Uptake,Transport and Storage of Cardenolides in Foxglove. Cardenolide Sinks and Occurrence of Cardenolides in the Sieve Tubes of Digitalis lanata1

Cardiac glycoside transport was investigated on the organ and whole plant level. Uptake experiments were carried out with shoot and root cultures of Digitalis lanata. In both systems primary cardenolides, i.e., those with a terminal glucose in their oligosaccharide side chain, were taken up against their concentration gradient, whereas the glucose-free secondary cardenolides were not. Active uptake of primary cardenolides was further evidenced by KCN inhibition of uptake. Using plantlets grown in vitro the long-distance transport of primary cardenolides from the leaves to the roots was demonstrated. Cardenolides were also detected in etiolated leaves, induced on plants with green leaves, which are supposed to be unable to synthezise cardenolides de novo, providing further evidence for long-distance transport. Several primary cardenolides were detected in the honeydew excreted by aphids fed on Digitalis lanata leaves, indicating that the phloem is a transporting tissue for cardenolides. On the other hand, the xylem sap obtained by applying the pressure-chamber technique was cardenolide-free. It was concluded that in Digitalis primary cardenolides serve as both the transport and the storage form of cardenolides. After their synthesis they are either stored in the vacuoles of the source tissue or loaded into the sieve tubes, from which they are unloaded at other sites where they are trapped in the vacuoles of the respective sink tissue.     

Design,synthesis and biological evaluation of 4-(pyridin-4-yloxy)benzamide derivatives bearing a 5-methylpyridazin-3(2H)-one fragment

A series of 4-(pyridin-4-yloxy)benzamide derivatives bearing a 5-methylpyridazin-3(2H)-one fragment were designed, synthesized, and evaluated for their biological activity. Most compounds showed effective inhibitory activity against cancer cell lines of A549, HeLa and MCF-7. Among them, the most promising compound 40 showed excellent activity against A549, HeLa and MCF-7 cell lines with IC₅₀ values of 1.03, 1.15 and 2.59 μM, respectively, which was 2.606.95 times more active than that of Golvatinib. The structure-activity relationships (SARs) showed that the introduction of 5-methylpyridazin-3(2H)-one to “5-atom linker” and the modification of the amide with morpholine group were beneficial for enhancing the inhibitory activity of compounds. In addition, the further research on compound 40 mainly include c-Met kinase activity, concentration dependence, apoptosis (acridine orange staining), and molecular docking.     

Phosphorylation of Cdc42 Effector Protein-4 (CEP4) by Protein Kinase C Promotes Motility of Human Breast Cells

Cdc42 effector protein-4 (CEP4) was recently identified by our laboratory to be a substrate of multiple PKC isoforms in non-transformed MCF-10A human breast cells. The significance of phosphorylated CEP4 to PKC-stimulated motility of MCF-10A cells was evaluated. Single site mutants at Ser residues embedded in potential PKC consensus sites (Ser¹⁸, Ser⁷⁷, Ser⁸⁰, and Ser⁸⁶) were individually replaced with Asp residues to simulate phosphorylation. Following expression in weakly motile MCF-10A cells, the S18D and S80D mutants each promoted increased motility, and the double mutant (S18D/S80D) produced a stronger effect. MS/MS analysis verified that Ser¹⁸ and Ser⁸⁰ were directly phosphorylated by PKCα in vitro. Phosphorylation of CEP4 severely diminished its affinity for Cdc42 while promoting Rac activation and formation of filopodia (microspikes). In contrast, the phosphorylation-resistant double mutant S18A/S80A-CEP4 blocked CEP4 phosphorylation and inhibited motility of MCF-10A cells that had been stimulated with PKC activator diacylglycerol lactone. In view of the dissociation of phospho-CEP4 from Cdc42, intracellular binding partners were explored by expressing each CEP4 double mutant from a tandem affinity purification vector followed by affinity chromatography, SDS-PAGE, and identification of protein bands evident only with S18D/S80D-CEP4. One binding partner was identified as tumor endothelial marker-4 (TEM4; ARHGEF17), a guanine nucleotide exchange factor that is involved in migration. In motile cells expressing S18D/S80D-CEP4, knockdown of TEM4 inhibited both Rac activation and motility. These findings support a model in which PKC-mediated phosphorylation of CEP4 at Ser¹⁸ and Ser⁸⁰ causes its dissociation from Cdc42, thereby increasing its affinity for TEM4 and producing Rac activation, filopodium formation, and cell motility.     

Single‐molecule force spectroscopy applied to heparin‐induced thrombocytopenia

Heparin‐induced thrombocytopenia (HIT), occurring up to approximately 1% to 5% of patients receiving the antithrombotic drug heparins, has a complex pathogenesis involving multiple partners ranging from small molecules to cells/platelets. Recently, insights into the mechanism of HIT have been achieved by using single‐molecule force spectroscopy (SMFS), a methodology that allows direct measurements of interactions among HIT partners. Here, the potential of SMFS in unraveling the mechanism of the initial steps in the pathogenesis of HIT at single‐molecule resolution is highlighted. The new findings ranging from the molecular binding strengths and kinetics to the determination of the boundary between risk and non‐risk heparin drugs or platelet‐surface and platelet‐platelet interactions will be reviewed. These novel results together have contributed to elucidate the mechanisms underlying HIT and demonstrate how SMFS can be applied to develop safer drugs with a reduced risk profile.     

Regulation of c-Myc Expression by Ahnak Promotes Induced Pluripotent Stem Cell Generation

We have previously reported that Ahnak-mediated TGFβ signaling leads to down-regulation of c-Myc expression. Here, we show that inhibition of Ahnak can promote generation of induced pluripotent stem cells (iPSC) via up-regulation of endogenous c-Myc. Consistent with the c-Myc inhibitory role of Ahnak, mouse embryonic fibroblasts from Ahnak-deficient mouse (Ahnak^−/− MEF) show an increased level of c-Myc expression compared with wild type MEF. Generation of iPSC with just three of the four Yamanaka factors, Oct4, Sox2, and Klf4 (hereafter 3F), was significantly enhanced in Ahnak^−/− MEF. Similar results were obtained when Ahnak-specific shRNA was applied to wild type MEF. Of note, expressionof Ahnak was significantly induced during the formation of embryoid bodies from embryonic stem cells, suggesting that Ahnak-mediated c-Myc inhibition is involved in embryoid body formation and the initial differentiation of pluripotent stem cells. The iPSC from 3F-infected Ahnak^−/− MEF cells (Ahnak^−/−-iPSC-3F) showed expression of all stem cell markers examined and the capability to form three primary germ layers. Moreover, injection of Ahnak^−/−-iPSC-3F into athymic nude mice led to development of teratoma containing tissues from all three primary germ layers, indicating that iPSC from Ahnak^−/− MEF are bona fide pluripotent stem cells. Taken together, these data provide evidence for a new role for Ahnak in cell fate determination during development and suggest that manipulation of Ahnak and the associated signaling pathway may provide a means to regulate iPSC generation.     

Effects of increasing saturation vapour pressure deficit on growth and ABA levels in black spruce and jack pine

 Plant responses to saturation vapour pressure deficit (SVPD) were studied by subjecting black spruce [Picea mariana (Mill) B.S.P.] and jack pine seedlings (Pinus banksiana Lamb.) to humid (0.3 – 0.8 kPa) or dry (2.0 – 2.5 kPa SVPD) regimes for 4 weeks using a computer-controlled environmental system to control diurnal variation in SVPD. Dry matter accumulation in needles was not altered by increasing SVPD. However, root growth declined by 60% which increased shoot to root ratio and reduced total seedling dry weight in both black spruce and jack pine. Relative growth rate of jack pine also declined to about half the rate of plants grown under humid conditions. In situ root marking studies showed that the decline in root growth of jack pine under the high SVPD was the result of reduced lateral root initiation, whereas root elongation was unaffected by humidity. A 4-week exposure to dry air increased abscisic acid (ABA) levels in needles, but not roots, of jack pine whereas ABA levels in black spruce were not altered. A short (3-day) exposure failed to increase needle ABA levels in either species. These results suggest that the responses of conifers to dry air were not the result of ABA accumulation. Received: 24 March 1996 / Accepted: 30 May 1996     

The antitumor agent 3-bromopyruvate has a short half-life at physiological conditions

Clinical research is currently exploring the validity of the anti-tumor candidate 3-bromopyruvate (3-BP) as a novel treatment for several types of cancer. However, recent publications have overlooked rarely-cited earlier work about the instability of 3-BP and its decay to 3-hydroxypyruvate (3-HP) which have obvious implications for its mechanism of action against tumors, how it is administered, and for precautions when preparing solutions of 3-BP. This study found the first-order decay rate of 3-BP at physiological temperature and pH has a half-life of only 77 min. Lower buffer pH decreases the decay rate, while choice of buffer and concentration do not affect it. A method for preparing more stable solutions is also reported.     

Isolation and characterization of the plasma membrane from the yeast Pichia pastoris

Despite similarities of cellular membranes in all eukaryotes, every compartment displays characteristic and often unique features which are important for the functions of the specific organelles. In the present study, we biochemically characterized the plasma membrane of the methylotrophic yeast Pichia pastoris with emphasis on the lipids which form the matrix of this compartment. Prerequisite for this effort was the design of a standardized and reliable isolation protocol of the plasma membrane at high purity. Analysis of isolated plasma membrane samples from P. pastoris revealed an increase of phosphatidylserine and a decrease of phosphatidylcholine compared to bulk membranes. The amount of saturated fatty acids in the plasma membrane was higher than in total cell extracts. Ergosterol, the final product of the yeast sterol biosynthetic pathway, was found to be enriched in plasma membrane fractions, although markedly lower than in Saccharomyces cerevisiae. A further characteristic feature of the plasma membrane from P. pastoris was the enrichment of inositol phosphorylceramides over neutral sphingolipids, which accumulated in internal membranes. The detailed analysis of the P. pastoris plasma membrane is discussed in the light of cell biological features of this microorganism especially as a microbial cell factory for heterologous protein production.     

Immunopathological Changes in the Brain of Immunosuppressed Mice Experimentally Infected with Toxocara canis

Toxocariasis is a soil-transmitted helminthozoonosis due to infection of humans by larvae of Toxocara canis. The disease could produce cognitive and behavioral disturbances especially in children. Meanwhile, in our modern era, the incidence of immunosuppression has been progressively increasing due to increased incidence of malignancy as well as increased use of immunosuppressive agents. The present study aimed at comparing some of the pathological and immunological alterations in the brain of normal and immunosuppressed mice experimentally infected with T. canis. Therefore, 180 Swiss albino mice were divided into 4 groups including normal (control) group, immunocompetent T. canis-infected group, immunosuppressed group (control), and immunosuppressed infected group. Infected mice were subjected to larval counts in the brain, and the brains from all mice were assessed for histopathological changes, astrogliosis, and IL-5 mRNA expression levels in brain tissues. The results showed that under immunosuppression, there were significant increase in brain larval counts, significant enhancement of reactive gliosis, and significant reduction in IL-5 mRNA expression. All these changes were maximal in the chronic stage of infection. In conclusion, the immunopathological alterations in the brains of infected animals were progressive over time, and were exaggerated under the effect of immunosuppression as did the intensity of cerebral infection.