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Ritter K, Odziemkowski MS, Gillham RW. An in situ study of the role of surface films on granular iron in the permeable iron wall technology. JOURNAL OF CONTAMINANT HYDROLOGY 2002; 55:87-111. [PMID: 12000094 DOI: 10.1016/s0169-7722(01)00187-5] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Permeable walls of granular iron are a new technology developed for the treatment of groundwater contaminated with dissolved chlorinated solvents. Degradation ofthe chlorinated solvents involves a charge transfer process in which they are reductively dechlorinated, and the iron is oxidized. The iron used in the walls is an impure commercial material that is covered with a passive layer of Fe2O3, formed as a result of a high-temperature oxidation process used in the production of iron. Understanding the behaviour of this layer upon contact with solution is important, because Fe2O3 inhibits mechanisms involved in contaminant reduction, including electron transfer and catalytic hydrogenation. Using a glass column specially designed to allow for in situ Raman spectroscopic and open circuit potential measurements, the passive layer of Fe2O3 was observed to be largely removed from the commercial product, Connelly iron, upon contact with Millipore water and with a solution of Millipore water containing 1.5 mg/l trichloroethylene (TCE). It has been previously shown that Fe2O3 is removed from iron surfaces upon contact with solution by an autoreduction reaction; however, prior to this work, the reaction has not been shown to occur on the impure commercial iron products used in permeable granular iron walls. The rate of removal was sufficiently rapid such that the initial presence of Fe2O3 at the iron surface would have no consequence with respect to the performance of an in situ wall. Subsequent to the removal of Fe2O3 layer, magnetite and green rust formed at the iron surface as a result of corrosion in both the Millipore water and the solution containing TCE. The formation of these two species, rather than higher valency iron oxides and oxyhydroxides, is significant for the technology. The former can interfere with contaminant degradation because they inhibit electron transfer and catalytic hydrogenation. Magnetite and green rust, in contrast, will not inhibit the mechanisms involved in contaminant reduction, and hence their formation is beneficial to the long-term performance of the iron material.
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23 |
97 |
2
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Böhle M, Eitel F, Weygandt M, Ritter K. Layer-Wise Relevance Propagation for Explaining Deep Neural Network Decisions in MRI-Based Alzheimer's Disease Classification. Front Aging Neurosci 2019; 11:194. [PMID: 31417397 PMCID: PMC6685087 DOI: 10.3389/fnagi.2019.00194] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 07/15/2019] [Indexed: 12/16/2022] Open
Abstract
Deep neural networks have led to state-of-the-art results in many medical imaging tasks including Alzheimer's disease (AD) detection based on structural magnetic resonance imaging (MRI) data. However, the network decisions are often perceived as being highly non-transparent, making it difficult to apply these algorithms in clinical routine. In this study, we propose using layer-wise relevance propagation (LRP) to visualize convolutional neural network decisions for AD based on MRI data. Similarly to other visualization methods, LRP produces a heatmap in the input space indicating the importance/relevance of each voxel contributing to the final classification outcome. In contrast to susceptibility maps produced by guided backpropagation ("Which change in voxels would change the outcome most?"), the LRP method is able to directly highlight positive contributions to the network classification in the input space. In particular, we show that (1) the LRP method is very specific for individuals ("Why does this person have AD?") with high inter-patient variability, (2) there is very little relevance for AD in healthy controls and (3) areas that exhibit a lot of relevance correlate well with what is known from literature. To quantify the latter, we compute size-corrected metrics of the summed relevance per brain area, e.g., relevance density or relevance gain. Although these metrics produce very individual "fingerprints" of relevance patterns for AD patients, a lot of importance is put on areas in the temporal lobe including the hippocampus. After discussing several limitations such as sensitivity toward the underlying model and computation parameters, we conclude that LRP might have a high potential to assist clinicians in explaining neural network decisions for diagnosing AD (and potentially other diseases) based on structural MRI data.
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research-article |
6 |
92 |
3
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Schaade L, Kockelkorn P, Ritter K, Kleines M. Detection of cytomegalovirus DNA in human specimens by LightCycler PCR. J Clin Microbiol 2000; 38:4006-9. [PMID: 11060060 PMCID: PMC87533 DOI: 10.1128/jcm.38.11.4006-4009.2000] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Detection of human cytomegalovirus (CMV) DNA in clinical specimens is considered a cornerstone in the diagnosis of CMV disease. The aim of this study was to evaluate a newly designed LightCycler-based quantitative CMV PCR. Specimens of human origin (n = 200) were tested using the LightCycler PCR, the quantitative COBAS AMPLICOR CMV MONITOR (CACM) assay, and a qualitative in-house PCR assay for the presence of CMV DNA. Samples that were reactive in at least two of the three assays were considered CMV DNA positive (n = 95 [47. 5%]), while samples that were nonreactive in two of the three assays were considered CMV DNA negative (n = 105 [52.5%]). Using the LightCycler assay, CMV DNA was detected in 91 of the 95 CMV DNA-positive human specimens (sensitivity, 95.8%; 95% confidence interval [CI], 89.6 to 98.8) and in 1 of the CMV DNA-negative specimens (specificity, 99%; 95% CI, 94.8 to 99.8). Results of CMV load determination as assessed by both quantitative test systems were correlated (r = 0.73; P < 0.0001; 95% CI, 0.61 to 0.81). Results for undiluted samples containing a high CMV load were more accurate with the LightCycler test than were results obtained with the CACM test, which underestimated the viral load of samples containing high DNA copy numbers. The high level of sensitivity, specificity, accuracy, and rapidity provided by the LightCycler technology are favorable for the use of this system in the detection of CMV DNA in clinical specimens.
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research-article |
25 |
91 |
4
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Montoya P, Ritter K, Huse E, Larbig W, Braun C, Töpfner S, Lutzenberger W, Grodd W, Flor H, Birbaumer N. The cortical somatotopic map and phantom phenomena in subjects with congenital limb atrophy and traumatic amputees with phantom limb pain. Eur J Neurosci 1998; 10:1095-102. [PMID: 9753177 DOI: 10.1046/j.1460-9568.1998.00122.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The extent of the cortical somatotopic map and its relationship to phantom phenomena was tested in five subjects with congenital absence of an upper limb, four traumatic amputees with phantom limb pain and five healthy controls. Cortical maps of the first and fifth digit of the intact hand, the lower lip and the first toe (bilaterally) were obtained using neuroelectric source imaging. The subjects with congenital upper limb atrophy showed symmetric positions of the left and right side of the lower lip and the first toe, whereas the traumatic amputees with pain showed a significant shift (about 2.4 cm) of the cortical representation of the lower lip towards the hand region contralateral to the amputation side but no shift for the toe representation. In healthy controls, no significant hemispheric differences between the cortical representation of the digits, lower lip or first toe were found. Phantom phenomena were absent in the congenital but extensive in the traumatic amputees. These data confirm the assumption that congenital absence of a limb does not lead to cortical reorganization or phantom limbs whereas traumatic amputations that are accompanied by phantom limb pain show shifts of the cortical areas adjacent to the amputation zone towards the representation of the deafferented body part.
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Clinical Trial |
27 |
80 |
5
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Weygandt M, Mai K, Dommes E, Ritter K, Leupelt V, Spranger J, Haynes JD. Impulse control in the dorsolateral prefrontal cortex counteracts post-diet weight regain in obesity. Neuroimage 2015; 109:318-27. [PMID: 25576647 DOI: 10.1016/j.neuroimage.2014.12.073] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 11/14/2014] [Accepted: 12/29/2014] [Indexed: 11/24/2022] Open
Abstract
A variety of studies suggest that efficient treatments to induce short-term dietary success in obesity exist. However, sustained maintenance of reduced weight is rare as a large proportion of patients start to regain weight when treatment is discontinued. Thus, from a clinical perspective, it would be desirable to identify factors that counteract post-diet weight regain across longer time-scales. To address this question, we extended our previous work on neural impulse control mechanisms of short-term dietary success in obesity and now investigated the mechanisms counteracting long-term weight regain after a diet. Specifically, we measured neural impulse control during a delay discounting task with fMRI at two time points, i.e. the beginning ('T0') and the end ('T12') of a one-year follow-up interval after a 12-week diet. Then, we tested whether activity in the dorsolateral prefrontal cortex (DLPFC) at T0 and whether activity changes across the follow-up period (T0-T12) are linked to success in weight maintenance. The analyses conducted show that control-related DLPFC activity at T0 was coupled to the degree of success in weight maintenance. Consistently, also behavioral measures of control were linked to the degree of success in maintenance. A direct comparison of neural and behavioral control parameters for prognostic weight change modeling revealed that neural signals were more informative. Taken together, neural impulse control in the DLPFC measured with fMRI directly after a diet predicts real-world diet success in obese patients across extended time periods.
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Research Support, Non-U.S. Gov't |
10 |
75 |
6
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Bleich S, Jünemann A, von Ahsen N, Lausen B, Ritter K, Beck G, Naumann GOH, Kornhuber J. Homocysteine and risk of open-angle glaucoma. J Neural Transm (Vienna) 2002; 109:1499-504. [PMID: 12486490 DOI: 10.1007/s007020200097] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Homocysteine levels and the frequency of heterozygous methylenetetrahydrofolate reductase (MTHFR) C677T mutation are increased in open-angle glaucoma. Since homocysteine can induce vascular injury, alterations in extracellular matrix remodelling, and neuronal cell death, these findings may have important implications for understanding glaucomatous optic neuropathy.
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23 |
75 |
7
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Saletu B, Gruber G, Saletu M, Brandstätter N, Hauer C, Prause W, Ritter K, Saletu-Zyhlarz G. Sleep laboratory studies in restless legs syndrome patients as compared with normals and acute effects of ropinirole. 1. Findings on objective and subjective sleep and awakening quality. Neuropsychobiology 2000; 41:181-9. [PMID: 10828727 DOI: 10.1159/000026658] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Although the restless legs syndrome (RLS) is a disorder with a relatively high prevalence rate (8% in Austria) and leads to insomnia and excessive daytime tiredness, there is a paucity of sleep laboratory data concerning objective and subjective sleep and awakening quality. Thus, the aim of this study was to investigate 12 untreated RLS patients as compared with 12 normal controls and subsequently measure the acute effects of 0.5 mg ropinirole (Requip((R))) - a nonergoline dopamine agonist - as compared with placebo. In 3 nights (adaptation, placebo, ropinirole night) sleep induction, maintenance and architecture were measured objectively by polysomnography, subjective sleep and awakening quality were assessed by self-rating scales and visual-analog scales, and objective awakening quality was evaluated by a psychometric test battery. In polysomnography, RLS patients demonstrated, as compared with normal controls, a decreased total sleep time (TST) and sleep efficacy, increased wakefulness during the total sleep period and frequency of nocturnal awakenings, increased sleep stage S1, decreased S2 and increased stage shifts. Subjective sleep quality tended to decrease, and morning well-being, mood, affectivity and wakefulness were deteriorated. In the noopsyche, fine motor activity and reaction time performance were deteriorated. Ropinirole 0.5 mg induced, as compared with placebo, an increase in TST, sleep efficacy, S2 sleep and stage shifts. In the morning, somatic complaints increased slightly, while fine motor activity and reaction time performance improved. Our findings suggest a key-lock principle in the diagnosis/treatment of RLS and a dopaminergic mechanism in its pathogenesis, which is supported by the data on periodic leg movements during sleep and arousals of the subsequent paper.
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Clinical Trial |
25 |
68 |
8
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Eitel F, Soehler E, Bellmann-Strobl J, Brandt AU, Ruprecht K, Giess RM, Kuchling J, Asseyer S, Weygandt M, Haynes JD, Scheel M, Paul F, Ritter K. Uncovering convolutional neural network decisions for diagnosing multiple sclerosis on conventional MRI using layer-wise relevance propagation. Neuroimage Clin 2019; 24:102003. [PMID: 31634822 PMCID: PMC6807560 DOI: 10.1016/j.nicl.2019.102003] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 08/29/2019] [Accepted: 09/04/2019] [Indexed: 12/21/2022]
Abstract
Machine learning-based imaging diagnostics has recently reached or even surpassed the level of clinical experts in several clinical domains. However, classification decisions of a trained machine learning system are typically non-transparent, a major hindrance for clinical integration, error tracking or knowledge discovery. In this study, we present a transparent deep learning framework relying on 3D convolutional neural networks (CNNs) and layer-wise relevance propagation (LRP) for diagnosing multiple sclerosis (MS), the most widespread autoimmune neuroinflammatory disease. MS is commonly diagnosed utilizing a combination of clinical presentation and conventional magnetic resonance imaging (MRI), specifically the occurrence and presentation of white matter lesions in T2-weighted images. We hypothesized that using LRP in a naive predictive model would enable us to uncover relevant image features that a trained CNN uses for decision-making. Since imaging markers in MS are well-established this would enable us to validate the respective CNN model. First, we pre-trained a CNN on MRI data from the Alzheimer's Disease Neuroimaging Initiative (n = 921), afterwards specializing the CNN to discriminate between MS patients (n = 76) and healthy controls (n = 71). Using LRP, we then produced a heatmap for each subject in the holdout set depicting the voxel-wise relevance for a particular classification decision. The resulting CNN model resulted in a balanced accuracy of 87.04% and an area under the curve of 96.08% in a receiver operating characteristic curve. The subsequent LRP visualization revealed that the CNN model focuses indeed on individual lesions, but also incorporates additional information such as lesion location, non-lesional white matter or gray matter areas such as the thalamus, which are established conventional and advanced MRI markers in MS. We conclude that LRP and the proposed framework have the capability to make diagnostic decisions of CNN models transparent, which could serve to justify classification decisions for clinical review, verify diagnosis-relevant features and potentially gather new disease knowledge.
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research-article |
6 |
65 |
9
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Stompe T, Ortwein-Swoboda G, Ritter K, Schanda H, Friedmann A. Are we witnessing the disappearance of catatonic schizophrenia? Compr Psychiatry 2002; 43:167-74. [PMID: 11994832 DOI: 10.1053/comp.2002.32352] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The decrease in the frequency of diagnosed catatonic subtypes among schizophrenic disorders as a whole during the last 50 years has long been regarded as an established fact. Until now the factors responsible for this development have been under discussion. As it is not clear if there is a true decrease or an ostensible one due to other factors such as changed diagnostic habits or neuroleptic treatment, we examined 174 consecutively admitted schizophrenic patients from three different psychiatric institutions diagnosed according to DSM-IV and Leonhard's criteria. It turned out that-depending on the diagnostic system-the rates of diagnosed catatonias were 10.3% (DSM-IV) and 25.3% (Leonhard's criteria). Comparison of the two original Leonhard cohorts (1938 to 1968, 1969 to 1986) with our own (1994 to 1999) shows a decrease in the frequency of catatonias from 35% to 25%, which-albeit statistically significant-is much less pronounced than in studies that used a narrower definition of catatonia. Here, besides sociocultural developments, the use of neuroleptics seems to effect the decrease in the frequency of catatonias in two ways: on one hand, they cause a decrease of hyperkinesia, excitement, or impulsivity; while on the other hand, they themselves produce motor abnormalities like rigidity, effects that favor the attribution of motoric symptoms to neuroleptics.
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Review |
23 |
57 |
10
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Stompe T, Ortwein-Swoboda G, Ritter K, Schanda H. Old wine in new bottles? Stability and plasticity of the contents of schizophrenic delusions. Psychopathology 2003; 36:6-12. [PMID: 12679586 DOI: 10.1159/000069658] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A number of recent case reports published during the last 20 years described a quick inclusion of new technologies and cultural innovations into schizophrenic delusions which led many of the authors to the conclusion that the 'Zeitgeist' is creating new delusional contents. On the other hand, long-term comparisons and comparative transcultural studies on delusions showed, despite a certain degree of variability, a stability of delusional themes over longer periods of time. Combining anthropological and historical theories of the development of societies with a differentiated psychopathological approach (Klosterkötter's three-stage model of the formation of schizophrenic delusions), we were able to resolve the problem of the ostensibly divergent results: there are only a few themes of extraordinary anthropological importance for the organization of human relationships which can be found in every epoch and in different cultures (persecution, grandiosity, guilt, religion, hypochondria, jealousy, and love). With the exception of persecution and grandiosity, these themes showed a certain variability over time and between cultures. The 'new' themes, referring to the development of modern technology and the rapid changes of 'cultural patterns' turned out to be only the shaping of the basic delusional themes on the 3rd stage of Klosterkötter's phase model (concretization).
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Case Reports |
22 |
50 |
11
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Ritter K, Odziemkowski MS, Simpgraga R, Gillham RW, Irish DE. An in situ study of the effect of nitrate on the reduction of trichloroethylene by granular iron. JOURNAL OF CONTAMINANT HYDROLOGY 2003; 65:121-36. [PMID: 12855204 DOI: 10.1016/s0169-7722(02)00234-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The effect of nitrate on the reduction of TCE by commercial granular iron was investigated in column experiments designed to allow for the in situ monitoring of the iron surface film with Raman spectroscopy. Three column experiments were conducted; one with an influent solution of 100 mg/l nitrate+1.5 mg/l TCE, and two control columns, one saturated directly with 100 mg/l nitrate solution, the other pre-treated with Millipore water prior to the introduction of a 100 mg/l nitrate solution. In the presence of nitrate, TCE adsorbed onto the iron, but there was little TCE reduction to end-products ethene and ethane. The iron used (Connelly, GPM, Chicago) is a product typical of those used in permeable granular iron walls. The material is covered by an air-formed high-temperature oxidation film, consisting of an inner layer of Fe(3)O(4), and an outer, passive layer of Fe(2)O(3). In the control column pre-treated with Millipore water, the passive Fe(2)O(3) layer was removed upon contact with the water in a manner consistent with an autoreduction reaction. In the TCE+nitrate column and the direct nitrate saturation column, nitrate interfered with the removal of the passive layer and maintained conditions such that high valency protective corrosion species, including Fe(2)O(3) and FeOOH, were stable at the iron surface. The lack of TCE reduction is explained by the presence of these species, as they inhibit both mechanisms proposed for TCE reduction by iron, including catalytic hydrogenation, and direct electron transfer.
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22 |
49 |
12
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Ebersbach U, Schwabe K, Ritter K. On the kinetics of the anodic passivation of iron, cobalt and nickel. Electrochim Acta 1967. [DOI: 10.1016/0013-4686(67)80093-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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58 |
48 |
13
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Ritter K. A method for solving maximum-problems with a nonconcave quadratic objective function. ACTA ACUST UNITED AC 1966. [DOI: 10.1007/bf00539118] [Citation(s) in RCA: 48] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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59 |
48 |
14
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Stürmer R, Ritter K, Hoffmann RW. A Short, Linear Synthesis of (9S)-Dihydroerythronolide A. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/anie.199301011] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22 |
45 |
15
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Ritter K, Schumacher J, Weygandt M, Buchert R, Allefeld C, Haynes JD. Multimodal prediction of conversion to Alzheimer's disease based on incomplete biomarkers. ALZHEIMER'S & DEMENTIA: DIAGNOSIS, ASSESSMENT & DISEASE MONITORING 2015; 1:206-15. [PMID: 27239505 PMCID: PMC4877756 DOI: 10.1016/j.dadm.2015.01.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Background This study investigates the prediction of mild cognitive impairment-to-Alzheimer's disease (MCI-to-AD) conversion based on extensive multimodal data with varying degrees of missing values. Methods Based on Alzheimer's Disease Neuroimaging Initiative data from MCI-patients including all available modalities, we predicted the conversion to AD within 3 years. Different ways of replacing missing data in combination with different classification algorithms are compared. The performance was evaluated on features prioritized by experts and automatically selected features. Results The conversion to AD could be predicted with a maximal accuracy of 73% using support vector machines and features chosen by experts. Among data modalities, neuropsychological, magnetic resonance imaging, and positron emission tomography data were most informative. The best single feature was the functional activities questionnaire. Conclusion Extensive multimodal and incomplete data can be adequately handled by a combination of missing data substitution, feature selection, and classification.
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Journal Article |
10 |
44 |
16
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Scheithauer S, Manemann AK, Krüger S, Häusler M, Krüttgen A, Lemmen SW, Ritter K, Kleines M. Impact of herpes simplex virus detection in respiratory specimens of patients with suspected viral pneumonia. Infection 2010; 38:401-5. [PMID: 20589523 PMCID: PMC7101829 DOI: 10.1007/s15010-010-0036-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Accepted: 06/09/2010] [Indexed: 11/26/2022]
Abstract
BACKGROUND Respiratory infection and failure is a commonly encountered problem in intensive care unit (ICU) patients. However, despite the accumulating body of evidence to suggest that herpes simplex virus type 1 (HSV-1) is associated with pneumonia, the exact role played by this virus in this process is still not fully understood. Therefore, to identify patients at risk, we have conducted a case-control study to characterize patients with HSV-1-positive pneumonia. PATIENTS AND METHODS Between 2007 and 2009, all patients with suspected viral pneumonia were tested for the presence of herpes viruses using a PCR assay approach with respiratory specimens. To identify possible associations, risk factors, and impact of HSV, HSV-1-positive ICU patients (n = 51) were compared to age-, gender-, and department- and season-matched HSV-negative patients (n = 52). RESULTS HSV-positive patients differed significantly from the HSV-negative ones only in terms of time of mechanical ventilation (13 vs. 6 days, respectively; p = 0.002). Subgroup analysis in the patients aged >60 years and in those without bacterial detection revealed a similar trend (p = 0.01 and p = 0.004, respectively). Mortality did not differ between the groups or between the HSV-1-positive patients treated with aciclovir and those who were not. A viral load >10E+05 geq/ml was associated with mechanical ventilation (20/21 vs. 17/29; p = 0.004), acute respiratory distress syndrome (ARDS; 19/21 vs. 18/29; p = 0.005), sepsis (18/21 vs. 14/29; p = 0.008), detection of a bacterial pathogen in the same specimen (10/21 vs. 4/29; p = 0.01) and longer ICU stay (25 vs. 30 days; p = 0.04). CONCLUSION Despite several associations with high viral load, the clinical outcome of HSV-1-positive ICU patients did not differ significantly from the clinical outcome of HSV-negative patients. This finding indicates that HSV-1 viral loads in respiratory specimens are a symptom of a clinically poor condition rather than a cause of it. Longitudinal and therapy studies are therefore needed to distinguish between HSV-1 as a causative pathogen and HSV-1 as a bystander of pneumonia/ARDS.
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Journal Article |
15 |
40 |
17
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Ritter K, Kuhlencord A, Thomssen R, Bommer W. Prolonged haemolytic anaemia in malaria and autoantibodies against triosephosphate isomerase. Lancet 1993; 342:1333-4. [PMID: 7901638 DOI: 10.1016/0140-6736(93)92248-r] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Prolonged haemolysis may accompany infection with Plasmodium falciparum. We observed prolonged haemolysis in 4 of 10 patients with this type of malaria after parasitological cure. IgM antibodies specific for the glycolytic enzyme triosephosphate isomerase were detected in these patients' sera. Clinical recovery and a decrease in haemolysis coincided with a fall in these autoantibodies. In vitro, affinity purified autoantibodies isolated from the sera directed against triosephosphate isomerase induced lysis of erythrocytes and activation of complement as shown by the 51Cr release assay. We assume that autoantibodies against triosephosphate isomerase contribute to the development of prolonged haemolysis and anaemia in P falciparum malaria.
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32 |
36 |
18
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Ritter K. Affinity purification of antibodies from sera using polyvinylidenedifluoride (PVDF) membranes as coupling matrices for antigens presented by autoantibodies to triosephosphate isomerase. J Immunol Methods 1991; 137:209-15. [PMID: 1849541 DOI: 10.1016/0022-1759(91)90026-c] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Polyvinylidenedifluoride (PVDF) membranes covered with antigen can be used for affinity purification of antibodies from sera. These antibodies serve as an appropriate substitute for monoclonal antibodies when performing cytological and analytical experiments with the respective antigen. The usefulness of this method is demonstrated with the purification of IgM autoantibodies produced against human triosephosphate isomerase in acute Epstein-Barr virus infection. Compared with the original serum, the specific activity of the purified antibodies was up to 1400-fold higher, and the recovery of the anti-triosephosphate isomerase activity between 25 and 33%.
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Abstract
It was the purpose of the study to obtain viewpoints on the genetics of febrile convulsions and their relationship to epilepsy by EEG long term follow up. 89 children with febrile convulsions could be followed up to the age of 11 to 13 years (in total 1046 EEG records). The study was concentrated on genetically determined EEG patterns: bilaterally synchronous spikes and waves, photosensitivity and 4-7 cps rhythms. The statistical evaluation was based on standards derived from known strict age dependence of the different patterns. Theta rhythms were found in 54%, spikes and waves of the resting record in 49% and photosensitivity in 42%. In total, genetically determined EEG patterns were found in 81% of the cases which were sufficiently investigated according to given standards. Spikes and waves are strongly age dependent with a maximum at the age of 5-6 years and appear very inconstantly. Theta rhythms and spikes and waves are closely correlated. Spikes and waves are a heterogeneous phenomenon. The type described here must be interpreted as a facultative symptom of the same functional anomaly which forms the basis of 4-7 cps rhythms. The possible pathophysiological basis of the pattern is discussed.--Photosensitivity is interpreted as the symptom of a genetically independent pathogenetic mechanism, which can lead to additive effects by interaction with other genetic abnormalities as well as exogenous factors.--The pathogenesis of febrile convulsions is multifactorial in the strict sense. While the exogenous pathogenetic factors are rather uniform, the genetic predisposition apparently is not. It is based on different genetic anomalies. Each of them is polygenically determined. In the individual case one or different factors can be involved. The genetic predisposition to febrile convulsions is definitely not only polygenic, but of heterogeneous nature. Finally the genetic relationship between febrile convulsions and epilepsy is discussed.
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Frottier P, Frühwald S, Ritter K, Eher R, Schwärzler J, Bauer P. Jailhouse Blues revisited. Soc Psychiatry Psychiatr Epidemiol 2002; 37:68-73. [PMID: 11931090 DOI: 10.1007/s127-002-8217-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Over the past decades a number of studies have appeared on suicide among persons in jail and prison remand settings, and sentenced prisoners. In these papers contradictory views concerning the relation between suicide risk and length of custody were published. METHODS This article reports on a study that investigated all suicides (n=206) in all 29 Austrian jails and prisons between 1975 and 1996. The authors demonstrate the necessity to calculate the hazard that reflects the suicide risk in relation to time. RESULTS The results suggest three different periods of high suicide risk: immediately after admission and 2 months thereafter for prisoners on remand; for long-term prisoners the suicide risk correlates with the length of the sentence and slightly increases with the time of custody. CONCLUSIONS With this knowledge, suicide prevention programmes in prisons and jails could be made more effective and economic.
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Voss G, Nick S, Stahl-Hennig C, Ritter K, Hunsmann G. Generation of macaque B lymphoblastoid cell lines with simian Epstein-Barr-like viruses: transformation procedure, characterization of the cell lines and occurrence of simian foamy virus. J Virol Methods 1992; 39:185-95. [PMID: 1331148 DOI: 10.1016/0166-0934(92)90137-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Two simian Epstein-Barr-like viruses, a rhesus Epstein-Barr virus and Herpesvirus papio, were used to transform B cells from rhesus or cynomolgus macaques. The resulting cell lines exhibited predominantly a B lymphocyte phenotype and expressed Epstein-Barr virus antigens. The majority of B lymphoblastoid cell lines from macaques, which were seropositive for simian foamy virus, developed giant cells in culture. The cytopathic agent was identified as a foamy virus and was transmissible to human embryonal fibroblasts. Treatment of cell cultures with AZT abolished giant cell formation.
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Kreuzer J, Denger S, Jahn L, Bader J, Ritter K, von Hodenberg E, Kübler W. LDL stimulates chemotaxis of human monocytes through a cyclooxygenase-dependent pathway. Arterioscler Thromb Vasc Biol 1996; 16:1481-7. [PMID: 8977452 DOI: 10.1161/01.atv.16.12.1481] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Monocyte migration into the vessel wall is an early step in atherogenesis. Even though a number of chemotactic factors have been identified, the regulation of the chemotactic response is not clearly understood. As the release of arachidonic acid has been implicated in monocyte chemotaxis, we studied the influence of LDL, which can supply this fatty acid to cells, on the chemotactic mobility of monocytes. Migration of human monocytic U937 cells was abolished by a 30-hour incubation in medium containing lipoprotein-depleted 10% fetal calf serum. Thereafter, human VLDL, LDL, acetyl LDL, methyl LDL, HDL, free cholesterol, linoleic acid, oleic acid, or arachidonic acid was added. At the end of varying incubation periods (0.5 to 8 hours), chemotaxis, viability, and cellular cholesterol content were measured. In the same experimental setting we also studied the effects of the pharmacological agents chloroquine, indomethacin, and acetylsalicylic acid on LDL-mediated chemotaxis. Chemotaxis was restored by LDL in a dose- and time-dependent manner starting at concentrations as low as 5 micrograms/mL and at incubations as brief as 30 minutes. The other lipoproteins tested (VLDL, HDL, acetyl LDL, and methyl LDL) as well as free cholesterol had no comparable effect on chemotaxis. Viability and total cholesterol content did not differ among the groups. Simultaneous incubation of cells with chloroquine, indomethacin, and acetylsalicylic acid reduced restitution of chemotaxis by LDL by 71%, 82%, and 68%, respectively. In contrast, the agents had only slight inhibitory effects on the chemotactic mobility of serum-fed control cells. Incubation with linoleic acid showed a 60% restoration of chemotaxis, whereas arachidonic acid stimulated chemotaxis by 140% compared with the positive control. Preincubation of LDL with the monoclonal antibody MB47 directed against LDL resulted in a significantly reduced migratory response. The data suggest a novel cyclooxygenase-dependent regulatory mechanism of chemotaxis by LDL.
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Geurs F, Ritter K, Mast A, Van Maele V. Successful plasmapheresis in corticosteroid-resistant hemolysis in infectious mononucleosis: role of autoantibodies against triosephosphate isomerase. Acta Haematol 1992; 88:142-6. [PMID: 1466197 DOI: 10.1159/000204671] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A 19-year-old girl fell ill with a high temperature and cervical lymphadenopathy. The detection of heterophile antibodies as well as Epstein-Barr-virus-specific antibodies confirmed the diagnosis of infectious mononucleosis. In the course of the infection, the patient developed severe hemolytic anemia with her hemoglobin falling from 14 to 8 g/dl. High-dose corticosteroid therapy did not stop hemolysis; this could only be achieved by seven plasmapheresis sessions. Antibodies against triosephosphate isomerase (TPI) and the blood group marker 'i' were found in the patient's serum. Anti-i cold agglutinins were not active at 37 degrees C, whereas antibodies against TPI caused increased 51Cr release from marked patient's erythrocytes in vitro. Plasmapheresis removed the autoantibodies effectively and stopped the hemolysis. After 8 weeks, the patient gradually recovered.
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Stürmer R, Ritter K, Hoffmann RW. Eine Kurze, lineare Synthese von (9S)-Dihydroerythronolid A. Angew Chem Int Ed Engl 1993. [DOI: 10.1002/ange.19931050129] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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