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Biomedical subjects

J Wessels

Publications and source records attributed to J Wessels.

46 records · Page 3Linked to original sources
PubMed1983

Cell size monitored counterflow centrifugation of human bone marrow resulting in clonogenic cell fractions substantially depleted of small lymphocytes.

Human bone marrow cells were fractionated by physical methods in order to obtain cell fractions enriched in clonogenic cells and devoid of immunocompetent lymphocytes. The bulk of the erythrocytes was removed by isopycnic gradient centrifugation on Ficoll-Isopaque (d = 1.085 g/ml) and the majority of mature granulocytes on Percoll (d = 1.070 g/ml). The nucleated cells were separated into fractions by counterflow centrifugation. Continuous monitoring of the effluent of the elutriator by a light scatter device improved the reproducibility of the separation profiles. Progenitor cells did not form a single distinct peak and the maximal enrichment factor was 8.5. Lymphocytes were eliminated almost completely from the progenitor cell rich fraction (both CFU-GM and BFU-E). Physical elimination of lymphocytes from human bone marrow may offer an alternative approach to the prevention of graft-versus-host disease in allogeneic bone marrow transplantation.

Antigens, Surface↗
PubMed1983

Continuous measurement and analysis of staining kinetics by flow cytometry.

The measurement of color development with time in cells following the start of a staining reaction is of interest in a number of biological systems. These include the subsets of peripheral white blood cells after acridine orange staining, the uptake by cells and nuclei of fluorescent agents, especially antitumor drugs, and measurement of intracellular enzyme kinetics using fluorogenic or absorbing substrates. The present work describes a simple computer program for analyzing flow cytometric (FCM) data versus time, including both the population kinetics of color development and the variability of staining speed within one population of cells. A single-channel absorption measurement in flow (Technicon Hemalog D) was used to record peroxidase kinetics in peripheral blood cells. Every 5 s, a 64-channel absorption histogram was recorded, up to a maximum of 64 histograms. The data were then analyzed by a computer program which searched for the peak channel of each histogram. A least-squares fit was computed for these maxima. The asymmetries of the 64 absorption histograms were compared to see if there was more than one population present with different time constants. Although developed for enzyme kinetic measurements, this program may have wider usefulness in any measurements of time-dependent phenomena by FCM.

Computers↗
PubMed1980

Improved method of enrichment for immature myeloid cells from normal human bone marrow.

A method of enrichment for immature myeloid cells from normal human bone marrow has been described. The method is based on 4 consecutive steps: 1. Density cut centrifugation. After centrifugation all cells above the pellet were collected. This suspension contained 93% of the originally present myeloblasts and promyelocytes. The majority of normoblasts and granulocytes was found in the pellet. 2. Nylon wool filtration. This procedure was performed to remove the majority (87%) of the monocytes. Recovery of myeloblasts and promyelocytes after filtration was 74%. 3. Centrifugation on a continuous density gradient. This procedure resulted in an additional purification of the myeloblasts and promyelocytes within a specific fraction. By centrifugation the concentration of myeloblasts and promyelocytes was increased from 19% to 38%. 4. Velocity sedimentation at 1 g. This technique produced a 82% pure immature myeloid cell suspension, comprising 57% myeloblasts and promyelocytes. All figures are the mean of 10 experiments.

Bone Marrow Cells↗
PubMed1977

Cytosine arabinoside binding to human plasma proteins.

The interaction of cytosine arabinoside (Ara-C) with human plasma proteins was investigated by means of ultrafiltration and ultracentrifugation. The results obtained with both methods did not differ significantly. Ara-C binding was studied at plasma levels within the therapeutic range (0.005-1.0 mg/l). It appeared that 13.3% (SD: 2.2%) of Ara-C in the plasma was bound to proteins. The percentage of bound drug was independent of the drug concentration, at least in the therapeutic range.

Blood Proteins↗
PubMed1975

Bone-marrow-profileration patterns in acute myeloblastic leukaemia determined by pulse cytophotometry.

The proliferation patterns of normal and leukaemic bone-marrow were studied by measuring the D.N.A. content of large numbers of cells by pulse cytophotometry (P.C.P.). In nineteen normal bone-marrow samples an average of 66-3% of the bone-marrow cells were in the G1 phase (2n D.N.A.), 26-1% in the S phase (2n smaller than D.N.A. smaller than 4n), and 7-5% in G2+M phase (4n D.N.A.). The percentages of S-phase cells determined by autoradiography and P.C.P. correlated well, both in normal and in leukaemic bone-marrow. In 25 patients with untreated acute myeloblastic leukaemia (A.M.L.) lower percentages of cells were found in S and G2+M phases, indicating a smaller proliferating pool compared with normal bone-marrow. The likelihood of a complete remission being attained in A.M.L. with the first treatment course was correlated with the percentage of S-phase cells present before treatment. At remission in A.M.L. the proliferation pattern was restored to normal.

Autoradiography↗
PubMedDate not supplied

From combinatorial libraries to MHC ligand motifs, T-cell superagonists and antagonists.

Complete experimental data sets of HLA-ligand motifs and T-cell recognition patterns can be derived from combinatorial peptide libraries. These data provide the exact molecular basis for a fast development of synthetic vaccines, T-cell superagonists and non-peptide antagonists. Patient-specific peptides, peptidomimetics and vaccines of highest reactivity can be derived directly from the data sets via our prediction programme EPIPREDICT. The resulting lead structures may be developed into valuable diagnostics and therapeutic tools for the treatment of viral infections, autoimmune diseases and tumors. As one example, antibody and T cell recognition in the intestinal auto-immune disease, coeliac disease was investigated in more detail concerning the deamidation of gamma-gliadin peptides by tissue transglutaminase 9tTG) leading to autoreactive peptides specific for HLA-DQA1*0501, DQB1*0201.

Amino Acid Sequence↗
PubMedDate not supplied

Cell cycle related uptake, retention and toxicity of idarubicin, daunorubicin and doxorubicin.

Exponentially growing Molt-4 cells were separated by means of counterflow centrifugation into fractions enriched for cells in early G1, late G1, S, or G2+M phase of the cell cycle. Subsequently, cells were exposed for 2 h to Idarubicin (Ida, 0.02-0.15 microgram/ml). Daunorubicin (Dnr, 0.1-0.75 microgram/ml) or Doxorubicin (Dox, 0.1-0.75 microgram/ml). Drug uptake, measured by flow cytometry, increased progressively with cell cycle traverse from early G1-to M-phase. The relative fraction of drug lost following an extensive wash procedure was 72% in case of Ida and 23% for Dnr and Dox and was independent of the cell cycle phase. Inhibition of DNA synthesis was determined by qualitative flow cytometric analysis of 5-iodo-2'-deoxyuridine (IdUrd) incorporation into DNA. The three drugs showed a similar gradual increase of inhibition of DNA synthesis from G1 to G2+M phase, demonstrating that cell cycle phase dependency of drug toxicity applies to all three anthracyclines studied.

Biological Transport↗