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Biomedical subjects

A Ehrenberg

Publications and source records attributed to A Ehrenberg.

At least 19 recordsLinked to original sources
PubMed2001

Amniotic fluid microflora in asymptomatic women at mid-gestation.

The presence and composition of amniotic fluid (AF) microflora, as well as AF glucose concentration and white blood cell (WBC) count, were investigated in 22 consecutive asymptomatic women with intact membranes at mid-gestation. AF was retrieved by trans-abdominal amniocentesis. Three of the 22 women (13.6%) had microorganisms in their AF: Chlamydia trachomatis in 2 and both Corynebacterium group absolute nonfermenter (ANF) group and Propionibacterium spp. in 1. No differences were found in clinical characteristics, glucose concentration or WBC count in patients with and without microorganisms in their AF.

Adult↗
PubMed1999

Patient records in nursing homes. Effects of training on content and comprehensiveness.

The purpose of this study was to describe the effects on the contents and comprehensiveness of the nursing-care documentation in the patient records at nursing homes following an educational intervention. A review was made of records (n = 120) from nursing homes in six Swedish municipalities, allocated to a study group and a reference group. All the nursing home nurses in three municipalities received education concerning the nursing process and how to document according to the VIPS model. A retrospective audit of all nursing notes in the records from the nursing homes was made before and after the intervention. Improvements were found in the contents of the records in the study group. The number of notes on nursing history more than doubled. The occurrence of the recording of nursing diagnoses, goals and discharge notes increased. No corresponding changes were observed in the reference group. In the study group, an increase in the number of acceptable notes with contents on nursing history, status, nursing diagnosis, planned and implemented interventions, and nursing discharge notes was found. This increase was significant. The comprehensiveness in the documentation of single nursing problems was only slightly improved in the study group. No record met the requirements of the national regulations on nursing documentation or followed the nursing process thoroughly.

Aged↗
PubMed1997

EPR study of the mixed-valent diiron sites in mouse and herpes simplex virus ribonucleotide reductases. Effect of the tyrosyl radical on structure and reactivity of the diferric center.

Reduction of ribonucleotide reductase (EC 1.17.4.1) R2 proteins in a frozen glycerol-buffer solution at 77 K by mobile electrons generated by gamma-irradiation produces EPR-detectable iron sites in mixed-valent Fe(II)/Fe(III) states. The primary EPR signals give information about the ligand arrangement of the diferric form of the iron site, whereas secondary signals observed after annealing of the sample show the effects of structural relaxation. In recombinant metR2 proteins (without free radical) from mouse and herpes virus type 1, the mixed-valent sites trapped at 77 K give rise to axial S = 1/2 EPR spectra with g values in the range 1.79-1.94, observable at temperatures up to 110 K. The spectra are assigned to mu-oxo-bridged dinuclear iron sites. In mouse metR2, the primary EPR spectrum is a mixture of two components. Annealing the R2 samples to 160-170 K transforms the primary EPR signals into rhombic spectra, characterized by gav < 1.8, and observable only below 25 K. These spectra are assigned to partially relaxed forms with a mu-hydroxo bridge, formed by protonation of the oxo bridge. Further annealing at 220 K produces new rhombic EPR spectra, which are closely similar with those observed and found to be stable after chemical reduction at room temperature. The EPR signal of the primary mixed-valent iron site in active mouse R2 protein with a tyrosyl radical also has two components. Both are different from those observed in metR2. In herpes simplex virus type 1 protein R2, one primary mixed-valent component was observed for the met protein. The dose-yield curve for the mixed-valent state in active mouse R2 is sigmoidal in shape, indicating that the tyrosyl radical is reduced by mobile electrons before the iron site. Kinetic experiments on the reduction by dithionite on mouse R2 without and with radical show a significantly enhanced rate for reduction of the iron site in the protein without radical. The results suggest that in active mouse R2 only complete diferric sites with neighboring radicals give rise to the mixed-valent spectra, and that these sites may exist in two structurally distinct forms. The results on the mouse R2 proteins confirm and extend previous results obtained on the Escherichia coli protein R2 showing that the presence of the tyrosyl radical significantly affects not only the structure but also the reactivity of the iron site.

Animals↗
PubMed1997

The VIPS model--implementation and validity in different areas of nursing care.

The development of common concepts and terms for nursing practice is crucial for the effective use of nursing-information systems. In Sweden, the VIPS model has been developed to support the systematic and common documentation of nursing care in patient records. The model has been widely used in different areas of nursing practice. This literature review was conducted as a part of a larger project to study the validity and reliability of the VIPS model, as well as its dissemination into the Swedish health-care system. The findings showed in general good reliability and content validity for the keywords in the VIPS model. The implications for the further development of the model are discussed.

Humans↗
PubMed1997

Non-medical prevention of pre-eclampsia.

Daily supplementation with 1.5-2 g calcium is the only known effective method of non-medical prevention of pre-eclampsia. Data concerning the role of bed rest for prevention of this condition are still controversial. Fish oil and magnesium supplements have proved ineffective in clinical trials. Dietary salt restriction is not acceptable in view of its possible adverse effects.

Bed Rest↗
PubMed1996

Effect of the tyrosyl radical on the reduction and structure of the Escherichia coli ribonucleotide reductase protein R2 diferric site as probed by EPR on the mixed-valent state.

It was recently shown by EPR that high yields of a sterically constrained mixed-valent species may be formed in radical free protein metR2 of Escherichia coli ribonucleotide reductase by gamma-irradiation at 77 K [Davydov, R., Kuprin, S., Gräslund, A., & Ehrenberg, A. (1994) J. Am. Chem. Soc. 116, 11120]. This species, with S = 1/2, essentially retains the ligand geometry of the original diferric center and should be a sensitive probe for structural changes in the diferric centers. Here we apply this probe and demonstrate that there is a structural difference between the diferric iron center of the complete site of protein R2, with a tyrosyl radical, and that of metR2, without radical. The EPR spectrum of the mixed-valent species of metR2 shows pure axial symmetry, while complete sites show rhombic distortion and a shifted high-field turning point. Differences also remain in the EPR of the first S = 9/2 species obtained by annealing at 165 K, but disappear after relaxation at 200 K. In addition, the diferric center of a complete site is not reduced radiolytically until the associated tyrosyl radical has been reduced, indicating that an electron first reaching the iron center may be transferred to the radical. This route of electron transfer and the influence of the radical on the structure of the iron center are likely to have functional roles for the formation of the proposed substrate radical and regulation of redox processes within the enzyme. The sensitivity of the structure of the iron site to the structure of the Tyr-122 site is also demonstrated by the strong influence the mutation Y122F has on the EPR spectra of the corresponding mixed-valent species.

Electron Spin Resonance Spectroscopy↗
PubMed1996

Spectral-Density Mapping of 13Calpha-1Halpha Vector Dynamics Using Dipolar Relaxation Rates Measured at Several Magnetic Fields

The spectral-density mapping of a 13Calpha-1Halpha vector of Leu10 in the 22-residue peptide hormone motilin [P. Allard, J. Jarvet, A. Ehrenberg, and A. Graslund, J. Biomol. NMR 5, 133-146 (1995)] is extended in this paper to three polarizing fields 9.4, 11.7, and 14.1 T in order to improve the accuracy of the calculated spectral-density function J(omega) and to extend the sampling range up to 750 MHz. The problem with a usually large relative error in J(omegaH) is eliminated since the generally more precise J(omegaH - omegaC) and J(omegaH + omegaC) determined at other fields appear at nearly the same frequencies. The fitting of dynamic models to the points of spectral density was made with error weighting, and the influence of J(omegaH) was found to be negligible. Therefore, the high-frequency part of the spectral-density function is determined essentially without influence from the two transverse-type relaxation rates. In the case of a carbon-proton vector, the relaxation is mainly determined by dipolar interaction and is only weakly influenced by other relaxation mechanisms, which makes it particularly suitable for the spectral-density mapping technique. The measured relaxation rates in the time domain are transformed into the frequency domain by spectral-density mapping, and the slopes in different frequency regions are important parameters when comparing experimental data with theoretical models of motion. Using an adjustable internuclear distance reff, combined with the model-free approach, it is possible to obtain a reasonable fit to measured spectral-density points at J(0) and around J(omegaC). At the same time, however, the high-frequency slope of the spectral-density function defined by J(omegaH - omegaC) and J(omegaH + omegaC) could not be reproduced.

Journal Article↗
PubMed1996

Nursing documentation in patient records: experience of the use of the VIPS model.

The VIPS model for the documentation of nursing care in patient records was scientifically developed and published in 1991, with the aim of supporting the systematic documentation of nursing care and promoting individualized care. As the model seemed to be accepted and used in many parts of Sweden, a study was conducted in order to gather further information on the validity of the model, to describe the clinical and educational experience of its use and to refine it. Experience of the use of the model was gathered from a review of the scientific papers and other reports on it, from questionnaires addressed to nurses (n = 514), from comments by key informants, and from interviews with faculty members at all the nursing schools in the country. The findings showed that an intense process of change and development was occurring regarding nursing documentation. However, there were limitations in the use of the entire nursing process, especially in the specification of patient problems and the formulation of nursing diagnoses and nursing interventions. The keywords (Swedish spelling) of the VIPS model had good content validity in different areas of nursing care. The findings also indicated the need for further elaboration and revision of some of the keywords. A revised version of the VIPS model based on these findings is presented.

Health Knowledge, Attitudes, Practice↗
PubMed1995

Nonideality of water-hexafluoropropanol mixtures as studied by X-ray small angle scattering.

Strong temperature dependent low angle X-ray scattering by trifluoroethanol- and hexafluoro-2-propanol-water mixtures was observed in conditions commonly used in NMR work on peptides. At least two types of molecular effects may contribute to the observed scattering: formation of clathrate hydrate-like aggregates of alcohol with water as have been proposed for the similar system tert-butanol-water (Iwasaki, K. and Fujiyama, T. (1976) J. Phys. Chem. 81, 1908-1912) and a further heterogeneity of the solution resulting from immiscibility of the two components.

1-Propanol↗
PubMed1995

NMR studies of binding of 5-FdUDP and dCDP to ribonucleoside-diphosphate reductase from Escherichia coli.

5-Fluoro-2'-deoxyuridine-5'-diphosphate (5-FdUDP) has been synthesised using an original route, previously applied to the synthesis of natural nucleoside diphosphates. The interaction between 5-FdUDP and the enzyme ribonucleoside-diphosphate reductase (EC 1.17.4.1) has been studied with 19F-NMR. The product analogue is shown to be in fast exchange with substrate binding sites on protein subunit 1 (R1) of ribonucleoside-diphosphate (NDP) reductase. The number of binding sites is reduced to half when the complete holoenzyme R1R2 is formed. The temperature dependence of the line broadening of 5-FdUDP was studied using 19F-NMR, and of dCDP and dUDP using 1H-NMR. The temperature dependences are complex and a molecular model in which R1 is in a temperature dependent equilibrium between at least two conformations is suggested in order to explain the observed behaviour. Binding of a ligand to the substrate binding sites affects the conformational equilibrium in a ligand specific way. Formation of the holoenzyme R1R2 also affects the equilibrium.

Binding Sites↗
PubMed1995

Mapping of the spectral density function of a C alpha-H alpha bond vector from NMR relaxation rates of a 13C-labelled alpha-carbon in motilin.

The peptide hormone motilin was synthesised with a 13C-enriched alpha-carbon in the leucine at position 10. In aqueous solution, six different relaxation rates were measured for the 13C alpha-H alpha fragment as a function of temperature and with and without the addition of 30% (v/v) of the cosolvent d2-1,1,1,3,3,3-hexafluoro-2-propanol (HFP). The relaxation rates were analysed employing the spectral density mapping technique introduced by Peng and Wagner [(1992) J. Magn. Reson., 98, 308-332] and using the model-free approach by Lipari and Szabo [(1982) J. Am. Chem. Soc., 104, 4546-4570]. The fit to various models of dynamics was also considered. Different procedures to evaluate the overall rotational correlation time were compared. A single exponential time correlation function was found to give a good fit to the measured spectral densities only for motilin in 30% (v/v) HFP at low temperatures, whereas at high temperatures in this solvent, and in D2O at all temperatures, none of the considered models gave an acceptable fit. A new empirical spectral density function was tested and found to accurately fit the experimental spectral density mapping points. The application of spectral density mapping based on NMR relaxation data for a specific 13C-1H vector is shown to be a highly useful method to study biomolecular dynamics. Advantages are high sensitivity, high precision and uniform sampling of the spectral density function over the frequency range.

Amino Acid Sequence↗
PubMed1994

Comparison of the solution structures of the chimeric peptides galanin(1-12)-Ala-neuropeptide Y(25-36)amide and galanin(1-12)-Pro-neuropeptide Y(25-36)amide.

In a previous study [Arvidsson, K., Land, T., Langel, U., Bartfai, T. & Ehrenberg, A. (1993) Biochemistry 32, 7787-7798], the 25-amino-acid-residue chimeric peptide M32, galanin(1-12)-Pro-neuropeptide Y(25-36)amide, was found to bind very strongly to galanin receptors and also to have considerable affinity to neuropeptide Y receptors. The solution structure of M32 in 30% (by vol.) 1,1,1,3,3,3-hexafluoro-2-propanol, was determined from structural restraints obtained by two-dimensional 1H-NMR. Another peptide, M88, with Ala instead of Pro in position 13, was shown to bind with tenfold lower affinity to galanin receptors, i.e. with nearly the same affinity as galanin itself. The binding to neuropeptide Y receptors was altered in the opposite sense. The peptide M88 has now been examined by two-dimensional 1H-NMR under the same conditions as applied for M32. Using NMR-derived restraints, we have calculated structures of M88 by means of the programs CALIBA, HABAS and DIANA, and refined them by restrained energy minimisation and restrained molecular dynamics. The use of CALIBA and HABAS meant that the restraints were less restrictively formulated, than in the previous work. Hence, structures of M32 were recalculated in the same way as for M88, also including some additional restraints, possible to identify by comparison of the NMR spectra of the two peptides. The new structures of M32 confirm an alpha-helix starting at Pro13, but now continuing until Gln23, instead of ending at Ile20. Conversely, no secondary structure is now expressed in the N-terminal section. It is concluded that in the case of peptides the details of the calculated structures depend on how the restraints are calibrated. In M88, an alpha-helix is found over a long section, approximately Ser6-Gln23. Possible correlations between the binding affinities to receptors and the solution structures of the peptides M32 and M88 are discussed. This is done with particular reference to the length and stability of the alpha-helix and the flexibility of the N-terminal section and its bending direction versus the helix.

Amino Acid Sequence↗
PubMed1994

Conformation of dCDP bound to protein R1 of Escherichia coli ribonucleotide reductase.

Deoxycytidine 5'-diphosphate (dCDP) is a product and competitive inhibitor of ribonucleoside-diphosphate reductase (EC 1.17.4.1) from Escherichia coli. Its conformation in the enzyme-bound state is of importance for understanding the reaction mechanism. Free and bound dCDP are in fast exchange and the transferred nuclear Overhauser effect in two-dimensional 1H NMR was used to obtain information about interproton distances within bound dCDP. The results are consistent with a model of dCDP with the base in anti conformation and the sugar in S-type puckering, when bound either to the complete enzyme complex or to the large protein subunit alone.

Deoxycytosine Nucleotides↗
PubMed1994

Solution structure by 1H and dynamics by natural abundance 13C NMR of a receptor recognising peptide derived from a C-terminal fragment of neuropeptide Y.

A peptide consisting of 20 amino acid residues, derived from a C-terminal fragment of neuropeptide Y (NPY) and showing high affinity to NPY receptors, was synthesised. Its sequence is PAADLARYRHYINLITRQRY-NH2, and the solution structure was calculated from NMR-derived distance and torsion angle restraints, obtained at 15 degrees C in a solvent mixture of water and 30% (v/v) 1,1,1,3,3,3-hexafluoro-2-propanol, by using DIANA and restrained energy minimisation. The structure was found to consist of a well-defined alpha-helix in the centre, with a few residues at the termini having less well defined conformations. The spin-lattice and spin-spin relaxation rates of alpha-carbons have been determined on 13C at natural abundance. From 1D experiments the global rotational correlation time was determined and from 2D experiments the dynamics of each individual residue was obtained. The results demonstrate that the C alpha-H alpha vectors in the alpha-helix essentially follow the global motion. Towards the termini, contributions from local dynamics increase. This tendency is correlated to the increasing uncertainty of the structure towards the peptide ends. An effective molecular volume was calculated from the temperature dependence of the global rotational correlation time. This is well compatible with a monomeric peptide, solvated by water and 1,1,1,3,3,3-hexafluoro-2-propanol. The presence of peptide dimers was ruled out as being inconsistent with the relaxation data.

Amino Acid Sequence↗
PubMed1993

19F NMR study of the interaction of fluoride ion with ribonucleotide reductase and methane monooxygenase.

The relaxation rates of fluoride, determined by 19F NMR spectroscopy, were greatly increased in the presence of protein Mn-A, the manganese form of the hydroxylase component of methane monooxygenase. This demonstrates that F- interacts with the manganese center of protein Mn-A. On the contrary, protein Mn-R2, the manganese form of the small subunit of ribonucleotide reductase, had no effect on the relaxation rate of F-. This reflects differences between the two proteins in terms of the accessibility of the metal ion sites, despite the strong similarities of these sites.

Binding Sites↗
PubMed1993

Solution structure by 2D 1H-NMR of a chimeric peptide recognized by galanin and neuropeptide Y receptors.

The 25 amino acid residue chimeric peptide M32, galanin(1-13)-neuropeptide Y(25-36)-amide, was synthesized. The peptide was found to be recognized by both galanin and NPY receptors. The solution structure in 30% (v/v) 1,1,1,3,3,3-hexafluoro-2-propanol was examined by 2-D 1H-NMR and by CD. Proton resonance assignments were made, and structures were calculated using DIANA and refined by restrained energy minimization and molecular dynamics. The obtained structures contain an alpha-helical part in the NPY portion of the peptide including residues 13-20, and in some structures it continues to the C-terminal Tyr25. The more flexible N-terminal portion of the peptide has the freedom to approach the C-terminal alpha-helix, via a reverse turn or a nascent alpha-helix, which permits the N-terminus with Trp2 to come into close contact with the C-terminus with Tyr25. Among the ten NMR structures with lowest energy, there are structures reminiscent of the horseshoe shape of aPP, a close relative of NPY with known crystal structure. It appears that the strong alpha-helical character of the NPY (25-36) amide fragment of M32 helps to stabilize structural features in the galanin-derived part of the peptide. It is noteworthy that this rigid NPY portion of M32 does not prevent the recognition of the peptide by galanin receptors; rather, the peptide has unusually high affinity: IC50 = 0.1 nM at galanin receptors. The chimeric peptide M32 is also recognized by NPY receptors with submicromolar affinity (IC50 = 0.25 microM). The availability of a solution structure for peptide M32, which is recognized by two peptide receptors that are both members of the family of G-protein-coupled receptors, may be useful in understanding peptide receptor-ligand interactions and in designing new galanin and NPY receptor ligands.

Amino Acid Sequence↗
PubMed1993

[Prevention of myopathies and cardiomyopathies in swine using magnesium aspartate hydrochloride].

The efficiency of magnesium-aspartate-hydrochloride (MAH) in prophylaxis of porcine stress-induced myopathy was investigated. For the examination a conveyor belt was used. MAH was administered orally or intramuscularly. Clinical investigations, blood specimen collections and ECG were carried out before and after running. Stress-induced tachypnoea and tachycardia and hyperthermia were reduced after both forms of administration of MAH. The enzyme activity of CK, LDH and alpha-HBDH increased slighter after oral and i. m. application. The increase of serum glucose concentration as well as serum lactate level were reduced after oral and i. m. substitution with MAH. In the ECG apart from the relative diastolic period all time values were significantly prolonged after MAH-substitution. The results indicate that several stress-induced changes of clinical and metabolic parameters can be reduced by administration of MAH.

Animals↗