Biomedical subjects

J Andersson

Publications and source records attributed to J Andersson.

At least 37 records · Page 2Linked to original sources

PubMed2002

Reasons among older Swedish women of not participating in a food survey.

OBJECTIVES: To (a) examine participation rate as a function of municipality, age group and living status; and (b) investigate the main reasons for exclusion and declining as stated by the women themselves. DESIGN: Analysis of participation rate and content analysis of statements given in phone calls explaining exclusion or declination from a project in which 24 h recalls and food-diaries were used. SUBJECTS: Self-managing Swedish women (n=505) were systematically selected from a stratified random sample covering single living and cohabiting women aged 64-68, 74-78 and 84-88 y living in three municipalities. RESULTS: No significant differences were found among included and declining women when municipalities and living status was analysed, but significantly more women in the oldest group were excluded (P>0.01). Among those in their 80s living at home, the usual reasons for exclusion were illness, disability or dementia, and many lived in institutions for old people. The four most used explanations to decline participation were 'lack of time', 'tired, fragile, sick or having bad memory', 'not willing to participate in scientific studies' and 'too old and nothing to contribute'. CONCLUSIONS: The participation rate was, compared with other food surveys in the older generation, fairly good, especially among those in their 80s. However, the most active and the very ill and disabled did not participate. SPONSORSHIP: The Swedish Council for Social Research, the Swedish Council for Forestry and Agricultural Research, the Swedish Foundation for Health and Care Sciences and Allergy Research and Uppsala University.

Age Factors↗

PubMed2002

Response of in vivo protein synthesis in T lymphocytes and leucocytes to an endotoxin challenge in healthy volunteers.

In vivo determination of protein synthesis in immune cells reflects metabolic activity and immunological activation. An intravenous injection of endotoxin to healthy volunteers was used as a human sepsis model, and in vivo protein synthesis of T lymphocytes and leucocytes was measured. The results were related to plasma concentrations of selected cytokines, peripheral cell counts and subpopulations of immune cells. The subjects (n = 8 + 8) were randomized to an endotoxin (4 ng/kg) or a saline group. In vivo protein synthesis was determined twice: before and 1-2.5 h after the endotoxin/saline injection. Protein synthesis decreased in isolated T lymphocytes, but increased in leucocytes. Plasma levels of TNF-alpha, IL-8, IL-6, IL-1 ra and IL-10 were elevated, whereas IL-2 and IFN-gamma, produced predominantly by T lymphocytes, did not change in response to endotoxin. Neutrophils increased, whereas lymphocytes and monocytes decreased 2.5 h after the endotoxin injection. Flow cytometry revealed a drop in total CD3+ T lymphocytes and CD56+ natural killer cells, accompanied by an increase in CD15+ granulocytes. In summary, in vivo protein synthesis decreased in T lymphocytes, while the total leucocyte population showed a concomitant increase immediately after the endotoxin challenge. The changes in protein synthesis were accompanied by alterations in immune cell subpopulations and in plasma cytokine levels.

Adult↗

PubMed2002

Delayed and reduced adaptive humoral immune responses in children with shigellosis compared with in adults.

We hypothesized that increased susceptibility to Shigella infection, increased severity of disease and high mortality in children compared with adults were consequences of insufficient adaptive immune responses. Antigen-specific immune responses were studied in paediatric patients (n = 38, 2-10 years) with shigellosis and compared with those of adult patients (n = 30, 18-45 years). Peak frequencies of antigen (invasion plasmid coded antigen B, Ipa-B; lipopolysaccharide, LPS)-specific immunoglobulin (IgM)-antibody secreting cells (ASC) were seen within 3-5 days after the onset of diarrhoea in children, while peak IgA- and IgG-ASCs were obtained 8-10 days later in line with adults. Antigen-specific ASC responses in children ranged between 2 and 4% of the total ASC responses, in contrast to 8-15% in adults. The kinetics of LPS-specific IgG subclass titres was different in younger children (2.5-5 years) (IgG1 > IgG2 > IgG4 > IgG3) compared with in older children (6-8 years) (IgG2 > IgG1 >IgG3 > IgG4) and adults. Secretory IgA levels in stool peaked 8-10 days after onset in both adults and children. However, a rapid induction of stool LPS-specific IgA, IgA1 and IgA2 occurred in adult patients within 3-5 days of onset, while in children, this was delayed by 8-10 days. Similarly, higher number of tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma expressing cells in vitro were seen in adult patients in response to antigens (LPS and Ipa-B) in the acute stage in contrast to paediatric patients. Thus, paediatric patients with shigellosis have reduced and delayed adaptive immune responses compared with adult patients.

Adaptation, Physiological↗

PubMed2001

Dressed to kill? A review of why antiviral CD8 T lymphocytes fail to prevent progressive immunodeficiency in HIV-1 infection.

CD8 T cells play an important role in protection and control of HIV-1 by direct cytolysis of infected cells and by suppression of viral replication by secreted factors. However, although HIV-1-infected individuals have a high frequency of HIV-1-specific CD8 T cells, viral reservoirs persist and progressive immunodeficiency generally ensues in the absence of continuous potent antiviral drugs. Freshly isolated HIV-specific CD8 T cells are often unable to lyse HIV-1-infected cells. Maturation into competent cytotoxic T lymphocytes may be blocked during the initial encounter with antigen because of defects in antigen presentation by interdigitating dendritic cells or HIV-infected macrophages. The molecular basis for impaired function is multifactorial, due to incomplete T-cell signaling and activation (in part related to CD3zeta and CD28 down-modulation), reduced perforin expression, and inefficient trafficking of HIV-specific CD8 T cells to lymphoid sites of infection. CD8 T-cell dysfunction can partially be corrected in vitro with short-term exposure to interleukin 2, suggesting that impaired HIV-specific CD4 T helper function may play a significant causal or exacerbating role. Functional defects are qualitatively different and more severe with advanced disease, when interferon gamma production also becomes compromised.

Acquired Immunodeficiency Syndrome↗

PubMed2001

Two active site asparagines are essential for the reaction mechanism of the class III anaerobic ribonucleotide reductase from bacteriophage T4.

Class III ribonucleotide reductase is an anaerobic enzyme that uses a glycyl radical to catalyze the reduction of ribonucleotides to deoxyribonucleotides and formate as ultimate reductant. The reaction mechanism of class III ribonucleotide reductases requires two cysteines within the active site, Cys-79 and Cys-290 in bacteriophage T4 NrdD numbering. Cys-290 is believed to form a transient thiyl radical that initiates the reaction with substrate and Cys-79 to take part as a transient thiyl radical in later steps of the reductive reaction. The recently solved three-dimensional structure of class III ribonucleotide reductase (RNR) from bacteriophage T4 shows that two highly conserved asparagines, Asn-78 and Asn-311, are positioned close to the essential Cys-79. We have investigated the function of Asn-78 and Asn-311 by site-directed mutagenesis and measured enzyme activity and glycyl radical formation in five single (N78(A/C/D) and N311(A/C)) and one double (N78A/N311A) mutant proteins. Our results suggest that both asparagines are important for the catalytic mechanism of class III RNR and that one asparagine can partially compensate for the lack of the other functional group in the single Asn --> Ala mutant proteins. A plausible role for these two asparagines could be in positioning formate in the active site to orient it toward the proposed thiyl radical of Cys-79. This would also control the highly reactive carbon dioxide radical anion form of formate within the active site before it is released as carbon dioxide. A detailed reaction scheme including the function of the two asparagines and two formate molecules is proposed for class III RNRs.

Amino Acid Sequence↗

PubMed2001

Evidence for superantigen involvement in severe group a streptococcal tissue infections.

Host-pathogen interactions were studied in tissue biopsy samples from patients with severe invasive group A streptococcus (GAS) infections. Skin, subcutaneous tissue, and fascia biopsy samples were divided into clinical grade 1 (no evidence of inflammation [n=7]) or clinical grade 2 (inflamed tissue--erythema and edema including cellulitis, fasciitis, and necrotizing fasciitis [n=24]). In situ imaging demonstrated significantly higher bacterial load in biopsy samples of higher clinical grade (P<.05), and the bacterial load correlated with the in vivo expression of the superantigen streptococcal pyrogenic exotoxin F (P<.02). Increased expression of the interleukin-1 cytokines and significantly higher expression of tumor necrosis factor-beta, interferon-gamma, and the homing receptors CC chemokine receptor 5, CD44, and cutaneous lymphocyte-associated antigen (P<.002-.05) were observed in biopsy samples of higher clinical grade. Thus, the cytokine profile at the local site of infection mimics that of a typical superantigen cytokine response. The findings of this study demonstrate a critical role for superantigens and Th1 cytokines in GAS tissue infections.

Bacterial Proteins↗

PubMed2001

Quantitative single cell methods that identify cytokine and chemokine expression in dendritic cells.

Two techniques based upon flow cytometry (FCM) and in situ image analysis were developed for quantification of intracellular cytokine and chemokine protein expression at the single cell level in dendritic cells (DCs). The qualitative and quantitative differences between the two methods were evaluated. In vitro differentiated DCs were stimulated with lipopolysaccaride (LPS) and thereafter stained for either IL-8, which is secreted through the Golgi-organelle, or IL-1ra, which localises diffusely in the cytoplasm. Microscopic examination, both for fluorophore and enzymatically stained cells, showed that DCs expressed IL-8 and IL-1ra with two different staining patterns. FCM analysis showed high frequencies of IL-1ra producing cells (76+/-13%), which was similar to the frequency obtained by in situ imaging. However, in contrast to IL-1ra, the incidence of IL-8 expressing DCs showed high variability between the donors. The numbers of positive cells were 19+/-19% as measured by FCM. The detection of IL-8 analysed by in situ imaging revealed higher frequencies (26+/-14%). The addition of brefeldin-A, leading to cytoplasmic accumulation of proteins secreted through the Golgi endoplasmatic route, generated a significantly increased signal intensity and incidence of producer cells, resulting in similar frequencies for both methods. FCM has the advantage of being less time consuming than image analysis and is also able to facilitate multiple colour analysis. However, FCM is less accurate in detecting and quantifying cytokines and chemokines with a preserved juxtanuclear staining pattern. The correct choice of detection technique therefore depends on the study question.

Chemokines↗

PubMed2001

Maternal kappa-containing IgG induces a late anti-Kappa response in adult, Kappa-deficient offspring.

Kappa (kappa)-light (L) chain-deficient (Ckappa-/-) mice readily mount a T cell-dependent antibody response after immunization with kappa-containing proteins. Such antibody responses areabsent in normal (Ckappa+/+) animals because of tolerance due to the abundance of kappa-L chains expressed on more than 95% of all B cells and serum immunoglobulins. When heterozygous kappa-sufficient (Ckappa+/-) females are bred with homozygous kappa-deficient (Ckappa-/-) males, half of their offspring will become kappa-deficient but have received kappa-L chain containing maternal Ig, mainly IgG and IgA, through placental and intestinal transmission. The kappa-containing maternal Ig persists for more than 2 months in the circulation of the offspring. Starting from week 15-20 of age, a spontaneous antibody response towards the maternal kappa-L chains can be recorded. The time of onset, as well as the magnitude of the responses differ among individuals of the same litter. Invariably, once a response has been initiated, it transits into an IgG-type of response, which upon injection with kappa-containing protein shows the features of a secondary type of immune response.

Animals↗

PubMed2001

Binding of a model regulator of complement activation (RCA) to a biomaterial surface: surface-bound factor H inhibits complement activation.

The complement system is an important inflammatory mediator during procedures such as cardiopulmonary bypass and hemodialysis when blood is exposed to large areas of biomaterial surface. This contact between blood and the biomaterials of implants and extracorporeal circuits leads to an inflammatory response mediated by the complement system. The aim of this study was to assess the ability of a complement regulator (factor H) immobilised on a biomaterial surface to inhibit complement cascade mediated inflammatory responses. The cross-linker N-succinimidyl 3-(2-pyridyldithio) propionate was used to immobilise factor H on a model biomaterial surface without affecting the biological activity of the inhibitor. Binding of factor H was then characterised using quartz crystal microbalance-dissipation (QCM-D) and enzyme immunoassays for products of complement activation: bound C3 fragments and soluble C3a, sC5b-9, and C1s-C1INA. Immobilised factor H reduced the amount C3 fragments deposited on the biomaterial surface after incubation with serum, plasma. or whole blood. In addition, lower levels of soluble C3a and sC5b-9 were generated after incubation with whole blood. In summary, we have demonstrated that complement activation on a highly activating model surface can be inhibited by immobilised factor H and have defined prerequisites for the preparation of future biomaterial surfaces with immobilised regulators of complement activation.

Biocompatible Materials↗

PubMed2001

Selection events operating at various stages in B cell development.

B cells have to progress through various checkpoints during their process of development. The three transcription factors E2A, EBF (early B cell factor) and Pax5 play essential roles in B cell commitment checkpoints. The various forms of the BCR and their downstream signaling molecules, which are expressed at different stages of B cell development, act as critical checkpoint guards allowing (positive selection) or preventing (negative selection) developmental progression. The recent advances on the molecular mechanisms operating at these various checkpoints are here summarized and discussed.

Animals↗

PubMed2001

Structural basis for allosteric substrate specificity regulation in anaerobic ribonucleotide reductases.

BACKGROUND: The specificity of ribonucleotide reductases (RNRs) toward their four substrates is governed by the binding of deoxyribonucleoside triphosphates (dNTPs) to the allosteric specificity site. Similar patterns in the kinetics of allosteric regulation have been a strong argument for a common evolutionary origin of the three otherwise widely divergent RNR classes. Recent structural information settled the case for divergent evolution; however, the structural basis for transmission of the allosteric signal is currently poorly understood. A comparative study of the conformational effects of the binding of different effectors has not yet been possible; in addition, only one RNR class has been studied. RESULTS: Our presentation of the structures of a class III anaerobic RNR in complex with four dNTPs allows a full comparison of the protein conformations. Discrimination among the effectors is achieved by two side chains, Gln-114 and Glu-181, from separate monomers. Large conformational changes in the active site (loop 2), in particular Phe-194, are induced by effector binding. The conformational differences observed in the protein when the purine effectors are compared with the pyrimidine effectors are large, while the differences observed within the purine group itself are more subtle. CONCLUSIONS: The subtle differences in base size and hydrogen bonding pattern at the effector site are communicated to major conformational changes in the active site. We propose that the altered overlap of Phe-194 with the substrate base governs hydrogen bonding patterns with main and side chain hydrogen bonding groups in the active site. The relevance for evolution is discussed.

Allosteric Site↗

PubMed2001

Changes in circulating blood volume after infusion of hydroxyethyl starch 6% in critically ill patients.

BACKGROUND: The cardiovascular response to a volume challenge with hydroxyethyl starch (HES) (200/0.5) 6% depends on the relation between the volume of HES 6% infused and the expansion of the blood volume in critically ill patients. However, only relatively limited data exist on the plasma expanding effect of infusion of HES 6% in critically ill patients. The purpose of the study was to evaluate the variation in the expansion of the circulating blood volume (CBV) in critically ill patients after infusion of 500 ml of colloid (HES (200/0.5) 6%) using the carbon monoxide method. METHODS: In 20 consecutive patients admitted to the ICU requiring mechanical ventilation and volume expansion, 500 ml of HES (200/0.5) 6% was infused. The CBV was measured immediately before the infusion, 10 min after completing the infusion and then hourly for 8 h. RESULTS: The median volume expansion immediately after infusion was 470 ml (range 270 ml to 840 ml). The corresponding values after 4 h and 8 h were 265 ml (range -30 ml to 460 ml) and 120 ml (range -210 ml to 360 ml), respectively. The increase in CBV was only statistically significant for 4 h. The coefficient of variation of the method for estimation of CBV was 3.6%. CONCLUSIONS: The large interindividual variation of the volume expansion after infusion of HES 6% in critically ill patients illustrates one of the difficulties in optimizing colloid therapy and interpretating the changes in hemodynamic variables after a colloid challenge.

Adult↗

PubMed2001

RANTES promotes growth and survival of human first-trimester forebrain astrocytes.

We have examined the role of alpha and beta chemokines in the promotion of the ontogenetic development of the brain. RANTES was expressed preferentially in human fetal astrocytes in an age-dependent manner. Astrocytes from 5-week-old brains showed high proliferation and reduced survival, whereas 10-week-old astrocytes exhibited opposite effects. These effects were suppressed by anti-RANTES or anti-RANTES receptor antibodies and were enhanced by recombinant RANTES. RANTES induced tyrosine phosphorylation of several cellular proteins and nuclear translocation of STAT-1 in astrocytes. Interferon-gamma (IFN-gamma) was required for RANTES effects because RANTES induced IFN-gamma and only 10-week-old astrocytes expressed the IFN-gamma receptor. Blocking of IFN-gamma with antibody reversed the effects of RANTES, indicating that cytokine/chemokine networks are critically involved in brain development.

Animals↗

PubMed2001

Increased production of IL-7 accompanies HIV-1-mediated T-cell depletion: implications for T-cell homeostasis.

We hypothesized that HIV-1-mediated T-cell loss might induce the production of factors that are capable of stimulating lymphocyte development and expansion. Here we perform cross-sectional (n = 168) and longitudinal (n = 11) analyses showing that increased circulating levels of interleukin (IL)-7 are strongly associated with CD4+ T lymphopenia in HIV-1 disease. Using immunohistochemistry with quantitative image analysis, we demonstrate that IL-7 is produced by dendritic-like cells within peripheral lymphoid tissues and that IL-7 production by these cells is greatly increased in lymphocyte-depleted tissues. We propose that IL-7 production increases as part of a homeostatic response to T-cell depletion.

Cohort Studies↗

PubMed2001

Escherichia coli-induced expression of IL-1 alpha, IL-1 beta, IL-6 and IL-8 in normal human renal tubular epithelial cells.

The aim of the present study was to investigate whether the IL-1 family cytokines, in addition to IL-6 and IL-8, could be induced in normal human cortical epithelial cells in response to bacterial stimuli. Human renal tissue was obtained from 9 patients undergoing elective tumour nephrectomy. Renal cortical epithelial cells of tubular origin were prepared from the unaffected tissue. The proximal tubular cells were stimulated for 2, 6 and 24 h with a heat-inactivated pyelonephritogenic Escherichia coli strain DS-17. Cultured unstimulated tubular cells served as controls. IL-1 alpha, IL-1 beta, IL-1 receptor antagonist, IL-6, IL-8, IL-10, TNF-alpha, G-CSF and GM-CSF were analysed using immunohistochemistry at the single cell level. The nonstimulated cells were found to express low levels of IL-6 and IL-8 (mean value < 3% of total cells). In contrast, E. coli exposure resulted in significantly increased incidences of IL-6 and IL-8 expressing cells (mean values approximately 18% of total cells) peaking within two hours of stimulation (P < 0.008 and P < 0.02 versus non-stimulated cells, respectively). A gradual decrease was thereafter observed at 6 and 24 h, respectively, although persistently higher compared to controls. A different kinetic response was found for IL-1 alpha, IL-1 beta and IL-1 receptor antagonist-expressing cells, which peaked 24 h after E. coli stimulation (mean values 3--10%) (P < 0.008, P < 0.02, P < 0.02 versus non-stimulated cells, respectively). Low levels of TNF-alpha and GM-CSF were found in 3 of the 9 donated epithelial cells, peaking at 2 h, and IL-10 and G-CSF producing cells in 1 patient each. In conclusion we found that heat-inactivated pyelonephritic E. coli induced a proinflammatory cytokine response in the normal human proximal tubular cells including the IL-1 family, IL-6 and IL-8.

Adult↗

PubMed2001

Ribavirin treatment in dialysis patients with chronic hepatitis C virus infection--a pilot study.

Standard treatment for chronic hepatitis C is with interferon (IFN)-alpha and ribavirin for 6-12 months. In dialysis patients only interferon therapy is currently used due to the lack of knowledge concerning ribavirin dosage and side-effects. The aim of this study was to investigate if ribavirin can be added to interferon when treating dialysis patients with hepatitis C. Five patients on haemodialysis and one patient on peritoneal dialysis with chronic hepatitis C, five with genotype 1 and one with genotype 4, were given interferon-alpha2b 3 MU thrice weekly for 4 weeks, whereafter ribavirin 200-400 mg was added, for an intended total treatment period of 28 weeks. Ribavirin plasma concentrations were monitored, using HPLC. Four patients completed the treatment. One patient suffered marked side-effects from interferon and therapy was terminated. One patient developed heart failure and died after 14 weeks of treatment but the death was not considered treatment related. Based on plasma concentrations, ribavirin doses were frequently adjusted initially. The target concentration (10-15 micromol/L) was reached with average daily doses of 170-300 mg ribavirin. Ribavirin induced anaemia was managed with high doses of erytropoietin (20 000-30 000 IU/week). Five of six patients became hepatitis C virus (HCV)-RNA negative during treatment, but four relapsed post-treatment; one is HCV-RNA negative. Hence ribavirin, in combination with IFN-alpha, can be used to treat dialysis patients with HCV. However, this requires reduced ribavirin doses and close monitoring of ribavirin plasma concentrations and haemoglobin. Ribavirin-induced anaemia can be managed with high doses of erythropoeitin.

Adult↗

PubMed2001

CD8+ T cells induce medullary thymic epithelium and CD4+CD8+CD25+ TCRbeta- thymocytes in SCID mice.

During T-cell development the transition in the thymus of CD4-CD8- double negative (DN) progenitor T cells into CD4+CD8+ double positive (DP) cells is dependent on the expression of a T-cell receptor (TCR)-beta-chain protein. In this study purified peripheral CD4+ and CD8+ T lymphocytes from the C.B-17 strain of mice were adoptively transferred into syngeneic, neonatal SCID mice, where donor cells resided at constant numbers in thymus from 2 weeks until 10 weeks post cell transfer. In the recipient thymus the CD8+ donor cells outnumbered the CD4+ cells by a factor of three to five and both subsets contained a large fraction of activated cells. During the late phase of treatment, CD8+ T cells induced high numbers of DP thymocytes in the SCID mice, a process accompanied by the maturation of medullary epithelial cells. Such thymic development in the SCID mouse was inhibited by coresiding CD4+ donor T cells. These results indicate a regulatory role by mature peripheral T cells on medullary epithelial growth and thymocyte development in the treated SCID mice.

Adoptive Transfer↗

PubMed2001

K, Fy(a), and Jk(a) phenotyping of donor RBCs on microplates.

BACKGROUND: In many cases, the search for compatible blood for patients with clinically significant RBC alloantibodies is difficult and time-consuming. To date, it has been considered necessary only to phenotype the blood donors for ABO group and D. There has been long experience with automated routine analysis (ABO, C, c, D, E, and e typing and RBC antibody screening), using robotic dispensers and computerized interpretation of microplate results. The purpose of this study was to explore the possibilities of also phenotyping for K, Fy(a), and Jk(a), as antibodies directed against these antigens (together with Rh antigens) are the most common clinically significant alloantibodies in the Swedish population. STUDY DESIGN AND METHODS: One thousand thirty-one EDTA samples from blood donors were phenotyped for K, Fy(a), and Jk(a) by use of an IAT with PEG on microplates. The findings were compared to those using conventional IAT in tube's and the microcolumn gel test (DiaMed-ID, DiaMed). RESULTS: All typing results with the microplate method were correct. All reactions for K and Fy(a) typing could be interpreted by the computer. The results for Jk(a) were indeterminate in 1.4 percent (14/1031) of the samples. CONCLUSION: The PEG-IAT microplate method gave reliable results that were suitable for routine phenotyping, thus making available a stock of phenotyped blood at reasonable cost, ready for delivery when required.

Blood Donors↗