Biomedical subjects

K U Scholz

Publications and source records attributed to K U Scholz.

6 recordsLinked to original sources

PubMed1988

Regulation of lymphocyte homing. I. Alterations in homing receptor expression and organ-specific high endothelial venule binding of lymphocytes upon activation.

Upon activation, lymphocytes display profound alterations in their in vivo migration behavior. In an attempt to understand some of the cellular mechanisms responsible for this altered behavior, in vitro stimulated lymphocytes have been analyzed for their expression of a putative homing receptor (HOR) (defined by mAb MEL-14) and for their ability to bind to specialized lymphoid organ high endothelial venules (HEV) in vitro. The results indicate that signals related to lymphocyte activation induce complex alterations in HOR expression and organ-specificity of HEV-binding: 1) submitogenic stimuli induce an increase in MEL-14 antigen expression. This applies to almost all lymphocytes in autologous cultures, for the fraction of cells in periodate, LPS- or Con A-treated cultures not fully activated and for cultures stimulated with suboptimal doses of Con A. 2) Full blast transformation is associated with a decrease or complete loss of MEL-14 antigen expression on the majority of blasts in all activating systems used, but a subset of up to 30 to 40% of fully activated cells may nonetheless express very high levels of the MEL-14 antigen. 3) Functional assays reveal that Con A and periodate stimulation lead to a selective, nearly complete suppression of the lymphocytes binding to HEV of Peyer's patches, even under conditions where overall binding to peripheral node HEV is increased. This indicates a differential regulation of the two respective receptors, with the mucosa system-specific HOR being more prone to down-regulation during in vitro activation by these mitogens.

Animals↗

PubMed1983

The intrathymic microenvironment: expression of lectin receptors and lectin-like molecules of differentiation antigens and MHC gene products.

The expression of MHC products, differentiation antigens and lectin receptors has been investigated in the various cell types populating different compartments of the thymus. The ultrastructural classification of suspended thymic epithelial cells was facilitated by using a technique that preserves cortical nursing cells or medullary epithelial cell clusters. A subset of peanut lectin positive lymphocytes could be distinguished by their ability to bind soybean lectin also. This subset corresponds to the large proliferating lymphocytes that populate the area between the thymic capsule and the cortex. Ia and H-2 D/K antigens could be detected on nearly all epithelial and lymphoid cells. Expression of H-2 antigens, however, is more pronounced on medullary epithelial cells. T-cell differentiation antigens such as Thy-1 and Lyt-1 could be demonstrated not only on lymphocytes, but, interestingly enough, on cortical epithelial cells as well. These latter cells, in addition, exhibit a cell membrane-bound lectin with a specificity for D-galactose which might well be the structure responsible for binding the galactosyl residues of the peanut lectin receptor of thymic lymphocytes. Binding sites for a large set of lectins could be demonstrated on both, thymic lymphocytes and epithelium. The intrathymic differentiation pathway of T-lineage cells is discussed with regard to those lymphocytic and epithelial cell surface structures considered to enable cellular interaction.

Animals↗

PubMed1981

Mathematical evaluation of two parameter flow cytometric histograms.

A general procedure was developed to evaluate two-parameter flow cytometric data. These data usually show overlapping distributions representing different subpopulations. To calculate the fractions of cells in the various subpopulations, the maximum likelihood method is used, assuming an unknown number of Gaussian distributions with constant coefficient of variation in the histogram. A test on simulated data shows that Gaussians can be separated clearly by the procedure if the distance between their mean values is larger than twice the maximum standard deviation. The analysis of different measurements of double-stained (DNA/protein) cultured cells out of the same pool yield the same fractions in the phases of the cell cycle with acceptable error rates. To simulate samples with different fractions in the phases of the cell cycle, defined mixtures of proliferating and resting cells of the same type were prepared and measured for DNA and cell size. The calculated fractions are consistent with the expected variation of G1, S and G2 + M fractions depending on the mixture ratio.

Animals↗

PubMed1981

Data analysis of two-parameter flow cytometric measurements.

A new procedure was developed to evaluate two-parameter flow cytometric data. These data usually show overlapping distributions of different subpopulations. To calculate the fractions of cells in the various subpopulations, the maximum likelihood method was used, which assumes a superimposition of Gaussian distributions in the histogram. The resolution quality was tested for both one-parameter and two-parameter data using simulated histograms with two superimposed subpopulations. Comparison of this procedure to existing one-parameter evaluations methods, using the same original histograms, yielded satisfactory results. For the case of one parameter as well as for two parameters, the subpopulations were well separated if the distance between the mean values exceeded 2 sigma ; the total count and the proportions of the subpopulations were of minor influence. The evaluation procedure also worked well when applied to simulated two-parameter histograms, similar to DNA protein measurements of cultured cells.

Cell Cycle↗

PubMed1981

Prescreening of cervical smears using two-parameter flow cytometry. Cytologic identification of artifacts.

Individual properties of gynecologic specimens can produce artifacts in flow cytometric (FMC) measurements, possibly leading to false interpretations. An identification of such artifacts was undertaken by parallel FCM and microscopic investigations. One hundred fifty unselected cervical smears were measured by FCM using the fluorochromes 4'-6-diamidino-2-phenylindole (DAPI) for DNA and sulforhodamine (SR 101) for protein. Microscopic specimens were stained by the Papanicolaou technique, and a detailed cytogram was prepared from each smear. FCM discrimination of fluorochrome-stained superficial and intermediate cells was very difficult. On the other hand, a correlation could be established between the fraction of cells from the deeper epithelial layers in the microscopic cytogram and the mean protein content in the FCM histogram. Furthermore, the role of microorganism could be elucidated. Some microorganisms may produce a reduction of the protein content by cytolytic changes. Other microorganisms adhere to the cell surface, resulting in a misleading increase of the DNA fluorescence. Implications for the problem of false alarms are discussed.

Bacteria↗

PubMed1979

Flow cytometric prescreening of cervical smears.

One-parameter (nuclear DNA) and two-parameter (nuclear DNA and protein or cellular light scatter) measurements of cervical smears were performed using an ICP 11 and a cytofluorograf 4800 respectively. A total of about 1000 cases was analyzed. For the estimation of nuclear DNA alone two fluorochromes were tested (ethidium bromide (EB) and mithramycin (MMC)) combined with three different methods of cell preparation. For the two-parameter measurements cells were double stained with EB and fluorescein isothiocyanate (FITC). Red fluorescence (EB) versus green fluorescence (FITC) or red fluorescence versus scatter were recorded. A computer analysis of the one-parameter histograms was performed using discriminant analysis and the results were compared with the cytodiagnosis of microscopic specimens stained with the Papanicolaou technique. The error rates of the flow cytometric (FCM) data were as follows: (a) standard EB staining, 11% false negative, 26% false positive, 6% unsatisfactory results; (b) pepsination of vital cells and EB staining, 12% false negative, 14% false positive and 4% unsatisfactory results; (c) MMC staining, 10% false negative, 65% false positive and 5% unsatisfactory results. Our two-parameter measurements prove that, as confirmed by cell sorting, red fluorescence versus scatter allows separation of at least three subpopulations in most analyzed samples: (a) anucleated cells; (b) leukocytes; and (c) intermediate and superficial cells.

Cell Nucleus↗