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Biomedical subjects

A Larsson

Publications and source records attributed to A Larsson.

At least 19 recordsLinked to original sources
PubMed1992

Chicken antibodies: a tool to avoid interference by complement activation in ELISA.

MicroELISA plates coated with mammalian IgG will activate the human complement system. It has been shown that this activation of the complement system may interfere in solid-phase immunometric assays, and that there is a difference between IgG from different species and between different IgG subclasses in their ability to activate the human complement system. We have studied the ability of mammalian IgG and avian IgG to activate the human complement system. We show that chicken IgG do not activate the human complement system, and chicken IgG can thus be used in solid-phase immunometric assays to reduce interference by complement activation.

Animals↗
PubMed1992

Studies of fibrinogen binding to platelets by flow cytometry: an improved method for studies of platelet activation.

Platelet function is dependent upon membrane receptors and their interaction with other proteins. Platelet activation appears to cause a structural change of the glycoprotein IIb/IIIa complex that exposes the fibrinogen binding site, which subsequently binds fibrinogen. Fluorescence-activated flow cytometry (FACS) is an efficient method for studying membrane proteins. Flow cytometry gives single-cell data, allowing the detection of only a small proportion of labelled platelets in whole blood without any washing steps. One problem with this method is that the labelled antibodies and the antigen, if present in plasma, form an immune complex, which may cause false positive reactions due to interaction between mammalian IgG and Fc gamma receptors on the platelets. We show that immune complexes with chicken IgG do not activate human platelets. We have developed a method for measuring platelet-bound fibrinogen in whole blood and platelet-rich plasma utilising fluorescein isothiocyanate (FITC)-conjugated chicken antibodies directed towards human fibrinogen. As low as 1% activated platelets could be detected without interference from Fc-interactions.

Adenosine Diphosphate↗
PubMed1992

Genetic regulation of human anti-malarial antibodies in twins.

Immune responses to defined antigens may differ between individuals in a population as the reflection of differences in genetic regulation. In experimental animals, variation in responsiveness to a given epitope may be due to major histocompatibility complex (HLA, in humans) class II restrictions, implying serious limitations for the development of subunit vaccines. For human populations, knowledge of the relative importance of genetic as opposed to environmental factors affecting the immune response is scarce. We have compared antibody levels after immunization through repeated infections to a major malarial antigen (Pf155/RESA) in monozygotic twins with those in dizygotic twins, siblings, or unrelated controls. Antibody responses to the intact antigen and to some of its immunodominant epitopes were found to be more concordant within monozygotic twin pairs than in dizygotic pairs or age- and sex-matched siblings living under similar environmental conditions. The results support the conclusion that the antibody responses were genetically regulated. When the responses were assessed for possible associations with different HLA class II DRB, DQA, and DQB alleles had haplotypes, no associations were found. This suggests that the regulation of the Pf155/RESA antibody responses seen in this study reflects the impact of factors encoded by genes outside the HLA class II regions.

Adolescent↗
PubMed1992

Does the shunt opening pressure influence the effect of shunt surgery in normal pressure hydrocephalus?

Thirteen patients with normal pressure hydrocephalus were operated upon with an externally maneuverable shunt system (Sophy SU8) in order to investigate its influence on clinical outcome, intracranial pressure and cranial CT parameters. The opening pressure was set at high at surgery and lowered stepwise at intervals of three months to medium and low. The clinical condition, intracranial pressure and cranial CT parameters were examined at the end of the 3 months interval on each pressure level. The patients improved within the first 3 months inspite of an unchanged mean intracranial pressure and remained in a stable clinical condition during the rest of the study period. The intracranial pressure was significantly reduced at 9 months. The ventricular index, Evans index, temporal horn and third ventricle width were reduced 3 months post-operatively and did not change significantly during the rest of the study. The pre-operative third ventricle width was correlated to high psychometric test results after shunt surgery. Reduction in ventricular index, Evans index and third ventricle width after surgery correlated to improvement in psychometric scoring. The clinical improvement after shunt surgery for normal pressure hydrocephalus is seen within 3 months and is independent of the adjusted valve pressure.

Aged↗
PubMed1992

Salivary gland involvement in autoimmune thyroiditis, with special reference to the degree of association with Sjögren's syndrome.

From a total of 63 patients with autoimmune thyroiditis, 19 cases were further investigated to determine the degree of concomitant morphologic and functional salivary gland changes. For comparison, 21 of a total of 28 cases of primary Sjögren's syndrome were also examined. Of the 19 cases of autoimmune thyroiditis, 11 showed various degrees of salivary gland involvement on the basis of an analysis of lower lip salivary gland biopsy specimens, scintigraphy of the parotid, and unstimulated whole sialometry. Six of these cases fulfilled the criteria of primary Sjögren's syndrome. A remarkably high proportion of dark-staining acini was observed in the lower lip biopsy specimens of our patients with thyroiditis (8 of 19, 42%) and less among our patients with primary Sjögren's syndrome (5 of 21, 24%). We conclude that significant involvement of salivary glands may occur in cases of autoimmune thyroiditis, which indicates that common mechanisms may frequently be operative in the development of thyroid and salivary gland immune disease.

Adult↗
PubMed1992

Chicken anti-protein A for the detection and capturing of protein A from Staphylococcus aureus in the presence or absence of mammalian IgG.

A sandwich-ELISA for the detection of protein A from Staphylococcus aureus (SpA) is described, using chicken anti-protein A as a capture antibody and its alkaline phosphatase conjugate for the detection of bound protein A. Traditionally, protein A is detected by its binding to the Fc part of a detector antibody. This binding will be influenced by the presence of other IgG in the protein A solution. However, SpA does not react with the Fc part of chicken IgG, and it is thus possible to detect protein A in IgG containing solutions, such as eluates from protein A-columns. The method can be used to detect 1 x 10(-7) g protein A/l in the presence of serum. The method is more sensitive if no serum or IgG is present in the solution.

Animals↗
PubMed1992

Chicken antibodies: a tool to avoid interference by human anti-mouse antibodies in ELISA after in vivo treatment with murine monoclonal antibodies.

Human anti-murine antibodies (HAMA) can be found in serum of many patients who have received murine monoclonal antibodies for diagnosis or therapy. These antibodies are known to give false positive results in sandwich-type assays (e.g. ELISA or RIA). This interference problem will increase in the future as more patients are treated with murine monoclonal antibodies in vivo. HAMA can also be found in sera from patients that has not been treated with monoclonal antibodies. In this work we have studied the interference of HAMA in sandwich ELISAs containing antibodies from different species. HAMA, present in the sample, may react both with the capture antibody and the detection antibody in these assays to give a false positive reaction. HAMA did not react with chicken IgG, and if one of (or both) the capture and detection antibody was of avian origin, the interference of HAMA in sandwich assays could be avoided.

Animals↗
PubMed1992

Pulmonary effects of body position, PEEP, and surfactant depletion in dogs.

The influence of position (sphinx, lateral, supine), surfactant depletion, and different positive end-expiratory pressure (PEEP) on functional residual capacity (FRC), series dead space (VdS) and compliance of the respiratory system (Crs) were evaluated in five dogs. Ventilation homogeneity as measured by an index (multiple breath alveolar mixing efficiency), oxygenation, and cardiovascular hemodynamics were additionally examined. The dogs were anesthetized with halothane, paralyzed, and mechanically ventilated. FRC and VdS were found to be notably large in dogs, 45 +/- 8 ml/kg and 6 +/- 1 ml/kg, respectively. FRC and ventilation homogeneity were improved in the sphinx position (prone position with upright head). Surfactant depletion by lung lavage with 37 degrees C saline caused an immediate and stable decrease in FRC, Crs, and oxygenation (P less than 0.05, respectively) for about 5 h without marked effects on the circulatory system. FRC and VdS increased with increasing PEEP. At the highest PEEP, 10 cmH2O (1 kPa), Crs decreased (P less than 0.05) and ventilation became more uneven, indicating alveolar overdistension.

Animals↗
PubMed1992

Elimination of apparatus dead space--a simple method for improving CO2 removal without increasing airway pressure.

During mechanical ventilation the apparatus dead space can be eliminated by insufflating through one lumen of a tracheal double-lumen tube and allowing expiration through the other. In six intravenously anesthetized pigs, this technique resulted in an 18% (1 kPa) decrease in PaCO2 compared with insufflating through both lumens (32 ml rebreathing volume). Oxygenation, airway pressures, and tidal volumes were unchanged. Flushing the trachea with fresh gas during the expiratory phase did not improve the efficiency of ventilation. It is concluded that elimination of apparatus dead space improves CO2 removal without increasing airway pressures and tidal volumes, and it is suggested that minimization of apparatus dead space should be tried before more advanced ventilatory modes are considered.

Animals↗
PubMed1992

Functional residual capacity and ventilation homogeneity in mechanically ventilated small neonates.

A modification of a computerized tracer gas (SF6) washout method was designed for serial measurements of functional residual capacity (FRC) and ventilation homogeneity in mechanically ventilated very-low-birth-weight infants with tidal volumes down to 4 ml. The method, which can be used regardless of the inspired O2 concentration, gave accurate and reproducible results in a lung model and good agreement compared with He dilution in rabbits. FRC was measured during 2-4 cmH2O of positive end-expiratory pressure (PEEP) in 15 neonates (700-1,950 g), most of them with mild-to-moderate respiratory distress syndrome. FRC increased with body weight and decreased (P less than 0.05) with increasing O2 requirement. Change to zero end-expiratory pressure caused an immediate decrease in FRC by 29% (P less than 0.01) and gave FRC (ml) = -1.4 + 17 x weight (kg) (r = 0.83). Five minutes after PEEP was discontinued (n = 12), FRC had decreased by a further 16% (P less than 0.01). The washout curves indicated a near-normal ventilation homogeneity not related to changes in PEEP. This was interpreted as evidence against the presence of large volumes of trapped alveolar gas.

Body Weight↗
PubMed1992

Glycerol production in subcutaneous adipose tissue in lean and obese humans.

To estimate the regional subcutaneous glycerol production rate in normal and obese humans, the venous arterialized plasma glycerol, interstitial glycerol in the subcutaneous adipose tissue together with adipose tissue blood flow (ATBF, ml/100 g.min) were measured in the postabsorptive state and for 2 h after ingestion of 100 g of oral glucose. Eight lean and eight obese men with normal oral glucose tolerance tests were investigated with the subcutaneous microdialysis technique and 133Xe clearance. In the postabsorptive state, the interstitial glycerol concentrations in lean and obese subjects were 170 +/- 21 vs. 282 +/- 28 microM (P less than 0.01) and 156 +/- 23 vs. 225 +/- 12 microM (P less than 0.05) in the abdominal and femoral subcutaneous adipose tissue, respectively. The corresponding arterial glycerol levels were 54 +/- 4 vs. 75 +/- 14 microM (NS). Abdominal ATBF was greater in lean subjects (3.2 +/- 0.6 vs. 1.6 +/- 0.3; P less than 0.05), whereas femoral ATBF was similar in both groups (2.7 +/- 0.4 vs. 2.4 +/- 0.7). Estimated mean local glycerol release (mumol/100 g.min) was similar in the lean and obese group (0.16 +/- 0.03 vs. 0.20 +/- 0.05 and 0.18 +/- 0.02 vs. 0.17 +/- 0.04) in the abdominal and femoral site, respectively. We conclude that glycerol production from the subcutaneous tissue is increased in obesity, irrespective of adipose tissue distribution. This enhancement is due to the increased adipose tissue mass.

Adipose Tissue↗
PubMed1992

Natural surfactant instilled in premature lambs increases lung volume and improves ventilation homogeneity within five minutes.

The immediate effects on lung volume, ventilation homogeneity, and lung mechanics of tracheal instillation of surfactant were studied in premature lambs, gestational age 120-122 d, with respiratory distress syndrome. Six lambs received surfactant by tracheal instillation 25 min after delivery by cesarean section; five received only vehicle and served as controls. The lambs were studied for 60 min thereafter. Functional residual capacity was measured with a computerized tracer gas washin-washout technique using sulfur hexafluoride as tracer gas. A measure of ventilation inhomogeneity (pulmonary clearance delay) was also calculated from the washout curves. Pressure-volume curves were studied with an interrupter technique during deflation of the lungs from an airway pressure of 30 cm H2O. In the surfactant group, arterial oxygenation and ventilation homogeneity improved within 5 min of giving surfactant; major increases in functional residual capacity, vital capacity, and compliance occurred within 5 to 20 min and were followed by gradual further improvements. The pressure-volume curve thus increased in amplitude and became steeper, but the lung volumes at various inflation pressures, and compliance, remained constant when expressed as fractions of total lung capacity volume. It is concluded that an improvement in lung volume, respiratory mechanics, and ventilation homogeneity occurs very soon after surfactant instillation and that there is a phase of successive further improvement over the next hour. Although the amplitude of the pressure-volume curve varied considerably, its basic shape varied little. This suggests that opening of new distal airways by surfactant predominated over changes in the mechanics of already aerated lung regions.

Animals↗
PubMed1992

Primary Sjögren's syndrome in patients with multiple sclerosis.

The relationship between multiple sclerosis (MS) and primary Sjögren's syndrome (PSS) is ambiguous; it was suggested that some patients diagnosed with MS may instead have PSS. In a recent epidemiologic study, the prevalence of PSS was 2.7% in southern Sweden. We randomly selected 30 patients with definite MS from our patient population and investigated them for evidence of PSS according to the Copenhagen criteria. One patient had clinical symptoms compatible with PSS and also fulfilled the Copenhagen criteria. In addition, five patients had keratoconjunctivitis sicca, one had xerostomia, and three had histopathologic evidence of sialadenitis in the lower lip salivary glands. However, one of these findings alone is not sufficient to support the diagnosis of PSS. We conclude that MS and PSS may coexist in the same individual, but PSS is not more common among MS patients than expected in the general population.

Antibodies, Antinuclear↗
PubMed1992

Viability, prostaglandin E2 production, and protein handling in normal and inflamed human colonic mucosa cultured for up to 48 h in vitro.

Human colonic mucosa obtained from colon cancer resections ('normal') and from colectomies owing to ulcerative colitis (inflamed) were cultured for up to 48 h in vitro. The 3H-leucine incorporation in normal tissue decreased to 52% (p less than 0.001) at 48 h compared with 24 h. The protein synthesis in normal but not in inflamed explants was significantly (p less than 0.01) improved at 48 h, reaching 72% of the 24-h value, on additions of insulin and the protease inhibitors aprotinin, soyabean trypsin inhibitor, and N alpha-tosyl-L-lysine chloromethyl ketone to the culture medium. Inflamed tissue had significant protein losses of 15% after 24 h and 29% after 48 h in culture, and the excretion of precipitable 3H-leucine-labelled proteins could be as high as 20%/24 h. A slight protein loss was observed in normal tissue after 48 h in culture, but the excretion of labelled proteins was very low (3%). The prostaglandin E2 (PGE2) production in both normal and inflamed tissue displayed an increasing non-linear pattern with time in culture, with higher values for inflamed tissue. The PGE2 release profiles and the differences in basic protein metabolism between normal and inflamed human colonic biopsy specimens in culture might reflect important characteristics of the inflammatory process.

Animals↗
PubMed1992

Oral mucosal findings associated with chewing tobacco in Sweden--a clinical and histological study.

Twenty men of mean age 51,9 years who used Swedish chewing tobacco as their only tobacco habit were examined for clinical and histological changes. On average they had been chewing tobacco for 10,7 hours daily for 11,3 years. The most common clinical finding was a leukoedema-like change of the buccal mucosa at the site where the quid was held after chewing. Ten subjects showed changes similar to mild snuff-induced ones. Histological findings corresponded well with the clinical ones. It appears that oral mucosal changes associated with chewing tobacco in Sweden are discrete.

Adult↗
PubMed1991

The effect of pancreatic procolipase and colipase on pancreatic lipase activation.

Intestinal fat digestion is carried out by the concerted action of pancreatic lipase and its protein cofactor colipase. Colipase is secreted from pancreas as a procolipase and is transformed into colipase by the trypsin cleavage of the Arg5-Gly6 bond during liberation of an N-terminal pentapeptide. The kinetic parameters for the lipase-colipase system compared to the lipase-procolipase system has been compared using trioctanoin and Intralipid as substrates. It was found that at pH 7.0 the Kmapp using Intralipid as substrate was the same for procolipase and colipase, 0.06 mM and 0.05 mM, respectively. At pH 8.0, however, the Kmapp were different-0.23 mM for procolipase and 0.08 mM for colipase. In a similar way the binding between colipase and lipase had a dissociation constant of 2.4 x 10(-6) M at pH 7.0, while for procolipase--lipase binding the dissociation constant was 4.1 x 10(-6) M with no significant difference. At pH 8.0 the binding between colipase and lipase was stronger, Kd being 2.0 x 10(-7) M, while weaker for procolipase and lipase, Kd being 1.0 x 10(-5) M. It is concluded that at the physiological pH value as is found in the intestine, the activation of procolipase to colipase has no influence on the hydrolysis of trioctanoin or Intralipid in the presence of bile salt.

Animals↗