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Biomedical subjects

A Horst

Publications and source records attributed to A Horst.

At least 37 records · Page 2Linked to original sources
PubMed1984

Transport of [125I] IgG and [125I] ovalbumin between lymphocyte-like and macrophage-like rat spleen cells: chromatin binding.

Spleen cells from rats were incubated for 10 min in Eagle's medium containing [125I] IgG or [125I] ovalbumin. Lymphocyte-like and macrophage-like cells were separated by centrifugation in Ficoll-metrizoate solution (d = 1.095). Control spleen cells were incubated in Eagle's medium without [125I] IgG or [125I] ovalbumin and both subpopulations were separated analogically. Lymphocyte-like cells labelled with [125I] IgG or [125I] ovalbumin were incubated for 10 min with control macrophage-like cells and labelled macrophage-like cells with control lymphocyte-like cells. After the incubation time all subpopulations were separated again in Ficoll-metrizoate solution. Radioactivity of [125I] IgG or [125I] ovalbumin was found in cytoplasmic fraction, sap protein fraction (nucleoplasm) and chromatin of control lymphocyte-like and macrophage-like cells. It may be concluded that transport of these potential antigenic compounds occurs directly in lymphocyte-like and macrophage-like cells as well as transport between these two subpopulations.

Animals↗
PubMed1983

Antigen binding with chromatin of immunocompetent cells.

Binding of [125I] IgG to chromatin of spleen cells was studied in vivo, in vitro and to isolated chromatin. In vivo, maximal saturation of chromatin occurred 1 day after immunization (1.3 X 10(12) molecules per spleen, 10(8) cells). At the same level the antigen bound to chromatin in vitro. Binding of [125I] IgG with isolated chromatin was dependent on antigen concentration.

Animals↗
PubMed1983

Changes of non-histone protein fractions during embryonic development of chicken liver.

Electrophoretic profiles of [3H] tryptophan labelled non-histone chromatin protein fractions of liver were studied during the embryonic development of chicken. In embryonic chicken liver a characteristic of non-histone chromatin protein fraction K (molecular weight 18 000) was synthesized. The synthesis of this fraction changed quantitatively during various days of chicken development. The greatest changes of non-histone chromatin proteins were observed on the 21st day of development (day of hatch), when besides the synthesis of a group of low molecular weight proteins (fractions J,K,L,M) the synthesis of fractions of non-histone proteins of high molecular weight was also higher than on other days. Significantly, a high molecular weight fraction, not analyzable in 7.5% PAGE, was present only in the early days (7th-12th) of our investigations.

Age Factors↗
PubMed1982

Specific non-histone protein fractions associated with 'active' chromatin in immunized rats.

Non-histone proteins of normal, non-immunized rats and rats immunized with mouse spleen cells were labelled with three different amino acids: [3H]tryptophan, [3H]methionine and [3H]leucine. Chromatin was fractionated at increasing salt concentrations into three fractions: 0.35 M NaCl-soluble, 2 M NaCl-soluble and residual. Non-histone protein fractions F (Mr 12 000) and H (Mr 3 000) highly labelled with [3H]tryptophan, lower with [3H]methionine but not with [3H]leucine, were present mainly in the residual fraction. After DNAse II treatment non-histone protein fractions F and H disappeared in chromatin fractions and were present in Mg2+ soluble fractions which suggests that, similar to the fractions I (Mr below 3 000) and B (Mr 120 000) described previously (5), these fractions may be associated with active transcribed genes.

Animals↗
PubMed1982

Differences in salt solubility, DNase II sensitivity and template activity of chromatin from antibody synthesizing spleen cells and myeloma cells RPC 5 and ABPC 22.

Chromatin from myeloma cells RPC5 and ABPC22, and from spleen and liver cells of immunized rats and mice, and mice bearing tumours, was fractionated into three part: 0.35 M NaCl-soluble, 2 M NaCl-soluble and residual. The residual fraction from myeloma cells differed from that of immunized spleen cells, described previously as containing unique sequences (5), in that it has higher protein and DNA levels, lower DNase II sensitivity and lower template activity.

Animals↗
PubMed1981

Non-histone chromatin proteins during various stages of activity of immunocompetent cells.

Qualitative and quantitative changes of non-histone chromatin proteins of spleen cells during the primary immune response to sheep red blood cells and aggregated human gamma-globulin were described. Synthesis of non-histone chromatin proteins was measured by labelling with 3H-tryptophan during culture of spleen cells in vitro. Chromatin was isolated and labelled proteins were analysed by polyacrylamide gel electrophoresis. During the immune response to both antigens in chromatin of spleen cells three new fractions of non-histone chromatin proteins were synthesized: fractions F1 - M = 12 000 and H - M = 3 000, specific for sheep red blood cells and fractions I1 - M less than 3 000 and B - M = 120 000, specific for human gamma-globulin. The third antigen-non-specific fraction was synthesized at the time when the primary immune reaction was finishing. These new fractions were synthesized only in one of the analysed subpopulations of spleen cells. In thymocytes (non-fully-differentiated lymphoid cells) all these fractions were absent. Changes of non-histone chromatin proteins in thymocytes during the immune response were similar to those found during stimulation to proliferation by phytohemagglutinin in vitro.

Animals↗
PubMed1981

Incorporation of various amino acids into non-histone chromatin protein fractions of spleen cells of mice immunized with IgG.

Incorporation of three various amino acids ([3H]-tryptophan, [3H]-methionine or [3H]-leucine) into the non-histone chromatin proteins, synthesized in spleen cells of mice after immunization with IgG, is described. Two new fractions of non-histone chromatin proteins (I-mol. wt. below 3 000 and B1-mol. wt. about 120 000), appearing during the immune reaction were labelled with [3H]-tryptophan and [3H]-methionine but not with [3H]-leucine. Synthesis of these fractions was observed only at the time of maximal RNA synthesis. A suggestion about the role of tryptophan and methionine in non-histone chromatin proteins in the regulatory processes of gene activation is discussed on the basis of their selective binding to DNA.

Amino Acids↗
PubMed1981

Non-histone proteins in fractionated chromatin before and after DNAse II treatment.

Chromatin from spleen cells of normal, non-immunized mice and from mice 3 days after immunization with human immunoglobulin G was fractionated at increasing salt concentrations into three fractions: 0.35 M NaCl-soluble, 2 M NaCl-soluble and a residual fraction, dissociated in 2 M NaCl/5 M urea. The residual fraction of chromatin, homogeneous by ultracentrifugation and containing only 25% of the total chromatin DNA, was associated with proteins strongly labeled with [3H]tryptophan, [3H]methionine and [3H]leucine. This fraction was more sensitive to DNAase II treatment than was native, non-fractionated chromatin and it contained approx. 40% Mg2+-soluble DNA sequences. The template activity of the residual fraction was 6--7-times higher than that of non-fractionated chromatin. Fraction A, characteristic for non-immunized spleen cells, was present in three chromatin fractions and after DNAase II treatment it remained only in the residual fraction, which suggests that this fraction is associated with genes non-transcribed in non-immunized mice. Fractions I and B1 were found mainly in the residual fraction, and only in smaller amounts in the 0.35 M NaCl-soluble fraction. After DNAase II treatment, fractions I and B1 in chromatin from immunized mice disappeared, which suggests that these fractions may be associated with active transcribed sequences during the immune reaction.

Animals↗
PubMed1980

Synthesis of non-histone chromatin proteins of mice in spleen cells and myeloma cells RPC 5 and ABPC 22.

Non-histone chromatin proteins of myeloma cells RPC 5, synthesizing gamma 2A and ABPC 22 synthesizing IgM as well as non-histone chromatin proteins of spleen cells from mice bearing these tumours and from control mice were labelled during culture in vitro with 3H-tryptophan, 3H-leucine or 3H-methionine. Electrophoretic patterns of labelled chromatin proteins indicated, that in myeloma cells, producing spontaneously immunoglobulins, any characteristic fraction of non-histone chromatin proteins, described previously in immunoglobulin producing spleen cells, could not be detected, although the profiles of these proteins in myeloma cells, spleen cells from mice bearing these tumours and control spleen cells varied.

Animals↗
PubMed1978

Non-histone chromatin proteins of mouse spleen cells during the primary immune response to sheep red blood cells and aggregated human gamma-globulin.

1. The protein/DNA ratio in chromatin of spleen cells increased during immunization; the ratio was the highest at the time of the maximum antibody synthesis, then decreased to the control values. 2. In the spleen cells of mice immunized with sheep red blood cells or aggregated human gamma-globulin, several characteristic fractions of non-histone chromatin proteins were preferentially synthesized: two antigen-specific fractions were observed in the phase of IgM and IgG synthesis, respectively, and the third, unspecific fraction was detected when the antibody synthesis ceased.

Animals↗