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Biomedical subjects

R Arndt

Publications and source records attributed to R Arndt.

At least 127 records · Page 7Linked to original sources
PubMed1978

Evidence for the presence of Thy-1 on cultured thymic epithelial cells of mice and rats.

Thymic tissue of C57BL/6 mice and DA rats was cultured. After 6--8 weeks, cultures were analyzed for their capacity to absorb anti-Thy-1 serum, and for the expression of Thy-1 on the surface of different cell types by means of the indirect peroxidase labeling method. Three main cell types were identified: epithelium-like cells, fibrocyte-like cells and macrophages, but no lymphocytes were found. The presence of Thy-1 on cultured nonlymphocytic thymus-derived cells was demonstrated by their ability to absorb the cytotoxic activity of the appropriate anti-Thy-1 sera. Electron microscopical analyses of labeling experiments revealed that Thy-1 was predominantly expressed on epithelium-like cells with preference for their cell protrusions. The possible role of Thy-1 expression, both on thymocytes and thymus epithelium for cellular interaction, is discussed.

Animals↗
PubMed1978

Investigations on the functional role of rat liver carboxylesterase isoenzymes.

We have compared the substrate specificities of two isoenzymes of rat liver esterase. Isoenzyme E1 which we isolated earlier, and isoenzyme EA, the isolation of which is reported here, have very similar molecular weights, subunit weights, and isoelectric points. In contrast, the two enzymes have distinctly different substrate optima when tested with a series of esterase substrates. Our finding poses the question, as to whether the rather unspecific in vivo behaviour of liver carboxylesterase could be explained by an ensemble of isoenzymes with overlapping substrate specificitites and mutually complementary substrate optima. The biological function of esterase isoenzymes appears to represent an extension of the range of hydrolytic competence of a single enzyme.

Animals↗
PubMed1978

Partial molecular characterization of an antigenic structure associated to cells of common acute lymphocytic leukaemia (ALL).

A heteroantiserum against common human acute lymphocytic leukaemia (ALL) cells was raised in rabbits. This antiserum was rendered specific for common ALL cells by extensive absorption with different human tissue. A specific antigen associated to common ALL cells was solubilized by sodium deoxycholate from ALL plasma membranes and identified by indirect immunofluorescence. By analytical chromatography, two antigenically active peaks were found. The apparent molecular weights were calculated to be 55,000 and 110,000.

Antigens, Neoplasm↗
PubMed1978

Serological and chromatographic analyses of antigenic structures detected in human brain, thymus and lymph nodes.

In the present paper it is shown that the non-species specific determinant of the antigenic thymus-brain system previously detected in murine and human brain also exists in human thymus. However, in contrast to the situation in mice and rats this antigenic structure is not expressed on suspended thymic lymphocytes, but is associated with thymic tissue largely depleted of thymic lymphocytes. Moreover, this determinant is also detectable in human lymph nodes. Besides the non-species-specific antigenic determinant human thymus and brain also share a species-specific determinant. In contrast to the non species specific determinant this structure is also displayed by suspended thymic lymphocytes, certain peripheral blood lymphocytes and bone marrow cells. The non-species-specific determinant detected in human thymus is borne by a structure, which physico-chemically resembles the thymus-brain antigen isolated from murine brain and thymus as well as from human brain. Although the structure bearing the species specific antigenic determinant has a similar apparent molecular weight both antigens could be separated by ion exchange chromotography indicating their molecular diversity.

Animals↗
PubMed1977

Analysis of the antigenic structure of the thymocyte surface membrane by heterologous anti-thymocyte serum.

The surface membrane of rat thymocytes and lymph node cells was analyzed by comparing the capability of different rat cell types and of solubilized and chromatographically separated rat thymocyte membrane fractions to absorb cytotoxic antibodies on rat thymocytes and lymph node cells from a heterologous anti-rat thymocyte serum. The experiments described cause distinct antigenic specificities of the thymocyte membrane to be brought into relationship to structures of defined physio-chemical properties, and thus are an approach of a thymocyte cell surface mapping in antigenic as well as in molecular terms. Futhermore, the data presented allow conclusions on the distribution pattern of single antigenic determinants on different cells or tissues used as absorbents and target cells.

Animals↗
PubMed1977

Evidence for the presence of choleragen receptor on the thymocyte-brain antigen molecule of mice.

CBA thymocytes were subjected to cocapping experiments using AThy-1.2 and choleragen. The finding that both structures showed a common ligant-induced redistribution implies that choleragen receptors of the cell membrane are associated with the thymocyte-brain molecule. Furthermore, it was found that the thymocyte-brain antigenic determinants on the thymocyte were not blocked by prior choleragen treatment. This suggests a spatial distance between these structures on the molecule.

Animals↗
PubMed1977

Detection and molecular characterization of the thymus-brain antigen in human brain.

Anti-human brain sera were found to contain antibodies reacting with determinants present on murine thymocyte plasma membranes. This determinant is borne by the thymocyte-brain antigen of mouse thymocytes. The non species-specific determinant of the thymocyte-brain system is detectable on the thymocyte-brain antigen of human and mouse brain in comparable amounts. In contrast to these findings, the allogenic Thy-1 and the species-specific determinant of this system were only found on the thymocyte-brain antigen of mouse brain but not on the corresponding antigen of human brain. The molecular weight, Stokes radius and diffusion coefficient of the thymocyte-brain antigen of human and mouse brain are in good accordance with the data estimated for the corresponding antigen of murine thymocytes.

Animals↗
PubMed1976

Solubilization and molecular characterization of membrane-bound antigens shared by thymocytes and brain.

In order to characterize chemically the serologically well-defined antigens shared by thymocytes and nervous tissue of mice and rats, different solubilization procedures have been tested. Treatment of thymocyte membranes with urea-Nonidet-P40 (NP40) proved to be the most valuable method, since nearly 100% of the antigen was solubilized essentially without loss of the antigenicity. By gel filtration in urea-NP40 the molecular weight was estimated to be 35 000 and the Stokes radius in sodium deoxycholate 31.8 A. In gel filtration studies a homogenous peak was obtained, whereas isoelectric focusing yielded two peaks (isoelectric points pH 4.5-5.0 and pH 5.4). The three determinants of this antigenic system were inseparable in gel filtration and isoelectric focusing, supporting the view put forward on the basis of serological studies that they are part of the same molecule. Extraction of murine thymocyte membranes with organic solvents yielded a considerable loss of activity of the thymocyte-brain antigen. There was some residual activity in the protein fraction, but none in the organic phase. Correspondingly, the highly purified ganglioside G Gtet 2b proved unable to absorb any rabbit anti-CBA brain serum. The reduced antigenic activity of the delipidated protein fraction could be restored by addition of lipids, as well as the nonionic detergent NP40. These observations suggest that interaction of protein and lipid is necessary for the antigenicity of the thymocyte-brain antigen.

Animals↗