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A Hartmann

Publications and source records attributed to A Hartmann.

At least 127 records · Page 7Linked to original sources
PubMed2000

16S rDNA analysis for characterization of denitrifying bacteria isolated from three agricultural soils.

Bacteria capable of denitrification are spread among phylogenetically diverse groups. In the present investigation, molecular methods (amplified ribosomal DNA restriction analysis (ARDRA) and partial 16S rDNA gene sequencing) were used to determine the genetic diversity of culturable denitrifying soil bacteria. The purpose of this work was to study the microbial density and diversity of denitrifying communities isolated from two luvisols and a rendosol. The denitrifying bacterial density was significantly higher in the two luvisols (3x10(6) and 4x10(6) bacteria g(-1) dry soil) than in the rendosol (4x10(5) bacteria g(-1) dry soil). Denitrifying isolates from soils were grouped according to the similarity of their restriction patterns into 26 ARDRA types. Interestingly ARDRA analysis suggests that some denitrifying isolates are specific to a soil type while others seem to be geographically widespread. The number of individual isolates found in each ARDRA type appeared to be highly variable between the two sampling dates but some denitrifying types were capable of persisting in soil. The tree obtained from the partial sequences revealed five major branches exhibiting highest identity to the following genera: (i) Burkholderia-Ralstonia, (ii) Pseudomonas, (iii) Xanthomonas-Frateuria, (iv) Bacillus and (v) Streptomyces. Our 16S rDNA-based analysis clearly reveals broad diversity exceeding that previously described in the literature.

Journal Article↗
PubMed2000

Genetic diversity of carbofuran-degrading soil bacteria.

The genetic diversity of 128 carbofuran-degrading bacteria was determined by ARDRA (amplified ribosomal DNA restriction analysis) of 16S rDNA and restriction fragment length polymorphism analysis of the 16S-23S rDNA spacer region (IGS) using five endonucleases. The isolates were distributed in 26 distinct ARDRA groups and 45 IGS types revealing a high level of microbial diversity confirmed by ARDRA clustering and sequencing of 16S rDNA. The occurrence of a methylcarbamate-degrading gene (mcd) was monitored by polymerase chain reaction amplification using specific primers. The mcd gene was detected only in 58 bacteria and there was no clear relationship between the presence of this gene and the phylogenetic position of the strain.

Journal Article↗
PubMed2000

[Liver histology in hepatitis C: correlation with different biochemical and virological parameters].

BACKGROUND AND AIM: According to the German consensus statement, the indication for treatment of HCV-RNA-positive chronic hepatitis C is not derived from histopathology but from elevated aminotransferases. The indication for liver biopsy has been discussed controversely. This study aimed at investigating the correlation between different biochemical and virological parameters and histological scores of inflammation and fibrosis in chronic hepatitis C. PATIENTS AND METHODS: In a retrospective study, data of 126 patients with chronic hepatitis C who had undergone liver biopsy between January 1994 and March 1998 were analyzed. Histology was interpreted according to a defined numerical score of inflammation and fibrosis by a single pathologist. Scores of fibrosis and inflammation were correlated with biochemical and virological parameters. RESULTS: Inflammatory grading showed a moderate but significant correlation with ALT (r = 0.33, p < 0.001), whereas staging of fibrosis did not correlate with ALT (r = 0.15). There was no association between grading or staging and HCV genotype (n = 110) or serum viral load (n = 57). Grading and staging showed a significant association with each other (p < 0.0001). CONCLUSION: Aminotransferases as "surrogate markers" reflect more or less the histological inflammatory activity but do not allow any estimation of the extent of fibrosis. Some patients may have a high inflammatory activity with low aminotransferases or high aminotransferases with low inflammatory activity. Virological parameters such as HCV genotype or viral load do not allow an estimation of histological findings. If prior to treatment of chronic hepatitis C liver biopsy is omitted and the decision for treatment depends solely on the measurement of surrogate markers, considerable misjudgement of the actual status of liver inflammation or fibrosis may result.

Adolescent↗
PubMed2000

A prospective study of the natural course of cytomegalovirus infection and disease in renal allograft recipients.

BACKGROUND: Cytomegalovirus (CMV) infection is the single most frequent infectious complication in renal transplant recipients. Because no CMV-prophylaxis is given and ganciclovir is used only as deferred therapy for CMV disease at our center, we have been able to study the natural course of CMV infections. The aim was to assess risk factors for CMV infection and disease and thus identify subgroups of patients likely to benefit from CMV prophylaxis or preemptive therapy. METHODS: Between October 1994 and July 1997, 477 consecutive renal transplant recipients (397 first transplants and 80 retransplants) were included in the study. The patients were followed prospectively for 3 months with serial measurements of CMV pp65 antigen for monitoring activity of CMV infections. RESULTS: The incidence of CMV infections in first transplants was 68% in D+R- and D+/-R+ serostatus groups, whereas the incidence of CMV disease was higher in D+R- (56%) than in D+/-R+ (20%, P<0.001). No difference in severity of CMV disease in D+R- and D+/-R+ was seen except for an increased incidence of hepatitis in primary infections. One of 14 deaths could be associated with CMV disease in a seropositive recipient. Cox regression analysis showed that rejection (RR 2.5, P<0.01) and serostatus group D+R- (RR 3.9, P<0.001) were significant risk factors for development of CMV disease. The maximum CMV pp65 antigen count had significant correlation to disease only in CMV seropositive recipients, P<0.001. Conclusion. Renal transplant recipients can safely be given deferred ganciclovir therapy for CMV disease if they are intensively monitored for CMV infection. Patients with primary CMV infection (D+R-), CMV infected patients undergoing anti-rejection therapy and R+ patients with high CMV pp65 counts seem to have a particular potential for benefit from preemptive anti-CMV-therapy.

Adolescent↗
PubMed2000

Predictors of resource use after acute hospitalization: the Northern Manhattan Stroke Study.

OBJECTIVE: To determine demographic and clinical predictors of discharge destinations following acute care hospitalization for stroke in the community of northern Manhattan. METHODS: A group of 893 patients (mean age, 70 +/- 12 years; 56% women; 51% Hispanic, 30% African-American, 19% white) who survived acute care hospitalization for a first ischemic stroke were followed prospectively. Stroke severity was assessed by the NIH Stroke Scale and categorized as mild (< or = 5), moderate (6 to 13), and severe (> or = 14). Polytomous logistic regression was used to determine predictors for rehabilitation and nursing home placement versus returning home. RESULTS: Among the survivors of acute stroke care hospitalization, 611 (68%) patients were discharged to their homes, 168 (19%) to rehabilitation, and 114 (13%) to nursing homes. Patients with moderate and severe neurologic deficits had more than a threefold increased risk of being sent to a nursing home and more than an eightfold increased risk of being sent to rehabilitation. Age over 65 and cognitive impairment were associated with placement to a nursing home (age over 65: OR, 2.4; 95% CI, 1.0 to 5.6; cognitive impairment: OR, 2.9; 95%, CI 1.4 to 5.7), and rehabilitation (age over 65: OR, 1.8; 95% CI, 1.1 to 2.9; cognitive impairment: OR, 2.9; 95% CI, 1.4 to 5.7). CONCLUSION: Our results demonstrated that one-third of patients with acute stroke from the community of northern Manhattan required placement in a temporary or a long-term disability care institution following acute care hospitalization. Severity of stroke is an important factor that influences discharge planning following acute care hospitalization and its reduction can improve health care resource usage.

Aged↗
PubMed2000

Few-particle effects in semiconductor quantum dots: observation of multicharged excitons

We investigate experimentally and theoretically few-particle effects in the optical spectra of single quantum dots (QDs). Photodepletion of the QD together with the slow hopping transport of impurity-bound electrons back to the QD are employed to efficiently control the number of electrons present in the QD. By investigating structurally identical QDs, we show that the spectral evolutions observed can be attributed to intrinsic, multi-particle-related effects, as opposed to extrinsic QD-impurity environment-related interactions. From our theoretical calculations we identify the distinct transitions related to excitons and excitons charged with up to five additional electrons, as well as neutral and charged biexcitons.

Journal Article↗
PubMed2000

Caspase-3: A vulnerability factor and final effector in apoptotic death of dopaminergic neurons in Parkinson's disease.

Caspase-3 is an effector of apoptosis in experimental models of Parkinson's disease (PD). However, its potential role in the human pathology remains to be demonstrated. Using caspase-3 immunohistochemistry on the postmortem human brain, we observed a positive correlation between the degree of neuronal loss in dopaminergic (DA) cell groups affected in the mesencephalon of PD patients and the percentage of caspase-3-positive neurons in these cell groups in control subjects and a significant decrease of caspase-3-positive pigmented neurons in the substantia nigra pars compacta of PD patients compared with controls that also could be observed in an animal model of PD. This suggests that neurons expressing caspase-3 are more sensitive to the pathological process than those that do not express the protein. In addition, using an antibody raised against activated caspase-3, the percentage of active caspase-3-positive neurons among DA neurons was significantly higher in PD patients than in controls. Finally, electron microscopy analysis in the human brain and in vitro data suggest that caspase-3 activation precedes and is not a consequence of apoptotic cell death in PD.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

[Cardiac pacemaker therapy for optimizing brain circulation. A possible prevention for cerebrovascular diseases?].

HISTORY AND CLINICAL FINDINGS: A 78-year-old patient experienced dizziness, impairment of mnemic and cognitive function, chronic fatigue and recurrent syncope. INVESTIGATIONS: Hypertensive heart disease, reduced left ventricular function, and ventricular ectopia classification Lown IVb was documented. Computed tomography showed minimal brain atrophia. Stenoses of the brain supplying arteries and of other intracranial diseases were excluded. A distinct correlation between cardiac output and cerebral blood flow in correspondence to changes of heart rate were found (cardiac output 4.2 l/min during sinus rhythm, 7.4 l/min during temporary atrial pacing--AAI-Mode with a pacing rate of 90/min; 4.8 l/min--AAI-Mode with a pacing rate of 120/min; cerebral blood flow: 70, 74 and 62 ml/100 g per minute, respectively). Thus, impairment of cerebral blood flow autoregulation can be assumed. TREATMENT AND COURSE: After implantation of a permanent pacemaker the patient was without any complaints. The mnemic and cognitive function improved, dizziness and fatigue disappeared. Synopsis did not occur. 14 months later a sudden onset of complaints occurred caused by atrial fibrillation (heart rate 120/min). Cardiac output and cerebral blood flow were now 4.0 l/min and 35 ml/100 g per minute. After antiarrhythmic drug therapy and restoration of sinus rhythm cardiac output and cerebral blood flow increased and the complaints disappeared again. CONCLUSION: In patients with impaired capacity of cerebral autoregulation a reduced cardiac function and output can induce a reduction of cerebral blood flow. Thus, impairment of mnemic and cognitive function as well as other unspecific neurological deficits can be caused. In these cases pacemaker therapy has to be discussed as an effective therapeutical concept.

Aged↗
PubMed2000

Interrater agreement for high grade carotid artery stenosis measurement and treatment decision.

OBJECTIVES: Randomized trials in North America (NASCET, ACAS) and Europe (ECST) have shown a beneficial effect of endarterectomy for patients with high grade carotid artery stenosis. The results of the NASCET and the ECST further suggest that the effect of endarterectomy differed by degree of stenosis, supporting the importance of stenosis measurement as a factor in the decision process regarding surgery. We investigated the interrater agreement for carotid artery stenosis measurements and treatment decision in a post hoc study on patients undergoing carotid surgery. METHODS: In a one-year series, 45 consecutive patients underwent preoperative conventional cerebral angiography followed by endarterectomy. Using a magnifying eyepiece and applying the two different measurement criteria of the randomized trials, angiograms were re-evaluated post hoc by three masked raters. Intra-class correlation coefficients (ICCs) with one-sided 95% confidence intervals (CIs) were calculated for the estimation of interrater agreement for degree of stenosis. Conger s kappa (k) statistics were used for the estimation of interrater agreement for a dichotomized stenosis evaluation, i.e. therapeutic decision on surgery (cut-off point for symptomatic stenosis: 70%, cut-off point for asymptomatic stenosis: 60%). RESULTS: ICCs were.74 (CI.63) for NASCET/ACAS criteria and.72 (CI. 59) for ECST criteria. k values were.55 (CI.42) for NASCET/ACAS criteria and.57 (CI.44) for ECST criteria. Disagreement for a therapeutic decision was seen in 6 of 23 symptomatic patients by NASCET criteria, in 2 of 23 symptomatic patients by ECST and in 4 of 22 asymptomatic patients by ACAS criteria. CONCLUSIONS: Overall, the interrater agreement for stenosis measurements was good. Agreement for therapeutic decisions on carotid surgery, however, was less strong. These findings suggest that accurate stenosis measurement may not suffice for reliable treatment decisions in patients with high grade carotid artery stenosis.

Aged↗
PubMed2000

A prospective trial of midwest breast cancer patients: a p53 gene mutation is the most important predictor of adverse outcome.

Several retrospective studies have suggested p53 gene mutation as an adverse prognostic indicator in breast cancer patients, based on a selective growth advantage of p53 mutant cancer cells and their presumed resistance to current adjuvant therapy regimens. A cohort of 90 Caucasian midwestern breast cancer patients was analyzed prospectively (60 months of follow-up) with a rigorous mutation detection methodology. The presence of a p53 gene mutation was the single most adverse prognostic indicator for recurrence (p = 0.0032) and death (p = 0.0001), and was associated with poor response to both adjuvant (p = 0.0001) and palliative (p = 0.006) therapy. Analysis of the p53 gene with appropriate mutation detection methodology markedly improves the prediction of early recurrence, treatment failure, and death in breast cancer patients.

Breast Neoplasms↗
PubMed2000

Effect of atenolol and celiprolol on acetylcholine-induced coronary vasomotion in coronary artery disease.

Earlier studies have reported on the potentiated muscarinic vasoconstriction of intracoronary acetylcholine after metoprolol application in patients with coronary artery disease. The present study investigated the effect of celiprolol, atenolol, and placebo on acetylcholine-induced vasomotion in patients with coronary artery disease. Furthermore, direct effects on coronary vasomotion and on hemodynamics were evaluated. Acetylcholine (intracoronary concentrations of 6.3x10(-7), 2.0x10(-6), and 6.3x10(-6) M) was given before and after double-blind celiprolol (0.30 mg/kg IV), atenolol (0.15 mg/kg IV), or placebo in 3x12 patients. Vasomotion was investigated by quantitative coronary angiography in proximal and distal segments of epicardial coronary arteries, and by the determination of the coronary resistance index based on Doppler-flow measurements. The investigated drugs had no direct affect on the diameter of the epicardial coronary arteries. However, celiprolol, in contrast to atenolol, significantly reduced systemic vascular resistance (change after atenolol: from 1,855+/-308 to 2,161+/-550 dyne s cm(-5); celiprolol: 1,691+/-435 to 1,411+/-343 dyne s cm(-5); and placebo: 1,722+/-215 to 1,710+/-213 dyne s cm(-5), p<0.001) and the coronary resistance index (change after atenolol: 2.52+/-3.58 to 2.86+/-4.24; celiprolol: 2.70+/-1.55 to 2.49+/-2.26; and placebo: 1.97+/-1.35 to 1.92+/-1.25, p<0.01). Celiprolol, atenolol, and placebo did not have different effects on acetylcholine-induced coronary vasomotion of epicardial conductance vessels (diminution of proximal lumen diameter before/after atenolol: 0.42+/-0.39/0.44+/-0.39 mm; celiprolol: 0.32+/-0.26/0.30+/-0.24 mm; and placebo: 0.36+/-0.29/0.43+/-0.40 mm) and of coronary resistance vessels (reduction of coronary resistance index before/after atenolol: 1.95 +/-4.74/ 1.92+/-3.74; celiprolol: 0.98+/-0.73/1.41+/-1.50; and placebo: 1.16+/-1.29/1.16+/-1.04). In contrast to atenolol, celiprolol possesses vasodilative properties in systemic and coronary resistance vessels. There was no direct effect on the diameter of conductance vessels. Acetylcholine-induced coronary vasomotion both in conductance and resistance vessels was not influenced by the beta blockers that were studied. This suggests that atenolol and celiprolol do not influence endothelium-dependent, nitric oxide related vasomotion.

Acetylcholine↗
PubMed2000

Single cell gel/comet assay: guidelines for in vitro and in vivo genetic toxicology testing.

Atthe International Workshop on Genotoxicity Test Procedures (IWGTP) held in Washington, DC, March 25-26, 1999, an expert panel met to develop guidelines for the use of the single-cell gel (SCG)/Comet assay in genetic toxicology. The expert panel reached a consensus that the optimal version of the Comet assay for identifying agents with genotoxic activity was the alkaline (pH > 13) version of the assay developed by Singh et al. [1988]. The pH > 13 version is capable of detecting DNA single-strand breaks (SSB), alkali-labile sites (ALS), DNA-DNA/DNA-protein cross-linking, and SSB associated with incomplete excision repair sites. Relative to other genotoxicity tests, the advantages of the SCG assay include its demonstrated sensitivity for detecting low levels of DNA damage, the requirement for small numbers of cells per sample, its flexibility, its low costs, its ease of application, and the short time needed to complete a study. The expert panel decided that no single version of the alkaline (pH > 13) Comet assay was clearly superior. However, critical technical steps within the assay were discussed and guidelines developed for preparing slides with agarose gels, lysing cells to liberate DNA, exposing the liberated DNA to alkali to produce single-stranded DNA and to express ALS as SSB, electrophoresing the DNA using pH > 13 alkaline conditions, alkali neutralization, DNA staining, comet visualization, and data collection. Based on the current state of knowledge, the expert panel developed guidelines for conducting in vitro or in vivo Comet assays. The goal of the expert panel was to identify minimal standards for obtaining reproducible and reliable Comet data deemed suitable for regulatory submission. The expert panel used the current Organization for Economic Co-operation and Development (OECD) guidelines for in vitro and in vivo genetic toxicological studies as guides during the development of the corresponding in vitro and in vivo SCG assay guidelines. Guideline topics considered included initial considerations, principles of the test method, description of the test method, procedure, results, data analysis and reporting. Special consideration was given by the expert panel to the potential adverse effect of DNA degradation associated with cytotoxicity on the interpretation of Comet assay results. The expert panel also discussed related SCG methodologies that might be useful in the interpretation of positive Comet data. The related methodologies discussed included: (1) the use of different pH conditions during electrophoreses to discriminate between DNA strand breaks and ALS; (2) the use of repair enzymes or antibodies to detect specific classes of DNA damage; (3) the use of a neutral diffusion assay to identify apoptotic/necrotic cells; and (4) the use of the acellular SCG assay to evaluate the ability of a test substance to interact directly with DNA. The alkaline (pH > 13) Comet assay guidelines developed by the expert panel represent a work in progress. Additional information is needed before the assay can be critically evaluated for its utility in genetic toxicology. The information needed includes comprehensive data on the different sources of variability (e.g., cell to cell, gel to gel, run to run, culture to culture, animal to animal, experiment to experiment) intrinsic to the alkaline (pH > 3) SCG assay, the generation of a large database based on in vitro and in vivo testing using these guidelines, and the results of appropriately designed multilaboratory international validation studies.

Animals↗
PubMed2000

Each administration of cyclosporin A enhances skin microvascular reactivity in renal transplant recipients.

Both impaired and enhanced microvascular function have been described in humans on cyclosporin A (CsA) therapy. In the present study we investigated the acute microvascular effects of a single CsA administration in renal transplant recipients on maintenance CsA therapy. Fourteen renal transplant recipients, median age 48 years (range 24-63 years), transplanted 4-12 weeks earlier, were included in this placebo-controlled, double-blinded, crossover study. All recipients had stable renal function; median serum creatinine was 116 micromol/L (range 80-184 micromol/L). Immunosuppressive therapy consisted of CsA, prednisolone, and either azathioprine or mycophenolate. Microvascular function was assessed by laser Doppler flowmetry in combination with acetylcholine (endothelium dependent) stimulation and the postocclusive reactive hyperemia test. Measurements were performed before (control) and 2.5 h following administration of CsA (Neoral) or matching placebo and repeated with reversed medication after at least 6 days. Vasodilative responses to acetylcholine stimulation were significantly higher following CsA ingestion compared with placebo. The mean change in AUC(1.5) (area under the flux versus time curve) from control to 2.5 h was 100 +/-145 for CsA and -292 +/- 140 AU x min for placebo (P = 0.047, n = 10). The postocclusive hyperemic response AUC(rh) was also significantly higher following CsA intake (39 +/- 4 AU x min) compared to placebo (30 +/- 4 AU x min) (P = 0.006, n = 12). This study shows that each dose of CsA induces a transient increase in skin microvascular reactivity in renal transplant recipients. We speculate that this might be due to the potentiation of one or several endothelial-dependent compensatory vasodilative mechanisms in the microvascular bed.

Adult↗
PubMed2000

Detectability and detection rate of acute cerebral hemisphere infarcts on CT and diffusion-weighted MRI.

Our purpose was to compare the detectability and detection rate of acute ischaemic cerebral hemisphere infarcts on CT and diffusion-weighted MRI (DWI). We investigated 32 consecutive patients with acute hemisphere stroke with unenhanced CT and DWI within 6 h of stroke onset. The interval between CT and DWI ranged from 15 to 180 min (mean 60 min). Infarct detectability on CT and DWI was determined by comparing the initial CT, DWI and later reference images in a consensus reading of five independent examiners. The "true" detection rate was assessed by analysing all single readings. Two patients had intracerebral haematomas on DWI and CT and were excluded. There were 27 patients with ischaemic infarcts; all were visible on DWI and proven by follow-up. DWI was negative in three patients without a final diagnosis of infarct (100% sensitivity, 100% specificity, chi2 = 30, P < 0.0001). Ischaemic infarcts were visible on 15 and not seen on 12 CT studies (55 % sensitivity, 100% specificity, chi2 = 1.48, P = 0.224). With regard to the single readings (30 examinations x 5 examiners = 150 readings), 63 CT readings were true positive and 72 false negative (sensitivity 47 %, specificity 86%, chi2 = 2.88, P = 0.089). Of the DWI readings 128 were true positive and 7 false negative (sensitivity 95%, specificity 87 %, chi2 = 70.67, P < 0.0001). Interobserver agreement was substantial for CT (chi = 0.72, 95 % confidence interval, 0.6-0.84) and DWI (chi = 0.82, 95 % confidence interval, 0.46-1). Taken together, detectability and detection rate of acute (< 6 h) hemisphere infarcts are significantly higher with DWI than with CT.

Brain↗
PubMed2000

Prognostic significance of DNA cytometry in thymoma.

PURPOSE: The aim of this work was to evaluate the prognostic significance of DNA image cytometry in thymoma. PATIENTS AND METHODS: Image cytometric studies with an automatic video-based analysis system (LEYTAS) were carried out on 47 archival specimens from 36 patients with thymomas who underwent operation at a single institution from 1954 to 1992. The significance of aneuploidy DNA-content (5c-exceeding events), and nuclear size on stage and survival were evaluated. The median follow-up was 52.7 (6-164) months. RESULTS: Masaoka's stage was predictive of aneuploidy (P < 0.01) and disease-free survival (P < 0.015). In stage I 18% of the tumors were aneuploid, in stage II 78%, in stage III 85% and in stage IV 100%. The occurrence of 5c-exceeding events was associated with both decreased disease-free survival (P < 0.01) and overall survival (P = 0.013). Nuclear size was not significantly correlated to stage. Under multivariate analysis, aneuploidy and DNA content failed to attain independent significance for stage, performance status, and histology. CONCLUSION: DNA image cytometry may provide additional information about the prognosis of resected thymoma.

Adult↗
PubMed2000

Genomic instability induced by high and low LET ionizing radiation.

Genomic instability is the increased rate of acquisition of alterations in the mammalian genome, and includes such diverse biological endpoints as chromosomal destabilization, aneuploidy, micronucleus formation, sister chromatid exchange, gene mutation and amplification, variations in colony size, reduced plating efficiency, and cellular transformation. Because these multiple endpoints persist long after initial radiation exposure, genomic instability has been proposed to operate as a driving force contributing to genetic plasticity and carcinogenic potential. Many of these radiation-induced endpoints depend qualitatively and quantitatively on genetic background, dose and LET. Differences in the frequency and temporal expression of chromosomal instability depend on all three of the foregoing factors. On the other hand, many of these endpoints appear independent of dose and show bystander effects, implicating non-nuclear targets and epigenetic regulatory mechanisms. The present work will survey results concerning the LET dependence of genomic instability and the role of epigenetic mechanisms, with a particular emphasis on the endpoint of chromosomal instability.

Animals↗