Search PubMed⌕ Search

Biomedical subjects

U Keller

Publications and source records attributed to U Keller.

At least 55 records · Page 3Linked to original sources
PubMed2002

Murine stromal cells producing hyper-interleukin-6 and Flt3 ligand support expansion of early human hematopoietic progenitor cells without need of exogenous growth factors.

Expansion of primitive hematopoietic progenitor cells (HPC) is a major challenge in stem cell biology. Stimulation by growth factors (GF) is essential for proliferation of HPC, while the role of stromal cell coculture for maintenance of progenitor/stem cell potential is unclear. We evaluated the potential of a murine stromal cell layer providing hematopoietic GF to support expansion of human CD34(+) cells. Murine MS-5 cells were transfected with the cDNA encoding huFlt3 ligand and the interleukin6/sinterleukin-6R fusion protein hyper-IL-6. Expansion of CFC and week6 CAFC was at least as efficient in transfected clones compared to control cocultures supported with exogenous GF. Cell numbers reached 17.5- to 62.3- (day 14) and 17.4- to 92.4-fold (day 21) of input cells. Expansion of CFU-GM/Mix was 4.0- to 12.8-fold (day 14) and 4.9- to 11.7-fold (day 21). Primitive week6 CAFC were expanded up to 6.5-fold (day 14) and 6.2-fold (day 21) without exogenous GF. When direct contact of HPC and stromal cells was inhibited, a loss of CFC and much more of CAFC potential was observed with unaffected overall cell proliferation. Here, we show the generation of GF producing murine stromal cells which efficiently support early hematopoiesis without exogenous GF. Direct stromal cell-HPC contact is advantageous for maintenance of differentiation potential.

Animals↗
PubMed2001

Early impairment of calcium handling and altered expression of junctin in hearts of mice overexpressing the beta1-adrenergic receptor.

Chronic stimulation of cardiac beta1-adrenergic receptors contributes to disease progression and mortality in patients and animal models of heart failure. To search for the mechanism of adrenergic impairment of cardiac function in vivo, we studied transgenic mice with cardiac-specific overexpression of beta1-adrenergic receptors. Transgenic mice with cardiac overexpression of beta1-adrenergic receptors showed progressive left ventricular fibrosis starting at 4 months of age. Left ventricular catheterization revealed a modest enhancement of contractility and relaxation at 2 months of age, followed by progressive dysfunction in both parameters and ultimately cardiac failure. When the effects of endogenous catecholamines were blocked by the b-receptor antagonist propranolol, maximal rate of contractility (dp/dtmax) and maximal rate of relaxation (dp/dtmin) were significantly blunted in 2-month-old beta1-receptor transgenic mice. Isolated cardiomyocytes from these animals displayed markedly altered calcium transients with significant prolongation of the intracellular calcium transient compared with nontransgenic littermates. We determined the expression of sarcoplasmic reticulum proteins involved in calcium handling by RNase protection assay and by immunoblotting. Although the expression of calsequestrin, triadin, and phospholamban was not altered, we observed a progressive decrease in junctin abundance in beta1-receptor transgenic mice (Pbeta1-adrenergic receptors.

Animals↗
PubMed2001

[Comorbidity and physical complaints in morbid obesity].

The prevalence of obesity is increasing world wide, resulting in morbidity, mortality, and reduced quality of life. The aim of this study was to assess comorbidities and complaints of subjects with morbid obesity in comparison to milder forms of overweight. Therefore, 299 patients visiting our obesity consultation were examined and surveyed prospectively. 41% of the subjects were morbidly obese showing a significantly higher prevalence of arterial hypertension, edema, dyspnea, eczema and depression. Additionally, sleepiness, reduced work capacity, physical inactivity, disadvantages in social life and disturbed eating habits were observed more frequent. Evaluation of subjects with morbid obesity should include a large spectrum of complications, in order to be able to offer a comprehensive support and treatment.

Adult↗
PubMed2001

Expression and rapid one-step purification of biologically active His-tagged factor C by Ni(2+) affinity column chromatography.

Factor C is an unusual extracellular protein capable of inducing cytodifferentiation in certain Streptomyces strains. The protein is produced by Streptomyces griseus 45H at such a low amount that the study of its mode of action was hindered by the shortage of purified protein. We report here the expression of C-terminally hexa-His-tagged factor C in Streptomyces lividans and Escherichia coli. Expression in S. lividans is low while in E. coli it is relatively high, yielding about 5--10 mg of biologically fully active protein per liter culture.

Amino Acid Sequence↗
PubMed2001

Biotechnology and genetics of ergot alkaloids.

Ergot alkaloids, i.e. ergoline-derived toxic metabolites, are produced by a wide range of fungi, predominantly by members of the grass-parasitizing family of the Clavicipitaceae. Naturally occurring alkaloids like the D-lysergic acid amides, produced by the "ergot fungus" Claviceps purpurea, have been used as medicinal agents for a long time. The pharmacological effects of the various ergot alkaloids and their derivatives are due to the structural similarity of the tetracyclic ring system to neurotransmitters such as noradrenaline, dopamine or serotonin. In addition to "classical" indications, e.g. migraine or blood pressure regulation, there is a wide spectrum of potential new applications of this interesting group of compounds. The biotechnology of ergot alkaloids has a long tradition, and efficient parasitic and submerse production processes have been developed; the biochemistry of the pathway and the physiology of production have been worked out in detail. The recent identification of a cluster of genes involved in ergot alkaloid biosynthesis in C. purpurea and the availability of molecular genetic techniques allow the development of strategies for rational drug design of ergoline-related drugs by enzyme engineering and by biocombinatorial approaches.

Biotechnology↗
PubMed2001

Nonribosomal biosynthesis of microbial chromopeptides.

Nonribosomal chromopeptides and mixed chromopeptide-polyketides contain aromatic or heteroaromatic side groups which are important recognition elements for interaction with cellular targets such as DNA and proteins, resulting in the biological activities of these natural products. In the chromopeptide lactones and arylpeptide-siderophores from bacteria, the chromophore moiety--an aryl carboxylate amidated to the peptide chain--constitutes the formal amino terminus and is the starter residue of peptide assembly. Common to many arylpeptide systems is the activation by stand-alone adenylation domains and loading of the starter to discrete aryl carrier proteins (ArCPs) or ArCP domains which interact with the modules of the respective nonribosomal peptide synthetase (NRPS), assembling the next residues of the chain. Chain modification is another mechanism of nonribosomal chromopeptide synthesis where heteroaromatic rings such as thiazoles and oxazoles in peptides and polyketides are generated by heterocylizations of acyl- or peptidyl-cysteinyl or -serinyl/threonyl intermediates in each elongation step. In this review the basic mechanisms of chromophore acquisition in nonribosomal chromopeptide synthesis and mixed peptide/polyketide synthesis are illustrated by comparing the biosynthesis systems of various chromopeptides and chromopeptidic polyketide compounds.

Bacteria↗
PubMed2001

gp130-stimulating designer cytokine Hyper-interleukin-6 synergizes with murine stroma for long-term survival of primitive human hematopoietic progenitor cells.

OBJECTIVE: Experimental strategies for ex vivo expansion of human hematopoietic stem/progenitor cells involve the use of exogenous cytokines as well as direct interaction with stromal elements. We examined the use of the interleukin-6/soluble interleukin-6 receptor (IL-6/sIL-6R) fusion protein Hyper-IL-6 (H-IL-6), which interacts directly with gp130, in conjunction with stromal support for expansion of human progenitors. MATERIALS AND METHODS: Peripheral blood CD34+ cells were cultured on the murine stromal cell line FBMD1 or in suspension for up to 28 days with different cytokines. Cells were evaluated at various time points for phenotype, proliferative and clonogenic capacity, and long-term hematopoietic activity. RESULTS: The combination of Flt3 ligand and H-IL-6 was markedly more effective than Flt3 ligand and IL-6/sIL-6R for expansion of CD34+ cells in suspension culture and on FBMD1. Addition of kit ligand but not thrombopoietin to Flt3 ligand and H-IL-6 significantly augmented proliferation and enhanced colony formation three-fold. However, long-term cobblestone area-forming cell assays indicated that although multipotent progenitors were maintained up to 21 days on FBMD1 in the presence of Flt3 ligand alone and were amplified three-fold by addition of H-IL-6, CD34+ cells cultured in the absence of stromal support rapidly lost their cobblestone area-forming cell potential. Immunophenotyping revealed that stromal support prevented up-regulation of IL-6R on CD34+ cells, which was induced within 3 days in stroma-free cultures and was enhanced in the presence of kit ligand. Delayed addition of H-IL-6 to the cultures resulted in reduced proliferation and colony-forming unit potential. CONCLUSION: H-IL-6 synergizes with stromal elements to effectively enhance proliferation and maintenance of primitive hematopoietic progenitors under prolonged ex vivo culture conditions.

Cell Communication↗
PubMed2001

Food and nutritional care in hospitals: how to prevent undernutrition--report and guidelines from the Council of Europe.

In 1999 the Council of Europe decided to collect information regarding Nutrition programmes in hospitals and for this purpose a network consisting of national experts from eight of the Partial Agreement member states was established. The aim was to review the current practice in Europe regarding hospital food provision, to highlight deficiencies and to issue guidelines to improve the nutritional care and support of hospitalized patients. Five major problems seemed to be common in this context: 1) lack of clearly defined responsibilities; 2) lack of sufficient education; 3) lack of influence of the patients; 4) lack of co-operation among all staff groups; and 5) lack of involvement from the hospital management. To solve the problems highlighted, a combined 'team-effort' is needed from national authorities and all staff involved in the nutritional care and support, including hospital managers.

Europe↗
PubMed2001

Regulation of hematopoietic growth factor production by genetically modified human bone marrow stromal cells expressing interleukin-1beta antisense RNA.

Interleukin-1 (IL-1) plays a major role in the regulation of bone marrow stromal cell function and hematopoiesis. It is known to induce secretion of the hematopoietic growth factors granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage CSF (GM-CSF), IL-6, and IL-8 as well as IL-1 itself in stromal cells. We investigated the role of IL-1beta-mediated growth factor production in the human stromal cell line L88/5. Using liposome-mediated DNA transfer, two stromal cell transfectants that constitutively express IL-1beta antisense (AS) RNA were generated. Expression of IL-1beta AS RNA and IL-1beta RNA was determined by RT-PCR. The stromal cell transfectants were strongly impaired in their endogenous IL-1beta production, and this effect was present even when strong IL-1beta inducers, such as IL-1alpha and tumor necrosis factor-alpha (TNF-alpha), were used. Reduced endogenous IL-1beta levels had no effect on the constitutive production of IL-6, IL-8, and GM-CSF measured by ELISA. In contrast to lipopolysaccharide (LPS) stimulation, IL-1alpha-mediated stimulation of GM-CSF production was significantly reduced in AS transfectants. TNF-alpha induced GM-CSF production was also reduced. IL-6 and IL-8 production was increased in transfectants, suggesting a negative regulatory role of IL-1beta in L88/5. This new approach using AS technology to specifically target constitutive RNA expression will allow further characterization of the bone marrow cytokine network in normal and malignant hematopoiesis.

Base Sequence↗
PubMed2000

[Nasal CPAP therapy in obstructive sleep apnea syndrome: patient compliance].

We aimed in 186 patients with obstructive sleep apnoea, consecutively treated with nasal CPAP between January 1990 and December 1997, to evaluate compliance with nCPAP therapy and to explore factors influencing compliance. At 3 to 6 months (K1), 1 to 2 years (K2) and more than 3 years (K3) patients were reexamined regarding clinical conditions, the mean time of nCPAP usage per night, nCPAP pressure, and body mass index (BMI). The regularly conducted controls consisted of checking mask fitting, polygraphy with automatic pressure titration and once, mostly at K1, polysomnography. Compliance with nCPAP was considered to be sufficient more than 4 hours of usage per night. At K1, 9 patients had stopped therapy, 5 had moved away, 6 had changed therapy, 6 had died, and 41 had not been treated long enough to have a follow-up at K1. Thus we were able to reexamine 119 patients with ongoing nCPAP therapy. We found no correlation between indices of severeness of sleep apnoea (apnoea/hypopnea index, mean low of night time oxygen saturation, nCPAP pressure, and BMI) and compliance. At K1 87 patients (73%) had sufficient nCPAP compliance. All of them showed sufficient compliance at K2 and K3 too. We conclude that a sufficient compliance at an initial control implies sufficient compliance later on. 32 patients (27%) showed insufficient compliance at K1. Of this group 41% (13 patients) improved compliance at K2. This result underlines the value of a second instruction in nCPAP therapy when patient compliance was lacking initially.

Administration, Intranasal↗
PubMed2000

[Evaluating the efficacy and tolerance of atorvastatin in hyperlipidemia in general practice (SWITCH Study)].

Elevated levels of serum lipids and lipoproteins are known to play a major role in the development of atherosclerosis and subsequent coronary heart disease (CHD). In controlled clinical studies, atorvastatin (Sortis), a new 3-hydroxy-3-methyl-glutaryl-coenzyme-A (HMG-CoA)-reductase inhibitor, proved to be a very effective and safe lipid-lowering agent. The aim of this open-label, multicentre study (without a control group) was to confirm the efficacy and safety of atorvastatin in a private practice group, including 181 Swiss cardiologists, internists, and general practitioners. A total of 877 hyperlipidaemic patients requiring treatment participated in this study. To evaluate the effectiveness of the treatment with atorvastatin over a period of 12 weeks, total plasma cholesterol (TC), HDL cholesterol, LDL cholesterol and triglycerides (TG) were determined every 4 weeks. The initial atorvastatin dose was 10 mg in 78% of patients and 20 mg in 22%. The dose was doubled every 4 weeks until the target values of TC < or = 5.2 mmol/l and TC/HDL < or = 5 were reached. After 12 weeks of treatment with atorvastatin the mean reduction in TC, TC/HDL, LDL and TG compared to baseline levels was 33, 37, 42, and 25% respectively. At the same time the HDL concentration was increased by 9%. These results were evidenced in patients with existing coronary heart disease, in high risk patients without manifest coronary heart disease and in patients with significantly elevated lipid levels (TC > 7.8 mmol/l, TC/HDL > 6.5). After treatment with atorvastatin for 12 weeks, 59% of patients had reached the therapeutic target of TC < or = 5.2 mmol/l. The target of TC/HDL < or = 5 was reached by 79%. Atorvastatin was almost without exception well tolerated, the most frequently reported side effects being nausea, myalgia, and headache. In this open-label multicentre study atorvastatin was found to be effective and well tolerated. The observed reduction in the lipid and lipoprotein concentration is in accordance with the results of published controlled studies. The lipid and lipoprotein concentrations were decreased significantly in patients with slight to moderate elevation of lipid levels as well as in those with significantly raised values.

Adult↗
PubMed2000

Effect of pretreatment of rubber material on its biodegradability by various rubber degrading bacteria.

The effect of pretreatment of several cis-1,4-polyisoprene containing rubbers on their biodegradability was examined. Tests were carried out with six recently isolated and characterized rubber degrading bacteria belonging to the genera Gordonia (strains Kb2, Kd2 and VH2), Mycobacterium, Micromonospora and Pseudomonas. All strains were able to use natural rubber (NR) as well as NR latex gloves as sole carbon source. Extraction of NR latex gloves by organic solvents resulted in an enhancement of growth for three of the selected strains. On the other hand, growth of Gordonia sp. (strain Kb2 and Kd2), Mycobacterium fortuitum NF4 and Micromonospora aurantiaca W2b on synthetic cis-1,4-polyisoprene did only occur after removal of the antioxidants, that are usually added during manufacture to prevent aging of the materials. Detailed degradation studies performed with Gordonia sp. Kb2 revealed an enhanced mineralization of pretreated NR latex gloves and mineralization of purified natural rubber (NR), indicating the actual mineralization of cis-1,4-polyisoprene rubber constituent even after removal of non-rubber constituent that may act as co-metabolic substrate and support microbial growth. Further analysis by scanning electron microscopy (SEM) clearly demonstrated the enhanced colonization efficiency of these bacteria towards pretreated NR latex gloves. Colonization was additionally visualized by staining of overgrown NR latex gloves with Schiff's reagent, and the purple color produced in the area of degradation was an evidence for the accumulation of aldehydes containing oligomers. Further enhancement of latex gloves degradation could be achieved after successive replacement of mineral salts medium during cultivation. Thereby, a rapid disintegration of untreated NR latex gloves material was accomplished by Gordonia sp. strain VH2.

Actinomycetales↗
PubMed2000

A gram-negative bacterium, identified as Pseudomonas aeruginosa AL98, is a potent degrader of natural rubber and synthetic cis-1, 4-polyisoprene.

A Gram-negative bacterium, strain AL98, was isolated from foul water inside of a deteriorated car tire on a farmer's field in Münster, Germany. The strain was able to considerably disintegrate natural rubber (NR), either in the raw state as NR latex concentrate or in the vulcanized state as NR latex glove, as well as raw synthetic cis-1,4-polyisoprene (IR). Determination of carbon dioxide evolution and living cell number during batch cultivation with each of the materials as sole source of carbon, revealed mineralization of the rubber polymer during biomass increase. Surface investigation by scanning electron microscopy gave evidence for an adhesive growth behavior of the strain proceeding by colonizing the rubber surface, merging into the rubber and forming a biofilm prior to disintegration of the material. Schiff's reagent staining performed with NR latex gloves indicated production and accumulation of aldehyde groups during colonization. The solid glove substrate disappeared completely after a prolonged cultivation period as a result of continuous degradation. Taxonomic analyses of the strain, which were also based on similarity examination of the complete 16S rRNA gene, revealed classification of strain AL98 as a strain of Pseudomonas aeruginosa. This is the first report about the isolation of a Gram-negative bacterium exhibiting strong rubber decomposing properties.

Automobiles↗
PubMed2000

Construction and in vitro analysis of a new bi-modular polypeptide synthetase for synthesis of N-methylated acyl peptides.

BACKGROUND: Many active peptides are synthesized by nonribosomal peptide synthetases (NRPSs), large multimodular enzymes. Each module incorporates one amino acid, and is composed of two domains: an activation domain that activates the substrate amino acid and a condensation domain for peptide-bond formation. Activation domains sometimes contain additional activities (e.g. N-methylation or epimerization). Novel peptides can be generated by swapping domains. Exchange of domains containing N-methylation activity has not been reported, however. RESULTS: The actinomycin NRPS was used to investigate domain swapping. The first two amino acids of actinomycin are threonine and valine. We replaced the valine activation domain of module 2 with an N-methyl valine (MeVal) activation domain. The recombinant NRPS (AcmTmVe) catalyzes the formation of threonyl-valine. In the presence of S-adenosyl-methionine, valine was converted to MeVal but subsequent dipeptide formation was blocked. When acyl-threonine (the natural intermediate) was present at module 1, formation of acyl-threonine-MeVal occurred. The epimerization domain of AcmTmVe was impaired. CONCLUSIONS: A simple activation domain can be replaced by one with N-methylation activity. The same condensation domain can catalyze peptide-bond formation between N-methyl and nonmethylated amino acids. Modification of the upstream amino acid (i.e. acylation of threonine), however, was required for condensation with MeVal. Steric hindrance reduces chemical reactivity of N-methyl amino acids - perfect substrate positioning may only be achieved with acylated threonine. Loss of the epimerase activity of AcmTmVe suggests N-methyltransferase and epimerase domains, not found together naturally, are incompatible.

Bacterial Proteins↗
PubMed2000

[Consequences and complications of obesity].

Obesity increases the risk of metabolic complications such as diabetes, dyslipidemia, systemic hypertension and cardiovascular disease. These are mainly responsible for the increased mortality of obese people. Other metabolic consequences of obesity are: gallstones, steatosis of the liver and the polycystic ovary syndrome. Beside the body mass index the distribution of body fat is important. Centralized obesity, as measured by the waist-to-hip circumference ratio (WHR), is associated with increased mortality and morbidity. Insulin resistance and hyperinsulinaemia seem to play a central role in the pathogenesis of this association. Obesity has not only metabolic complications. There is a relationship between obesity and impaired respiratory function. Furthermore is obesity a risk factor for osteoarthrosis of the knee, the hip and even the hand and for pulmonary embolism and venous thrombosis. Obesity can also lead to psycho-social problems such as depression, social discrimination and isolation.

Body Constitution↗
PubMed2000

Nutritional supplements combined with dietary counselling diminish whole body protein catabolism in HIV-infected patients.

BACKGROUND: Weight loss and protein malnutrition are frequent complications in HIV-infected patients. The effect of an oral nutritional supplement combined with nutritional counselling on whole body protein metabolism was assessed. MATERIALS AND METHODS: HIV-infected individuals with a body mass index < 21 kg m-2 or CD4-T cells < 500 micro L-1 in stable clinical condition were randomly allocated to [1] receive either oral nutritional supplements (containing 2510 kJ, complete macro- and micronutrients) and dietary counselling (n = 8), or [2] identical monitoring but no supplements or specific nutritional advice (controls, n = 7). Whole body leucine kinetics and leucine oxidation rate were determined by [1-13C]-leucine infusions and lean and fat mass were measured before and 12 weeks after intervention. RESULTS: Leucine oxidation (protein catabolism) decreased in the group receiving nutritional intervention from 0.33 +/- 0.02 to 0.26 +/- 0.02 micromol kg-1 min-1 after 12 weeks (P < 0.05; P < 0.05 vs. control group) but remained unchanged in the control group. Whole body leucine flux showed a tendency to decrease in the intervention group from 1.92 +/- 0.19 to 1.73 +/- 0.14 micromol kg-1 min-1 (P = 0.07) and remained unchanged in the control group (2.21 +/- 0.16 and 2.27 +/- 0.14 micromol kg-1 min-1, respectively). Lean body mass determined by bioelectrical impedance analysis increased in the nutritional intervention group from 84 +/- 2 to 86 +/- 2 per cent (P < 0.05) and fat mass decreased from 17 +/- 2 to 14 +/- 2 per cent (P < 0.05) of total body weight whereas neither mass changed in the control group. Nutritional intervention had no significant effect on lymphocyte CD4 counts, on plasma TNFR 55, TNFR 75 and ILR 2 concentrations and on quality of life. CONCLUSIONS: The data demonstrate an anticatabolic effect of nutritional supplements combined with dietary counselling in HIV-infected subjects. They suggest that diminished whole body protein catabolism resulted in a change of body composition (increased lean mass, decreased fat mass).

Body Composition↗
PubMed2000

Bioelectrical impedance analysis during acute changes of extracellular osmolality in man.

BACKGROUND & AIMS: Bioelectrical impedance analysis (BIA) is widely used as an inexpensive and noninvasive method to provide estimates of body compartments such as total body water, lean body mass and fat mass. The present study was performed to test the reliability of this method during acute changes of extracellular osmolality in eight young health men. METHODS: Hyperosmolal isohydration was achieved by overnight infusions of hypertonic saline solutions (2 and 5% NaCl) and thirsting, and hypoosmolal hyperhydration by drinking of free water and overnight application of desmopressin. The control study (isoosmolality) consisted of oral water ad libitum. RESULTS: When plasma osmolality and sodium concentrations increased (from 285 +/- 1 to 296 +/- 1 mmol/kg (P<0.001) and from 141.9 +/- 0.7 to 148.3 +/- 0.6 mmol/l (P<0.0001)) and total body water remained unchanged, body impedance decreased and calculated total body water increased from 42.7 +/- 2.7 to 45.6 +/- 2.3 liters (P<0.03). In contrast, during hypoosmolal hyperhydration total body water increased by 1.56 +/- 0.17 kg and plasma osmolality decreased from 285 +/- 1 to 272 +/- 1 mmol/kg (P<0.001) and plasma sodium concentrations from 142 +/- 0.5 to 134.8 +/- 0.4 mmol/l (P<0.0001). In spite of these changes of body water, impedance measurements and calculated total body water remained unchanged. During conditions of isoosmolal isohydration (as demonstrated by unchanged plasma sodium concentrations and osmolality) the measurements by BIA also remained unchanged. CONCLUSIONS: Measurements of total body water using BIA under conditions of unknown hydration status (hyper-, hypo- or isohydration) and unknown osmolality (hyper-, hypo- or isoosmolality) may not be reliable. Therefore bioelectrical impedance analysis is not a suitable bedside method to assess changes of body compartments under unstable hydration status.

Adult↗