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Biomedical subjects

P Roos

Publications and source records attributed to P Roos.

At least 19 recordsLinked to original sources
PubMed2004

Distribution and flux of 238Pu, 239,240Pu, 241Am, 137Cs and 210Pb to high arctic lakes in the Thule district (Greenland).

Environmental samples (soil, sediment and lake water) in the Thule area (NW Greenland) have been studied to assess the contamination of radionuclides originating from a nuclear weapons accident (the Thule accident in 1968). Four lakes were chosen at different distances from the point of impact with the Thule air base community situated in between. The sedimentation rates in the lakes varied from 0.4 mm a(-1) (5 mg cm(-2) a(-1)) to 1.6 mm a(-1) (82 mg cm(-2) a(-1)). With these sedimentation rates, it is not possible to resolve the (239,240)Pu global fallout peak from a possible (239,240)Pu "accident" peak in the sediment depth profiles. However, the (239,240)Pu/(137)Cs and the (238)Pu/(239,240)Pu ratios agreed well with global fallout ratios, indicating that plutonium originating from the accident had not reached these lakes. This also indicates that the Thule air base community has probably only been exposed to radionuclides from the accident to a very limited extent. A limited study showed that (210)Pb could not be used as a normalizing nuclide to explain the transport of transuranic elements from the catchment area to the lake, i.e. (210)Pb has a different transport mechanism from that of the transuranic elements studied in this investigation.

Arctic Regions↗
PubMed2004

No significant contribution of arbuscular mycorrhizal fungi to transfer of radiocesium from soil to plants.

The diffuse pollution by fission and activation products following nuclear accidents and weapons testing is of major public concern. Among the nuclides that pose a serious risk if they enter the human food chain are the cesium isotopes 137Cs and 134Cs (with half-lives of 30 and 2 years, respectively). The biogeochemical cycling of these isotopes in forest ecosystems is strongly affected by their preferential absorption in a range of ectomycorrhiza-forming basidiomycetes. An even more widely distributed group of symbiotic fungi are the arbuscular mycorrhizal fungi, which colonize most herbaceous plants, including many agricultural crops. These fungi are known to be more efficient than ectomycorrhizas in transporting mineral elements from soil to plants. Their role in the biogeochemical cycling of Cs is poorly known, in spite of the consequences that fungal Cs transport may have for transfer of Cs into the human food chain. This report presents the first data on transport of Cs by these fungi by use of radiotracers and compartmented growth systems where uptake by roots and mycorrhizal hyphae is distinguished. Independent experiments in three laboratories that used different combinations of fungi and host plants all demonstrated that these fungi do not contribute significantly to plant uptake of Cs. The implications of these findings for the bioavailability of radiocesium in different terrestrial ecosystems are discussed.

Biological Transport↗
PubMed2004

Respiratory arrest in systemic lupus erythematosus due to phrenic nerve neuropathy.

Diaphragmatic weakness in patients with systemic lupus erythematosus (SLE) is a controversial issue and is claimed to have a neuropathic, myopathic or unknown pathogenesis. In this patient a predominantly motor neuropathy with diaphragmatic paralysis due to axonal involvement of the phrenic nerve was discovered and successfully treated with immunosuppressive drugs.

Aged↗
PubMed2003

Long-term study of 99Tc in the marine environment on the Swedish west coast.

The activity concentration of (99)Tc in brown seaweed (Fucus vesiculosus and Fucus serratus) and seawater were analysed in samples collected in 1991, 1995 and 2001 at several stations along the Swedish west coast. In addition to these locations, a well-defined site (Särdal, 56.76 degrees N, 12.63 degrees E) was included with (99)Tc activity concentration data in seaweed from 1967 to 2000. Over the years, the major source of (99)Tc in the coastal waters of western Sweden has been the radioactive liquid discharge from the nuclear fuel reprocessing plant in Sellafield (UK) transported via ocean currents in the North Sea. The (99)Tc activity concentration in seaweed at the Särdal site increased from approximately 30 Bq kg(-1) up to 230 Bq kg(-1) (dry weight) between 1997 and 2000 due to the Sellafield EARP (Enhanced Actinide Removal Plant) discharges in 1995-1996, yielding an approximate transport time of 4-5 years between the Irish Sea and the Kattegat. Due to the very sharp gradient in (99)Tc concentration between the Baltic Sea and the North Sea, (99)Tc is presently one of the best transit tracers for the recent ventilation events in the Baltic Sea.

Cesium Radioisotopes↗
PubMed2002

Transport of plutonium in surface and sub-surface waters from the Arctic shelf to the North Pole via the Lomonosov Ridge.

New data on the levels and long-range transport of plutonium in the Arctic Ocean, recorded in the course of two expeditions to this zone in 1994 and 1996, are discussed in this paper. Specifically, approximately 100 plutonium measurements in surface and sub-surface water sampled at 58 separate stations throughout the Kara, Laptev and East Siberian Seas, as well as along latitudinal transects across the Lomonosov Ridge, are reported and interpreted in terms of the circulation pathways responsible for the transport of this element from the North Atlantic to the Arctic Shelf and into the Arctic interior. In addition, the behaviour of plutonium in its transit through the vast Arctic shelf seas to open waters under extreme environmental conditions is discussed in terms of the partitioning of plutonium between filtered (<0.45 microm) seawater and suspended particulate, and its association with colloidal matter. Finally, limited evidence of the presence of a colloidal plutonium component in Arctic waters subject to direct riverine input is adduced.

Arctic Regions↗
PubMed2001

Longitudinal electroproduction of charged pions from (1)H, (2)H, and (3)He.

Separated longitudinal and transverse cross sections for charged pion electroproduction from (1)H, (2)H, and (3)He were measured at Q(2) = 0.4 (GeV/c)(2) for two values of the invariant mass, W = 1.15 GeV and W = 1.60 GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in (3)He at W = 1.60 GeV. The W = 1.15 GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production.

Journal Article↗
PubMed2001

Measurement of the high energy two-body deuteron photodisintegration differential cross section.

The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.

Journal Article↗
PubMed2001

Measurement of the electric form factor of the neutron through d-->(e-->,e(')n)p at Q2 = 0.5 (GeV/c)(2).

We report the first measurement using a solid polarized target of the neutron electric form factor G(n)(E) via d-->(e-->,e(')n)p. G(n)(E) was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia ( 15ND3). The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility in quasifree kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find G(n)(E) = 0.04632+/-0.00616(stat)+/-0.00341(syst) at Q2 = 0.495 (GeV/c)(2).

Journal Article↗
PubMed2001

Radionuclide fluxes at a plant manufacturing dicalcium phosphate for domestic animals.

We have studied a phosphate rock plant which produces dicalcium phosphate (DCP), used as a source of calcium and phosphorus for domestic animals. A by-product in the manufacturing process is calcium chloride which is used in the oil industry, the food industry and as road-salt. The objectives of our study were to describe the fluxes of radionuclides from the 238U decay series and to estimate the radiation doses to workers at the plant. The radionuclides in the phosphate rock were found to be in secular radioactive equilibrium with 238U, with an average activity concentration of 837 Bq kg-1. Separation and concentration processes were observed at different stages in the plant. Most of the 226Ra was found in the calcium chloride, while the major part of the 238U, about 950 Bq kg-1, was found in the dicalcium phosphate. The annual occupational effective dose to the workers was found to be below the 1 mSv limit recommended by ICRP (1991a) for the public. This study has shown a good example of an important non-nuclear industry with a high input of natural radionuclides with several conceivable pathways to man.

Animal Feed↗
PubMed2001

Cataract surgery and effectiveness. 2. An index approach for the measurement of output and efficiency of cataract surgery at different surgery departments.

PURPOSE: To describe a model for comparing the performance of cataract surgery among ophthalmology departments in terms of economic efficiency. METHODS: An index approach for the measurement of outcome of cataract surgery is modeled. The index approach uses information about activities and difficulties in daily life as well as visual acuity and age. The change in activities and difficulties after surgery is expressed by changes in distances, and an overall index score is calculated as ratios of values to distances. Values to distances are estimated as solutions to linear programming problems. Index scores are calculated for two groups of patients, those with an ocular co-morbidity and those without. Economic efficiency is also estimated by use of an index approach. In the estimation of efficiency we use the calculated index scores of outcome of surgery as a measure of output of the ophthalmology department. Four different departments providing cataract surgery are compared. RESULTS: The studied departments showed differences to a great extent when traditional measures of cataract surgery outcomes were used. These differences changed when the outcomes were compared by use of index scores. When economic efficiency was calculated the difference between the departments was further reduced and only one department was considered inefficient according to the model. CONCLUSION: An index approach was used to study outcomes of cataract surgery and economic efficiency in four departments. This approach takes into account the complexity of cost in relation to feasible outcome. The ranking between the departments described by traditional methods turned out differently using the model.

Cataract Extraction↗
PubMed2000

In situ sorption of technetium using activated carbon

The sorption of technetium in pertechnetate form on carbon has been investigated. The sorption is pH dependent with maximal distribution coefficients, Kd, in the order of 10(6) at pH 2-4 for activated carbon with a grain size < or = 100 microm. The equilibrium time to reach such distribution coefficient was about 5 h at room temperature. The exact mechanisms for the sorption are not fully understood but reduction of Tc by the carbon might be an important process. Technetium can effectively and rapidly (5 l min(-1)) be sorbed from very large volumes (several hundred liters) of environmental waters on commercial cartridge filters impregnated with activated carbon. After incineration, the filters can be analyzed for 99Tc by conventional methods.

Journal Article↗
PubMed2000

Cataract surgery and effectiveness. 1. Variation in costs between different providers of cataract surgery.

PURPOSE: To describe and analyse the cost of cataract surgery in four community-run eye clinics in Sweden and also to analyse differences in cost between these clinics. METHODS: The average cost of a cataract surgery episode was calculated including one pre-operative visit, the surgery itself and the post-operative visits. Included in the analysis were the costs of disposables, personnel, rent, depreciation, general anaesthesia, bed days and education. Excluded were the costs of complications and overhead costs. RESULTS: The average cost for one cataract surgery episode was 5052/6915 SEK (1 Euro = 8.57 SEK) with a variation from 4436/6202 to 6130/8293 between the clinics. The lower sum represents a minimum cost of personnel, the higher sum a maximum cost. CONCLUSION: A large variation in costs of cataract surgery was found in four providers of cataract surgery. Nearly all clinics studied had one or more areas with much higher costs than average.

Cataract Extraction↗
PubMed1999

Inhibition of ATM and ATR kinase activities by the radiosensitizing agent, caffeine.

Caffeine exposure sensitizes tumor cells to ionizing radiation and other genotoxic agents. The radiosensitizing effects of caffeine are associated with the disruption of multiple DNA damage-responsive cell cycle checkpoints. The similarity of these checkpoint defects to those seen in ataxia-telangiectasia (A-T) suggested that caffeine might inhibit one or more components in an A-T mutated (ATM)-dependent checkpoint pathway in DNA-damaged cells. We now show that caffeine inhibits the catalytic activity of both ATM and the related kinase, ATM and Rad3-related (ATR), at drug concentrations similar to those that induce radiosensitization. Moreover, like ATM-deficient cells, caffeine-treated A549 lung carcinoma cells irradiated in G2 fail to arrest progression into mitosis, and S-phase-irradiated cells exhibit radioresistant DNA synthesis. Similar concentrations of caffeine also inhibit gamma- and UV radiation-induced phosphorylation of p53 on Ser15, a modification that may be directly mediated by the ATM and ATR kinases. DNA-dependent protein kinase, another ATM-related protein involved in DNA damage repair, was resistant to the inhibitory effects of caffeine. Likewise, the catalytic activity of the G2 checkpoint kinase, hChk1, was only marginally suppressed by caffeine but was inhibited potently by the structurally distinct radiosensitizer, UCN-01. These data suggest that the radiosensitizing effects of caffeine are related to inhibition of the protein kinase activities of ATM and ATR and that both proteins are relevant targets for the development of novel anticancer agents.

Ataxia Telangiectasia Mutated Proteins↗
PubMed1999

Deviant trafficking of I-Ad mutant molecules is reflected in their peptide binding properties.

I-Ad molecules harboring single amino acid changes in the conserved 80-82 region of the beta-chain show altered trafficking in invariant chain (Ii)-negative cell lines. Since residues beta81 and beta82 form hydrogen bonds with the backbone of bound peptide, alterations in this region may result in distinct MHC class II conformers that are targeted aberrantly. We examined the assembly and peptide binding properties of the mutant I-Ad molecules generated by in vitro translation. Indeed, loss of a single hydrogen bond at beta81, or of two hydrogen bonds at beta82, is sufficient to render I-Ad incapable of stable interaction with CLIP and other antigenic peptides, despite normal assembly with intact invariant chain. These results suggest that stable interaction of MHC class II molecules with peptide requires the integrity of the H-bond network between residues in the MHC class II alpha-helices and bound peptide, and that conformational features revealed by stable peptide binding are critical for MHC class II intracellular transport.

Amino Acid Sequence↗
PubMed1998

Nonaqueous capillary electrophoretic separation and thermo-optical absorbance detection of five tricyclic antidepressants and metabolism of amitriptyline by Cunninghamella elegans.

We developed a technique based on nonaqueous capillary electrophoresis and laser-based thermo-optical absorbance detection to assay five antidepressants with similar structures and mass-to-charge ratios. A mixture of methanol and acetonitrile with ammonium acetate was essential to achieve baseline resolution of these compounds. We investigated the effects of ammonium acetate concentration, temperature, applied voltage, and capillary length on separation efficiency. The nonaqueous capillary electrophoresis and laser-based thermo-optical absorbance detection technique was used to study the metabolism of amitriptyline by Cunninghamella elegans. Sample preparation procedures were simplified for fast screening of the parent drug and its metabolites. Reproducible electropherograms were obtained from replicate cultures of C. elegans growing in the presence of amitriptyline.

Amitriptyline↗
PubMed1998

Catquest questionnaire for use in cataract surgery care: assessment of surgical outcomes.

PURPOSE: To demonstrate the outcome for patients after cataract extraction using the Catquest cataract questionnaire and discuss the models validity in assessing outcome. SETTING: Thirty-five Swedish departments of ophthalmology. METHODS: Patients having cataract extraction performed by surgeons from 35 Swedish departments of opthalmology participated in the study. The questionnaire was given to 2970 consecutive patients having surgery during March 1995 at the participating surgical units. The questionnaire was sent by mail to patients and completed on a voluntary basis. It focuses on visual disabilities in daily life, activity level, cataract symptoms, and degree of independence. The results form the questionnaire are interpreted using a benefit matrix that credits not only a decrease in visual disabilities and cataract symptoms but also an improvement in or maintenance of a preoperative activity level. RESULTS: Complete surgical outcome data and completed preoperative and postoperative questionnaires were available in 1933 cases (65.1%). Benefit from surgery according to the model was achieved by 90.9% of the patients. Patients having their second cataract extraction had the highest frequency of the greatest benefit form surgery. There was good agreement between the different levels of benefit from surgery according to the model and the patient's global rating of his or her vision or achieved visual acuity after surgery, respectively. Patients with missing data (did not return postoperative questionnaire or had missing surgical result variables) were older and had a higher frequency of other diseases and handicaps. CONCLUSION: The Catquest cataract questionnaire allowed the outcome of cataract surgery to be graded by different levels of benefit. There seemed to be good agreement between this model of assessment and the patient's global rating of his or her vision. Missing data may be a problem when a postal questionnaire is used.

Activities of Daily Living↗
PubMed1997

Catquest questionnaire for use in cataract surgery care: description, validity, and reliability.

PURPOSE: To describe and evaluate the Catquest self-assessment questionnaire for cataract patients. SETTING: Thirty-five Swedish departments of ophthalmology. METHODS: The Catquest is designed to be used by cataract surgeons for continuous quality control regarding appropriateness and outcome of surgery. It is administered before and after cataract surgery. The questionnaire focuses on visual disabilities in daily life, activity level, cataract symptoms, and degree of independence. The results are interpreted using a benefit matrix that credits not only a decrease in visual disabilities and cataract symptoms but also an improvement or a maintenance of a preoperative activity level. The questionnaire was used by consecutive patients having surgery during March 1995 at the participating surgical units. RESULTS: A full range of responses was given to all questions. A strong relationship was found between patients' responses to questions about visual disabilities in daily life and their general opinion about vision (P < .001). The answers showed a high stability when test-retest reliability was evaluated and a high internal consistency when different questions about visual disabilities were compared (P < .001). The answers from cataract patients before surgery were significantly different from those of a control group that did not have cataract (P < .0001). CONCLUSION: The Catquest had high validity and reliability when used as a disease-specific instrument testing visual disabilities in patients having cataract extraction.

Aged↗