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Biomedical subjects

R Halvorsen

Publications and source records attributed to R Halvorsen.

51 records · Page 3Linked to original sources
PubMed1988

Role of accessory cells in the activation of pure T cells via the T cell receptor-CD3 complex or with phytohaemagglutinin.

The ability of different subpopulations of blood mononuclear cells to serve as accessory cells in the activation of CD4+ and CD8+ T cells via Ti-CD3 or with phytohaemagglutinin (PHA) was studied. Pure CD4+ or CD8+ T cells did not respond to particle-bound anti-CD3 monoclonal antibodies (MoAb) or PHA, whereas responses were seen when non-T cells served as accessory cells. Removal of class II-positive cells from peripheral blood mononuclear cells (PBMC) or from non-T cells diminished, but did not completely abolish, the responses in both T cell subsets, indicating that the accessory cells are mainly found among the class II-positive cells. However, the class II molecules themselves were not involved, as demonstrated in antibody-blocking experiments. Removal of monocytes decreased the ability of non-T cells to serve as accessory cells for both CD4+ and CD8+ cells in PHA activation. In contrast, the removal of monocytes resulted in an enhanced activation by anti-CD3 MoAb in CD4+ T cells, while the activation of CD8+ T cells was less affected. Positively selected B cells were effective accessory cells in anti-CD3 and PHA activation. Furthermore, Epstein-Barr virus (EBV)-transformed B cell lines were very potent accessory cells both in anti-CD3 and PHA activation of T cells, and showed the strongest accessory cell function observed in this system on a per cell basis.

Antigen-Presenting Cells↗
PubMed1988

Requirements for phytohaemagglutinin activation of resting pure CD4+ and CD8+ T cells.

We have utilized a new method for obtaining highly purified cells using positive selection by immunomagnetic separation to study the conditions required for phytohaemagglutinin (PHA) activation of pure T4 and T8 cells. In the presence of accessory cells (AC), a comparable proliferative response was obtained in the two subsets. In the absence of AC, PHA induced low levels of interleukin 2 (IL-2) receptor expression as well as responsiveness to IL-2 in both T4 and T8 cells. If AC or 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were also present, IL-2 production and DNA synthesis were seen in both subsets. A short preincubation with PHA 'primed' T cells for subsequent responsiveness to IL-2 or TPA, while preincubation with TPA did not induce response to PHA. Thus, PHA alone is sufficient for the first step of T cell activation leading to IL-2 receptor expression. The second step leading to IL-2 production, is dependent on direct interaction with AC in the presence of PHA. While T8 cells are dependent on help by T4 cells for proliferation to occur during stimulation with antigen, in PHA stimulation the requirements for activation and proliferation seem to be identical for T4 and T8 cells.

Antigen-Presenting Cells↗
PubMed1987

Effects of examination stress on some cellular immunity functions.

The effects of examination stress on some lymphocyte subpopulations and cellular immune responses are reported. Twelve undergraduate students of psychology in examination term were tested six weeks before the written examination (phase I), one day before the first or second examination day (phase II) and 12-14 days after the examination (phase III). A comparable control group of students not in examination was assessed in parallel in phase II. The percentage of circulating monocytes increased in phase II in the examination group whereas the percentage of large (probably activated) CD4 and CD8 cells decreased. There was also a decrease in the number of cells expressing the IL-2 receptor in phase II. The proliferative response of T-cells to antigens, mitogens and allogeneic cells decreased from phase I to phase III. Thus, acute examination stress has a detectable influence on certain cellular immunological functions.

Adult↗
PubMed1987

Biological equilibration of allergen preparations: methodological aspects and reproducibility.

A method for biological equilibration (BE) of allergen reference preparations using the skin-prick test (SPT) method and histamine HCl 10 mg/ml as reference substance (reference method), was evaluated. The precision was low for weals less than 10 mm2. The slope (log weal area/log concentration) of allergen and histamine did not vary significantly between investigators and allergens. The median slopes were 0.39 (n = 384) and 0.34 (n = 397), for allergen and histamine, respectively (P less than 0.01). The concentration of allergen eliciting a weal of the same size as that of histamine HCl 1 mg/ml (Chl) in the median sensitive patient, 1000 Biological Units/ml (BU/ml), did not vary significantly between clinics/geographical regions (grasses, mites and moulds). As BE is repeatable between regions, BUs estimated by this method are generally valid. A high correlation (r = 0.91, P less than 0.001) was found between the median Chl as estimated with histamine 1 and 10 mg/ml as reference substance, respectively. Thus, this reference method for BE is valid. The precision of the SPT method with histamine HCl 1 mg/ml is not as good as with 10 mg/ml, which is therefore recommended as the reference concentration.

Adolescent↗
PubMed1987

Activation of resting, pure CD4+, and CD8+ cells via CD3. Requirements for second signals.

We studied the requirements for secondary activation signals in pure CD4+ and CD8+ T cells after stimulation with anti-CD3 antibodies. Stimulation of CD4+ or CD8+ cells with anti-CD3 monoclonal antibodies (MoAb) bound to polystyrene monosized particles never resulted in a proliferative response. However, DNA synthesis was observed when recombinant interleukin 2 (IL-2) or other secondary signals, such as those provided by phorbol myristate acetate (PMA) or autologous accessory cells (AC), were also added. These secondary signals were not in themselves capable of inducing DNA synthesis in the absence of particle-bound anti-CD3. We also found that the signals provided by AC may be dependent on the activation state of these cells. Thus, the effects of accessory cells were enhanced by a factor present in fetal calf serum (FCS), most likely endotoxin or lipopolysaccharide (LPS), which alone, however, were not able to activate T cells, even in the presence of particle-bound anti-CD3. Recombinant IL-1 over a broad dose range was unable to replace PMA or activated AC after stimulation with particle-bound anti-CD3. Purified CD4+ and CD8+ T cells behaved identically in all the experiments, indicating that the basic mechanisms for activation in the two T-cell subsets are identical.

Antibodies, Monoclonal↗
PubMed1986

Role of chest CT in non-Hodgkin lymphoma.

A retrospective study of 48 patients with non-Hodgkin lymphoma (NHL) who underwent 54 computed tomographic (CT) examinations of the chest evaluated the role of chest CT in the management of this disease. Of 18 cases in which chest radiographs were not indicative of NHL, CT scans showed abnormalities consistent with NHL in five (28%). Of 11 cases where radiographs were questionable, CT confirmed NHL in five (45%) and excluded it in six (55%). Of 25 cases where radiographs were consistent with NHL, CT confirmed the findings in 23 (92%) and added information in all 25. Chest CT affected management in eight of 25 treated and five of 19 untreated patients. It appears to be useful in untreated patients with stage I or II NHL but no definite radiographic abnormalities, or with abnormal radiographs but no extrathoracic spread, and in treated patients with questionable radiographs. CT is not helpful in untreated patients with stage III or IV NHL or treated patients with normal radiographs.

Adolescent↗
PubMed1986

T cell responses to a Dermatophagoides farinae allergen preparation in allergics and healthy controls.

We have studied possible differences between mite-allergic individuals and healthy controls in their T cell proliferation and T cell surface markers after in vitro stimulation with a Dermatophagoides farinae allergen preparation. No significant differences were found between the two groups in 3H-thymidine incorporation in T cells after 7 days in culture with allergen- and antigen-presenting cells. The frequencies of allergen-reactive T cells determined by limiting dilution were also similar in the two groups. Finally, no differences were found in surface markers on allergen-activated T cells from mite-allergic and healthy blood donors using a variety of monoclonal antibodies reactive with T cell subsets and activation antigens. Our conclusion is that with the D. farinae preparation employed in this investigation and using T cells prepared from peripheral blood no significant differences were seen between mite allergics and controls.

Allergens↗
PubMed1984

A new, purified Dermatophagoides farinae allergen preparation. Evaluation with SPT and RAST techniques.

A purified, standardized and characterized allergen preparation of the house dust mite Dermatophagoides farinae (Df) was evaluated by skin prick test (SPT) and radioallergosorbent test (RAST) in 88 subjects. Skin reactions to the purified Df preparation and a corresponding crude Df preparation were compared. SPT was also performed with a crude Dermatophagoides pteronyssinus (Dpt) preparation to compare reactions obtained with the two mite preparations. By SPT the purified Df allergen preparation was representative of the crude Df preparation (r = 0.78) and the correlation between skin reactions to Df and Dpt was high (r = 0.78). The concordance between results obtained with RAST and SPT techniques with the purified Df preparation was high (84%). The purified D. farinae preparation was well tolerated and is well suited for SPT.

Allergens↗
PubMed1981

Tumors of the pubis: an analysis by probabilities.

Three patients with a tumor of the pubis are presented (an aneurysmal bone cyst, a Ewing's tumor and a mesenchymal chondrosarcoma). The concept of a probability index is described and the three pubic tumors are used to demonstrate its role in the radiologic evaluation of bone tumors.

Adolescent↗
PubMedDate not supplied

Analysis of air contrast barium enema, computed tomographic colonography, and colonoscopy: prospective comparison.

BACKGROUND: The usefulness of currently available colon imaging tests, including air contrast barium enema (ACBE), computed tomographic colonography (CTC), and colonoscopy, to detect colon polyps and cancers is uncertain. We aimed to assess the sensitivity of these three imaging tests. METHODS: Patients with faecal occult blood, haematochezia, iron-deficiency anaemia, or a family history of colon cancer underwent three separate colon-imaging studies--ACBE, followed 7-14 days later by CTC and colonoscopy on the same day. The primary outcome was detection of colonic polyps and cancers. Outcomes were assessed by building an aggregate view of the colon, taking into account results of all three tests. FINDINGS: 614 patients completed all three imaging tests. When analysed on a per-patient basis, for lesions 10 mm or larger in size (n=63), the sensitivity of ACBE was 48% (95% CI 35-61), CTC 59% (46-71, p=0.1083 for CTC vs ACBE), and colonoscopy 98% (91-100, p<0.0001 for colonoscopy vs CTC). For lesions 6-9 mm in size (n=116), sensitivity was 35% for ACBE (27-45), 51% for CTC (41-60, p=0.0080 for CTC vs ACBE), and 99% for colonoscopy (95-100, p<0.0001 for colonoscopy vs CTC). For lesions of 10 mm or larger in size, the specificity was greater for colonoscopy (0.996) than for either ACBE (0.90) or CTC (0.96) and declined for ACBE and CTC when smaller lesions were considered. INTERPRETATION: Colonoscopy was more sensitive than other tests, as currently undertaken, for detection of colonic polyps and cancers. These data have important implications for diagnostic use of colon imaging tests.

Barium Sulfate↗
PubMedDate not supplied

Effect of increasing current and decreasing blood flow for transcatheter electrocoagulation (TCEC).

Arterial occlusion by direct-current transcatheter electrocoagulation (TCEC) has been developed experimentally and used successfully in clinical situations. The major shortcoming of the technique has been the lengthy time necessary for occlusion of larger arteries. In the present study we attempted to decrease the time necessary for TCEC occlusion of the renal and femoral arteries of heparinized mongrel dogs. The results showed that the occlusion time could be significantly decreased, either by increasing the TCEC current from 15 ma to 30 or 60 ma, or by using a Meditech balloon catheter to occlude the artery during TCEC. The combination of higher current and simultaneous balloon occlusion consistently produced permanent occlusion of arteries up to 7 mm in diameter in 15 minutes or less. Balloon occlusion with TCEC is significantly faster than without this modification and makes the technique of TCEC more applicable for human use and for continued experimental study than any previous refinements.

Animals↗
PubMedDate not supplied

Tidal flow volume loops and inflammatory indicators in small children.

Serum eosinophilic cationic protein (sECP) serum myeloperoxidase (sMPO) and tidal flow volume loops were measured in 41 awake children with at least two episodes of bronchopulmonary obstruction, at least 3 weeks after an acute episode, and in 38 control children, all below 2 years of age. Reversibility to salbutamol was assessed in 26 cases and 24 controls. The baseline ratio of time to peak flow to total expiratory time (Tpef/Te) was significantly lower in cases (0.21) than in controls (0.33). sECP was significantly higher in cases (21.9 micrograms/l) than in controls (14.0 micrograms/l), and correlated significantly (r = 0.70) with the percentage change in Tpef/Te from before to after salbutamol. sMPO did not differ significantly between the two groups.

Airway Obstruction↗