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Biomedical subjects

G Krause

Publications and source records attributed to G Krause.

At least 55 records · Page 3Linked to original sources
PubMed2001

Outbreak of Salmonella serotype Anatum infection associated with unpasteurized orange juice.

In March 1999, a patient was infected with Salmonella serotype Anatum after having consumed unpasteurized orange juice from a manufacturer in Florida. We conducted a cohort study among customers of the manufacturer, performed pulsed-field gel electrophoresis (PFGE) on isolates, and inspected the manufacturing plant. Surveillance data identified three additional patients infected with Salmonella Anatum showing indistinguishable or closely related PFGE patterns. Three of the four patients had consumed orange juice from the same manufacturer. In the cohort study, 6 of 68 persons (9%) who consumed orange juice and/or orange ice cream from the manufacturer were ill, compared with 1 of 47 (2%) who did not. A positive antigen test for Salmonella species and coliform growth in juice samples taken from the production line suggested contamination during the manufacturing process. Commercially produced orange juice should be pasteurized or otherwise processed to achieve equivalent reduction of pathogens.

Child, Preschool↗
PubMed2000

Functional rescue of the nephrogenic diabetes insipidus-causing vasopressin V2 receptor mutants G185C and R202C by a second site suppressor mutation.

Mutations in the gene of the G protein-coupled vasopressin V2 receptor (V2 receptor) cause X-linked nephrogenic diabetes insipidus (NDI). Most of the missense mutations on the extracellular face of the receptor introduce additional cysteine residues. Several groups have proposed that these residues might disrupt the conserved disulfide bond of the V2 receptor. To test this hypothesis, we first calculated a structure model of the extracellular receptor domains. The model suggests that the additional cysteine residues may form a second disulfide bond with the free, nonconserved extracellular cysteine residue Cys-195 rather than impairing the conserved bond. To address this question experimentally, we used the NDI-causing mutant receptors G185C and R202C. Their Cys-195 residues were replaced by alanine to eliminate the hypothetical second disulfide bonds. This second site mutation led to functional rescue of both NDI-causing mutant receptors, strongly suggesting that the second disulfide bonds are indeed formed. Furthermore we show that residue Cys-195, which is sensitive to "additional cysteine" mutations, is not conserved among the V2 receptors of other species and that the presence of an uneven number of extracellular cysteine residues, as in the human V2 receptor, is rare among class I G protein-coupled receptors.

Amino Acid Sequence↗
PubMed2000

Requirement of specific intrahelical interactions for stabilizing the inactive conformation of glycoprotein hormone receptors.

Systematic analysis of structural changes induced by activating mutations has been frequently utilized to study activation mechanisms of G-protein-coupled receptors (GPCRs). In the thyrotropin receptor and the lutropin receptor (LHR), a large number of naturally occurring mutations leading to constitutive receptor activation were identified. Saturating mutagenesis studies of a highly conserved Asp in the junction of the third intracellular loop and transmembrane domain 6 suggested a participation of this anionic residue in a salt bridge stabilizing the inactive receptor conformation. However, substitution of all conserved cationic residues at the cytoplasmic receptor surface did not support this hypothesis. Asp/Glu residues are a common motif at the N-terminal ends of alpha-helices terminating and stabilizing the helical structure (helix capping). Since Asp/Glu residues in the third intracellular loop/transmembrane domain 6 junction are not only preserved in glycoprotein hormone receptors but also in other GPCRs we speculated that this residue probably participates in an N-terminal helix-capping structure. Poly-Ala stretches are known to form and stabilize alpha-helices. Herein, we show that the function of the highly conserved Asp can be mimicked by poly-Ala substitutions in the LHR and thyrotropin receptor. CD and NMR studies of peptides derived from the juxtamembrane portion of the LHR confirmed the helix extension by the poly-Ala substitution and provided further evidence for an involvement of Asp in a helix-capping structure. Our data implicate that in addition to well established interhelical interactions the inactive conformation of GPCRs is also stabilized by specific intrahelical structures.

Amino Acid Sequence↗
PubMed2000

Peptide leucine arginine, a potent immunomodulatory peptide isolated and structurally characterized from the skin of the Northern Leopard frog, Rana pipiens.

On the basis of histamine release from rat peritoneal mast cells, an octadecapeptide was isolated from the skin extract of the Northern Leopard frog (Rana pipiens). This peptide was purified to homogeneity using reversed-phase high performance liquid chromatography and found to have the following primary structure by Edman degradation and pyridylethylation: LVRGCWTKSYPPKPCFVR, in which Cys(5) and Cys(15) are disulfide bridged. The peptide was named peptide leucine-arginine (pLR), reflecting the N- and C-terminal residues. Molecular modeling predicted that pLR possessed a rigid tertiary loop structure with flexible end regions. pLR was synthesized and elicited rapid, noncytolytic histamine release that had a 2-fold greater potency when compared with one of the most active histamine-liberating peptides, namely melittin. pLR was able to permeabilize negatively charged unilamellar lipid vesicles but not neutral vesicles, a finding that was consistent with its nonhemolytic action. pLR inhibited the early development of granulocyte macrophage colonies from bone marrow stem cells but did not induce apoptosis of the end stage granulocytes, i.e. mature neutrophils. pLR therefore displays biological activity with both granulopoietic progenitor cells and mast cells and thus represents a novel bioactive peptide from frog skin.

Adjuvants, Immunologic↗
PubMed2000

Comparative analysis of CD137 and LPS effects on monocyte activation, survival, and proliferation.

CD137 (ILA/4-1BB), a member of the TNF receptor family, regulates activation, survival and proliferation of primary human monocytes. Here we compare the activities of lipopolysaccharide (LPS), a classical and potent monocyte activator to that of CD137. LPS is a more potent activator of monocytes, as evidenced by a stronger induction of the proinflammatory cytokine IL-8. However, CD137 could further increase maximal cytokine induction by LPS, which points to separate signaling pathways for LPS and CD137. Also, expression of myc was only induced by the combination of CD137 and LPS. Expression of macrophage colony-stimulating factor is induced more potently by CD137, but an additive effect is obtained by the combination of CD137 and LPS. Monocyte/macrophage survival and proliferation is only induced by CD137. LPS counteracts both activities of CD137 via activation induced cell death. While LPS has a role in activation of monocytes in innate immunity, the CD137 receptor/ligand system seems to deliver an activating signal to monocyte in acquired immunity.

Antigens, CD↗
PubMed2000

Cysteine scanning mutagenesis of helices 2 and 7 in GLUT1 identifies an exofacial cleft in both transmembrane segments.

Cysteine scanning mutagenesis in conjunction with site-directed chemical modification of sulfhydryl groups by p-chloromercuribenzenesulfonate (pCMBS) or N-ethylmaleimide (NEM) was applied to putative transmembrane segments (TM) 2 and 7 of the cysteine-less glucose transporter GLUT1. Valid for both helices, the majority of cysteine substitution mutants functioned as active glucose transporters. The residues F72, G75, G76, G79, and S80 within helix 2 and G286 and N288 within helix 7 were irreplaceable because the mutant transporters displayed transport activities that were lower than 10% of Cys-less GLUT1. The indicated cluster of glycine residues within TM 2 is located on one face of the helix and may provide space for a bulky hydrophobic counterpart interacting with another transmembrane segment or lipid side chains. Characteristic for helix 7, three glutamine residues (Q279, Q282, and Q283) played an important role in transport activity of Cys-less GLUT1 because an individual replacement with cysteine reduced their transport rates by about 80%. ParaCMBS-sensitivity scanning of both transmembrane segments detected several membrane-harbored residues to be accessible to the extracellular aqueous solvent. The pCMBS-reactive sulfhydryl groups were located exclusively in the exofacial half of the plasma membrane and, when presented in a helical model, lie along one side of the helices. Taken together, transmembrane segments 2 and 7 form clefts accessible to the extracellular aqueous solvent. The lining residues are however excluded from interaction with intracellular solutes, as justified by microinjection of pCMBS into the cytoplasm of Xenopus oocytes.

4-Chloromercuribenzenesulfonate↗
PubMed2000

Effects of the 5-HT3 antagonist cilansetron vs placebo on phasic sigmoid colonic motility in healthy man: a double-blind crossover trial.

AIMS: 5-hydroxytryptamine3 receptor antagonists act antiemetically and slow colonic transit. This study evaluated effects of the high-affinity 5-HT3 antagonist, cilansetron, on fasting, meal-and anticholinesterase-stimulated phasic contractile activity of the human sigmoid colon as well as on bowel habits and stool consistency. METHODS: Five female and seven male healthy volunteers received, during three 7 day periods separated by 7 day wash-out periods, 4 mg cilansetron, 8 mg cilansetron or placebo three times daily orally under random, double-blind, crossover conditions. On day 8 of each treatment period, motility 20-40 cm from the anal verge was recorded using five pressure sensors spaced at 5 cm intervals. After a basal 30 min, subjects swallowed a further dose of the scheduled treatment; 60 min later, blood was taken for the determination of plasma cilansetron levels. Thereafter, subjects ingested a 4200 kJ meal and 250 ml sweetened mallow tea (166 kJ); 90 min after meal onset, 1 mg neostigmine was administered intramuscularly and motility recording was continued for 60 min RESULTS: Phasic contractile activity and intraluminal base-line pressure increased postprandially and more so after neostigmine. With cilansetron, the area under the pressure curve as the primary outcome variable and the number of contractions were significantly greater than with placebo (P = 0.005), amplitude and duration of contractions and base-line pressure were not affected. The effects of the two cilansetron dosages did not differ. With cilansetron, stool tended to become firmer. No adverse effects were observed. Plasma levels were highest with 8 mg cilansetron. CONCLUSIONS: Cilansetron slightly augments meal-stimulated and markedly neostigmine-stimulated phasic motility of the sigmoid colon. When administered over 7 days, it tends to increase stool consistency and is well tolerated.

Adult↗
PubMed2000

Can quality circles improve hospital-acquired infection control?

It is a fundamental principle of continuous quality improvement (CQI) that processes should be the objects of quality improvement. The objective of this study was to improve process quality concerning the prevention of hospital-acquired infections in surgical departments and intensive care units by a continuous quality improvement (CQI) approach based mainly on quality circles. This approach was evaluated in a prospective controlled intervention study in medium-size acute care hospitals (four intervention and four control hospitals). During two intervention periods (each 10 months) four external physicians with training in hospital epidemiology and infection control introduced and supervised quality circles in the intervention hospitals. Process quality was assessed by interviewing senior staff members before the first and after the second intervention period using standardized questionnaires. The gold standard process quality was defined on the basis of the CDC/HICPAC-guidelines for the prevention of hospital-acquired infections. Most of the evaluated aspects of process quality belonged to the HICPAC-categories IA and IB respectively, the CDC category I. Fifty quality circle sessions were performed in the four intervention hospitals of which 28 were dealing directly with key subjects in infection control. In the intervention hospitals, 19.8% of evaluated aspects of process quality which concerned the prevention of hospital-acquired infections were improved compared to only 6.9% in the control hospitals (P<0.05). Sixty-six point seven percent of positive changes in process quality were initiated by the results of the quality circles. Our study demonstrates that a CQI approach based on infection control quality circles can lead to a substantial improvement of process quality regarding the prevention of hospital-acquired infections.

Cross Infection↗
PubMed2000

Comprehensive community effectiveness of health care. A study of malaria treatment in children and adults in rural Burkina Faso.

Malaria is one of the most important causes of morbidity and mortality in children in sub-Saharan Africa, yet community effectiveness of treatment is not well understood. This study presents a quantitative estimate of community effectiveness of malaria treatment in Burkina Faso, based on population surveys, observational studies of health services and user surveys. Analysis of seven steps in the process of treating malaria reveal the following: (1) 21% of people with malaria attend health centres; (2) 31% of them have a sufficient history taken; (3) 69% receive a complete clinical examination; (4) 81% receive the correct dosage of drugs prescribed; (5) 91% purchase the drugs; (6) 68% take the drugs as prescribed; (7) the drugs are estimated to be 85% effective. Taking all the steps into account, overall community effectiveness is estimated to be 3%. Statistically significant differences in age and gender are seen in some steps. Quinine is prescribed too frequently. Critical issues in educating health care workers include complete history-taking and clinical examination, rational indication for quinine and adjusted drug dosages for children. We identify utilization and diagnostic quality as offering the greatest potential for improvement in overall community effectiveness.

Adolescent↗
PubMed2000

From diagnosis to drug taking: staff compliance with guidelines and patient compliance to prescriptions in Burkina Faso.

OBJECTIVE: We studied compliance with guidelines and prescriptions for six steps of the health care process to identify the step with the greatest need for improvement. DESIGN: In a cross-sectional study we used hidden observation in health centres and counting of remaining drugs in home visits. We assessed provider compliance with guidelines for medical history, physical examination, drug choice, and explanation of drug dosing, and patient compliance for drug buying and drug taking. SETTING: The study took place in six rural health centres in Burkina Faso. MAIN OUTCOME MEASURES: We measured unconditional (UPC), conditional (CPC) and accumulated proportions of compliant procedures (APC). UPC determined the proportion of compliant procedures independent from earlier steps. CPC was defined as the proportion of compliant procedures among those which were compliant in all previous steps. APC was the proportion of procedures compliant in all steps including the step concerned. RESULTS: Twenty-three per cent UPC medical history, 27% UPC (CPC = 39%) clinical examination, 59% (83%) drug choice, 22% (40%) explanation of dosing, 71% (75%) drug buying, and 63% (67%) drug taking compliance. Two per cent of the patients had compliant procedures for all steps of the process (APC). CONCLUSION: The majority of patients did not get treatment compliant with guidelines. Diagnosis had the largest need for improvement. UPC, CPC and APC were useful to identify steps with the greatest need for improvement and to assess quantitatively aspects of quality of care.

Burkina Faso↗
PubMed2000

Molecular and conformational features of a transport-relevant domain in the C-terminal tail of the vasopressin V(2) receptor.

We have previously shown a conserved glutamate/dileucine motif ((335)ELRSLL(340)) in the intracellular C terminus of the vasopressin V(2) receptor (V(2) receptor) to be essential for receptor transport from the endoplasmic reticulum (ER) to the Golgi apparatus. The motif may represent a transport signal that is recognized by a component of ER to Golgi vesicles. Alternatively, it may be necessary for transport-competent receptor folding to pass the quality-control system of the ER. To assess these two possibilities, we constructed a receptor fragment that allows transport studies independent of full-length receptor folding. Transmembrane domains II-VII were deleted, thereby fusing the intracellular C terminus to the first cytoplasmic loop. The mutations that impaired transport of the full-length receptor were introduced, and receptor fragments were localized in transiently transfected HEK 293 cells. All mutant receptor fragments were detectable at the plasma membrane, demonstrating that the glutamate/dileucine motif does not function as a small, linear vesicular transport signal. Instead, our data strongly suggest that this motif is required for transport-competent folding of the full-length receptor. To assess the underlying conformational features, a three-dimensional homology model of the V(2) receptor was computed. Our model predicts that the glutamate/dileucine motif contributes to a U-like loop within the intracellular C terminus. Residue Leu(339) may be required for folding back the intracellular C terminus to residue Leu(62) of the first cytoplasmic loop. We characterized the naturally occurring L62P and DeltaL62-R64 mutations in the first cytoplasmic loop and show that they lead to transport-defective full-length V(2) receptors that are retained in the ER, consistent with the structure model.

Amino Acid Sequence↗
PubMed1999

Spontaneous and chemically induced point mutations in HPRT cDNA of the metabolically competent human lymphoblastoid cell line, MCL-5.

Thioguanine-resistant clones of the human lymphoblastoid cell, MCL-5, which carries two recombinant plasmids expressing xenobiotic metabolizing enzymes, were obtained spontaneously and after treatment with 0.1 microgram/ml benzo[a]pyrene (BaP), 1.0 microgram/ml 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK), and 10 micrograms/ml cigarette smoke condensate (CSC). Treatment with the chemicals reduced the cloning efficiency (CE) of MCL-5 cells from about 30% in untreated cultures to about 10% after treatment with NNK and to about 1% or to less than 1% after treatment with CSC or BaP, respectively. At the same time, the mutant frequencies were increased about sevenfold above those of untreated cultures. Among a total of 138 independent mutant clones that had resulted from 55 separate cultures, 60 point mutations were identified within the hypoxanthine guanine phosphoribosyltransferase (HPRT) reading frame by sequencing full-size reverse transcription polymerase chain reaction (RT-PCR) products from thioguanine-resistant clones. The identified 53 coding errors were distributed among 33 locations and types. Among the 30 types of single basepair substitutions leading to coding errors, 12 had not been described before. In the present set of point mutations, the distribution of base substitution types as well as of mutated sites appeared to be influenced by the treatment with the chemicals. Thus, the ratio of G to T transversions increased from 3 among 19 spontaneous point mutations in the HPRT coding region to 9 among 21 BaP-induced point mutations. The G119T and G208T transversions were found three times each, exclusively after treatment with BaP, while the accumulation of two to eight incidences of the G97T, CG142/3TA, C508T, T583A and G599A mutations was split among different treatments. All eight identified point mutations identified after NNK treatment were at G or T residues on either strand that were followed by additional G or T residues.

Benzo(a)pyrene↗
PubMed1999

Structural requirements for V2 vasopressin receptor proteolytic cleavage.

The ligand-induced proteolytic cleavage of the V2 vasopressin receptor transiently expressed in COS cells was investigated. After incubation of the cell membranes with a photoreactive ligand possessing full agonistic properties for V2 receptors, approximately 90% of the porcine and bovine V2 vasopressin receptors were cleaved in the upper part of transmembrane helix 2 at a heptapeptide sequence conserved in both vasopressin and oxytocin receptors. The oxytocin receptor was completely resistant to proteolysis after binding the same photoreactive ligand, which is only a partial agonist for this receptor. Chimeric V2/oxytocin receptors obtained by transfer of extracellular domains of the oxytocin receptor into the V2 receptor showed an increase in binding affinity for oxytocin versus vasopressin and a diminished cleavage. The proteolysis-resistant chimeric V2/oxytocin receptor, which contains the first three extracellular domains of the oxytocin receptor, stimulated cAMP accumulation to a larger extent in response to vasopressin than the wild-type receptor and showed impaired desensitization of the adenylate cyclase system. Our data indicate that the proteolytic cleavage of the V2 receptor requires a defined conformation, especially of the first two extracellular domains that is induced by agonist binding. Furthermore, the results suggest that the proteolytic V2 receptor cleavage might play a role in signal termination at elevated hormone concentrations.

Adenylyl Cyclases↗
PubMed1999

Effect of body weight on phosphorus digestibility and efficacy of a microbial phytase in young pigs.

The effect of body weight on P digestibility and on efficacy of supplemental Aspergillus niger phytase was studied in two experiments with young growing pigs. Excreta were collected quantitatively. All diets contained 2.0 g digestible P per kg dry matter at a maximum and renal P excretion never exceeded 15 mg/d. When dietary P mainly originated from monocalcium-phosphate, both P digestibility and Ca net absorption linearly increased by 3.6 and 5.6 percentage units, respectively, when BW increased from 15 to 35 kg. With a similar range in BW, P digestibility and Ca net absorption were unaffected by BW when P mainly originated from maize, barley and soybean meal. In both types of diet, crude protein digestibility increased with increasing body weight, whereas organic matter digestibility was effected by BW only in the diet containing maize, barley and soybean meal. Phytase (400 U/kg) almost doubled P digestibility when supplemented to a diet with P mainly originating from maize, soybean meal and barley. This effect of phytase supplementation was equal in pigs at 15.7 kg BW (33 vs. 55%) and at 39.1 kg BW (32 vs. 56%). Digestibility of any organic fraction was unaffected by supplemental phytase. With regard to on-farm conditions, it appears eligible from this results to apply digestibility coefficients for P determined in growing-finishing pigs for piglets as well.

6-Phytase↗
PubMed1999

Rationality of drug prescriptions in rural health centres in Burkina Faso.

The objective of this study is to investigate the quality of drug prescriptions in nine health centres of three districts in rural Burkina Faso. 313 outpatient consultations were studied by methods of guided observation. Additionally interviews were held with the health care workers involved in the study. A total of 793 drugs prescribed by 15 health care workers during the observation period and 2815 prescribed drugs copied from the patient register were analyzed. An average of 2.3 drugs were prescribed per visit. 88.0% of the prescribed drugs were on the essential drug list. 88.4% were indicated according to the national treatment guidelines. 79.4% had a correct dosage. The study revealed serious deficiencies in drug prescribing that could not be detected by assessing selected quantitative drug-use indicators as recommended by the WHO. In two-thirds of the cases the patients received no information on how long the drug had to be taken. Errors in dosage occurred significantly more often in children under 5 years. The combined analysis of choice and dosage of drugs showed that 59.3% of all the patients received a correct prescription. Seven out of 21 pregnant women received drugs contraindicated in pregnancy. We conclude that assessment of quantitative drug-use indicators alone does not suffice in identifying specific needs for improvement in treatment quality. We recommend that prescribing for children under 5 and for pregnant women should be targeted in future interventions and that the lay-out, content and distribution of treatment guidelines must be improved.

Attitude of Health Personnel↗
PubMed1999

Solution structure of the receptor tyrosine kinase EphB2 SAM domain and identification of two distinct homotypic interaction sites.

The sterile alpha motif (SAM) is a protein interaction domain of around 70 amino acids present predominantly in the N- and C-termini of more than 60 diverse proteins that participate in signal transduction and transcriptional repression. SAM domains have been shown to homo- and hetero-oligomerize and to mediate specific protein-protein interactions. A highly conserved subclass of SAM domains is present at the intracellular C-terminus of more than 40 Eph receptor tyrosine kinases that are involved in the control of axonal pathfinding upon ephrin-induced oligomerization and activation in the event of cell-cell contacts. These SAM domains appear to participate in downstream signaling events via interactions with cytosolic proteins. We determined the solution structure of the EphB2 receptor SAM domain and studied its association behavior. The structure consists of five helices forming a compact structure without binding pockets or exposed conserved aromatic residues. Concentration-dependent chemical shift changes of NMR signals reveal two distinct well-separated areas on the domains' surface sensitive to the formation of homotypic oligomers in solution. These findings are supported by analytical ultracentrifugation studies. The conserved Tyr932, which was reported to be essential for the interaction with SH2 domains after phosphorylation, is buried in the hydrophobic core of the structure. The weak capability of the isolated EphB2 receptor SAM domain to form oligomers is supposed to be relevant in vivo when the driving force of ligand binding induces receptor oligomerization. A formation of SAM tetramers is thought to provide an appropriate contact area for the binding of a low-molecular-weight phosphotyrosine phosphatase and to initiate further downstream responses.

Amino Acid Motifs↗