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Biomedical subjects

M Christensson

Publications and source records attributed to M Christensson.

9 recordsLinked to original sources
PubMed2004

Treatment of municipal wastewater in a hybrid process using a new suspended carrier with large surface area.

An activated sludge/biofilm hybrid process treating municipal wastewater was studied in pilot plant trials. A new type of suspended carrier, with large effective surface area, was employed in the process with the aim of enhancing nitrification. The pilot plant was operated for 1.5 years in five different configurations including pre-denitrification in all five and enhanced biological phosphorus removal in the final two. The wastewater temperature ranged between 11 degrees C and 20 degrees C, and the nominal dissolved oxygen (DO) level was 5-6 mg/L. The nitrification rate obtained on the new carrier within the hybrid stage was in the range of 0.9-1.2 g NH4-N/m2/d corresponding to a volumetric rate of 19-23 g NH4-N/m3/h (total nitrification including nitrification in the suspended solids). More than 80% of the total nitrification took place on the carrier (and the remainder in the suspended solids). The nitrification rate was shown to correlate with DO, decreasing when the DO was decreased. The results supported the idea of using the new carrier as a tool to upgrade plants not having nitrification today or improve nitrification in activated sludge processes not reaching necessary discharge levels. The large surface area present for nitrification makes it possible to obtain high nitrification rates within limited volumes. The possibility to keep the total suspended solid content low (< 3 g/L) and avoiding problems with the filament Microthrix parvicella, are other beneficial properties of the hybrid process.

Biofilms↗
PubMed2001

Inverse cascade in decaying three-dimensional magnetohydrodynamic turbulence.

We perform direct numerical simulations of three-dimensional freely decaying magnetohydrodynamic turbulence. For helical magnetic fields, an inverse cascade effect is observed in which power is transferred from smaller scales to larger scales. The magnetic field reaches a scaling regime with self-similar evolution, and power-law behavior at high wave numbers. We also find power-law decay in the magnetic and kinematic energies, and power-law growth in the characteristic length scale of the magnetic field.

Journal Article↗
PubMed2000

T cell activation in patients with ANCA-associated vasculitis: inefficient immune suppression by therapy.

BACKGROUND AND AIMS: Patients with vasculitic disease and autoantibodies to neutrophil cytoplasmic antigens (ANCA) generally respond to immunosuppressive therapy with a reduction of the inflammation and lowering of the ANCA titre. However, most patients experience relapses, sometimes after years of quiescence. In the present study we addressed the question whether the relapsing nature of this disease could be dependent on an underlying T cell activation. Patients were analyzed at disease onset, in remission while on treatment, and in quiescence. PATIENTS AND METHODS: Blood lymphocyte subsets and the expression of molecules associated with T cell activation were analyzed by flow cytometry and soluble interleukin-2 receptor (sIL2r) levels in serum by ELISA. Three patient categories (la, 1b and 2) were studied and compared with age-matched healthy controls (1a: 16 patients at onset of the disease before therapy, 1b: 10 patients from group 1a, re-analyzed after first remission, 2: 11 other patients in quiescence, 2-10 years after debut). RESULTS: All patient groups, 1a, 1b and 2, showed signs of T cell activation such as reduced CD28 on CD3+ and increased of the early T cell activation marker CD69 on CD3+, as well as of CD38 on CD8+ T cells. The sIL2r levels were significantly raised in all patient categories (la: 4280, 1b: 1844, 2: 2882 ng/ml) compared with the controls (923 ng/ml). CONCLUSION: Patients with ANCA-positive vasculitis show an increased expression of T cell activation markers irrespective of immunosuppressive therapy or disease phase. Such memory cells may form the basis for the remitting course of vasculitides and would be a rational target for new strategies of therapy.

Adult↗
PubMed1998

Lack of T-lymphocytosis and poor interferon gamma production in BAL fluid from HIV-negative immunocompetent patients with pulmonary non-tuberculous mycobacteriosis.

Very little is known about the pathogenesis of pulmonary non-tuberculous mycobacteriosis in immunocompetent individuals. Local inflammatory response was assessed by examining bronchoalveolar lavage fluid from 13 HIV-negative patients (12 F) without known cell-mediated immunosuppression, aged 48-72 y (median age 60 y), with non-tuberculous lung mycobacteriosis. Macrophages, lymphocytes, polymorphonuclear neutrophils and eosinophils in bronchoalveolar lavage fluid were analysed morphologically, and the subsets of T-lymphocytes (CD3+, CD4+, CD8+), HLA-DR+, B-lymphocytes (CD19+) and CD16+/CD56+ cells (natural killer, NK cells) were analysed by flow cytometry. Interleukin-1 beta (IL-1beta), IL-2, IL-4, IL-6, IL-8, IL-10 and interferon-gamma (IFN-gamma) levels were assessed by ELISA. The total number of cells/ml was significantly higher in BAL fluid from the patients (median value=880 x 10(3)/ml) compared to six healthy controls (200 x 10(3)/ml). The polymorphonuclear neutrophil population was significantly increased in the patients both proportionally and in the count/ml. The proportion of macrophages was significantly reduced in the patients but not the count/ml. The count of lymphocytes/ml was significantly higher in the patients but the proportion of lymphocytes was unchanged. No significant difference was seen in the relative proportion of NK cells, B- or T-lymphocytes and HLA-DR+ compared to the healthy controls. The IL-1beta and IL-8 levels were significantly increased in the patients. No differences were seen between the patients and controls in the leukocyte or lymphocyte subsets in peripheral blood. The local inflammatory response in BAL fluid from the studied patients was characterized by granulocytosis, and increase in the IL-1beta and IL-8 levels. There was no specific T-cell response.

Aged↗
PubMed1996

Flow cytometric quantitation of serum anti-D in pregnancy.

BACKGROUND: The major cause of fetal hemolytic disease is maternal immunization to D in D-incompatible pregnancies. To prevent complications, D-incompatible pregnancies are monitored for the level of maternal anti-D. At present, the monitoring of anti-D levels is performed by the indirect antiglobulin test complemented by quantitation by the technique used in an automated antibody detection and quantitation instrument. STUDY DESIGN AND METHODS: Flow cytometry was used to quantitatively determine the level of anti-D in serum and to analyze the IgG subclass distribution and the presence of IgM anti-D in these samples. The results were compared to the indirect antiglobulin test titer and to the results obtained by the technique used in an automated antibody detection and quantitation instrument. RESULTS: Flow cytometry allowed sensitive and accurate determinations of anti-D levels with low interassay and intra-assay variability, both for serum samples and standard curves. CONCLUSION: Flow cytometry is a simple, rapid, and reliable method for determining the serum levels of D antibodies and their Ig subclass distribution. It is therefore well suited for the monitoring of women during D-incompatible pregnancies.

Female↗
PubMed1996

Lack of T-helper lymphocytes in BAL fluid from a HIV-negative patient with recurrent non-tuberculous mycobacterial lung infections.

We describe here a previously healthy, 42 year old, HIV-negative woman. Following a seemingly successful 2-year antimycobacterial regimen for a lung infection caused by Mycobacterium avium/intracellulare she acquired a lung infection caused by M. chelonei. Characterization of alveolar cells from bronchoalveolar lavage fluid using flow cytometry revealed a total lack of T-cell subset CD4+ helper lymphocytes in spite of a normal proportion of the CD3+ and CD4+ T-cells in peripheral blood. The levels of Th2 cytokines such as IL-4, TGF-beta and G-CSF were higher in the patient's alveolar cells than in the cells of 4 healthy controls. This imbalance of cells and cell cytokines may contribute to the patient's susceptibility for non-tuberculous mycobacteria and her failure to eradicate these microorganisms.

Adult↗
PubMed1990

A method for monitoring intracerebral temperature in neurosurgical patients.

Current interest in brain temperature and selective brain cooling makes a method allowing for continuous monitoring of intracerebral temperature in humans desirable. The authors describe a safe, simple, and reliable technique using a thermocouple of copper and constantan in combination with intraventricular monitoring of intracranial pressure for measurement of brain temperature in neurosurgical patients.

Body Temperature↗