Stem cell factor is encoded at the Sl locus of the mouse and is the ligand for the c-kit tyrosine kinase receptor.

We have cloned a partial cDNA encoding murine stem cell factor (SCF) and show that the gene is syntenic with the Sl locus on mouse chromosome 10. Using retroviral vectors to immortalize fetal liver stromal cell lines from mice harboring lethal mutations at the Sl locus (Sl/Sl), we have shown that SCF genomic sequences are deleted in these lines. Furthermore, two other mutations at Sl, Sld and Sl12H, are associated with deletions or alterations of SCF genomic sequences. In vivo administration of SCF can reverse the macrocytic anemia and locally repair the mast cell deficiency of Sl/Sld mice. We have also provided biological and physical evidence that SCF is a ligand for the c-kit receptor.     

Vibronic attraction energy for superconductivity in the model of Si-containing organic polymers

Superconducting vibronic interaction has been examined for a model of Si-substituted polyacetylene. Large attractive vibronic interaction for the formation of superconducting electron pair has been found for the electron scattering process in between the and in-plane orbitals in silene unit. Doping of holes in these orbitals would be done by extracting electrons from the out-of-plane orbitals as well as from the in-plane orbitals. If stacking of the model polymers is performed in a parallel manner, the interplane electron pairing has also been found to be favorable on account of small Coulombic repulsion.     

A sensitive and reproducible assay to measure the activity of glucosylceramide synthase and lactosylceramide synthase using HPLC and fluorescent substrates

Glucosylceramide synthase (GlcT) and lactosylceramide synthase (GalT) are key enzymes for the synthesis of major glycosphingolipids of vertebrates. In this article, we report a new reliable method to determine GlcT and GalT activities using the fluorescent acceptor substrates C6-4-nitrobenzo-2-oxa-1,3-diazole (NBD)-ceramide and C6-NBD-glucosylceramide, respectively, and a normal-phase high-performance liquid chromatography (HPLC). The reaction products, C6-NBD-glucosylceramide for GlcT and C6-NBD-lactosylceramide for GalT, could be separated from the corresponding acceptor substrates within 6 min under the conditions used. Reaction products were able to be detected quantitatively at concentrations ranging from 50 fmol to 50 pmol, making it possible to determine both activities using the lysate from 1 x 10(4) cultured CHOP cells (Chinese hamster ovary cells expressing polyoma LT antigen) and one zebrafish embryo. This method was used successfully to evaluate the degree of knockdown of GlcT and GalT during zebrafish embryogenesis after injection of the morpholino-oligo-based antisense into one- to four-cell embryos. These results indicate that the fluorescence-based HPLC method is a highly sensitive, rapid, and reproducible assay for determining GlcT and GalT activities and is useful for evaluating the activities in gene knockdown experiments.     

Atypical virulence in a type III Toxoplasma gondii strain isolated in Japan

The virulence of a type III Toxoplasma gondii strain isolated in Japan and designated here as TgCatJpGi1/TaJ was examined in mice and micro minipigs in this study. Despite its type III genotype, oral or intraperitoneal inoculation of cysts from it resulted in severe virulence in C57BL/6J and BALB/c mice. In contrast, mice inoculated with a high dose of TgCatJpGi1/TaJ tachyzoites showed no obvious clinical signs of infection, and all of them survived for >21?days post-inoculation. Furthermore, no clinical signs of infection were seen when micro minipigs were inoculated with 900 cysts. Interestingly, our allelic type screening of the virulence-related rop5, rop16, rop17, and rop18 genes, as based on restriction fragment length polymorphism analysis (RFLP), revealed that the RFLP patterns for TgCatJpGi1/TaJ were identical to those from nonvirulent type III parasites. These results suggest that TgCatJpGi1/TaJ possesses an unknown virulence factor or factors.     

Characterization of a second gene product related to rabbit cytochrome P-450 1

A cDNA, p1-88, was cloned from a library constructed using rabbit liver mRNA. Sequence analysis indicates that p1-88 is highly similar (congruent to 95%) to the cDNA, p1-8, that encodes rabbit liver cytochrome P-450 1 and that had been isolated from the same library. The predicted amino acid sequence of the protein encoded by p1-88, P-450 IIC4, differs at 25 of 487 amino acids from that encoded by p1-8. P-450 IIC4 was synthesized in vitro using rabbit reticulocyte lysate primed with RNA transcribed from the coding sequence of p1-88 using a bacteriophage T7 RNA polymerase/promoter system. P-450 IIC4 reacts with two monoclonal antibodies that recognize P-450 1 and exhibits the same relative electrophoretic mobility as P-450 1. In contrast, the reactivity of a third monoclonal antibody recognizing P-450 1, 1F11, toward P-450 IIC4 synthesized in vitro is greatly diminished. The latter antibody extensively inhibits hepatic progesterone 21-hydroxylase activity and recognizes phenotypic differences among rabbits in the microsomal concentration of P-450 1. This difference in the immunoreactivity of P-450 IIC4 and P-450 1 with the 1F11 antibody suggests that P-450 IIC4 does not contribute significantly to hepatic progesterone 21-hydroxylase activity. S1 nuclease mapping demonstrates that the expression of mRNAs corresponding to p1-88 are expressed to equivalent extents in rabbits exhibiting high and low expression of mRNAs corresponding to p1-8. Thus, P-450 1 differs from the protein encoded by p1-88, in its regulation, immunoreactivity, and by inference its catalytic properties although the amino acid sequences of P-450 1 and P-450 IIC4 are highly similar (congruent to 95%).     

Comparison between crude Interleukin-2 and recombinant Interleukin-2 in maintaining killing activity of cultured lymphocytes

Peripheral blood lymphocytes, regional lymph node lymphocytes or malignant effusion lymphocytes from cancer patients were incubated with crude IL-2 (cIL-2) for 13 days. These effectors, which frequently expressed IL-2 receptor (IL-2R), proliferated well and possessed augmented killing activity against fresh autologous tumor cells and K562. However, when recombinant IL-2 (rIL-2) was added for the last 4 days of culture instead of cIL-2, IL-2R expression and killing activity against fresh autologous tumor cells decreased significantly (P<0.05). Phenotypic analysis indicated that cIL-2 significantly promoted the expansion of the cytotoxic population (CD8⁺ .11b^–)(P<0.05). The decreases in killing activity and IL-2R expression were restored by 0.004% PHA plus rIL-2, but not in the presence of rIFN-, rIL-1, rIL-l, rIL-4 or rIL-6. PHA-free cIL-2 maintained killing activity, but not IL-2R expression.We conclude that some factors in cIL-2 and a low dose of PHA-P are necessary for the maintenance of killing activity and IL-2R expression of cultured lymphocytes in the late phase of culture.