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Improving COVID-19 Research of University Hospitals in Germany: Formative Usability Evaluation of the CODEX Feasibility Portal. Appl Clin Inform 2022; 13:400-409. [PMID: 35445386 PMCID: PMC9021003 DOI: 10.1055/s-0042-1744549] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
BACKGROUND Within the German "Network University Medicine," a portal is to be developed to enable researchers to query on novel coronavirus disease 2019 (COVID-19) data from university hospitals for assessing the feasibility of a clinical study. OBJECTIVES The usability of a prototype for federated feasibility queries was evaluated to identify design strengths and weaknesses and derive improvement recommendations for further development. METHODS In the course of a remote usability test with the thinking-aloud method and posttask interviews, 15 clinical researchers evaluated the usability of a prototype of the Feasibility Portal. The identified usability problems were rated according to severity, and improvement recommendations were derived. RESULTS The design of the prototype was rated as simple, intuitive, and as usable with little effort. The usability test reported a total of 26 problems, 8 of these were rated as "critical." Usability problems and revision recommendations focus primarily on improving the visual distinguishability of selected inclusion and exclusion criteria, enabling a flexible approach to criteria linking, and enhancing the free-text search. CONCLUSION Improvement proposals were developed for these user problems which will guide further development and the adaptation of the portal to user needs. This is an important prerequisite for correct and efficient use in everyday clinical work in the future. Results can provide developers of similar systems with a good starting point for interface conceptualizations. The methodological approach/the developed test guideline can serve as a template for similar evaluations.
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Architecture for a feasibility query portal for distributed COVID-19 Fast Healthcare Interoperability Resources (FHIR) patient data repositories: Design and Implementation Study (Preprint). JMIR Med Inform 2022; 10:e36709. [PMID: 35486893 PMCID: PMC9135115 DOI: 10.2196/36709] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/16/2022] [Accepted: 04/11/2022] [Indexed: 12/04/2022] Open
Abstract
Background An essential step in any medical research project after identifying the research question is to determine if there are sufficient patients available for a study and where to find them. Pursuing digital feasibility queries on available patient data registries has proven to be an excellent way of reusing existing real-world data sources. To support multicentric research, these feasibility queries should be designed and implemented to run across multiple sites and securely access local data. Working across hospitals usually involves working with different data formats and vocabularies. Recently, the Fast Healthcare Interoperability Resources (FHIR) standard was developed by Health Level Seven to address this concern and describe patient data in a standardized format. The Medical Informatics Initiative in Germany has committed to this standard and created data integration centers, which convert existing data into the FHIR format at each hospital. This partially solves the interoperability problem; however, a distributed feasibility query platform for the FHIR standard is still missing. Objective This study described the design and implementation of the components involved in creating a cross-hospital feasibility query platform for researchers based on FHIR resources. This effort was part of a large COVID-19 data exchange platform and was designed to be scalable for a broad range of patient data. Methods We analyzed and designed the abstract components necessary for a distributed feasibility query. This included a user interface for creating the query, backend with an ontology and terminology service, middleware for query distribution, and FHIR feasibility query execution service. Results We implemented the components described in the Methods section. The resulting solution was distributed to 33 German university hospitals. The functionality of the comprehensive network infrastructure was demonstrated using a test data set based on the German Corona Consensus Data Set. A performance test using specifically created synthetic data revealed the applicability of our solution to data sets containing millions of FHIR resources. The solution can be easily deployed across hospitals and supports feasibility queries, combining multiple inclusion and exclusion criteria using standard Health Level Seven query languages such as Clinical Quality Language and FHIR Search. Developing a platform based on multiple microservices allowed us to create an extendable platform and support multiple Health Level Seven query languages and middleware components to allow integration with future directions of the Medical Informatics Initiative. Conclusions We designed and implemented a feasibility platform for distributed feasibility queries, which works directly on FHIR-formatted data and distributed it across 33 university hospitals in Germany. We showed that developing a feasibility platform directly on the FHIR standard is feasible.
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Generation of a Fast Healthcare Interoperability Resources (FHIR)-based Ontology for federated Feasibility Queries in the context of COVID-19: An automated approach (Preprint). JMIR Med Inform 2021; 10:e35789. [PMID: 35380548 PMCID: PMC9049646 DOI: 10.2196/35789] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/27/2022] [Accepted: 02/13/2022] [Indexed: 12/02/2022] Open
Abstract
Background The COVID-19 pandemic highlighted the importance of making research data from all German hospitals available to scientists to respond to current and future pandemics promptly. The heterogeneous data originating from proprietary systems at hospitals' sites must be harmonized and accessible. The German Corona Consensus Dataset (GECCO) specifies how data for COVID-19 patients will be standardized in Fast Healthcare Interoperability Resources (FHIR) profiles across German hospitals. However, given the complexity of the FHIR standard, the data harmonization is not sufficient to make the data accessible. A simplified visual representation is needed to reduce the technical burden, while allowing feasibility queries. Objective This study investigates how a search ontology can be automatically generated using FHIR profiles and a terminology server. Furthermore, it describes how this ontology can be used in a user interface (UI) and how a mapping and a terminology tree created together with the ontology can translate user input into FHIR queries. Methods We used the FHIR profiles from the GECCO data set combined with a terminology server to generate an ontology and the required mapping files for the translation. We analyzed the profiles and identified search criteria for the visual representation. In this process, we reduced the complex profiles to code value pairs for improved usability. We enriched our ontology with the necessary information to display it in a UI. We also developed an intermediate query language to transform the queries from the UI to federated FHIR requests. Separation of concerns resulted in discrepancies between the criteria used in the intermediate query format and the target query language. Therefore, a mapping was created to reintroduce all information relevant for creating the query in its target language. Further, we generated a tree representation of the ontology hierarchy, which allows resolving child concepts in the process. Results In the scope of this project, 82 (99%) of 83 elements defined in the GECCO profile were successfully implemented. We verified our solution based on an independently developed test patient. A discrepancy between the test data and the criteria was found in 6 cases due to different versions used to generate the test data and the UI profiles, the support for specific code systems, and the evaluation of postcoordinated Systematized Nomenclature of Medicine (SNOMED) codes. Our results highlight the need for governance mechanisms for version changes, concept mapping between values from different code systems encoding the same concept, and support for different unit dimensions. Conclusions We developed an automatic process to generate ontology and mapping files for FHIR-formatted data. Our tests found that this process works for most of our chosen FHIR profile criteria. The process established here works directly with FHIR profiles and a terminology server, making it extendable to other FHIR profiles and demonstrating that automatic ontology generation on FHIR profiles is feasible.
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The journey to establishing an IT-infrastructure within the German Biobank Alliance. PLoS One 2021; 16:e0257632. [PMID: 34551019 PMCID: PMC8457464 DOI: 10.1371/journal.pone.0257632] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 09/04/2021] [Indexed: 11/19/2022] Open
Abstract
Background Biobanks ensure the long-term storage and accessibility of biospecimens and corresponding data sets. Thus, they form the foundation for many research projects which may contribute to improving medical care. With the establishment of the German Biobank Node and Alliance, expertise in biobanking is bundled and strengthened. An important component within this research infrastructure is the set-up of an information technology (IT) network for allowing feasibility requests across individual biobanks. Objective We aim to describe relevant aspects that have shaped the journey to interconnect biobanks, to enhance their visibility within the research-community, to harmonize data, and to enable feasibility searches to support access to available data and biosamples. Methods To achieve this task, we resorted to a wide variety of methods: we ran a requirement analysis, decided on the mode of operation for the federated team of IT-developers and on the development approach itself, took related national and international initiatives into account, and concluded with evaluations of the developed software artefacts and the operation of the entire chain of applications. Results We drew an IT framework including all heterogeneous data aspects derived from our requirement analysis and developed a comprehensive IT infrastructure. The successful implementation benefited from a smooth interaction of a federated IT team distributed across all participating sites that was even able to manage a major technology change mid-project. Authentication and project management services from associated partners could be integrated and the graphic user interface for an intuitive search tool for biospecimens was designed iteratively. The developed code is open source to ensure sustainability and the local implementation is concluded and functioning. The evaluation of the components was positive. Conclusions The entire project had given ample opportunity for challenges, predictable and unpredictable—from the mode of operation to changing some of the initial ideas. We learned our lessons concerning personnel, budget planning and technical as well as manual monitoring as well as some requirements arising only during the process of the project. Nevertheless, we can here report a success story of a network infrastructure, highly agile and much easier in local installation than initially anticipated.
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APERITIF - Automatic Patient Recruiting for Clinical Trials Based on HL7 FHIR. Stud Health Technol Inform 2021; 281:58-62. [PMID: 34042705 DOI: 10.3233/shti210120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Clinical trials are carried out to prove the safety and effectiveness of new interventions and therapies. As diseases and their causes continue to become more specific, so do inclusion and exclusion criteria for trials. Patient recruitment has always been a challenge, but with medical progress, it becomes increasingly difficult to achieve the necessary number of cases. In Germany, the Medical Informatics Initiative is planning to use the central application and registration office to conduct feasibility analyses at an early stage and thus to identify suitable project partners. This approach aims to technically adapt/integrate the envisioned infrastructure in such a way that it can be used for trial case number estimation for the planning of multicenter clinical trials. We have developed a fully automated solution called APERITIF that can identify the number of eligible patients based on free-text eligibility criteria, taking into account the MII core data set and based on the FHIR standard. The evaluation showed a precision of 62.64 % for inclusion criteria and a precision of 66.45 % for exclusion criteria.
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One Step Away from Technology but One Step Towards Domain Experts-MDRBridge: A Template-Based ISO 11179-Compliant Metadata Processing Pipeline. Methods Inf Med 2019; 58:e72-e79. [PMID: 31853911 DOI: 10.1055/s-0039-3399579] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND Secondary use of routine medical data relies on a shared understanding of given information. This understanding is achieved through metadata and their interconnections, which can be stored in metadata repositories (MDRs). The necessity of an MDR is well understood, but the local work on metadata is a time-consuming and challenging process for domain experts. OBJECTIVE To support the identification, collection, and provision of metadata in a predefined structured manner to foster consolidation. A particular focus is placed on user acceptance. METHODS We propose a software pipeline MDRBridge as a practical intermediary for metadata capture and processing, based on MDRSheet, an ISO 11179-3 compliant template using popular spreadsheet software. It serves as a practical mediator for metadata acquisition and processing in a broader pipeline. Due to the different origins of the metadata, both manual entry and automatic extractions from application systems are supported. To enable the export of collected metadata into external MDRs, a mapping of ISO 11179 to Clinical Data Interchange Standards Consortium (CDISC) Operational Data Model (ODM) was developed. RESULTS MDRSheet is embedded in the processing pipeline MDRBridge and delivers metadata in the CDISC ODM format for further use in MDRs. This approach is used to interactively unify core datasets, import existing standard datasets, and automatically extract all defined data elements from source systems. The involvement of clinical domain experts improved significantly due to minimal changes within their usual work routine. CONCLUSION A high degree of acceptance was achieved by adapting the working methods of clinical domain experts. The designed process is capable of transforming all relevant data elements according to the ISO 11179-3 format. MDRSheet is used as an intermediate format to present the information at a glance and to allow editing or supplementing by domain experts.
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Abstract
Analysis of 36 records of the rarely encountered moray Gymnothorax polyuranodon indicate that juveniles and adults inhabit fresh and mildly brackish habitats (salinity < 5) in streams of the Australian Wet Tropics Eighty-one per cent of these records were from freshwater streams and collectively demonstrate that this species inhabits fresh water throughout all seasons. A survey of fish researchers, each with at least 100 h of field experience in Australia's Wet Tropics, revealed that 33% of researchers working in fresh waters (nine of 27 researchers) had encountered the species and 15% of researchers with substantial experience working in estuaries (two of 13 researchers) had encountered the species. The species was not sampled or observed in the nearshore marine environment. The only record of an elver of this species was, however, found in an estuary at a salinity of 33·4. This preliminary evidence suggests adult G. polyuranodon occupy freshwater habitats, but further research is required to understand the complete life cycle, including movements, habitat use and reproductive ecology of the species.
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Zukunftsperspektiven ambulanter Palliativversorgung in Bielefeld. DAS GESUNDHEITSWESEN 2009. [DOI: 10.1055/s-0029-1215498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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A phase III placebo controlled trial of oral pilocarpine in patients undergoing radiation therapy for head and neck cancer. Int J Radiat Oncol Biol Phys 2001. [DOI: 10.1016/s0360-3016(01)01982-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
It has been suggested that a post-streptococcal autoimmune process may be involved in the pathogenesis of a subgroup of children with tics and obsessive-compulsive symptoms (PANDAS). Elevated antibody titers against streptococcal antigens have also been described in adult patients suffering from Tourette's syndrome (TS). In order to characterise further streptococcal antigens, we focussed on M proteins. M proteins are a major virulence factor of group A streptococci and known to evoke an immunologic cross-reaction with diverse epitopes of human tissue including brain tissue. Therefore, antibodies against M proteins may play a role in the pathophysiology of at least a subgroup of TS patients. Antibodies against M proteins were studied in 25 adult patients suffering from TS and 25 healthy controls after careful medical examination. The antibody titers against the peptides M1, M4, M6, M12 and M19 were estimated by ELISA. Our results show increased titers of antibodies against the streptococcal M12 and M19 proteins in TS patients as compared with controls, while antibody titers against M1, M4 and M6 did not differ between the TS and control groups. Elevated serum titers of antibodies against M12 and M19 proteins support the view that a streptococcus-induced autoimmune process may be involved in TS. The finding of a possible autoimmune origin of TS has implications for both pathophysiology and future therapeutic strategies.
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A phase II study of Biotene in the treatment of postradiation xerostomia in patients with head and neck cancer. Support Care Cancer 2000; 8:203-8. [PMID: 10789961 DOI: 10.1007/s005200050286] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One of the major side effects of radical radiation therapy for head and neck malignancies is xerostomia, or dryness of the mouth. There is no clearly effective treatment for this condition, but we have observed that patients in our practice believe that their symptoms improve significantly when using two "over-the-counter" oral comfort products - Biotene (toothpaste, mouthwash and chewing gum) and Oralbalance gel. We decided to study these agents in a formal phase II study to evaluate their usefulness in patients with postirradiation xerostomia. Twenty-eight patients with post-irradiation xerostomia were entered on the study. All had biopsy-proven carcinoma of the nasopharynx, oropharynx, oral cavity, hypopharynx or larynx, and had received primary radiotherapy with curative intent (> or =50 Gy in 20 fractions) more than 4 months before study entry. More than 75% of both parotid glands were included in the primary radiation field. There was no clinical evidence of recurrent disease. Patients were provided with a 2-month supply of Biotene mouthwash, toothpaste, chewing gum and Oralbalance gel. Response was evaluated 1 and 2 months after study entry using a patient-completed visual analogue scale to assess the severity of xerostomia and its effects on quality of life. For analysis, the scored baseline was subtracted from the later scores to assess change. Patients with an increase of 10 mm from their baseline score on the visual analogue scale were classified as having responded to the treatment intervention, and those with an increase of > or =25 mm from their baseline score were classified as having experienced a major improvement in their symptoms. After 2 months of treatment, 15 patients (54%) reported an improvement in intraoral dryness and 10 of these patients (36%) reported a major improvement. Similar proportions of patients (46% some improvement, 25% major improvement) reported an improvement in their ability to eat normally. Seventeen patients (61%) reported an improvement in oral discomfort, and 12 of these (43%) had a major improvement in their symptoms. The results of this study suggest that the use of Biotene (mouthwash, toothpaste and chewing gum) and Oralbalance gel can improve many of the symptoms of radiation-induced xerostomia. A placebo effect could account for many of the observed improvements in symptoms, and in order to assess the role of these agents in the management of patients with postirradiation xerostomia a randomised phase III study is needed.
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[Self-assessment by patients of impairment caused by obstructive sleep apnea syndrome]. Dtsch Med Wochenschr 2000; 125:348-51. [PMID: 10767871 DOI: 10.1055/s-2007-1024178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
BACKGROUND AND OBJECTIVE The compliance of the nasal continuous positive airway pressure treatment (nCPAP) of the obstructive sleep apnea syndrome (OSAS) depends on the patients' awareness and improvement of the symptoms. Therefore, we studied the relevance of OSAS in different aspects of the quality of life and important aspects of daily life (driving performance, working place). METHODS 352 patients with OSAS filled in a questionnaire of sociodemographic data and impairment of quality of life. The relevance of OSAS was evaluated with polysomnography and parameters of daytime sleepiness. RESULTS The number of women was lower than expected from community related data. The apnea/hypopnea index was 29.9 +/- 23.4/h at baseline measurement and was reduced to 8.8 +/- 9.6/h with nCPAP (p < 0.001). The arousal index (baseline 26.6 +/- 15.3/h) fell with treatment significantly (17.7 +/- 9.2 Arousals/h, p < 0.001). The error rate in the driving simulator test was 7.8 +/- 8.9% (normal value 5.75 +/- 1.4). It was normalised with nCPAP (5.8 +/- 9.5, p < 0.001). 42.3% of patients reported about sleep apnea related symptoms for more than five years before diagnosis. The patients rated their physical fitness on a scale (0 to 6) at 2.9 +/- 1.3. It increased significantly with treatment to 3.4 +/- 1.3 an (p < 0.001). The mental activity improved significantly, too. The daytime sleepiness improved from 3.4 +/- 1.5 to 3.1 +/- 1.5 (p < 0.001). 32.3% of the patients reported that they fell asleep while steering at least once in the last month, 13.0% reported about more than five episodes/month. 5.3% of the patients thought their job in danger because of OSAS. 65.1% felt their performance in job to be impaired. CONCLUSION OSAS impairs patients in different aspects of daily life, especially in the working place. The latency between the onset of symptoms and diagnosis is longer than expected. NCPAP treatment improves the symptoms of OSAS significantly both in criteria of polysomnography and self-assessment of the patients.
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Arousals bei Patienten mit obstruktivem Schlafapnoe-Syndrom Untersuchung zur Haufigkeit in Abhangigkeit von Lebensalter, Geschlecht und Schweregrad der Erkrankung. Frequency of Arousals in Patients With Obstructive Sleep Apnea Syndrome Correlation With Age, Gender, and State of the Disease. SOMNOLOGIE 2000. [DOI: 10.1046/j.1439-054x.2000.00107.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Effect of lindane and phenobarbital on cyclooxygenase-2 expression and prostanoid synthesis by Kupffer cells. Carcinogenesis 1999; 20:1411-6. [PMID: 10426785 DOI: 10.1093/carcin/20.8.1411] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Prostaglandins (PGs) have been implicated in tumor promotion. In this study, we investigated the effect of the hepatic tumor promoters lindane and phenobarbital (PB) on the PG metabolism of Kupffer cells in vitro and in vivo, in particular on the expression of cyclooxygenase (COX), the leading enzyme in prostanoid synthesis. Exposure of primary cultures of Kupffer cells to lindane for 1 h stimulated the production of the PGs PGE(2) and PGD(2) markedly (up to 50-fold) and that of PGF(2alpha) by >3-fold. This effect was accompanied by an increase in the COX-2 protein, as demonstrated by western blotting. Similarly, PB, which shares several effects with lindane in rat liver, also clearly induced COX-2. Lindane and PB affected the PG synthesis in vitro and in vivo in Kupffer cells of rats that had been treated with the two compounds for 56 days. Kupffer cells, which were isolated at days 2, 5 and 56 of the treatment, showed a significant increase in the levels of COX-2 mRNA and protein. Total COX activity was increased approximately 2-fold and 3- to 5-fold in Kupffer cell homogenates of PB- and lindane-treated animals, respectively, compared with the untreated controls. These results suggest that paracrine mechanisms may contribute to the tumor-promoting activity of lindane and PB, stimulating the production of PGs by Kupffer cells.
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Inhibition of transforming growth factor-beta1 and UV light-induced apoptosis by prostanoids in primary cultures of rat hepatocytes. Toxicol Appl Pharmacol 1998; 152:240-50. [PMID: 9772219 DOI: 10.1006/taap.1998.8513] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Treatment of rat hepatocytes cultured in collagen gel with transforming growth factor-beta1 (TGFbeta1) or with UV light strongly increased the frequency of apoptotic nuclei within 24 h; at doses of 0.5 ng/ml TGFbeta1 or 90 J/m2 UV light about 17 and 22% apoptotic nuclei were determined, respectively. DNA of the treated cells showed internucleosomal DNA fragmentation. Already the presence of the cytokine for only 1 h significantly induced apoptosis. The prostanoids PGI2, PGD2, and PGE1 decreased the frequency of apoptotic nuclei in a dose-dependent manner by up to 70 to 80% and suppressed internucleosomal DNA fragmentation. In contrast, PGE2 and PGF2alpha elicited a smaller protective effect and arachidonic acid had none. In the case of PGE1 it was shown that the prostaglandin was most effective when added together with TGFbeta1 or within 2 h before or after treatment with this cytokine. An early increase of the tumor suppressor gene product p53 is thought to play a decisive role in UV light-induced apoptosis. However, this increase in p53 was not affected by the strong cytoprotective prostacyclin PGI2. Our findings show a marked antiapoptotic activity of the prostanoids PGE1, PGI2, and PGD2 and raise the question of whether these prostanoids may influence apoptosis in pathological processes in the liver.
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Abstract
The authors prospectively studied movement patterns of the spinal cord in 46 patients (aged 0.5-16 years) with meningomyelocele but without major neurologic deficits. Three different motion patients were observed. Reduced mobility correlated with a higher risk of developing secondary tethered cord syndrome after a mean observation time of 15 months. This technique may be helpful in identifying patients for early surgery.
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Abstract
Mechanisms of H+ transport across the plasma cell membrane of prophase-arrested oocytes of Xenopus laevis were investigated by testing the effect of ion substitutions and inhibitors on cytoplasmic pH (pHi), membrane potential (Vm) and membrane resistance (Rm). During superfusion with control solution of pH = 7.4, pHi was 7.49 +/- 0.12 (n = 15), Vm was -61.9 +/- 7.8 mV (n = 34) (cytoplasm negative), and Rm was 2.9 +/- 1.5 M omega (n = 19). These data confirm that H+ ions are not distributed at electrochemical equilibrium. By following pHi during recovery of the oocytes from an acid load (20 mmol/l NH4Cl) in the presence and absence of extracellular Na+ or amiloride (1 mmol/l), a Na/H exchanger was identified. On the basis of the known Na+ gradient across the cell membrane, this transporter could suffice to generate the observed H+ disequilibrium distribution. Utilizing blockers or ion-concentration-step experiments no evidence was obtained for an ATP-driven H+ pump or for passive acid/base transporters such as H+ conductances or Na+ (HCO3-)3 cotransport. The membrane depolarization observed in response to extracellular acidification appeared to result from a pH-dependent, Ba(2+)-inhibitable K+ conductance.
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Abstract
cRNA from a PCR-generated C5aR clone was prepared by in vitro transcription and microinjected into Xenopus laevis oocytes. Ligand-induced whole cell current could be detected after co-injection of cRNA for the C5aR with total RNA of the unstimulated U937 cell line, but not with either of the components injected alone. These data clearly demonstrate an absolute requirement of the C5aR for an additional human factor to become functionally expressed in Xenopus oocytes.
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Sodium dependence of the epithelial sodium conductance expressed in Xenopus laevis oocytes. Pflugers Arch 1991; 419:101-7. [PMID: 1658728 DOI: 10.1007/bf00373753] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The epithelial Na+ conductance was expressed in Xenopus laevis oocytes by injection of size-fractionated mRNA of bovine tracheal epithelium. Fractionation was achieved by sucrose density gradient centrifugation. Successful expression was analysed by recording current/voltage (I/V) curves in the presence and absence of amiloride (10 mumol/l). The newly expressed conductance was half-maximally inhibited by 44 nmol/l amiloride and exhibited a selectivity for Na+ over K+ of 140:1. I/V curves obtained at different extracellular Na+ concentrations ([Na+]o) were subjected to a Goldman-fit analysis to obtain the relation between Na+ permeability (PNa) and [Na+]o. The data show that decreasing [Na+]o from 85 mmol/l to 0.85 mmol/l increased PNa by more than threefold, which is thought to reflect Na+ channel inhibition by increasing [Na+]o. This effect clearly exceeded what can be attributed to concentration saturation of single Na+ channel conductance (Palmer and Frindt (1986) Proc Natl Acad Sci USA 83:2767). No correlation of inhibition with intracellular Na+ concentration was observed. Preservation of the [Na+]o-dependent self-inhibition by the newly expressed Na+ conductance suggests that it is an intrinsic property of the Na+ channel protein, probably mediated by an extracellular Na+ binding site.
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Third International Symposium for health professionals in rheumatology. Clin Rheumatol 1990. [DOI: 10.1007/bf02031982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Selective expression of an amiloride-inhibitable Na+ conductance from mRNA of respiratory epithelium in Xenopus laevis oocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1989; 257:L284-8. [PMID: 2552830 DOI: 10.1152/ajplung.1989.257.4.l284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Poly(A)+RNA was prepared from primary cultures of human nasal polyp epithelia and from native bovine tracheal epithelia. Six to fifty nanograms mRNA were injected into prophase-arrested immature Xenopus laevis oocytes. One to four days later the oocytes were probed with electrophysiological techniques for induction of novel ion conductances. Oocytes injected with mRNA had lower membrane potentials (Vm) and resistances (Rm) than controls. By use of step changes in extracellular Na+ concentration and applying amiloride, a Na+ conductance could be identified in mRNA-injected oocytes, which was inhibited by submicromolar concentrations of amiloride with the same kinetics (Ki = 1.3 X 10(-7) mol/l) as in the original tissue. After complete inhibition of this conductance by 10(-5) mol/l amiloride, Vm and Rm approached the respective values of controls. The data indicate that oocytes express functional epithelial Na+ channels but apparently no other epithelial ion conductances from injected mRNA of respiratory epithelium.
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Elevating standards is of critical concern to dental laboratory study clubs. Interview by Carl M. Caplan. DENTAL LABORATORY REVIEW 1983; 58:22-26. [PMID: 6583107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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Health care in China. HEALTH CARE IN CANADA 1979; 21:13, 15. [PMID: 10241336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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Generative Wirkung von O2-freien Kochextrakten aus Krebsgeweben auf anabiotische Hefezellen. Naturwissenschaften 1957. [DOI: 10.1007/bf00629913] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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26
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Antimetabolitische Inaktivierung der anoxygenen Proliferationswirkung von Kochsaft aus tierischen und menschlichen Krebsgeschwülsten in vitro. ACTA ACUST UNITED AC 1957. [DOI: 10.1515/bchm2.1957.308.1.246] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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27
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DNP-Hemmung der anoxygenen Proliferationswirkung von Hefekochsalt auf anabiotische Zellen. Naturwissenschaften 1957. [DOI: 10.1007/bf00597342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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