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Biomedical subjects

Mats Nilsson

Publications and source records attributed to Mats Nilsson.

34 records · Page 2Linked to original sources
PubMed2004

Is frequent attendance a persistent characteristic of a patient? Repeat studies of attendance pattern at the family practitioner.

OBJECTIVE: To assess the extent of frequent attendance as a persistent characteristic of patients by repeat studies of attendance at a health centre. DESIGN: A follow-up of frequent attenders and compared patients in 1991 among frequent attenders in 1996. SETTING: Mariehem health centre in Umeå in northern Sweden providing care for 10,500 and 12,000 inhabitants in 1991 and 1996, respectively. SUBJECTS: Frequent attenders, defined as patients who had at least 5 consultations with physicians during 1 year at the health centre, compared to attenders who had between 1 and 4 consultations in 1991 and 1996. RESULTS: The proportion of people who lived in the area and consulted a doctor at the health centre at least once during 1 year increased from 40.0% in 1991 to 45.2% in 1996. The number of frequent attenders increased from 179 to 303 and they took 15% and 20% of all consultations in 1991 and 1996, respectively. Twenty-five patients (21 females and 4 males) were identified as frequent attenders in both years. CONCLUSION: With the exception of a small group of patients, mostly females, frequent attendance seems not to be a persistent characteristic of patients.

Family Practice↗
PubMed2004

Whole-body autoradiography reveals that the Peptostreptococcus magnus immunoglobulin-binding domains of protein L preferentially target B lymphocytes in the spleen and lymph nodes in vivo.

Protein L is an immunoglobulin (Ig)-binding protein produced by the Gram-positive bacterium Peptostreptococcus magnus that interacts with the variable region of Ig kappa light chains. The Ig light chain-binding capacity of protein L gives it the potential to interact with cells expressing surface Ig such as B cells. The present study was performed to address the in vivo trafficking of protein L at both the organ and the cellular level. Using the powerful technique of whole-body autoradiography in a murine model system, we demonstrate specific targeting of protein L to secondary lymphoid tissues in whole-animal analysis. The observed targeting depends on the capacity to interact with murine Ig, as tissue targeting was not apparent in mice given protein H, an Ig-binding protein produced by Streptococcus pyogenes with affinity for human but not murine Ig. Tissue targeting data were combined with flow cytometry analysis, which demonstrated the capacity of protein L to target and activate B lymphocytes in vivo. B cells targeted by protein L had increased surface expression of CD86 and MHC-II, and protein L was present in vacuolar compartments of B cells. Protein L did not bind T cells or natural killer cells but had some capacity to target dendritic cells and macrophages. The data show that protein L preferentially targets secondary lymphoid organs, and activates and is internalized by B cells in vivo. Furthermore, the observed tissue and cell targeting properties require an affinity for murine Ig. These data support the potential use of this Ig-binding protein as a targeting approach to deliver agents to defined cell populations in vivo.

Animals↗
PubMed2003

Parallel gene analysis with allele-specific padlock probes and tag microarrays.

Parallel, highly specific analysis methods are required to take advantage of the extensive information about DNA sequence variation and of expressed sequences. We present a scalable laboratory technique suitable to analyze numerous target sequences in multiplexed assays. Sets of padlock probes were applied to analyze single nucleotide variation directly in total genomic DNA or cDNA for parallel genotyping or gene expression analysis. All reacted probes were then co-amplified and identified by hybridization to a standard tag oligonucleotide array. The technique was illustrated by analyzing normal and pathogenic variation within the Wilson disease-related ATP7B gene, both at the level of DNA and RNA, using allele-specific padlock probes.

Adenosine Triphosphatases↗
PubMed2003

Multiplexed genotyping with sequence-tagged molecular inversion probes.

We report on the development of molecular inversion probe (MIP) genotyping, an efficient technology for large-scale single nucleotide polymorphism (SNP) analysis. This technique uses MIPs to produce inverted sequences, which undergo a unimolecular rearrangement and are then amplified by PCR using common primers and analyzed using universal sequence tag DNA microarrays, resulting in highly specific genotyping. With this technology, multiplex analysis of more than 1,000 probes in a single tube can be done using standard laboratory equipment. Genotypes are generated with a high call rate (95%) and high accuracy (>99%) as determined by independent sequencing.

Cells, Cultured↗
PubMed2003

Lateral-flow and up-converting phosphor reporters to detect single-stranded nucleic acids in a sandwich-hybridization assay.

Up-converting Phosphor Technology (UPT) particles were used as reporters in lateral-flow (LF) assays to detect single-stranded nucleic acids. The 400-nm phosphor particles exhibit strong visible luminescence upon excitation with infrared (IR) light resulting in the total absence of background autofluorescence from other biological compounds. A sandwich-type hybridization assay was applied using two sequence-specific oligonucleotides. One of the oligonucleotides probes was covalently bound to the UPT particle (reporter) for direct labeling and detection, whereas the second oligonucleotide probe contained biotin for capture by avidin during LF. The whole procedure of hybridization, UPT-LF detection, and analysis required a minimum time of 20 min. Moreover, aiming at minimal equipment demands, the hybridization conditions were chosen such that the entire assay could be performed at ambient temperature. During lateral flow, only targets hybridized to both capture and detection oligonucleotide were trapped and detected at an avidin capture line on the LF strip. Analysis (IR scanning) of the strips was performed in an adapted microtiter plate reader provided with a 980-nm IR laser for excitation of the phosphor particles (a portable reader was also available). Visible luminescence was measured and presented as relative fluorescence units (RFU) allowing convenient quantitation of the phosphor signal. With the assay described here as little as 0.1 fmol of a specific single-stranded nucleic acid target was detected in a background of 10 microg fish sperm DNA.

Animals↗
PubMed2003

PCR-generated padlock probes distinguish homologous chromosomes through quantitative fluorescence analysis.

Conventional cytogenetic techniques can distinguish homologous chromosomes in a qualitative manner based upon obvious morphological features or using in situ hybridization methods that yield qualitative data. We have developed a method for quantitative genotyping of single-nucleotide variants in situ using circularizable DNA probes, so-called padlock probes, targeting two different alpha satellite repeat variants present in human chromosome 7 centromeres, and a single-nucleotide variation in alpha satellite repeats on human chromosome 15 centromeres. By using these PCR-generated padlock probes, we could quantitatively distinguish homologous chromosomes and follow the transmission of the chromosomes by in situ analysis during three consecutive generations.

Centromere↗
PubMed2003

Cardiovascular disease and diabetes in the Northern Sweden Health and Disease Study Cohort - evaluation of risk factors and their interactions.

The purpose of this paper is, first, to describe the organization, sampling procedures, availability of samples/database, ethical considerations, and quality control program of the Northern Sweden Health and Disease Study Cohort. Secondly, some examples are given of studies on cardiovascular disease and diabetes with a focus on the biomarker programme. The cohort has been positioned as a national and international resource for scientific research.

Cardiovascular Diseases↗
PubMed2003

Countrywide estimates of forest variables using satellite data and field data from the National Forest Inventory.

About 55% of the land area in Sweden is covered by forest. Presently, there is no uniform and geographically explicit description of the forest cover for Sweden. Independent data sources already existing are satellite data from Landsat TM and SPOT HRV, map masks and forest inventory plots. Together, they provide the possibility of computing estimates of forest variables such as stem volume and stand age. The accuracy for these estimations will be low on the pixel level, but higher on a stand level. This type of raster-based forest data is useful for authorities when planning how timber resources should be utilized or for monitoring purposes. The production line that was developed to create a countrywide database of forest variable estimates in a cost-efficient way is described. Accuracy of forest variable estimates for an area in southwestern Sweden was assessed at stand level. Results showed 33% overall root mean square error for the estimates of total wood volume, and 23% for the age estimates.

Conservation of Natural Resources↗
PubMed2002

Real-time monitoring of rolling-circle amplification using a modified molecular beacon design.

We describe a method to monitor rolling-circle replication of circular oligonucleotides in dual-color and in real-time using molecular beacons. The method can be used to study the kinetics of the polymerization reaction and to amplify and quantify circularized oligonucleotide probes in a rolling-circle amplification (RCA) reaction. Modified molecular beacons were made of 2'-O-Me-RNA to prevent 3' exonucleolytic degradation by the polymerase used. Moreover, the complement of one of the stem sequences of the molecular beacon was included in the RCA products to avoid fluorescence quenching due to inter-molecular hybridization of neighboring molecular beacons hybridizing to the concatemeric polymerization product. The method allows highly accurate quantification of circularized DNA over a broad concentration range by relating the signal from the test DNA circle to an internal reference DNA circle reporting in a distinct fluorescence color.

Chromatography, High Pressure Liquid↗
PubMed2002

Making ends meet in genetic analysis using padlock probes.

Padlock probes are molecular tools that combine highly specific target sequence recognition with the potential for multiplexed analysis of large sets of target DNA or RNA sequences. In this brief review, we exemplify the ability of these probes to distinguish single-nucleotide target sequence variants. We further discuss means to detect the location of target sequences in situ, and to amplify reacted padlock probes via rolling-circle replication, as well as to sort reaction products on tag-arrays. We argue that the probes have the potential to render high-throughput genetic analyses precise and affordable.

DNA↗
PubMed2002

Sex differences in cobalamin vitamin B12 opinions of Swedish physicians.

The aim of the study was to elucidate possible sex differences in knowledge, competence and attitudes behind decision-making on cobalamin-associated problems (vitamin B(12)). The study was conducted by postal questionnaires to Swedish physicians in 1996-98. The participants were recruited by random sampling of general practitioners (1996, 1998), and a total sampling of geriatricians (1998). The overall response rate was 71%. The study group comprised 480 female physicians and 526 male physicians. The responses to 24 statements in the questionnaire were measured by means of visual analogue scales. Group differences were evaluated by medians and shapes of distributions. The female doctors appeared to value patient-related symptoms and signs more than male doctors. Conversely, male doctors relied on laboratory tests more than female doctors. As reflected by questionnaire answers, female doctors appeared to be more informed than male doctors on cobalamin-associated clinical problems. Group differences between the sexes were marginal from a numerical point of view. It is suggested that the statistical differences observed should be regarded as negligible until confirmed by further studies.

Clinical Competence↗
PubMed2002

Are gadolinium-based contrast media really safer than iodinated media for digital subtraction angiography in patients with azotemia?

Gadolinium chelates, intended as intravenous contrast media for magnetic resonance imaging, have been regarded as nonnephrotoxic and recommended to replace iodinated contrast media in patients with azotemia who are undergoing digital subtraction angiography (DSA). High intraarterial doses (up to 220 mmol of gadodiamide) have been used, with a 40% incidence of nephropathy. The authors discourage the use of gadolinium for DSA for several reasons. (a) There exist no randomized studies comparing the nephrotoxic effects of gadolinium-based and iodinated media at equal-attenuating concentrations and doses. (b) Gadolinium-based media are hypertonic, a pathogenetic factor in contrast medium-induced nephropathy after renal angiography, with an osmolality two to seven times that of plasma. Iodinated media in concentrations that are equally attenuating with gadolinium-based media can be made isotonic. (c) In vitro measurements indicate that 0.5 mol/L gadolinium chelates are equally attenuating with 60-80 mg iodine per milliliter at the commonly used 70-90-kV range used for DSA. Thus, 50 mL of 0.5 mol/L gadolinium chelate ( approximately 0.3 mmol/kg in an 80-kg person) would be equally attenuating with a dose of 3-4 g of iodine in an iodinated medium (eg, 50 mL iohexol at 60-80 mg I/mL or 10-13 mL at 300 mg I/mL). (d) By combining these data on attenuation and results of toxicity studies in mice, the general toxicity of gadolinium chelates may be six to 25 times higher than that of equal-attenuating doses of iodinated media at 70-kV DSA. Thus, the authors believe that at equal-attenuating doses for DSA, modern iodinated contrast media should result in a lower toxic load on the body than with presently available gadolinium chelates.

Angiography, Digital Subtraction↗
PubMedDate not supplied

Molecular tools for a molecular medicine: analyzing genes, transcripts and proteins using padlock and proximity probes.

Procedures and reagents are needed to specifically detect all the macromolecules that are being identified in the course of genome projects. We discuss how this challenge may be met using a set of ligation-based reagents termed padlock probes and proximity ligation probes. These probes include elements with affinity for specific nucleic acid and protein molecules, respectively, along with unique identifier DNA sequence elements that encode the identity of the recognized target molecules. The information content of DNA strands that form in the detection reactions are recorded after amplification, allowing the recognized target molecules to be identified. The procedures permit highly specific solution-phase or localized analyses of large sets of target molecules as required in future molecular analyses.

Clinical Medicine↗