Search PubMed⌕ Search

Biomedical subjects

Lars Peter Nielsen

Publications and source records attributed to Lars Peter Nielsen.

13 recordsLinked to original sources
PubMed2006

Nitrogen transformations in stratified aquatic microbial ecosystems.

New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a microm-mm scale. A large and ever-expanding knowledge base about nitrogen fixation, nitrification, denitrification, and dissimilatory reduction of nitrate to ammonium, and about the microorganisms performing the processes, has been produced by use of these techniques. During the last decade the discovery of anammmox bacteria and migrating, nitrate accumulating bacteria performing dissimilatory reduction of nitrate to ammonium have given new dimensions to the understanding of nitrogen cycling in nature, and the occurrence of these organisms and processes in stratified microbial communities will be described in detail.

Aerobiosis↗
PubMed2006

Evidence for complete denitrification in a benthic foraminifer.

Benthic foraminifera are unicellular eukaryotes found abundantly in many types of marine sediments. Many species survive and possibly reproduce in anoxic habitats, but sustainable anaerobic metabolism has not been previously described. Here we demonstrate that the foraminifer Globobulimina pseudospinescens accumulates intracellular nitrate stores and that these can be respired to dinitrogen gas. The amounts of nitrate detected are estimated to be sufficient to support respiration for over a month. In a Swedish fjord sediment where G. pseudospinescens is the dominant foraminifer, the intracellular nitrate pool in this species accounted for 20% of the large, cell-bound, nitrate pool present in an oxygen-free zone. Similarly high nitrate concentrations were also detected in foraminifera Nonionella cf. stella and a Stainforthia species, the two dominant benthic taxa occurring within the oxygen minimum zone of the continental shelf off Chile. Given the high abundance of foraminifera in anoxic marine environments, these new findings suggest that foraminifera may play an important role in global nitrogen cycling and indicate that our understanding of the complexity of the marine nitrogen cycle is far from complete.

Anaerobiosis↗
PubMed2006

[Medication errors on hospital admission].

INTRODUCTION: This study investigated the number of medication errors on hospital admission and the clinical relevance of these errors. The new personal electronic medicine profile (PEM) was tested to establish whether it can contribute further information about the patient's medication on admission. MATERIALS AND METHODS: This cross-sectional study included patients admitted to an acute medical admissions ward. In addition to the ward's usual admission procedure, a clinical pharmacist created an extra medication history by carrying out semi-structured interviews and obtaining additional information from the patient's GP. Information was then obtained from the PEM. A clinical expert panel assessed the potential clinical relevance of the discrepancies. RESULTS: Of 67 patients admitted, 48 were interviewed. The patients' average age was 71, and they used an average of 6.4 medications each. There were 309 prescriptions registered, producing 85 errors: the extra medication history highlighted 73 of these errors, and the subsequent check of the PEM revealed a further 12 errors. Thirty-three patients (69%) were affected by one or more errors, of which the expert panel considered six (18%) to be potentially serious. CONCLUSION: Medication errors on admission to hospital reduce the quality of treatment and can lead to adverse events. The PEM cannot replace the traditional medication history, but the use of a PEM and the increased focus on medication histories can contribute to an improved hospital stay.

Adult↗
PubMed2006

Methods for measuring denitrification: diverse approaches to a difficult problem.

Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO3-) and nitrite (NO2-), to the gases nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2), is important to primary production, water quality, and the chemistry and physics of the atmosphere at ecosystem, landscape, regional, and global scales. Unfortunately, this process is very difficult to measure, and existing methods are problematic for different reasons in different places at different times. In this paper, we review the major approaches that have been taken to measure denitrification in terrestrial and aquatic environments and discuss the strengths, weaknesses, and future prospects for the different methods. Methodological approaches covered include (1) acetylene-based methods, (2) 15N tracers, (3) direct N2 quantification, (4) N2:Ar ratio quantification, (5) mass balance approaches, (6) stoichiometric approaches, (7) methods based on stable isotopes, (8) in situ gradients with atmospheric environmental tracers, and (9) molecular approaches. Our review makes it clear that the prospects for improved quantification of denitrification vary greatly in different environments and at different scales. While current methodology allows for the production of accurate estimates of denitrification at scales relevant to water and air quality and ecosystem fertility questions in some systems (e.g., aquatic sediments, well-defined aquifers), methodology for other systems, especially upland terrestrial areas, still needs development. Comparison of mass balance and stoichiometric approaches that constrain estimates of denitrification at large scales with point measurements (made using multiple methods), in multiple systems, is likely to propel more improvement in denitrification methods over the next few years.

Acetylene↗
PubMed2005

Lysis with Saponin improves detection of the response through CD203c and CD63 in the basophil activation test after crosslinking of the high affinity IgE receptor FcepsilonRI.

BACKGROUND: The basophil activation test (BAT), in which translocation of markers to the surface of blood basophils is measured in response to allergen by flow cytometry, is a rapid assay that is gaining popularity. Two markers are currently being evaluated for the BAT; CD63 and the lineage-specific CD203c. In a recent report, detection of CD203c after lysis with Saponin was shown to be superior to detection of CD63 after lysis with formic acid. We wanted to compare a) lysis with formic acid and lysis with Saponin, b) the response through CD203c and CD63, and c) the definition 10% activated cells above background with the probability binning metric T(chi) > 4, on sets of data generated with blood basophils stimulated with varying concentrations of anti-FcepsilonRI antibody. METHODS: Blood from volunteers was incubated with serial logarithmic dilutions of anti-FcepsilonRI and subsequently with antibodies to CD203c PE and CD63 FITC. Sets of samples set up in parallel were lysed with either Saponin based Whole Blood Lysing reagent or with formic acid based Immunoprep/Q-prep. Samples were acquired on a FACS Calibur, but were compensated and analysed offline. Responders were defined as persons who had 10% or more activated basophils above background, or a T(chi) > 4, for two consecutive dilutions of anti-FcepsilonRI antibody. RESULTS: More basophils (median 1164 vs. median 397) and better discrimination of upregulated CD203c and CD63 amongst responders were obtained after lysis with Saponin than after lysis with formic acid. We suggest that CD203c may be a more sensitive marker for the BAT than CD63, as 6/11 responders were found with CD203c, compared with 3/11 with CD63. Most responders (7/11) were identified with probability binning. CONCLUSION: A combination of lysis with Saponin and the markers CD203c and CD63 computed by probability binning may be the most sensitive method of detecting activation of basophils after stimulation through FcepsilonRI.

Journal Article↗
PubMed2005

Kinetics, diffusional limitation and microscale distribution of chemistry and organisms in a CANON reactor.

In the Completely Autotrophic Nitrogen removal Over Nitrite (CANON) process, aerobic and anaerobic ammonia oxidizing bacteria cooperate to remove ammonia in one oxygen-limited reactor. Kinetic studies, microsensor analysis, and fluorescence in situ hybridization on CANON biomass showed a partial differentiation of processes and organisms within and among aggregates. Under normal oxygen-limited conditions ( approximately 5 microM O2), aerobic ammonia oxidation (nitrification) was restricted to an outer shell (<100 microm) while anaerobic ammonia oxidation (anammox) was found in the central anoxic parts. Larger type aggregates (>500 microm) accounted for 68% of the anammox potential whereas 65% of the nitrification potential was found in the smaller aggregates (<500 microm). Analysis with O2 and NO2- microsensors showed that the thickness of the activity zones varied as a function of bulk O2 and NO2- concentrations and flow rate.

Aerobiosis↗
PubMed2005

Few but severe viral infections in children with cancer: a prospective RT-PCR and PCR-based 12-month study.

BACKGROUND: Treatment of low-risk febrile episodes with oral administered antibiotics at home is a new approach in pediatric oncology and protective isolation is loosened in more centers. The impact of viral respiratory infections in febrile diseases in this population is still unclear in terms of occurrence and morbidity. PROCEDURE: A prospective follow-up study of all febrile episodes during 12 months in a pediatric oncology department with a high level of protective isolation was set-up with expanded molecular viral examinations. Reverse transcriptase polymerase chain reaction (RT-PCR) and PCR diagnostics of ten viruses, two atypical bacteria, and one fungus were performed and clinical information on all infections was registered. RESULTS: A total of 250 febrile episodes in 66 patients were registered. In all, 198 respiratory secretions, predominantly oral washes, and 165 anal swabs were analyzed. Twenty-two infections were diagnosed: 7 rhinovirus infections, 4 respiratory syncytial virus (RSV) infections, 2 herpes simplex virus (HSV) infections, 2 varicella-zoster-virus (VZV) infections, 1 influenza B virus infection, 1 parainfluenza virus type 3 infection (PIV3), 1 human metapneumovirus (HMPV) infection, 1 enterovirus infection, 0 adenovirus infections, 0 influenza A virus infections, and 3 non-viral pneumonias: 1 M. Pneumonia, 1 C. Pneumonia, and 1 P. Carinii. The detected pathogens correlated well to the clinical disease. Patients with viral infections were as affected as patients with bacteria in the blood. One of 19 viral infections was lethal, a RSV pneumonia. C-reactive protein concentrations were not able to distinguish viral infections from bacteremias. CONCLUSIONS: The applied sampling method was acceptable and molecular diagnosis of viruses, atypical bacteria and P. Carinii increased the microbiological verification of infections by 35%. Viral infections were few in our protected population but caused severe infectious complications in these patients.

Child↗
PubMed2005

Errors in the medication process: frequency, type, and potential clinical consequences.

OBJECTIVE: To investigate the frequency, type, and consequences of medication errors in more stages of the medication process, including discharge summaries. DESIGN: A cross-sectional study using three methods to detect errors in the medication process: direct observations, unannounced control visits, and chart reviews. With the exception of errors in discharge summaries all potential medication error consequences were evaluated by physicians and pharmacists. SETTING: A randomly selected medical and surgical department at Aarhus University Hospital, Denmark. STUDY PARTICIPANTS: Eligible in-hospital patients aged 18 or over (n = 64), physicians prescribing drugs and nurses dispensing and administering drugs. MAIN OUTCOME MEASURES: Frequency, type, and potential clinical consequences of all detected errors compared with the total number of opportunities for error. RESULTS: We detected a total of 1065 errors in 2467 opportunities for errors (43%). In worst case scenario 20-30% of all evaluated medication errors were assessed as potential adverse drug events. In each stage the frequency of medication errors were-ordering: 167/433 (39%), transcription: 310/558 (56%), dispensing: 22/538 (4%), administration: 166/412 (41%), and finally discharge summaries: 401/526 (76%). The most common types of error throughout the medication process were: lack of drug form, unordered drug, omission of drug/dose, and lack of identity control. CONCLUSION: There is a need for quality improvement, as almost 50% of all errors in doses and prescriptions in the medication process were caused by missing actions. We assume that the number of errors could be reduced by simple changes of existing procedures or by implementing automated technologies in the medication process.

Adult↗
PubMed2005

Impact of bacterial NO3(-) transport on sediment biogeochemistry.

Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3(-) reduction from denitrification to dissimilatory NO3(-) reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H2S with NO3(-) and transported S0 to the sediment surface for aerobic oxidation.

Geologic Sediments↗
PubMed2004

Effects of zinc pyrithione and copper pyrithione on microbial community function and structure in sediments.

The effects of the new antifouling biocides, zinc pyrithione (ZPT) and copper pyrithione (CPT), on microbial communities in estuarine sediments were studied in microcosms. As functional endpoints, fluxes of nutrients (NO3-, NH4+, HPO4(2-), Si(OH)4) and protein synthesis ([14C]leucine incorporation) were used, whereas molecular fingerprinting methods (polymerase chain reaction/denaturing gradient gel electrophoresis) were used to describe the bacterial community structure. The lowest-observed-effect concentration (LOEC) for ZPT was 0.001 nmol/g dry sediment for the phosphate flux and total DNA content, whereas the LOEC for CPT was 0.1 nmol/g dry sediment for the nitrate flux and total DNA content. Nitrate fluxes increased significantly following additions of both ZPT and CPT, whereas ammonium fluxes decreased significantly after ZPT addition, suggesting changes in the nitrification and denitrification processes. The total DNA content decreased significantly following addition of both ZPT and CPT, but at the highest addition of ZPT (10 nmol ZPT/g dry sediment), an increase in total DNA content was found. Increased protein synthesis and bacterial diversity were also observed at this concentration of ZPT, suggesting growth of tolerant opportunistic species.

Bacteria↗
PubMed2003

The Lotus japonicus ndx gene family is involved in nodule function and maintenance.

To elucidate the function of the ndx homeobox genes during the Rhizobium-legume symbiosis, two Lotus japonicus ndr genes were expressed in the antisense orientation under the control of the nodule-expressed promoter Psenod12 in transgenic Lotus japonicus plants. Many of the transformants obtained segregated into plants that failed to sustain proper development and maintenance of root nodules concomitant with down-regulation of the two ndx genes. The root nodules were actively fixing nitrogen 3 weeks after inoculation, but the plants exhibited a stunted growth phenotype. The nodules on such antisense plants had under-developed vasculature and lenticels when grown on medium lacking nitrogen sources. These nodules furthermore entered senescence earlier than the wild-type nodules. Normal plant growth was resumed upon external addition of nitrogen. This suggests that assimilated nitrogen is not properly supplied to the plants in which the two ndx genes are down-regulated. The results presented here, indicate that the ndx genes play a role in the development of structural nodule features, required for proper gas diffusion into the nodule and/or transport of the assimilated nitrogen to the plant.

Cell Nucleus↗