Biomedical subjects

M Kiess

Publications and source records attributed to M Kiess.

At least 19 recordsLinked to original sources

PubMed2006

Treating the right patient at the right time: access to cardiovascular nuclear imaging.

Cardiovascular nuclear medicine uses agents labelled with radioisotopes that can be imaged with cameras (single-photon emission tomography [SPECT] or positron emission tomography [PET]) capable of detecting gamma photons to show physiological parameters such as myocardial perfusion, myocardial viability or ventricular function. There is a growing body of literature providing guidelines for the appropriate use of these techniques, but there are little data regarding the appropriate timeframe during which the procedures should be accessed. An expert working group composed of cardiologists and nuclear medicine specialists conducted an Internet search to identify current wait times and recommendations for wait times for a number of cardiac diagnostic tools and procedures, including cardiac catheterization and angioplasty, bypass grafting and vascular surgery. These data were used to estimate appropriate wait times for cardiovascular nuclear medicine procedures. The estimated times were compared with current wait times in each province. Wait time benchmarks were developed for the following: myocardial perfusion with either exercise or pharmacological stress and SPECT or PET imaging; myocardial viability assessment with either fluorodeoxyglucose SPECT or PET imaging, or thallium-201 SPECT imaging; and radionuclide angiography. Emergent, urgent and nonurgent indications were defined for each clinical examination. In each case, appropriate wait time benchmarks were defined as within 24 h for emergent indications, within three days for urgent indications and within 14 days for nonurgent indications. Substantial variability was noted from province to province with respect to access for these procedures. For myocardial perfusion imaging, mean emergent/urgent wait times varied from four to 24 days, and mean nonurgent wait times varied from 15 to 158 days. Only Ontario provided limited access to viability assessment, with fluorodeoxyglucose available in one centre. Mean emergent/urgent wait times for access to viability assessment with thallium-201 SPECT imaging varied from three to eight days, with the exception of Newfoundland, where an emergent/urgent assessment was not available; mean nonurgent wait times varied from seven to 85 days. Finally, for radionuclide angiography, mean emergent/urgent wait times varied from two to 20 days, and nonurgent wait times varied from eight to 36 days. Again, Newfoundland centres were unable to provide emergent/urgent access. The publication of these data and proposed wait times as national targets is a step toward the validation of these recommendations through consultation with clinicians caring for cardiac patients across Canada.

Canada↗

PubMed2002

A mycorrhiza-responsive protein in wheat roots.

A small protein, designated Myk15, was found to be strongly induced in wheat ( Triticum aestivum) roots colonized by the arbuscular mycorrhizal fungus Glomus intraradices. This protein, which is most abundant in root fractions characterized by strong mycorrhizal colonization, has been characterized using two-dimensional polyacrylamide gel electrophoresis and microsequencing. It has an apparent molecular mass of 15 kDa and an isoelectric point of 4.5. The N-terminal sequence has high similarity to a peptide sequence deduced from an expressed sequence tag (EST) clone derived from Medicago truncatula roots colonized by G. intraradices. This EST clone is predicted to code for a protein with a similar size and isoelectric point as Myk15. The N-terminus of the deduced M. truncatula protein contains a highly hydrophobic stretch of 24 amino acid residues preceding the region with high similarity to the Myk15 N-terminus. This hydrophobic stretch is predicted to form a transmembrane alpha-helix and may correspond to a cleavable targeting domain.

Base Sequence↗

PubMed2001

Phase I-II study of escalating doses of amifostine combined with high-dose cyclophosphamide.

PURPOSE: To evaluate the feasibility and clinical effects of increasing doses of amifostine administered four times in 1 day with high-dose (HD) cyclophosphamide (CTX). METHODS: A group of 16 patients with a diagnosis of lymphoma were treated with HD-CTX given at a total dose of 7 g/m2 subdivided into four doses, each preceded by increasing doses of amifostine. A group of 12 lymphoma patients previously treated with the same HD-CTX regimen was used as historical controls. RESULTS: The dose of amifostine was escalated in cohorts of three patients each from 4x570 mg/m2 to 4x910 mg/m2 without severe toxic effects. Further patients were treated at the highest dose level. Side effects included a fall in blood pressure (always less than 20% of baseline value), asymptomatic hypocalcemia (from a median value of 2.4 to 1.7 mmol/l) and a decrease in creatinine clearance (from a median value of 102 to 85 ml/min). The parameters of hematotoxicity for patients treated in the study were not significantly different from those of the historical control patients. CONCLUSIONS: Amifostine can be given safely at a dose of 910 mg/m2 four times in 1 day in combination with HD-CTX. With this schedule amifostine did not show a myeloprotective effect.

Adolescent↗

PubMed2001

Subcellular distribution of 14-3-3 proteins in the unicellular green alga Chlamydomonas reinhardtii.

A polyclonal antibody was raised against a recombinant Chlamydomonas 14-3-3-beta-galactosidase (beta-Gal) fusion protein and characterized for its epitope specificity towards the corresponding Chlamydomonas 14-3-3 protein by scan-peptide analysis. This antibody recognized four Chlamydomonas polypeptides with apparent molecular masses 32, 30, 27, and 24 kDa, which also reacted with the antiserum depleted of anti-(Escherichia coli beta-Gal) IgG, but not with the corresponding preimmune serum or the antiserum preincubated with purified 14-3-3 proteins. Western-blot analyses performed with the antibody depleted of anti-(beta-Gal) IgG revealed that more or less pronounced levels of 14-3-3 proteins were present in all subcellular fractions of Chlamydomonas reinhardtii except the nuclei. The highest levels of 14-3-3 protein were observed in the cytosol and microsomal fraction. The 30-kDa isoform was predominant in the cytosol, whereas the 27-kDa isoform was prevalent in the microsomes. When microsomal membranes were separated by sucrose-density-gradient centrifugation, Western-blot analysis revealed distinct patterns of 14-3-3 isoforms in the endoplasmic reticulum, dictyosome, and plasma membrane fractions identified by marker enzyme activities. These findings indicate that the four 14-3-3 proteins of C. reinhardtii differentially interact with endoplasmic reticulum, dictyosomes, and plasma membrane.

14-3-3 Proteins↗

PubMed1999

Method for determining protein kinase substrate specificities by the phosphorylation of peptide libraries on beads, phosphate-specific staining, automated sorting, and sequencing.

A method is described for the elucidation of the peptide substrate phosphorylation specificity of a protein kinase. Peptide libraries with two to six degenerate positions and a length of seven or nine amino acids were generated directly on Sepharose beads by solid-phase peptide synthesis according to the split-and-mix procedure. The immobilized peptides were incubated with the catalytic subunit of the cyclic AMP-dependent protein kinase (PKA) as a model enzyme resulting in the phosphorylation of the beads that contain the recognition motif of the kinase. The beads were then stained with a new phosphate-monoester-specific fluorescent dye consisting of a complex of iron(III) with fluorescein-coupled iminodiacetic acid. A flow cytometer was used to analyze the phosphorylation efficiency and the beads with the highest phosphorylation degree were isolated by the use of a fluorescence-activated cell sorter. Pool sequencing of those beads revealed the preferred kinase motif. The results are in good agreement with data from the literature. The method lends itself to the rapid elucidation of the specificity of uncharacterized protein kinases.

Amino Acid Sequence↗

PubMed1999

X-ray structure determination of a vanadium-dependent haloperoxidase from Ascophyllum nodosum at 2.0 A resolution.

The homo-dimeric structure of a vanadium-dependent haloperoxidase (V-BPO) from the brown alga Ascophyllum nodosum (EC 1.1.11.X) has been solved by single isomorphous replacement anomalous scattering (SIRAS) X-ray crystallography at 2.0 A resolution (PDB accession code 1QI9), using two heavy-atom datasets of a tungstate derivative measured at two different wavelengths. The protein sequence (SwissProt entry code P81701) of V-BPO was established by combining results from protein and DNA sequencing, and electron density interpretation. The enzyme has nearly an all-helical structure, with two four-helix bundles and only three small beta-sheets. The holoenzyme contains trigonal-bipyramidal coordinated vanadium atoms at its two active centres. Structural similarity to the only other structurally characterized vanadium-dependent chloroperoxidase (V-CPO) from Curvularia inaequalis exists in the vicinity of the active site and to a lesser extent in the central four-helix bundle. Despite the low sequence and structural similarity between V-BPO and V-CPO, the vanadium binding centres are highly conserved on the N-terminal side of an alpha-helix and include the proposed catalytic histidine residue (His418(V-BPO)/His404(V-CPO)). The V-BPO structure contains, in addition, a second histidine near the active site (His411(V-BPO)), which can alter the redox potential of the catalytically active VO2-O2 species by protonation/deprotonation reactions. Specific binding sites for the organic substrates, like indoles and monochlordimedone, or for halide ions are not visible in the V-BPO structure. A reaction mechanism for the enzymatic oxidation of halides is discussed, based on the present structural, spectroscopic and biochemical knowledge of vanadium-dependent haloperoxidases, explaining the observed enzymatic differences between both enzymes.

Amino Acid Sequence↗

PubMed1999

Dual function of the selenoprotein PHGPx during sperm maturation.

The selenoprotein phospholipid hydroperoxide glutathione peroxidase (PHGPx) changes its physical characteristics and biological functions during sperm maturation. PHGPx exists as a soluble peroxidase in spermatids but persists in mature spermatozoa as an enzymatically inactive, oxidatively cross-linked, insoluble protein. In the midpiece of mature spermatozoa, PHGPx protein represents at least 50 percent of the capsule material that embeds the helix of mitochondria. The role of PHGPx as a structural protein may explain the mechanical instability of the mitochondrial midpiece that is observed in selenium deficiency.

Animals↗

PubMed1999

ATP-sensitive association of mortalin with the IL-1 receptor type I.

Interleukin-1 (IL-1) is a major proinflammatory cytokine mediating local and systemic responses of the immune system. Two types of IL-1 receptors are known, but only the IL-1 receptor type I initiates biological responses. Here we show that two proteins with nucleic acid binding potential and mortalin, a member of the HSP70-family, are associated with the IL-1 receptor type I irrespective of IL-1 binding. The association of mortalin with the IL-1 receptor type I is specifically reversed by ATP concentrations in the physiological range. Other nucleotides are not or much less effective. The in vitro dissociation of mortalin effects neither the receptor association nor the activity of IRAK, which initiates the IL-1-dependent phosphorylation cascade. The roles of the receptor-associated proteins are therefore discussed in the context of receptor internalisation.

Adenosine Triphosphate↗

PubMed1999

Xylose utilisation: cloning and characterisation of the Xylose reductase from Candida tenuis.

Xylose reductases catalyse the initial reaction in the xylose utilisation pathway, the NAD(P)H+H+ dependent reduction of xylose to xylitol. In this work, the xylose reductase gene from Candida tenuis CBS 4435 was cloned and successfully expressed in E. coli. From the purified and partially sequenced protein primers were deduced for PCR. The fragment obtained was used for Southern blot analysis and screening of a subgenomic library. The clone containing the open reading frame was sequenced; the gene consisted of 969 nucleotides coding for a 322 amino acids protein with a molecular mass of 36 kDa. Putative regulatory signals were identified with the help of a Saccharomyces cerevisiae regulatory sequence database. In order to express the xylose reductase in E. coli, the gene was placed under positive and negative control. At low temperatures, the xylose reductase was expressed in soluble and active form up to about 10% of the soluble protein; with rising temperatures formation of visible inclusion bodies occurred. In refolding experiments we were able to recover the major portion of xylose reductase activity from the pellet fraction.

Aldehyde Reductase↗

PubMed1999

Xylose utilisation: cloning and characterisation of the xylitol dehydrogenase from Galactocandida mastotermitis.

We cloned and successfully expressed the gene for xylitol dehydrogenase from Galactocandida mastotermitis in Escherichia coli. The amino acid sequence revealed that the enzyme belongs to the superfamily of zinc containing, medium-chain alcohol dehydrogenases. The enzyme catalyses the second step in the xylose utilising pathway converting xylose to xylulosephosphate. Xylulose-phosphate is further degraded by the transaldolase and transketolase reactions of the pentose phosphate pathway. The purified xylitol dehydrogenase from G. mastotermitis was subjected to partial amino acid sequence analysis. The resulting amino acid information was then used to construct oligonucleotide probes for PCR amplification. The PCR product was used to screen a genomic library. The identified xdh gene includes one short intron at its 5' end. Putative regulatory signals were identified with the help of Saccharomyces cerevisiae regulatory sequence databases. An intronless xdh transcript, cloned by RT-PCR, was actively expressed in pBTac1 at 37 degrees C to approximately 8% of the soluble E. coli protein. Furthermore, the kinetic parameters were determined and conditions were found to stabilise the soluble and active protein.

Amino Acid Sequence↗

PubMed1999

Right ventricular ischemia mimicking acute anterior myocardial infarction.

Isolated right ventricular ischemia in combination with myocardial infarction (MI) is uncommon, accounting for fewer than 3% of all MI cases. A young man who presented with acute right ventricular ischemia from occlusion of a codominant right coronary artery proximal to an acute marginal branch is presented. His presenting electrocardiogram (ECG) showed ST segment elevation in V1 to V4 mimicking acute anterior MI. ECG criteria for isolated right ventricular ischemia are discussed.

Acute Disease↗

PubMed1998

Regulation of expression and activity of distinct pRB, E2F, D-type cyclin, and CKI family members during terminal differentiation of P19 cells.

The cell cycle regulatory proteins, which include cyclin-dependent kinases (cdks), cdk inhibitors (CKIs), cyclins, and the pRB, and E2F families of proteins, constitute a network of interacting factors which govern exit from or passage through the mammalian cell cycle. While the proteins within these families have similar structural characteristics, each family member exhibits distinct expression patterns during embryogenesis and distinct biological activities. In order to begin to understand the tissue-specific roles of these interacting factors, we determined the expression pattern and activity of the pRB, E2F, cyclin, cdk, and CKI families of cell cycle regulatory proteins during retinoic acid-induced (neuronal pathway) and DMSO-induced (cardiac muscle pathway) differentiation of the pluripotent murine embryonal carcinoma cell line, P19. We demonstrate here that P19 terminal differentiation causes lineage-specific changes in the expression and activity of distinct members of the E2F, pRB, cyclin, and CKI families. Furthermore, dynamic changes in the activities of these cell cycle regulatory proteins occur through several overlapping mechanisms, culminating in repression of DNA-binding activity by all of the E2F family members as cells terminally differentiate.

Animals↗

PubMed1998

Solution structure of the cytoplasmic domain of the human CD4 glycoprotein by CD and 1H NMR spectroscopy: implications for biological functions.

The human T cell receptor CD4 is a type I integral membrane glycoprotein that is involved in T cell activation and also acts as the primary coreceptor for human immunodeficiency viruses (HIV). Here the structure of a synthetic 38 amino acid peptide corresponding to the complete cytoplasmic domain of CD4 (CD4CYTO) has been investigated under a variety of solution conditions using a combination of circular dichroism and homonuclear two-dimensional 1H nuclear magnetic resonance spectroscopy. In the presence of the membrane mimetic 2,2,2-trifluoroethanol (TFE), a conformational change of CD4CYTO from a random coil to an alpha-helical structure was observed. In keeping with this, CD4CYTO has the potential to associate with membranes as demonstrated by binding studies of in vitro phosphorylated CD4CYTO with microsomal membranes. Both chemical shift and nuclear Overhauser enhancement data in 50% 2,2, 2-trifluoroethanol solution provide direct experimental evidence for the predominance of a short amphiphatic alpha-helix that is approximately 4 turns in length and extends from positions Arg-402 to Lys-417. The present data provide, for the first time, compelling experimental evidence that only a fraction of CD4CYTO has a propensity for adopting secondary structure under conditions that are assumed to exist at or near to the membrane surface and that this alpha-helical structure is located in the membrane-proximal region of CD4CYTO. The N-terminal residues, that link the alpha-helix to the transmembrane anchor of CD4, and a substantial C-terminal portion (14-18 residues) of CD4CYTO are unstructured under the solution conditions investigated. Correlation of our structural data with recent studies on the biological activity of CD4CYTO indicates that the alpha-helix is of crucial importance for the interaction of CD4 with Nef and Vpu in the process of HIV-mediated CD4 down-regulation.

Amino Acid Sequence↗

PubMed1998

Substrate-dependent enantioselectivity of a novel hydantoinase from Arthrobacter aurescens DSM 3745: purification and characterization as new member of cyclic amidases.

A hydantoinase from Arthrobacter aurescens DSM 3745 has been purified to homogeneity with a yield of 77% using a three-step purification procedure. The active enzyme is a tetramer consisting of four identical subunits, each with a molecular mass of 49670 Da as determined by mass spectrometry. The N-terminal amino acid sequence of the enzyme indicates sequence identities to cyclic amidases involved in the nucleotide metabolism as the D-hydantoinase from Agrobacterium radiobacter (53%), the D-selective dihydropyrimidinase from Bacillus stearothermophilus (38%), the allantoinase from Rana catesbeiana (26%), as well as to the catalytic subunit of the urease from Helicobacter pylori (50%). However, all studies based on substrate-dependent growth, induction and catalytic behavior documented the novelty of the bacterial hydantoinase and that its physiological role is not related to any of these enzymes or known metabolic pathways. Its substrate specificity differs from hydantoinases listed in Enzyme Nomenclature and is rather more predominant for the cleavage of aryl- than for alkyl-hydantoin derivatives. It is shown that the stereoselectivity of this enzyme depends on the substrate used for bioconversion: although it is strictly L-selective for the cleavage of D,L-5-indolylmethylhydantoin, it appears to be D-selective for the hydrolysis of D,L-methylthioethylhydantoin. Due to these findings we conclude that this novel bacterial hydantoinase should be classified as a new member of the EC-group 3.5.2 of cyclic amidases.

Amidohydrolases↗

PubMed1998

Glucose oxidase from Penicillium amagasakiense. Primary structure and comparison with other glucose-methanol-choline (GMC) oxidoreductases.

The complete amino acid sequence of glucose oxidase from Penicillium amagasakiense was determined by Edman degradation and mass spectrometry of peptide fragments derived from three different specific proteolytic digests and a cyanogen bromide cleavage. The complete sequence of each monomer comprises 587 amino acid residues, contains three cysteine residues, and seven potential N-glycosylation sites, of which at least five were confirmed to be glycosylated. Glucose oxidase from P. amagasakiense shows a high degree of identity (66%) and 79% similarity to glucose oxidase from Aspergillus niger, and is a member of the glucose-methanol-choline (GMC) oxidoreductase family. The tertiary structures of glucose oxidase from A. niger and cholesterol oxidase from Brevibacterium sterolicum were superimposed to provide a template for the sequence comparison of members of the GMC family. The general topology of the GMC oxidoreductases is conserved, with the exception of the presence of an active site lid in cholesterol oxidase and the insertion of additional structural elements in the substrate-binding domain of alcohol oxidase. The overall structure can be divided into five distinct sequence regions: FAD-binding domain, extended FAD-binding domain, flavin attachment loop and intermediate region, FAD covering lid, and substrate-binding domain. The FAD-binding and the extended FAD-binding domains are composed of several separate sequence regions. The other three regions each comprise a single contiguous sequence. Four major consensus patterns have been identified, including the nucleotide-binding consensus sequence close to their N-termini. The functions of the two motifs recently selected by the Genetics Computer Group, Madison, Wisconsin, as additional signature patterns of the GMC oxidoreductases are discussed. The other consensus patterns belong to either the FAD-binding or the extended FAD-binding domain. In addition, the roles of conserved residues are discussed wherever possible.

Amino Acid Sequence↗

PubMed1998

Structure and specific activity of macrophage-stimulating lipopeptides from Mycoplasma hyorhinis.

Mycoplasmas are potent macrophage stimulators. We describe the isolation of macrophage-stimulatory lipopeptides S-[2, 3-bisacyl(C16:0/C18:0)oxypropyl]cysteinyl-GQTDNNSSQSQQPGS GTTNT and S-[2,3-bisacyl(C16:0/C18:0)oxypropyl]cysteinyl-GQTN derived from the Mycoplasma hyorhinis variable lipoproteins VlpA and VlpC, respectively. These lipopeptides were characterized by amino acid sequence and composition analysis and by mass spectrometry. The lipopeptides S-[2,3-bis(palmitoyloxy)propyl]cysteinyl-GQTNT and S-[2, 3-bis(palmitoyloxy)propyl]cysteinyl-SKKKK and the N-palmitoylated derivative of the latter were synthesized, and their macrophage-stimulatory activities were compared in a nitric oxide release assay with peritoneal macrophages from C3H/HeJ mice. The lipopeptides with the free amino terminus showed half-maximal activity at 3 pM regardless of their amino acid sequence; i.e., they were as active as the previously isolated M. fermentans-derived lipopeptide MALP-2. The macrophage-stimulatory activity of the additionally N-palmitoylated lipopeptide or of the murein lipoprotein from Escherichia coli, however, was lower by orders of magnitude. It is concluded that the lack of N-acyl groups in mycoplasmal lipoproteins explains their exceptionally high in vitro macrophage-stimulatory capacity. Certain features that lipopolysaccharide endotoxin and mycoplasmal lipopeptides have in common are discussed. Lipoproteins and lipopeptides are likely to be the main causative agents of inflammatory reactions to mycoplasmas. This may be relevant in the context of mycoplasmas as arthritogenic pathogens and their association with AIDS.

Amino Acid Sequence↗

PubMed1998

Transgenic mice as research tools in neurocarcinogenesis.

Transgenic animal models for neurocarcinogenesis have provided significant insights into the molecular mechanisms underlying carcinogenic processes, including those which affect the nervous system. In view of the very rapid pace of acquisition of knowledge, it is not possible to cover all transgenic mouse models for neural tumors. Instead, this article discusses some of the most important technical innovations for manipulation of the mammalian genome (notably the various methods for targeted genome modifications, as well as the technology for introducing large DNA fragments into the germ line of mice), and presents a selection of the transgenic mouse models which are proving most promising for furthering our understanding of the pathogenetic basis of cancer in the nervous system.

Animals↗

PubMed1997

Synthesis of mono- and bifunctional peptide-dextran conjugates for the immobilization of peptide antigens on ELISA plates: properties and application.

Dextran has been used as a carrier molecule for the synthesis of monofunctional peptide-dextran conjugates. The immunodetection of such carrier immobilized peptides on ELISA plates was compared to that of peptides adsorbed directly to immunoplates. The main features observed with peptide-dextran conjugates were as follows: only small amounts of peptide (1-2 mg) were necessary for coupling via alpha- or epsilon-amino groups to NaIO4-activated dextran (4 mg); the coupling yield was up to 68%; an amino acid analysis of the conjugate enabled the amount of carrier immobilized peptide to be calculated; an estimated 15-17 peptides were bound per dextran molecule (MW 73,500); using a carbohydrate as carrier reduces the possibility of non-specific interactions because no hydrophobic or ionic sites and no protein-like epitopes exist on the carrier apart from the peptide ligand. It can be assumed that some peptide ligands provide the forces for an interaction with the plate surface whereas other remain free for the interaction with the antibody. Thus, the detection with monoclonal anti-peptide antibodies allowed peptide-dextran conjugates to be used at coating concentrations of 1-3 nM peptide, corresponding to 0.6-2.6 ng peptide-dextran per well. In contrast, concentrations of 150-500 nM were required for coating with peptides. The applicability of monofunctional peptide-dextran conjugates was demonstrated by investigating the titer and specificity of a polyclonal anti-peptide serum developed against human gastrointestinal glutathione peroxidase. The introduction of biotin as a second ligand of the dextran conjugate permitted its capture on streptavidin coated plates. This synthesis of bifunctional peptide-biotin-dextran conjugates opens up additional possibilities for applications.

Adsorption↗