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M Karlsson

Publications and source records attributed to M Karlsson.

At least 55 records · Page 3Linked to original sources
PubMed2001

Comparison of calculated, measured and self-assessed intelligibility of speech in noise for hearing-aid users.

The Speech Intelligibility Index (SII) was used along with paired-comparison judgements and speech recognition scores to compare the speech intelligibility provided by two hearing-aid frequency responses in two different background noises. The purpose was to validate an SII-based procedure. Test subjects were 26 hearing-aid users representing a wide range of hearing loss configurations. One hearing-aid setting was in close agreement with the NAL-R prescription, whereas the other setting was achieved by reducing the high-frequency gain by about 10 dB compared to NAL-R. There were good overall agreements between results of the three methods. Average speech recognition scores were about 4 percentage points higher for the NAL-R frequency response, which also was subjectively judged as significantly better in terms of speech intelligibility. The SII based procedure was found to be suitable for comparing hearing-aid characteristics within subjects.

Aged↗
PubMed2001

Predicted and measured speech recognition performance in noise with linear amplification.

OBJECTIVE: The purpose of this study was to investigate the applicability of the Speech Intelligibility Index (SII) in hearing aid fitting. It was hypothesized that estimated speech intelligibility, based on the SII, could be a more reliable measure than real speech recognition results for comparing hearing aid characteristics. DESIGN: The test subjects were 29 elderly persons (66 to 80 yr) with mild-to-moderate hearing loss, who were using monaurally fitted linear hearing aids. They were selected from the files at Sahlgrenska hearing clinic. Speech recognition scores were obtained at fixed speech-to-noise ratios with Phonemically Balanced (PB) words in speech-weighted noise and in low-frequency noise. A Just-Follow-Conversation (JFC) test was performed with connected speech presented in the same background noises. The subjects were tested without hearing aid and with their hearing aids set at three different frequency responses. Predicted speech recognition scores were calculated for each condition based on the SII, complemented with a correction for sensorineural hearing impairment. The calculations involved speech and noise spectra, pure tone thresholds and insertion gain responses. RESULTS: For each condition, the measured speech recognition scores were, on average, well predicted by the calculated scores. The intra-individual standard deviation of the predicted scores was estimated to be about one percent unit. The group results of the JFC test were in agreement with the word recognition results for the aided conditions, but a floor effect was observed for the unaided conditions. CONCLUSIONS: Speech intelligibility prediction based on the modified SII is a valid estimate of speech recognition performance of hearing-impaired persons with mild-to-moderate hearing loss. Estimated intelligibility based on the SII is more reliable than actually measured speech recognition performance, for comparing amplification conditions within subjects.

Aged↗
PubMed2001

The complete set of genes encoding major intrinsic proteins in Arabidopsis provides a framework for a new nomenclature for major intrinsic proteins in plants.

Major intrinsic proteins (MIPs) facilitate the passive transport of small polar molecules across membranes. MIPs constitute a very old family of proteins and different forms have been found in all kinds of living organisms, including bacteria, fungi, animals, and plants. In the genomic sequence of Arabidopsis, we have identified 35 different MIP-encoding genes. Based on sequence similarity, these 35 proteins are divided into four different subfamilies: plasma membrane intrinsic proteins, tonoplast intrinsic proteins, NOD26-like intrinsic proteins also called NOD26-like MIPs, and the recently discovered small basic intrinsic proteins. In Arabidopsis, there are 13 plasma membrane intrinsic proteins, 10 tonoplast intrinsic proteins, nine NOD26-like intrinsic proteins, and three small basic intrinsic proteins. The gene structure in general is conserved within each subfamily, although there is a tendency to lose introns. Based on phylogenetic comparisons of maize (Zea mays) and Arabidopsis MIPs (AtMIPs), it is argued that the general intron patterns in the subfamilies were formed before the split of monocotyledons and dicotyledons. Although the gene structure is unique for each subfamily, there is a common pattern in how transmembrane helices are encoded on the exons in three of the subfamilies. The nomenclature for plant MIPs varies widely between different species but also between subfamilies in the same species. Based on the phylogeny of all AtMIPs, a new and more consistent nomenclature is proposed. The complete set of AtMIPs, together with the new nomenclature, will facilitate the isolation, classification, and labeling of plant MIPs from other species.

Algorithms↗
PubMed2001

A novel superoxide dismutase with a high isoelectric point in higher plants. expression, regulation, and protein localization.

Several isoforms of superoxide dismutase (SOD) with a high isoelectric point (pI) have been identified by isoelectric focusing chromatography in protein extracts from Scots pine (Pinus sylvestris) needles. One of these isoforms, a CuZn-SOD with a pI of about 10 and thus denoted hipI-SOD, has been isolated and purified to apparent homogeneity. A cDNA encoding the hipI-SOD protein was cloned and sequenced. Northern hybridization of mRNA isolated from different organs and tissues showed that hipI-SOD has a markedly different pattern of expression compared with chloroplastic and cytosolic SOD. Furthermore, the transcript levels of hipI-SOD and cytosolic SOD were found to respond differently to mechanical wounding, treatment with oxidized glutathione, paraquat, and ozone. Immunogold electron microscopy localized the hipI-SOD in the plasma membrane of sieve cells and the Golgi apparatus of albuminous cells. Moreover, high protein density was also detected in extracellular spaces such as secondary cell wall thickenings of the xylem and sclerenchyma and in intercellular spaces of parenchyma cells.

Adaptation, Physiological↗
PubMed2001

Three dimensional flow in the human left atrium.

BACKGROUND: Abnormal flow patterns in the left atrium in atrial fibrillation or mitral stenosis are associated with an increased risk of thrombosis and systemic embolisation; the characteristics of normal atrial flow that avoid stasis have not been well defined. OBJECTIVES: To present a three dimensional particle trace visualisation of normal left atrial flow in vivo, constructed from flow velocities in three dimensional space. METHODS: Particle trace visualisation of time resolved three dimensional magnetic resonance imaging velocity measurements was used to provide a display of intracardiac flow without the limitations of angle sensitivity or restriction to imaging planes. Global flow patterns of the left atrium were studied in 11 healthy volunteers. RESULTS: In all subjects vortical flow was observed in the atrium during systole and diastolic diastasis (mean (SD) duration of systolic vortex, 280 (77) ms; and of diastolic vortex, 256 (118) ms). The volume incorporated and recirculated within the vortices originated predominantly from the left pulmonary veins. Inflow from the right veins passed along the vortex periphery, constrained between the vortex and the atrial wall. CONCLUSIONS: Global left atrial flow in the normal human heart comprises consistent patterns specific to the phase of the cardiac cycle. Separate paths of left and right pulmonary venous inflow and vortex formation may have beneficial effects in avoiding left atrial stasis in the normal subject in sinus rhythm.

Adult↗
PubMed2001

Nerve growth factor is expressed by postmitotic avian retinal horizontal cells and supports their survival during development in an autocrine mode of action.

Cell death in the developing retina is regulated, but so far little is known about what factors regulate the cell death. Several neurotrophic factors and receptors, including the neurotrophins and Trk receptors, are expressed during the critical time. We have studied the developing avian retina with respect to the role of nerve growth factor (NGF) in these processes. Our starting point for the work was that NGF and its receptor TrkA are expressed in a partially overlapping pattern in the inner nuclear layer of the developing retina. Our results show that TrkA and NGF-expressing cells are postmitotic. The first NGF-expressing cells were found on the vitreal side of the central region of E5.5-E6 retina. This pattern changed and NGF-expressing cells identified as horizontal cells were later confined to the external inner nuclear layer. We show that these horizontal cells co-express TrkA and NGF, unlike a subpopulation of amacrine cells that only expresses TrkA. In contrast to the horizontal cells, which survive, the majority of the TrkA-expressing amacrine cells die during a period of cell death in the inner nuclear layer. Intraocular injections of NGF protein rescued the dying amacrine cells and injection of antisense oligonucleotides for NGF that block its synthesis, caused death among the TrkA-expressing horizontal cells, which normally would survive. Our results suggest that NGF supports the survival of TrkA expressing avian horizontal cells in an autocrine mode of action in the retina of E10-E12 chicks. The cells co-express TrkA and NGF and the role for NGF is to maintain the TrkA-expressing horizontal cells. The TrkA-expressing amacrine cells are not supported by NGF and subsequently die. In addition to the effect on survival, our results suggest that NGF plays a role in horizontal cell plasticity.

Animals↗
PubMed2001

Prognostic importance of DNA ploidy and p53 in early stages of epithelial ovarian carcinoma.

Patients with early stages (FIGO stages IA-IIC) of ovarian cancer continue to experience tumor relapses and they succumb due to their disease after seemingly adequate adjuvant therapy. In a series of 113 patients treated with adjuvant radiotherapy 4-6 weeks after primary surgery, the DNA content and p53 status of the tumors were studied and related to other known prognostic factors (age, FIGO stage, histopathologic type, and tumor grade). The DNA analyses were done by flow cytometry and p53 expression was studied by immunohistochemistry on formalin-fixed and paraffin-embedded tissue. DNA analyses of 103 tumors could be made and the p53 status was determined in 106 cases. Univariate analyses showed that both p53-positivity and aneuploidy of the ovarian tumors were strongly associated with tumor grade. There was also a strong association between p53 expression of the tumors and DNA aneuploidy (DNA index >1.10 and S-phase fraction >11.5%). P53-positivity and tumor grade were the only significant factors for the risk of tumor recurrence. DNA and p53 status alone were not adequate predictive factors to identify clinically relevant subgroups of patients who would benefit from adjuvant postoperative therapy. Tumor grade remains the most important prognostic factor with regard to the risk of tumor recurrence and the cancer-specific survival rate in early stage ovarian carcinoma. Overexpression of p53 also increases the risk of tumor recurrence.

Adenocarcinoma, Clear Cell↗
PubMed2001

Susceptibility to pleuromutilins in Brachyspira (Serpulina) hyodysenteriae.

The pleuromutilins are the only antimicrobial agents with sufficient minimum inhibitory concentration (MIC) values left to treat swine dysentery in Sweden. Other antimicrobials are either not approved for use against swine dysentery or only partly active against Brachyspira hyodysenteriae. To date, in Sweden two pleuromutilins, tiamulin and valnemulin, are authorized for use in pigs. This study includes a comparison between MICs of tiamulin and valnemulin for Swedish field isolates of B. hyodysenteriae, as determined by broth dilution. For different isolates the MIC of tiamulin was between 0 and 8 times higher than that of valnemulin. No resistance to pleuromutilins was recorded (tiamulin MIC range 0.031-2 microg/ml, valnemulin MIC range < or =0.016-1 microg/ml). In vitro development of tiamulin resistance was also studied. Two B. hyodysenteriae and two B. pilosicoli strains became resistant to tiamulin following reiterated passages on agar containing tiamulin in increasing concentrations. The resistance emerged slowly and three of the strains that went through more than 60 passages increased their tiamulin MICs from 0.031-0.25 to more than 128 microg/ml. The tiamulin MIC for one B. hyodysenteriae strain that went through 29 passages increased from 0.0125 to 4 microg/ml. One B. pilosicoli strain developed cross-resistance to valnemulin; the MIC increased from 0.25 to more than 64 microg/ml. The valnemulin MIC for one B. hyodysenteriae strain increased from 0.031 microg/ml to 32 microg/ml. Valnemulin MIC was not determined for the B. hyodysenteriae strain that only went through 29 passages. The valnemulin MIC of the other B. pilosicoli strain increased from 0.031 to 4 microg/ml.

Animals↗
PubMed2000

Cholesterol depletion disrupts caveolae and insulin receptor signaling for metabolic control via insulin receptor substrate-1, but not for mitogen-activated protein kinase control.

Insulin exerts its cellular control through receptor binding in caveolae in plasmalemma of target cells (Gustavsson, J., Parpal, S., Karlsson, M., Ramsing, C., Thorn, H., Borg, M., Lindroth, M., Peterson, K. H., Magnusson, K.-E., and Strålfors, P. (1999) FASEB. J. 13, 1961-1971). We now report that a progressive cholesterol depletion of 3T3-L1 adipocytes with beta-cyclodextrin gradually destroyed caveolae structures and concomitantly attenuated insulin stimulation of glucose transport, in effect making cells insulin-resistant. Insulin access to or affinity for the insulin receptor on rat adipocytes was not affected as determined by (125)I-insulin binding. By immunoblotting of plasma membranes, total amount of insulin receptor and of caveolin remained unchanged. Receptor autophosphorylation in response to insulin was not affected by cholesterol depletion. Insulin treatment of isolated caveolae preparations increased autophosphorylation of receptor before and following cholesterol depletion. Insulin-increased tyrosine phosphorylation of an immediate downstream signal transducer, insulin receptor substrate-1, and activation of the further downstream protein kinase B were inhibited. In contrast, insulin signaling to mitogenic control as determined by control of the extracellular signal-related kinases 1/2, mitogen-activated protein kinase pathway was not affected. Insulin did not control Shc phosphorylation, and Shc did not control extracellular signal-related kinases 1/2, whereas cholesterol depletion constitutively phosphorylated Shc. In conclusion, caveolae are critical for propagating the insulin receptor signal to downstream targets and have the potential for sorting signal transduction for metabolic and mitogenic effects.

3T3 Cells↗
PubMed2000

Electroinjection of colloid particles and biopolymers into single unilamellar liposomes and cells for bioanalytical applications.

A combined electroporation and pressure-driven microinjection method for efficient loading of biopolymers and colloidal particles into single-cell-sized unilamellar liposomes was developed. Single liposomes were positioned between a approximately 2-microm tip diameter solute-filled glass micropipet, equipped with a Pt electrode, and a 5-microm-diameter carbon fiber electrode. A transient, 1-10 ms, rectangular waveform dc voltage pulse (10-40 V/cm) was applied between the electrodes, thus focusing the electric field over the liposome. Dielectric membrane breakdown induced by the applied voltage pulse caused the micropipet tip to enter the liposome and a small volume (typically 50-500 x 10(-15) L) of fluorescein, YOYO-intercalated T7-phage DNA, 100-nm-diameter unilamellar liposomes, or fluorescent latex spheres could be injected into the intraliposomal compartment. We also demonstrate initiation of a chemical intercalation reaction between T2-phage DNA and YOYO-1 by dual injection into a single giant unilamellar liposome. The method was also successfully applied for loading of single cultured cells.

Biopolymers↗
PubMed2000

Binding and detection of glycosaminoglycans immobilized on membranes treated with cationic detergents.

Immobilization of molecules on surfaces is used for preparative, quantitative, and qualitative studies. Glycosaminoglycans (GAGs) are strongly hydrophilic and negatively charged molecules that do not bind well to either polystyrene surfaces or hydrophobic blotting membranes. Hydrophobic membranes were derivatized with cationic detergents to become hydrophilic and positively charged. The ability of the polyvinylidene fluoride and nitrocellulose membranes to retain GAGs increased up to 12.8 microg per spot in the dot blot assay when the membrane was treated with a cationic detergent. Immobilized GAGs were stained with alcian blue, and the staining intensity was quantitated by scanning and densitometry. The derivatized membranes were used for solid-phase extraction of GAGs in blood plasma, urine, or cerebrospinal fluid. The detection sensitivity was equal for different types of GAGs but there was a slight negative interference from fibrinogen in blood plasma. The immobilized GAGs could also be released from the membrane using a nonionic detergent at high ionic strength. Recovery of different proteoglycan populations, separated by electrophoresis and detected by reversible staining with toluidine blue, was 70-100%.

Alcian Blue↗
PubMed2000

Application of the JKR Method to the Measurement of Adhesion to Langmuir-Blodgett Cellulose Surfaces.

The JKR method has been applied for studying adhesion between poly(dimethylsiloxane) (PDMS) caps and Langmuir-Blodgett cellulose surfaces including the substrate, hydrophobized mica, and two flat mineral surfaces, bare mica and glass. The self-adhesion of PDMS caps and oxidized PDMS caps are included as a reference to compare with literature data. The results of the measurements have been compared with previous studies using the surface force apparatus and similar systems. A satisfactory agreement is obtained for simple systems showing no, or very limited, hysteresis between loading and unloading curves. In several cases, however, a large hysteresis is found between loading and unloading curves, with a larger adhesion measured from the pull-off force than from the JKR-curve determined on loading. This is, for instance, the case for PDMS against cellulose. The situation is analogous to that found in wetting studies showing a large hysteresis between advancing and receding contact angles. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

The antennapedia peptide penetratin translocates across lipid bilayers - the first direct observation.

The potential use of polypeptides and oligonucleotides for therapeutical purposes has been questioned because of their inherently poor cellular uptake. However, the 16-mer oligopeptide penetratin, derived from the homeodomain of Antennapedia, has been reported to enter cells readily via a non-endocytotic and receptor- and transporter-independent pathway, even when conjugated to large hydrophilic molecules. We here present the first study where penetratin is shown to traverse a pure lipid bilayer. The results support the idea that the uptake mechanism involves only the interaction of the peptide with the membrane lipids. Furthermore, we conclude that the translocation does not involve pore formation.

Animals↗
PubMed2000

The role of aquaporins in cellular and whole plant water balance.

Aquaporins are water channel proteins belonging to the major intrinsic protein (MIP) superfamily of membrane proteins. More than 150 MIPs have been identified in organisms ranging from bacteria to animals and plants. In plants, aquaporins are present in the plasma membrane and in the vacuolar membrane where they are abundant constituents. Functional studies of aquaporins have hitherto mainly been performed by heterologous expression in Xenopus oocytes. A main issue is now to understand their role in the plant, where they are likely to be important both at the cellular and at the whole plant level. Plants contain a large number of aquaporin isoforms with distinct cell type- and tissue-specific expression patterns. Some of these are constitutively expressed, whereas the expression of others is regulated in response to environmental factors, such as drought and salinity. At the protein level, regulation of water transport activity by phosphorylation has been reported for some aquaporins.

Amino Acid Sequence↗
PubMed2000

Bonding and reactivity at oxide mineral surfaces from model aqueous complexes

The kinetic stability of oxide surfaces affects a broad range of physical phenomena, including mineral dissolution and sorption reactions, stable-isotope fractionation, and catalyst support degradation. Our knowledge of the rates of these processes derives mostly from the rates of net mass transfer between the bulk solid and fluid phases. But from such data it is difficult to determine rates of elementary steps that are needed to test theoretical models. Here we determine the rates of oxygen exchange between an aqueous fluid and specific sites on the 'Al13' polyoxocation--AlO4Al12(OH)24(H2O)12(7+)--the structure of which closely resembles the surfaces of some Al-(hydr)oxide minerals in soils and catalyst supports. Extrapolation of these data to 298 K (and near pH 5.3) yields half-lives for oxygen on the complex that range from approximately 0.6 milliseconds for bound water to 41 seconds and 13 hours for the two distinct, but structurally similar, bridging hydroxyls. This surprisingly large range of labilities (approximately 10(7)) indicates that reactivity is very sensitive to molecular structure. Moreover, these results indicate that well chosen aqueous complexes provide important information to relate bonding to reactivity at mineral surfaces.

Journal Article↗
PubMed2000

Down-regulation of cyclic-nucleotide phosphodiesterase 3B in 3T3-L1 adipocytes induced by tumour necrosis factor alpha and cAMP.

We have used murine 3T3-L1 cells, which differentiate in culture and acquire morphological and biochemical features of mature adipocytes, as a model for studying the expression of cyclic-nucleotide phosphodiesterase (PDE) 3B activity, protein and mRNA during differentiation and during long-term treatment of the cells with tumour necrosis factor alpha (TNF-alpha), a cytokine associated with insulin resistance, and a cAMP analogue, N(6),2'-O-dibutyryl cAMP (dbcAMP). PDE3B activity, protein and mRNA could be detected 4 days after the initiation of differentiation of 3T3-L1 preadipocytes. Treatment of 3T3-L1 adipocytes with 10 ng/ml TNF-alpha for 24 h produced a maximal (50%) decrease in PDE3B activity, protein and mRNA, which was well correlated with both activation of protein kinase A (PKA) and stimulation of lipolysis, presumably reflecting an increase in intracellular cAMP concentration. To investigate the effect of cAMP on PDE3B we treated 3T3-L1 adipocytes with dbcAMP. After 4 h with 0.5 mM dbcAMP, PDE3B activity was decreased by 80%, which was also correlated with a decrease in PDE3B protein and mRNA. This effect was abolished in the presence of N-[2-(bromocinnamylamino)ethyl]-5-isoquinolinesulphonamide] (H-89), a specific PKA inhibitor. We conclude that the lipolytic effect of TNF-alpha involves the down-regulation of PDE3B, which is associated with increased activation of PKA, presumably owing to increased levels of cAMP. In addition, the PKA activation induced by dbcAMP resulted in the down-regulation of PDE3B. These results, which suggest that PDE3B is a novel target for long-term regulation by TNF-alpha and cAMP, could contribute to the understanding of the mechanisms of insulin resistance.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Correction for acceleration-induced displacement artifacts in phase contrast imaging.

The acceleration-induced displacement artifact impairs the accuracy of MR velocity measurements. This study proposes a post processing method for correction of this artifact. Velocity measurements were performed in a flow phantom containing a constriction. Velocity curves were obtained from streamlines parallel to the frequency, phase, and slice directions, respectively. The acceleration-induced displacement artifact was most prominent when the frequency encoding direction was aligned with the flow direction. After correction, velocity assignment improved and a more accurate description of the flow was obtained. In vivo measurements were performed in the aorta in a patient with a repaired aortic coarctation. The correction method was applied to velocity data along a streamline parallel to the frequency encoding direction. The result after correction was a new location of the peak velocity and improved estimates of the velocity gradients.

Adult↗