Biomedical subjects

K Bachmann

Publications and source records attributed to K Bachmann.

At least 37 records · Page 2Linked to original sources

PubMed1999

Evolution of the chloroplast genome and polymorphic ITS regions in Allium subg. Melanocrommyum.

Relationships based on PCR-RFLPs of non-coding regions of cpDNA indicate that some of the largest subgenera of the genus Allium and five of the largest sections of the Central Asian subg. Melanocrommyum are artificial. Internested synapomorphic mutations without homoplasy were found only in the chloroplast genomes of plants of subg. Melanocrommyum that occur in the border region of Tajikistan, Uzbekistan, Afghanistan, and Kyrgyzstan. Eighteen of 49 plants surveyed were polymorphic for their ITS regions. Even plants that had identical chloroplast genomes were polymorphic for nuclear ribosomal regions. These individuals had markedly different frequencies of ITS variants that were detected with various restriction enzymes. The geographic partitioning of chloroplast haplotypes and the fact that the ITS variants could not be ordered hierarchically can readily be envisioned to result from gene flow. Processes such as concerted evolution and parallel morphological evolution may also be partly responsible for the disconcordance of mutations in the chloroplast and nuclear genome. However, the chimeric nature of the nuclear ribosomal regions indicates that concerted evolution is not the dominating process in Allium subg. Melanocrommyum.

Allium↗

PubMed1999

RAPDs and noncoding chloroplast DNA reveal a single origin of the cultivated Allium fistulosum from A. altaicum (Alliaceae).

The origin of the crop species Allium fistulosum (bunching onion) and its relation to its wild relative A. altaicum were surveyed with a restriction fragment length polymorphism (RFLP) analysis of five noncoding cpDNA regions and with a random amplified polymorhic DNA (RAPD) analysis of nuclear DNA. Sixteen accessions of A. altaicum, 14 accessions of A. fistulosum, representing the morphological variability of the species, and five additional outgroup species from Allium section Cepa were included in this study. The RFLP analysis detected 14 phylogenetically informative character transformations, whereas RAPD revealed 126 polymorphic fragments. Generalized parsimony, neighbor-joining analysis of genetic distances, and a principal co-ordinate analysis were able to distinguish the two species, but only RAPD data allowed clarification of the interrelationship of the two taxa. The main results of this investigation were: (1) A. fistulosum is of monophyletic origin, and (2) A. fistulosum originated from an A. altaicum progenitor, making A. altaicum a paraphyletic species. Compared with A. altaicum the cultivated accessions of the bunching onion show less genetic variability, a phenomenon that often occurs in crop species due to the severe genetic bottleneck of domestication. Allium altaicum and A. fistulosum easily hybridize when grown together, and most garden-grown material is of recent hybrid origin.

Journal Article↗

PubMed1999

Chloroplast DNA evidence for the evolution of Microseris (Asteraceae) in Australia and New Zealand after long-distance dispersal from western North America.

Restriction site mutations and trnL(UAA)-trnF(GAA) intergenic spacer length variants in the chloroplast genome were used to investigate the phylogenetic relationships among 53 Australian and New Zealand Microseris populations and to assess their position within their primarily North American genus. The study was performed to enhance understanding of evolutionary processes within this unique example of intercontinental dispersal and subsequent adaptive radiation. A southern blot method using four-base restriction enzymes and fragment separation on polyacryamide gels resulted in 55 mutations of which 30 were potentially phylogenetically informative. Most mutations were small indels of <162 bp, 80% of which were <20 bp. The small indels were useful for phylogenetic reconstruction of Australasian Microseris as judged by the high consistency indexes. The results confirmed the monophyly of the Australian and New Zealand Microseris. The occurrence of "hard" basal polytomies in the most parsimonious trees indicated that rapid radiation has occurred early in the history of the taxon. The monophyly of M. lanceolata, which includes the self-incompatible ecotypes of the Australian mainland, was confirmed. Within this species three clades were found that reflect more geographic distribution than morphological entities, suggesting that migration and possibly introgression between different ecotypes, or parallel evolution of similar adaptations, has occurred. One of the three clades was supported by a 162-bp deletion in the trnL-trnF spacer, while a subgroup of this exhibited also a tandemly repeated trnF exon. The data were inconclusive about the monophyly of the second Australasian species, M. scapigera, which comprises the New Zealand, Tasmanian, and autofertile ecotypes of Australia.

Journal Article↗

PubMed1998

Noninvasive coronary angiography by contrast-enhanced electron beam computed tomography.

Electron beam computed tomography (EBCT) is a cross-sectional imaging method with high temporal and spatial resolution. So far, it has mainly been applied for the detection of coronary artery calcifications which permit the very sensitive detection of coronary atherosclerosis even in the very early stages. However, after intravenous injection of a contrast agent, EBCT also permits the direct visualization of the coronary artery lumen. For these investigations, a volume data set is acquired that consists of 40 axial cross-sections of the heart (3 mm slice thickness). To evaluate the coronary arteries as to the presence of stenoses and occlusions, various forms of post-processing, including shaded surface display, maximum intensity projection, and multiplanar reconstruction, are applied. The sensitivities and specificities for the detection of coronary artery stenoses and occlusions are about 90%. Best results are obtained for coronary artery bypass grafts, the left main coronary artery, and the left anterior descending coronary artery, while reduced image quality impairs the results for the right coronary artery and the left circumflex coronary artery.

Contrast Media↗

PubMed1998

[Prenatal recording of fetal heart action with magnetocardiography].

Fetal magnetocardiography (fMCG) registers the magnetic field generated by the fetal heart. In contrast to the fetal electrocardiogram, fECG permits non-invasive registration of fetal heart activity and documentation of all parts of the PQRST-wave-forms from the second trimenon onwards. This facilitates the determination of cardiac time intervals and establishment of reference values for different stages of pregnancy. We examined 53 women in 104 recordings from the 10th week of gestation onwards (1 to 10 recordings per individual). The fMCG (37 magnetic channels, sampling rate 1024 Hz, bandwidth 1-200 Hz) was recorded non-invasively over the mother's abdomen in a magnetically shielded room. Registration of fetal heart beats was generally successful from the 20/21th week of gestation onwards. In a few cases, fetal heart beats could be registered as early as in the 16th week. Cardiac time intervals and amplitudes of fMCG increased concordantly with fetal growth. Mean P wave duration increased from 31 to 49 ms (p < 0.05), PQ interval from 95 to 107 ms (n.s.) and QRS duration from 36 to 52 ms (p < 0.01). The mean amplitudes of the P and R waves also increased. FMCG, furthermore permits a prenatal diagnosis of fetal cardiac arrhythmias. We recorded fetal arrhythmias in 20 cases (26-38th week), including episodes of ventricular and supraventricular arrhythmias or atrioventricular blockings. Due to its high resolution, fMCG offers new information on the development of fetal cardiac activity which cannot be achieved by conventional methods like cardiotocography or dopplerultrasound. Therefore, fMCG could become a new diagnostic instrument for monitoring fetal wellbeing during pregnancy.

Adult↗

PubMed1998

[Evaluation of coronary artery stenosis with respiratory gated NMR angiography].

Respiratory gated MR coronary angiography is a new MR imaging technique which permits reconstruction of the coronary arteries from a three-dimensional data set obtained from contiguous parallel sections. In this study, respiratory gated MR angiography was applied to assess significant coronary artery stenoses (> or = 50%). MR imaging was performed in 68 patients (50 men, 18 women) who had been referred to cardiac catheterization because of suspected or known coronary artery disease. The evaluation of coronary artery stenoses was performed in a blinded manner in the proximal, middle, and distal vessel segments after multiplanar coronary reconstruction of the MR images. Of the 680 coronary segments, 275 (40%) were located outside the imaging volume and were, therefore, excluded from further analysis. The highest sensitivity for stenosis detection was found in the proximal left anterior descending (LAD) and right coronary artery (RCA) with 75% and 71%, respectively. The overall sensitivity, however, was low with 48%. The overall specificity was 92%. The positive and negative predictive values were 67% and 85%, respectively. This study shows that significant coronary artery stenoses, especially in the proximal LAD and RCA, can be correctly identified using respiratory gated MR angiography. However, further technical improvements are necessary before this method may become a reliable diagnostic tool in clinical practice.

Adult↗

PubMed1998

[Possibilities and limits of electron beam tomography].

Electron beam CT, which does not require mechanical movement of an X-ray tube, has a temporal resolution which exceeds that of conventional computed tomography by a factor of about ten. Axial images of the heart can be acquired within 50 to 100 ms with a spatial resolution below 0.5 mm2 and permit precise visualization of all cardiac structures. ECG-triggered acquisition of 30 to 40 axial images (3 mm slice thickness) in a short inspiratory breathhold allows one to sample a 3-dimensional volume data set which covers the complete heart. Overall acquisition times are approximately 30 to 50 seconds. While electron beam CT in general permits a complete cardiac investigation, including morphology, function, and perfusion, the method's most important application is non-invasive imaging of the coronary arteries. Without contrast enhancement, coronary calcifications by EBCT currently constitutes the most sensitive non-invasive marker for the presence even of very early forms of coronary atherosclerosis. Intravenous injection of contrast agent during image acquisition additionally permits the selective visualization of the coronary artery lumen and detection of significant stenoses. This method is especially well suited in the follow-up of coronary interventions and coronary bypass grafting. Breathhold and movement artifacts, superposition of coronary arteries and veins, as well as severe coronary calcifications currently constitute the method's main problems. In spite of these limitations, electron beam CT has been shown to permit clinically valuable non-invasive investigations of the coronary arteries, which may be further refined as technology progresses.

Adult↗

PubMed1998

[Anti-bradycardia ventricle stimulation during the vulnerable phase of the heart cycle in ICD system with DDD cardiac pacemaker function].

We report a case of a 56-year-old white female with an ICD system (Ventak AV, CPI) implanted because of repeated episodes of ventricular fibrillation and preexisting intermittent total AV-block. Several times asynchronic stimulation could be observed in the case of ventricular extrasystole stimulating the ventricle during different times of depolarization. The reason for undersensing of the premature ventricular complexes was a blanking period of 66 ms after atrial stimulation. Therefore, the ICD was not able to sense the ventricular extrasytole and the stimulation of the ventricle occurred during the vulnerable period of the heart cycle. Induction of severe ventricular arrhythmia was not documented. Because of missing programmability of the ventricular blanking period, no possibility of a safety stimulation, and already maximal sensitivity of the ICD, the incidence of these events could only be reduced by increasing the lower rate limit of the pacemaker and suppression of the premature ventricular complexes by medication.

Cardiac Complexes, Premature↗

PubMed1998

Evaluation of the Association Between Coronary Calcification Detected by Electron Beam Computed Tomography and Atherosclerosis of Extracranial Carotid Arteries In Vivo.

The aim of this study was to evaluate the association between carotid and coronary atherosclerosis and their diagnostic value for predicting angiographically significant coronary artery disease (CAD). We investigated 80 subjects (mean age 55 +/- 8 years) by electron beam computed tomography (EBT), the most sensitive technology for noninvasive detection of coronary calcification (a marker of coronary atherosclerosis); by carotid sonography; and by coronary angiography. Carotid ultrasound was performed with a 7.5 MHz Duplex probe, EBT was done with an EVOLUTION(R) scanner. In 47 subjects, coronary calcification as well as carotid atherosclerosis was present. Thirteen subjects showed isolated coronary calcification, 10 had isolated carotid atherosclerosis, and 10 showed neither coronary calcification nor carotid atheroscleroosis. The association between carotid atherosclerosis and CAD as well as the relationship between coronary calcification and CAD were statistically significant (p < 0.05), but the correlation between coronary calcification and CAD was higher than between carotid atherosclerosis and CAD (Pearson contingency coefficient: 0.34 vs 0.86). In subjects without carotid atherosclerosis, the mean area of coronary calcificiation was significantly (p < 0.01) lower (41 mm2) than in subjects with carotid atherosclerosis (113 mm2). For noninvasive detection of CAD, electron beam CT was superior to carotid sonography on sensitivity (95% vs 78%) and specificity (81% vs 48%). Former studies suggested that sonography of extracoronary vessels could aid in screening for CAD. In our study, the sonographic status of carotid arteries was associated with cardiovascular atherosclerosis but it did not allow us to make a judgment about the presence of CAD with sufficient reliability and it was inferior to electron beam CT as a noninvasive marker of CAD.

Journal Article↗

PubMed1998

Natural course of angiographic parameters after myocardial infarction: an evaluation in the prethrombolytic and pre-angiotensin converting enzyme inhibition era.

BACKGROUND: After myocardial infarction, left ventricular dilation is a frequent cause of cardiac insufficiency, which is associated with high morbidity and mortality. In this angiographic study, the natural course of postinfarction ventricular dilation could be followed up because patients undergoing revascularization procedures were excluded and only some few patients received angiotensin-converting enzyme inhibitors. METHODS AND RESULTS: Of 85 patients suffering from angina after myocardial infarction, 59 could be examined twice by angiocardiography in a mean interval of 52 +/- 14 months; 37 of the 59 patients had sustained posterior myocardial infarction, 20 had anterior myocardial infarction, and 2 had both. During follow-up, end-diastolic volume index increased from 100 +/- 27 mL/m2 to 110 +/- 34 mL/m2; in 26 of the 59 patients the increase was greater than 15 mL/m2. Irrespective of the time since infarction, patients with an end-diastolic volume index greater than 100 mL/m2 and an ejection fraction less than 50% at the time of first angiography were at high risk of progressive ventricular dilation and further deterioration of left ventricular function (for both, P = .003). This process was independent of extent of coronary artery involvement and coronary disease progression. Multivariate analysis identified ejection fraction at the time of index angiography as the strongest predictor of further left ventricular dilation (P = .0004). CONCLUSIONS: Continuing left ventricular dilation occurs in less than half the patients who had myocardial infarction. Left ventricular ejection fraction is the most sensitive parameter to predict the risk of ventricular dilation after infarction.

Adult↗

PubMed1998

Comparison of vessel diameters in electron beam tomography and quantitative coronary angiography.

Electron beam tomography (EBT) has been shown to permit non-invasive imaging of the coronary arteries after intravenous injection of contrast agent and 3-dimensional reconstruction. We compared the vessel diameters in EBT reconstructions to quantitative coronary angiography (QCA). 10 patients were investigated by EBT and QCA. 3-dimensional EBT reconstructions (shaded surface display) were performed after acquisition of 40 axial cross-sections of the heart with 3 mm slice thickness (1 mm overlap) which were obtained triggered to the ECG in breathhold following intravenous injection of 120-160 ml of contrast agent. A fixed lower reconstruction threshold of 80 HU was used to selectively visualize the contrast-enhanced coronary artery lumen. At 60 sites in the coronary artery system, the vessel diameters measured in the EBT reconstructions were compared to the diameters found in quantitative analysis of the patients' coronary angiograms. The correlation coefficient of the vessel diameters in EBT and QCA was 0.83. Mean vessel diameters were not significantly different in EBT and QCA (3.06 +/- 0.93 vs. 2.97 +/- 0.94 mm). However, very small vessel diameters tended to be underestimated in the EBT reconstructions, which was due to the partial volume effect. It only vessel diameters measured in the left main or left anterior descending coronary artery were compared to QCA, the correlation increased to 0.87, since these vessel segments are less prone to artifacts in the EBT investigation. Vessel diameters in EBT and QCA correlated reasonably well. Due to partial volume effects, the diameter of very small vessels and stenotic segments tends to be underestimated by EBT.

Adult↗

PubMed1998

Assessment of coronary blood flow in humans using phase difference MR imaging. Comparison with intracoronary Doppler flow measurement.

Coronary blood flow quantification provides essential information on the hemodynamic significance of coronary artery stenoses. Recently, magnetic resonance (MR) flow mapping has emerged as a new promising method to noninvasively determine flow velocity and flow volume within the coronary arteries. The aim of this study was to compare phase difference (PD) MR flow quantification with intracoronary Doppler flow measurements in 15 patients with suspected or known coronary artery disease. Flow quantification was attempted before and after systemic application of 5mg Isosorbiddinitrate (ISDN) in order to determine possible alterations in coronary flow volume. PD MR flow mapping was performed successfully in 13 of the 15 patients. For flow velocities and flow volume values, a close correlation between PD MR and Doppler flow measurements was found (r = 0.79 and r = 0.90, respectively). However, average flow measured by PD MR was significantly lower than the invasively obtained values (9.0 +/- 4.4 cm/sec vs. 11.7 +/- 4.9 cm/sec; p < 0.001 and 46.3 +/- 28.7 ml/min vs. 53.4 +/- 32.8 ml/min; p < 0.05). Although the mean flow volume remained constant in the entire patient group after ISDN application, individual changes (increase in 6, decrease in 4 cases) could be documented with PD MR imaging and showed a good correlation to the Doppler method (r = 0.82). In conclusion, PD MR flow mapping is a promising method for the noninvasive quantification of coronary blood flow and therefore offers the potential of assessing coronary artery stenoses. However, technical improvements are mandatory in order to increase accuracy of the method.

Blood Flow Velocity↗

PubMed1998

Poststenotic coronary blood flow following percutaneous transluminal coronary angioplasty.

Poststenotic intracoronary flow velocity measurements both prior to and following percutaneous transluminal coronary angioplasty (PTCA) by use of a Doppler-tipped guidewire allow estimation of haemodynamic improvement due to interventional procedures. Since poststenotic coronary artery vasoconstriction routinely occurs after PTCA, haemodynamic improvement may be overestimated when measured by flow velocity alone. In 38 patients scheduled for elective PTCA in single vessel disease (left anterior descending = 19; left circumflex = 9; right coronary artery = 10) change of poststenotic coronary blood flow (CBF) was calculated by the combined use of intracoronary flow velocity measurement (average peak velocity: APV) and quantitative coronary angiography (cross sectional area: CSA) both prior to and following PTCA. Poststenotic coronary diameters revealed a small but significant decrease following PTCA (2.9 +/- 0.5 versus 2.7 +/- 0.5 mm, p < 0.001, 33 of 38 analysed vessels, i.e. 86.8%), whereas APV demonstrated a significant increase due to PTCA (17.0 +/- 8 versus 41.5 +/- 16, p < 0.001). Along with the increment in poststenotic flow velocity, poststenotic CBF increased highly significantly following PTCA (33 +/- 25 versus 73 +/- 41 ml min(-1), p < 0.001). In spite of a significant decrease in poststenotic coronary diameter, a highly significant increment of poststenotic flow due to PTCA can be demonstrated paralleling increment of poststenotic coronary Doppler-flow velocity.

Angioplasty, Balloon, Coronary↗

PubMed1998

Effect of montelukast on single-dose theophylline pharmacokinetics.

The effect of montelukast (MK-0476), a cysteinyl leukotriene receptor antagonist in development for treatment of asthma, on single-dose theophylline plasma concentrations was studied in three separate clinical trials. Montelukast was evaluated at 10 mg once daily (the clinical dosage), 200 mg once daily, and 600 mg (200 mg three times daily). At the clinical dosage, montelukast did not change single-dose theophylline plasma concentration in a clinically important manner. The geometric mean ratios for theophylline area under the plasma concentration versus time curve (AUC0-->infinity ) (0.92) and maximal plasma concentration (Cmax ) (1.04) were well within the predefined and generally accepted bioequivalence range of 0.80 and 1.25. Montelukast decreased theophylline Cmax by 12% and 10%, AUC0-->infinity by 43% and 44%, and elimination half-time by 44% and 39% at 200 mg/d (oral and intravenous, respectively), and at 600 mg/d, montelukast decreased theophylline Cmax by 25%, AUC0-->infinity by 66%, and elimination half-time by 63%. These results show that montelukast at the clinical dosage did not change theophylline pharmacokinetics in a clinically important manner, but at 20- to 60-fold higher dosages, montelukast significantly reduced the theophylline pharmacokinetics parameters; an apparent dosage dependence is suggested.

Acetates↗

PubMed1998

Impedance rise, only clue to severe insulation damage in a transvenous single-lead AICD-system.

We report a case of severe insulation damage 10 months after implantation of a fourth-generation single-lead implantable cardioverter defibrillator in a 45-year-old patient with dilative cardiomyopathy. The measured impedance was > 2000 Ohm and decreased to < 100 Ohm after slight pressure was applied to the device. All other parameters including intracardiac ECGs and markers were normal. Despite this delicate finding operative exploration revealed severe insulation damage of the pace-sense arm of the plug and insulation loss proximal to the distal coil of the lead.

Cardiomyopathy, Dilated↗

PubMed1998

Microsatellite enrichment in organisms with large genomes (Allium cepa L.).

To exploit the polymorphism of repeat numbers in short tandem repeat (STR) sequences (microsatellites) as molecular markers, STRs must be isolated and PCR primers must be developed in flanking sequences. In species with large genomes such as Allium cepa L. (onion and shallot), an efficient selection procedure for genomic fragments containing STRs is a crucial step. Here we describe a nonradioactive method for microsatellite isolation based on affinity capture of single-stranded restriction fragments annealed to biotinylated microsatellite oligonucleotides (CA)10, (GAA)8 and (AAC)8 followed by adapter-mediated genomic PCR. Cloning of the products in E. coli and plasmid sequencing revealed more than 60% positive clones. Primers were designed in STR-flanking regions, and one or two bands were amplified in 13 diploid onion and five shallot accessions. Allelism of the bands was confirmed by product sequencing.

Dinucleotide Repeats↗

PubMed1998

Curved multiplanar reconstructions for the evaluation of contrast-enhanced electron beam CT of the coronary arteries.

OBJECTIVE: We investigated the applicability of curved multiplanar reconstructions for the evaluation of contrast-enhanced electron beam CT scans of the coronary arteries. SUBJECTS AND METHODS: Thirty-two patients (43-72 years old; mean age, 58 years old) underwent electron beam CT. After injection of i.v. contrast medium, 40 axial cross sections of the heart were acquired, triggered to the ECG during breath-hold (3-mm slice thickness, 1-mm overlap). Curved multiplanar reconstructions were obtained separately for each coronary artery. The reconstructions were independently evaluated by two investigators for the presence of high-grade stenoses and occlusions. The results were then compared with coronary angiography results, of which the two investigators had been unaware. RESULTS: Because of degraded image quality, 15 (12%) of the 128 vessels (left main, left anterior descending, left circumflex, and right coronary arteries in 32 patients) were excluded from evaluation. In the remaining 113 vessels, 16 (89%) of 18 high-grade stenoses and occlusions were correctly detected (89% sensitivity). Absence of significant stenosis was correctly detected in 87 (92%) of 95 vessels (92% specificity). The negative and positive predictive values were 98% and 67%, respectively. CONCLUSION: Curved multiplanar reconstructions are useful in the evaluation of contrast-enhanced electron beam CT scans of coronary arteries.

Adult↗

PubMed1997

Detection of high-grade restenosis after PTCA using contrast-enhanced electron beam CT.

BACKGROUND: Contrast-enhanced electron beam computed tomography (EBCT) has been shown to permit noninvasive visualization of the coronary arteries. We determined the value of EBCT to noninvasively detect high-grade restenosis after percutaneous transluminal coronary angioplasty (PTCA). METHODS AND RESULTS: Fifty patients (37 to 68 years of age), were investigated by EBCT at a mean interval of 9 months after PTCA of coronary artery stenoses. Forty axial cross-sections of the heart (3-mm slice thickness, 1-mm overlap) were acquired triggered to the ECG after intravenous injection of contrast agent. Three-dimensional reconstructions of the coronary arteries were rendered with a lower threshold of 80 HU to selectively visualize the contrast-enhanced vessel lumen. EBCT results were compared with conventional quantitative coronary angiography (QCA) performed within 1 week. In 6 patients, the PTCA segment could not be evaluated because of impaired image quality. Sixteen of the remaining 44 patients had high-grade restenoses in QCA (>70% diameter reduction), which was correctly detected by EBCT in 15 cases (94% sensitivity). There were 5 false-positive EBCT results of high-grade restenosis (82% specificity). CONCLUSIONS: EBCT with intravenous injection of contrast agent permits the noninvasive diagnosis of restenosis after PTCA, with high sensitivity and sufficient specificity.

Adult↗