Retention of survivors of acute lymphoblastic leukemia in a longitudinal study of bone mineral density

Attrition in longitudinal studies of survivors of childhood cancer reduces these studies' statistical power, introduces bias and threatens internal and external validity. This study investigated the variables associated with dropout of survivors of acute lymphoblastic leukemia in a trial investigating the effect of vitamin D and calcium supplementation and nutritional counseling on bone mineral density (BMD). Twenty-five participants withdrew from the study. Common reasons given for withdrawing were intolerance of the study drug, family hardship and schedule conflicts. Few statistically and clinically significant differences identified participants who completed the study. Nurses need to be aware of the reasons that participants withdraw from clinical trials, as they are in a strategic position to encourage patients to participate in health promotion studies.

Efficient CO Oxidation at Low Temperature on Au(111)

The rate of CO oxidation to CO2 depends strongly on the reaction temperature and characteristics of the oxygen overlayer on Au(111). The factors that contribute to the temperature dependence in the oxidation rate are (1) the residence time of CO on the surface, (2) the island size containing Au-O complexes, and (3) the local properties, including the degree of order of the oxygen layer. Three different types of oxygen--defined as chemisorbed oxygen, a surface oxide, and a bulk oxide--are identified and shown to have different reactivity. The relative populations of the various oxygen species depend on the preparation temperature and the oxygen coverage. The highest rate of CO oxidation was observed for an initial oxygen coverage of 0.5 monolayers that was deposited at 200 K where the density of chemisorbed oxygen is maximized. The rate decreases when two-dimensional islands of the surface oxide are populated and further decreases when three-dimensional bulk gold oxide forms. Our results are significant for designing catalytic processes that use Au for CO oxidation, because they suggest that the most efficient oxidation of CO occurs at low temperature--even below room temperature--as long as oxygen could be adsorbed on the surface.

Progress in parasitic plant biology: host selection and nutrient transfer

Host range varies widely among species of parasitic plants. Parasitic plants realize host selection through induction by chemical molecular signals, including germination stimulants and haustoria-inducing factors (HIFs). Research on parasitic plant biology has provided information on germination, haustorium induction, invasion, and haustorial structures and functions. To date, some molecular mechanisms have been suggested to explain how germination stimulants work, involving a chemical change caused by addition of a nucleophilic protein receptor, and direct or indirect stimulation of ethylene generation. Haustorium initiation is induced by HIFs that are generated by HIF-releasing enzymes from the parasite or triggered by redox cycling between electrochemical states of the inducers. Haustorium attachment is non-specific, however, the attachment to a host is facilitated by mucilaginous substances produced by haustorial hairs. Following the attachment, the intrusive cells of parasites penetrate host cells or push their way through the host epidermis and cortex between host cells, and some types of cell wall-degrading enzymes may assist in the penetration process. After the establishment of host-parasite associations, parasitic plants develop special morphological structures (haustoria) and physiological characteristics, such as high transpiration rates, high leaf conductance, and low water potentials in hemiparasites, for nutrient transfer and resource acquisition from their hosts. Therefore, they negatively affect the growth and development and even cause death of their hosts.

Telomerase activation by Epstein-Barr virus latent membrane protein 1 is associated with c-Myc expression in human nasopharyngeal epithelial cells

Latent membrane protein 1 (LMP1), one of the oncoproteins encoded by Epstein-Barr virus is sufficient for the development of nasopharyngeal carcinoma in vivo and nasopharyngeal epithelial cellular immortalization in vitro. It has also been shown to increase the telomerase activity in primary human nasopharyngeal epithelial cells by an unknown mechanism. We reported here that LMP1 could increase telomerase activity in coordination with LMP1-induced c-Myc expression in LMP1-transfected primary human nasopharyngeal epithelial cells or in a dual-stable LMP1 integrated nasopharyngeal carcinoma cell line with Tet-on regulatory system, named Tet-on-LMP1 HNE2 by PCR-ELISA analysis and reporter gene assay. Blocking of LMP1 expression decreased telomerase activity and c-myc transactivation. Mutagenesis of Myc-responsive E-box elements in the minimal core of hTERT promoter could inhibit the hTERT expression induced by LMP1. Moreover, blocking of c-myc transactivation could further decrease LMP1-mediated hTERT expression. It has been suggested that LMP1 can be used to aid myc control telomerase. In addition, we also found that C-terminus of LMP1, including CTAR1 and CTAR2 domains participated in telomerase activation. Together, these findings suggested that LMP1 activated telomerase via c-myc.

Locomotor activity and behavior of mutant mice deleted for gastrin gene expression

The current studies were initiated to investigate the role of brain-gut peptide, gastrin, on locomotor activity and anxiety-like behavior. Young, male mutant mice, lacking gastrin gene expression (GAS-KO mice), were used in the experiments. The locomotor activity of GAS-KO vs wild type (WT) mice was compared by open field test. The anxiety-like behavior was examined using elevated plus maze. The time and entries to the open arms of the elevated plus maze were used as an indicator for the anxiety-like behavior and the data were analyzed using Hindsight program. On the open field test, locomotor activity of GAS-KO mice was similar to that of the WT mice for the first 10 min of the test, but decreased significantly after that. Anxiety-like behavior was more evident in the GAS-KO vs WT mice in the elevated plus maze experiments. The number of entries to and time spent on the open arms of plus-maze were significantly reduced for the GAS-KO vs WT mice suggesting an increased anxiety-like behavior of GAS-KO mice. Our studies suggest that normal circulating levels of gastrins may play a direct or indirect role in the regulation of locomotor activity and anxiety-like behavior.

Regulation of Bcl2 phosphorylation and potential significance for leukemic cell chemoresistance

Although considered tightly linked, the linkage effectors for proliferation and antiapoptotic signaling pathways are not clear. Phosphorylation of Bcl2 at serine 70 is required for suppression of apoptosis in interleukin 3 (IL-3)-dependent myeloid cells deprived of IL-3 or treated with antileukemic drugs and can result from agonist activation of mitochondrial protein kinase C alpha (PKCalpha). However, we have recently found that high concentrations of staurosporine up to 1 microM: can only partially inhibit IL-3-stimulated Bcl2 phosphorylation but completely block PKCalpha-mediated Bcl2 phosphorylation in vitro, indicating the existence of a non-PKC, staurosporine-resistant Bcl2 kinase (SRK). Although the RAF-1MEK-1-mitogen-activated protein kinase (MAPK) cascade is required for factor-dependent mitogenic signaling, a direct role in antiapoptosis signaling is not clear. In particular, the role of phosphorylation in the regulation of death substrates is not yet clear. Our findings indicate a potential role for the MEK/MAPK pathway in addition to PKC in antiapoptosis signaling, involving Bcl2 phosphorylation that features a role for extracellular signal-regulated kinase (ERK)1 and 2 as SRKs. These findings indicate a novel role for ERK1 and 2 as molecular links between proliferative and survival signaling and may, at least in part, explain the apparent paradox by which Bcl2 may suppress staurosporine-induced apoptosis. Although the effect of phosphorylation on Bcl2 function is not clear, effector molecules that regulate Bcl2 phosphorylation may have clinical significance in patients with acute myelogenous leukemia (AML) who express detectable levels of Bcl2. Preliminary findings suggest that expression of PKCalpha, ERK2, and Bax in leukemic blast cells from patients with AML, although individually not prognostic, appears to have potential clinical value in predicting chemoresistance and survival outcomes.

Bioaccumulation of nickel from aqueous solutions by genetically engineered Escherichia coli

This study constructed a genetically engineered Escherichia coli JM109 which simultaneously expressed nickel transport system and metallothionein to remove and recover Ni(2+) from aqueous solution. Bioaccumulation process was rapid and followed linearized Langmuir isotherm. A more than six-fold increase of Ni(2+) binding capacity was obtained by genetically engineered E. coli cells compared with original host E. coli cells. A pH assay showed genetically engineered E. coli cells accumulated Ni(2+) effectively over a broad range of pH (4-10). The presence of 1000 mg/L Na(+) and Ca(2+), or 50mg/L Cd(2+) or Pb(2+) did not have a significant effect on Ni(2+) bioaccumulation, while Mg(2+), Hg(2+) and Cu(2+) posed a severe adverse influence on Ni(2+) uptake by genetically engineered E. coli. Furthermore, genetically engineered E. coli cells did not require extra nutrients for Ni(2+) bioaccumulation.

Computational and experimental studies of the catalytic mechanism of Thermobifida fusca cellulase Cel6A (E2)

Mutagenesis experiments suggest that Asp79 in cellulase Cel6A (E2) from Thermobifida fusca has a catalytic role, in spite of the fact that this residue is more than 13 A from the scissile bond in models of the enzyme-substrate complex built upon the crystal structure of the protein. This suggests that there is a substantial conformational shift in the protein upon substrate binding. Molecular mechanics simulations were used to investigate possible alternate conformations of the protein bound to a tetrasaccharide substrate, primarily involving shifts of the loop containing Asp79, and to model the role of water in the active site complex for both the native conformation and alternative low-energy conformations. Several alternative conformations of reasonable energy have been identified, including one in which the overall energy of the enzyme-substrate complex in solution is lower than that of the conformation in the crystal structure. This conformation was found to be stable in molecular dynamics simulations with a cellotetraose substrate and water. In simulations of the substrate complexed with the native protein conformation, the sugar ring in the -1 binding site was observed to make a spontaneous transition from the (4)C(1) conformation to a twist-boat conformer, consistent with generally accepted glycosidase mechanisms. Also, from these simulations Tyr73 and Arg78 were found to have important roles in the active site. Based on the results of these various MD simulations, a new catalytic mechanism is proposed. Using this mechanism, predictions about the effects of changes in Arg78 were made which were confirmed by site-directed mutagenesis.

Gut barrier permeability, reticuloendothelial system function and protease inhibitor levels following intestinal ischaemia and reperfusion--effects of pretreatment with N-acetyl-L-cysteine and indomethacin

BACKGROUND

Pathophysiological mechanisms and ways to intervene on intestinal barrier dysfunction following small intestinal ischaemia and prolonged reperfusion are still not fully clarified.

AIMS

To evaluate the effect of oxygen free radical and prostaglandin inhibition on intestinal barrier injury following intestinal ischaemia/reperfusion.

METHODS

Endothelial and epithelial barrier permeability was evaluated by clearance of radiolabelled albumin. Parameters included 125I-Escherichia coli uptake rate index, host reticuloendothelial system function and organ distribution, as well as protease inhibitor and proenzyme activities in rats subjected to small intestinal ischaemia for 40 minutes followed by 12 hours reperfusion (ischaemia/reperfusion), pretreated with N-acetyl-L-cysteine or indomethacin.

RESULTS

Following ischaemia/reperfusion, endothelial and epithelial permeability increased, reticuloendothelial system activation occurred and plasma protease inhibitors were consumed. N-acetyl-L-cysteine pretreatment resulted in improved endothelial and epithelial barrier integrity, a decrease in protease inhibitor consumption and less pronounced reticuloendothelial system activation. Pretreatment with indomethacin was not effective.

CONCLUSION

Oxygen free radicals seem to play an important role in the development of intestinal barrier impairment following ischaemia/reperfusion. N-acetyl-L-cystine may be a potential agent for preventing ischaemia/reperfusion damage.