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Biomedical subjects

S Rosén

Publications and source records attributed to S Rosén.

At least 19 recordsLinked to original sources
PubMed2006

Dissociative recombination of ammonia clusters studied by storage ring experiments.

Dissociative recombination of ammonia cluster ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for dissociative recombination of H+(NH3)2, H+(NH3)3, D+(ND3)2, and D+(ND3)3 in the collision energy range of 0.001-27 eV are reported, and thermal rate coefficients for the temperature interval from 10 to 1000 K are calculated from the experimental data and compared with earlier results. The fragmentation patterns for the two ions H+(NH3)2 and D+(ND3)2 show no clear isotope effect. Dissociative recombination of X+(NX3)2 (X=H or D) is dominated by the product channels 2NX3+X [0.95+/-0.02 for H+(NH3)2 and 1.00+/-0.02 for D+(ND3)2]. Dissociative recombination of D+(ND3)3 is dominated by the channels yielding three N-containing fragments (0.95+/-0.05).

Journal Article↗
PubMed2005

Chromogenic methods in coagulation diagnostics.

Chromogenic peptide substrates were developed more than 30 years ago. Although the use of chromogenic substrate methods in coagulation and fibrinolysis diagnostics was not as rapidly implemented as initially believed, they are now well established for several analytes such as antithrombin, FVIII, protein C, plasminogen, plasmin inhibitor, heparins, and pentasaccharides. The advent of direct thrombin and factor Xa inhibitors has stimulated the development of new, specific chromogenic methods and these may find their way into routine use if these new drug candidates will prove to be valid replacements for coumarin derivatives. A large number of chromogenic research methods for other analytes were developed, too. The current interest in global chromogenic methods for thrombin generation and the protein C pathway may turn out as clinically important and thus enter into routine use.

Antithrombins↗
PubMed2004

Dissociative recombination of NH4+ and ND4+ ions: storage ring experiments and ab initio molecular dynamics.

The dissociative recombination (DR) process of NH4+ and ND4+ molecular ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for DR of NH4+ and ND4+ in the collision energy range 0.001-1 eV are reported, and thermal rate coefficients for the temperature interval from 10 to 2000 K are calculated from the experimental data. The absolute cross section for NH4+ agrees well with earlier work and is about a factor of 2 larger than the cross section for ND4+. The dissociative recombination of NH4+ is dominated by the product channels NH3+H (0.85+/-0.04) and NH2+2H (0.13+/-0.01), while the DR of ND4+ mainly results in ND3+D (0.94+/-0.03). Ab initio direct dynamics simulations, based on the assumption that the dissociation dynamics is governed by the neutral ground-state potential energy surface, suggest that the primary product formed in the DR process is NH3+H. The ejection of the H atom is direct and leaves the NH3 molecule highly vibrationally excited. A fraction of the excited ammonia molecules may subsequently undergo secondary fragmentation forming NH2+H. It is concluded that the model results are consistent with gross features of the experimental results, including the sensitivity of the branching ratio for the three-body channel NH2+2H to isotopic exchange.

Journal Article↗
PubMed2003

The ScanDeNi process could turn an existing under-performing activated sludge plant into an asset.

With tightening up of effluent discharge standards from wastewater treatment facilities, many plants are facing costly augmentations and in many cases completely new plants will have to be constructed. The ScanDeNi process was developed in Sweden for increased nitrogen removal at the Västerås Sewage Treatment Plant (STP), 125,000 p.e. near Stockholm, and can be described as a modified contact stabilisation process with pre-denitrification and a selector stage for nitrification. The STP was upgraded at a cost of some 25 Mill. SEK (2.5 Mill. USD). It has been successfully in operation since 1998, exceeding all expectations. The process is showing the following major advantages. 25-35% less volume for the same Sludge Retention Time (SRT) and secondary sedimentation sludge load, compared to conventional pre-denitrification; or a 25-35% higher load can be applied within the same volume with the same removal efficiencies. The selector mechanism appears to be not limited to the nitrifying bacteria alone. Other microorganisms appear to be responsible for the reduction of surface active matter from the return activated sludge (RAS), as well as in the reject stream from sludge dewatering, resulting in an increase in alpha-values of approximately 50%. Due to the high alpha-values less aeration is required, resulting in significant operating cost savings. 'Automatic' creation of anaerobic conditions, enabling biological phosphorus removal. Whilst rarely a concern in warmer climates, BNR plants in cold climates in winter often lose their capacity to nitrify. The Västerås STP has consistently maintained excellent effluent quality even with effluent temperatures as low as 7 degrees C, and at an SRT of some 7-9 days, proving the effectiveness of the nitrifier selector. The ScanDeNi process could offer excellent effluent discharge standards (T-N < 10 mg/L, T-P < 0.5 mg/L) in smaller tank volumes and at a significantly lower operating cost, compared to conventional pre-denitrification systems.

Automation↗
PubMed2000

Dynamics of three-body breakup in dissociative recombination: H(2)O(+).

To better understand the propensity for the three-body breakup in dissociative recombination (DR) of dihydrides ( H(3)(+), NH(2)(+), CH(2)(+), and H(2)O(+)), we undertook a study of the dynamics of this process. A study of DR of H(2)O(+) to give O + H + H was carried out at the CRYRING Heavy-Ion Storage Ring in Stockholm. With the stored beam energy of 4.5 MeV, we separated the O signal from the H signals with a differential absorber, thus reducing the problem to a sum of two two-body problems. Results included (1) the ratio of O((3)P) to O((1)D) product, (2) the distribution of recoil-kinetic energy between the two hydrogen atoms, (3) the angular distribution between the hydrogen atoms in the O((3)P) channel and in the O((1)D) channel.

Journal Article↗
PubMed1999

The Aspergillus nidulans sfaD gene encodes a G protein beta subunit that is required for normal growth and repression of sporulation.

flbA encodes an Aspergillus nidulans RGS (regulator of G protein signaling) domain protein that antagonizes FadA (G(i)alpha-subunit of heterotrimeric G protein)-mediated growth signaling to allow asexual development. We previously defined and characterized five suppressors of flbA (sfa) loss-of-function mutations and showed that one suppressor (sfaB) resulted from a novel dominant-negative allele of fadA. In this report we show that a second suppressor gene (sfaD) is predicted to encode the beta subunit of a heterotrimeric G protein. Deletion of sfaD suppressed all defects resulting from complete loss-of-flbA function mutations, caused a hyperactive sporulation phenotype and severely reduced vegetative growth. However, the sfaD deletion could not suppress the growth activation caused by dominant-activating fadA alleles, indicating that constitutively active FadA can cause proliferative growth in the absence of Gbetagamma signaling. We propose that SfaD and FadA are both positive growth regulators with partially overlapping functions and that FlbA has an important role in controlling the activities of both proteins. Inactivation of signaling events stimulated by both components of the heterotrimeric G protein is essential for both sexual and asexual sporulation.

Amino Acid Sequence↗
PubMed1999

Extragenic suppressors of loss-of-function mutations in the aspergillus FlbA regulator of G-protein signaling domain protein.

We showed previously that two genes, fl bA and fadA, have a major role in determining the balance between growth, sporulation, and mycotoxin (sterigmatocystin; ST) production by the filamentous fungus Aspergillus nidulans. fadA encodes the alpha subunit for a heterotrimeric G-protein, and continuous activation of FadA blocks sporulation and ST production while stimulating growth. fl bA encodes an A. nidulans regulator of G-protein signaling (RGS) domain protein that antagonizes FadA-mediated signaling to allow development. To better understand FlbA function and other aspects of FadA-mediated growth control, we have isolated and characterized mutations in four previously undefined genes designated as sfaA, sfaC, sfaD, and sfaE (suppressors of flbA), and a new allele of fadA (fadAR205H), all of which suppress a fl bA loss-of-function mutation ( fl bA98). These suppressors overcome fl bA losses of function in both sporulation and ST biosynthesis. fadAR205H, sfaC67, sfaD82, and sfaE83 mutations are dominant to wild type whereas sfaA1 is semidominant. sfaA1 also differs from other suppressor mutations in that it cannot suppress a fl bA deletion mutation (and is therefore allele specific) whereas all the dominant suppressors can bypass complete loss of fl bA. Only sfaE83 suppressed dominant activating mutations in fadA, indicating that sfaE may have a unique role in fadA- fl bA interactions. Finally, none of these suppressor mutations bypassed fl uG loss-of-function mutations in development-specific activation.

Alleles↗
PubMed1999

APC resistance and other haemostatic variables during pregnancy and puerperium.

Forty-eight healthy pregnant women were studied prospectively and longitudinally. Blood sampling was performed at 10-15, 23-25, 32-34 and 38-40 weeks of gestation, within one week and at eight weeks postpartum. Classic and modified activated protein C ratio decreased as pregnancy progressed. In the third trimester 92% of the ratios measured with the classic test were above the lower reference level whereas all modified test ratios were normal. Slight activation of blood coagulation was shown with increased levels of prothrombin fragment 1+2, soluble fibrin and D-dimer. Fibrinogen, factor VIII and plasminogen activator inhibitor type I and type 2 increased. Protein S and tissue plasminogen activator activity decreased. Protein C remained unchanged. No correlation was found between the decrease in classic APC ratio and changes in factor VIII, fibrinogen, protein S, prothrombin fragment 1+2 or soluble fibrin, nor between the increase in soluble fibrin and changes in prothrombin fragment 1+2, fibrinogen and D-dimer.

Activated Protein C Resistance↗
PubMed1998

Evaluation of a modified APTT-based method for determination of APC resistance in plasma from patients on heparin or oral anticoagulant therapy.

An APTT-based kit method (Coatest APC Resistance), modified by predilution 1+4 of sample plasma in a plasma diluent containing a heparin antagonist (V-DEF plasma), has been evaluated on plasmas from patients treated with unfractionated (n = 110) or either of three different low molecular heparins (n=44), or with oral anticoagulants (n=147). Irrespective of treatment, no difference was observed in the APC response as compared to untreated individuals (n=62), and a complete discrimination was obtained between individuals with a normal factor V genotype and those carrying the FV:Q506 mutation. Furthermore, in contrast to the original, APTT-based kit method, where anticoagulant therapy results in a prolongation of the APTT, the modified kit provided APTT values within the normal range for orally anticoagulated (INR< or =6) and for all heparin treated (< or =1 IU/mL) patients except for one with a suspected presence of phospholipid antibodies. Due to the predilution in V-DEF plasma, contamination with platelets up to 1.5 x 10(4)/microL had a negligible effect on analysis of frozen plasmas regarding their classification as normal or abnormal. Analyses of fresh plasmas show no influence at platelet counts up to 6x10(4)/microL. Consequently, negligible differences in APC ratios were obtained between fresh and frozen plasmas. In conclusion, the modified kit method is applicable to plasmas from anticoagulated patients as well as from untreated individuals, allowing a safe assignment regarding the presence or absence of the FV:Q506 genotype.

Administration, Oral↗
PubMed1996

Molecular characterization of a saline-soluble lectin from a parasitic fungus. Extensive sequence similarities between fungal lectins.

It has been proposed that the interactions between several parasitic and pathogenic fungi and their hosts are mediated by soluble lectins present in the fungus. We have cloned and analyzed a gene encoding such a lectin (AOL) from the nematophagous fungus Arthrobotrys oligospora (deuteromycete). The deduced primary structure of the AOL gene displayed an extensive similarity (identity 46.3%) to that of a gene encoding a lectin (ABL) recently isolated from the mushroom Agaricus bisporus (basidiomycete), but not to any other fungal, microbial, plant or animal lectins. The similarities between AOL and ABL were further demonstrated by the observation that an antibody specific for AOL cross-reacted with ABL. Together with data showing that AOL has a binding specificity that is similar to that of ABL [Rosen, S., Bergström, J., Karlsson, K.-A. & Tunlid, A. (1996) Eur. J. Biochem. 238, 830-837], these results indicate that AOL and ABL are members of a novel family of saline soluble lectins present in fungi. Southern blots indicated that there is only one AOL gene in the genome encoding a subunit (monomer) of the lectin. The primary structure of AOL did not show the presence of a typical N-terminal signal sequence. Comparison of the deduced primary structure with the molecular mass of AOL as determined by electrospray mass spectrometry (16153 Da), indicated that AOL has an acetylated N-terminal but no other post-translational modifications, and that a minor isoform is formed by deamidation. Circular dichroism (CD) spectroscopy suggested that the secondary structure of AOL contains 34% beta-sheets, 21% alpha-helix, and 45% turns and coils.

Agaricus↗
PubMed1996

A multispecific saline-soluble lectin from the parasitic fungus Arthrobotrys oligospora. Similarities in the binding specificities compared with a lectin from the mushroom agaricus bisporus.

Several fungi can express high levels of saline-soluble and low-molecular-mass lectins that bind to glycoproteins such as fetuin and different mucins but not bind to any monosaccharides. In this paper, we report the binding specificities of such a lectin (designated AOL) isolated from the nematophagous fungus Arthrobotrys oligospora. The results show that AOL is a multispecific lectin that interacts with the following ligands: (a) Several sulfated glycoconjugates including sulfatide, dextran sulfate, and fucoidan. The specificity of this binding was indicated by experiments showing that none of the tested neutral- and sialic-acid-containing glycolipids, chondroitin sulfates B and C, heparin, and polyvinyl sulfate bound to AOL; (b) Phosphatidic acid and phospatidylglycerol, two out of several tested phospholipids. (c) N-linked and O-linked sugar chains bound to intact fetuin. The involvement of such sugar structures was demonstrated by analyzing the binding of AOL to chemically deglycosylated (trifluoromethanesulfonic acid) fetuin. Treating fetuin with O-glycosidase and N-glycosidase indicated that AOL bound to Gal beta GaLNAc alpha-Ser/Thr and to some N-linked complex sugars, respectively. Further assays demonstrated that AOL could interact with several other glycoproteins containing O-linked and/or N-linked sugar chains. The observations that AOL did not bind to free N-linked sugars isolated from fetuin, or to fetuin treated with trypsin or pronase, or to any of the tested neoglycoproteins and glycolipids with neutral- or sialic acid-containing sugars, indicated that the sugar chains need to be bound to an intact peptide backbone to interact with AOL. We have recently shown that the deduced primary structure of AOL has a high similarity to the sequence of a saline-soluble lectin isolated from the mushroom Agaricus bisporus (ABL) (Rosén, S., Kata, M., Persson, Y., Lipniunas, P. H., Wikström, M., van den Hondel, C. A. M. J. J., van den Brink, J. M., Rask, L., Hedén L.-O. and Tunlid, A., see companion paper). It is well known that ABL binds to Gal beta 3GaLNAc alpha-Ser/Thr, and in this paper we demonstrate that ABL binds to sulfatide, phosphatidic acid, phospatidylglycerol, and possibly also to the same N-linked complex sugars as AOL. The above data indicate that AOL and ABL are members of a novel family of fungal lectins sharing similar primary structure and binding properties.

Agaricus↗