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Biomedical subjects

A Olofsson

Publications and source records attributed to A Olofsson.

At least 19 recordsLinked to original sources
PubMed2005

'If only I manage to get home I'll get better'--interviews with stroke patients after emergency stay in hospital on their experiences and needs.

OBJECTIVE: To find out about the experiences of stroke patients concerning their falling ill, their stay in hospital, discharge and homecoming. DESIGN: Qualitative methods using in-depth interviews. SUBJECTS AND SETTING: Nine strategically chosen patients and in five cases near family members were interviewed in their homes four months post stroke and following care at the Stroke Centre, University Hospital of Northern Sweden, Umeå. RESULTS: Three main categories with subcategories were brought to the fore from the interviews: 'Responsible and implicated', 'Depersonalized object for caring measures' and 'The striving for repersonalization and autonomy'. The patients got the most important insights and understanding about their state and the consequences when they came home. CONCLUSION: The three main categories that were found mirror the crisis which becoming ill entails and the process gone through when the individual takes control again of his or her life. The patients saw coming home as an important factor for their recovery and rehabilitation. The health care system needs to develop strategies to make use of the power of this attitude with the patients and to use the patients' own milieu in rehabilitation after stroke.

Adaptation, Psychological↗
PubMed2003

Relationship between fibrinolytic activity and gingival inflammatory reaction in young individuals.

The fibrinolytic system (the plasminogen activating system) is involved in several physiological and pathological processes. Through the transformation of plasminogen to the aggressive broad spectrum protease plasmin, potent enzymatic activity is released. Plasmin acts directly on connective tissue components, and indirectly by activating proforms of the metalloproteinases. The destructive potential of the fibrinolytic system may thus be of importance for the initiation and progression of periodontal diseases. Earlier studies have shown high concentrations of the plasminogen activator t-PA and its inhibitor PAI-2 in gingival crevicular fluid (GCF) as well as enhanced concentrations in areas of gingival inflammation. The aim of this study was to investigate a possible relationship between the gingival inflammatory reactivity and the fibrinolytic activity in gingival crevicular fluid. Thirty-one young individuals took part in the study. Gingival Index scores and Plaque Index scores were assessed and used to formulate a score expressing an individuals' inflammatory response to microbial plaque levels (Relative G/P score). The fibrinolytic activity of GCF was assessed with a fibrin gel lysis assay, and the levels of t-PA and PAI-2 were assayed with ELISAs. All samples showed fibrinolytic activity. A positive correlation between the fibrinolytic activity and Relative G/P score was found. Thus, in individuals with an enhanced reactivity to dental plaque, a higher plasminogen activating activity in GCF was seen. This indicates a higher potential for tissue proteolysis in these individuals, possibly facilitating spread and deeper involvement of the lesions.

Adolescent↗
PubMed2001

Capture of a dimeric intermediate during transthyretin amyloid formation.

Point mutations in the human plasma protein transthyretin are associated with the neurological disorder familial amyloidosis with polyneuropathy type 1. The disease is characterized by amyloid fibril deposits causing damage at the site of deposition. Substitution of two amino acids in the hydrophobic core of transthyretin lead to a mutant that was very prone to form amyloid. In addition, this mutant has also been shown to induce a toxic response on a neuroblastoma cell line. Renaturation of the transthyretin mutant at low temperature facilitated the isolation of an amyloid-forming intermediate state having the apparent size of a dimer. Increasing the temperature effectively enhanced the rate of interconversion from a partly denatured protein to mature amyloid. Using circular dichroism the beta-sheet content of the formed mature fibrils was significantly lower than that of the native fold of transthyretin. Morphology studies using electron microscopy also indicated a temperature-dependent transformation from amorphous aggregates toward mature amyloid fibrils. In addition, 1-anilino-8-naphtalenesulfonate fluorescence studies suggested the loss of the thyroxin-binding channel within both the isolated intermediate and the mature fibrils.

Amyloid↗
PubMed2001

Kinetics of the AHL regulatory system in a model biofilm system: how many bacteria constitute a "quorum"?

Acylated homoserine lactones (AHLs) regulate a wide variety of phenotypes in Gram-negative bacteria. Most research suggests that AHL-mediated phenotypes are not expressed in populations until late logarithmic phase or stationary phase. Here, we model how the concentration of AHLs inside bacterial cells and in a biofilm changes over time as a function of population growth rate, diffusion of AHLs and the rate of autoinduction. Our theoretical results show that the concentration of AHLs inside a single bacterium (and by implication induction of a phenotype) has a non-trivial behaviour over time, and often exhibits a rapid increase early in population growth. This rapid increase is followed by a plateau, followed by another rise in the concentration of AHLs, to a second plateau. High concentrations of AHLs inside the bacterial cell early in population growth are positively affected by slow diffusion rates out of the cell and the biofilm, slow bacterial growth rates and fast autoinduction. In contrast, fast growth rates, slow autoinduction rates and high diffusion rates result in a high concentration plateau in stationary phase. More generally, the density-dependent nature of AHL regulation can be viewed as a trade-off between factors that dilute intracellular concentrations of AHLs (diffusion out of the cell, cell division), and those that increase concentrations (a slowing or restriction of diffusion or growth, or autoinduction). These results suggest that expression of AHL-mediated phenotypes can occur at relatively low cell densities and low external/environmental AHL concentrations.

4-Butyrolactone↗
PubMed2001

Antibody recognition of amyloidogenic transthyretin variants in serum of patients with familial amyloidotic polyneuropathy.

Familial amyloidotic polyneuropathy (FAP) is a late-onset inherited disease characterized by the deposition of amyloid fibrils. FAP is associated with mutations on the transthyretin (TTR) gene. A monoclonal antibody, MAb 39-44, reacting with high molecular weight aggregates of TTR but not with tetrameric TTR has recently been generated and characterized. This antibody recognizes a cryptic epitope that is expressed in isolated recombinant amyloidogenic mutants and in ex vivo amyloid. In the present work we show that this amyloid-specific antibody specifically recognizes in a direct enzyme-linked immunoassay (ELISA) plasma TTR from carriers of various mutations associated with FAP, both in asymptomatic individuals and in patients. In contrast, it does not react with plasma TTR from healthy individuals or that from carriers of nonpathogenic mutations. Using the ELISA developed in this study we identified three different TTR mutations in Portuguese patients with neuropathy of unknown cause, later shown to have amyloid tissue deposition. This antibody recognizes conformations that express cryptic epitopes shared by amyloidogenic TTR variants associated with FAP, not present among nonpathogenic TTR molecules. This antibody will contribute to further identify and characterize intermediates of the amyloidogenic cascade. In addition, it will also be useful for screening amyloidogenic TTR mutations in patients with neuropathy of unknown cause, prior to precise molecular diagnosis using protein and/or DNA analysis.

Amino Acid Substitution↗
PubMed2000

Search for intermediate structures in transthyretin fibrillogenesis: soluble tetrameric Tyr78Phe TTR expresses a specific epitope present only in amyloid fibrils.

Familial Amyloidotic Polyneuropathy (FAP) is caused by the assembly of TTR into an insoluble beta-sheet. The TTR tetramer is thought to dissociate into monomeric intermediates and subsequently polymerise into the pathogenic amyloid form. The biochemical mechanism behind this transformation is unknown. We characterised intermediate TTR structures in the in vitro amyloidogenesis pathway by destabilising the AB loop through substitution of residue 78. Changes at this residue, should destabilise the TTR tetrameric fold, based on the known crystallographic structure of a Leu55Pro transthyretin variant. We generated a soluble tetrameric form of TTR that is recognised by a monoclonal antibody, previously reported to react only with highly amyloidogenic mutant proteins lacking the tetrameric native fold and with amyloid fibrils. BIAcore system analysis showed that Tyr78Phe had similar binding properties as synthetic fibrils. The affinity of this interaction was 10(7) M(-1). We suggest that the tetrameric structure of Tyr78Phe is altered due to the loosening of the AB loops of the tetramer, leading to a structure that might represent an early intermediate in the fibrillogenesis pathway.

Amino Acid Substitution↗
PubMed2000

A comparative analysis of 23 structures of the amyloidogenic protein transthyretin.

Self-assembly of the human plasma protein transthyretin (TTR) into unbranched insoluble amyloid fibrils occurs as a result of point mutations that destabilize the molecule, leading to conformational changes. The tertiary structure of native soluble TTR and many of its disease-causing mutants have been determined. Several independent studies by X-ray crystallography have suggested structural differences between TTR variants which are claimed to be of significance for amyloid formation. As these changes are minor and not consistent between the studies, we have compared all TTR structures available at the protein data bank including three wild-types, three non-amyloidogenic mutants, seven amyloidogenic mutants and nine complexes. The reference for this study is a new 1.5 A resolution structure of human wild-type TTR refined to an R-factor/R-free of 18.6 %/21.6 %. The present findings are discussed in the light of the previous structural studies of TTR variants, and show the reported structural differences to be non-significant.

Crystallography, X-Ray↗
PubMed2000

The beta-slip: a novel concept in transthyretin amyloidosis.

Transthyretin is a tetrameric plasma protein associated with two forms of amyloid disease. The structure of the highly amyloidogenic transthyretin triple mutant TTRG53S/E54D/L55S determined at 2.3 A resolution reveals a novel conformation: the beta-slip. A three-residue shift in beta strand D places Leu-58 at the position normally occupied by Leu-55 now mutated to serine. The beta-slip is best defined in two of the four monomers, where it makes new protein-protein interactions to an area normally involved in complex formation with retinol-binding protein. This interaction creates unique packing arrangements, where two protein helices combine to form a double helix in agreement with fiber diffraction and electron microscopy data. Based on these findings, a novel model for transthyretin amyloid formation is presented.

Amino Acid Substitution↗
PubMed2000

Analysis of magnetic resonance imaging acoustic noise generated by a 4.7 T experimental system.

High intensity acoustic noise is an undesirable side-effect in magnetic resonance imaging (MRI) that can cause discomfort and hearing loss in patients and may be an impediment in functional MRI (fMRI) studies of the auditory system. Experimental MRI systems with high magnetic field strengths may generate acoustic noise of higher sound pressure levels (SPLs) than conventional 1.0 and 1.5 T clinical systems. We measured the SPL and spectral content of the acoustic noise generated by the Bruker Biospect 47/40 4.7 T experimental MRI system during scanning sequences commonly used in animal testing. Each sequence generated acoustic noise of high SPL, rapid pulse rates, amplitude-modulated pulse envelopes and multi-peaked spectra. The rapid acquisition with enhancement sequence with a 0.25 mm slice thickness generated SPLs of up to 129 dB peak SPL and 130 dB (A). Fourier analysis of the spectral content of the acoustic noise generated by each MRI sequence showed a wide band of acoustic energy with spectral peaks from 0.2-5 kHz. The intense MRI acoustic impulse noise generated by the 4.7 T system may cause masking of stimuli used in fMRI of the auditory cortex, reduce the hearing acuity of experimental animals and present a risk for unprotected human ears.

Acoustics↗
PubMed2000

Naming speed, phonological awareness and the initial stage of learning to read.

Phonological awareness in kindergarten and rapid naming of objects in Grade 1 were used as predictors of reading achievement in Grade 1. Two reading measures were used: oral decoding of both words and pseudowords. They were found to be highly correlated. Both rapid naming and phonological awareness accounted for independent variance in reading achievement except for pseudoword reading, where rapid naming did not contribute significantly after the effect of phonemic awareness had been accounted for. Phonological awareness was the stronger predictor and a large part of the variance was shared between it and rapid naming. The rapid naming testing procedure functioned well and its potential as a research and diagnostic tool is discussed.

Analysis of Variance↗
PubMed1999

Exposure of cryptic epitopes on transthyretin only in amyloid and in amyloidogenic mutants.

The structural requirements for generation of amyloid from the plasma protein transthyretin (TTR) are not known, although it is assumed that TTR is partly misfolded in amyloid. In a search for structural determinants important for amyloid formation, we generated a TTR mutant with high potential to form amyloid. We demonstrated that the mutant represents an intermediate in a series of conformational changes leading to amyloid. Two monoclonal antibodies were generated against this mutant; each displayed affinity to ex vivo TTR and TTR mutants with amyloidogenic folding but not to wild-type TTR or mutants exhibiting the wild-type fold. Two cryptic epitopes were mapped to a domain of TTR, where most mutations associated with amyloidosis occur and which we propose is displaced at the initial phase of amyloid formation, opening up new surfaces necessary for autoaggregation of TTR monomers. The results provide direct biochemical evidence for structural changes in an amyloidogenic intermediate of TTR.

Amino Acid Sequence↗
PubMed1999

Unusual, high genetic diversity of Aleutian mink disease virus.

The genetic diversity of Aleutian mink disease virus (AMDV) was examined. Sequences obtained from 35 clinical samples were compared with five published sequences. An unusual, high genetic variability was revealed. Three phylogenetic subgroups of AMDV were identified, and the presence of more than one genotype at some farms was detected.

Aleutian Mink Disease↗
PubMed1999

Analysis of transthyretin amyloid fibrils from vitreous samples in familial amyloidotic polyneuropathy (Val30Met).

The aim of the present study was to analyze the forms of wild type and mutated monomeric transthyretin (Val30Met) in the amyloid fibrils of patients with familial amyloidotic polyneuropathy by electrospray ionization mass spectrometry (ESI-MS). The solubility of amyloid fibrils from the vitrectomized samples was examined to determine the appropriate solution for ESI-MS. ESI-MS analysis revealed that heterozygotic Val30Met amyloid fibrils contained 14.6 +/- 7.5% normal TTR. In all samples, 3 different types of variant ATTR could be identified: Full length ATTR, and -57, and -157 (or 156) Da from ATTR Val30Met were found. The two peaks showing -57, and -157 (or 156) Da from ATTR Val30Met corresponded to the -Gly, and -Gly-Pro sequences of ATTR Val30Met from the N-terminal. The results illustrate the heterogeneity of ATTR amyloid deposits and this method may be very useful for analyzing amyloid fibrils in ATTR related amyloidosis.

Aged↗
PubMed1998

Metaplastic transformation of urinary bladder epithelium: effect on mast cell recruitment, distribution, and phenotype expression.

Mucosal mast cells (MCs) are normally found in the connective tissue stroma but are redistributed into the epithelium in conditions associated with immunoglobulin E responses, such as allergic inflammation and nematode infections, as well as in interstitial cystitis, a condition of unknown etiology. The potential role of epithelium-derived factors in this response prompted this inquiry into growth and differentiation signaling in normal tissue as well as in tissues from five different metaplastic conditions of the urothelium (cystitic cystica, cystitis glandularis, colonic metaplasia, squamous cell metaplasia, and nephrogenic metaplasia). Expression of the two major human MC growth factors, stem cell factor (or kit ligand) and interleukin 6, was detected using immunohistochemistry. In the case of interleukin 6, its mRNA expression was also detected using in situ reverse transcription-polymerase chain reaction. Among the different metaplastic lesions, nephrogenic metaplasia was the only one associated with an abundance of MCs, which were distributed within or in close relationship to the epithelium. Unlike in the other types of metaplasia, the epithelium strongly co-expressed interleukin 6 and stem cell factor. The MCs expressed the stem cell factor receptor CD117 and exhibited a variable tryptase immunoreactivity, but lacked chymase. They also displayed a relative deficiency of granular glycosaminoglycan, as indicated by a lack of metachromasia, and were sensitive to strong aldehyde fixation. The findings suggest that the MC response in nephrogenic metaplasia may be the result of local epithelial stem cell factor/interleukin 6 expression.

Antigens, CD34↗
PubMed1998

Two-dimensional crystallization of Ca-ATPase by detergent removal.

By using Bio-Beads as a detergent-removing agent, it has been possible to produce detergent-depleted two-dimensional crystals of purified Ca-ATPase. The crystallinity and morphology of these different crystals were analyzed by electron microscopy under different experimental conditions. A lipid-to-protein ratio below 0.4 w/w was required for crystal formation. The rate of detergent removal critically affected crystal morphology, and large multilamellar crystalline sheets or wide unilamellar tubes were generated upon slow or fast detergent removal, respectively. Electron crystallographic analysis indicated unit cell parameters of a = 159 A, b = 54 A, and gamma = 90 degrees for both types of crystals, and projection maps at 15-A resolution were consistent with Ca-ATPase molecules alternately facing the two sides of the membrane. Crystal formation was also affected by the protein conformation. Indeed, tubular and multilamellar crystals both required the presence of Ca2+; the presence of ADP gave rise to another type of packing within the unit cell (a = 86 A, b = 77 A, and gamma = 90 degrees), while maintaining a bipolar orientation of the molecules within the bilayer. All of the results are discussed in terms of nucleation and crystal growth, and a model of crystallogenesis is proposed that may be generally true for asymmetrical proteins with a large hydrophilic cytoplasmic domain.

Animals↗
PubMed1998

Investigation into thiol conjugation of transthyretin in hereditary transthyretin amyloidosis.

BACKGROUND: For all forms of amyloidosis, the amyloid-generating mechanism is unknown. Familial amyloidotic polyneuropathy type I is caused by a variant transthyretin (TTR Met-30). As electrospray ionization mass spectrometry (ESI-MS) discloses both thiol-conjugated and -unconjugated forms of wild-type and variant TTR, we wanted to investigate the relationship between TTR conjugation and clinically overt amyloid disease. METHODS: Plasma from 35 individuals (12 symptomatic TTR Met-30 carriers, nine asymptomatic and 14 healthy control subjects) were analysed using ESI-MS. RESULTS: The total TTR concentration was significantly lower in symptomatic TTR Met-30 carriers than in control subjects. An increased percentage of conjugated TTR Met-30 was found in symptomatic carriers compared with asymptomatic, whereas the percentage conjugated wild-type TTR was similar for control subjects, asymptomatic and symptomatic TTR Met-30 carriers. CONCLUSION: The finding of a decreased ratio of unconjugated to conjugated TTR Met-30 in plasma samples from symptomatic TTR Met-30 carriers indicates that thiol conjugation of TTR could be involved in amyloid formation.

Adult↗
PubMed1997

Projection map of cytochrome b6 f complex at 8 A resolution.

The structure of the cytochrome b6 f complex has been investigated by electron microscopy and image analysis of thin three-dimensional crystals. Electron micrographs of negatively stained specimens were recorded and showed optical diffraction peaks to 10 A resolution. A projection map was calculated at 8 A resolution and showed the presence of cytochrome b6 f dimers. The extramembrane part of each monomer featured a C shape, with mean external diameter approximately of 53 A and an internal groove approximately 14 A long and approximately 9 A wide. Within each monomer, strong features were clearly resolved and tentatively attributed to some of the subunits of the cytochrome b6 f complex. The data are consistent with the Rieske iron-sulfur protein lying close to the monomer-monomer interface and the heme-bearing domain of cytochrome f far from it.

Animals↗