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D Hahn

Publications and source records attributed to D Hahn.

At least 127 records · Page 7Linked to original sources
PubMed1999

[3-dimensional MR coronary angiography in the navigator technic for the primary diagnosis of coronary heart disease: a comparison with conventional coronary angiography].

PURPOSE: Evaluation of three-dimensional MR coronary angiography with the navigator technique for the primary diagnosis of coronary artery disease (CAD) in patients with chest pain. MATERIALS AND METHODS: In this prospective study 20 patients with chest pain were examined with MR coronary angiography and conventional angiography. The three-dimensional MR coronary angiography was performed using a 1.5 T scanner with an ECG-triggered 3D-FLASH-sequence and retrospective respiratory gating in the navigator technique. The MR coronary angiography was evaluated by two radiologists blinded to the results of the conventional coronary angiography. RESULTS: One patient was excluded from further evaluation due to reduced image quality. Conventional coronary angiography excluded CAD in 8/19 patients, 11/19 patients overall showed 20 stenoses (> 50%) or occlusions. With MR coronary angiography, CAD was correctly excluded in 7 patients, one patient was false positive, one patient was false negative. 14/20 stenoses (> 50%) or occlusions were detected, 5 stenoses were diagnosed false positive. Sensitivity and specificity for primary diagnosis of CAD or detection of coronary artery stenoses were 91% and 88% or 70% and 91%, respectively. DISCUSSION: Using MR coronary angiography with the navigator technique in the primary evaluation of CAD, the diagnosis of stenoses or occlusions of the main coronary arteries is feasible.

Adult↗
PubMed1999

Accuracy of methemoglobin measurements: comparison of six different commercial devices and one manual method.

OBJECTIVE: During nitric oxide inhalation, methemoglobinemia needs to be monitored. We compared six commercially available instruments and one manual method for methemoglobin measurements. In addition, we studied whether and to what degree methylene blue interferes with methemoglobin measurements. DESIGN: In vitro methodologic study. SETTING: Research laboratory in a university hospital. PATIENTS: Five healthy volunteers from whom red blood cells were obtained. INTERVENTIONS: Methemoglobinemia was generated in a red blood cell suspension by nitric oxide; methemoglobin was measured with six commercial instruments and one manual photometric method to calculate variation coefficients and to determine the differences between the devices. Methemoglobin was measured with and without the addition of methylene blue with two instruments. Measurements were performed immediately after the addition of methylene blue. MEASUREMENTS AND MAIN RESULTS: All six commercially available instruments had variation coefficients of <0.1 at methemoglobin concentrations of 5%, whereas the manual photometric method did not reach a variation coefficient of <0.1 at 8% of methemoglobin. Apart from two devices that measured slightly but significantly higher methemoglobin levels, all instruments measured similar values of methemoglobin when the same samples were determined simultaneously. Higher concentrations of methylene blue (10, 40, 100 microM) reduced substantially the apparent concentrations of methemoglobin. Interference by methylene blue was most pronounced at low methemoglobin levels. CONCLUSIONS: With some limitations, all commercial instruments that were tested performed adequately for the monitoring of methemoglobinemia. Methylene blue interferes with the methemoglobin measurements in a dose-dependent manner.

Adult↗
PubMed1999

Characterization and identification of numerically abundant culturable bacteria from the anoxic bulk soil of rice paddy microcosms.

Most-probable-number (liquid serial dilution culture) counts were obtained for polysaccharolytic and saccharolytic fermenting bacteria in the anoxic bulk soil of flooded microcosms containing rice plants. The highest viable counts (up to 2.5 x 10(8) cells per g [dry weight] of soil) were obtained by using xylan, pectin, or a mixture of seven mono- and disaccharides as the growth substrate. The total cell count for the soil, as determined by using 4', 6-diamidino-2-phenylindole staining, was 4.8 x 10(8) cells per g (dry weight) of soil. The nine strains isolated from the terminal positive tubes in counting experiments which yielded culturable populations that were equivalent to about 5% or more of the total microscopic count population belonged to the division Verrucomicrobia, the Cytophaga-Flavobacterium-Bacteroides division, clostridial cluster XIVa, clostridial cluster IX, Bacillus spp., and the class Actinobacteria. Isolates originating from the terminal positive tubes of liquid dilution series can be expected to be representatives of species whose populations in the soil are large. None of the isolates had 16S rRNA gene sequences identical to 16S rRNA gene sequences of previously described species for which data are available. Eight of the nine strains isolated fermented sugars to acetate and propionate (and some also fermented sugars to succinate). The closest relatives of these strains (except for the two strains of actinobacteria) were as-yet-uncultivated bacteria detected in the same soil sample by cloning PCR-amplified 16S rRNA genes (U. Hengstmann, K.-J. Chin, P. H. Janssen, and W. Liesack, Appl. Environ. Microbiol. 65:5050-5058, 1999). Twelve other isolates, which originated from most-probable-number counting series indicating that the culturable populations were smaller, were less closely related to cloned 16S rRNA genes.

Alphaproteobacteria↗
PubMed1999

In situ analysis of phototrophic sulfur bacteria in the chemocline of meromictic Lake Cadagno (Switzerland).

Comparative sequence analysis of a 16S rRNA gene clone library from the chemocline of the meromictic Lake Cadagno (Switzerland) revealed the presence of a diverse number of phototrophic sulfur bacteria. Sequences resembled those of rRNA of type strains Chromatium okenii DSM169 and Amoebobacter purpureus DSM4197, as well as those of four bacteria forming a tight cluster with A. purpureus DSM4197 and Lamprocystis roseopersicina DSM229. In situ hybridization with fluorescent (Cy3 labeled) oligonucleotide probes indicated that all large-celled phototrophic sulfur bacteria in the chemocline of Lake Cadagno were represented by C. okenii DSM169, while small-celled phototrophic sulfur bacteria consisted of four major populations with different distribution profiles in the chemocline indicating different ecophysiological adaptations.

Bacteria↗
PubMed1999

Vertical distribution of methanogens in the anoxic sediment of Rotsee (Switzerland).

Anoxic sediments from Rotsee (Switzerland) were analyzed for the presence and diversity of methanogens by using molecular tools and for methanogenic activity by using radiotracer techniques, in addition to the measurement of chemical profiles. After PCR-assisted sequence retrieval of the 16S rRNA genes (16S rDNA) from the anoxic sediment of Rotsee, cloning, and sequencing, a phylogenetic analysis identified two clusters of sequences and four separated clones. The sequences in cluster 1 grouped with those of Methanosaeta spp., whereas the sequences in cluster 2 comprised the methanogenic endosymbiont of Plagiopyla nasuta. Discriminative oligonucleotide probes were constructed against both clusters and two of the separated clones. These probes were used subsequently for the analysis of indigenous methanogens in a core of the sediment, in addition to domain-specific probes against members of the domains Bacteria and Archaea and the fluorescent stain 4', 6-diamidino-2-phenylindole (DAPI), by fluorescent in situ hybridization. After DAPI staining, the highest microbial density was obtained in the upper sediment layer; this density decreased with depth from (1.01 +/- 0.25) x 10(10) to (2.62 +/- 0.58) x 10(10) cells per g of sediment (dry weight). This zone corresponded to that of highest metabolic activity, as indicated by the ammonia, alkalinity, and pH profiles, whereas the methane profile was constant. Probes Eub338 and Arch915 detected on average 16 and 6% of the DAPI-stained cells as members of the domains Bacteria and Archaea, respectively. Probe Rotcl1 identified on average 4% of the DAPI-stained cells as Methanosaeta spp., which were present throughout the whole core. In contrast, probe Rotcl2 identified only 0.7% of the DAPI-stained cells as relatives of the methanogenic endosymbiont of P. nasuta, which was present exclusively in the upper 2 cm of the sediment. Probes Rotp13 and Rotp17 did not detect any cells. The spatial distribution of the two methanogenic populations corresponded well to the methane production rates determined by incubation with either [14C]acetate or [14C]bicarbonate. Methanogenesis from acetate accounted for almost all of the total methane production, which concurs with the predominance of acetoclastic Methanosaeta spp. that represented on average 91% of the archaeal population. Significant hydrogenotrophic methanogenesis was found only in the organically enriched upper 2 cm of the sediment, where the probably hydrogenotrophic relatives of the methanogenic endosymbiont of P. nasuta, accounting on average for 7% of the archaeal population, were also detected.

Anaerobiosis↗
PubMed1999

Three-dimensional MR coronary angiography using the navigator technique compared with conventional coronary angiography.

OBJECTIVE: We evaluated the diagnostic accuracy of three-dimensional (3D) MR coronary angiography with the navigator technique for the detection of coronary artery stenoses in comparison with that of conventional radiographic angiography. SUBJECTS AND METHODS: Thirty patients with coronary artery disease were examined with an ECG-triggered 3D fast low-angle shot sequence using retrospective respiratory gating and the navigator technique on a 1.5-T MR scanner. The data set was evaluated as a 3D view with a surface rendering technique. RESULTS: Imaging of the proximal coronary arteries was possible in all patients. The average visualized lengths of the left main, left anterior descending, left circumflex, and right coronary arteries were 1.9+/-0.5 cm (mean +/- SD), 5.2+/-2.3 cm, 4.2+/-1.9 cm, and 5.2+/-2.5 cm, respectively. Irregular breathing reduced image quality in seven of the 30 patients, making diagnosis of stenoses impossible. In the 77% of patients whose examinations resulted in high-quality images, the sensitivity and specificity for detection of significant stenoses and occlusions in all four main coronary arteries were 81% and 89%, respectively. CONCLUSION: The navigator technique allows reproducible imaging of the proximal course of coronary arteries. This technique obviates breath-hold studies, thus allowing more patients to be examined. In patients whose examinations resulted in high-quality images, significant coronary artery lesions could be seen. However, for widespread clinical use, further technical improvement is necessary to increase sensitivity and specificity.

Adult↗
PubMed1998

Human small intestinal maltase-glucoamylase cDNA cloning. Homology to sucrase-isomaltase.

It has been hypothesized that human mucosal glucoamylase (EC 3.2.1. 20 and 3.2.1.3) activity serves as an alternate pathway for starch digestion when luminal alpha-amylase activity is reduced because of immaturity or malnutrition and that maltase-glucoamylase plays a unique role in the digestion of malted dietary oligosaccharides used in food manufacturing. As a first step toward the testing of this hypothesis, we have cloned human small intestinal maltase-glucoamylase cDNA to permit study of the individual catalytic and binding sites for maltose and starch enzyme hydrolase activities in subsequent expression experiments. Human maltase-glucoamylase was purified by immunoisolation and partially sequenced. Maltase-glucoamylase cDNA was amplified from human intestinal RNA using degenerate and gene-specific primers with the reverse transcription-polymerase chain reaction. The 6,513-base pair cDNA contains an open reading frame that encodes a 1,857-amino acid protein (molecular mass 209,702 Da). Maltase-glucoamylase has two catalytic sites identical to those of sucrase-isomaltase, but the proteins are only 59% homologous. Both are members of glycosyl hydrolase family 31, which has a variety of substrate specificities. Our findings suggest that divergences in the carbohydrate binding sequences must determine the substrate specificities for the four different enzyme activities that share a conserved catalytic site.

Amino Acid Sequence↗
PubMed1998

[SieScape panorama imaging in radiologic diagnosis].

Through high-performance computer processing it has become possible to realize a new ultrasound imaging process: SieScape imaging. This method provides extended field of view images in real time using successive ultrasound images obtained when a standard transducer is scanned over a distance of up to 60 cm without any position sensor. SieScape offers new possibilities to view topographical anatomy. It is especially advantageous for scanning extended and tubular structures as well as large and enlarged organs and big pathologic volumes. Parallel scanning sequences allow documentation comparable to that of computed tomography. In addition, just as in magnetic resonance, variable imaging planes can be realized. The following describes the results obtained with SieScape in a multitude of clinical applications, especially in examinations of throat, thoracic and abdominal walls, breast, and intraabdominal organs as well as the soft tissues and small vessels of the extremities. The experience gathered with SieScape imaging--its advantages as well as its potential limitations, such as the formation of artefacts--is described.

Equipment Design↗
PubMed1998

Dehalobacter restrictus gen. nov. and sp. nov., a strictly anaerobic bacterium that reductively dechlorinates tetra- and trichloroethene in an anaerobic respiration.

The highly enriched anaerobic bacterium that couples the reductive dechlorination of tetrachloroethene to growth, previously referred to as PER-K23, was obtained in pure culture and characterized. The bacterium, which does not form spores, is a small, gram-negative rod with one lateral flagellum. It utilized only H2 as an electron donor and tetrachloroethene and trichloroethene as electron acceptors in an anaerobic respiration process; it could not grow fermentatively. Acetate served as a carbon source in a defined medium containing iron as the sole trace element, the two vitamins thiamine and cyanocobalamin, and the three amino acids arginine, histidine, and threonine. The cells contained menaquinones and b-type cytochromes. The G+C content of the DNA was 45.3 +/- 0.3 mol%. The cell wall consisted of type-A3gamma peptidoglycan with ll-diaminopimelic acid and one glycine as an interpeptide bridge. The cells are surrounded by an S-layer; an outer membrane was absent. Comparative sequence analysis of the 16S rRNA sequence showed that PER-K23 is related to gram-positive bacteria with a low G+C content of the DNA. Based on the cytological, physiological, and phylogenetic characterization, it is proposed to affiliate the isolate to a new genus, Dehalobacter, with PER-K23 as the type strain of the new species Dehalobacter restrictus.

Anaerobiosis↗
PubMed1998

A review of Takayasu's arteritis in children in Gauteng, South Africa.

We have reviewed 31 patients with Takayasu's arteritis followed at two pediatric nephrology units in Gauteng, South Africa over a 15-year period. There were 25 black patients, 4 white, and 2 of mixed race. The mean age at diagnosis was 8.42+/-3.59 (range 2.4-14.5, median 8) years. The most common presenting sign was hypertension, followed by cardiac failure, bruits, and absent pulses. The Mantoux test was strongly positive in 27 patients (90%, control population 5%). Markers of activity included a raised erythrocyte sedimentation rate (23 patients) or Gallium single photon emission tomography (positive in 12 of 16 patients). Angiography revealed type II (abdominal aorta) and III (arch plus abdominal aorta) lesions to be most common (11 in each group). All patients received antituberculous therapy and most low-dose aspirin for its antithromboxane effect. Corticosteroids and further immunosuppression were used to control disease activity. We added total lymphoid irradiation (TLI) or cyclophosphamide. Twenty-six patients in all received further immunosuppression, with 13 patients in each group. Results were similar in the two groups, with similar pre- and posttherapy systolic blood pressures and creatinine clearances. Two patients in each group relapsed, 3 died in the TLI group and 2 in the cyclophosphamide group. Surgical intervention, usually in the quiescent phase, consisted mainly of renal autotransplantation. Because of the problems with TLI and 2 patients with papillary carcinoma of the thyroid with long-term follow-up, we no longer use TLI. We have shown that with active medical and surgical intervention the aggressive course of this disease in children can be modified.

Adolescent↗
PubMed1998

Invasion of cytotrophoblastic JEG-3 cells is stimulated by hCG in vitro.

Trophoblast invasion into the uterine wall is controlled by many factors. Previously, a human chorionic gonadotropin (hCG) receptor has been found to be expressed on invasive trophoblast as well as on choriocarcinoma cells implying a possible role for the hormone in trophoblast invasion. Therefore, this study examined the role of hCG in the invasion of trophoblastic (JEG-3) cells. Increasing hCG concentrations were applied in a trophoblast invasion model, JEG-3, through matrigel-coated filters. The proliferation was quantified by WST-1 cleavage assay. Cell migration was studied by examining the number of cells that had passed the uncoated porous (8-microm pore size) filters. After staining, filters were examined microscopically for cells on the underside of the membrane. A quantitative protease assay was also performed. Flow cytometric analysis of alpha5 and alpha6 integrin subunits, which are essential for interactions between cells and extracellular matrix, was performed. hCG increased significantly (P<0.01) the in vitro invasion of trophoblastic JEG-3 cells in a dose-dependent manner. Migration was also increased by hCG (P<0.01). However, cell proliferation remained unchanged. The second messenger analogue dibutyryl cAMP (db cAMP) and the cAMP elevating factor (forskolin) mimicked the effects of hCG by stimulating a dose-dependent increase of trophoblastic cell UEG-3) invasion. The collagenolytic activity of trophoblastic cells (EG-3) was increased by hCG stimulation. No changes were shown in the expression of alpha5 and alpha6 integrin subunits on JEG-3 cells. In vitro hCG is a regulatory factor of invasion and migration in trophoblastic JEG-3 cells, whereas proliferation is not influenced. The endogenous production of hCG by the trophoblast in vivo implies an autocrine control of invasion processes by hCG.

Bucladesine↗
PubMed1998

Analysis of broad-scale differences in microbial community composition of two pristine forest soils.

Broad-scale differences in soil microbial community composition were analyzed in two contrasting soils using DNA reassociation and % G + C profiles for analysis on the community-level, and filter- and whole cell hybridization techniques for a coarse-level characterization of larger phylogenetic groups of bacteria. Reassociation analysis of DNA from bacterial fractions extracted from the organic soil Seim and the mineral soil Hau revealed similar complexity of the communities with 5700 and 4900 different bacterial genomes (g soil [dry wt])-1, respectively. Thermal denaturation studies showed wide % G + C distributions in DNA from bacteria of both soils. Differences in the median % G + C with 55 to 61% for the bacterial community in soil Seim and 61 to 66% for that in soil Hau indicated a higher proportion of bacteria with a high DNA G + C content in soil Hau. In situ hybridization with fluorescent (Cy3-labeled) probes targeting larger phylogenetic groups showed minor differences between both soils, and between direct detection of bacteria in dispersed soil slurries and in bacterial fractions extracted from soils through about 90% of the total bacteria were lost during extraction. In dispersed slurries of both soils, only probes ALF1b, SRB385, and PLA46 hybridized to cells accounting for more than 1% of the DAPI-stained cells, while numbers obtained after hybridization with probes ARCH915, BET42a, GAM42a, HGC69a, and CF319a were below the detection limit set at < 1%. These results were confirmed by in situ hybridization with horseradish peroxidase (HRP)-labeled probes and subsequent Cy3-tyramide signal amplification. In contrast, dot blot hybridization with probe HGC69a indicated significant amounts of Gram-positive bacteria with a high DNA G + C content in both soils. These could subsequently be visualized in non-dispersed soil slurries by in situ hybridization with HRP-labeled probe HGC69a and Cy3-tyramide signal amplification. Filamentous Gram-positive bacteria with a high DNA G + C content, likely actinomycetes, which are present in soil Hau in significant numbers are obviously destroyed by procedures used for soil dispersion.

Actinomycetales↗
PubMed1998

The Calvin cycle enzyme sedoheptulose-1,7-bisphosphatase is encoded by a light-regulated gene in Chlamydomonas reinhardtii.

We have studied the light-dependent expression of the Chlamydomonas reinhardtii csbp gene encoding sedoheptulose-1,7-bisphosphatase (SBPase), an enzyme of the pentose-phosphate pathway. Expression studies using light/dark-synchronized cultures revealed that csbp mRNA abundance increases significantly during illumination. We have used a 1.4 kb region upstream of the csbp gene in transcriptional fusions to the homologous arylsulfatase-encoding reporter gene (ars). In transformants carrying the chimeric csbp/ars reporter gene, arylsulfatase activity is detected in the absence of sulfate, a condition under which the endogenous ars gene is repressed. Moreover, ars mRNA accumulation is dramatically stimulated by light, indicating that 1.4 kb of the csbp 5'-untranslated region are sufficient to confer light-dependent expression on the ars reporter gene.

Animals↗
PubMed1998

[Value of color-coded duplex ultrasound in evaluating arm blood vessels--arteries and hemodialysis shunts].

AIM: Comparison of colour coded duplex sonography (CCDS) to angiography in visualizing arteries and haemodialysis fistulas of the upper extremity. METHOD: 1145 arterial and vein segments were visualised using CCDS and angiography in 219 patients by different examiners with different degrees of experience. Sensitivity, specificity and accuracy were calculated. RESULTS: For the arterial segments--subclavian artery up to the distal lower arm arteries--the sensitivity was 90% and the specificity 99%. The sensitivity for the detection of vascular alterations in haemodialysis fistulas was 89% and the specificity 95%. CONCLUSION: CCDS may be able to replace diagnostic angiography of the arm except when evaluating the hand arteries and the central veins.

Adult↗
PubMed1998

[In vitro studies to determine the degree of stenosis using spiral CT angiography].

UNLABELLED: Aim of the study was to evaluate the influence of different spiral-CT parameters for the visualisation of vascular stenoses, especially of the renal arteries. MATERIAL AND METHODS: Models with a density equivalent to that of fat, filled with diluted contrast agent, and an inner lumen of 4, 6, 8 mm were scanned in x-, y- and z-direction. Data were acquired in up to 24 second long spiral-CT scans using different spiral-CT parameters (collimation, table speed, reconstruction algorithm, tube current). Detection of the degree of stenosis was achieved by assessment of the axial images and 3D reconstructions. RESULTS: The best correlation between real and measured degree of stenosis was seen by using a small collimation, a low table increment and assessment of the axial images reconstructed in standard algorithm. The stenosis degrees of models directed in x- and y-direction were overestimated and those in z-direction were underestimated depending on the spiral-CT parameters. CONCLUSION: For optimal imaging of renal artery stenoses, collimation of 2 mm (pitch = 1-2 and a reconstruction interval of 1 mm is recommended.

Algorithms↗