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Biomedical subjects

M Hansson

Publications and source records attributed to M Hansson.

At least 73 records · Page 4Linked to original sources
PubMed1996

Autologous peripheral blood stem cells: collection and processing.

The rapid development in the area of collecting and processing autologous peripheral blood stem cells (PBSC) is reflected by the escalating number of patients treated with PBSC, and by the increasing amount of literature on the subject. Clinical experience suggests that among the variables with a negative influence on mobilization of PBSC, the most important may be the amount of previous stem cell toxic chemotherapy. In selecting patients suitable for autologous PBSC support, the requirement of an adequate anti-tumor therapy has to be weighed against the risk of chemotherapy related stem cell toxicity which will result in inability to collect a sufficient amount of PBSC. The general consensus is that a sufficient PBSC-autograft should contain 2-5 x 10(6) CD34+/kg body weight, but attempts to provide a recommended optimal or threshold level are hampered by the lack of standardized methods for CD34+ cell enumeration. In addition, the time to haematological recovery depends both on the dose of infused CD34+ cells and also on the amount of previous chemotherapy, which affects both the quality of the graft and the supportive microenvironment of the host. The quality of the autograft may also be contaminated by malignant cells, even if the biological significance of tumor cell detection in the PBSC graft has not yet been established. Recent development of methods for in vitro purging and selection of CD34+ cells for clinical use have provided the means to avoid or reduce reinfusion of malignant cells. Future directions of clinical research include the ability to define and enumerate the proportion of stem cells versus committed progenitor cells among the CD34+ cells in a PBSC collection, which will be important to ensure rapid engraftment as well as long term haematopoiesis.

Antigens, CD34↗
PubMed1996

Histaminergic regulation of interferon-gamma (IFN-gamma) production by human natural killer (NK) cells.

Monocytes, recovered from human peripheral blood by counter-current centrifugal elutriation, effectively inhibit the production of IFN-gamma by CD3-/56+ NK cells in response to IL-2. This study aimed at defining the nature of the inhibitory signal, particularly the importance of monocyte-derived reactive metabolites of oxygen. It was found that monocytes recovered from patients with chronic granulomatous disease (CGD), a condition characterized by deficient NADPH-oxidase activity of phagocytes, did not inhibit IFN-gamma production by NK cells. Further, catalase, a scavenger of hydrogen peroxide, completely reversed the inhibitory signal whereas scavengers of the superoxide anion, hypohalous acids, the hydroxyl radical, or nitric oxide synthesis inhibitors such as L-NMMA were ineffective. Inhibition of IFN-gamma production was operating on a pretranslational level, as indicated by the inability of enriched NK cells to accumulate IFN-gamma mRNA in the presence of elutriated monocytes. Hydrogen peroxide, at micromolar concentrations, reconstituted the inhibition of IFN-gamma production when added to enriched NK cells. Histamine, a biogenic amine which inhibits the generation of reactive oxygen metabolites in monocytes, abrogated the inhibition of IFN-gamma production in NK cells; by this mechanism, histamine strongly synergized with IL-2 to induce IFN-gamma in mixtures of NK cells and monocytes. The synergizing effect of histamine was specifically mediated by H2-type histamine receptors. We conclude that: (i) the induction of IFN-gamma mRNA in NK cells is effectively down-regulated by products of the oxidative metabolism of monocytes; and (ii) histamine effectively enhances IFN-gamma production by preventing monocyte-induced oxidative damage to NK cells.

Base Sequence↗
PubMed1996

Histaminergic regulation of NK-cells: protection against monocyte-induced apoptosis.

Human natural killer (NK) cells (with CD3-/56+ phenotype) acquired features characteristic of apoptosis after incubation with autologous monocytes, as revealed by apoptotic nuclear morphology and degradation of DNA into oligonucleosomal fragments. The monocyte-induced apoptosis in NK-cells was prevented by the biogenic amine histamine at concentrations exceeding 0.1 microM. The protective effect of histamine was blocked by the H2-receptor (H2R) antagonist ranitidine but not by AH202399 A, a chemical control to ranitidine devoid of H2R affinity. It is concluded that histaminergic mechanisms may serve to protect NK cells from damage inflicted by products of the oxidative metabolism of monocytes.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1996

Estimation of single event-related potentials utilizing the Prony method.

This paper deals with estimation of the waveform of a single event-related potential, sERP. An additive noise model is used for the measured signal and the SNR of the disturbed sERP is approximately 0 dB. The sERP is described by a series expansion where the basis functions are damped sinusoids. The fundamental basis function is estimated by the least squares Prony method, derived for colored noise. The performance of the Prony method for different forms of the power density spectrum of the noise is investigated. A white noise approximation can be used at a low signal-to-noise (SNR). The basis functions change slowly but the waveform of the sERP may vary from one stimulus to another, thus we average a small number of correlation functions in order to increase the SNR. The method is evaluated by using measurements from four subjects and the results confirm the variability of the sERP.

Algorithms↗
PubMed1996

NK cell-mediated killing of AML blasts: role of histamine, monocytes and reactive oxygen metabolites.

Blasts recovered from patients with acute myelogenous leukaemia (AML) were lysed by heterologous natural killer (NK) cells treated with NK cell-activating cytokines such as interleukin-2 (IL-2) or interferon-alpha (IFN-alpha). The cytokine-induced killing of AML blasts was inhibited by monocytes, recovered from peripheral blood by counterflow centrifugal elutriation. Histamine, at concentrations exceeding 0.1 microM, abrogated the monocyte-induced inhibition of NK cells; thereby, histamine and IL-2 or histamine and IFN-alpha synergistically induced NK cell-mediated destruction of AML blasts. The effect of histamine was completely blocked by the histamine H2-receptor (H2R) antagonist ranitidine but not by its chemical control AH20399AA. Catalase, a scavenger of reactive oxygen metabolites (ROM), reversed the monocyte-induced inhibition of NK cell-mediated killing of blast cells, indicating that the inhibitory signal was mediated by products of the respiratory burst of monocytes. It is concluded that (i) monocytes inhibit anti-leukemic properties of NK cells, (ii) the inhibition is conveyed by monocyte-derived ROM, and (iii) histamine reverses the inhibitory signal and, thereby, synergizes with NK cell-activating cytokines to induce killing of AML blasts.

CD56 Antigen↗
PubMed1995

Hydrophobicity engineering to facilitate surface display of heterologous gene products on Staphylococcus xylosus.

Protein engineering has been employed to investigate the effect of specific amino acid changes on the targeting of heterologous proteins to the outer cell surface of the Gram-positive bacterium Staphylococcus xylosus. Three different variants, corresponding to a 101 amino acid region of the major glycoprotein (G protein) of human respiratory syncytial virus (RSV), were generated in which multiple hydrophobic phenylalanine residues were either substituted or deleted. The different G protein fragments were expressed as one part of recombinant receptors designed for surface display on S. xylosus cells. The engineered variants of the RSV G protein hybrid receptors were, in contrast to a non-engineered fragment, efficiently targeted to the outer cell surface of recombinant S. xylosus cells as determined by different methods, including fluorescence-activated cell sorting. In addition, immunization of mice with live recombinant S. xylosus demonstrated that surface exposure was required to generate receptor-specific antibodies. The present strategy of hydrophobic engineering should be of general interest in surface-display applications and for secretion of proteins otherwise difficult to translocate through host cell membranes.

Amino Acid Sequence↗
PubMed1995

Purification, crystallization, and preliminary X-ray analysis of Bacillus subtilis ferrochelatase.

Bacillus subtilis ferrochelatase (EC 4.99.1.1), the final enzyme in protoheme IX biosynthesis, was produced with an inducible T7 RNA polymerase expression system in Escherichia coli and purified from the soluble cell fraction. It was crystallized from polyethylene glycol solution using the microseeding technique. The crystals diffract to a minimum Bragg spacing of 2.1 A. The space group is P4(2) with unit cell dimensions a = b = 50.2 A, c = 120.1 A.

Bacillus subtilis↗
PubMed1995

Adipose tissue concentrations of dioxins and dibenzofurans in patients with malignant lymphoproliferative diseases and in patients without a malignant disease.

Concentrations of dioxins (PCDD) and dibenzofurans (PCDF) were analysed in adipose tissue from seven patients with malignant lymphoproliferative diseases and 12 surgical patients without a malignant disease. All cases in the first group had reported potential exposure to PCDD and PCDF. Of the analysed congeners significantly higher concentrations of 1,2,3,7,8-pentachlorodioxin, 1,2,3,6,7,8-hexachlorodioxin, and 2,3,4,7,8-pentachlorodibenzofuran were found in the cases with lymphoproliferative diseases compared with the patients in the other group. Higher mean concentration of 2,3,7,8-TCDD was also found in the first group but not significantly so. Toxic equivalents of PCDD and PCDF were significantly higher in the first group (mean 64.7 pg/g, range 19.9-187) than in the second group (mean 29.7 pg/g, range 12.9-53.4). Even if the cases with lymphoproliferative diseases in this case series were potentially exposed to PCDD/PCDF in contrast to the other group, the observed differences may be of may be of interest in relation to the aetiology of these malignancies. Immunosuppression increases the risk for malignant lymphoproliferative diseases, and PCDD/PCDF have established immunotoxic properties.

Adipose Tissue↗
PubMed1995

Immunogens containing sequences from antigen Pf332 induce Plasmodium falciparum-reactive antibodies which inhibit parasite growth but not cytoadherence.

Immunogens based upon sequences from the P. falciparum asexual blood stage antigen Pf332 were assessed for their capacity to induce antibodies inhibiting parasite growth or cytoadherence of infected erythrocytes in vitro. Selection of the Pf332 sequences was based on their reactivity with the human monoclonal antibody (MoAb) 33G2 which inhibits parasite growth as well as cytoadherence in vitro. Octameric multiple antigen peptides (MAP) were assembled based upon either a trimer of the minimal epitope recognized by the MoAb, VTEEI, or a Pf332 sequence including that motif, SVTEEIAEEDK. A dimer of SVTEEIAEEDK was also expressed in Escherichia coli, genetically fused to ZZ, two IgG-binding domains of staphylococcal protein A. Rabbit antibodies elicited by the immunogens reacted with Pf332 in immunofluorescence and in ELISA with Pf332 peptides which were also recognized by MoAb 33G2. The MAP with branched (VTEEI)3 peptide induced the highest titres of P. falciparum-reactive antibodies. In contrast to MoAB 33G2, none of the polyclonal Pf332 reactive sera cross-reacted with repeat sequences of the malaria antigen Pf155/RESA. The polyclonal Pf332-reactive antibodies inhibited parasite growth efficiently but had no or very low inhibitory effect in a cytoadherence assay. Thus, while Pf332 may be an important target for parasite neutralizing antibodies its involvement in cytoadherence is unclear.

Amino Acid Sequence↗
PubMed1995

Surface display compared to periplasmic expression of a malarial antigen in Salmonella typhimurium and its implications for immunogenicity.

Two different expression systems were investigated for the production of an 80 amino acid polypeptide, M3, from the C-terminus of the Plasmodium falciparum blood stage antigen Pf155/RESA in an attenuated Salmonella typhimurium vaccine strain. Upon expression, the malarial polypeptide was targeted either to the periplasm as a soluble fusion protein containing two IgG-binding domains (ZZ) from the staphylococcal protein A or, to the bacterial surface as an insert within a chimeric outer membrane protein A (OmpA) derived from Escherichia coli and Shigella dysenteriae. Both the ZZM3 and the OmpAM3 proteins were stably expressed in the periplasm or on the surface of Salmonella, respectively. The ZZ expression system yielded 10-100 times more malarial immunogen than did the OmpA system. Live recombinant Salmonella expressing ZZM3 or OmpAM3 were used to immunize mice intraperitoneally. Both the ZZM3 and OmpAM3 genes persisted for up to three weeks in bacteria isolated from different lymphoid organs. Bacteria expressing ZZM3 induced antibodies to M3, ZZ and to the Pf155/RESA antigen whereas, bacteria producing OmpAM3 induced similar levels of antibodies reactive with M3 but not with Pf155/RESA. Both recombinants induced a memory response of antibodies reactive with both M3 and Pf155/RESA. The high levels of M3 produced by the ZZ expression system make it suitable for the expression of heterologous antigens in Salmonella. Nevertheless, in spite of the quantitative difference in M3 expression, the ZZ and OmpA constructs elicited comparable immune responses to M3.

Animals↗
PubMed1995

Increase of monocytes predicts mobilization of peripheral stem and progenitor cells after chemotherapy followed by G-CSF administration.

Mobilization of primitive haematopoietic cells to the peripheral blood was studied in 25 patients with haematological malignancies. The optimal level of peripheral stem cells (PSC), defined by their surface expression of CD34, was significantly higher after mobilization with G-CSF, either following chemotherapy or alone (median: 123 x 10(6)/l and 143 x 10(6)/l of CD34+ cells respectively) than without administration of G-CSF subsequent to chemotherapy (median: 27 x 10(6)/l of CD34+ cells). An individual variation in when optimal mobilization of CD34+ cells and myeloid progenitors occurs after chemotherapy and G-CSF administration was noted (median: day 12, range 7-24 days), which makes it difficult to predict when PSC collections in a given patient should be performed. In this study, chemotherapy followed by G-CSF administration resulted in a short lasting (2-3 days) peak appearance of CD34+ cells that could predicted by a 2-fold increase in absolute numbers of monocytes, as compared to the previous day. After the peak level of CD34+ cells in the blood was reached, no further increase in monocytes was seen. The identification of an increase in monocytes, to be used as a predictive variable for when optimal mobilization of PSC will occur in a given patient, may be particularly useful in the individual timing of PSC collections from non-hospitalized patients.

Adolescent↗
PubMed1995

Cell surface display of recombinant proteins on Staphylococcus carnosus.

A novel expression system for surface display of heterologous proteins on Staphylococcus carnosus cells has been developed. Taking advantage of the promoter and secretion signals, including a propeptide region, from the lipase gene of Staphylococcus hyicus and the cell wall-spanning and membrane-binding region of protein A from Staphylococcus aureus, efficient surface display of an 80-amino-acid peptide from a malaria blood stage antigen could be achieved. A serum albumin binding protein from streptococcal protein G was used both as a general reporter molecule and to increase the accessibility of the surface-displayed proteins. Immunoblotting, immunogold staining, and immunofluorescence on intact recombinant S. carnosus cells verified the presence of the propeptide, the malaria antigen, and the albumin-binding reporter protein on the bacterial surface. For the first time, fluorescence-activated cell sorting was used to analyze the presence of surface-displayed hybrid receptors on gram-positive bacteria.

Antigens, Protozoan↗
PubMed1995

Occupational exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans in a magnesium production plant.

OBJECTIVES: The production of magnesium is a well known source of both aliphatic and aromatic chlorinated compounds, among others the polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The aim of this study was to establish whether increased concentrations of PCDDs and PCDFs could be found in the blood of workers in a magnesium plant. METHODS: Blood plasma from 10 workers, employed at a magnesium plant for 10 to 36 years, and from a control group consisting of nine people who had no direct contact with the production were studied. Isomer specific analyses of PCDDs and PCDFs by means of high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) techniques were performed. RESULTS: A significant increase was found in the concentrations of some of the congeners, mainly PCDFs, in the workers compared with the control group. Octachlorodibenzofuran (OCDF) is the congener that most strongly correlates with occupational exposure in the magnesium plant. Low concentrations of 1,2,3,4,6,8,9-heptachlorodibenzofuran were found in seven of the workers. Such isomers--that is, not 2,3,7,8-substituted--are rarely found in human samples. CONCLUSION: Due to the long biological half lives and lipid solubility of PCDDs and PCDFs, blood analyses may serve as an index of past cumulative occupational exposure and a means of assessing a person's exposure situation.

Benzofurans↗
PubMed1995

Immunoreactive atrial and brain natriuretic peptides are co-localized in Purkinje fibres but not in the innervation of the bovine heart conduction system.

Recently, we observed that atrial natriuretic peptide (ANP) immunoreactivity was present in Purkinje fibres and nerve fibre varicosities in the conduction system of the bovine heart. In order to elucidate further the morphological correlation between natriuretic peptides and the conduction system, the distribution of brain natriuretic peptide (BNP) was examined. The different parts of the conduction system in the bovine heart were dissected out and processed for immunohistochemistry with antisera against BNP and ANP. BNP immunoreactivity was frequently observed in Purkinje fibres of the atrioventricular bundle, whereas only a few Purkinje fibres in the ventricular part of the conduction system showed immunoreaction. BNP immunoreactivity was detected in regions of the Purkinje fibres which also showed ANP immunoreactivity. BNP immunoreactivity was not observed in nerve fibre varicosities. Methodologically, a larger number of small BNP immunofluorescent granular structures was observed by using an elution-restaining technique instead of conventional immunohistochemistry. The present study shows that BNP and ANP immunoreactivities frequently occur in the atrioventricular bundle and that they are co-localized in Purkinje fibres, but not in nerve fibre varicosities, in the conduction system. As previously has been proposed for ANP, the present observations suggest that also BNP may act in an autocrine and/or paracrine way in the conduction cells.

Animals↗
PubMed1995

Genetic restriction and specificity of the immune response in mice to fusion proteins containing repeated sequences of the Plasmodium falciparum antigen Pf155/RESA.

The genetic restriction and specificity of the immune response in mice to two fusion proteins, ZZ-M3 and ZZ-M5, were studied. These proteins contain two IgG-binding domains (ZZ) from staphylococcal protein A, and repeated sequences from the C-terminal [(VEHDAEEN)5 (VEEN)10] (M3) or central [(VEEPTVADDEH)3(VEEPTVAEEH)2] (M5) regions of the Plasmodium falciparum malaria blood stage antigen Pf155/RESA. Strong antibody and T-cell responses to M3 and M5 were linked to expression of the I-Ak allele, and T-cell responses to the bacterial fusion partner ZZ were restricted to mice of the H-2k haplotype. The response to M5 was less restricted than that to M3, giving intermediate responses in mice of H-2d haplotypes as well. However, ZZ-M5-primed lymph node (LN) cells from these mice were primarily induced to proliferate in vitro by the complete ZZ-M5 construct and not by synthetic peptides representing the repeated subunits in M5. The reactivity with intact Pf155/RESA in erythrocyte membrane immunofluorescence was weak of antisera from mice immunized with ZZ-M5, whereas the reactivity of antisera from mice immunized with ZZ-M3 roughly paralleled their reactivity with M3 in an enzyme-linked immunosorbent assay (ELISA). The antibody responses induced by immunization with ZZ-M3 or ZZ-M5 were specific for M3 or M5, respectively, while activated T cells displayed cross-reactivity between M3 and M5 in an in vitro proliferation assay. The results indicate that the assembly of repeated sequences in fusion proteins affects both the MHC class II restriction and the specificity of the induced antibody and T-cell responses.

Amino Acid Sequence↗
PubMed1994

Atrial natriuretic peptide in the innervation of the bovine heart conduction system: relationship with substance P and autonomic innervation--immunohistochemical studies.

Recently, we observed that atrial natriuretic peptide (ANP) immunoreactivity (IR) was present not only in the Purkinje fibres, but also in nerve fibre varicosities in the conduction system of the bovine heart. These findings and previous observations that ANP is able to influence autonomic neurotransmission in the heart, lead us to elucidate the possible occurrence of ANP in the sympathetic and/or parasympathetic nervous systems and/or in various types of peptidergic innervation in the conduction system. The different parts of the conduction system of bovine hearts were dissected out and processed for immunohistochemistry including double-staining, using antisera against ANP, tyrosine hydroxylase and different neuropeptides. We observed that some of the nerve fibre varicosities exhibiting ANP-IR showed substance P-IR and that ANP was present as scattered immunoreactive granules in intracardial, presumably parasympathetic, ganglionic cells. The study shows that ANP is likely to be present in parasympathetic innervation and in afferent nerve endings in the bovine heart conduction system.

Animals↗
PubMed1994

Purification and characterisation of a water-soluble ferrochelatase from Bacillus subtilis.

Bacillus subtilis ferrochelatase is encoded by the hemH gene of the hemEHY gene cluster and catalyses the incorporation of Fe2+ into protoporphyrin IX. B. subtilis ferrochelatase produced in Escherichia coli was purified. It was found to be a monomeric, water-soluble enzyme of molecular mass 35 kDa which in addition to Fe2+ can incorporate Zn2+ and Cu2+ into protoporphyrin IX. Chemical modification experiments indicated that the single cysteine residue in the ferrochelatase is required for enzyme activity although it is not a conserved residue compared to other ferrochelatases. In growing B. subtilis, the ferrochelatase constitutes approximately 0.05% (by mass) of the total cell protein, which corresponds to some 600 ferrochelatase molecules/cell. The turnover number of isolated ferrochelatase, 18-29 min-1, was found to be consistent with the rate of haem synthesis in exponentially growing cells (0.2 mol haem formed/min/mol enzyme). It is concluded that the B. subtilis ferrochelatase has enzymic properties which are similar to those of other characterised ferrochelatases of known primary structure, i.e. ferrochelatases of the mitochondrial inner membrane of yeast and mammalian cells. However, in contrast to these enzymes the B. subtilis enzyme is a water-soluble protein and should be more amenable to structural analysis.

Amino Acid Sequence↗