Investigation of the aluminium biokinetics in humans: a 26Al tracer study

Despite the well-known toxicity of aluminium in chronic renal failure, a solid database on its biokinetics has been difficult to establish. A highly sensitive method using (26)Al as tracer and accelerator mass spectrometry (AMS) for detection was used. No perturbing background and saturation effects were taken into account using a delta function input of aluminium in time. Aluminium absorption, distribution, speciation and excretion in six healthy volunteers and in two patients with chronic renal failure were investigated following administration of a single oral or i.v. dose of (26)Al. Serial samples of blood and urine were taken. In a speciation study, the time dependence of the binding of (26)Al to low-molecular weight molecules in serum was investigated. The measured data were compared and interpreted with simulations in an open compartmental model. Fractional absorption, distribution, excretion and time constants for the aluminium transport were determined. Typical intestinal absorption rates for AlCl(3) were found to be in the range of 10(-3). The ultrafiltrable percentage of aluminium in serum of one volunteer was estimated to be 5.6+/-0.8%. Differences between healthy volunteers and patients with chronic renal failure were deduced. The employed method using (26)Al and ams has proven to be highly sensitive for investigations of aluminium biokinetics at the ultra-trace element level. With the model, the measured values of (26)Al in serum and urine were used to precisely determine absorption, speciation, distribution, retention and excretion of aluminium in humans.

Identification of (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate as a major activator for human gammadelta T cells in Escherichia coli

The gcpE and lytB gene products control the terminal steps of isoprenoid biosynthesis via the 2-C-methyl-D-erythritol 4-phosphate pathway in Escherichia coli. In lytB-deficient mutants, a highly immunogenic compound accumulates significantly, compared to wild-type E. coli, but is apparently absent in gcpE-deficient mutants. Here, this compound was purified from E. coli DeltalytB mutants by preparative anion exchange chromatography, and identified by mass spectrometry, (1)H, (13)C and (31)P NMR spectroscopy, and NOESY analysis as (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP). HMB-PP is 10(4) times more potent in activating human Vgamma9/Vdelta2 T cells than isopentenyl pyrophosphate.

Cell-based delivery of cytokines allows for the differentiation of a doxycycline inducible oligodendrocyte precursor cell line in vitro

BACKGROUND

Stem cells, having the property of self renewal, offer the promise of lifelong repair of damaged tissue. However, somatic tissue-committed primary stem cells are rare and difficult to expand in vitro. Genetically modified stem-like cells with the ability to expand conditionally provide a valuable tool with which to study stem cell biology, especially the cellular events of proliferation and differentiation. In addition, stem cells may be appropriate candidates for therapeutic applications.

METHODS

Double transgenic mice possesing SV40 T antigen (Tag) under the control of the reverse tetracycline-transactivator (rtTA) were used to establish cell lines. One brain cell line was partially characterized by DNA sequencing, morphology, antigen expression using flow cytometry, confocal microscopy, and electrophysiology using the patch clamp technique. Cell cycle analysis was performed using propidium iodide staining; cell viability and H3-thymidine incorporation assays. The ability of this cell line to differentiate was assessed by confocal microscopy following co-culture with stem cells secreting cytokines.

RESULTS

We report here the establishment and partial characterization of a cell line derived from the brain tissue of rtTA-SV40 Tag transgenic mice. Analysis of the morphology and antigen markers has shown that this cell line mimics some aspects of primary glial precursors. The results of electrophysiology are consistent with this and suggest that the cell line is derived from O2A glial precursor cells. Cell cycle progression of this cell line is doxycycline-dependent. In the absence of doxycycline, cells become apoptotic. Differentiation into mature type 2 astrocytes and (precursor) oligodendrocytes can be induced upon withdrawal of doxycycline and addition of epithelial stem cells secreting cytokine, such as hIL3 (human Interleukine 3) or hIL6 to the culture. In contrast, co-culturing with hCNTF (human Ciliary NeuroTrophic Factor)-secreting epithelial stem cells did not induce them to mature into progeny cell types.

CONCLUSION

The differentiation of this O2A glial precursor line does not occur automatically in culture. Additional external help is required from the cell-based delivery of appropriate transgenic cytokines. Withdrawal of doxycycline from the culture medium removes the proliferation signals and induces a fatal outcome.

Activation of spinach pullulanase by reduction results in a decrease in the number of isomeric forms

Spinach starch debranching enzyme, a limit dextrinase or pullulanase (EC 3.2.1.41), is a monomeric protein of 100 kDa that produces up to seven coexisting and mutually interconvertible isomers of different specific activity, a phenomenon that has been termed microheterogeneity and for which a structural explanation has not yet been presented. The enzyme can be activated by reduction, in particular by thiol reagents, and inactivated by oxidation and the concomitant change of the patterns of its isomeric forms could be quantified by chromatofocusing. The hypothesis was examined that reduction of the enzyme's thiol groups shifts the isomer pattern towards the forms with a higher specific activity while oxidation favours the less active forms. Using TCEP as reductant only the form with the highest specific activity was obtained. This form was almost inaccessible for proteolysis by trypsin while the oxidized and GSH-activated enzyme yielded four peptides when treated with trypsin. Their sequence indicated cleavage predominantly of loops connecting the beta-strands and alpha-helices of the (beta/alpha)(8)-barrel which forms the catalytic site of the pullulanase. Formation of various disulphide bridges between the loops connecting the barrel structures -- predominantly on one side -- may be the reason for the microheterogeneity of the spinach pullulanase. In vivo, the enzyme maintains its activated state due to the high concentration of GSH in the chloroplast. However, the chloroplast's pH shifts from day (pH 8) to night (pH 7) and thus could also alter the activity of the protein in accordance with the required function in starch metabolism.

LytB, a novel gene of the 2-C-methyl-D-erythritol 4-phosphate pathway of isoprenoid biosynthesis in Escherichia coli

The mevalonate-independent 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway for isoprenoid biosynthesis is essential in many eubacteria, plants, and the malaria parasite. Using genetically engineered Escherichia coli cells able to utilize exogenously provided mevalonate for isoprenoid biosynthesis by the mevalonate pathway we demonstrate that the lytB gene is involved in the trunk line of the MEP pathway. Cells deleted for the essential lytB gene were viable only if the medium was supplemented with mevalonate or the cells were complemented with an episomal copy of lytB.

GcpE is involved in the 2-C-methyl-D-erythritol 4-phosphate pathway of isoprenoid biosynthesis in Escherichia coli

In a variety of organisms, including plants and several eubacteria, isoprenoids are synthesized by the mevalonate-independent 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. Although different enzymes of this pathway have been described, the terminal biosynthetic steps of the MEP pathway have not been fully elucidated. In this work, we demonstrate that the gcpE gene of Escherichia coli is involved in this pathway. E. coli cells were genetically engineered to utilize exogenously provided mevalonate for isoprenoid biosynthesis by the mevalonate pathway. These cells were then deleted for the essential gcpE gene and were viable only if the medium was supplemented with mevalonate or the cells were complemented with an episomal copy of gcpE.

Diaryl ester prodrugs of FR900098 with improved in vivo antimalarial activity

The fosmidomycin derivative FR900098 represents an inhibitor of the 1-deoxy-D-xylulose 5-phosphate (DOXP) reductoisomerase with potent antimalarial activity. Prodrugs of FR900098 with increased activity after oral administration were obtained by chemical modification of the phosphonate moiety to yield phosphodiaryl esters. One diaryl ester prodrug demonstrated efficacy in mice infected with the rodent malaria parasite Plasmodium vinckei comparable to i.p. drug administration.

Cutting edge: human gamma delta T cells are activated by intermediates of the 2-C-methyl-D-erythritol 4-phosphate pathway of isoprenoid biosynthesis

Activation of V gamma 9/V delta 2 T cells by small nonprotein Ags is frequently observed after infection with various viruses, bacteria, and eukaryotic parasites. We suggested earlier that compounds synthesized by the 2-C:-methyl-D-erythritol 4-phosphate (MEP) pathway of isopentenyl pyrophosphate synthesis are responsible for the V gamma 9/V delta 2 T cell reactivity of many pathogens. Using genetically engineered Escherichia coli knockout strains, we now demonstrate that the ability of E. coli extracts to stimulate gamma delta T cell proliferation is abrogated when genes coding for essential enzymes of the MEP pathway, dxr or gcpE, are disrupted or deleted from the bacterial genome.

Predictors of depression in a sample of African-American homeless men: identifying effective coping strategies given varying levels of daily stressors

In a sample of African-American, homeless or insecurely sheltered men, the occurrence of discrete stressors in the prior week contributed to the experience of depressive symptoms among this generally stressed population. Reliance on active, problem-focused coping strategies as opposed to emotion-coping strategies was associated with lower levels of depressive symptoms contradicting the hypothesis that active coping is counter-productive for African-American men. However, depressive symptoms increased, with added uncontrollable stress, even for active copers, contradicting a stress-buffering hypothesis. Under conditions of high uncontrollable stress, problem-focused coping was associated with lower levels of depressive symptoms than emotion-focused coping, however, additional discrete stressors exerted less impact on the level of depressive symptoms among the emotion-focused copers than the active, problem-focused copers.

Compartmental model for aluminium biokinetics

An open compartmental model for describing aluminium biokinetics is presented with a central compartment consisting of transferrin- and citrate-bound aluminium in blood plasma and interstitial fluid, and three peripheral compartments for organs, muscles and bones and the gastro-intestinal tract. The rate constants describing the transport of aluminium are normalized to an estimated plasma volume and do not depend on the size of the individual. Effects due to changes in compartmental sizes or to transport characteristics are described. The model is applied to biokinetics studies of a volunteer after i.v. administration and of Sprague-Dawley rats with different iron status and with nephrectomization after p.o. administration of 26Al.

Translation from the internal ribosome entry site of bovine viral diarrhea virus is independent of the interaction with polypyrimidine tract-binding protein

Translation of the pestiviral polyprotein is initiated cap independently at an internal site of the viral RNA, the internal ribosome entry site (IRES). We investigated the translation from the IRES of bovine viral diarrhea virus (BVDV) and the possible interaction of the unconventional cellular RNA-binding proteins, particularly of polypyrimidine tract-binding protein (PTB). The BVDV IRES is translationally active in rabbit reticulocyte lysate (RRL), and it is translated most efficiently at low concentrations of Mg(2+)- and K(+)-ions. In the UV cross-link assay, several proteins from RRL bind to the BVDV IRES, including proteins of 50, 65 and 72kDa, but no protein of 57kDa possibly corresponding to PTB, although PTB is endogenously present in RRL. However, the BVDV IRES can bind PTB weakly under certain conditions. Interestingly, in a functional depletion and add-back translation system, PTB does not enhance translation of BVDV, although PTB enhances translation of a picornavirus in this translation stimulation assay. These results indicate that PTB can bind the BVDV IRES RNA, but translation is independent of the action of PTB.

What proportion of dyspeptic patients having H. pylori breath test subsequently undergo endoscopy?

BACKGROUND

Helicobacter pylori (HP) testing in young patients with uncomplicated dyspepsia has been recommended. A test and treat strategy for dyspeptics positive for HP is recommended by the European H. pylori Study Group and the American Gastroenterology Association.

OBJECTIVES

To assess the rates of re-referral for upper GI endoscopy (OGD) and outpatient (OPD) attendance in uncomplicated dyspeptic patients following assessment of HP status.

METHODS

190 patients under 50 years of age with uncomplicated dyspepsia (without alarm symptoms) referred from general practitioners (GPs) to the gastroenterology department underwent HP urea breath test (UBT). GPs were informed of the results of UBT and recommended eradication therapy if positive, and if negative advised symptomatic treatment with an acid suppressant with/without a prokinetic. The patients were analysed for subsequent attendance at OGD or OPD in the following two years.

RESULTS

HP was present in 93 of 190 patients. Twenty of 190 (10.5%) patients subsequently were re-referred and underwent OGD for continuing dyspeptic symptoms; a further 6 were seen in OPD but not endoscoped as they have been judged to have uncomplicated gastro-oesophageal reflux disease. At time of OGD all patients were negative on Campylobacter-like organism (CLO) test for HP. Findings at OGD were normal (9), hiatus hernia (6), gastritis (4) and duodenitis (1). No case of peptic ulcer disease or gastric cancer has been identified.

CONCLUSIONS

In this group of dyspeptic patients, adopting a test and treat policy after initial analysis of HP resulted in 10.5% being re-referred for subsequent OGD; findings in those endoscoped were normal or minimal. A test and treat strategy for H. pylori in uncomplicated dyspeptics therefore saves endoscopies and outpatient consultations without missing significant underlying pathology.

CA 125 elevations in patients with malignant lymphomas

Circulating CA 125 serum levels were measured in 60 patients with several hematological malignancies. Using 35 U/ml as cutoff level, elevated CA 125 concentrations were found in 3 of 18 patients with acute leukemia, 1 of 5 patients with chronic myelocytic leukemia, 2 of 9 patients with Hodgkin's lymphoma and in 14 of 28 patients with non-Hodgkin's lymphoma. None of the healthy control group had CA 125 serum levels above 35 U/ml. In patients with malignant lymphoma, elevated CA 125 serum concentrations were associated with abdominal involvement (p < 0.01). 15 of 19 patients with abdominal tumor masses had CA 125 concentrations above 35 U/ml, but only 1 of 18 patients with supradiaphragmatic involvement. Serial determinations of CA 125 were performed in 3 patients with malignant lymphoma during chemotherapy. Disease regression was associated with decreasing CA 125 serum levels. Thus, CA 125 may be a useful indicator of abdominal involvement in patients with malignant lymphoma. Moreover, serial CA 125 measurement may be of value in monitoring response to chemotherapy in these patients.

Tools for discovery of inhibitors of the 1-deoxy-D-xylulose 5-phosphate (DXP) synthase and DXP reductoisomerase: an approach with enzymes from the pathogenic bacterium Pseudomonas aeruginosa

Two Pseudomonas aeruginosa genes encoding the enzymes 1-deoxy-D-xylulose 5-phosphate (DXP) synthase and DXP reductoisomerase, both involved in the mevalonate-independent biosynthesis of isoprenoids, have been expressed as recombinant enzymes in Escherichia coli. The purified P. aeruginosa DXP reductoisomerase was inhibited by submicromolar concentrations of the antibiotics fosmidomycin and FR-900098 in a well established method. A novel and convenient spectrophotometric assay was developed to determine activity and inhibition of P. aeruginosa DXP synthase. Fluoropyruvate is described as a first inhibitor of DXP synthase.

Improvement of a serodiagnostic strategy for foot-and-mouth disease virus surveillance in cattle under systematic vaccination: a combined system of an indirect ELISA-3ABC with an enzyme-linked immunoelectrotransfer blot assay

Foot-and-mouth disease (FMD) recombinant non-capsideal viral antigens 3A, 3B, 2C, 3D and 3ABC were assessed individually in an indirect enzyme-linked immunosorbent assay (I-ELISA) for their ability to screen for persistent infection-specific antibodies in cattle, regardless of vaccination condition. Results of sequential serum samples from non-vaccinated animals with experimentally induced persistent infection, and their correlation with virus isolation, indicated that the polypeptides 3A, 3B and 3ABC showed the most adequate characteristics for further field studies. Reliable performance of the I-ELISA with the selected antigen 3ABC was indicated by the distinct patterns observed for the frequency distribution values of naive and true positive samples. For regularly vaccinated livestock, a clear negative profile was proved in samples from regions without recent history of FMD. In contrast, at 90 and 900 days post-outbreak, coexistence of a positive and a negative population was established. These findings indicated that, irrespective of vaccination, the test allowed a classification of the herd-disease status. A high degree of agreement was observed between I-ELISA-3ABC and EITB results for clearly reactive and non-reactive sera. For samples with reactivity values close to that of the cut-off, the EITB profiles upheld the definition of the infection condition. On this basis, screening by I-ELISA-3ABC, together with confirmation of suspect or positive samples by EITB is proposed as an adequate and accurate approach for large-scale epidemiological surveillance.

IL-18 potentiates the adjuvant properties of IL-12 in the induction of a strong Th1 type immune response against a recombinant antigen

Due to the synergistic effects of IL-12 and IL-18, and to their importance in establishing a Th1 type immune response, we investigated the potential of a combined administration of both cytokines as an adjuvant for recombinant antigens. As a model system, we used a schistosome T cell antigen recently identified in our group. By co-adsorption of this antigen on alum in the presence of IL-12 and IL-18, we demonstrate that IL-18 enhances the effects of IL-12 in inducing an antigen-specific Th1 type CD4(+) T cell response as well as high titres of IgG1, IgG2a, and IgG2b antibodies.

Molecular characterization of a Litomosoides sigmodontis protein involved in the development of the microfilarial sheath during embryogenesis

A cDNA clone Ls110 was isolated from a female Litomosoides sigmodontis expression library using an antiserum raised against the microfilarial sheath. The complete cDNA encodes a protein (Ls110) of 382 amino acids. Southern and PCR analyses revealed the presence of Ls110 in L. sigmodontis as a single copy gene. The transcription of the Ls110 gene was limited to female worms. In these worms the transcription was confined to the epithelial cells of the uterus. The protein Ls110 was detected not only in the epithelial layer of the uterus but also secreted in the lumen of the uterus. All the intra-uterine embryonic stages showed the protein bound to their egg shell/sheath, except the early multicellular embryonic stages and fully developed microfilariae. The transient occurrence of Ls110 on these structures of intra-uterine stages besides the presence of a cysteine-rich N-terminal region (SXC-like domain) suggest that the protein may play a role in the formation of the microfilarial sheath during embryogenesis.

Growth, ageing and death of a photoautotrophic plant cell culture

Batch cultures of photoautotrophic cell suspensions of Chenopodium rubrum L., growing in an inorganic medium on CO2 under a daily balanced light-dark regime of 16: 8 h could be maintained for approximately 100 d without subcultivation. The long-lived cultures showed an initial cell division phase of 4 weeks, followed by a stationary phase of another 4 weeks, after which ageing and progressive cell death reduced the number of living cells and the cultures usually expired after another 3-4 weeks. These developmental phases of the cell culture were characterised with respect to photosynthetic performance, dark respiration, content of phytohormones and capacity of cell division. Cell division of the majority of the cells finished in the G1- or G0-phase of the cell cycle, caused by a pronounced decline in the endogenous levels of auxin and cytokinins. Supply of these growth factors to resting cells resulted in resumption of cytokinesis, at least by some of the cells. However, responsiveness to the phytohormones declined during the stationary phase, and subcultivation was no longer possible beyond day 60 when the phases of ageing and death commenced. Ageing was characterised by a further decline in the photosynthetic capacity of the cells, by a climacteric enhancement of dark respiration, but also by a slight increase in the level of IAA and cytokinins concomitant with a decrease in ethylene. Similarities and differences between the development of batch-cultured photoautotrophic cells of C. rubrum and that of a leaf are discussed with respect to using the cell culture as a model for a leaf.

Cell recognition by foot-and-mouth disease virus that lacks the RGD integrin-binding motif: flexibility in aphthovirus receptor usage

Cell surface molecules that can act as virus receptors may exert an important selective pressure on RNA viral quasispecies. Large population passages of foot-and-mouth disease virus (FMDV) in cell culture select for mutant viruses that render dispensable a highly conserved Arg-Gly-Asp (RGD) motif responsible for integrin receptor recognition. Here, we provide evidence that viability of recombinant FMDVs including a Asp-143-->Gly change at the RGD motif was conditioned by a number of capsid substitutions selected upon FMDV evolution in cell culture. Multiply passaged FMDVs acquired the ability to infect human K-562 cells, which do not express integrin alpha(v)beta(3). In contrast to previously described cell culture-adapted FMDVs, the RGD-independent infection did not require binding to the surface glycosaminoglycan heparan sulfate (HS). Viruses which do not bind HS and lack the RGD integrin-binding motif replicate efficiently in BHK-21 cells. Interestingly, FMDV mutants selected from the quasispecies for the inability to bind heparin regained sensitivity to inhibition by a synthetic peptide that represents the G-H loop of VP1. Thus, a single amino acid replacement leading to loss of HS recognition can shift preferential receptor usage of FMDV from HS to integrin. These results indicate at least three different mechanisms for cell recognition by FMDV and suggest a potential for this virus to use multiple, alternative receptors for entry even into the same cell type.

Inhibitors of the nonmevalonate pathway of isoprenoid biosynthesis as antimalarial drugs

A mevalonate-independent pathway of isoprenoid biosynthesis present in Plasmodium falciparum was shown to represent an effective target for chemotherapy of malaria. This pathway includes 1-deoxy-D-xylulose 5-phosphate (DOXP) as a key metabolite. The presence of two genes encoding the enzymes DOXP synthase and DOXP reductoisomerase suggests that isoprenoid biosynthesis in P. falciparum depends on the DOXP pathway. This pathway is probably located in the apicoplast. The recombinant P. falciparum DOXP reductoisomerase was inhibited by fosmidomycin and its derivative, FR-900098. Both drugs suppressed the in vitro growth of multidrug-resistant P. falciparum strains. After therapy with these drugs, mice infected with the rodent malaria parasite P. vinckei were cured.