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Biomedical subjects

L Ericsson

Publications and source records attributed to L Ericsson.

14 recordsLinked to original sources
PubMed2002

Algorithms for suppressing ultrasonic backscattering from material structure.

In pulse-echo ultrasonic inspection the backscattering from the material structure appears in the received ultrasonic images as clutter, often referred to as grain noise, which impairs the inspection results. A toolbox including algorithms for suppressing ultrasonic clutter is presented in the paper. Several processing algorithms capable of suppressing grain noise have been proposed, of which the split spectrum processing (SSP) probably is the most renowned. The classical SSP technique applies a filter bank to some frequency band that has to be precisely known in advance, to obtain a set of narrow-band signals that are tested for mutual correlation using some statistical operation. A number of SSP algorithms with different statistical operations are included in the toolbox. A completely different approach is to use explicit statistical models of grain noise and defects and to design an optimal filter based on those models. A simple such algorithm, based on noncoherent detection (NCD) known from communications, is also included in the toolbox. The toolbox, implemented in Matlab, is provided with a user-friendly graphical interface facilitating comparison of the algorithms.

Journal Article↗
PubMed1993

Structural studies of the extracellular polysaccharide from Butyrivibrio fibrisolvens strain X6C61.

The capsular polysaccharide from Butyrivibrio fibrisolvens strain X6C61 has been investigated using NMR spectroscopy, mass spectrometry, methylation analysis, and partial acid hydrolysis as the main methods. The polysaccharide is composed of hexasaccharide repeating units having the following structure. [formula: see text] The polysaccharide also contains O-acetyl groups, of which approximately 70% are substituted to O-3 of the beta-D-Glc pA residue.

Bacterial Capsules↗
PubMed1993

Safe pulmonary preservation for 12 hours with low-potassium-dextran solution.

The function of porcine left lung allografts was studied after perfusion with (150 mL/kg) and storage for 12 hours in a 4 degrees to 6 degrees C low-potassium-dextran solution (Perfadex; Kabi Pharmacia AB, Uppsala, Sweden). After a left lung transplantation, an artificial lung in the form of venoarterial extracorporeal membrane oxygenation was established. The artificial lung has a "biological" heparin-coated surface (Carmeda AB, Stockholm, Sweden), and there is no need for systemic anticoagulation. Immediately thereafter, pneumonectomy of the normal right lung was done. All the animals were weaned from the artificial lung within 1 hour after the pneumonectomy. Six animals were followed up for 24 hours. They were in good condition throughout the 24-hour observation period with arterial oxygen tensions around 200 mm Hg (inspired oxygen fraction = 0.4) and arterial carbon dioxide tensions around 40 mm Hg. This study demonstrates a reliable method for continuous evaluation of the function of a transplanted lung immediately after transplantation and over the ensuing postoperative period. Safe 12-hour lung preservation can be obtained with the low-potassium-dextran solution Perfadex.

Animals↗
PubMed1992

Human T-cell mitogen-activated protein kinase kinases are related to yeast signal transduction kinases.

Mitogen-activated protein (MAP) kinase kinases, intermediates in a growth factor-stimulated protein kinase cascade, are dual specificity protein kinases that specifically phosphorylate and activate MAP kinases in response to extracellular signals. Here, we report the cloning of two forms of cDNA that encode this protein from human T-cells. MKK1a encodes a protein with predicted molecular size of 43,439 Da. Overexpression of this clone in COS cells led to elevated levels of protein and phorbol ester-stimulated MAP kinase kinase activity, confirming that MKK1a encodes the predicted protein. MKK1b, which appears to be an alternatively spliced form of the MKK1a gene, encodes a protein with predicted molecular size of 40,745 Da. Northern analysis revealed that the MKK1 cDNA hybridizes with a single 2.6-kilobase mRNA species in all human tissues examined. Sequence comparison shows homology to a group of yeast kinases that participate in signal transduction and to subdomain XI of other dual specificity kinase.

Amino Acid Sequence↗
PubMed1991

Microtubule-associated protein 2 kinases, ERK1 and ERK2, undergo autophosphorylation on both tyrosine and threonine residues: implications for their mechanism of activation.

Microtubule-associated protein 2 kinase (MAP kinase), which exists in several forms, is a protein serine/threonine kinase that participates in a growth factor-activated protein kinase cascade in which it activates a ribosomal protein S6 kinase (pp90rsk) while being regulated itself by a cytoplasmic factor (MAP kinase activator). Experiments with recombinant MAP kinase, ERK2, purified from Escherichia coli in a nonactivated form revealed a self-catalyzed phosphate incorporation into both tyrosine and threonine residues. Another MAP kinase, ERK1, purified from insulin-stimulated cells also autophosphorylated on tyrosine and threonine residues. Autophosphorylation of ERK2 correlated with its autoactivation, although both autophosphorylation and autoactivation were slow compared to that occurring in the presence of MAP kinase activator. Therefore, we propose that autophosphorylation is probably involved in the MAP kinase activation process in vitro, but it may not be sufficient for full activation. The specificity toward tyrosine and threonine residues indicates that the MAP kinases ERK1 and ERK2 are members of a group of kinases with specificity for tyrosine as well as serine and threonine residues.

Amino Acid Sequence↗
PubMed1987

Proteolytic dimers of porcine muscle lactate dehydrogenase: characterization, folding, and reconstitution of the truncated and nicked polypeptide chain.

Lactate dehydrogenase from porcine skeletal muscle is a "dimer of dimers" that is stabilized in its tetrameric state by an N-terminal "arm" of approximately 20 amino acid residues. Due to the low dissociation constant of the tetramer, the dimer is inaccessible to direct analysis. Limited proteolysis during reconstitution (after dissociation at pH 2.3) yields stable "dimers". As suggested by affinity chromatography, these inactive dimers contain the dinucleotide fold of native LDH. In the presence of structure-making ions, approximately 40% activity is restored in the dimeric state [Girg, R., Jaenicke, R., & Rudolph, R. (1983) Biochem. Int. 7, 443-444]. The cleavage yields about equal amounts of three fragments, F 34, F 21, and F 14 (Mr 33.5K, 21.4K, and 13.5K, respectively). F 34 represents the intact chain lacking the N-terminal 10-11 amino acid residues; its C-terminus is heterogeneous, varying in the range between residues 326 +/- 5. F 21 contains residues 11/12 to 200 +/- 3; F 14 is a mixture of three subfragments: residues 11/12 to approximately 133, 38 to approximately 163, and 208 to approximately 327. After solubilization in 6 M guanidine hydrochloride, F 34 can be reconstituted to partially active dimers. Reactivation is determined by slow subunit refolding with subsequent diffusion-controlled dimerization, in accordance with the monomer-dimer transition in the reconstitution mechanism of the intact tetramer. Reconstitution of F 21 and F 14 is concentration dependent and leads to partially active "nicked dimers", indicating that separate domains are able to reassociate correctly to yield the native subunit arrangement.

Amino Acid Sequence↗
PubMed1985

Wound-induced proteinase inhibitors from tomato leaves. I. The cDNA-deduced primary structure of pre-inhibitor I and its post-translational processing.

A cDNA containing the coding region for the complete amino acid sequence of wound-induced proteinase Inhibitor I from tomato leaves was constructed in the plasmid pUC9 and characterized. The open reading frame codes for a protein of 111 amino acids. This deduced amino acid sequence revealed the presence of a 42-amino acid N-terminal sequence that is not found in the native protein. This sequence appears to contain a 23-amino acid segment typical of a signal sequence followed by a 19-amino acid sequence containing 9 charged amino acids. The 42-amino acid sequence is apparently lost during maturation to the native Inhibitor I and represents 38% of the translated protein. The Inhibitor I amino acid sequence contains 71% identity with potato tuber Inhibitor I sequence and 35% identity with an inhibitor from the leech.

Amino Acid Sequence↗
PubMed1978

Amino acid sequence of the diazooxonorleucine binding site of Acinetobacter and Pseudomonas 7A glutaminase--asparaginase enzymes.

Acinetobactor glutaminase-asparaginase was treated with [6-14C]diazo-5-oxonorleucine, reduced with sodium borohydride, and cleaved with cyanogen bromide. Radioactivity was present only in a 96-residue-N-terminal peptide which eluted as the second peptide peak on Sephadex G-50. Radioactivity was released with the threonine in position 12 during automatic sequencing of this peptide. The amino acid sequence of a 60-residue tn-terminal segment and a 16-residue C-terminal segment of this peptide was determined. Pseudomonas 7 A glutaminase-asparaginase was treated with [6-14C]diazo-5-oxonorleucine and reduced with sodium borohydride. Radioactivity was released with the threonine in residue 20 during automatic sequencing of the whole enzyme. Analysis of 26 N-terminal residues showed that an 8-residue segment containing the radioactive threonine was identical with that in Acinetobacter glutaminase-asparaginase and in Escherichia coli asparaginase. Additional identical residues were noted in the N-terminal regions of these enzymes.

Acinetobacter↗