined. The adsorption of nitrate reductase on Blue Dextran Sepharose is optimum when a phosphate buffer of low ionic strength and pH 6.5-7.0 is used. Once the enzyme has been bound to Blue Dextran Sepharose, it can be specifically eluted by addition of NADH and FAD to the washing buffer. However, none of the nucleotides added separately is able to promote the elution of the enzyme from the column. The elution can be also achieved, but not specifically, by increasing the ionic strength of the buffer with KCl. These results have made possible a procedure for the purification of A. braunii nitrate reductase which led to electrophoretic homogeneity, with an overall yield of 70% and a specific activity of 49 units/mg of protein.     

Differential and integral W-values for ionization in gaseous water under electron and proton irradiation: consistency of inelastic collision cross sections.

Differential and integral W-values for ionization in gaseous water for electron and proton irradiation have been analyzed from the theoretical point of view for consistency between ionization and total inelastic collision cross sections. For low-energy electrons, which are ubiquitous for all primary radiations, the experimental or compiled cross sections from different sources are sometimes not consistent with one another. A practical, self-consistent procedure is outlined in such cases. The high-energy asymptotic W-values for differential and integral ionization are calculated to be 33.7 and 34.7 eV, respectively, for electron irradiation and 34.6 and 32.5 eV, respectively, for proton irradiation. The computed variations of the W-values with energy are generally in good agreement with experiment. Integral primary W-values due only to the interactions between the incident particle and the water vapor are calculated to be 43.5 and 45.0 eV for electrons and protons, respectively, in the high-energy asymptotic limit.     

The nuclear pores of early meiotic prophase nuclei of plants

Summary Pollen mother cells at early meiotic prophase fromFritillaria lanceolata, F. mutica, Tulbaghia violacea, the lily “Formobel”,Triticum aegilopoides, T. dicoccoides, T. aestivum and synaptic and asynaptic forms ofT. durum were studied in thin sections with the electron microscope (a) in relation to distribution of nuclear pores (b) in respect of fine structure of the pore complex in those of the first four. The pores were distributed in random clusters during leptotene to pachytene in all plants, except in the two forms ofT. durum where there were either no pores or so few that they were not detectable. Probably correlated with this, the two membranes of the nuclear envelope were often widely separated and frequently sacculated. No pores were seen at leptotene in the part of the envelope to which, in theFritillarias and lily, the nucleolus was adpressed at this time. Evidence supporting a recent model which proposes that annuli are composed of three rings of eight granular subunits was obtained. These subunits as well as a dense central element, observed in most pores, were composed of filaments about 3 nm in diameter and evidently protein in character. There was evidence of a continuity between filaments in the central element and those in the rings of subunits which encircle the pore aperture at both the nuclear and cytoplasmic sides of the pore. In profiles of pores knobbed filaments were sometimes seen extending laterally from the pore wall into the perinuclear space at two sides. Questions concerning the role of the annulus are discussed. The author wish to thank Mr. R. F. Scott for construction to the model.