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Biomedical subjects

G Sandberg

Publications and source records attributed to G Sandberg.

At least 109 records · Page 6Linked to original sources
PubMed1979

Further studies on splenic material inhibiting the growth of lymphocytes in vitro.

A material inhibiting growth of lymphocytes from different lymphoid organs and from different species was purified from calf spleen. A factor with a molecular weight of about 45,000 dal (estimated by gel chromatography) inhibited DNA synthesis and mitosis irreversibly in thymocytes and caused degenerative changes in the nucleus and the cytoplasm of the thymocytes as judged by electron microscopy. However, no decrease in cell number and no increase in dye uptake in a dye exclusion test were found. Growth inhibition was also demonstrated for human melanoma cells, but not for rat liver cells. The cytotoxicity and the lack of absolute lymphocyte specificity of the factor speak against its character as a lymphocyte chalone. A probably identical factor was purified from calf liver, but was not found in extracts of calf thymus.

Animals↗
PubMed1979

Mitotic activity of thymocytes in a synthetic tissue culture medium. Effect of L-alanine.

DNA synthesis in guinea pig thymocytes suspended in RPMI 1640 medium increased to a peak after 4-5 h in culture and was followed by increased mitotic activity, indicating that many thymocytes in S phase proceeded through G2 into mitosis. Addition of L-alanine to the medium markedly increased the DNA synthesis within 1 h and the mitotic frequency from 6 h. The increase in DNA synthesis when L-alanine was present in the medium was thus caused by an increased number of cells in S phase. Human thymocytes cultured in RPMI 1640 for 18 h had a low mitotic frequency. Addition of L-alanine immediately started DNA synthesis in the arrested thymocytes resulting in increased mitotic activity from 6 h later. The results show that L-alanine is a growth factor for guinea pig and human thymocytes and should be included in tissue culture media used for such cells. Growth of thymocytes in vitro was partly synchronized, and the mitotic studies indicated that many cells had entered S phase near the start of incubation.

Alanine↗
PubMed1978

Effect of immunization on the cyclic AMP level and 3H-thymidine incorporation in cultured lymphoid cells.

The cyclic AMP level and the uptake of 3H-thymidine were studied in short-term suspension cultures of guinea pig lymphoid cells. Spleen cells from animals immunized 3 days previously with typhoid vaccine were shown to differ in three respects from the normal cells: (1) The level of cyclic AMP was higher. (2) The cyclic AMP increase following addition of isoproterenol or adenosine was abolished. (3) Isoproterenol (10(-5) to 10(-4) M) stimulated the uptake of 3H-thymidine in cells from immunized animals, while the uptake into normal cells was inhibited by these concentrations. A higher dose of isoproterenol (10(-3) M) inhibited 3H-thymidine uptake in both immunized and normal cells. The results reveal certain biochemical alterations in splenic lymphocytes after immunization. An altered 3H-thymidine uptake may be caused by the modified cyclic AMP metabolism in cells from immunized animals.

Adenosine↗
PubMed1977

Observations on rosette formation by thymocytes and T lymphocytes in guinea pigs. Effect of neonatal thymectomy, irradiation, thymosin, albumin and the influence of cell viability.

Irradiation (300 rad) of guinea pigs and subsequent transfer of bone marrow cells was followed by a decreased frequency of rabbit erythrocyte rosettes (a T lymphocyte marker) in peripheral lymphoid organs. Neonatal thymectomy did not potentiate this effect. A reduced amount of rosette-forming cells was also found in the thymus of irradiated animals. This was not affected by treatment with thymosin in vivo or in vitro, and was probably due to a reduced viability of the cells after irradiation since it was demonstrated that rosette formation among dead thymus cells was significantly less than among living cells. Incubation of normal thymocytes in non-supplemented medium for 2--4 h at 37 degrees C was also followed by a diminished rosette-forming capacity. The addition of thymosin or bovine serum albumin prevented both the decrease of rosette-forming cells and the reduction of viable cells during incubation. Thus, a diminished rosette formation may have been caused by reduced viability after incubation as well as after irradiation. The rosette-forming ability of only some dead thymocytes may reflect different subpopulations.

Animals↗
PubMed1976

The sealed capillary migration technique and thymocyte migration in vitro.

The in vitro migration of thymocytes in sealed capillary tubes was influenced by cell number, temperature, cell viability and oxygen supply. Migration was successively slower over a 24 h period. There was no major influence of gravity or the degree of initial packing of the cells by centrifugation. Migration was inhibited by cytochalasin B, although the cells escaped from this effect after 8 h. A transient stimulatory effect on migration was seen after addition of serum or supernatants from cultured thymocytes. There was no effect of isoproterenol, theophylline or carbacholine. A paradoxic effect was obtained with high doses of some metabolic inhibitors, which produced increased migration in spite of cell death. The technique may be used for studies on lymphocyte migration in vitro, but care must be taken to exclude a toxic influence of added substances, and expected effects should preferably be looked for early after onset of migration, since cell viability is gradually decreased.

Animals↗
PubMed1976

Quantitation of B and T lymphocytes in guinea pigs with evidence for a release of both cell types from the spleen into the blood.

B and T lymphocytes were quantitated in lymphoid organs and in blood of young normal guinea pigs by the use of EAC rosettes and rabbit erythrocyte (RE) rosettes as markers. Special attention was focused on the release of B and T cells from the spleen, estimated from the difference between the content of B and T cells in splenic efferent and afferent blood. The following frequencies of resette-forming cells (RFC) were found. Thymus: 0.3% EAC- and 88% RE-RFC; spleen: 44% EAC- and 46% RE-RFC; lymph nodes: 13% EAC- and 39% RE-RFC; arterial blood: 13% EAC- and 42% RE-RFC, and bone marrow: 2% EAC- and 7% RE-RFC. A fairly large number of cells in the lymph nodes and blood could not be identified by any of the two markers. Some possible explanations for this are discussed. The content of both EAC- and RE-RFC in splenic efferent blood significantly exceeded that in the afferent blood, indicating a release of both B and T cells from the spleen into the blood. The possibility of a release of a third type of mononuclear cell cannot be excluded from the present results.

Animals↗
PubMed1975

Influence of thymectomy, transfer of thymus and bone marrow cells and treatment with thymosin on the depressed splenic release of lymphocytes into the blood after irradiation.

The content of lymphocytes in blood samples from the splenic vein and the splenic artery of guinea pigs was determined and the veno-arterial difference in number of cells was used as measure of the net release of cells from the spleen into the blood. The splenic release of lymphocytes was reduced after whole body irradiation with 300 rad. This reduction could partly be prevented by transfusion of bone marrow cells after irradiation, 10(6) cells being the most effective dose. In thymectomized, irradiated animals the restoration of the splenic release of lymphocytes after irradiation was impaired in comparison with sham-operated animals. In the thymectomized animals the transfusion of 10(6) thymus cells had a restitutive effect on the splenic release of lymphocytes, while transfusion of bone marrow cells or daily treatments with thymosin, alone or combined with transfusion of bone marrow cells, had no such restitutive effect. The results indicate that restoration of the splenic release of lymphocytes into the blood after irradiation is thymus dependent and probably caused by a traffic of lymphocytes from the thymus to the spleen.

Animals↗