Activity of pp60c-src in 60 different cell lines derived from human tumors

The activity of the protein tyrosine kinase pp60c-src was determined for each of the 60 human cell lines in the panel used by the National Cancer Institute for the random screening of potential anticancer drugs. The leukemia, lymphoma, melanoma, and small-cell lung cancer derived cell lines had low pp60c-src activity. Surprisingly, non-small-cell lung and ovarian cell lines had a median pp60c-src activity which was greater than that of the panel of cells representing colon cancer, which is most often associated with elevated pp60c-src activity. This data defines homologous cell lines which contain low and high pp60c-src activity which will aid attempts to understand the role of this enzyme in human cancer.

Activation of phosphatidylinositol-3 kinase by ligation of the interleukin-7 receptor is dependent on protein tyrosine kinase activity

Ligation of the interleukin-7 receptor (IL-7R) results in a rapid phosphorylation of tyrosine residues on multiple substrates. In addition, we have recently shown that the IL-7R mediates activation of phosphatidylinositol-3 (PI-3) kinase. Because PI-3 kinase activity can be immunoprecipitated with antiphosphotyrosine antibodies in most receptor systems studied, it has been examined that either PI-3 kinase or an associated protein become tyrosine-phosphorylated after ligand binding. We studied here the possibility that PI-3 kinase, which is directly linked to mitogenic responses in growth factor receptors, is tyrosine-phosphorylated after stimulation of the IL-7R. Using anti-p85 alpha or anti-p85 beta antibodies raised against the p85 subunit of PI-3 kinase for immunoprecipitation and subsequent blotting with antiphosphotyrosine clearly shows that IL-7-stimulated human precursor cells contain both p85 alpha and p85 beta proteins phosphorylated on tyrosine residues. Specific protein tyrosine kinase inhibitors such as tyrphostin AG-490 block total cell lysate phosphorylation and tyrosine phosphorylation on p85. Similar concentrations of this inhibitor also block in vitro and in vivo PI-3 kinase activity suggesting that this enzyme activation is dependent on the phosphorylation event of p85. In addition, AG-490 blocks IL-7-mediated proliferation in a dose-dependent manner, suggesting a link between the early events of PI-3 kinase phosphorylation and activation with IL-7R-induced cell growth.

Recombinant pp60c-src from baculovirus-infected insect cells: purification and characterization

A simple and effective method has been developed to purify the recombinant protein tyrosine kinase pp60c-src from a baculovirus-insect cell expression system. The procedure includes affinity chromatography and HPLC. Milligram quantities of protein have been isolated with an activity of 3.9 mumol/min/mg protein using the substrate poly E4Y. This specific activity is many times higher than any published protocol. The enzyme is stable for months when stored in buffered 10% glycerol at -70 degrees C. This purification technique is compared to the immuno-affinity technique which is widely used for this enzyme. Enzyme kinetics were characterized with respect to substrate specificity, the effect of temperature, ionic strength, pH, and Mg+2 versus Mn+2 ions. Similar to the enzyme expressed in human cells, the recombinant enzyme demonstrated a higher Vmax and substrate specificity for poly E4Y over 5V-Agt-II. An activation energy of 14.2 kcal/mol was determined. Inhibition by increasing ionic strength is mostly due to an increase in Km for the poly E4Y substrate and hence was substrate dependent. The Km(ATP) was pH dependent while the Km(poly E4Y) was pH independent. For the phosphorylation of poly E4Y, free Mg+2 was stimulatory while Mn+2 was inhibitory. In contrast, Mn+2 stimulated the phosphorylation of 5V-Agt-II.

CD19 is a substrate of the antigen receptor-associated protein tyrosine kinase in human B cells

The B cell antigen receptor, mIg, is part of a multimolecular complex including Ig alpha, Ig beta, and CD19. We provide evidence here that upon ligation of mIg CD19 becomes phosphorylated on tyrosine residues. Further, protein tyrosine kinase lyn, which is activated by the antigen receptor, can be readily co-immunoprecipitated with CD19 suggesting this is the enzyme responsible for the antigen receptor mediated tyrosine phosphorylation of CD19.

Interleukin 7 receptor mediates the activation of phosphatidylinositol-3 kinase in human B-cell precursors

Interleukin 7 appears to be central to promoting growth and differentiation of lymphocyte precursors. Pro-B cells, as well as pre-pre-B cells, but not mature cells express the IL-7 receptor suggesting an important role for IL-7 during these early stages of B cell maturation. Indeed, IL-7 was shown to promote not only growth but also immunoglobulin gene rearrangement in these cells. However, the mechanism by which IL-7 receptor transduces these growth signals remains elusive. In an attempt to characterize a pathway of signal transduction via the IL-7 receptor, we have demonstrated here that ligation of the IL-7 receptor is associated with increased activity of PI-3 kinase. PI-3 kinase products were detected by TLC and their identity confirmed by HPLC. Further, by in vivo labeling intact cells we have shown that IL-7 receptor mediates the activation of PI-3 kinase.

Somatic embryogenesis and plant regeneration in Acanthopanax senticosus

Mature embryos of Acanthopanax senticosus explanted on Murashige and Skoog (MS) medium with 0.5 mg/1 2,4-D developed somatic embryos directly from swollen cotyledon and embryo axes within one to two months. When the somatic embryos were transferred to medium supplemented with 2,4-D (0.5 mg/1) or IAA (1-3 mg/1) or Zeatin (0.5 mg/1) and NAA (0.2 mg/1), additional somatic embryos developed. Most (93%) embryos germinated on the above medium without 2,4-D. Sixty-two percent of the plantlets survived in soil. Histological observations revealed that the somatic embryos originated from cell masses of epidermal and sub-epidermal origin. There was no cytological separation zone between the somatic embryos and cultured expiants. Consequently, embryos were difficult to separate from their expiant tissue.

[A study on the serological effects of newborn babies using China made 50 micrograms hepatitis B vaccine]

The blood source Hepatitis B vaccine produced by Beijing Institute of Biological Products was given to New born babies. The procedure and doses are as follows: first dose 30 micrograms was given within 24 hours after birth; second dose 10 micrograms was given one month after birth and the third dose 10 micrograms was given 6 months after birth. The sera samples were collected during 1-6 months after 3 times of inoculation. And tested HBsAg, anti-HBs and anti-HBc by using Solid-phase Radioimmunoassay (SPRIA). In total, 288 sera samples were tested. All samples were negative in HBsAg; Positive rate of anti-HBs was 96.18%, geometric titer was 1105.14 mIU/m. The results showed that the China made 50 micrograms Hepatitis B vaccine has a good serological effect on newborn babies.