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C Jäger

Publications and source records attributed to C Jäger.

At least 37 records · Page 2Linked to original sources
PubMed1998

Measurements of chain length distributions in calcium phosphate glasses using 2D 31P double quantum NMR.

31P double quantum (DQ) NMR is used for improved studies of the structure of phosphate glasses. The common Qn notation of the network forming tetrahedral phosphate units with n bridging oxygen atoms is extended to Qn,jkl indicating the Q type of the bonded adjacent units by the additional superscripts j,k and l. It will be shown that: (i) Q1 units have different isotropic chemical shifts depending on whether they form diphosphate anions in the amorphous state (Q1,1) or end groups of chains (Q1,2) and (ii) that even Q2 units possess different isotropic chemical shifts such that in the DQ dimension Q2,11 can be distinguished from Q2,12 and middle groups of longer chains or rings (Q2,22). Based on this result the opportunity for measuring chain length distributions in the amorphous state is discussed and first results for binary calcium phosphate glasses are presented. The advantages and also the limitations of this novel approach will be discussed.

Calcium Phosphates↗
PubMed1998

Molecular characterization of Coxiella burnetii isolates.

Restriction fragment length polymorphism (RFLP) was used for the differentiation of 80 Coxiella burnetii isolates derived from animals and humans in Europe, USA, Africa and Asia. After NotI restriction of total C. burnetii DNA and pulsed field gel electrophoresis (PFGE) 20 different restriction patterns were distinguished. The index of discrimination for this typing system was 0.86. Comparison and phylogenetic analysis of the different RFLP patterns revealed evolutionary relationships among groups that corresponded to the geographical origin of the isolates. This finding was confirmed by genetic mapping. No correlation between restriction group and virulence of isolates was detected.

Animals↗
PubMed1998

An outbreak of sheep-associated Q fever in a rural community in Germany.

In spring 1996, an outbreak of Q fever occurred among residents of a rural town (population: 300) in Germany. A retrospective cohort study was conducted to ascertain the extent of the outbreak and to assess potential risk factors for illness. In July 1996, all residents > or =15 years received a self-administered questionnaire and were offered Coxiella burnetii antibody testing. Residents were considered to have probable Q fever if they had a positive result for IgM C. burnetii antibodies by ELISA or possible Q fever if they had fever > or =39 degrees C lasting >2 days and > or =3 symptoms (chills, sweats, severe headache, cough, aching muscles/joints, back pain, fatigue, or feeling ill) after 1 January 1996. Two hundred (84%) of the 239 residents aged > or =15 years either completed the questionnaire or submitted blood for antibody testing. Forty-five (23%) of these 200 met the probable or possible case definitions. Onsets of illness occurred in January-June 1996. Cases were geographically distributed throughout the town. Persons reporting contact with sheep (32% vs 18%, RR: 1.8, 95% CI: 1.1-2.9) and walking near a large sheep farm located next the town (34% vs 8%, RR: 4.5, 95% CI: 1.7-12.2) were more likely to have met the case definition than those without these exposures. Fifteen of 20 samples from the large sheep flock were positive for C. burnetii antibodies. The sheep had lambed outdoors in December 1995-January 1996 while the weather was extremely dry. The timing of the outbreak after lambing, the uniform distribution of cases throughout the town and the absence of risk factors among most case-persons suggest airborne transmission of C. burnetii from the large sheep farm.

Adolescent↗
PubMed1998

Ultraviolet B radiation-induced production of interleukin 1alpha and interleukin 6 in a human squamous carcinoma cell line is wavelength-dependent and can be inhibited by pharmacological agents.

Ultraviolet (UV) B irradiation induces keratinocytes to produce among others the proinflammatory cytokines interleukin (IL) 1 and IL-6. The wavelength dependence of this UVB effect has not yet been assessed. We evaluated the potential of different UVB wavelength regions to release cytokines from the squamous carcinoma cell line SCL II and also assessed the effect of various putative inhibitors. Confluent monolayers of the cells were irradiated with 0.5-2.0 mJ/cm2 UVB at 280, 290, 300, 310 or 320 (each +/- 5) nm. In additional experiments dexamethasone (10-9-10-5 mol/L), ascorbic acid, d-alpha-tocopherol or indomethacin (each 10-7-10-4 mol/L) were added to the culture medium 24 h before, immediately after or combined before and after irradiation with 1 mJ/cm2 UVB at 280 +/- 5 nm. Supernatants of the cell cultures were recovered at 24 h after irradiation, and IL-1alpha or IL-6 were determined by an enzyme-linked immunosorbent assay (ELISA). IL-1alpha and IL-6 production were induced by UVB at 280, 290 and 300 nm, the production depended on the UV dose and decreased with increasing wavelengths. Irradiation at 310 or 320 nm did not induce cytokine production up to the maximum dose used. The production of IL-1 alpha/IL-6 was inhibited up to 80/89% (10-7-10-6 mol/L before and after irradiation) by dexamethasone in a concentration-dependent manner and with all conditions of incubation. Release of cytokines was also suppressed by indomethacin, d-alpha-tocopherol or ascorbic acid, but concentration dependence was not always evident. These results show that particularly shorter UVB radiation, which is expected to increase due to stratospheric ozone depletion, induces prominent production of proinflammatory cytokines, indicating major biological effects. Different pharmacological compounds can interfere with this effect and seem worth further evaluation with regard to their clinical effects.

Aged↗
PubMed1998

PCR detection of Coxiella burnetii from different clinical specimens, especially bovine milk, on the basis of DNA preparation with a silica matrix.

For PCR detection of Coxiella burnetii in various clinical specimens we developed a sample preparation method in which silica binding of DNA was used. This method was found to be fast, easily performed with large numbers of samples, and equally sensitive for all of the specimens tested (livers, spleens, placentas, heart valves, milk, blood). The DNA preparation method described here can also be used as an initial step in any PCR-based examination of specimens. The procedure was tested with more than 600 milk samples, which were taken from 21 cows that were seropositive for C. burnetii and reportedly had fertility problems (and therefore were suspected of shedding the agent through milk intermittently or continuously). Of the 21 cows tested, 6 were shedding C. burnetii through milk. Altogether, C. burnetii DNA was detected in 6% of the samples. There was no correlation between the shedding pattern and the serological results.

Animals↗
PubMed1998

Physical and genetic map of the obligate intracellular bacterium Coxiella burnetii.

Pulsed-field gel electrophoresis and PCR techniques have been used to construct a NotI macrorestriction map of the obligate intracellular bacterium Coxiella burnetii Nine Mile. The size of the chromosome has been determined to be 2,103 kb comprising 29 NotI restriction fragments. The average resolution is 72.5 kb, or about 3. 5% of the genome. Experimental data support the presence of a linear chromosome. Published genes were localized on the physical map by Southern hybridization. One gene, recognized as transposable element, was found to be present in at least nine sites evenly distributed over the whole chromosome. There is only one copy of a 16S rRNA gene. The putative oriC has been located on a 27.5-kb NotI fragment. Gene organization upstream the oriC is almost identical to that of Pseudomonas putida and Bacillus subtilis, whereas gene organization downstream the oriC seems to be unique among bacteria. The physical map will be helpful in investigations of the great heterogeneity in restriction fragment length polymorphism patterns of different isolates and the great variation in genome size. The genetic map will help to determine whether gene order in different isolates is conserved.

Bacillus subtilis↗
PubMed1997

Plasmid-homologous sequences in the chromosome of plasmidless Coxiella burnetii Scurry Q217.

Chromosomal DNA from Coxiella burnetii Scurry Q217 was screened for the presence of plasmid-homologous sequences. Total DNA from Scurry Q217 was digested with NotI, and the resulting DNA fragments were separated by contour-clamped homogeneous electric field pulsed-field gel electrophoresis (CHEF-PFGE). Following hybridization with biotin-labeled QpH1 plasmid as a probe, two DNA fragments of 40 and 170 kb were identified as targets. These fragments were cloned, and subclones containing QpH1-homologous sequences were completely sequenced. The physical mapping of DNA fragments was achieved by PCR with primers derived from adjacent fragments, and a total of 18,360 bp was sequenced. Within the QpH1-homologous region spanning 16,624 bp, homology was as high as 99%. Deletions were identified within EcoRI fragments A(H)-C(H)-K(H)-B(H) (13,490 bp) and J(H)-G(H)-E(H)-L+-D(H) (6,509 bp) and in fragment A(H) alone (619 bp). An insertion of 744 bp was identified within the JDc region of Scurry Q217. A search for putative coding regions identified a total of 17 open reading frames (ORFs). Compared to plasmid QpH1, 6 ORFs were identical, 5 ORFs were different in size, 6 ORFs were newly generated, and 25 ORFs were lost. It was found that plasmid-homologous sequences in Scurry Q217 were of chromosomal origin.

Base Composition↗
PubMed1995

Detection of multiple boron sites in glasses by 11B satellite transition nuclear magnetic resonance spectroscopy.

The magic-angle spinning sidebands of the satellite transition (ST, m = +/- 3/2 <==> +/- 1/2) for 11B nuclear magnetic resonance (11B ST spectroscopy) have been used to detect multiple boron sites in Na2O-B2O3-SiO2 glasses. The experimental details and data analysis are described, how multiple BO4 and BO3 units can be distinguished using standard magic-angle spinning. For a 16Na2O-30B2O3-53.9SiO2 glass (0.1 MnO) two BO4 units with chemical shifts of -2.5 and 0 ppm were found which differ considerably in their quadrupole interaction. Besides this we found three different BO3 units with approximate chemical shifts of 17, 15, and 19 ppm. The results are compared with earlier measurements.

Boron↗
PubMed1994

Quantitative structural analysis of mullite by 27Al nuclear magnetic resonance satellite transition spectroscopy.

27Al Nuclear magnetic resonance (NMR) satellite transition spectroscopy has been used for the quantitative investigation of the microstructure of polycrystalline 2/1-type mullite (approximately 76 wt.-% Al2O3 and 24 wt.-% SiO2). Using this method the chemical shifts, quadrupole interaction parameters and relative amount of Al in the various coordination polyhedra have been obtained with high accuracy. The additional suppression of second-order quadrupolar broadening of the 27Al magic-angle spinning (MAS) spinning sidebands of the inner satellite transitions allows three different AlO4 units to be detected. The three AlO4 resonances with isotropic chemical shifts at 68, 53 and 45 ppm are associated with AlO4 polyhedra in the tetrahedral double chains [AlO4(T)], the tetrahedra adjacent to the oxygen vacancies [AlO4(T*)] and the tetrahedra AlO4(T') linked by Oc* with AlO4(T*), respectively. Our NMR study of a polycrystalline sample supports the results of previous single-crystal studies of Angel et al. [Am. Mineral., 76 (1991) 332], especially the exclusion of silicon from the tetrahedral sites linked by Oc*.

Aluminum↗
PubMed1993

Determination of distributions of the quadrupole interaction in amorphous solids by 27Al satellite transition spectroscopy.

27Al Satellite transition spectroscopy (SATRAS) has been used to extract both the quadrupole interaction and its distribution width from MAS spectra of glasses. Using this method a measurement at a single magnetic field strength allows one to obtain the true chemical shifts and the quadrupole interaction (and its distributions) with high accuracy, including quantification of the results. In contrast to earlier investigations the central transition MAS lineshapes can be described without assumptions and give correct relative proportions of differently coordinated Al species in glasses. The distribution model for the quadrupole interaction and the resulting MAS lineshapes are discussed in detail including a description of the experimental requirements. Experimental results of 27Al SATRAS spectra of a ternary Al2O3-B2O3-P2O5 glass exhibiting 4-, 5-, and 6-coordinated aluminum species clearly prove different mean values and distribution widths for the quadrupole interaction in the various AlOx polyhedra.

Aluminum↗
PubMed1992

27Al satellite transition spectroscopy (SATRAS) of polycrystalline aluminum borate 9Al2O3.2B2O3.

27Al NMR spectra of polycrystalline aluminum borate 9Al2O3.2B2O3 have been measured at 104, 130 and 156 MHz. The parameters of the quadrupole interaction and the isotropic chemical shifts have been obtained by fitting the CT/MAS pattern and consideration of the inner satellite transitions m = 3/2<-->1/2 and m = - 1/2<-->- 3/2. The gain in spectral resolution concerned with the observation of the MAS lines of the inner satellites leads to complete separation of the signals of AlO6, AlO5 and AlO4 polyhedra. Also signals of structural groups of one and the same coordination number can be distinguished. Experimental and theoretical lineshape calculations are compared.

Aluminum↗