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R Halvorsen

Publications and source records attributed to R Halvorsen.

At least 37 records · Page 2Linked to original sources
PubMed1993

[Infectious diseases and physical activity].

Moderate physical activity has a beneficial effect on health. On the other hand, physical and psychological stress may have a suppressive effect on the immune system, implying that intense physical activity may possibly enhance the appearance of infectious diseases. There are no studies showing any effect on the immune system, nor on the frequency of infections, from physical training of low to moderate intensity. However, in several cases, high intensity training has been shown to produce chronic overtraining, which may impair general health. It is suggested that the extreme physical exertion of elite athletic training may suppress the immune system and thus lead to enhanced susceptibility to infectious diseases. Furthermore physical activity during the incubation period of several serious infectious diseases seems to be especially disadvantageous for the course of the disease.

Bacterial Infections↗
PubMed1993

The effect of daily low-dose iron supplements in female blood donors with depleted iron stores: comparison with female non-donors.

Female blood donors with serum ferritin < or = 20 micrograms l-1 and haemoglobin > 120 g l-1 participated in an iron supplement study with two different low-dose supplements in a period without donations. Comparable non-donors served as controls. Serum ferritin, haemoglobin and transferrin were determined. Increases in serum ferritin and in haemoglobin, and decrease in transferrin were highly significant (p < 0.01) in both donor groups. In one of the non-donor groups the increase in serum ferritin and decrease in transferrin were highly significant (p < 0.01), while in the other only transferrin changed significantly (p < 0.03). The increases in serum ferritin and haemoglobin over a 5-month period were significantly higher among donors (p < 0.001) than among non-donors. We interpret the results to mean that the donors have a more efficient iron absorption.

Adult↗
PubMed1991

[The effect of conversion from blood donation to plasma donation on serum ferritin and hemoglobin].

In the present study the effect of a change from whole blood to plasma donation on iron stores is investigated by measuring serum ferritin levels. Paired serum samples from 125 plasma donors showed a significant increase in mean serum ferritin level with plasmapheresis. 76% of the plasma donors showed an increase in serum ferritin. For plasma donors the haemoglobin concentration is not related to serum ferritin level and hence to iron stores, and a change in haemoglobin concentration is not related to a change in serum ferritin. Plasma donation is a good alternative to whole blood donation for fertile women and for blood donors opposed to iron supplements.

Adult↗
PubMed1990

[Pregnancy and iron storage].

We present the results from a study of 97 female blood donors who reappeared for donation after giving birth from nine to 60 months before. The donors answered a questionnaire about number of pregnancies, the time since last pregnancy, iron medication before and during pregnancy, and methods of contraception. Serum ferritin was determined in a blood sample drawn before donation. In this group, mean serum ferritin was 21.5 +/- 14 micrograms/l. In a control group consisting of young women who registered as donors the mean serum ferritin was 39.4 +/- 29.4 micrograms/l. There was a decrease in serum ferritin with increasing age and parity. The mean serum ferritin value was higher among women who had taken iron supplements regularly before and during pregnancy than among women who had not taken iron supplements. The differences were statistically significant for iron supplementation during pregnancy. Iron supplements during pregnancy seem justified, but further information should be obtained about necessary does and appropriate time for starting supplementation.

Adult↗
PubMed1990

[Cholesterol status of blood donors. Motivation for dietary changes and their effects].

We present the results of serum-cholesterol measurements in 956 blood donors and an evaluation of their motivation for dietary changes based on answers to a questionnaire. The mean serum-cholesterol level was 5.5 mmol/l for women and 5.7 mmol/l for men, with an increase in serum-cholesterol with age. Motivation for dietary changes was food, since 85% answered that they would change their diet if their serum-cholesterol was high. 65% of those who knew their serum-cholesterol to be high before this study had changed their diet. 38% of the smokers answered that they would stop smoking if their serum-cholesterol was high. Eight to 14 months later, serum-cholesterol measurements in 201 of the blood donors showed that 72.4% of those with serum-cholesterol greater than 6 mmol/l had changed their diet and that these had reduced their serum-cholesterol by an average 10.6%.

Adult↗
PubMed1990

[The effect of plasmapheresis on IgG and albumin].

Since 1986, we have performed 26,500 plasma donations at the Red Cross and National Hospital Blood Centre. In conjunction with these donations, 4,000 serum samples from 3,400 donors have been tested for IgG and albumin level. 125 donors who donated plasma regularly were studied further. In this group we found a mean reduction in IgG of 0.3 g/l, but no significant reduction in albumin. Even for donors who donate regularly the mean time interval between donations was more than 40 days. Today's recommendation of regular IgG and albumin control is a result of experiences from twice weekly plasma donations in the USA. We conclude that such testing is unnecessary in Norway.

Adult↗
PubMed1990

[Iron status in blood donors evaluated by serum ferritin].

In the present study we have examined serum ferritin in experienced male and female blood donors and in women who had never donated blood before, but had registered at the Blood Centre as future donors. There was no coincidence between low haemoglobin and low s-ferritin when haemoglobin was within normal range. Iron stores (s-ferritin less than 20 micrograms/l) were reduced in 40% of the female blood donors and in 21% the iron stores (s-ferritin less than 10 micrograms/l were completely empty. 10% of the male donors had iron stores, while in 3% the iron stores were empty. Among the females who had not donated blood, 30% had s-ferritin values below 20 micrograms/l and 6% had values below 10 micrograms/l. We conclude that measuring s-ferritin is a better method of identifying individuals at risk for iron depletion than measuring hemoglobins. A combination of longer intervals between donations and iron therapy may prevent depletion of iron stores in blood donors.

Adult↗
PubMed1989

[The effect of exercise and elite athletics on the immune system].

Physical and psychological stress influence immune responses. The influence of physical stress on immunity is through the action of neuro-peptides and other hormones and by way of a direct effect on the cells controlling the immune response. There is little or no evidence that physical activity, i.e. regular exercise without competition has any harmful effects on immunity. On the contrary, some animal studies tend to indicate a beneficial effect of exercise on the immune system. Regular intense training and competitions have been associated with increased morbidity, especially from infections. This may be connected to suppression of cell-mediated and humoral immunity which has been demonstrated in connection with exercising to exhaustion.

Animals↗
PubMed1989

Isolation of functionally active T cell receptor gamma delta-bearing lymphocytes from human peripheral blood.

We have developed a simple method for isolation of functionally active T cell receptor (TCR)-gamma delta positive cells from human peripheral blood, using immunomagnetic separation techniques. After culture with feeder cells and interleukin-2, cells thus isolated showed a CD3+ TCR-alpha beta- phenotype, and stained with antibodies against the TCR-gamma delta complex. The TCR-gamma delta+ cells were functionally active, responding with DNA synthesis when stimulated via their CD3 and CD2 molecules in concert, or when interleukin-2 was added.

Adult↗
PubMed1989

Ability of pure resting CD8+ human T cells to respond to alloantigen.

The ability of highly purified resting human CD8 cells to respond to alloantigens in vitro was examined. Necessary conditions for induction of interleukin 2 receptors (IL-2R), IL-2 production, proliferative responses, and various effector functions were determined. Allogeneic non-T cells induced IL-2R expression in a high proportion of resting CD4 and CD8 cells, but only CD4 cells produced detectable amounts of IL-2. CD8 cells also became IL-2 responsive upon stimulation with purified resting allogeneic CD4 or CD8 cells, indicating that HLA class I+, II- cells alone may initiate activation of resting CD8 cells. The activated CD8 cells needed the presence of simultaneously activated CD4 cells or exogenous IL-2 to be able to synthesize DNA. Effector functions like cytotoxicity, mixed lymphocyte culture (MLC) suppression, or gamma interferon (IFN-gamma) production were also only detectable when the CD8 cells were activated in the presence of IL-2.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Specificity of gamma delta receptor-bearing cytotoxic T lymphocytes isolated from human peripheral blood.

T-cell receptor (TcR)-gamma delta-bearing lymphocytes were isolated from the peripheral blood of two healthy donors by immunomagnetic separation and subsequently cultured. The cell lines generated showed two distinct patterns of cytotoxicity. One TcR-gamma delta + cell line (HG.D) lysed K562 and U937 target cells, three TcR-gamma delta + cell lines lysed Daudi cells, and one TcR-gamma delta + cell line showed a shift from the former to the latter specificity during culture. Cold target inhibition experiments showed that the HG.D effector cells which were cytotoxic against U937 cells also lysed K562 cells. The cytotoxicity against Daudi cells was strongly inhibited by monoclonal antibodies (MoAb) against the CD3 complex, whereas the cytotoxicity of the HG.D cell line against K562 and U937 was unaffected by such antibodies. The cytotoxicity against Daudi cells was also strongly inhibited in the presence of anti-TcR-gamma delta MoAb. However, in two of the Daudi-specific cell lines, strong cytotoxicity against K562 cells was induced by anti-TcR-gamma delta MoAb. Anti-LFA-1 MoAb caused only a partial inhibition of cytotoxicity, while anti-CD2 and anti-TcR-alpha beta MoAb were found to have no effect. The results indicate that human gamma delta receptor-bearing T cells demonstrate a certain degree of target cell specificity, and that recognition of some target cells may be mediated through the TcR-gamma delta.

Adult↗
PubMed1988

A simple and sensitive bioassay for the detection of IL-2 activity.

A simple, one-step quantitative assay for the detection of biologically active interleukin-2 (IL-2) is described. It is based on culture of pure CD3+ T cells which have been positively selected from blood mononuclear cells by particle (M450)-bound anti-CD3 monoclonal antibody (mAb). During culture, activation of the T cells via CD3 will occur, leading to expression of IL-2 receptors but not IL-2 production. By adding IL-2 a proliferative response is evoked, giving a linear dose-response curve for IL-2 concentrations between 0.01-20 U/ml. The cells were unresponsive to IL-1, IL-4, tumor necrosis factor alpha (TNF-alpha), interferon-alpha (IFN-alpha), IFN-gamma, phytohemagglutinin and concanavalin A. The responsiveness to IL-2 was enhanced by TNF-alpha and inhibited by IFN-alpha, while the other tested lymphokines and mitogens did not influence the proliferative response. Antibodies to IL-2 and to IL-2 receptor suppressed the IL-2 response in a dose-dependent manner. The method is both simple and specific, and obviates the necessity for keeping assay cells in long term culture.

Antibodies, Monoclonal↗
PubMed1988

Accessory cell-dependent T-cell activation via Ti-CD3. Involvement of CD2-LFA-3 interactions.

The activation of resting T cells to interleukin 2 (IL-2) production and DNA synthesis via Ti-CD3 is dependent on accessory cells (AC). Using positively selected, resting T cells activated with particle-bound anti-CD3, we investigated the ability of various cell lines to function as AC. We found that cell lines able to act as AC all expressed LFA-3, while cell lines not expressing LFA-3 were unable to provide AC signals. This applied to CD3+, CD4+, and CD8+ T cells. Sheep red blood cells (SRBC), which express LFA-3-like molecules, also had a weak, but significant AC function in this test system. Both CD4+ and CD8+ T cells activated with particle-bound anti-CD3 could be induced to enter DNA synthesis in the absence of AC when monoclonal antibodies reacting with CD2 were present instead of AC. IL-2 production could be detected in the latter cultures but not when positively selected CD3+ or CD2+ T cells were cultured alone. Our data suggest that activation of resting T cells via CD3 will lead to IL-2 receptor expression, while the interactions between LFA-3 and its ligand CD2 provide the necessary secondary signals for IL-2 production and induction of DNA synthesis.

Animals↗
PubMed1988

Induction of interleukin-2 production in CD4+ and CD8+ T-cell subsets after activation via CD3 and CD2.

The activation signals necessary for interleukin-2 (IL-2) receptor induction, IL-2 production, and DNA synthesis in resting T cells were investigated. IL-2 receptors were induced after activation via CD2 or CD3 alone, while IL-2 production in both CD4+ and CD8+ T cells required activation via both CD3 and CD2. The sequence of activation signals via CD3 and CD2 was shown to be important since DNA synthesis was induced when the primary activation signal was delivered via CD3, and the CD2 signal within 8 h. In contrast, no DNA synthesis was demonstrated when the primary activation signal was delivered via CD2 and the CD3 signal later. Ciclosporin A (CyA) inhibited T-cell DNA synthesis after activation via CD2 and CD3. The inhibition seemed to be due to the prevention of IL-2 synthesis.

Antigens, Differentiation, T-Lymphocyte↗